Long-term trends in British Columbia lower mainland air quality: Criteria air pollutants and VOC

ABSTRACT

The lower mainland of British Columbia is a geographic region that comprises the districts of Metro Vancouver and the Lower Fraser Valley. It is situated in a complex topographical and coastal location in southwestern British Columbia. Metro Vancouver is Canada’s third largest population center. Accessing the Canadian National Air Pollution Surveillance Program (NAPS) database we calculated air pollutant statistics using the Canadian Ambient Air Quality Standards (CAAQS) averaging times, numerical forms, and numerical levels for the years 2001to 2020. Man Kendall and Sen statistical methods were used to test for the presence of trends and the slope of those trends in fine particulate matter (PM_2.5), ozone (O₃), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and volatile organic compound (VOC) ambient air concentrations. We did not determine a significant trend in 98^th percentile of the daily 24-hr average PM_2.5 concentrations. We did determine significant negative trends in the annual average of the daily 24-hr average PM_2.5 concentrations at 6 of the 9 locations. Episodic, multi-day duration elevated PM_2.5 concentrations related to forest fires were a significant influence on PM_2.5 ambient concentrations. Annual 4^th highest daily maximum 8-hr average O₃ concentrations showed no trend at 14 of 18 locations, declined at 3 locations, and increased at one location. We determined statistically significant declines in peak and average NO₂ and SO₂ concentrations, and in time-integrated annual VOC concentrations.

Implications: This non-parametric, statistical analysis determines 20-year trends in British Columbia lower mainland ambient air quality for PM_2.5, O₃, NO₂, SO₂ and VOC, assesses air quality against Canadian Ambient Air Quality Standards, and highlights the importance of event-based wildfire-sourced PM_2.5.

Acknowledgment

The authors thank the reviewers for their constructive comments on the manuscript. They acknowledge Taylor and Francis Editing Services for their work on manuscript formatting.

Author contributions

Conceptualization, analysis, writing, draft preparations KP; data retrieval-calculation-validation, draft review TD.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data used in this study are available upon request from the corresponding author.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

No external funding was sought, nor was any received for this study. The authors’ work and their respective contributions were on a strictly pro bono basis in the interests of informing air shed managers, regulators, and the public.

Notes on contributors

Kevin Percy

Kevin Percy is retired Senior Scientist-Global Change, Natural Resources Canada, and the former Executive Director-Lead Scientist of the science-based, multistakeholder Wood Buffalo Environmental Association, Fort McMurray Alberta.

Tom Dann

Tom Dann is the former Manager, NAPS Operations, Environment and Climate Change Canada.