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UBC Theses and Dissertations

Assessing sub-daily exposure to wildfire smoke and its public health effects in British Columbia Yao, Jiayun


Global climate change has created new public health issues, and evidence-based policies are needed for mitigating the health impacts. The increasing frequency and intensity of wildfires is one of the pressing concerns in Canada and globally. Epidemiological studies have found that daily average exposure to wildfire smoke is associated with a wide range of cardiopulmonary conditions. However, few studies have looked at the health effects of sub-daily exposures measured in hours, and little is known about the lag-response relationship at such temporal scales. Sub-daily impacts are highly relevant for public health response, especially for smoke episodes of limited duration. To address these knowledge gaps, this dissertation presents a machine learning approach to identify variables relevant to the vertical distribution of smoke in the atmosphere, which can improve the application of remote sensing data for population exposure assessment. Relevant variables included fire activity in the vicinity, geographic location of the smoke, and meteorological conditions. These variables were next combined with data from air quality monitors and ecological information, to develop an empirical model for estimating 1-hour average population exposure to fine particulate matter (PM₂.₅) during wildfire seasons from 2010 to 2015 in British Columbia, Canada, at a 5 km² resolution. Compared with observations, model predictions had a correlation of 0.93, root mean squared error of 3.2 μg/m³, mean fractional bias of 15.1%, and mean fractional error of 44.7%. The model estimates were then linked to ambulance dispatches, paramedic assessments, and subsequent hospital admissions. Increased PM₂.₅ was associated with increased dispatches for respiratory and cardiovascular reasons within one hour following exposure, and for diabetic reasons within the first 24-hour period. Each 10 μg/m³ increase in PM₂.₅ was associated with an increase in the cumulative odds over 48 hours of up to 10%, 20% and 10% for respiratory, cardiovascular, and diabetes calls, respectively. These results support further investigation into the health effects of sub-daily exposures and suggest that air quality standards and public health actions during wildfire smoke events should be based on the hourly time scale. Public health agencies and the general public should act promptly to reduce exposure when affected by wildfire smoke.

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