New/updated screening levels for the Air Contaminants Benchmarks (ACB) list

Description of policy

The ministry is proposing to update the Air Contaminants Benchmarks (ACB) List with new or updated screening levels for over 4500 contaminants, to help the regulated community assess the potential for adverse effects from their air emissions. See attachment 1, Proposed Air Contaminants Benchmarks (ACB) List.

The ACB List is a compilation of air standards and guidelines as well as screening levels. This proposal addresses screening levels. It does not impact the standards and guidelines on the list.

This proposal responds to multiple requests from the regulated community for additional tools to facilitate screening of contaminants. It is recognized that expanding the ACB list with additional screening levels will support the regulated community, as it will reduce the number of toxicological assessments needed, saving time and money for industry without negatively impacting the environment.

Approaches used to determine the new/updated screening levels

The ministry’s proposed expanded and updated list of screening levels was developed from two sources: (1) air quality values from 11 health/environmental agencies in other jurisdictions; and (2) ministry’s recommendations from previous in-house toxicological assessments performed. Further details on these approaches are available in the proposed updated ACB List (attachment 1, see Introduction).

Implementation of updated screening levels

In addition to proposing to update the ACB List with new/updated screening levels (see attachment 1), the ministry is seeking input on a proposed approach to maintaining an up-to-date ACB List over time:

1. ACB List Update Frequency – It is proposed that the ACB List be updated annually in April of each calendar year to reflect any new/updated screening levels, by posting an Information Notice on the Environmental Registry. A link to the updated ACB List would also be made available on the ontario.ca website. Annual updates to the screening levels could reflect toxicological assessments submitted to the ministry by stakeholders, findings from the ministry’s own in-house toxicological assessments, and any future reviews of the screening levels derived from other jurisdictions.
2. Approach for stakeholders to contribute screening levels to the ACB List – It is proposed that the ministry would consider recommended new screening levels when external parties choose to provide the ministry with their recommendation along with a toxicological assessment. The ministry would review the submission and, if appropriate, accept the value for inclusion in the next update to the screening levels on the ACB List.
3. Transition period – Of the approximately 1200 existing screening levels that have been updated in the proposed new list, approximately 450 are more stringent, and approximately 50 are being removed from the list altogether.

These more stringent screening levels may, in certain circumstances, impact how an Emission Summary and Dispersion Modelling report (ESDM report) is prepared. For example, further refinement of emission estimates may be needed to demonstrate that concentrations are below the more stringent screening level and in some cases, a toxicological assessment may be needed to determine whether there may be an adverse effect.

To acknowledge this possibility, the ministry is proposing to post the amendments to the ACB List in April of each year. This would give persons required to annually update their ESDM report approximately one year to address any concerns, as updates are required by March 31 each year. It should also be noted that Guideline A-10 (Procedure for Preparing an Emission Summary and Dispersion Modelling report, section 12.2 – see attachment 2) provides guidance with respect to ministry expectations regarding concentrations that exceed a screening level.

These new values will be effective immediately once they are announced on the Environmental Registry (with link to the updated list on the ontario.ca website). Any ESDM report prepared after the date of the published update will be required to use the new/updated screening levels.

Consultation questions

The ministry invites comments on this proposal including responses to the following:

1. The proposed updated and expanded list of screening levels is based on examination of other jurisdictions’ values, as well as results of the ministry’s own in-house toxicological assessments. What other approaches or methods could be considered in setting screening levels in future ACB List updates?
2. The ministry would like to continue to expand the list of screening levels over time. What approaches could be considered, to prioritize new contaminants for addition to the list of screening levels?
3. The ministry is suggesting that stakeholders could provide toxicological reviews and proposed screening levels for ministry consideration and inclusion in future ACB List updates. How else could the stakeholder community be engaged in contributing screening levels?
4. The ministry is proposing annual updates to the ACB List. Do you have any feedback on the proposed frequency and timing of updates to the screening levels on the ACB List?

Please also let the ministry know if you notice any potential errors in the proposed new/updated ACB List.

Purpose of policy

Under both Ontario Regulation 419/05 Air Pollution – Local Air Quality, and Ontario Regulation 1/17: Registrations Under Part II.2 of the Act - Activities Requiring Assessment of Air Emissions, all contaminants released to air above negligible amounts must be assessed for their potential to cause adverse effects.

Contaminants are assessed using benchmarks (standards, guidelines and screening levels), if available, or by a toxicological assessment.

Screening levels were first introduced in 2008 to help expedite air emissions approvals. In January 2017, these 2008 values were compiled along with air standards and guidelines into the ACB List.

This proposal is to expand the ACB List to provide new screening levels for ~3500 contaminants and update the screening levels for ~1200 contaminants.

Screening levels serve as a tool to quickly determine if an assessment is required. They are conservative benchmarks below which adverse health effects from air emissions are not expected. If a facility’s emission concentrations are below a screening level, no further assessment is required. If a screening level is exceeded, or no screening level is available for the contaminant, further assessment is needed, which may include a toxicological assessment.