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1 APPENDIX 3-VI SELECTION OF SCREENING THRESHOLDS AND TOXICITY REFERENCE VALUES

2 Cenovus FCCL Ltd. - i - Appendix 3-VI TABLE OF CONTENTS SECTION PAGE 1 INTRODUCTION SELECTION OF SCREENING VALUES ACUTE INHALATION HUMAN HEALTH THRESHOLDS CHRONIC INHALATION HUMAN HEALTH THRESHOLDS SCREENING VALUES USED FOR IDENTIFYING CHEMICALS OF POTENTIAL CONCERN FOR THE DEPOSITIONAL PATHWAY Toxic Potential Ranking HUMAN HEALTH TOXICITY ASSESSMENT SUMMARY OF CHEMICALS OF POTENTIAL CONCERN Short-Term Inhalation Risk Assessment Long-Term Inhalation Risk Assessment Multimedia Risk Assessment CHEMICAL CLASSIFICATION Long-Term Inhalation Risk Assessment Multimedia Risk Assessment TOXICITY REFERENCE VALUES Long-Term Inhalation Risk Assessment Multimedia Risk Assessment WILDLIFE TOXICITY ASSESSMENT TOXICITY REFERENCE VALUES Toxicity Reference Values Derivation Methods Summary of Ecological Soil Screening Level (Eco-SSL) Derivations Alternate Literature-Based Toxicity Reference Values Data Processing Results REFERENCES PERSONAL COMMUNICATIONS ABBREVIATIONS GLOSSARY... 70

3 Cenovus FCCL Ltd. - ii - Appendix 3-VI LIST OF TABLES Table 1 Acute Inhalation 1-Hour Health-Based Thresholds... 6 Table 2 Acute Inhalation 24-Hour Health-Based Thresholds Table 3 Chronic Air Screening Levels and Guidelines Used in the Chemical Screening Process Table 4 Oral Reference Doses Used in the Depositional Screening for the Multimedia Risk Assessment Table 5 Oral Slope Factors Used in the Depositional Screening for the Multimedia Risk Assessment Table 6 Carcinogenicity Classification of Chemicals of Potential Concern for the Long-Term Inhalation Risk Assessment Table 7 Carcinogenicity Classification of Chemicals of Potential Concern for Multimedia Risk Assessment Table 8 Inhalation Reference Concentrations for Non-Carcinogenic Chemicals of Potential Concern Evaluated in the Long-Term Air Quality Risk Assessment Table 9 Inhalation Unit Risks for Carcinogenic Chemicals of Potential Concern Evaluated in the Long-Term Air Quality Risk Assessment Table 10 Oral Reference Doses for Non-Carcinogenic Chemicals of Potential Concern Evaluated in the Multimedia Risk Assessment Table 11 Oral Slope Factors for Carcinogenic Chemicals of Potential Concern Evaluated in the Multimedia Risk Assessment Table 12 Inhalation Reference Concentrations for Non-Carcinogenic Chemicals of Potential Concern Evaluated in the Multimedia Risk Assessment Table 13 Inhalation Unit Risks for Carcinogenic Chemicals of Potential Concern Evaluated in the Multimedia Risk Assessment Table 14 Toxicity Data Used to Calculate Toxicity Reference Values for Mammals Table 15 Toxicity Data Used to Calculate Toxicity Reference Values for Birds... 54

4 Cenovus FCCL Ltd Appendix 3-VI 1 INTRODUCTION This appendix forms part of the Environmental Health Risk Assessment being completed as part of the overall Environmental Impact Assessment (EIA) for the Cenovus FCCL Ltd. (Cenovus) Christina Lake Thermal Project Phase H and Eastern Expansion (the Project). For the Human Health Risk Assessment, the screening values used in the acute and chronic inhalation assessments and multimedia assessment are identified in this appendix in addition to the toxicity assessment (i.e., development of Toxicity Reference Values [TRVs]) for the Chemicals of Potential Concern (COPCs) retained following the inhalation and multimedia screening process. For the Wildlife Health Risk Assessment, the screening values for the multimedia assessment are identified in this appendix in addition to the toxicity assessment (i.e., development of TRVs) for the COPCs retained following the multimedia screening process.

5 Cenovus FCCL Ltd Appendix 3-VI 2 SELECTION OF SCREENING VALUES 2.1 ACUTE INHALATION HUMAN HEALTH THRESHOLDS As part of the short-term human health inhalation risk assessment, predicted peak 1- hour and 24-hour concentrations of Volatile Organic Compounds (VOCs), acid gases, metals and Polycyclic Aromatic Hydrocarbons (PAHs) were compared to the most conservative of the available acute health-based thresholds from the following agencies: Alberta Environment (AENV 2011); Agency of Toxic Substances and Disease Registry (ATSDR 2012); California Environmental Protection Agency Office of Environmental Health Hazard Assessment (Cal EPA OEHHA 2012); World Health Organization (WHO 2000, 2006); Ontario Ministry of the Environment (OMoE 2012a,b); and Texas Commission on Environmental Quality (TCEQ 2012). The most conservative of the available 1-hour or 24-hour health-based screening levels for a given chemical was used. Screening thresholds from the Texas Commission on Environmental Quality (TCEQ) were only used in the absence of available health-based thresholds from the agencies listed above. For substances for which health-based thresholds were only available from the Ontario Ministry of the Environment (OMoE) and the TCEQ, and supporting documentation was not available, the lower of the two values was used in the assessment. In addition, guidelines for carbon monoxide, nitrogen dioxide, sulphur dioxide and particulate matter were also available from the Canadian Council of Ministers of the Environment (CCME 1999, 2012). Alberta Environment Alberta Environment (2011) has adopted several of their ambient air quality objectives from other jurisdictions (e.g., Ontario, Texas, California). In some cases, the original source has updated their value(s); however, Alberta has not yet reviewed and adopted the updated values. Regardless of this, the air quality objective reported in AENV (2011) is shown in the screening table. Supporting documentation for the Alberta Ambient Air Quality Objectives (AAAQO) was limited and not available for all of the air quality objectives.

6 Cenovus FCCL Ltd Appendix 3-VI Agency for Toxic Substances and Disease Registry The Agency for Toxic Substances and Disease Registry (ATSDR) derives Minimal Risk Levels (MRLs) for non-carcinogenic health effects. The MRLs are based on reliable and sufficient data that identify the target organ(s) of effect or the most sensitive health effect(s) for a specific duration for a given route of exposure to the substance. The ATSDR generally uses the No Observed Adverse Effect Level/Uncertainty Factor (NOAEL/UF) approach to derive MRLs. Physiologicallybased pharmacokinetic (PBPK) modelling and benchmark dose (BMD) modelling have also been used in deriving MRLs. The MRLs are set below levels that may cause adverse health effects in sensitive subpopulations of people. The acute MRLs are derived for exposure durations of 1 to 14 days. The ATSDR MRLs are generally based on the most sensitive endpoint considered to be of relevance to humans. However, as MRLs are often based on animal studies (because of lack of relevant human studies), there is some degree of uncertainty associated with MRLs. Generally, precise toxicological information is lacking for people who might be most sensitive (e.g., infants, elderly and nutritionally or immunologically compromised). As a result of this uncertainty, ATSDR assumes that humans are more sensitive than animals to the effects of hazardous substances and that certain people may be particularly sensitive, and applies a protective approach (i.e., application of margins of safety) to address uncertainty. Supporting documentation was available for the MRLs used in this assessment. California Environmental Protection Agency The California Office of Environmental Health Hazard Assessment (OEHHA) Reference Exposure Levels (RELs) are concentrations of a chemical at or below which adverse non-carcinogenic health effects are not anticipated to occur for a specified exposure duration. The RELs are used in risk assessments to evaluate the potential for adverse non-carcinogenic public health effects from facility emissions or similar localized sources in the Air Toxics Hot Spots Program, and from widespread exposures in the Toxic Air Contaminants program. The REL is an exposure at or below which adverse non-carcinogenic health effects are not expected to occur in a human population, including sensitive subgroups (e.g., infants and children). Supporting documentation was available for most of the RELs. World Health Organization The World Health Organization (WHO) has produced air quality guidelines to provide a basis for protecting public health from adverse effects of air pollution. The guidelines are intended to provide background information and guidance to governments in making risk management decisions, particularly in setting standards, but their use is not restricted to this. They also provide information for those who

7 Cenovus FCCL Ltd Appendix 3-VI deal with air pollution. The guidelines may be used in planning processes and various kinds of management decisions at a community or regional level. Supporting documentation was provided for all WHO guidelines. Ontario Ministry of Environment The OMoE has developed Ambient Air Quality Criteria (AAQC), which may be used in environmental assessments to assess air quality. An AAQC is a desirable concentration of a contaminant in air, based on protection against adverse effects on health or the environment. The term ambient is used to reflect general air quality independent of location or source of a contaminant. The AAQCs are set with different averaging times (e.g., 24-hour, 1-hour and 10 minutes) appropriate for the effect that they are intended to protect against. The effects considered may be health, odour, vegetation, soiling, visibility, corrosion or other effects. The OMoE has also derived air quality standards used to assess emissions from non-mobile sources of air pollution in Ontario. The Ontario air quality standards are generally derived from ambient air quality criteria, and are set at levels protective of the natural environment and sensitive populations (e.g., children, the elderly). The OMoE considers available toxicological information and supporting environmental information to establish effects-based air standards based on the limiting or critical effect(s) (health or environmental considerations) of that chemical. Texas Commission on Environmental Quality Where air quality thresholds were not available from all other jurisdictions, the criteria derived by TCEQ were used. The TCEQ has developed acute (1-hour) Effects Screening Levels (ESLs) that are used in the air permitting process to evaluate effects predicted by air dispersion modelling. The ESLs are used to evaluate the potential for effects to occur as a result of exposure to concentrations of constituents in the air. The ESLs are based on health effects, the potential for odours to be a nuisance, effects on vegetation, and corrosive effects. The ESLs are not ambient air standards. If predicted airborne levels of a constituent do not exceed the screening level, adverse health or welfare effects are not expected. If predicted ambient levels of constituents in air exceed the screening levels, it does not necessarily indicate a problem but rather triggers a more detailed review. The TCEQ has developed a guidance document titled Guidelines to Develop Effects Screening Levels, Reference Values and Unit Risk Factors (TCEQ 2006) that outlines the approach and methods used to derive the acute and chronic ESLs. Texas does not provide supporting documents for all compounds for which they have screening values. Accordingly, the TCEQ ESLs were not selected for use in the screening process unless adequate supporting documentation was available.

8 Cenovus FCCL Ltd Appendix 3-VI Summary of Screening Thresholds The available acute inhalation 1-hour and 24-hour health-based thresholds and the basis of these thresholds are presented in Tables 1 and 2, respectively. Predicted 1-hour and 24-hour peak concentrations in air from the Application Case were compared to the most conservative of the 1-hour and 24-hour acute thresholds, respectively (Appendix 3-VIII, Table 3 and Appendix 3-VIII, Table 4, respectively). A parameter was retained for further evaluation if the predicted Application Case peak concentration (i.e., maximum from all receptor locations) was greater than the threshold. A parameter that was retained for further assessment was classified as a COPC and was evaluated for all receptor locations.

9 Cenovus FCCL Ltd Appendix 3-VI Table 1 Acute Inhalation 1-Hour Health-Based Thresholds Acid Gases Parameter Alberta (a) CCME NAAQO (b)(j) OMoE (c) (d) Cal EPA ATSDR Desirable Acceptable Tolerable Ambient Air Quality Objectives OEHHA (e) WHO(f)(g) and Other (i) (h) TCEQ Toxicological Endpoints and Derivations Carbon disulphide TCEQ: Threshold based on health (supporting documentation not available). Alberta: Based on the oxygen carrying capacity of the blood (supporting documentation not available). Carbon monoxide 15,000 15,000 35,000-36,200-23,000 30,000 - CCME NAAQO: Supporting documentation not available. OMoE: Threshold based on health endpoint (supporting document not available). Cal OEHHA: Threshold based on effects of angina in people with known cardiovascular diseases that are exercising heavily. WHO: Threshold based on a maximum concentration of 2.5% carboxyhaemoglobin (COHb - carbon monoxide bound to blood haemoglobin) to protect non-smoking, middle-aged and elderly population groups with coronary artery disease, and to protect fetuses of non-smoking pregnant women. Carbonyl sulphide ,330 TCEQ: Threshold based on health effects (interim) (supporting documentation not available). Hydrogen sulphide Cal OEHHA: Threshold based on headaches and nausea in response to odour. Nitrogen dioxide Sulphur dioxide PM Alberta: Threshold based on respiratory effects (supporting documentation available). CCME: Supporting documentation not available. OMoE: Threshold based on health endpoint (supporting document not available). Cal OEHHA: Threshold based on increased airway reactivity in asthmatics. WHO: Threshold based on studies of bronchial responsiveness among asthmatics. Alberta: Threshold based on pulmonary function (supporting documentation available). CCME: Supporting documentation not available. OMoE: Threshold based on health and vegetation endpoints (supporting documentation not available). Cal OEHHA: Threshold based on impairment of airway function (bronchoconstriction) especially in asthmatics. Alberta: Threshold was derived from the statistical equivalent of the 24-hour Canada Wide Standard. Threshold is used in the monitoring and reporting of the Ambient Air Quality Index. PM Metals Arsenic Alberta: Threshold adopted from TCEQ (2001) which was based on an occupational exposure limit of 0.01 mg/m 3, divided by a safety factor of 100. Since then, TCEQ (2012) has updated its acute threshold to 3 μg/m 3 (HQ=0.3) which is based on maternal toxicity as rales (crackling noises in lungs during inhalation) in rats. Cal OEHHA: Threshold based on decreased fetal weight in mice following maternal inhalation of As 2O 3 during gestation period. A LOAEL of 0.26 mg/m 3 and an uncertainty factor of 1,000 (10 for no NOAEL value, 10 for interspecies differences between mice and humans, 10 for human interindividual differences) were used. Barium TCEQ: Threshold based on health (interim, supporting documentation not available), for barium and compounds. Beryllium TCEQ: Threshold based on health (interim, supporting documentation not available); for beryllium as a particulate. Cadmium TCEQ: Threshold based on health (interim, supporting documentation not available); for cadmium and compounds. Alberta: Adopted from TCEQ (supporting documentation not available). TCEQ: Threshold for Cr 3+ based on increased acid phosphatase activity in lavage fluid and increased acid Chromium phosphotase and β-glucuronidase activity in lung tissue (precursors to adverse effects) in hamsters. The NOAEL was 77 mg/m 3 and adjusted to mg/m 3 for a human equivalent concentration. An uncertainty factor of 300 (3 for interspecies differences, 10 for intraspecies differences and 10 for incomplete database) was used for a threshold of 36 μg/m 3 (HQ=1) or 3.6 μg/m 3 (HQ=0.3). Cobalt TCEQ: Threshold based on health (interim, supporting documentation not available); for cobalt and inorganic compounds. Copper Cal OEHHA: Threshold based on respiratory system effects in humans. Lead (9) Alberta: Adopted from TCEQ (which reference the US EPA National Ambient Air Quality Standards). Other: the US National Ambient Air Quality Standards have since been updated and the standard of 0.15 μg/m 3 is health-based threshold based on rolling 3-month average. Manganese Alberta: Adopted from TCEQ. TCEQ: Threshold based on health (interim, supporting documentation not available), as dust and inorganic compounds.

10 Cenovus FCCL Ltd Appendix 3-VI Table 1 Acute Inhalation 1-Hour Health-Based Thresholds (continued) Parameter Alberta (a) CCME NAAQO (b)(j) OMoE (c) (d) Cal EPA ATSDR Desirable Acceptable Tolerable Ambient Air Quality Objectives OEHHA (e) WHO(f)(g) and Other (i) (h) TCEQ Mercury Toxicological Endpoints and Derivations Cal OEHHA: Threshold based on CNS disturbances in rat offspring. Maternal rats were exposed to metallic Hg vapour (1.8 mg/m 3 ) for 3 hours/day during gestation. The offspring displayed significant dose-dependent deficits in behaviour 3 to7 months after birth compared to controls. An uncertainty factor of 3000 (10 for using LOAEL for moderate to severe effects in the absence of a NOAEL, 3 for interspecies toxicokinetic differences, 10 for interspecies toxicodynamic differences, 3 for individual variability, and 3 for intraspecies differences in age differences) was used. Molybdenum TCEQ: Threshold based on health (interim, supporting documentation not available). Nickel Alberta: Threshold adopted from Cal OEHHA (supporting documentation available) however the Cal OEHHA has since been updated. The previous Cal OEHHA threshold was based on a LOAEL of 67 μg/m 3 for 30 minutes based on a study of seven metal plating workers with occupational asthma. The LOAEL was extrapolated to a 1 hour concentration of 33 μg/m 3 and an uncertainty factor of 6 (6 for using a LOAEL) was applied. Cal OEHHA: Threshold based on depressed antibody response in mice, exposed for two hours to nickel and nickel compounds. The extrapolated one hour concentration was 233 μg/m 3 and an uncertainty factor of 1,000 (3 for BMR uncertainty, 10 for interspecies differences, and 30 for intraspecies differences) was applied. Selenium TCEQ: Threshold based on health (interim, supporting documentation not available), as selenium and compounds. Vanadium Cal OEHHA: Threshold based on respiratory system and eyes effect in humans, as vanadium pentoxide. Zinc TCEQ: Threshold based on health (interim, supporting documentation not available), for zinc and compounds. Polycyclic Aromatic Hydrocarbons Acenaphthene TCEQ: Threshold based on health effects (interim, supporting documentation not available). Acenaphthylene TCEQ: Threshold based on health effects (interim, supporting documentation not available). Anthracene TCEQ: Threshold based on health effects (interim, supporting documentation not available). Benz(a)anthracene TCEQ: Threshold based on health effects (interim, supporting documentation not available). Benzo(a)pyrene TCEQ: Threshold based on health effects and as benzo(a)pyrene in PM 10 (supporting documentation not available). Benzo(b)fluoranthene TCEQ: Threshold based on health effects (interim, supporting documentation not available). Benzo(g,h,i)perylene TCEQ: Threshold based on health effects (interim, supporting documentation not available). Benzo(k)fluoranthene TCEQ: Threshold based on health effects (interim, supporting documentation not available). Chrysene TCEQ: Threshold based on health effects (interim, supporting documentation not available). Dibenzo(a,h)anthracene TCEQ: Threshold based on health effects (interim, supporting documentation not available); as anthracene. 7,12-Dimethylbenz(a)anthracene TCEQ: Threshold based on health effects (interim) (supporting documentation not available). Fluoranthene TCEQ: Threshold based on health effects (interim, supporting documentation not available). Fluorene TCEQ: Threshold based on health effects (interim, supporting documentation not available). Indeno(1,2,3-cd)pyrene TCEQ: Threshold based on health effects (interim, supporting documentation not available). 3-Methylcholanthrene TCEQ: Threshold based on health effects (interim) (supporting documentation not available). 2-Methylnaphthalene TCEQ: Threshold based on health effects (interim, supporting documentation not available). Naphthalene (surrogate: 2-methyl naphthalene) As no health-based 1-hour standard was available for naphthalene, the health-based standard for 2-methylnaphthalene was adopted for screening purposes (TCEQ). Phenanthrene TCEQ: Threshold based on health effects (interim, supporting documentation not available). Pyrene TCEQ: Threshold based on health effects (interim, supporting documentation not available). Volatile Organic Compounds C2-C8 Aliphatics (surrogate: cyclohexane) C9-C16 Aliphatics (surrogate: decane) ,400 TCEQ: The threshold for the surrogate, cyclohexane, is based on health effects (interim, supporting documentation not available) ,000 TCEQ: Threshold based on health effects (interim, supporting documentation not available).

11 Cenovus FCCL Ltd Appendix 3-VI Table 1 Acute Inhalation 1-Hour Health-Based Thresholds (continued) Parameter Alberta (a) CCME NAAQO (b)(j) OMoE (c) (d) Cal EPA ATSDR Desirable Acceptable Tolerable Ambient Air Quality Objectives OEHHA (e) WHO(f)(g) and Other (i) (h) TCEQ Acetaldehyde Acrolein (0.003 ppm) Benzene Toxicological Endpoints and Derivations Cal OEHHA: Threshold based on sensory irritation, bronchi, eyes, nose and throat. Sixty-one adult asthmatic human volunteers exposed to acetylaldehyde via inhalation by nebulizer for 2-4 minutes experienced bronchoconstriction, PC 20 > 20% drop in forced expiratory volume in one second (FEV1). LOAEL = 142 mg/m 3. Uncertainties applied include 10 for LOAEL, 1 for interspecies, 1 for intraspecies, and 30 for asthma exacerbation in children and hyperresponsiveness to methacholine for a total of 300. OMoE: Threshold based on irritation following an acute exposure (1 hour) to acrolein. A LOAEL of 137 μg/m 3 was identified and an uncertainty factor of 30 (3 for LOAEL to NOAEL extrapolation and 10 for interspecies variability) wasapplied. ATSDR: Acute inhalation MRL was derived based on a LOAEL of 0.3 ppm for nasal and throat irritation and decreased respiratory rate in volunteers exposed for 1 h. An uncertainty factor of 100 was applied (10 for using a LOAEL and 10 for human variability). The MRL of ppm was converted to µg/m 3 using MW = g/mol. Cal OEHHA: Threshold based on eye irritation in humans in two studies. Two LOAELs of 0.06 ppm (138 µg/m 3 ) and 0.07 ppm (160 µg/m 3 ) were identified and a NOAEL was not observed for both studies. An uncertainty factor of 60 (6 for using LOAEL for mild effects in the absense of a NOAEL and 10 for greater sensitivity in children with asthma) was applied to each of the LOAELs and the average of the two values were taken (2.5 µg/m 3 ). The threshold in ppm was converted to µg/m 3 using MW = g/mol. Alberta: Threshold based on haematological effects and was adopted from TCEQ in TCEQ has since updated its Effects Screening Level; documentation for the Alberta threshold is unavailable. Cal OEHHA: Threshold based on reproductive and developmental toxicity. 1,3-Butadiene TCEQ: Health endpoint for 1,3-butadiene homopolymers (100 μg/m 3 ) (supporting documentation not available). n-butane ,000 TCEQ: The threshold is based on the highest concentration of n-butane exposed to rats (for 6 h/day, 7 d/week for two weeks) in which there was no significant difference noted in body weight, organ weights or feed consumption compared to control animals. The NOAEL identified was 9,2 ppm (21,862 mg/m 3 ) and an uncertainty factor of 100 (10 for intraspecies variability, 3 for interspecies variability and 3 for an incomplete database) was applied to derive the threshold. The threshold is based on a target HQ of 0.3. The threshold in ppm was converted to µg/m 3 using MW = g/mol. Cyclohexane ,400 TCEQ: Threshold based on health effects (interim, supporting documentation not available). Cyclopentane ,400 TCEQ: The threshold is based on health effects (interim, supporting documentation not available). n-decane , ,000 OMoE: Threshold based on health and odour (supporting documentation not available). TCEQ: Threshold based on health effects (interim, supporting documentation not available). Dichlorobenzenes (mixture) (surrogate: 1,4-dichlorobenzene) TCEQ: Threshold for 1,4-dichlorobenzene is based on eye and nose irritation in occupationally-exposed workers. The workers were exposed to 1,4-dichlorobenzene for 8 h/day, 5 d/week continually or intermittently for periods of eight months to 25 years. Eye and nose irritation were reported at a LOAEL of 50 ppm (301 mg/m 3 ) and a NOAEL 15 ppm (90 mg/m 3 ) was identified. An uncertainty factor of 30 (10 for intraspecies difference and 3 for an incomplete database) was applied to derive the threshold. The threshold is based on a target HQ of 0.3. The threshold was converted from ppm to mg/m 3 using a MW = 147 g/mol. 2,3-Dimethylpentane ,500 TCEQ: The threshold is based on health effects (interim, supporting documentation not available). Ethane (surrogate: cyclohexane) ,400 TCEQ: The threshold for the surrogate, cyclohexane, is based on health effects (interim, supporting documentation not available). Ethylbenzene ,000 TCEQ: Threshold based on ototoxicity observed in an inhalation study where rats were exposed to ethylbenzene. The NOAEL was 300 ppm, and the POD HEC was 600 ppm (1,303 mg/m 3 ). A total uncertainty factor of 30 (3 for interspecies differences and 10 for intraspecies differences) was applied to the extrapolated 1-hour concentration (POD ADJ of 600 ppm; HQ=0.3). The threshold was converted from ppm to mg/m 3 using MW = g/mol. Formaldehyde (0.04 ppm) Alberta: Threshold adopted from TCEQ based on human respiratory effects. However, TCEQ (2008) has since updated their threshold to 15 μg/m 3 (HQ=0.3) or 50 μg/m 3 (HQ=1) based on eye and nose irritation in human volunteers. ATSDR: Threshold based on LOAEL of 0.4 ppm (Nasal and eye irritation in humans following 2-hour exposure); uncertainty factors: 3 for use of LOAEL, 3 for human variability. The MRL of 0.04 ppm was converted to 49.1 µg/m 3 using MW = g/mol. Cal OEHHA: Based on mild and moderate eye irritation. 19 non-asthmatic, non-smoking humans exposed to 0.5 to 3.0 ppm (0.6 to 3.7 mg/m 3 ; single exposure per concentration) for 3 hrs experienced mild and moderate eye irritation. LOAEL = 1 ppm and NOAEL = 0.5 ppm. Uncertainty factors of 1 for interspecies, 1 for intraspecies, and 10 for asthma exacerbation in children were applied. The threshold was converted from ppm to mg/m 3 using MW = g/mol. n-heptane ,500 TCEQ: Threshold based on health effects (interim, supporting documentation not available).

12 Cenovus FCCL Ltd Appendix 3-VI Table 1 Acute Inhalation 1-Hour Health-Based Thresholds (continued) Parameter Alberta (a) CCME NAAQO (b)(j) OMoE (c) (d) Cal EPA ATSDR Desirable Acceptable Tolerable Ambient Air Quality Objectives OEHHA (e) WHO(f)(g) and Other (i) (h) TCEQ Hexane (n-hexane) 21, Isobutane ,000 Isopentane (surrogate: n-pentane) ,000 Isopropylbenzene (cumene) (surrogate: n-propylbenzene) Methylcyclohexane (surrogate: cyclohexane) , ,400 Toxicological Endpoints and Derivations Alberta: Derived from the 24-hour REL from Cal OEHHA. The Cal OEHHA threshold was based on peripheral neuropathy in male mice exposed for 1 year. The NOAEL was 352 mg/m 3 (100 ppm) and the NOAEL HEC was 204 mg/m 3 (57.9 ppm). An uncertainty factor of 30 (3 for interspecies differences and 10 for intraspecies differences) was applied to derive a 24-hour REL of 7,000 µg/m 3. Alberta Environment applied an additional factor of 3 to adjust from a chronic to acute threshold. TCEQ: The threshold is based on a NOAEL of 1000 ppm (2,377 mg/m 3 ), which was the highest concentration tested that did not produce any cardiac and pulmonary response in human volunteers in the key study. Human volunteers were exposed to isobutane for 1, 2, or 8 h/day, 5 d/week for two weeks. The NOAEL was adjusted for continuous exposure and thenan uncertainty factor of 30 (10 for intraspecies variability and 3 for an incomplete database) was applied to derive a threshold. The threshold is based on a target HQ of 0.3.and was converted from ppm to mg/m 3 using MW = g/mol. TCEQ: The threshold is based on anoael of 19,872 mg/m 3 (the highest concentration tested that did not produce any clinical, motor activity and neurobehavioral effects observed in rats in the key study). The rats were exposed to n-pentane for 8 h/day for three days. The NOAEL was used as the POD and an uncertainty factor of 100 (3 for interspecies variability, 10 for intraspecies variability and 3 for an incomplete database) was applied to derive the threshold. The threshold is based on a target HQ of 0.3. TCEQ: The health-based threshold for n-propylbenzene was used as a surrogate (supporting documentation not available). TCEQ: The threshold for the surrogate, cyclohexane, is based on health effects (interim, supporting documentation not available). Methylcyclopentane ,600 TCEQ: The threshold is based on health effects (interim, supporting documentation not available). 3-Methylheptane ,500 TCEQ: The threshold is based on health effects (interim, supporting documentation not available). 3-Methylhexane ,070 TCEQ: The threshold is based on health effects (interim, supporting documentation not available). 3-Methylpentane ,500 TCEQ: The threshold is based on health effects (interim, supporting documentation not available). n-nonane ,500 TCEQ: Threshold based on health effects (interim, supporting documentation not available). n-octane ,500 TCEQ: Threshold based on health effects (interim, supporting documentation not available). Pentane (surrogate: n-pentane) ,000 TCEQ: The threshold is based on a NOAEL of 19,872 mg/m 3 (the highest concentration tested that did not produce any clinical, motor activity and neurobehavioral effects observed in rats in the key study). The rats were exposed to n-pentane for 8 h/day for three days. The free-standing NOAEL was used as the POD and an uncertainty factor of 100 (3 for interspecies variability, 10 for intraspecies variability and 3 for an incomplete database) was applied to derive the threshold. The threshold is based on a target HQ of 0.3. Propane (surrogate: cyclohexane) ,400 TCEQ: The threshold for the surrogate, cyclohexane, is based on health effects (interim, supporting documentation not available). Propylene oxide Alberta: Threshold adopted from Oklahoma Department of Environmental Quality (DEQ) (supporting documentation available). The Oklahoma DEQ threshold was derived from the American Conference of Governmental Industrial Hygienist (ACGIH) Threshold Limit Value (TLV) of 48 mg/m 3 and divided by a safety factor of 100. Cal OEHHA: Threshold based on dyspnea (nasal irritation) in mice exposed for 4 hours. The LOAEL was 387 ppm (919 mg/m 3 ) and the extrapolated 1-hour concentration was 774 ppm (1,839 mg/m 3 ). An uncertainty factor of 600 (6 for using a LOAEL, 10 for interspecies variability, and 10 for intraspecies variability) was used to derive the threshold. The threshold was converted from ppm to mg/m 3 using MW = g/mol. Toluene 1, ,000-15,000 Alberta: Threshold adopted from TCEQ (2003, supporting documentation available). The TCEQ (2003) threshold was based on the threshold limit value time weight average (TLV-TWA) of 188 mg/m 3 (50 ppm) established by the American Conference of Governmental Industrial Hygienists (ACGIH) as an occupational air standard. A safety factor of 100 was applied. Since then, TCEQ (2008) has updated their 1-hour threshold to 4,500 μg/m 3 (HQ=0.3) or 15,000 μg/m 3 (HQ=1) which is based on eye and nose irritation, increased occurrence of headaches, dizziness and intoxication in human male volunteers. The LOAEL was 377 mg/m 3 (100 ppm) and the exposure duration was 6h/day for 4 days. The extrapolated 1 hour concentration was 151 mg/m 3 (40 ppm) and an uncertainty factor of 10 (intraspecies differences) was applied. Cal OEHHA: Threshold based on impaired reaction time and symptoms of headaches, dizziness and a feeling of intoxication, and slight eye and nose irritation. Sixteen young, health males exposed to 369 mg/m 3 (98 ppm) for six hrs experienced impaired reaction time and symptoms of headache, dizziness, a feeling of intoxication and slight eye and nose irritation. Cal OEHHA identified a LOAEL = 100 ppm (377 mg/m 3 ) and NOAEL = 40 ppm (151 mg/m 3 ) and the extrapolated 1-hour concentration was 98 ppm (369 mg/m 3 ) calculated from the NOAEL). Uncertainty factors were applied to the extrapolated 1-hour concentration for intraspecies variability (10) for a total of 10. The threshold was converted from ppm to mg/m 3 using MW = g/mol.

13 Cenovus FCCL Ltd Appendix 3-VI Table 1 Acute Inhalation 1-Hour Health-Based Thresholds (continued) Parameter 2,3,4-Trimethylhexane (surrogate: decane) Alberta (a) CCME NAAQO (b)(j) OMoE (c) (d) Cal EPA ATSDR Desirable Acceptable Tolerable Ambient Air Quality Objectives OEHHA (e) WHO(f)(g) and Other (i) (h) TCEQ Toxicological Endpoints and Derivations ,000 TCEQ: Threshold based on health effects (interim, supporting documentation not available). o-xylene (surrogate: xylenes) m-and p-xylene (surrogate: xylenes) Xylenes (a) (b) (c) (d) (e) (f) (g) (h) Alberta Environment (AENV) Alberta Ambient Air Quality Objectives and Guidelines Summary. April ,680 (2 ppm) 8,680 (2 ppm) 8,680 (2 ppm) 22, See Xylenes. 22, See Xylenes. 22, Canadian Council of Ministers of the Environment (CCME). Canadian National Ambient Air Quality Objectives: Process and Status. In: Canadian Environmental Quality Guidelines (1999). ATSDR: Threshold based on a minimal LOAEL of 217 μg/m 3 (50 ppm) for mild objective and subjective respiratory effects and subjective neurological effects in subjects exposed to m-xylene vapour for 2 hours (uncertainty factor of 30). The MRL of 2 ppm was converted to µg/m 3 using MW = g/mol. Cal OEHHA: Threshold based on nervous system, respiratory system, and eye effects in humans. Ontario Ministry of the Environment (OMoE). 2012a. Ontario's Ambient Air Quality Criteria. Standards Development Branch, OMoE. (April 2012) Agency of Toxic Substances and Disease Registry (ATSDR) Minimum Risk Levels (MRLs) and supporting toxicological profiles (February 2012) ( California Office of Environmental Health Hazard Assessment (Cal EPA OEHHA) Toxicity Criteria Database. Chemical-specific inhalation unit risks used to derive carcinogenic thresholds, ( World Health Organization (WHO) WHO Air quality guidelines for particulate matter, ozone, nitrogen dioxide and sulphur dioxide. Global update Summary of risk assessment. World Health Organization (WHO) Air Quality Guidelines for Europe. Second Edition. WHO Regional Publications, European Series, No. 91. Texas Commission on Environmental Quality (TCEQ) Interoffice memorandum, Effects Screening Levels (March 2012). These values were only provided when values for no other jurisdictions were available. The screening levels derived by TCEQ are based on an HQ=0.3 for noncarcinogens, and an ILCR of one in 100,000 cancer risk for carcinogens. (i) US EPA (United States Environmental Protection Agency). 2008a. National Ambient Air Quality Standard for Lead; last updated October 1, (j) CCME Guidance Document on Achievement Determination: Canadian Ambient Air Quality Standards for Fine Particulate Matter and Ozone. PN CCME, October European Commission Council Directive 1999/30/EC of 22 april 1999 Relating to Limit Values for Sulphur Dioxide, Nitrogen Dioxide and Oxides of Nitrogen, Particulate Matter and Lead in Ambient air. (June, 1999). ( Health Canada Health-Based Tolerable Daily Intakes/Concentrations and Tumorigenic Doses/Concentrations for Priority Substances. Health Canada. ISBN: Accessed January ( Note: Shaded and bold acute thresholds were used in the risk assessment. See Section 2.1 for a discussion on the hierarchy for selecting the acute thresholds. All values are in µg/m 3, unless otherwise noted. To convert from ppm to mg/m 3, the following formula was used: (MW [g/mol] x ppm) / and divided by 1000 to convert from mg/m 3 to µg/m 3. CCME = Canadian Council of Ministers of the Environment; NAAQO = National Ambient Air Quality Objectives; OMoE = Ontario Ministry of Environment; ATSDR: Agency of Toxic Substances and Disease Registry; Cal EPA OEHHA = California Environmental Protection Agency, Office of Environmental Health Hazard Assessment; WHO = World Health Organization; TCEQ = Texas Commission on Environmental Quality; ppm = parts per million; LOAEL/LOEC = Lowest Observable Adverse Effect Level/Lowest Observable Effect Concentration; NOAEL/NOEC = No Observable Adverse Effect Level/No Observable Effect Concentration; MRL = Minimal Risk Level; PAH = Polycyclic Aromatic Hydrocarbons; HEC = Human Equivalent Concentration; POD = Point of Departure; CNS = Central nervous system; - = Value not available.

14 Cenovus FCCL Ltd Appendix 3-VI Table 2 Acute Inhalation 24-Hour Health-Based Thresholds Acid Gases Parameter Alberta (a) Ambient Air Quality Objectives CCME NAAQO (b,c) OMoE (d,e) ATSDR (f) WHO (g,h) Toxicological Endpoints and Derivations Desirable Acceptable Tolerable Carbon disulphide Carbon monoxide 6,000 [8 hour] 6,000 [8 hour] 15,000 [8 hour] 20,000 [8 hour] 15,700 [8 hour] - 10,000 [8 hour] WHO: Threshold based on the LOAEC in occupational exposure to be around 10 mg/m 3, which is equivalent to 1 mg/m 3 in the general population. A safety factor of 10 was selected to take the variability in susceptibility of the general population into account. Alberta: Objective is for 8-hour exposure; supporting information is not available. OMoE: Threshold is based on a health endpoint, and 8 hours of exposure, but supporting documentation is not available. WHO: Threshold is a time-weighted average 8 hour exposure determined so that the carboxyhemoglobin (COHb) level of 2.5% is not exceeded (threshold for human health effect). Carbonyl sulphide Hydrogen sulphide OMoE: Threshold based on nasal lesions in rats (supporting documentation available). Rats were exposed to hydrogen sulphide for 10 weeks and the NOAEL was 13.8 mg/m 3. The NOAEL was adjusted for continuous exposure and the NOAEL HEC was 0.64 mg/m 3. An uncertainty factor of 100 (10 to protect sensitive individuals, 3 to adjust from sub-chronic to chronic exposure, and 3 for interspecies conversion) was applied. WHO: Threshold based on the LOAEC of 15 mg/m 3 (eye irritation). An uncertainty factor of 100 is used because of the steep rise in dose-effect curve implied by reports of serious eye damage at 70 mg/m 3. Nitrogen dioxide Sulphur dioxide PM PM CCME: Supporting documentation not available. OMoE: Threshold based on health effects (supporting documentation not available). Alberta: Threshold adopted from European Union (1999), based on human health (supporting documentation is available but derivation for the threshold is unavailable). CCME: Supporting documentation not available. OMoE: Threshold based on health and vegetation endpoints (supporting document not available). WHO: Threshold based childhood respiratory disease and all-age mortality based on a study in Hong Kong (Hedley et al. 2002, as cited in WHO 2006). After a major reduction in sulphur content in fuels over a very short period of time in Hong Kong, an associated substantial reduction in health effects (listed above) was shown. Another study (Wong et al. 2002, as cited in WHO 2005) showed there was no evidence of a concentration threshold within a SO 2 range of 5-40 µg/m 3 in Hong Kong and in London. Burnett et al. (2004) showed there was a significant association with daily mortality in 12 Canadian cities with an average SO 2 concentration of 5 µg/m 3. However, there is still uncertainty as to whether SO 2 is responsible for the observed adverse effects or is a surrogate for fine particles. The WHO selected a threshold of 10 µg/m 3 to take into consideration to account for the following:1. The uncertainty in SO 2 in causality, 2. The practical difficulties in reaching a level that would produce no effects, and 3. The need to provide a greater degree of protection than what was published previously in 2000 (WHO 2000). Alberta and OMoE thresholds are based on the CCME Canadian Wide Standard for particulate matter, which was protective of human health and the environment. The standard of 30 μg/m 3 was an achievement level (by the year 2010) to be based on the 98th percentile ambient measurement annually, averaged over 3 consecutive years. CCME 10 has recently updated the Canadian ambienit air quality standard for PM 2.5, which is protective of human health and the environment, and a value of 27 μg/m 3 is proposed for the year The metric is the 3-year average of the annual 98 th percentile of the daily 24-hour average concentrations. Alberta and OMoE have not yet adopted the recent CCME value. WHO: Based on significant effects on survival from several long-term exposure studies. The PM hour threshold is based on the chronic threshold of 10 μg/m 3 and the application of a factor of 2.5to derive an acute threshold. CCME: reference level, above which there are demonstrated effects on human health and/or the environment. OMoE: interim ambient air quality criterion. WHO: The 24-hour threshold for PM 10 is based on the annual air threshold for PM 2.5. The annual air threshold for PM 2.5 is 10 µg/m 3 and is based on the lowest level at which total, cardiopulmonary and lung cancer mortality have been shown to increase with more than 95% confidence in response to PM 2.5 in a study (Pope et al. 2002, as cited in WHO 2005). The 24-hour threshold is based on a PM 2.5/PM 10 ratio of 0.5 and a factor of 2.5 to convert from an annual air threshold. The ratio of 0.5 is close to that observed in urban areas. Metals Arsenic OMoE: Threshold based on health endpoint (supporting document not available). Barium OMoE: Threshold based on health endpoint (supporting document not available), for total water soluble barium compounds. Beryllium OMoE: Threshold based on health endpoint (supporting document not available), for beryllium and compounds. Cadmium OMoE: Threshold based on health endpoint (supporting document available). The threshold is based on kidney damage derived by the European Commission based on an occupational LOAEL of 100 μg/m 3 -years and extrapolated for continuous exposure (270 ng/m 3 ). An uncertainty factor of 50 (5 for LOAEL to NOAEL extrapolation and 10 for interindividual variability) was applied to result in an annual threshold of 5 ng/m 3. The OMoE used a factor of 5 to convert from annual thresholds to a 24-hour threshold. ATSDR: Threshold based on a LOAEL of mg/m 3 for respiratory effects in rats exposed to cadmium oxide for 6.2 hours/day, 5 days/week for 2 weeks and an uncertainty factor of 300 (3 for extrapolating from animals to humans and 10 for human variability). Chromium OMoE: Threshold (for Cr(0), Cr(II) and Cr(III)) based on respiratory effects associated with exposure to Cr(III). It is based on a BMCL 10 value of 3.45 mg/m 3 sub-chronic inhalation exposure study (rats) and an uncertainty factor (300). Cobalt OMoE: Threshold based on health endpoint (supporting document not available).

15 Cenovus FCCL Ltd Appendix 3-VI Table 2 Acute Inhalation 24-Hour Health-Based Thresholds (continued) Parameter Alberta (a) Ambient Air Quality Objectives CCME NAAQO (b,c) OMoE (d,e) ATSDR (f) WHO (g,h) Toxicological Endpoints and Derivations Desirable Acceptable Tolerable Copper OMoE: Threshold based on health endpoint (supporting document not available). Lead OMoE: Threshold based on health endpoint (supporting document not available), for lead and compounds. Manganese OMoE: Threshold for Mn as MnO 2 in PM 2.5 and is based on a neurological endpoint (eye-hand coordination) in an occupational study. Workers wore personal monitoring data in which 80% of cases of the exposures exceeded 4.5 hours. Exposure duration averagd 5.3 years. Hand tremor was the most sensitive parameter and a LOAEL of 150 µg/m 3 was derived. The POD was a BMCL 05 of 84 µg/m 3 and adjusted for continuous exposure (30 µg/m 3 ). An uncertainty factor of 300 (10 for human variability, 3 for database limitation, 3 for the sensitivity of the developing nervous system and 3 for subchronic to chronic exposure) was applied to derive the threshold. Mercury OMoE: Threshold based on health endpoint (supporting document not available). Molybdenum OMoE: Threshold based on particulate endpoint (supporting document not available), as a particulate. Nickel OMoE: Threshold for nickel as a metal/parameter in PM10. Based on carcinogenic and non-carcinogenic effects (supporting documentation available). The 24-hour screening value was derived from the annual screening value (0.02 μg/m 3 ) and a conversion factor of 5, which is based on empirical monitoring data, ratios of concentrations observed for different averaging times, and meteorological considerations. Selenium OMoE: Threshold based on health endpoint (supporting document not available). Vanadium OMoE: Threshold based on health endpoint (supporting document not available). ATSDR: Threshold based on a LOAEL of 0.56 mg/m 3 for lung inflammation in rats exposed to vanadium pentoxide for 6 hours/day, 5 days/week for 13 days. The human equivalent concentration of the LOAEL (0.073 mg/m 3 ) was divided by an uncertainty factor of 90 (3 for using minimal LOAEL, 3 for animal to human extrapolation and 10 for human variability). WHO: Threshold based on occupational studies suggesting that the LOAEL of vanadium can be assumed to be 20 μg/m 3, based on chronic upper respiratory tract symptoms. The adverse nature of the observed effects was minimal at 20 μg/m 3 and a susceptible subpopulation was not identified, an uncertainty factor of 20 was applied to derive a threshold of 1 μg/m 3. Zinc OMoE: Threshold based on particulate endpoint (supporting document not available). Polycyclic Aromatic Hydrocarbons Acenaphthene (surrogate: Acenaphthylene) OMoE: Jurisdictional Screening Level. Acenaphthylene OMoE: Jurisdictional Screening Level. Anthracene OMoE: Jurisdictional Screening Level. Benz(a)anthracene OMoE: Jurisdictional Screening Level. Benzo(a)pyrene A chronic threshold from OMoE was conservatively used in the absence of an appropriate 24-hour threshold. The chronic threshold based on a carcinogenic potential endpoint based on the WHO's evaluation of coke-oven worker epidemiological studies from which was derived an inhalation unit risk value of ng/m 3 (BaP as a surrogate for total PAHs) equivalent to µg/m 3 of BaP at a 1 x 10-6 risk level. The chronic threshold was adjusted ( µg/m 3 ) to reflect a 1 x 10-5 incremental lifetime cancer risk. A 24-hour threshold is available from OMoE ( µg/m 3 ); this threshold is based on carcinogenicity associated with exposure to PAH compounds and was derived by applying a conversion factor of 5 to the chronic threshold. The conversion factor is not based on health (i.e., it is based on empirical monitoring data, ratios of concentrations observed for different averaging times, and meteorological considerations) and therefore it was considered conservative and appropriate to use the chronic threshold rather than the 24-hour threshold. Benzo(b)fluoranthene OMoE: Threshold based on Health Canada (2010) 9 PEF of 0.1 relative to BaP. Benzo(g,h,i)perylene OMoE: Jurisdictional Screening Level. Benzo(k)fluoranthene OMoE: Threshold based on Health Canada (2010) 9 PEF of 0.1 relative to BaP. Chrysene OMoE: Threshold based on Health Canada (2010) 9 PEF of 0.01 relative to BaP. Dibenzo(a,h)anthracene OMoE: Threshold based on Health Canada (2010) 9 PEF of 1 relative to BaP. 7,12- Dimethylbenz(a)anthracene OMoE: Based on a PEF of 10 relative to BaP (PEF from Health Canada 2010) (i). Fluoranthene OMoE: Jurisdictional Screening Level. Fluorene (surrogate: Fluoranthene) OMoE: Jurisdictional Screening Level. Indeno(1,2,3-cd)pyrene OMoE: Threshold based on Health Canada (2010) (i) PEF of 0.1 relative to BaP. 3-Methylcholanthrene OMoE: Based on PEF of 1.9 (Cal EPA) relative to BaP. 2-Methylnaphthalene OMoE: Jurisdictional Screening Level. Naphthalene OMoE: Threshold based on health endpoint (supporting document not available). Phenanthrene (surrogate: anthracene) OMoE: Jurisdictional Screening Level. Pyrene OMoE: Jurisdictional Screening Level.

16 Cenovus FCCL Ltd Appendix 3-VI Table 2 Acute Inhalation 24-Hour Health-Based Thresholds (continued) Parameter Volatile Organic Compounds C2-C8 Aliphatics (surrogate: cyclohexane) C9-C16 Aliphatics (surrogate: cyclohexane) Alberta (a) Ambient Air Quality Objectives CCME NAAQO (b,c) OMoE (d,e) ATSDR (f) WHO (g,h) Toxicological Endpoints and Derivations Desirable Acceptable Tolerable OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available) Acetaldehyde Acrolein Benzene ,3-Butadiene (0.009 ppm) 220 (0.1 ppm) - - No 24-hour threshold for the C9-C16 aliphatic surrogate, decane, is available. The 24-hour threshold for C2-C8 aliphatics, cyclohexane, was conservatively used in the risk assessment. OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available). OMoE: Threshold based on health (avoid irritation & possible tissue damage in upper respiratory tract resulting from prolonged exposure) endpoint (supporting document available, but details are not provided). OMoE: Threshold based on olfactory epithelial pathology in a rat study. The NOAEL was 0.6 ppm and the estimated NOAEL HEC was 11 μg/m 3. An uncertainty factor of 30 (3 for interspecies extrapolation and 10 to protect sensitive individuals in humans) was used. OMoE: Threshold based on methods used by US EPA and the European Union that extrapolated occupational exposure concentrations to annual ambient air exposures based on mortality due to acute myeloid leukemia (AML). The 24-h threshold was calculated from the annual threshold (0.45 μg/m 3 ) usiing a conversion factor of 5 (based on empirical monitoring data, ratios of concentrations observed for different averaging times, and meteorological considerations). ATSDR: Threshold from LOAEL of 10.2 ppm which is based on reduced lymphocyte proliferation following mitogen stimulation in mice. The LOAEL was adjusted for continuous exposure (10.2 ppm x 6hr/24/hr = LOAEL ADJ of 2.55 ppm) and an uncertainty factor of 300 was applied (10 for use of a LOAEL, 3 for extrapolation from animals to humans, 10 for human variability). The resulting value was converted to mg/m 3 using a molecular weight of 78.11/24.45 to derive a threshold of mg/m 3. OMoE: Threshold based on carcinogenicity associated with exposure to this compound. Threshold based on a unit risk estimate from the State of Texas that was based on cancer studies to occupationally-exposed workers. The inhalation unit risk estimate from Texas is 5x10-7 μg/m 3 and was used to derive an annual threshold of 2 μg/m 3. A conversion factor of 5 (based on empirical monitoring data, ratios of concentrations observed for different averaging times and meteorological considerations) was used to derive the 24-hour threshold from the annual threshold. ATSDR: An acute-duration inhalation MRL of 0.1 ppm was derived using the LOAEL of 40 ppm for reduced male fetal body weight gain from exposed pregnant mice. The LOAEL of 40 ppm was adjusted for intermittent exposure (6 hours/day) resulting in a duration-adjusted LOAEL of 10 ppm. A LOAEL HEC of 10 ppm was derived, which was divided by an uncertainty factor of 90 (3 for use of a minimally adverse effect, 3 for extrapolation from animals to humans, and 10 for human variability). The MRL was converted from 0.1 ppm to 220 μg/m 3 using MW = g/mol. n-butane (surrogate: cyclohexane) , OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available). Cyclohexane , OMoE: Threshold based on a health endpoint (supporting document not available). Cyclopentane (surrogate: cyclohexane) , OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available). n-decane (surrogate: cyclohexane) Dichlorobenzene (mixture) (surrogate: 1,4- dichlorobenzene) 2,3-Dimethylpentane (surrogate: cyclohexane) Ethane (surrogate: cyclohexane) , ,030 - No surrogate with available health-based thresholds was available for the C8-C10 aliphatic group, therefore cyclohexane (surrogate for the C2-C8 aliphatic group) was used as the surrogate. OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available). OMoE: Threshold based on health effects (exposure to 1,4-dichlorobenzene) (supporting documentation available). The threshold is based on the value derived by Health Canada (Health Canada 1996) which is based on a NOAEL (value not specified) from increased liver and kidney weights, urinary protein and coproporphyrin in a rat long-term study. The NOAEL was adjusted to continuous exposure and uncertainty factors applied to account for intraand inter-species variation and for the less than lifetime exposure of this study (value not specified). When converted to a daily averaged air concentration, the RfC becomes 95 µg/m 3 based on a body weight of 27 kg and a respiration rate of 12 m 3 /day (for a human aged 5 to 11 years). ATSDR: The acute MRL for 1,4-dichlorobenzene is based eye and nose irritation in humans. The MRL is based on a NOAEL of 15 ppm in an occupational exposure study in which humans were exposed for 8h/day. A safety factor of 10 was applied resulting in a MRL of 2 ppm. The MRL was adjusted for continuous exposure over 24 hours by multiplying by 8/24. The resulting threshold of 0.67 ppm was converted to 4,030 µg/m , OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available) , OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available). Ethylbenzene ,000 21,710 (5 ppm) - OMoE: Threshold based on health endpoint (supporting documentation not available). ATSDR: An acute-duration inhalation MRL was identified using benchmark dose (BMD) analysis of auditory threshold data. The lowest human equivalent concentration (HEC) of 669 mg/m 3 ( ppm) was selected as the point of departure. This HEC was divided by an uncertainty factor of 30 (3 for extrapolation from animals to humans with dosimetric adjustments and 10 for human variability) resulting in an acute-duration inhalation MRL of 21.7 mg/m 3 (5 ppm). Formaldehyde OMoE: Threshold based on health endpoint and odour (supporting document not available). n-heptane , OMoE: Threshold based on health effects.

17 Cenovus FCCL Ltd Appendix 3-VI Table 2 Acute Inhalation 24-Hour Health-Based Thresholds (continued) Parameter Alberta (a) Ambient Air Quality Objectives CCME NAAQO (b,c) OMoE (d,e) ATSDR (f) WHO (g,h) Toxicological Endpoints and Derivations Desirable Acceptable Tolerable Hexane (n-hexane) 7, , Isobutane (surrogate: cyclohexane) Isopentane (surrogate: cyclohexane) Alberta: Alberta adopted the Cal OEHHA chronic reference exposure level as the 24-hour objective. The Cal OEHHA threshold was based on peripheral neuropathy in male mice exposed for 1 year. The NOAEL was 352 mg/m 3 (100 ppm) and the NOAEL HEC was 204 mg/m 3 (57.9 ppm). An uncertainty factor of 30 (3 for interspecies differences and 10 for intraspecies differences) was applied. OMoE: Threshold based on health endpoint from exposure to n-hexane. The threshold of 7500 μg/m 3 applies to n-hexane and hexane isomers only , OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available) , OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available). Isopropylbenzene (cumene) Methylcyclohexane (surrogate: cyclohexane) Methylcyclopentane (surrogate: cyclohexane) 3-Methylheptane (surrogate: cyclohexane) 3-Methylhexane (surrogate: cyclohexane) 3-Methylpentane (surrogate: cyclohexane) n-nonane (surrogate: cyclohexane) n-octane (surrogate: cyclohexane) Pentane (surrogate: cyclohexane) Propane (surrogate: cyclohexane) OMoE: The threshold is based on US EPA s derivation for a chronic reference concentration for isopropylbenzene. The health effect was a significant weight increase in the adrenal glands and kidneys in rats exposed to isopropylbenzene for 6 hours/day, 5 days/week for 13 weeks. The NOAEL was 2438 mg/m 3, adjusted for continuous exposure (435 mg/m 3 ) and an uncertainty factor of 1000 (10 for extrapolating from a subchronic to a chronic exposure, 10 for human variability, 3 for extrapolating from animals to humans, and 3 for a lack of a multigenerational study) was applied to derive the threshold , OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available) , OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available) , OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available) , OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available) , OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available) , , No surrogate with a health-based threshold was available for the C8-C10 aliphatic group, therefore cyclohexane (surrogate for the C2-C8 aliphatic group) was used as the surrogate. OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available). No surrogate with a health-based threshold was available for the C8-C10 aliphatic group, therefore cyclohexane (surrogate for the C2-C8 aliphatic group) was used as the surrogate. OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available) , OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available) , OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available). Propylene oxide Toluene ,3,4-Trimethylhexane (surrogate: cyclohexane) 3,770 (1 ppm) - OMoE: Threshold based on a US EPA RfC of 30 μg/m 3. The threshold is based on infolding of the respiratory epithelium in male and females rats after a two-year exposure to propylene oxide. The LOAEL was 71 mg/m 3 and the LOAEL HEC was 2.9 mg/m 3. An uncertainty factor of 100 (3 for interspecies extrapolation, 3 for the use of a LOAEL associated with a mild effect, and 10 for protecting sensitive individuals in humans) and a factor of 5 (to covert from an annual threshold of 0.3 μg/m 3 to a 24-hour threshold) was applied. Alberta: Threshold adopted from Michigan Department of Environmental Quality (DEQ) and Washington Department of Ecology (DOE) (supporting documentation available). The threshold was based on a reference concentration (RfC) of 400 μg/m 3 for neurological effects by the US EPA. ATSDR: The threshold was derived from a NOAEL of 40 ppm for neurological effects in 16 healthy young men exposed for 6 hours/day on 4 consecutive days. The exposure concentration was adjusted from intermittent to continuous exposure (40 ppm x 5d/7d x 8hr/24hr). An uncertainty factor of 10 for human variability was applied. The MRL of 1 ppm was converted to µg/m 3 using MW = g/mol , OMoE: The threshold for the surrogate, cyclohexane, is based on a health endpoint (supporting document not available).

18 Cenovus FCCL Ltd Appendix 3-VI Table 2 Acute Inhalation 24-Hour Health-Based Thresholds (continued) Parameter Xylene, o- (surrogate: xylenes) Xylene, m-and p- (surrogate: xylenes) Alberta (a) Ambient Air Quality Objectives CCME NAAQO (b,c) OMoE (d,e) ATSDR (f) WHO (g,h) Toxicological Endpoints and Derivations Desirable Acceptable Tolerable See Xylenes See Xylenes. Xylenes (a) (b) (c) Alberta Environment (AENV) Alberta Ambient Air Quality Objectives and Guidelines Summary. Canadian Council of Ministers of the Environment (CCME) Canadian National Ambient Air Quality Objectives: Process and Status. In: Canadian Environmental Quality Guidelines. Alberta: Threshold adopted from a Cal OEHHA chronic REL (supporting documentation available). The Cal OEHHA chronic threshold of 700 μg/m 3 (for mixed xylenes or for individual isomers) was developed from a LOAEL of 61.7 mg/m 3 (14.2 ppm) for nervous and respiratory system effects (eye irritation, sore throat, floating sensation and poor appetite) in humans for an exposure period of seven years (on average). The LOAEL was converted to an average experimental concentration of 22 mg/m 3 (5.1 ppm) and an uncertainty factor of 30 (3 for using a LOAEL and 10 for intraspecies variation) was applied. OMoE: Threshold based on health endpoint (supporting document not available). CCME Guidance Document on Achievement Determination: Canadian Ambient Air Quality Standards for Fine Particulate Matter and Ozone. PN CCME, October European Commission Council Directive 1999/30/EC of 22 april 1999 Relating to Limit Values for Sulphur Dioxide, Nitrogen Dioxide and Oxides of Nitrogen, Particulate Matter and Lead in Ambient air. (June, 1999). ( Health Canada Health-Based Tolerable Daily Intakes/Concentrations and Tumorigenic Doses/Concentrations for Priority Substances. Health Canada. ISBN: Accessed January ( (d) Ontario Ministry of the Environment (OMoE). 2012a. Ontario's Ambient Air Quality Criteria. Standards Development Branch, OMoE. ( (e) Ontario Ministry of the Environment (OMoE) Jurisdictional Screening Levels (JSL). (February, 2008) ( (f) Agency of Toxic Substances and Disease Registry (ATSDR) Minimum Risk Levels (MRLs) and Toxicological Profiles. ( (g) World Health Organization (WHO) WHO Air quality guidelines for particulate matter, ozone, nitrogen dioxide and sulphur dioxide. Global update Summary of risk assessment. (h) World Health Organization (WHO) Air Quality Guidelines for Europe. Second Edition. WHO Regional Publications, European Series, No. 91. (i) Health Canada Part I: Guidance on Human Health Preliminary Quantitative Risk Assessment (PQRA), Version 2.0. Ottawa, Canada. Note: Shaded and bold acute thresholds were used in the risk assessment. See Section 2.1 for a discussion on the hierarchy for selecting the acute thresholds. ll values are in µg/m 3, unless otherwise noted. To convert from ppm to mg/m 3, the following formula was used: (MW [g/mol] x ppm) / and divided by 1000 to convert from mg/m 3 to µg/m 3. CCME = Canadian Council of Ministers of the Environment; NAAQO = National Ambient Air Quality Objectives; OMoE = Ontario Ministry of Environment; ATSDR: Agency of Toxic Substances and Disease Registry; Cal EPA OEHHA = California Environmental Protection Agency, Office of Environmental Health Hazard Assessment; WHO = World Health Organization; ppm = parts per million; LOAEL/LOEC = Lowest Observable Adverse Effect Level/Lowest Observable Effect Concentration; NOAEL/NOEC = No Observable Adverse Effect Level/No Observable Effect Concentration; IUR = Inhalation Unit Risk; MRL = Minimal Risk Level; MW = Molecular Weight; PAH = Polycyclic Aromatic Hydrocarbons; HEC = Human Equivalent Concentration; POD = Point of Departure; BMCL = Benchmark concentration level that gives rise to a 10% response; PEF = Potency equivalent factor; REL = Reference Exposure Level; JSL = Jurisdictional Screening Level; RfC = Reference Concentration; - Value not available.

19 Cenovus FCCL Ltd Appendix 3-VI 2.2 CHRONIC INHALATION HUMAN HEALTH THRESHOLDS As part of the long-term human health inhalation risk assessment, concentrations of VOCs, acid gases, metals and PAHs were compared to air quality screening levels or guidelines derived for the protection of chronic inhalation to human health, from the following agencies: Alberta Ambient Air Quality Objectives (AAAQO; AENV 2011); United States Environmental Protection Agency (US EPA) Regional Screening Levels (US EPA 2012a); Ontario Ministry of Environment and Energy (OMoE 2012a,b); Agency for Toxic Substances and Disease Registry (ATSDR 2012); California Environmental Protection Agency, Office of Environmental Health Hazard Assessment (Cal EPA OEHHA 2012); World Health Organization Air Quality Guidelines (WHO 2000, 2006); and Texas Commission on Environmental Quality Effects Screening Levels (TCEQ 2012). The most conservative of the available health-based screening levels for a given chemical was used. Priority was given to screening levels that were health-based and had supporting documentation. Screening thresholds from the TCEQ were only used in the absence of available health-based thresholds from the agencies listed above. In addition, guidelines for nitrogen dioxide, sulphur dioxide and particulate matter were also available from the Canadian Council of Ministers of the Environment (CCME 1999, 2012). The screening levels and guidelines available from the agencies listed above are shown in Table 3. Risk levels for which the screening levels/guidelines were derived were standardized to risk levels considered acceptable by the Government of Alberta and Health Canada (Government of Alberta 2011; Health Canada 2012). For non-carcinogens, this involved adjusting to a hazard quotient of 1.0 and for carcinogens this involved adjusting to a risk level of 1 x 10-5 (i.e., one in 100,000). The risk levels for which the screening levels/guidelines were developed are noted in the column headers for each regulatory agency. Further information on the approach used to develop the screening levels/guidelines/objectives for each of the agencies is provided below.

20 Cenovus FCCL Ltd Appendix 3-VI Table 3 Chronic Air Screening Levels and Guidelines Used in the Chemical Screening Process Acid Gases Parameter Carcinogenic/ Non-Carcinogenic Alberta (a) Ambient Air Quality Objectives RL = 1x10-5 ) CCME NAAQO (b,l) (c, d, e) US EPA Desirable Acceptable Tolerable Carbon disulphide Non-Carcinogenic OMoE (f) ATSDR (g) 934 (0.3 ppm) Cal EPA OEHHA (h) RL = 1x10-5 ) (I, j) WHO TCEQ (k) (HQ = 0.3, RL = 1x10-5 ) Toxicological Endpoints and Derivations US EPA: Threshold based on peripheral nervous system dysfunction in an occupational study where 145 males worked in a viscose rayon factory. The mean exposure period was 12.1 years. The benchmark concentration was based on maximum motor conduction velocity in the ulnar and peroneal (motor) nerves and sensory nerve conduction velocity in the sural (sensory) nerve. A BMC 10 of 55 mg/m 3 (17.7 ppm) and an adjusted BMC 10 of 19.7 mg/m 3 were calculated. An uncertainty factor of 30 (10 for database deficiencies and 3 for extrapolating data to sensitive humans) was used in the threshold derivation. The threshold (0.7 mg/m 3 ) was adjusted for residential air (l). ATSDR: Threshold based on an LOAEL of 7.6 ppm (24 mg/m 3 ) from chronic inhalation exposure in artificial fibre plant workers exposed 8 hours/day, 5 days/week for an average of 12 years. The LOAEL was based on reduced motor nerve conduction velocities in the calves and ankles. The LOAEL was divided by an uncertainty factor of 30 to derive a MRL of 0.25 ppm (0.778 mg/m 3 ) which was rounded to 0.3 ppm (0.934 mg/m 3 ). The MRL was converted from ppm to mg/m 3 using a MW of g/mol. Cal OEHHA: Threshold based on the same study that US EPA used. The health effect was a reduction in motor nerve conduction velocities and the LOAEL was 24 mg/m 3 (7.6 ppm). The BMC 05 was 21 mg/m 3 (6.86 ppm) and the BMC HEC05 was 7.9 mg/m 3 (2.54 ppm). An uncertainty factor of 10 (for intraspecies differences) was applied. Carbon monoxide Carbonyl sulphide Non-Carcinogenic (2.6) TCEQ: Threshold based on health effects (interim; supporting documentation not available). Hydrogen sulphide Non-Carcinogenic US EPA: Threshold based on nasal lesions of the olfactory mucosa in a rat 10-week long inhalation study. A NOEC of 13.9 mg/m 3 was observed and a NOEC HEC 0.64 mg/m 3 was calculated. An uncertainty factor of 300 (10 for extrapolating to sensitive humans, 10 for extrapolating from subchronic to chronic, and 3 for interspecies extrapolation) was used to derive the threshold. Cal OEHHA: Threshold based on nasal histological changes in mice when exposed for 90 days. The NOAEL was 42 mg/m 3 (30.5 ppm) and NOAEL HEC was 1.2 mg/m 3 (0.85 ppm). An uncertainty factor of 100 (3 for sub-chronic to chronic extrapolation, 3 for interspecies differences, and 10 for intraspecies differences) was applied. Nitrogen dioxide Non-Carcinogenic Alberta: Threshold based on vegetation effects. CCME: Supporting documentation not available. WHO: Threshold based on health endpoint. (Epidemiological studies show that reduced lung function growth in children is linked to elevated NO 2 concentrations within communities already at current North American and European urban ambient air levels). The threshold of 40 µg/m 3 is within the exposure ranges reported in these studies. The association between health effects and exposure to NO 2 is confounded by co-exposure to organic carbon, nitrous acid vapour, PM, and it is conservative to retain an annual threshold of 40 µg/m 3 while taking into account the direct toxic effects of chronic NO 2 exposure at low levels (WHO 2005). Sulphur dioxide Non-Carcinogenic Alberta: Threshold adopted from European Commission (1999), based on ecosystem effects (supporting documentation available). CCME: Supporting documentation not available. OMoE: Threshold based on health and vegetation endpoints (supporting document not available). PM 2.5 Non-Carcinogenic CCME (l) : Canadian ambient air quality standard protective of human health and the environment, proposed for the year The metric is the 3-year average of the annual average concentrations. WHO: Threshold represents the lowest level at which total, cardiopulmonary and lung cancer mortality have been shown to increase with more than 95% confidence in response to long term exposure. PM 10 Non-Carcinogenic WHO: Threshold represents the lowest level at which total, cardiopulmonary and lung cancer mortality have been shown to increase with more than 95% confidence in response to long term exposure.