Regulating air contaminants from industrial sources is a priority in Ontario. Ontario’s local air quality regulation (O. Reg. 419/05: Air Pollution – Local Air Quality) works within the province’s air management framework by regulating air contaminants released into communities by various sources including local industrial and commercial facilities. The ministry regulates contaminants in air to protect human health and the environment. Air standards are used to assess the contributions of contaminants to air by regulated facilities and may trigger investments in best available technologies and practices to reduce air emissions and improve air quality over time.
The existing standard(s) for sulphur dioxide were originally developed in 1974 and retained in O. Reg. 419/05 when it was promulgated in 2005. Since then, toxicological information has been published and considered in this proposal to update this air standard and AAQC.
The rationale for the air standards are based on the same science used to develop the AAQCs. This proposal also includes amendments to Schedule 6 for Upper Risk Thresholds (URTs) for Sulphur Dioxide.
1. Ambient Air Quality Criteria (AAQCs)
In the standards setting process, the ministry generally first sets ambient air quality criteria (AAQCs) as the preliminary step. AAQCs are non-regulatory values used to evaluate ambient air quality that results from all sources of a contaminant to air. AAQCs are listed in the ministry document entitled, "Ontario's Ambient Air Quality Criteria". The current AAQCs for sulphur dioxide in Ontario are 690, 275 and 55 µg/m3 (micrograms per cubic meter of air) for 1-hour, 24-hour and annual averaging times, respectively. These AAQCs were set based on respiratory effects and damage to vegetation.
Based on the evaluation of the scientific rationale of air guidelines from leading agencies, an examination of current toxicological research information and on the comments from stakeholders, the ministry is proposing the following AAQCs for Sulphur Dioxide:
- Ten-minute (10-min) average AAQC of 180 μg/m3 (micrograms per cubic metre of air) for Sulphur Dioxide based on the respiratory effects in exposed sensitive populations.
- One hour (1-hr) average AAQC of 100 μg/m3 (micrograms per cubic metre of air) for Sulphur Dioxide based on the respiratory effects in exposed sensitive populations.
- Annual (year) average AAQC of 10 μg/m3 (micrograms per cubic metre of air) for Sulphur Dioxide based on the vegetative damage in exposed sensitive species.
2. Air Standards for Sulphur Dioxide in O. Reg. 419/05
The rationale for the air standards are based on the same science used to develop the AAQCs. Air standards are regulatory values used to evaluate discharges of a contaminant from a facility at a point of impingement (POI). The current half-hour, 1 hour and 24-hour average air standards for Sulphur Dioxide are 830, 690 and 275 μg/m3, respectively. The ministry is proposing the following air standards for Sulphur Dioxide to replace these existing air standards:
- One hour (1-hr) standard of 100 μg/m3 (micrograms per cubic metre of air) for Sulphur Dioxide based on the respiratory morbidity in exposed sensitive populations.
- Annual (year) standard of 10 μg/m3 (micrograms per cubic metre of air) for Sulphur Dioxide based on the vegetative damage in exposed sensitive species.
The annual and 1 hour standards are proposed to be incorporated into Schedule 3 of O. Reg. 419/05.
Transitional Operating Conditions
Section 10 of O. Reg. 419/05 requires a facility to model the operating scenario that would result in the highest concentration of a contaminant at a point of impingement that the facility is capable of. It has been identified that section 10 of the Regulation and related guidance in Guideline A10: Procedure for Preparing an Emission Summary and Dispersion Modelling (ESDM) Report were being inconsistently interpreted and that clarification was needed. Providing clear rules would promote consistent interpretation and application of Section 10 by the regulated community, air practitioners and ministry staff when preparing and reviewing ESDM reports. It would also provide a better depiction of a facility’s compliance with air standards and whether there is the potential for adverse effects for certain operating conditions.
The proposed amendments clarify that all facilities will need to consider scenarios that include start-up and shut-down and when the facility is operating at its maximum design capacity. All other scenarios, when a facility is operating normally, will also need to be considered.
Sulphur dioxide is a contaminant that may cause acute health effects if a person is exposed to elevated emissions over short periods of time such as emissions that may occur during TOC scenarios. Petroleum refineries are of particular concern as high levels of sulphur dioxide can be emitted as a result of acid gas flaring (that is flaring of process gases that contain sulphur). A new provision of the regulation would require that acid gas flaring from petroleum refineries be added to the operating scenarios noted above for modelling to determine compliance with the sulphur dioxide standard.
To supplement the proposed amendments to section 10 of the Regulation, a new provision of the regulation would allow a Director to require a facility to consider ‘non-normal’ operating scenarios by way of a notice. This is particularly important for discharges of contaminants with the potential for acute health effects where effects may occur over a short-term exposure or where operating conditions are occurring frequently. In addition a new order provision would require a facility to model a specific incident that has occurred (e.g. a malfunction).
This proposal in its entirety will aid in the prevention of incidents that have the potential for adverse effects caused by the release of contaminants. This proposal will potentially lead to reduction of emissions of sulphur dioxide and improved local air quality near petroleum refineries (e.g. primarily in the Sarnia area).
After consultation on the proposed amendments and the proposed new/updated air standards, the ministry's intent is to arrive at a decision regarding the science-based standards and other proposed amendments. The standards and other proposed amendments would then be incorporated into O. Reg. 419/05. The ministry will also update the document "Ontario's Ambient Air Quality Criteria" and the document “The Air Contaminants Benchmarks (ACB) List: Standards, guidelines and screening levels for assessing point of impingement concentrations of air contaminants". Other guidance documents that are affected by this proposal may also be updated or introduced to reflect the final decisions.