Canadian Council of Ministers of the Environment Endorses New Air Quality Standards for SO2

On October 3, 2016 the Canadian Council of Ministers of the Environment (CCME) endorsed new Canadian Ambient Air Quality Standards (CAAQS) for sulphur dioxide (SO2).  The new SO2 CAAQS joins the existing PM2.5 and ozone CAAQS.  Additionally, the CCME continues to progress on the NO2 CAAQS, expected to be announced in 2017.

Table 1 shows the new 1‑hour and annual SO2 CAAQS and the form of the standards.  The form of the 1-hour standard is similar to the existing B.C. interim air quality objective for SO2 (99th percentile of the daily peak 1-hour concentrations); however, the new CAAQS also includes a 3-year average, matching the form of the U.S. national 1-hour SO2 standard.  The values of the new standards themselves are lower, more stringent than existing standards or objectives:

  • 70 ppb CAAQS compared to 75 ppb B.C. interim air quality objective for 1‑hour average, and
  • 5 ppb compared to 10 ppb NAAQO for annual average.

Table 1. SO2 CAAQS1

The British Columbia Ministry of Environment (the Ministry) has incorporated these new CAAQS into the most recently published British Columbia Ambient Air Quality Objectives, dated November 17, 2016.2  This version of the objectives continues to include the interim 1-hour SO2 objective of 75 ppb.  Also in November 2016, the Ministry released a two page information sheet3 which includes a brief description of how the new SO2 CAAQS will be implemented in B.C., stating:

The CAAQS will be used as a tool to help inform air management decisions in B.C.  While the CAAQS are not intended to be used for fenceline reporting, these standards will be used to characterize air quality and potential air quality impacts in areas where people live or where other sensitive receptors are likely to be found.  Where necessary, actions to reduce SO2 emissions will be developed in cooperation with facility operators.

Based on the above statement, it is expected that air quality assessments required for new facilities or modification projects will need to compare to the new CAAQS in residential areas and at other sensitive locations (e.g., hospitals, schools, etc.), but will not be required to demonstrate that predicted concentrations at fenceline are below the new CAAQS.

The Ministry SO2 CAAQS information sheet also discusses how the new SO2 CAAQS may affect existing industry, stating that if the CAAQS are exceeded, the Ministry will:

  • Clarify the cause of the exceedances, and
  • Work with key stakeholders and affected communities to take appropriate action to reduce SO2 emissions over time.

Table 2 summarizes the air quality management levels and actions based on the new SO2 CAAQS.  It should be noted that the new SO2 CAAQS will become effective in 2020, with lower standards in 2025.  As such, action related to improving in areas exceeding the new CAAQS may not progress fully until the 2020 effective date.

Table 2. SO2 CAAQS Air Quality Management Levels