The Ontario Ministry of the Environment, Conservation and Parks (MECP) released an updated version of the Air Contaminants Benchmarks (ACB) list on March 31, 2023 and adopted updated air dispersion model versions on April 13, 2023. Neither of these changes required public consultation and therefore they took effect upon publication in the Environmental Registry of Ontario. The ACB list and air dispersion models are primarily used to complete an Emission Summary and Dispersion Modelling (ESDM) report under O.Reg. 419/05 or O.Reg. 1/17, to obtain or update an Environmental Compliance Approval (ECA) or an Environmental Activity and Sector Registry (EASR) registration. Air Contaminants Benchmarks (ACB) list.
The ACB list is a reference tool that was first introduced by the MECP in 2017 and is a compilation of air standards, guidelines, and screening levels for approximately 5,200 contaminants. The 2023 updates to the ACB list include:
• The removal of half-hour (Schedule 2) standards. As of February 1, 2020, all facilities in Ontario have been required to comply with Schedule 3 air standards (using newer air dispersion models). Standards and guidelines are not to be exceeded.
• Updates to non-regulatory screening levels. Note that if a screening level is exceeded, further assessment must be completed, which may include toxicological assessments.
Updated Air Dispersion Model Versions
Section 6 of Ontario Regulation 419/05 lists the dispersion models approved for use in assessing compliance with air standards, which include the U.S. EPA AERMOD dispersion model, ASHRAE method of calculation and the U.S. EPA SCREEN3 dispersion model. The ASHRAE version (Chapter 46 of the 2019 ASHRAE Handbook) and the SCREEN3 version (February 12, 2013) remain the unchanged, approved versions.
The use of version 19191 of AERMOD (and AERMET, the associated meteorological data preprocessor), has been updated to version 22112 (version date April 22, 2022). Ontario Regional Meteorological data sets that have been reprocessed with version 22112 of AERMET, are available on the Ontario government website. If an area has mixed dominant land uses or a significant proportion of water, the MECP recommends the use of site-specific meteorological data which must be requested from the MECP’s Environmental Monitoring and Reporting Branch.
As of April 13, 2023, the updated version of AERMOD/AERMET must be used. Any new ECA applications submitted or EASR registrations made after this date must include the use of the updated version. For an ECA with Limited Operational Flexibility (LOF), the first modification assessed after this date must use the updated version of AERMOD.
Conclusion
The use of the updated ACB list and updated versions of the air dispersion models are now in effect. The Trinity Toronto office can assist with dispersion modelling and assessing the impact of changes to the ACB list, as well as assisting with ECA applications and EASR registrations. If you have any questions, please do not hesitate to reach out to Sundar Sadashivam in Trinity’s Toronto office.
