An Updated Air Contaminants Benchmark (ACB) List Released
April 2023
The Human Toxicology and Air Standards Section of the Ontario Ministry of Environment, Conservation and Parks (MECP) released the latest version (V.3.0 – April 2021) of the Air Contaminants Benchmark (ACB) on March 31, 2023 (Ontario Environmental Registry of Ontario). The ACB contains approximately 5,200 contaminants with corresponding benchmarks (air standards, guidelines, or screening values) used to assess point of impingement (POI) concentrations of contaminants in air by emitters required to prepare Emission Summary and Dispersion Modelling (ESDM) under Ontario Regulation 419/05 and Ontario Regulation 1/17.
The ACB list is made up of B1 and B2 benchmark concentrations. B1 benchmark concentrations typically represent air standards and guidelines, whereas B2 benchmark concentrations represent screening levels. If a B1 benchmark concentration (an air standard or guideline) is exceeded, specific actions are triggered under Ontario Regulation 419/05 and the exceedance is considered an offence under O. Reg. 1/17. If a B2 benchmark concentration is exceeded, or if no B2 value exists, a toxicological assessment to determine the likelihood of adverse effects is triggered/required. Wolf Environmental Science Ltd. specializes in conducting Toxicological Assessments.
The overarching changes to the previous ACB list (V2.0 – 2018) include:
- Revised screening levels for frequently-occurring contaminants (gasolines, kerosenes, isoprene);
- New screening levels and guidance for metal-containing compounds not already captured by existing benchmarks for metals;
- New and updated screening levels resulting from recent toxicological assessments and the review of values from another jurisdiction, respectively; and
- The removal of all half-hour B1 benchmarks (air standards or guidelines) to be consistent with the phase-out of all Schedule 2 air standards with a half-hour averaging period (as of February 1, 2020) under Ontario Regulation 419/05.
In addition to the revised ACB list (V3.0 – April 2021), the MECP has provided several additional tables that are referenced within the ACB list, including:
- Table 1: Schedule 8 (Dioxin, Furans and and Dioxin-Like PCBs) of Ontario Regulation 419/05 has been added – provides all compounds for which the Dioxin air standard applies and their associated Toxic Equivalency Factors;
- Table 2: Modelling Assessment Values – provides the assessment values (AVs) to be used when evaluating modelling data for compounds with an annual average air standard;
- Table 3: Monitoring Assessment Values – provides AVs which may be used when evaluating monitored data for compounds with an annual average air standard;
- Table 4: Schedule 6 (Upper Risk Thresholds or URTs) of Ontario Regulation 419/05 have been referenced in the ACB list;
- Table 5: A list of 182 B2 benchmark values that have been removed from the ACB list; and,
- Table 6: A list of all half-hour B1 benchmark values that have been removed from the ACB List (Version 2.0 – April 2018) to be consistent with the phase-out of all Schedule 2 air standards with a half-hour averaging period by February 1, 2020.
Proposed Drinking Water Quality Objective for Total PFAS
February 2023
Health Canada has released a technical document outlining the proposed Canadian Drinking Water Quality Objective for per- and polyfluoroalkyl substances (PFAS). An objective of 30 ng/L has been proposed for the sum of total PFAS. Comment period ends April, 12, 2023. The document can be found here: https://www.canada.ca/content/dam/hc-sc/documents/programs/consultation-draft-objective-per-polyfluoroalkyl-substances-canadian-drinking-water/overview/overview.pdf
The Draft CCME Canadian Soil Quality Guideline for Lead
June 25 2020
Earlier this month, the Canadian Council of Ministers for the Environment (CCME) released their draft ‘Scientific Criteria Document for the Development of the Canadian Soil Quality Guidelines for the Protection of Human Health – Lead’ for public review and comment. The provisional soil quality guidelines developed to protect human health (PSoQGHH) from lead in soil through direct contact (via dermal contact, incidental ingestion and inhalation) are: 70 mg/kg soil for agricultural and residential/parkland land uses, 95 mg/kg soil for commercial land use and 870 mg/kg foil for industrial land use. Comment period ends August 4th 2020. The technical document can be found at: https://www.ccme.ca/en/whats_new/article.html?id=137
The Toronto Subway Air Quality Health Impact Assessment
January 29 2020
After nearly a year of work, Ollson Environmental Health Management (OEHM) and Wolf Environmental Science Ltd. (WOLF) have completed the Toronto Subway Air Quality Health Impact Assessment (TSQA HIA). The HIA incorporated a Human Health Risk Assessment (HHRA) to calculate the potential health risks from exposure to air pollutants in the subway. Globally there has been an increased focus on air quality issues in major subway systems. Internationally, the TSQA HIA is one of the most comprehensive subway health assessment conducted to date.
The TSAQ HIA sought to answer three overarching questions:
1. What is the potential health risk to current passengers from air pollutants in the subway system?
2. What are the potential health benefits to mitigation measures that could be implemented to improve air quality in the TTC subway system?
3. What is the overall impact of the TTC’s subway system on the health and well-being of Torontonians?
The complete report can be found at: https://www.toronto.ca/wp-content/uploads/2019/11/99d2-TSAQ-HIA-Final-Report-November-25_2019.pdf
Updated Air Standard for Sulphur Dioxide – On What Basis?
March 28 2018
Last week (March 20th, 2018), the Ontario Ministry of the Environment and Energy (MOECC) posted a Regulatory Decision Notice (and supporting documentation) to the Environmental Registry (EBR Registry Number: 013-0903) concerning, among other items including upper risk thresholds, changes to the Ontario Air Standards for Sulphur Dioxide (SO2) under Ontario Regulation 419/05 (https://ero.ontario.ca/notice/013-0903).
The MOECC has finalized an eco-based annual average air standard of 10 µg/m3 (or approximately 4 ppb) for sulphur dioxide (SO2). More specifically, the revised annual average SO2 standard was adopted to mitigate the effects (including foliar damage, decreased photosynthesis, and decreased growth) of long-term exposure to SO2 among the most susceptible of plant species (e.g., lichen).
The MOECC also finalized a human health-based 1-hour air standard of 100 µg/m3 (or approximately 40 ppb) for SO2. The revised 1-hour standard was developed to protect sensitive members of the population (i.e., exercising asthmatics) from the respiratory effects (i.e., narrowing of the bronchial passages) resulting from short-term (or acute) exposure to SO2.
The phase-in period for the updated sulphur dioxide air standards is five (5) years and will take effect on July 1, 2023. The standards will also be incorporated into the MOECC’s Air Contaminants Benchmarks (ACB) List – a collection of standards, guidelines, and screening levels for assessing point of impingement (POI) concentrations of air contaminants.
On What Basis?
Central to the development of the updated 1-hour SO2 air standard is the Health Canada (2016) 10-minute reference concentration (RfC) of 67 ppb (Approach #1); the ‘Ontario-modification of the Health Canada RfC (2016)’ of 67 ppb (Approach #2); and the rationale used to extrapolate from a 10-mintue duration to a 1-hour averaging time, as described in the MOECC Rationale Document (MOECC, 2017).
Many current-day health-based air standards for SO2, including the revised MOECC 1-hour standard, rely on the interpretation of clinical data generated by controlled human exposure studies involving free-breathing asthmatic adults exposed to SO2 while exercising. It is the interpretation of these clinical data in conjunction with other lines of evidence (e.g., information from epidemiological studies) and the resulting rationale used to apply uncertainty factors (UFs) to a specific point of departure (POD) that are critical to the development of this air standard. The application of a standard UF of 3 to account for intra-species sensitivities (i.e., to account for sensitive members within the population) to a POD derived from clinical data generated using a sensitive subset of the populations (i.e., exercising asthmatics), albeit rationalized, seems unconventional. Equally important are the rationale and methods used to extrapolate from a 10-minute exposure duration (the most toxicologically-relevant duration, as it relates to bronchoconstrictive responses among exercising asthmatics) to a 1-hour duration, required to facilitate compliance under O. Reg 419/05.
Understanding how an effects-based standard is developed, including the key assumptions used, is essential to effectively characterizing and communicating potential health hazards.
References
Health Canada. 2016. Human Health Risk Assessment for Sulphur Dioxide (CAS RN: 7446-09-5). Analysis of Ambient Exposure to and Health Effects of Sulphur Dioxide in the Canadian Population. Water and Air Quality Bureau. Safe Environment Directorate. Healthy Environments and Consumer Safety Branch. January 2016
MOECC. 2017. Ontario Ministry of the Environment and Climate Change. Rationale for the Development of Ontario Ari Standards for Sulphur Dioxide (SO2). Standards Development Branch Ministry of the Environment and Climate Change. May, 2017. environmental consulting toxicology
An Update to the Air Contaminant Benchmark (ACB) List
News - Air Quality
Under Ontario Regulation 419/05 and Ontario Regulation 1/17, contaminants released into the air above ‘negligible amounts’ must be evaluated for their potential to cause adverse effects.
To further facilitate the screening of contaminants within regulated industries, the Ontario Ministry of the Environment and Energy (MOECC) proposed, on January 18th, an update to the existing Air Contaminant Benchmark (ACB) list – a collection of screening levels, standards, and guidelines used to help assess the potential for air emitted contaminants to cause adverse effects. The proposed ACB list includes approximately 3,500 new screening levels in addition to an update of approximately 1,200 existing screening levels (http://www.ebr.gov.on.ca/ERS-WEB-External/displaynoticecontent.do?noticeId=MTM0NDA1&statusId=MjA0NDUx&language=en).
Of the 1,200-existing screening levels that were updated, approximately 450 are more stringent (i.e., lower than previously set). These more stringent screening levels could, depending on the circumstances, result in the need for a toxicological assessment to determine whether there may be an adverse effect.
Wolf Environmental Science Ltd. (Wolf) has been reviewing the proposed ACB list, paying particular attention to the 450 revised screening levels to determine the extent of the reduction on a per contaminant basis.
