Screening Assessment Petroleum Sector Stream Approach Asphalt and Oxidized Asphalt Chemical Abstracts Service Registry Numbers 8052-42-4, 64742-93-4 (2024)

Environment and Climate Change Canada
Health Canada

August 2017

(PDF Format - 691 KB)

• Synopsis
• 1. Introduction
• 2. Identity of substances
• 3. Physical and chemical properties
• 4. Sources
• 5. Uses
• 6. Releases to the environment
• 7. Environmental fate and behaviour
  • 7.1 Environmental distribution
  • 7.2 Persistence and bioaccumulation
• 8. Potential to cause ecological harm
  • 8.1 Ecological effects assessment
  • 8.2 Ecological exposure assessment
  • 8.3 Characterization of ecological risk
• 9. Potential to cause harm to human health
  • 9.1 Exposure assessment
  • 9.2 Health effects assessment
  • 9.3 Characterization of risk to human health
  • 9.4 Uncertainties in evaluation of cumulative risk to human health
• 10. Conclusion
• References
• Appendices
  • Appendix A. Petroleum substance grouping
  • Appendix B. Physical and chemical properties of representative substances for asphalts (experimental and modelled values, EPI Suite c2000-2010)a
  • Appendix C. Sources and releases of asphalts in Canada
  • Appendix D. Persistence of specific groups of petroleum hydrocarbons potentially found in asphalts
  • Appendix E. Ecotoxicological information
  • Appendix F. Exposure from industrial release from asphalt processing, handling and storage for asphalt refineries and dust ingestion
  • Appendix G. Summary of health effects information for asphalts (CAS RNs 8052-42-4 and 64742-93-4)
  • Appendix H. Potency equivalence factors for 16 PAH species

• Table 2-1. Summary of major chemical classes found in asphalts (API 2009)
• Table 3-1. Estimated physical and chemical properties for asphalt (CAS 8052-42-4)
• Table 3-2. Estimated physical and chemical properties for oxidized asphalt (CAS 64742-93-4)
• Table 5-1. Types of asphalt produced (CONCAWE 1992)
• Table 5-4. Description of asphalt formulations used in paving applications (US NTP 1997; WHO 2004)
• Table 8-1. Lines of evidence for risk characterization
• Table 9-1. Median concentrations in dust (μg/g) from 23 ground-floor apartments in Austin, Texas (adapted from Mahler 2010)
• Table 9-2. MOEs for long term benzene exposure in the vicinity of asphalts facilities
• Table 9-3. Air concentrations of PAH species in the vicinity of an asphalt plant at 230 m from release source
• Table 9-4. Soil and dust and B[a]P-equivalent intakes by age group
• Table A-1. Description of the nine groups of petroleum substances
• Table A-2. Substance identity of asphalts
• Table A-3. Definitions for asphalts and related terms
• Table C-1. Canadian supply and demand characteristics in million liters, 2012 (Statistics Canada 2013)
• Table C-2. Reported release volumes and spill numbers of asphalts spilled in Ontario from 2008 to 2012 (OMOE 2013)a
• Table C-3. Number of spills of asphalt materials affecting air, land, and freshwater in Ontario from 2008 to 2012 (OMOE 2013)
• Table C-4. Reported causes of spills of asphalt materials in Ontario from 2008 to 2012 (OMOE 2013)
• Table D-1. Persistence of petroleum hydrocarbon groups (based on Environment Canada (2014)
• Table E-1. Modelled acute aquatic toxicity data for asphalts (PETROTOX 2012)a
• Table E-2. Aquatic toxicity of aromatic extracts (C20-C50) (US EPA 2011)
• Table E-3. PAH concentrations in various leaching tests with a comparison to CCME water quality guidelines
• Table F-1. Variable inputs to SCREEN3 for Hot Mix Asphalt Plants benzene dispersion
• Table F-2. Concentrations of benzene at hot mix asphalt plants form dispersion modelling
• Table F-3. Variable inputs to SCREEN3 for hot mix asphalt plant total PAHs and individual PAH dispersion
• Table F-4a. Dispersion modelling (in μg/m3) results for PAHs (total and individual species) in the vicinity of drum mix asphalt plants
• Table F-4b. Dispersion modelling (in μg/m3) results for PAHs (total and individual species) in the vicinity of drum mix asphalt plants
• Table F-4c. Dispersion modelling (in μg/m3) results for PAHs (total and individual species) in the vicinity of drum mix asphalt plants
• Table F-5a. PAH concentrations (μg/g) and benzo[a]pyrene equivalents in house dust (includes unsealed asphalt and asphalt-based sealcoated asphalt pavement types)
• Table F-5b. PAH concentrations (μg/g) and benzo[a]pyrene equivalents in house dust (includes unsealed asphalt and asphalt -based sealcoated asphalt pavement types)
• Table F-5c. PAH concentrations (μg/g) and benzo[a]pyrene equivalents in house dust (includes unsealed asphalt and asphalt-based sealcoated asphalt pavement types)
• Table F-6. Age-dependent adjustment factors (ADAF) and determination of dust ingestion MOE
• Table F-7. Age-dependent adjustment factors (ADAF) and determination of dust ingestion MOE
• Table H-1. Potency equivalence factors for 16 PAH species

Asphalt (CAS RN 8052-42-4) and oxidized asphalt (CAS RN 64742-93-4) were identified as priorities for assessment as they met the categorization criteria under subsection 73(1) of CEPA. These substances were included in the Petroleum Sector Stream Approach (PSSA) because they are related to the petroleum sector and are considered to be of Unknown or Variable composition, Complex reaction products or Biological materials (UVCBs).

Asphalt and oxidized asphalt are complex combinations of high molecular weight organic compounds containing a relatively high proportion of hydrocarbons; carbon (C) numbers are predominantly greater than C₂₅ with high carbon-to-hydrogen ratios. They are residual substances derived from the high temperature vacuum distillation of petroleum. The composition and physical-chemical properties of asphalt and oxidized asphalt vary depending on the source(s) of crude oil, processing steps and blending stocks involved in their production.

Asphalt and oxidized asphalt are used primarily (approximately 99%) in the construction of roads and in roofing materials, but they may be found in adhesives and sealants, paints and coatings, and other miscellaneous products available to consumers. Other residual substances in the asphalt group with different CAS RNs might also be added into asphalt formulations if they meet the material specifications. As data on asphalt formulations (final formulated products) generally do not specify a CAS RN, and all residuals are expected to behave similarly when used in these products, the results of the analyses herein on these asphalt formulations for the purpose of assessing asphalt and oxidized asphalt may also apply to other substances in the asphalt group. For the purpose of this assessment the term "asphalts" is used to refer to different grades and types of asphalt (CAS RNs 8052-42-4) and oxidized asphalts (CAS RN 64742-93-4).

Release of hazardous components of asphalts to the environment is considered to be low based on experimental studies on polycyclic aromatic hydrocarbons (PAHs) leaching from paving and roofing asphalt formulations. In addition, asphalts can stabilize and entrap contaminants or other petroleum substances mixed with asphalts, making them unavailable to organisms or the environment.

Based on physical-chemical properties such as high K_OW, high K_OC, very low vapour pressure and very low water solubility under environment-relevant conditions, asphalt components are not expected to disperse in the environment or to be bioavailable. Modelled ecotoxicity data, and results from ecological toxicity studies on bean and corn seeds exposed to oxidized asphalt indicate low toxicity. Use of hot-mix asphalt as lining for fish ponds, and low aquatic toxicity of runoff from unsealed asphalt pavement also indicate that the bioavailability and ecotoxicity of asphalts is very low. Although spills of asphalt materials are reported, asphalts are not likely to disperse in the environment because of their low mobility. The lack of bioavailability and low toxicity of asphalts also indicate that the ecological concern of spilled asphalt materials is considered to be low.

Considering all available lines of evidence presented in this screening assessment, there is a low risk of harm to organisms or the broader integrity of the environment from these substances. It is concluded that asphalt and oxidized asphalt (CAS RNs 8052-42-4 and 64742-93-4) do not meet the criteria under paragraphs 64(a) or (b) of CEPA as they are not entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity or that constitute or may constitute a danger to the environment on which life depends.

A critical health effect for the initial categorization of asphalt and oxidized asphalt was carcinogenicity, based on classifications by international agencies. PAHs and benzene, minor components of asphalts, have been identified by Health Canada and several international regulatory agencies as carcinogens. PAHs (as represented by benzo[a]pyrene equivalents) and benzene were therefore selected as high-hazard components of asphalts for use in characterizing long-term exposure and risk to the general population in the vicinity of asphalt production and storage facilities. Naphthalene, a volatile PAH, was selected to characterize shorter term exposures to bystanders.

The potential for exposure of the general population to asphalts includes consideration of inhalation exposure in the vicinity of either asphalt-producing and refining industries or near paving operations. Dermal exposure can occur from use of consumer products, including as a result of application of asphalt-based pavement sealant in residential settings. Long-term oral exposure to components of asphalts (i.e., PAHs) can occur as components of asphalts may migrate from asphalt surfaces indoors and are found in house dust. Risks to human health were characterized for these potential exposures.

For short-term inhalation exposure in the vicinity of paving operations, a margin of exposure based on an a conservativeexposure of a bystander to naphthalene, and the effect level in exposed animals causing a local effect on nasal olfactory epithelium, was considered adequate. Short-term dermal exposure to asphalts from asphalt-containing products is not considered to constitute a risk to human health due to a lack of toxicity exhibited by asphalt in short-term animal studies, and due to low dermal absorption of asphalts.

For potential inhalation exposures to asphalts from fugitive and point releases from the production and refinement of asphalt in the vicinity of facilities, margins of exposure between conservative estimates of exposures to benzene and to PAHs, and estimates of cancer potency previously developed for inhalation exposure to benzene and to PAHs, are considered adequate to address uncertainties in health effects and exposure databases.

For potential long-term oral exposure to components of asphalts that may migrate indoors over time from asphalt driveway sealcoat (where exposure is through ingestion of house dust that contains asphalt-derived PAHs), margins of exposure between oral exposure to PAHs and a conservative point of departure for benzo[a]pyrene are considered adequate to address uncertainties in health effects and exposure databases.

Therefore, general population exposure to asphalt and oxidized asphalt is not considered to constitute a risk to human health.

Based on the information presented in this screening assessment, it is concluded that asphalt and oxidized asphalt (CAS RNs 8052-42-4 and 64742-93-4) do not meet the criteria under paragraph 64(c) of CEPA as they are not entering the environment in a quantity or concentration or under conditions that constitute or may constitute a danger in Canada to human life or health.

It is concluded that asphalt and oxidized asphalt (CAS RNs 8052-42-4 and 64742-93-4) do not meet any of the criteria set out in section 64 of CEPA.

Pursuant to section74 of the Canadian Environmental Protection Act, 1999 (CEPA) (Canada 1999), the Minister of the Environment and the Minister of Health conduct screening assessments of substances to determine whether these substances present or may present a risk to the environment or to human health.

A key element of the Government of Canada's Chemicals Management Plan (CMP) is the Petroleum Sector Stream Approach (PSSA), which involves the assessment of approximately 160 petroleum substances that are considered priorities for action. These substances are primarily related to the petroleum sector and are considered to be of Unknown or Variable composition, Complex reaction products or Biological materials (UVCBs).

These petroleum substances fall into nine groups of substances based on similarities in production, toxicity and physical-chemical properties (see Table A-1 in Appendix A). In order to conduct the screening assessments, each petroleum substance was placed into one of five categories ("streams") depending on its production and uses in Canada:

Stream 0: substances not produced by the petroleum sector and/or not in commerce;
Stream 1: site-restricted substances, which are substances that are not expected to be transported off refinery, upgrader or natural gas processing facility sites^Footnote1;
Stream 2: industry-restricted substances, which are substances that may leave a petroleum sector facility and may be transported to other industrial facilities (for example, for use as a feedstock, fuel or blending component), but that do not reach the public market in the form originally acquired;
Stream 3: substances that are primarily used by industries and consumers as fuels;
Stream 4: substances that may be present in products available to the consumer.

An analysis of the available data determined that 67 of these petroleum substances may be present in consumer products under Stream 4, as described above. These 67 substances were further sub-grouped as follows, based on their physical and chemical properties and potential uses: aromatic extracts, gas oils, heavy fuel oils (HFOs), low boiling point naphthas, natural gas condensates, solvents, petroleum and refinery gases (including liquefied petroleum gases), base oils, petrolatum and waxes, and asphalts.

This screening assessment addresses asphalt and oxidized asphalt described under Chemical Abstracts Service Registry Number (CAS RN) 8052-42-4 and CAS RN 64742-93-4, respectively. Asphalt and oxidized asphalt were identified as priorities for assessment as they met the categorization criteria under subsection 73(1) of CEPA (ECCC, HC 2007). Asphalt and oxidized asphalt were included in the PSSA because they are related to the petroleum sector and are complex combinations of hydrocarbons.

Included in this screening assessment is the consideration of information on chemical properties, health effects, uses, and exposure, including information submitted under section 71 of CEPA. Data relevant to the screening assessment of these substances were identified in original literature, review and assessment documents, and in stakeholder research reports, submissions and correspondence, as well as from recent literature searches, up to June 2015. Key studies, which were critically evaluated, and modelling results were used to inform conclusions.

This screening assessment was prepared by staff in the CEPA Risk Assessment Programs at Health Canada and Environment and Climate Change Canada and incorporates input from other programs within these departments. The ecological and human health portions of this assessment have undergone external review and/or consultation. Comments on the technical portions relevant to the environment were received from Dr. Lawrence Kapustka, Dr. Gladys Stephenson and Mr. Geoff Granville, while those relevant to human health were received from Dr. Simon Hesp (Queen's University, Kingston, ON) and Dr. E. Spencer Williams (Baylor University, Waco, TX). Additionally, the draft of this Screening Assessment was subject to a 60-day public comment period. While external comments were taken into consideration, the final content and outcome of the screening assessment remain the responsibility of Health Canada and Environment and Climate Change Canada.

This screening assessment focuses on information critical to determining whether a substance meets the criteria as set out in section 64 of CEPA, by examining scientific information and incorporating a weight-of-evidence approach and precaution^Footnote2. The screening assessment presents the critical information and considerations on which the conclusion is based.

For the purposes of this document, the term "asphalt" refers to the substance with CAS RN 8052-42-4; the term "oxidized asphalt" refers to the substance with CAS RN 64742-93-4; the term "asphalts" refers to both. Various terms related to asphalt are used in this assessment, and their definitions are provided in Table A-3 in Appendix A for clarity. The asphalt considered in this screening assessment is a refined petroleum product imported into Canada or produced in Canadian refineries and upgraders, though natural asphalt deposits occur in various parts of the world due to mineral oil seepage from the ground (WHO 2004). Oxidized asphalt is also known as air-blown or air-refined asphalt, which is produced from asphalt during air-blown processes at elevated temperatures (WHO 2004). This process is principally one of oxidative condensation, which increases the molecular weight, melting point and asphaltene content (Kleinschmidt and Snoke 1958; CONCAWE 1992).

Asphalts are UVCBs rather than discrete chemicals and, as such, they have no specific chemical formula or structure. These UVCB substances are complex combinations of molecules that can originate in nature or are the result of chemical reactions and processes that take place during the distillation process. Given their complex and variable compositions, they could not practicably be formed by simply combining individual constituents.

Asphalts are complex combinations of high molecular weight organic compounds containing a relatively high proportion of hydrocarbons; carbon (C) numbers are predominantly greater than C₂₅ with high carbon-to-hydrogen ratios (API 2009). Elemental analyses indicate that most asphalts contain approximately 79%-88% by weight (wt%) carbon, 7 wt%-13 wt% hydrogen, 2 wt%-8 wt% oxygen, trace to 8 wt% sulphur and trace to 3 wt% nitrogen (US EPA 2011).

Asphalts are among seven residual streams covered within the asphalt group as defined in the US Environmental Protection Agency High Production Volume (HPV) Challenge Program (API 2009). The asphalt group is typically made up of a group of heavy residual streams derived from the high temperature vacuum distillation of petroleum but may also be produced by thermal alteration during distillation, or from air blowing of residual streams (API 2009; Speight 2014). Substances in the asphalt group of the HPV program have high molecular weights (500-5000 g/mol) (API 2006, 2009).

Asphalt that has been refined to meet specifications for a particular use (e.g., paving, roofing, industrial or other uses) is termed asphalt cement (AI 1990b). Other synonyms for asphalt include asphaltic bitumen, asphaltum, petroleum asphalt, and, in Europe, bitumen (Speight 2014).

Asphalt is commercially available in a variety of types and grades. For example, there are different penetration grades of asphalt and hard asphalts (hard bitumens), which are described in detail in Section 5. The different grades of asphalt are still addressed by CAS RN 8052-42-4. Commercial asphalt has three main types: penetration grade, hard asphalts and oxidized asphalts; therefore, it includes both non-oxidized asphalt (CAS RN 8052-42-4) and oxidized asphalt (CAS RN 64742-93-4) (API 2006, 2009). For the purpose of this assessment, the term "asphalts" is used to refer to both asphalt and oxidized asphalt.

The four major chemical classes present in asphalt, oxidized asphalt and other substances of the asphalt group from petroleum refineries are described in Table 2-1. Proportions of these chemical classes can vary because of significant differences in the compositions of crude oil sources and the manufacturing process. No two asphalts are chemically identical and chemical analysis cannot be used to define the exact chemical structure or chemical composition of asphalt (IARC 1998; CONCAWE 1992; API 2006, 2009).

Polycyclic aromatic hydrocarbons (PAHs) are part of the aromatic fraction of asphalt and oxidized asphalt. They are organic compounds comprised of two or more fused aromatic rings in various arrangements, and contain only carbon and hydrogen molecules (Environment Canada, Health Canada 1994). The predominant PAHs present in asphalt and oxidized asphalt are of a high molecular weight. The presence of conventional PAHs (condensed three to seven ringed structures with no or few alkyl side chains) is limited in asphalt: 29 PAHs ranged from not detected to 28 mg/kg in one study (Kriech et al. 2002).

Commercial asphalt and oxidized asphalt can be treated further, processed or modified (e.g., by incorporating certain other substances) to produce asphalt formulations used as pavement and roofing materials, such as cutback asphalt, emulsified asphalt, foamed asphalt or polymer-modified asphalt. The term "asphalt materials" refers to Statistics-Canada-defined-asphalt, which is "produced by petroleum processing and includes asphalt flux, asphalt primers, asphaltic saturants, bitumals, cutback asphalts, liquid or solid asphalts, oxidized asphalt, paving compound and fluxes or primers" (Statistic Canada 2013); it is a general term that is inclusive of both asphalt group substances and asphalt formulations. Other residual stream substances in the asphalt group with different CAS RNs might also be used in asphalt formulations if they meet the material specifications. As data on asphalt formulations generally do not specify a CAS RN, and all residuals are expected to behave similarly when used in these products, the results of the analyses herein on such asphalt formulations for the purpose of assessing asphalt and oxidized asphalt may apply to all asphalt group substances that are used in such asphalt formulations. In addition, asphalt formulations can contain other petroleum substances (e.g., gas oils, kerosene, base oils, heavy fuel oils, distillate aromatic extracts, or naphtha). It is not possible to apportion releases of PAHs to individual substances when they are present in an asphalt formulation. Therefore, when characterizing environmental releases of PAHs from asphalt formulations, the contribution of components from any other petroleum substances present in the formulation is considered as part of the release scenario. Volatile organic compounds (VOCs) are also released during the application of asphalt formulations. The concern with VOCs is also from the cumulative loadings from numerous sources including asphalt formulations. VOCs are already listed on Schedule 1 of CEPA and actions are being taken to address releases of these compounds from different sources, including asphalt formulations. The environmental concerns of VOCs are not considered as part of this assessment.

Twenty-two representative structures were selected (Appendix B) on the basis of two fundamental characteristics: a boiling point greater than 350 °C and a carbon number inclusively between C₂₅ and C₅₀. Naphthalene (C₁₀) was included as a representative structure due to its presence in leachate of asphalt formulations, although it has a boiling point of 218 °C and would not be substantively present in untreated asphalt (i.e., asphalt not diluted or modified with other petroleum substances to reduce viscosity) (Kriech 1990, 1992a, 1992b). The presence of naphthalene in leachate is indicative of asphalt formulations containing other petroleum substances, or could simply be due to some carryover of naphthalene and its presence in leachate due to its high solubility. Asphaltenes and resin were not included within the representative structures because their complex structures are difficult to identify and their very high molecular weight (800-5000) makes them likely not bioavailable (Speight 2014; API 2009).

The physical and chemical behaviour of the individual representative structures will differ if these substances are present in a mixture. The vapour pressures of components in a mixture will be lower than their individual vapour pressures as explained by Raoult's law (i.e., the total vapour pressure of an ideal mixture is proportional to the sum of the vapour pressures of the mole fractions of each individual component). Similar to Raoult's law, the water solubilities of components in a mixture are lower than those for individual components alone (Banerjee 1984). Additionally, mixture components, which are normally solid under environmental conditions, might have lower melting points (and therefore be in a liquid state at lower temperatures), as well as increased vapour pressure and water solubility (Banerjee 1984). Nevertheless, the physical and chemical properties of the individual representative structures, as reported by Environment Canada (2014), indicate how the individual components of the mixture might behave in the environment.

Throughout this screening assessment, where information specific to asphalt was not available, information relating to its components was considered.

Asphalt (CAS RN 8052-42-4) is obtained as the non-volatile residue from crude oil distillation or as the raffinate following separation from a residual oil in a de-asphalting or de-carbonisation process (API 2009). In the refining process, starting with the residuum from atmospheric distillation, the maximum quantity of high value distillates are extracted from the residue until only the high boiling, high molecular weight components are left. Oxidized asphalt (CAS RN 64742-93-4) is obtained by treating asphalt by blowing air at elevated temperatures (CONCAWE 1992).

Multiple sources of production quantities of asphalt materials (import and export statistics of asphalt, and related materials, including asphalt flux, asphalt primers, asphaltic saturants, bitumals, cutback asphalts, liquid or solid asphalts, oxidized asphalt, paving compound and fluxes or primers) for provincial and territorial production in 2012 are presented in Table C-1 (Appendix C). According to Statistics Canada, 4.35 million tonnes of all types of asphalt materials were produced in 2012 and 1.40 million tonnes were exported. After accounting for other adjustments, such as transfers and inventory changes, 4.04 million tonnes of asphalt materials were available for sale in Canada in 2012 (Statistics Canada 2013).

In Canada, an estimated 1.25 million tonnes of asphalt shingles and roofing materials are discarded every year into landfills (CCIC 2007). Asphalt shingles can be recycled into hot-mix asphalt for road or trail construction, or used as fuel in cement kilns (CCIC 2007). Asphalt is the most recycled substance in the USA with 80% of reclaimed asphalt pavement being reused in other roads (US EPA 1993). A similar reuse of asphalt is expected to occur in Canada. Up to 100% of existing asphalt used for the construction of roads can be recycled (Martec Recycling Corporation 2016).

Asphalt has been identified by the Organisation for Economic Co-operation and Development (OECD) as an HPV chemical, with 1000 tonnes or more produced per year (OECD 2004).The European Union (EU) and the United States Environmental Protection Agency (US EPA) have also identified asphalt as an HPV chemical (EC 2008a; US EPA 2011). HPV chemicals in the United States are produced or imported in quantities of one million pounds (approximately 450 000 kg) or more per year (US EPA 2011). In the EU, HPV chemicals are produced or imported in volumes of over 1000 tonnes per year (EC 2008a). Asphalt plants in the United States produce estimated 400 million tons of asphalt materials annually (NAPA c2016).

It has been determined from an in-depth literature review and a search of material safety data sheets (MSDS) that asphalt identified as CAS RN 8052-42-4 and oxidized asphalt identified as CAS RN 64742-93-4 are transported to other facilities where they are further refined for use in commercial and consumer products.

Information on the use for asphalt (non-oxidized; CAS RN 8052-42-4) and oxidized asphalt (CAS RN 64742-93-4) is often combined. There are three main types of commercial asphalt produced, as described in Table 5-1.

The United States High Production Volume (US HPV) Program reports that asphalt and oxidized asphalt represent over 99% of all asphalt material used in the United States and Europe, which is used primarily for road surface coating and roofing applications (API 2009). Based on an analysis of information from various sources, Cheminfo (2009) reports that, in the United States and Europe, 80-90% of asphalt is used in road surface coating, 10-15% in roofing applications, and 1-2% in other applications.

Cheminfo (2009) also estimated the proportion of asphalt and oxidized asphalt used in each of the above application types, though there is uncertainty in the values due to lack of quantitative data. It is estimated that 90% of the asphalt used in road surfacing and 50% of applications other than road surfacing or roofing is non-oxidized asphalt (Cheminfo 2009). Approximately 50% of the commercial asphalt in roofing applications is non-oxidized and about 50% is polymer-modified asphalt (CONCAWE 1992).

In Canada in 2012, 4.0 million cubic metres of asphalt and oxidized asphalt was sold (Statistics Canada 2013). Table 5-2 reports the use of these asphalt formulations in three broad sectors. The uses associated with manufacturing primarily correspond to the manufacture of roofing products, which represents about 20% of domestic use of asphalt formulations. Construction, commercial and other uses roughly correspond to road and driveway paving applications and represent approximately 80% of its total use (Statistics Canada 2013). These values are consistent with what has been reported globally.

The second major use of asphalt is in roofing, including underlayments, asphalt shingles, roll roofing, modified bitumen roofing and built-up roofing systems (Statistic Canada 2013; Cheminfo 2009).

A very small proportion of asphalts is used in other diverse applications (IARC 2011), many of which need to be purchased directly from the distributor. These include, but are not limited to, damp-proofing and waterproofing; mastic asphalt for industrial flooring; building papers; primes; caulking compounds; acoustical blocks, compositions, felts; bricks; joint filler compounds; soundproofing; stucco base; lining irrigation canals, water reservoirs, dams, and dykes; protective coatings for walls, cars, and water mains; brake linings; clutch facings; rubber extenders; lubricating grease; printing inks; well drilling fluid; boat deck sealing compound; enamels; paints; adhesives for the building industry; coal briquetting; electrical insulation; and battery making (US DHHS 2000, Inchem 1982, HSDB 2009, Al 1990a in API 2009).

Asphalt was first registered in Canada in 1973 as an active ingredient under the Pest Control Products Act (PCPA).The pesticides containing asphalt were registered for use in pruning paints with pest control claims as a protective coating against moisture, wood rot disease and wood-boring insects. Under PMRA's re-evaluation program, registrants agreed to remove pest control claims. As a result, registrations of products under the PCPA have expired and the re-evaluation for asphalt was not carried out. Asphalt is not listed as an approved food additive in the Lists of Permitted Food Additives as regulated under the Food and Drugs Act nor has it been identified as being used/present in formulations of food packaging materials or incidental additives that come in contact with foods (Health Canada 2013, November 2014 email from Food Directorate, Health Canada, to Risk Management Bureau, Health Canada; unreferenced).

Asphalt is listed in the Natural Health Products Ingredients Database (NHPID) with a non-NHP role as it is not a naturally occurring substance included in Schedule 1 of the Natural Health Products Regulations. It is not listed in the Licensed Natural Health Products Database (LNHPD) to be present in any currently licensed natural health products (NHPID 2015; Canada 2003; LNHPD 2015).

Releases to the environment may either be of asphalts themselves or of components of asphalt formulations, such as the more volatile components that may be released to air when heated, or the relatively more soluble components that might leach.

Releases of asphalt and oxidized asphalt are not reportable to the National Pollutant Release Inventory (NPRI 2008). However, releases to air including volatile hydrocarbons such as toluene, xylenes, and benzene from Canada's asphalt paving formulations and block manufacturing are reported.

Releases of components of asphalts can also occur from their use in road pavement, roofing, adhesives and sealants, paints and coatings, and miscellaneous consumer products. Meridian (2009) considered the potential releases to be small because asphalt formulations are in solid form.

In general, three operating procedures are involved in the process of transportation: loading, transit and unloading. Loading and unloading of asphalts is normally conducted at sites where access by the general public is limited. The handling of asphalts at petroleum facilities, for the purpose of transportation, is regulated at both the federal and provincial levels, with measures covering both loading and unloading (SENES 2010). Collectively, these measures establish requirements for the safe handling of petroleum substances and are intended to minimize or prevent potential releases during loading, transportation and unloading operations (SENES 2010). Unintentional spills or leaks during the handling and transport processes were considered in this screening assessment for the potential to cause ecological harm.

The Ontario Ministry of the Environment (OMOE) spill database (OMOE 2013) was used to evaluate the frequency and volume of accidental releases of asphalts. The Spills Action Center at the Ontario Ministry of the Environment is responsible for managing oil spill reporting in Ontario. All spills of asphalt materials must be reported, including spills from motor vehicles, although there are exceptions for spills smaller than 100 L unless they are likely to enter waters, or where remediation has not occurred immediately.

The Ontario database does not report spills by CAS RNs; therefore, the analysis captures spills of all asphalt materials as a group. Spills not considered in the analysis were those due to collisions and storms, as well as those occurring on industrial sites (e.g., refineries); the latter were excluded because releases at these locations are expected to be contained and recovered, so the probability of entry into the environment would be minimal.

Finally, landfills that do not collect and treat their leachate may potentially release substances to ground or surface water via leachate. However, release of components from asphalt formulations that are discarded into landfills is expected to be low based on the low water solubility.

When petroleum substances are released into the environment, four major fate processes could take place: dissolution in water, volatilization, biodegradation, and adsorption. These processes will cause changes in the composition of these UVCB substances. In the case of spills on land or water surfaces, photodegradation--another fate process--can also be significant.

Each of the fate processes affects hydrocarbon families differently. Aromatics tend to be more water soluble than aliphatics of the same carbon number, whereas aliphatics tend to be more volatile (Potter and Simmons 1998). It has also been widely demonstrated that nearly all soils and sediments have populations of bacteria and other organisms capable of degrading petroleum hydrocarbons (Pancirov and Brown 1975). However, these generalizations tend to be less relevant when dealing with hydrocarbons with carbon numbers greater than 25, such as asphalts, when water solubility and volatilization are minimal at normal temperatures.

Given that asphalt exists in a semi-solid state and oxidized asphalt exists in a solid state at most temperatures (API 2006), they are unlikely to be found outside of where they were initially applied or spilled. Asphalts are also unlikely to change from the semi-solid or solid state except when being heated for application (API 2006). When released into the environment, regular asphalts (without further treatment) tend to harden and remain intact (CONCAWE 1992); hot asphalt will flow until it cools below its pour point, then it will solidify and not disperse any further; whereas cutback asphalts and emulsified asphalts are fluids at ambient temperatures and thus might be more dispersive. Asphalt formulations for paving will not flow due to the high proportion of gravel and sand. However, heating of asphalts to facilitate paving and roofing applications produces vapours and fumes composed of the lower molecular weight components, which may be inhaled or deposited on the skin or clothing ( US EPA 2011, 2006). Additionally, asphalts in roofing and paving products will become oxidized with exposure to air over time (Robertson 1991).

Due to their high molecular weights and hydrophobic characteristics, asphalts have extremely low water solubility, so that if spilled into water they will sink, rapidly solidify and not disperse. Despite the low solubility of asphalt, however, some of its components such as PAHs, can leach from asphalts. Generally, leaching tests from various asphalt formulations found concentrations of PAHs below detection limits or in the parts per trillion range (ng/L) in the leachate (Brandt and de Groot 2001; Kriech 1990, 1992, Legret et al. 2005; Cooper and Kratz 1996).

Additionally, asphalt in roofing and paving products will become oxidized with exposure to air over time (Robertson 1991). When asphalt is oxidized, ketones and carboxylic anhydrides are formed in the oxidized region of the molecule (Petersen 2009). Oxidized asphalts are produced from asphalt during air-blown processes, during which the softening point and asphaltene content of the product increase linearly (Kleinschmidt and Snoke 1958).

Due to the complex interaction of components within a mixture, which impacts their physical-chemical properties and behaviour, it is difficult to predict the fate of a complex mixture. Therefore, as a general indication of the fate of asphalts, the physical-chemical properties of representative structures of asphalts (Appendix B) were examined.

Based on the physical-chemical properties of representative structures of asphalts, the majority of components are not soluble in water nor easily degraded, and are likely to sorb to soil. The C₂₅-C₅₀ components have boiling points ranging from approximately 395 to 746 °C. The individual components of asphalts are characterized by low water solubilities (2.6 × 10^-21 to 1.5 × 10^-5 mg/L) and low vapour pressures (3.1 × 10^-15 to 4.9 × 10^-4Pa). As noted previously, the solubility and vapour pressure of components within a mixture will differ from those of the components individually and these interactions are complicated for complex UVCBs such as asphalts. In addition, they have very low to very high Henry's law constants (3.3 × 10^-3 to 2.0 × 10¹¹ Pa·m³/mol), high log K_owvalues (10.9-25), and high log K_oc values (7.7-21.6) (Appendix B).

Based on its low vapour pressure (3.1 × 10^-15 to 4.9 × 10^-4 Pa), the majority of components of asphalts are not expected to be found in air (Appendix B). Therefore, releases of asphalts to air are unlikely unless it is heated to a high temperature (e.g., greater than 150 °C). In preparing asphalt, asphalt cement is mixed with either a petroleum diluent, to produce cutback asphalt or with emulsifiers, water and sometimes a small quantity of petroleum diluent, to produce emulsified asphalt. Once the liquefied asphalt cement is applied to the surface of the road, the diluent (petroleum solvent in the case of cutback asphalt and primarily water in the case of asphalt emulsions) evaporates, leaving the residual asphalt cement to perform its function. VOCs are released during this process.

The density of asphalt and oxidized asphalt varies with composition (0.95-1.10 g/mL; Table 3-1), such that, upon entering water some asphalts will float, while others will sink (CONCAWE 2001). Based on the water solubility of these components (2.6 × 10^-21 to 1.5 × 10^-5 mg/L), if a release occurs to water most representative structures of asphalts are not expected to dissolve into water to any great extent, except for naphthalene, which is a minor component as it is outside the boiling range of asphalts. Additionally, asphalts show little tendency to disperse in the water column, but instead will sorb to sediments based upon the high estimated log Koc values of its components (CONCAWE 2001; Appendix B).

Based on the high estimated log K_oc values of components of asphalts, if released to soil, most components are expected to sorb to soil. Volatilization from moist soil surfaces may occur based upon estimated Henry's law constant values of 3.3 × 10^-3 to 2.0 × 10¹¹ Pa·m³/mol for lower molecular weight representative structures of asphalts (alkanes, isoalkanes, cycloalkanes and one-ring aromatics), which might also volatilize from dry soil surfaces based upon their moderate vapour pressures (Appendix B).

Persistence was characterized based on empirical and/or modelled data for a suite of petroleum hydrocarbons expected to occur in asphalts. Model results and the weighing of information are reported in the supporting documentation for the persistence and bioaccumulation of petroleum substances (Environment Canada 2014). These data are summarized in Appendix D.

Empirical and modelled half-lives in the atmosphere for all components of asphalts are less than 2-d (Environment Canada 2014). A number of three- to six-ring PAHs can undergo long-range transport to remote regions due to sorption to particulate matter (Environment Canada 2014).

Considering biodegradation in water, soil and sediment, the following components are expected to have half-lives greater than 6 months in water and soils and greater than a year in sediments: C₃₀ isoalkanes, C₅₀ monocycloalkanes, C₃₀-C₅₀ dicycloalkanes, C₃₀-C₅₀ monoaromatics, C₂₅-C₅₀ diaromatics, C₃₀-C₅₀ three-ring aromatics, and C₂₅-C₃₀ five-ring aromatics. The C₃₀ monocycloalkanes and C₃₀-C₅₀monoaromatics have half-lives greater than a year in sediments (Appendix D).

Asphaltenes and resins, which comprise up to 50% of asphalts, are not represented in Environment Canada (2014); however, their high molecular weight and structural complexity indicate that they likely persist in the environment for a long time.

Bioaccumulation potential for a suite of petroleum hydrocarbons expected to occur in asphalts was characterized based on empirical and/or modelled data. Bioaccumulation factors (BAFs) are the preferred metric for assessing the bioaccumulation potential of substances, as the bioconcentration factor (BCF) may not adequately account for the bioaccumulation potential of substances via the diet, which predominates for substances with log K_owgreater than approximately 4.5 (Arnot and Gobas 2003). Components with carbon numbers greater than greater than C₂₀ have estimated log Kow values of greater than 8 and were not included in the modelling because there were insufficient empirical bioaccumulation data for these components.

The aliphatic and aromatic components of asphalts have carbon numbers greater than C₂₅ and estimated log Kow values greater than 10 (Appendix B). Evidence suggests that substances with log K_ow greater than 8 are not likely highly bioaccumulative due to reduced bioavailability, and there is also evidence that metabolism occurs to some degree (Arnot and Gobas 2006); thus, these substances are not expected to be highly bioaccumulative. While log Kow data were not available for asphaltenes and resins, their high molecular weights (greater than 1000) suggest that they will not easily be absorbed by organisms. Therefore, the asphaltenes and resins are also not expected to bioaccumulate.

Asphalt and oxidized asphalt are not expected to cause acute or chronic toxicity to aquatic organisms due to their extremely low water solubility. As the molecular weight of components of asphalts range from 500 to greater than 5000, and due to their low water solubility, the likelihood of components of asphalts migrating into the water column is small, as demonstrated by the results of toxicity studies as described below. Measured concentrations of asphalt components in leachate from asphalt formulations are presented in Section 8.2.1.

Hot-mix asphalt is used to line fish hatchery ponds that are operated by the Oregon Department of Fish and Wildlife and the Washington State Department of Fisheries, where no apparent adverse impact to the culture and propagation of sport and food fish was observed (API 2009).This indicates that asphalts are not toxic to fish even with long-term exposure.

Mahler et al. (2015) investigated the toxicity of runoff from unsealed asphalt pavement to Ceriodaphnia dubia and Pimephales promelas. Runoff samples were collected from pavement test plots in areas of active parking and driving, and the samples were analyzed for the 16 US EPA priority PAH^Footnote3pollutants, as well as 4H-cyclopenta-[def] phenanthrene, seven N-heterocycles (azaarenes) (i.e., quinoline, isoquinoline, acridine, phenanthridine, carbazole, benzo[c]-cinnoline, and 2,2'-biquinoline; 1-methylphenanthrene), and nitrobenzene (Mahler et al. 2015). Groups of ten organisms in each of four replicates were exposed to runoff samples for 48 h. Three treatments of exposure waters were tested for each runoff sample: 100% runoff, 10% runoff (1:10 dilution with control water), and 0% runoff (100% control water). Mean mortality for both species in 10% and 100% runoff concentrations were less than 5%, and that in the control was less than 2% (Mahler et al. 2015).

Another study demonstrated that asphalt emulsions could stabilize waste incinerator salt and ash and significantly decrease their toxicity: inhibition of the observed parameter (IC50) in organisms (Pseudomonas putida, Lactaca sativa and Sinapis alba) was not observed even with 100% leachate (Vondruska et al. 2002).

Since there were no empirical aquatic toxicity data for asphalt (CAS RN 8052-42-4) or oxidized asphalt (CAS RN 64742-93-4), aquatic toxicity was modeled. PetroTox is an aquatic toxicity model specific for petroleum hydrocarbon mixtures (PetroTox 2012). This model assumes narcosis is the chemical mode of action and accounts for additive effects according to the toxic unit approach. The PetroTox model can be used to predict petroleum hydrocarbon toxicity for C₄-C₄₁ compounds dissolved in the water fraction. Substances smaller than C₄ are considered too volatile to remain in water, while compounds larger than C41 are considered too hydrophobic and immobile, to impart any significant aquatic toxicity. This model is very sensitive to the proportion of hydrocarbons considered to be sufficiently soluble to impart toxicity. Thus, the model was run assuming a 1:1 ratio of components within the C₂₅-C₃₅ versus C₃₆-C₄₁ carbon ranges for illustrative purposes. The model cannot be applied to asphaltenes or resins, which comprise up to 50% of asphalts. However, given the physical-chemical properties of asphaltenes and resins (i.e., high molecular weight and low water solubility), they are not expected to be bioavailable or toxic to aquatic organisms.

The PetroTox model generates estimates of toxicity with a median lethal loading concentration (LL₅₀) rather than a median lethal concentration (LC₅₀) due to the insolubility of petroleum products in water. The LL₅₀ value is the amount of petroleum product needed to generate a water-accommodated fraction (WAF) that is toxic to 50% of the test organisms. It is not a measure of the concentration of the petroleum components in the WAF. The modelled ecotoxicological data in Table E-1 (Appendix E) indicates that even if assuming that as much as half the asphalt components are in the more bioavailable range (i.e., carbon number less than C₃₆), the acute toxicity is still extremely low for all test organisms, as indicated by LL₅₀ values greater than 1000 mg/L. While the proportion of components in asphalts within certain carbon ranges is unknown, the ratio used in the model is considered a reasonable conservative approximation and indicates low hazard.

The predicted toxicity of asphalts was comparable to empirical results from toxicity studies with aromatic extracts in the carbon number range of C₂₀-C₅₀ (Table E-2 in Appendix E). Aromatic hydrocarbons are considered to contribute the most to petroleum toxicity (Verbruggen et al. 2008). Therefore, the predictions from the PetroTox model are considered relevant and reliable.

Asphalts used for road paving and roofing are subject to leaching. However, asphalts predominantly contain large hydrocarbons with molecular weights in the range of 500-15 000 (API 2009) with low solubility, which are generally considered to have low bioavailability and ecotoxicity (see Sections 7.2.2 and 8.1).

Extensive research has been conducted on the leaching of PAHs from asphalt formulations used as pavement and roofing materials. This assessment considers PAHs leaching from asphalt formulations (such as asphalt emulsion, cutback asphalt and hot-mix asphalt) that might contain other petroleum substances (e.g., aromatic extracts, base oils, gas oils, kerosene, naphtha and heavy fuel oils). Thus, the release of these other petroleum substances from asphalt formulations is addressed in this assessment.

Leaching tests conducted on asphalt formulations (e.g., hot-mix asphalt, asphalt concrete pavements and roofing asphalts) have shown that equilibrium concentrations of PAHs in the leachate are generally below detection limits or are typically in the parts per trillion range (ng/L); however, low concentrations of some PAHs (e.g., naphthalene and phenanthrene) are often found in leachate (Kriech 1990, 1992a; Brandt and de Groot 2001; Kriech et al. 2002). The individual PAH concentrations measured in those laboratory leaching studies are shown in Table E-3 (in Appendix E). Kriech (1990) measured 16 PAHs in extracts from leaching tests with new (uncontaminated) hot-mix asphalt and detected only naphthalene at a concentration of 0.25 μg/L. Similar results were reported for leaching tests using new hot-mix asphalt and field samples of hot-mix asphalt collected from various locations on a road (Kriech 1992a). Only naphthalene was detected in samples collected from the road with concentrations ranging from 0.26 to 0.31μg/L; naphthalene at 0.76 μg/L was measured in soil extracts of samples collected from the shoulder of the road (Kriech 1992a). With further development of laboratory analytical methodology, Brandt and de Groot (2001) detected low concentrations of PAHs (less than detection limit for benzo[a]pyrene (B[a]P) to 0.12 μg/L for naphthalene) in leachates from conventional penetration grade asphalt using high-performance liquid chromatography (HPLC) analysis. Mahler et al. (2004) found that of 17 PAHs (15 of the 16 US EPA priority PAHs plus 9h-fluorene and nitrobenzene) analyzed, only anthracene was detected in the laboratory simulated runoff from test plots and a used parking lot sealed with asphalt emulsion at an estimated concentration of 0.09-0.23 μg/L (depending on the sampling date as the concentration decreased over time) and 0.42 μg/L, respectively. In this and similar studies, the concentration of PAHs in runoff was initially small and decreased over a seven-week period following application (Mahler et al. 2004, 2005; Rowe and O'Connor 2011).

Except for those test samples of new asphalt formulations obtained directly following manufacture, some PAHs in leachate might be from other sources such as vehicle tire wear and contamination from transportation. Old or weathered asphalts, as demonstrated through leaching studies, are likely to contain multiple sources of petroleum products (e.g., vehicle emissions, lube oils, and tire wear). Therefore, leaching studies on fresh asphalts provide a better indication of what could be released from asphalts. In a study by Birgisdottir et al. (2007), PAH leached from samples collected on the surface of an old road built in 1980 were much more elevated compared to the samples from the base layer of a new road. The PAH concentrations from the base layer of a new road are considered more reliable for evaluating PAH leachability from asphalts because the top layer is likely contaminated.

Slightly higher release of PAHs from cutback asphalts than from asphalt emulsions and hot-mix asphalt was observed (Table E-3 in Appendix E). Kriech (1992b) found relatively higher PAHs in the leachate from new asphalt emulsion, gelled asphalt and cutback asphalt. Material safety data sheets from various companies for these three asphalt formulations identified the presence of solvents such as kerosene or fuel oil no. 2 in the formulations (MSDS 2006, 2007a,b), though asphalt emulsion does not usually contain solvent. The PAHs in the leachate mostly originate from the solvent components in the formulation. The solvent components are volatile; when exposed to air, they evaporate and leave the hard asphalt at the site of application after curing (Speight 2014). Rapid-curing (RC), medium-curing (MC) and slow-curing (SC) cutback asphalts are classified depending on the relative speed of evaporation, and they contain solvents with different boiling points (Asphalt Institute 2007). RC and MC asphalts generally contain solvents with a boiling point similar to naphtha and kerosene, respectively (Environmental Health Strategies 2010). These solvents are volatile, and if released to the environment, they will not likely persist for long in the air (Environment Canada 2014). SC asphalts generally contain solvents with a boiling point similar to fuel oils. Although the SC asphalt solvents are less volatile and more persistent than naphtha and kerosene, asphalt can entrap these solvents and limit their availability to the environment and the organisms (Meegoda 1999; Vondruska et al. 2002).

The slightly higher release of PAHs from cutback asphalts (as shown in Table E-3 in Appendix E) is not continuous. The risk of release is greatest following application and before it is fully cured. Cutback asphalt is primarily used as prime and tack coat (Environmental Health Strategies 2010). Prime and tack coats are used for preparing the surface and promoting bonding to the subsequent pavement layers; they are applied only when the road is constructed and are subsequently covered underneath after paving (US DOT 2005; TDOT 2017). Spray application of cutback asphalts might result in release of VOCs, which will quickly dissipate. In addition, cutback asphalts are less commonly used today due to the release of VOCs and the cost of petroleum solvents (US NTP 1997).

In preparing asphalt, asphalt cement is mixed with either a petroleum diluent, to produce cutback asphalt or with emulsifiers, water and sometimes a small quantity of petroleum diluent, to produce emulsified asphalt. Once the liquefied asphalt cement is applied to the surface of the road, the diluent (petroleum solvent in the case of asphalt cutbacks and primarily water in the case of asphalt emulsions) evaporates, leaving the residual asphalt cement to perform its function. VOCs are released during this process.

Studies with reclaimed asphalt pavement samples have found that the majority of PAHs are below detection limit ranges (Brantley and Townsend 1999; Townsend 1998; Legret et al. 2005). Legret et al. (2005) detected B[a]P and fluoranthene at concentrations greater than their respective detection limits in leachate from a reclaimed asphalt pavement sample.

Increased temperatures, the presence of road salts and high acidity can increase the rate of leaching from fresh asphalt. This was shown to be the case in a chemical oxygen demand leaching test in which the amount of organic components in the leachate was determined by the oxygen consumption for complete chemical oxidization (Cai et al. 2009).

The amount of PAHs that can effectively leach from asphalt is dependent upon the amount of PAHs that are present. Roofing asphalt formulations contain lower concentrations of PAHs (range: 4-23 mg/kg) compared to road asphalt formulations (range: 1.9-66 mg/kg) (Kriech et al. 2002). Kriech et al. (2002) did not find any PAHs leaching from four roofing test samples. In tests on the aqueous leaching of PAHs from commercially available asphalt formulations, the level of PAHs leaching from roofing asphalts was minimal and generally lower than that from paving asphalts (Table E-3 in Appendix E; Brandt and de Groot 2001). Similarly, the PAH concentration of the asphalt-based pavement sealant (i.e., 50 mg/kg) (Mahler et al. 2012) is within the same range as asphalt formulations (Kriech et al. 2002) and is much lower than that of coal-tar-based pavement sealant (i.e., 66 000 mg/kg) (Mahler et al. 2012). The total PAH concentrations in runoff water from asphalt-based pavement sealant is low (i.e., 2 ug/L), compared to that of coal-tar-based pavement sealant (i.e., 71 ug/L) (Watt et al. 2010; Mahler et al. 2012).

Some studies show that asphalt emulsions can stabilize and solidify petroleum-contaminated soils to produce quality construction material (Meegoda 1999). Concrete made from cold-mix asphalt (CMA) consisted of asphalt emulsions mixed with six levels of petroleum-contaminated soils (PCSs). A uniform leaching test was designed to simulate the contaminant release rate from CMA made with PCSs when used as pavement and exposed to realistic environmental conditions. The structural integrity of the samples was kept intact during the test. Only the low molecular weight hydrocarbons (i.e., 2-methylpentane, heptane, benzene, toluene, ethylbenzene, m-xylene, o-xylene and 1,2,4-trimethylbenzene) found in the PCSs were analyzed. None of these compounds leached from any of the six mixtures (the detection limit was approximately 0.1 part per billion), except for iso-octane, which was present in two soils at 12.5 and 10 ppm (12.5 and 10 mg/L) (Meegoda 1999). While components from the cold-mix asphalt were not measured, the ability to entrain the low molecular weight and more soluble compounds within the cold-mix asphalt concrete indicates that the larger components of asphalts should be similarly entrained and have low leachability. Loss of the low molecular weight contaminants due to volatility is possible during the preparation of the cold-mix asphalt concrete, so the leaching test might have underestimated the leachability of the contaminants compared to the original amount in the contaminated soil. In addition, Vondruska et al. (2002) demonstrated that asphalt emulsions could stabilize salt and ash, which further supports the entrainment of low molecular weight substances in in asphalt.

Studies on metals leached from asphalts are also available. Aluminum and mercury were found at concentrations of 0.014 and 0.027 mg/L, respectively (Azizian et al. 2003). However, other studies identify metals as coming from the aggregate in the pavement and not from the asphalt itself (Kriech 1990, 1992; Brantley and Townsend 1999; Azizian et al. 2003). These metals include aluminum, barium, chromium, lead, and mercury. Therefore, metals leaching from asphalt are not considered further in the assessment.

Leaching of other components of asphalts, such as aliphatics, resins and asphaltenes, is expected to be lower than PAHs due to their lower solubilities. Furthermore, the solubility of PAHs decreases with increased alkylation of the PAH (Gustafson et al. 1997). Overall, exposure of ecological receptors to asphalt components in leachates is considered limited based on the very low concentrations of PAHs leaching from asphalt paving and roofing formulations.

Spill data from the Ontario Ministry of the Environment databases were analyzed. The spill data reported under "asphalt" in this database included data from both liquid asphalt and asphalt found in shingles (roofing materials) or mixed with aggregates (pavements). However, it is unclear how many spills within the database were liquid asphalt, hot-mix asphalt, or asphalt shingles as this was not consistently recorded. The spills that include shingles or road debris are primarily composed of aggregate, typically gravel or sand, with only 5%-35% of the mixture being asphalt (Kreich et al. 2002; CCIC 2007).

There were 37 spills of asphalt materials reported to the Ontario Ministry of Environment from 2008 to 2012 (Table C-2 in Appendix C). Of the reported spills in the Ontario database between the years 2008 and 2012, the volume released was reported for 25 of these spills (Table C-2 in Appendix C). The average number of spills reported annually was less than eight (OMOE 2013). The total known spill volume was 154 017 L, with a median of 600 L. Most spills were to land (30 incidences), followed by five spills to water and one release to air; one incident did not report the spill medium (Table C-3 in Appendix C). Various causes for spills of asphalt materials were reported such as discharges or bypass to a watercourse, overflow, pipe, hose or valve leakage or failure, or process upset/malfunction. The causes for ten spills (25.4% by volume) were not specified (Table C-4 in Appendix C; OMOE 2013).

Once spilled, asphalts are generally not expected to disperse in the environment because of the high viscosity, high Kow and Koc, and low water solubility of their components (see Section 7.1). Regular and oxidized asphalts will tend to harden and remain intact upon release. Cutback asphalts and emulsified asphalts are liquids at ambient temperatures and will be more dispersive if released. However, the use of cutback asphalts is less common nowadays, which limits its potential release from spills.

No adverse effects were observed in fish in aquaculture ponds with asphalt linings (API 2009). Oxidized asphalt also had no effect on the growth of either bean or corn seeds (WHO 2004). Modelled toxicity for asphalts indicates low toxicity (LL50's greater than 1000 mg/L assuming 50% of components are less than C₃₆) (PetroTox 2012).

Studies on the leaching of components from asphalt formulations reported low or undetectable concentrations of PAHs and inorganics from the examined asphalt road pavement and roofing formulations (API 2009; Kriech 1990, 1992a; Brandt and de Groot 2001; Kriech et al. 2002). Most PAH concentrations were lower than the detection limit or the CCME water quality guideline with a few exceptions (see Table E-3 in Appendix E). The relatively high PAH concentrations in leachates from aged asphalt road surfaces were attributed to contamination from other sources (see Section 8.2.1). Concentrations of PAHs in laboratory simulated runoff from unsealed asphalt pavement, asphalt emulsion sealed test plot and a used parking lots were not detected or were low; and the concentrations decreased over time (Mahler et al. 2004, 2012). The toxicity of runoff from unsealed asphalt did not show significant mortality in aquatic species exposed to diluted or undiluted runoff samples (Mahler et al. 2015). Although the particulate-phase PAHs are also present in the runoff besides the dissolved phase, it is of lower concern as the PAHs in the particulate fraction often have high molecular weight and low water solubility, hence they are not likely bioavailable to the aquatic organisms. The release of these PAHs will contribute to the loading of PAHs in the sediment that has been previously assessed (Environment Canada, Health Canada 1994). These findings indicate that exposure to the components leaching from asphalt formulations, whether used on paved surfaces, roofs, or disposed of in landfills, pose a low risk to the aquatic environment.

In addition to a low leaching of components of asphalts, asphalt formulations have been used to stabilize and solidify petroleum-contaminated soils and waste incinerator salts and ash. The ability of asphalts to bind hydrocarbons and other contaminants (e.g., metals) can significantly decrease the availability of these potential contaminants to leach out to the environment (Meegoda 1999; Vondruska et al. 2002). This process would also occur with hydrocarbons naturally present within the asphalts, limiting their availability and ability to leach from the cured asphalt formulations.

For reclaimed asphalt pavement (RAP), the origin of some substances measured in leaching studies is uncertain, because the recycled asphalt formulations might have been exposed to vehicle emissions, lube oils, gasoline and metals from brake pads during their original use (Brantley and Townsend 1999, Norin and Strömvaix 2004). However, since the asphalt formulations are recycled, any PAHs from these sources will be mixed into asphalt and likely entrapped.

For cutback asphalt, the slightly higher release of asphalt components in leachate than from asphalt emulsion and hot-mix asphalt is still of low significance (Table E-3 in Appendix E), because most of the PAHs in the leachate are below the CCME quality guideline, and will likely be further diluted by runoff and result in even lower concentrations in the environment. The major use of cutback asphalt as prime and tack coat is infrequent and does not result in continuous release. Furthermore, the decreased use of cutback asphalts also limits the exposure of cutback asphalt (US NTP 1997). Therefore, the exposure from cutback asphalts is considered low.

Although the toxicity data of asphalts to terrestrial organisms are limited, asphalts are not considered to be toxic to terrestrial plants.

Very limited ecotoxicity data were available for asphalts or asphalt formulations overall. However, the observed low toxicity in the available studies, as well as the physical-chemical properties (e.g., high Kow, high Koc and low water solubility) of components of asphalts, and the very high molecular weight of asphaltenes and resins as major chemical classes in asphalts, indicate that asphalts are not likely to enter the environment in such a way as to be bioavailable or cause direct toxicity.

The use of asphalts in industrial operations may result in release of components in sludge and biosolids, if water is used to clean production equipment and/or facilities. However, because components of asphalts are generally not bioavailable, the risk is considered low.

A total of 37 spills of asphalt materials were reported in the Ministry of Ontario database. They are not likely to disperse in the environment once spilled, due to their low mobility. The lack of bioavailability and the low toxicity of asphalts indicate that the ecological concern is likely low when spilled.

Modelling the physical and chemical properties, as well as the persistence and toxicity of asphalts, is based on representative structures potentially found in asphalts, which do not include some of the principal components, namely asphaltenes and resins, due to their extreme complexity and variability. The physicochemical properties of 22 representative structures were used to estimate the behaviour of asphalts. The reliance on this method for the physical and chemical characteristics, as well as for persistence and bioaccumulation potential, is a source of uncertainty in the prediction of partitioning to different environmental compartments and given the lack of empirical data for these processes. Given that a variety of different representative structures may be derived for the same petrochemical, it is recognized that structure-related uncertainties exist for these substances. The lack of specific proportions of representative structures in asphalts is also a source of considerable uncertainty. However, the physical-chemical properties (very low water solubility and very large molecular weight) of most components of asphalts, including asphaltenes and resins, indicate that they are not bioavailable and have low toxicity.

Leaching data for asphalt formulations are not specifically associated with a CAS RN, as leaching of PAHs from various types of asphalt formulations were considered. The amount of PAHs in the leachate originating from asphalts was also uncertain. However, even when considering multiple sources of PAHs in the leachate, the overall release is insignificant, which was evident in the aquatic toxicity study on runoff from a parking lot (Mahler et al. 2015).

There were insufficient data to evaluate the release of petroleum substances from all types of use of asphalt formulations, (e.g., cutback asphalts used as stock pile mixes and cold patching). However, it is evident that once a substance in the formulations is mixed with asphalt, it is likely entrapped in asphalt and has decreased environmental availability (Meegoda 1999; Vondruska et al. 2002).

Large quantities of asphalt formulations are disposed of in landfill each year. Components of asphalts, such as PAHs, may contribute to the total concentration of these individual chemicals in the landfill leachate. While available evidence on the leaching of PAHs from asphalt formulations indicates low risk, the environmental conditions within a landfill could affect the leachability of components out of asphalt formulations. It is currently not possible to estimate what the contribution of asphalt formulations to landfill leachate might be. However, the physical-chemical properties of most components of asphalts indicate that asphalts are not bioavailable and have low toxicity.

This assessment focuses on estimating general population exposures to volatile substances released during the production, refining and use of asphalt and oxidized asphalt, in areas surrounding industrial and application sites. Estimates are also derived for exposures to asphalts that may occur from the use of consumer products containing asphalts, as well as for ingestion of house dust that may contain substance components that originate from asphalt-based pavement sealant. Determining the potential for exposure to various substances found in asphalts from consumer products is difficult due to the variable nature of both the product formulations and the substance composition of asphalts.

Polycyclic aromatic hydrocarbons (PAHs), naphthalene and benzene are minor components of asphalts that are the basis of characterizing long-term exposure to asphalts, and are recognized as presenting a potential hazard to human health. These substances have been previously assessed by the Government of Canada and are included on the List of Toxic Substances in Schedule 1 of CEPA (Environment Canada, Health Canada 1993, 1994, 2008). Benzene, naphthalene and PAHs are organic compounds that contain only carbon and hydrogen atoms that form aromatic rings, where benzene contains a single ring and PAHs contain two or more fused rings.

Given that asphalts are predominantly composed of non-volatile substances, inhalation exposure of the general population to fugitive emissions of components of asphalt in the vicinity of industrial facilities that process, handle and store asphalt is expected to be low, even at elevated substance working temperatures. However, a Hot Mix Asphalt Plants Emissions Report (US EPA 2000) was prepared by the Office of Air Quality Planning and Standards at the U.S. Environmental Protection Agency that characterized asphalt emissions to air. These emissions data were therefore used as input parameters in SCREEN3 for dispersion modelling (SCREEN3 2011), in order to confirm the low potential for exposure to benzene and PAH components that may be released during the handling and storage of bulk quantities of asphalts (see Appendix F for input parameters) (US EPA 1992a). Emissions were considered to originate from an area source, given the size, potential points of emissions, and locations of the facilities involved. Total emission rates of benzene were reported to be 12.85 kg per year for a 100 000 tonne batch mix asphalt plant and 35.96 kg per year for a 200 000 tonne drum mix asphalt plant (US EPA 2000).

SCREEN3 is a screening-level Gaussian air dispersion model based on the Industrial Source Complex (ISC) model (for assessing pollutant concentrations from various sources in an industry complex) (SCREEN3 2011). The driver for air dispersion in the SCREEN3 model is wind. The maximum calculated exposure concentration is selected based on a built-in meteorological data matrix of different combinations of meteorological conditions, including wind speed, turbulence and humidity. This model directly predicts concentrations resulting from point, area and volume source releases. SCREEN3 gives the maximum concentrations of a substance at chosen receptor heights and at various distances from a release source in the direction downwind from the prevalent wind one hour after a given release event. During a 24-hour period, for point emission sources, the maximum 1-hour exposure (as assessed by the ISC Version 3) is multiplied by a factor of 0.4 to account for variable wind direction. This gives an estimate of the air concentration over a 24-hour exposure (US EPA 1992a; SCREEN3 2011). Similarly, for exposure events happening over the span of a year, it can be expected that the direction of the prevalent winds will be more variable and uncorrelated to the wind direction for a single event; thus, the maximum amortized exposure concentration for one year is determined by multiplying the maximum 1-hour exposure by a factor of 0.08 (US EPA 1992a; SCREEN3 2011). Such scaling factors are not used for non-point source emissions. However, to prevent overestimation of the exposures originating from area sources, a scaling factor of 0.2 was used to obtain the yearly amortized concentration from the value of the maximum 1-hour exposure concentration determined by SCREEN3(SCREEN3 2011).

The results of the dispersion modelling indicate a low level of benzene at a distance of 230 m from the fence-line of the facility, where this distance represents the maximum concentration of benzene found in air (Table F-2 of Appendix F). Map analysis suggests that residential homes may exist within this distance, which could lead to an incremental increased long-term exposure to benzene for those residing in the vicinity of such facilities. The annual concentrations of benzene at 230 m were estimated to range from 0.018 to 0.051 μg/m³, a fraction of the 2009 Canadian average background concentration of benzene in ambient air of 0.32-0.84 μg/m³ for rural and urban areas (NAPS 2012).

Total emissions of six individual PAHs (benzo[a]pyrene, benzo[a]anthracene, benzo[b]flouranthene, benzo[k]flouranthene, dibenz[a,h]anthracene, indeno[1,2,3-cd]pyrene) from asphalt refining were also estimated by dispersion modelling using SCREEN3. PAHs with 5 or more rings have been shown to be predominantly particle-bound in the atmosphere, and are typically associated with particles less than 2.5 μm in diameter (Ontario 2011; EC 2001). During normal inhalation exposure to PAH-containing aerosols, the majority (likely greater than 80%) of inhaled PAHs are expected to be deposited on the thin alveolar epithelium and be rapidly absorbed into the blood (Ontario 2011). These considerations support the validity of conducting dispersion modelling for PAHs that originate from asphalt plants, where there could be inhalation exposure to PAHs for those residing in the vicinity.

Relevant parameters that were used in the modelling of PAH dispersion from asphalt plants are presented in Appendix H, Table F-3. The results of the modelling at 230 m from the site of the area release source are presented in Table F-4 for individual PAHs. The concentrations at 230 m were used to characterize risk of long-term general population exposure to PAHs originating from production of asphalts and handling at a facility. For individual PAHs, the estimated concentrations at 230 m range from 0.00016 ng/m³ for dibenz[a,h]anthracene to 0.528 ng/m³ for benz[a]anthracene based on the conservative release quantities associated with drum mix asphalt plants (US EPA 2000). These results corroborate occupational studies that indicate general population inhalation exposure to asphalt components are generally low, including for those down-wind of facilities that heat asphalt (refineries, terminals, hot mix plants, and roofing plants) (Cheminfo 2009).

An occupational exposure study was conducted at an asphalt plant in Germany that measured worker exposure to vapour and aerosols of asphalts (Rühl et al. 2006). During production of asphalts, air monitoring determined that a 95^th percentile exposure to total vapour and aerosols of asphalt would be 33.2 mg/m³(arithmetic mean = 2.11 mg/m³) in the plant. External to the asphalt plant, air monitoring showed that a 95^thpercentile exposure would be 0.88 mg/m³ (arithmetic mean = 0.70 mg/m³), showing that a substantial drop occurs within the facility grounds, over only a short distance from the emissions source. In the same study, B[a]P air concentrations were determined to range from 0.008 to 0.078 mg/m³ in the plant (Rühl 2006). This direct air monitoring study therefore supports the results of air dispersion modelling with SCREEN3 in the estimation of potential long-term exposures of the general population to volatiles of asphalts in the vicinity of asphalt plants.

During paving and roofing operations asphalt is heated to a suitable working temperature and this produces vapours. These vapours cool and condense, producing a substance referred to as asphalt fume. Therefore, exposure can occur to both asphalt vapour and to asphalt fume. The properties of fumes have not been well characterized, but available studies tend to focus on asphalt fumes rather than vapours (Cheminfo 2009, CONCAWE 1992, API 2009). The data indicates that fumes contain low concentrations of PAHs (Van Metre 2012a, Van Metre 2012b, Diamond Environment Group 2011, Inchem 2004).

Application of asphalts to roads, roofs, and other surfaces may result in short-term inhalation exposures for the general population (Cheminfo 2009). No studies were identified which measured air concentrations of asphalt components in the vicinity of paving or roofing activities. However, a number of occupational inhalation exposure studies were identified in the literature. A recent study on personal breathing zone exposures among hot-mix asphalt paving workers measured air concentrations of individual PAHs (Osborn 2013). The highest breathing zone PAH concentration was identified for naphthalene at 1593 ng/m³, exceeding other measured substances by an order of magnitude (Osborn 2013). This concentration was therefore selected as a conservative estimate of potential exposure of the general population in the vicinity of asphalt paving operations. It is noted, however, that exposures of the general population would be lower than the exposure derived from direct occupational exposure.

Historically, asphalts were used to coat the interior of cast iron water pipes (Inchem 2004), but was replaced by cement in the 1970's (Blokker 2013). Thus, exposures via drinking water would be expected to be low.

Asphalt is not listed as an approved food additive in the Lists of Permitted Food Additives as regulated under the Food and Drugs Act nor has it been identified as being used/present in formulations of food packaging materials or incidental additives that come in contact with foods (Health Canada 2013, November 2014 email from Food Directorate, Health Canada, to Risk Management Bureau, Health Canada; unreferenced).Migration into food and subsequent exposure is expected to be limited from petroleum asphalt when used as an indirect additive in food contact substances.

Exposure to asphalts from environmental media, drinking and food is expected to be low.

Asphalt and oxidized asphalt are included on the List of Prohibited and Restricted Cosmetic Ingredients (more commonly referred to as the Cosmetic Ingredient Hotlist or simply the Hotlist). The Hotlist is an administrative tool that Health Canada uses to communicate to manufacturers and others that certain substances, when present in a cosmetic, may contravene (a) the general prohibition found in Food and Drugs Act or (b) a provision of the Cosmetic Regulations. As a result of this prohibition, exposure from cosmetic products is not expected.

Asphalts may be found in adhesives and sealants (e.g., cold-application cement, driveway sealer), paints and coatings (e.g., asphalt primer), and for miscellaneous use (e.g., wall insulation). Many of these products are considered commercial grade and need to be purchased directly from the distributor (Personal communication between Health Canada Risk Management Bureau and Industry, June 2010).

For professional roof resurfacing activities, the potential for inhalation exposure to asphalts for the general population is low. Roof resurfacing occurs outdoors and at variable locations. Any transient inhalation exposures are considered covered by the characterization of bystander inhalation exposure to naphthalene from road paving operations.

There is the potential for direct dermal contact with roofing shingles containing asphalt blends, and with dry asphalt coated surfaces such as driveways and roadways. The use of asphalts in these products is to act as a binder, and therefore by the very nature of this property it is expected there is limited transfer of asphalt components to the skin. Following these types of considerations in the assessment of the variety of products available, the sentinel products considered for estimating direct dermal exposure are driveway sealants and moisture/damping proofing paints, as these products exist in an uncured liquid state. Inhalation exposure to asphalt vapour from these products are expected to be negligible given the ambient application temperature for these products. If inhalation exposures occur, they are considered to be covered by the characterization of bystander inhalation exposure to naphthalene from road paving operations.

Dermal exposure to asphalts from the use of coating products

For estimating dermal exposure to asphalts from the use of consumer products, a scenario was developed that considered an individual applying asphalt-based sealant or waterproofing product once per year as part of regular home maintenance. Spills, splashes and handling of the container or applicator could result in exposure; however, for the purpose of this assessment, incidental contact with a small amount of product is assumed to occur via the palms of the hands. The mass of asphalts in contact with the skin as a result of such an exposure is derived using the EPA-Versar thin film approach (US EPA 2011c). This approach characterizes exposure from a mineral oil substance following a partial wipe of the hands to remove excess material. The substance thickness "thin film" estimated to remain on the skin after wiping was 2.00 × 10^-3 cm. Given an density of 1.1 g/cm³ of asphalts, with sealcoat containing 30% asphalt by weight (w/w) and waterproofing product containing 75% w/w, and with an exposed skin surface area of 227.5 cm² (one quarter of each hand), the mass of asphalt in contact with the skin was estimated to be 149.8 and 375.5 mg, respectively. Using the selected body weight of 70.9 kg (considered to be representative of an average Canadian adult; Health Canada 1998), the dermal dose was therefore estimated to be 2.1 and 5.3 mg/kg-bw, respectively. These estimates are considered to represent exposures that might occur under normal conditions of product use, and to occur yearly.

Oral exposure to components of asphalts via house dust

Asphalts are components of some pavement sealants in Canada that can be applied to residential driveways or small commercial or residential parking lots. A study conducted in Texas analyzed the PAH content in dust found inside 23 ground-floor apartments that had different parking lot surfaces (Mahler et al. 2010). Twelve of the lots were unsealed asphalt or concrete or asphalt sealed with an asphalt-based sealant, and the rest were surfaces that had been sealed with a coal tar-based sealant. The concentration of total PAHs found in the indoor dust samples were calculated as the sum of the 16 US EPA priority pollutant PAHs. The concentrations of PAHs were significantly lower in apartment dust associated with asphalts or concrete surface lots and those sealed with asphalt-based sealant compared with those lots sealed with a coal tar-based sealant (median concentrations of 5.1 vs. 129 μg/g, respectively; Table 9-1). Of 17 variables examined in the apartments, pavement surface type was found to be the most dominant single factor affecting the concentration of PAHs in indoor dust, accounting for 48% of the variance in PAH concentration.

For characterizing risk from exposure to indoor dust associated with asphalt driveways/lots, the average concentration of each of the 16 PAH species identified in the asphalt/concrete samples in Mahler et al. (2010) were used (see Appendix I). It is assumed that each daily dust exposure would contain the same concentration of PAHs.

Supplementary material from Mahler et al. (2010) also shows that the PAH concentration varies depending on the type of asphalt used for the driveway/lot. In house dust, the PAH concentration ranged from 0.06 mg/g (for unsealed asphalt driveways) to 3.91 mg/g (for asphalt-based sealants). For samples taken from ground floor apartments with parking lots, PAH concentrations similarly ranged from 0.06 mg/g for unsealed asphalt to 3.36 mg/g for asphalt-based sealants (Mahler et al. 2010).

Research conducted with support by the US EPA at the University of New Hampshire on simulated seal-coated surfaces resulted in similar findings to those of Mahler et al. (2010). Pavement dust collected from coal tar-based seal-coated surfaces was found to contain up to 1192 mg/kg total PAHs, compared to less than 2 mg/kg collected from unsealed asphalt surfaces (UNHSC 2010).

Appendix I summarizes health effects information for asphalts, including carcinogenicity, the no- and lowest-observed-(adverse)-effect levels/concentrations (N/LO(A)EL/Cs), and corresponding critical effects. Select studies are summarized below.

Asphalt has low acute toxicity, as an oral LD50 value was not established with exposures of 5000 mg/kg-bw in rats, an LC₅₀ value was not established with inhalation exposure of 94.4 mg/m³ over 4.5 hours, and a dermal LD50 was not established with exposure of 2000 mg/kg-bw in rabbits (API 1982; Fraunhofer 2000). In the latter study, a 24-hour occluded exposure on abraded skin with animal monitoring to 14 days did not reveal significant adverse effects (API 1982). Skin irritation was not observed with acute dermal exposures to vacuum residues (CAS RN 64741-56-6) (API 1982). Slight eye irritation was observed for these samples, as well as for undefined asphalt dust (straight or mixed with street dust or inert dust) (API 1982, b; Truc and Fleig 1913).

Repeated dose inhalation studies have used asphalt fume condensate as a source for generating exposures. A LO(A)EC of 100 mg/m³ was identified in rats after nose-only exposure for 28 days, based on changes in lung histology parameters (Fraunhofer 2009). The same authors showed a NOAEC for reproductive and developmental toxicity with exposures of 300 mg/m³. A LO(A)EC of 149 mg/m³ was identified in rats based on degenerative lesions in nasal and paranasal cavities after 14 weeks exposure (Fraunhofer 2001). In a chronic nose-only exposure study in rats, a LO(A)EC of 34.4 mg/m³ was identified based on a statistically significant decrease in body weight (Fuhst et al. 2007).

In short-term dermal studies in rabbits, a LO(A)EL of 2000 mg/kg-bw per day was identified for CAS RN 64741-56-6 based on significantly reduced body weight gain in New Zealand White rabbits. Exposures to two different samples of vacuum residues were via abraded and occluded dorsal skin at 200, 1000 and 2000 mg/kg-bw, 6 hours per application, three times weekly for 4 weeks. Reduced body weight gain was seen for animals exposed to only one of the two similar test substances (API 1983a, b).

The International Agency for Research on Cancer (IARC) concluded there is inadequate evidence that asphalts are carcinogenic to humans (IARC 1998). However, there is sufficient evidence in animalsfor the carcinogenicity of extracts of steam-refined asphalts, air-refined bitumens and pooled mixtures of steam- and air-refined asphalts. Extracts of steam-refined and air-refined bitumens were classified as possible human carcinogens (Group 2B). There is limited evidence for the carcinogenicity of undiluted steam-refined bitumens and for cracking-residue asphalts in animals and there is inadequate evidence for the carcinogenicity of undiluted air-refined asphalts.

The potential for dermal carcinogenicity of asphalt has been investigated in multiple skin painting studies using whole asphalts of different grades, or asphalt fume condensates. Of 218 Swiss mice exposed to different samples of 10% whole asphalt in benzene, 6 developed skin tumours for an overall tumour incidence of 2.7% (Wallcave et al. 1971). Tumour incidences of 2.55% and 14.3% were observed in a study that exposed mice to either 40% of straight or cracked asphalt, respectively (Kireeva 1968). Road and roofing asphalts (diluted with acetone) showed carcinogenic activity in mice but not in rabbits (Hueper and Payne 1960). Another study exposed 50 mice to steam- or air-refined asphalts, resulting in 3 and 9 total skin tumours, respectively (Simmers 1965). A lack of carcinogenic activity was reported in a study that exposed male C3H mice to 30% whole asphalt in mineral oil (McGowan et al. 1992).

Asphalt fumes generated in laboratories under high temperature have been shown to produce skin tumours in mice (see Appendix I). However, it has been demonstrated that laboratory-generated asphalt fumes are compositionally different from the fumes generated by road workers (McCarthy et al. 1999; Reinke et al. 2000). For example, in the lab, asphalts are heated to higher temperatures under vacuum and with continuous agitation for significantly longer periods of time in order to generate a sufficient yield of fumes for exposure experiments (Niemeier et al. 1988). These methods alter the chemical composition of the fumes, resulting in higher concentrations of volatiles, thus reducing the relevance of any testing results to exposure to fumes that are generated under different conditions by road workers (McCarthy et al. 1999).

Only limited evidence for carcinogenicity has been derived from studies assessing inhalation to "real world" asphalt fumes. SPF-Wistar rats did not exhibit an increase in tumours from nose-only exposure to 4, 20 and 100 mg/m³ total hydrocarbons as derived from paving asphalt fume condensate (obtained from the overhead space of a hot storage tank of semi-blown paving asphalt) (Fuhst et al. 2007). However, a poorly differentiated adenocarcinoma of the nasal cavity was observed in a single male of the high-dose group, and therefore a link with asphalt fume exposure could not be ruled out (Fuhst et al. 2007). In another study, one bronchial adenoma was observed in C₅₇ black mice exposed to fumes from a pooled asphalt sample heated to 120^oC (Simmer 1964). However, no lung cancer developed in Besthesda black rats and Strain-13 guinea pigs exposed to fumes from a roofing asphalt (Heuper and Payne 1960). Some animals did develop chronic fibrosing pneumonitis with peribronchial adenomatosis.

The available in vivo genotoxicity tests on asphalt and asphalt fumes had mixed results. Oral exposure to vacuum residuum did not cause chromosome damage in Sprague-Dawley rats (API 1984c, d). Nose-only exposure to asphalt fume condensates under realistic fume generation and exposure conditions did not induce cytogenic damage in the respiratory or hematopoetic systems of Wistar rats (Fraunhofer 2009). At the highest dose level, asphalt fume condensates (collected from the top of a paving storage tank at a temperature of 160^oC) caused increased micronuclei after intra-tracheal instillation, but also caused cytotoxicity at this dose (Ma et al. 2002). In another study, DNA adducts were seen in lung cells, but not in leukocytes obtained via cardiac puncture, in male CD rats exposed to condensed asphalt fumes that were generated at 316^oC (Qian et al. 1998). DNA adducts were not seen in transgenic mice and rats exposed to total particulate paving asphalt fumes that were generated at 170^oC (Micillino et al. 2002; Bottin et al. 2006). Single-strand DNA breaks were seen in Sprague Dawley female rat alveolar macrophages and lung tissue, but micronucleus formation was not apparent in bone marrow polychromatic erythrocytes (Zhao et al. 2004).

Whole asphalts were generally non-mutagenic or weakly mutagenic in in vitro mouse lymphoma and Ames assays (API 1984c, d; Robinson et al. 1984; Monarca et al. 1987). Asphalt fumes collected at approximately 146 to 157^oC from the headspace of an asphalt storage tank at a hot-mix asphalt production plant were not mutagenic in the modified Ames assay, whereas fume condensates generated in the laboratory at 149^oC and 316^oC were mutagenic (Reinke et al. 2000). The mutagenicity of asphalt fume condensates also varied with the origination of crude oil feedstock, but the effect of the generation temperature on mutagenicity could not be determined (Machado et al. 1993). DNA adducts have also been demonstrated in vitro with asphalt fume condensates generated using laboratory conditions (DeMéo et al 1996; Akkineni et al. 2001).

Epidemiology studies on asphalts provide limited evidence on the carcinogenicity of asphalts. Roofers have shown an excess of lung cancer, but it is uncertain whether this excess was related to asphalts or to known carcinogens such as coal tar or asbestos (Hammond et al. 1976; Menck and Handerson 1976; NIOSH 2000), although IARC has indicated that the occupation 'roofing' when using asphalt is probably carcinogenic to humans (Group 2A) (IARC 2011). Some epidemiologic studies of road pavers exposed to asphalt fumes reported an elevated risk for lung cancer. However, design limitations of these studies confound the results, and include smoking, and likely exposure to coal tar, traffic exhaust, diesel exhaust, silica and asbestos (Darby et al. 1986; Burgaz et al. 1988; Gunkel 1989; Pasquini et al. 1989; Hansen 1991; NIOSH 2000). There are several studies that show cytogenetic effects in blood cells of asphalt field and paving workers, including micronuclei, sister chromatid exchange and DNA strand breaks (Burgaz et al. 1998; Murray and Edwards 2005; Cavallo et al. 2005). Other studies do not reveal genotoxic effects including a negative result for sister chromatid exchange in paving workers (Cavallo et al. 2005). The results from these studies typically derive from small sample size populations, and are confounded by co-exposure to other materials such as coal tar fumes, diesel exhaust and asbestos, as well as lifestyle factors (e.g., grilled and smoked food intake).

9.2.3.1 Polycyclic aromatic hydrocarbons

Although asphalts are known to contain only a low level of PAHs, PAH species have a wide carcinogenic potency range. IARC (2010) recently reviewed the carcinogenicity data in experimental animals for 60 PAHs: 13 have sufficient evidence, 16 have limited evidence and 31 have inadequate evidence. Some PAHs, including B[a]P are classified as Category 1B carcinogens 'may cause cancer' by the European Commission (2008a). PAH species that have sufficient toxicological information can be ranked according to toxicological potency relative to B[a]P (Appendix J).

The Government of Canada previously completed a human health risk assessment of certain PAHs, including B[a]P, under the Priority Substances List Program. Based primarily on the results of carcinogenicity bioassays in animal models, five PAHs were considered "probably carcinogenic to humans", substances for which there is believed to be some chance of adverse effects at any level of exposure (Environment Canada, Health Canada 1994). PAHs were added to the List of Toxic Substances in Schedule 1 of CEPA.

The US EPA previously identified PAHs that may be carcinogenic in animals and humans (US EPA 1992b), ultimately listing 16 substances that became known as the priority pollutant PAHs (Menzie et al. 1992; US EPA 2013). They are naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b+j]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, dibenz[a,h]anthracene and benzo[ghi]perylene.

Several authors have created toxic or potency equivalency factors (PEFs) for numerous PAH species (i.e., estimates of their carcinogenic potency relative to that of B[a]P). PEFs as developed by Nisbet and LaGoy (1992) were used in this assessment (Appendix J). The PEF approach to estimating carcinogenic potency is an accepted method for human health risk assessment of PAH-rich mixtures, and has been widely used by several international organizations (EC 2008b; WHO 1998, 2001). The PEF approach has been adopted herein as a method to characterize the theoretical carcinogenic risk from oral exposure to PAH-containing house dust. It is noted that the empirical evidence to date is inconclusive for the carcinogenicity of asphalts (CAS RN 8052-42-4 and 64742-93-4) as whole substances.

In 2015, Health Canada used the B[a]P-specific tumour data in mice provided in Culp et al. (1998) to derive a lower limit of a one-sided 95% confidence interval of a carcinogenic benchmark dose for B[a]P (Health Canada 2015). This reference value, referred to as an oral BMDL₁₀, was calculated to be 0.545 mg/kg-bw/day, and is based on forestomach papillomas and/or carcinomas in female B6C3F1 mice (Health Canada 2015). This is of the same order of magnitude as oral BMDL₁₀ values for B[a]P derived by other groups, including the WHO. Using tumour data based on exposure to coal tars in mice, JECFA calculated a BMDL₁₀ range for B[a]P of 0.1-0.23 mg/kg-bw/day (FAO/WHO 2006). Wester et al. (2012) recently proposed 3 mg/kg-bw/day based on hepatocellular carcinomas in B[a]P-exposed Wistar rats. Health Canada's Guidelines for Canadian Drinking Water Quality proposed a maximum acceptable daily intake concentration of 0.04 μg/L for B[a]P (Health Canada, 2015).

Additionally, the Goverrment of Canada previously developed estimates of carcinogenic potency associated with the inhalation of B[a]P. A tumourigenic dose (TD₀₅) was calculated to be 1.57 mg/m³ based on respiratory tract tumours in laboratory animals (Thyssen et al. 1981), using a multi-stage model (Environment Canada, Health Canada 1994).

9.2.3.2 Benzene

In the initial stages of asphalt processing, it may contain low levels of the high-hazard component benzene; however, upon processing, handling and heating, benzene is lost through the vapour phase of asphalts. Benzene has been assessed by the Government of Canada (Environment Canada, Health Canada 1993), was determined to be a carcinogen and was added to the List of Toxic Substances in Schedule 1 of CEPA. International organizations have drawn similar conclusions; IARC classifies benzene as Group 1 (carcinogenic to humans) (IARC 2012). The Government of Canada has previously developed estimates of carcinogenic potency associated with inhalation exposure to benzene. A 5% tumourigenic concentration (TC₀₅) for benzene was calculated to be 14.7 × 10³ μg/m³ (Environment Canada, Health Canada 1993) from the epidemiological investigation of Rinsky et al. (1987), based on acute myelogenous leukaemia in Pliofilm workers. The TC₀₅ value is the air concentration of a substance associated with a 5% increase in incidence or mortality due to tumours (Environment Canada, Health Canada 1993). Reference values for benzene from other international agencies (US EPA 2000, WHO 2000) are similar to the TC05 used below in this screening assessment for the characterization of risk to human health.

9.2.3.3 Naphthalene

A non-cancer health effects database for naphthalene was available and considered. Naphthalene was previously assessed by the Government of Canada (Environment Canada, Health Canada 2008), and a LO(A)EC of 7.86 mg/m³ was considered based on point-of-contact nasal olfactory epithelium injury in mice after a two-hour exposure (Phimister et al. 2004). This effect was also seen in repeated dose studies in rats at 5 and 10 mg/m³(EURAR 2003), and these effect levels have recently been supported by other studies (Dodd 2010, 2012; Cichocki 2014). Other low dose studies were also considered (Clewell 2014). As naphthalene is predominant in heated asphalt vapour (Osborn 2013) and has a low effect level, the short-term critical effect level of 5 mg/m³ was selected to characterize risk of potential transient inhalation exposure of bystanders to volatiles from hot asphalt paving.

A critical health effect for the initial categorization of asphalts were carcinogenicity, based on classifications by international agencies. IARC classifies asphalts as having insufficient evidence for carcinogenicity, however asphalt extracts were considered to range from limited to sufficient evidence for carcinogenicity, depending on type of extract (i.e., undiluted air-refined asphalts, undiluted steam-refined asphalts, extracts of steam-refined, air-refined asphalts and pooled mixtures of steam- and air-refined asphalts).

The characterization of risk to human health involves the consideration of exposure scenarios that are considered to present the highest exposures of the general population to asphalts. This includes transient inhalation exposure of bystanders during paving operations, short-term dermal exposure from the use of coating products, long-term inhalation exposure from living in the vicinity of asphalt plants and refineries, and long-term oral exposure to house dust that contains asphalt components as derived from driveway sealant.

For this scenario, the general population may be exposed to fugitive releases (i.e., volatile components of asphalts) that may occur during asphalt processing, handling and storage at asphalt plants and refineries. Exposures to component substances that are known to be present in asphalt in the initial stages of processing (benzene and PAHs), and that are released during asphalt production, were estimated using measured emissions data combined with dispersion modelling. Conservative assumptions were used in order to characterize risk for potential long term exposure to asphalt volatiles due to living in the vicinity of asphalt plants or refineries.

An estimate of the carcinogenic potency for benzene (TC₀₅), previously developed by the Government of Canada (Environment Canada, Health Canada 1993), was used to calculate MOEs associated with long term benzene exposure due to asphalt emissions at facilities that produce, handle and store asphalts. The resulting MOEs for this exposure scenario are presented in Table 9-2.

The MOEs (291 000 and 803 000) for potential long-term inhalation exposure to benzene emissions from asphalt at asphalt plants are considered adequate to address uncertainties related to the health effects and exposure databases. The air concentrations attributed to asphalt-derived benzene at 230 metres from the facility are significantly below the background level of benzene found in ambient air in Canada (0.32-0.84 μg/m³) (NAPS 2012).

Releases of PAHs to air are also associated with the production and refinement of asphalts. For the purposes of characterizing risk for potential long-term inhalation exposure to asphalt-derived PAHs, the PAH concentrations determined at 230 metres (the distance associated with the highest levels of exposure as determined by dispersion modelling) were converted into B[a]P equivalents using potency equivalence factors (PEFs) as developed by Nisbet and LaGoy (1992) (see Table Appendix H).

Based on measured emissions quantity data from the US EPA (2000) for asphalt plants, PAH concentrations in air at 230 metres were determined and their sum potency was 0.0105 ng/m³ of B[a]P equivalents (see Table 9-3).

An estimation of potential long-term exposure to PAHs at 230 m from asphalt production, handling and storage was therefore determined to be 0.0105 ng/m³ B[a]P equivalents. This value is lower, by over an order of magnitude, than the average Canadian background concentration of B[a]P in ambient air (0.14 ng/m³) (NAPS 2012). Compared with the TD₀₅for B[a]P of 1.57 mg/m³ (Environment Canada, Health Canada 1994), the resulting MOE is 149 500 000 for long-term exposure in the vicinity of asphalt plants. This margin is considered adequate to address uncertainties in the exposure and health effects databases.

Long-term oral exposure to asphalt-derived PAHs found in house dust

For the purpose of characterizing risk for long-term exposure to asphalt-derived PAHs found in house dust (that are assumed to migrate indoors over time from the wearing of asphalt-based driveway/parking lot sealants), the concentration of each of 16 PAH species found in 10 samples of ground floor apartment dust with associated asphalt-based parking lots was considered (Mahler et al. 2010). It was conservatively assumed that these levels of PAHs were derived solely from asphalt surfaces (i.e., ignoring non-asphalt sources that might contribute to PAHs in house dust). The average PAH level found in the dust samples for each of the 16 PAHs was converted into a B[a]P equivalent using the Nisbet and LaGoy (1992) PEFs (Appendix H). The combined potency across the 16 PAH species resulted in a total average B[a]P equivalents in dust of 3.18 μg/g (see Table F-5 in Appendix F for more details). Therefore, exposure to house dust was considered to carry an associated oral exposure to B[a]P of 3.18 μg per gram of dust. For the purposes of conducting a combined dust and soil exposure risk characterization, this concentration of B[a]P was considered to exist in soil, and to be 100% bioavailable. Conservatism is built in from assuming 100% bioavailability for every exposure and by attributing all PAHs in the dust to asphalts.

Average combined soil and dust ingestion rates were adapted from the work of Wilson (2013) for each age group. A daily exposure estimate to B[a]P equivalents (i.e., representing asphalt-derived PAHs) was derived for each age group based on the ingestion of soil and indoor dust, and assuming that the soil and dust contains 3.18 μg/g of B[a]P. Soil and dust and B[a]P intakes for each age group are presented in Table 9-4

The average daily dose of asphalt-derived PAHs (i.e., in B[a]P equivalents) over a lifetime was determined to be 0.00135 µg/kg-bw. Young children ingest the greatest mass of soil and dust due to touching surfaces that accumulate dust and their extensive hand-to-mouth action (Van Metre 2013).

In characterizing risk for a lifetime of exposure, US EPA age-dependent adjustment factors (US EPA 2011c) were adjusted to the Health Canada age bins and applied to each age group (see Appendix F). These factors were used to account for the sensitivity of each life stage; an MOE for long term exposure was then determined (see Appendix F). The point of departure for determining a lifetime MOE from a lifetime of daily exposure to soil and dust containing asphalt-derived PAHs was the lower limit of a one-sided 95% confidence interval (BMDL₁₀) for B[a]P. This was calculated by Health Canada to be 0.545 mg/kg-bw/day (Health Canada 2015). The daily B[a]P intakes for each age group were determined, were compared with this endpoint, and the MOE for each age group was adjusted based on age sensitivity using the adjustment factors fit to Health Canada’s age bins. The resulting lifetime MOE is 99 150, considering a 70 year lifespan (equaling a sum total of 71 years of exposure), and factors in age group sensitivities and differences in daily exposure per age group. This MOE is considered adequate to address uncertainties in the exposure and health effects databases.

Given the possibility of a higher 'one-time' oral exposure to soil for infants and toddlers, the short-term risk from a potential higher oral exposure to asphalt-derived PAHs from the ingestion of soil was considered for toddlers. Based on the considerations outlined above, ingestion of 1 gram of soil for a toddler would result in an oral exposure to 3.18 μg B[a]P equivalents (0.21 µg B[a]P/kg-bw). Given that the ingested dose is low (on the order of low parts per billion relative to body weight), that PAHs are only partially bioavailable when adsorbed to soil, the short-term nature of the exposure, and the limited health endpoints available for characterizing short-term oral exposures to PAHs, risk to human health is considered to be low.

Because asphalt and oxidized asphalt are UVCBs, their specific compositions are only broadly defined and vary from batch to batch. The proportion of component substances can change depending on operating conditions, feedstocks and processing units; however, given the nature by which asphalts are produced, volatile and light molecular weight substances such as benzene and 2-3 ring PAHs are expected to be consistently present only at very low levels.

Also, due to limited detailed information on the composition of asphalts, characterization of exposure and risk focussed on the known component substances that pose the highest hazard to human health, as well as on the component substance with the potential for highest short-term inhalation exposure (i.e., naphthalene). Additionally, dermal exposure to whole asphalts was assessed. However, exposure to other component substances of asphalts may occur that were not considered in the inhalation and oral ingestion scenarios, and these substances may have associated health effects. The margins developed for the high exposure and high hazard substances are considered to account for potential exposure to other less well-defined component substances of asphalts.

There is uncertainty in the level of B[a]P equivalents contained in home dust and soil, as the concentration is based on ten dust samples from ground floor apartments in Texas. Additional PAH compositional analysis of dust and soil from Canadian homes would result in a better understanding of the range of PAH concentrations found here, and could be assessed across a variety of housing types and ages. Also, refining the percent attribution of PAHs that are found in house dust (from 100%) that originate from asphalts would result in more precise estimates of contribution of asphalts to PAHs in dust, but assuming 100% attribution is conservative for the purpose of assessing risk to human health.

Considering all available lines of evidence presented above including studies of releases from asphalt formulations used for paving and roofing, there is low risk of harm to organisms or the broader integrity of the environment from these substances. It is concluded that asphalt and oxidized asphalt (CAS RNs 8052-42-4 and 64742-93-4) do not meet the criteria under paragraphs 64(a) or (b) of CEPA as they are not entering the environment in quantities or concentrations or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity or that constitute or may constitute a danger to the environment on which life depends.

The general population may be exposed to asphalts through product use, or may be exposed to minor components of asphalts that are found in soil and house dust, or that are released during professional asphalt paving, roofing or transportation activities, or by asphalt facilities. However, exposure to asphalts and to minor high-hazard components of asphalts are low and therefore risk is considered to be low.

Based on the information presented in this screening assessment, it is concluded that asphalt and oxidized asphalt (CAS RNs 8052-42-4 and 64742-93-4) do not meet the criteria under paragraph 64(c) of CEPA as they are not entering the environment in a quantity or concentration or under conditions that constitute or may constitute a danger in Canada to human life or health.

It is concluded that asphalt and oxidized asphalt (CAS RNs 8052-42-4 and 64742-93-4) do not meet any of the criteria set out in section 64 of CEPA.

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MOE_{ADJ age group} = (BMDL₁₀/Dose_{age group}) × (1/ADAF_{age group})

MOE_{ADJ lifetime} = 1 / Σ[1/MOE_{ADJ age group} × Averaging Time_{age group}]
MOE_{ADJ lifetime} = 1 / [(1/MOE_{ADJ 0 to 0.5yrs}× 0.5/71) + (1/MOE_{ADJ 0.5 to 4yrs} × 4.5/71) + (1/MOE_{ADJ 5 to 11yrs} × 7/71) + (1/MOE_{ADJ 12 to 19yrs} × 8/71) + (1/MOE_{ADJ 20 to 59yrs} × 40/71) + (1/MOE_{ADJ 60+yrs} × 11/71)]
MOE_{ADJ lifetime} = 1 / [(1/3488 × 0.5/71) + (1/9961 × 4.5/71) + (1/35119 × 7/71) + (1/1458019 × 8/71) + (1/3056128 × 40/71) + (1/3181132 × 11/71)]
MOE_{ADJ lifetime} = 99 150