Air Toxics in Canada Measured by the National Air Pollution Surveillance (NAPS) Program and their Relation to Ambient Air Quality Guidelines

Measured concentrations are compared to ambient air quality guidelines from Canadian jurisdictions and compounds that exceeded guidelines are identified and discussed. Though this study does not assess risk or cumulative effects, air toxics that approached guidelines are also identified so that their potential contribution to ambient air toxics pollution can be considered.Eleven air toxics exceeded at least one guideline and an additional sixteen approached guidelines during the study period.

Four compounds were measured using methods whose detection limits exceeded a guideline value, three of which could not be compared to guidelines since they were not detected in any samples. The assessment of several metal(loid) concentrations is tentative since they were measured only in fine particulate matter (PM) but compared to guidelines based on coarse or total PM. Improvements to sampling and analysis techniques for the latter compounds as well as for those whose methods are subject to known uncertainties would improve confidence in reported concentrations and their relation to applicable guidelines.