University of Tasmania
139930 - Sub-daily exposure to fine particulate matter and ambulance dispatches.pdf (2.71 MB)

Sub-daily exposure to fine particulate matter and ambulance dispatches during wildfire seasons: a case-crossover study in British Columbia, Canada

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journal contribution
posted on 2023-05-20, 16:09 authored by Yao, J, Brauer, M, Wei, J, McGrail, KM, Fay JohnstonFay Johnston, Henderson, SB
Background: Exposure to fine particulate matter (PM2:5) during wildfire seasons has been associated with adverse health outcomes. Previous studies have focused on daily exposure, but PM2:5 levels in smoke events can vary considerably within 1 d.

Objectives: We aimed to assess the immediate and lagged relationship between sub-daily exposure to PM2:5 and acute health outcomes during wildfire seasons in British Columbia.

Methods: We used a time-stratified case-crossover study design to evaluate the association between modeled hourly PM2:5 and ambulance dispatches during wildfire seasons from 2010 to 2015. Distributed lag nonlinear models were used to estimate the lag-specific and cumulative odds ratios (ORs) at lags from 1 to 48 h. We examined the relationship for all dispatches and dispatches related to respiratory, circulatory, and diabetic conditions, identified by codes for ambulance dispatch (AD), paramedic assessment (PA) or hospital diagnosis (HD).

Results: Increased respiratory health outcomes were observed within 1 h of exposure to a 10-lg=m3 increase in PM2:5. The 48-h cumulative OR [95% confidence interval (CI)] was 1.038 (1.009, 1.067) for the AD code Breathing Problems and 1.098 (1.013, 1.189) for PA code Asthma/COPD. The point estimates were elevated within 1 h for the PA code for Myocardial Infarction and HD codes for Ischemic Heart Disease, which had 24-h cumulative ORs of 1.104 (0.915, 1.331) and 1.069 (0.983, 1.162), respectively. The odds of Diabetic AD and PA codes increased over time to a cumulative 24-h OR of 1.075 (1.001, 1.153) and 1.104 (1.015, 1.202) respectively.

Conclusions: We found increased PM2:5 during wildfire seasons was associated with some respiratory and cardiovascular outcomes within 1 h following exposure, and its association with diabetic outcomes increased over time. Cumulative effects were consistent with those reported elsewhere in the literature. These results warrant further investigation and may have implications for the appropriate time scale of public health actions.


Publication title

Environmental Health Perspectives





Article number









Menzies Institute for Medical Research


Us Dept Health Human Sciences Public Health Science

Place of publication

Natl Inst Health, Natl Inst Environmental Health Sciences, Po Box 12233, Res Triangle Pk, USA, Nc, 27709-2233

Rights statement

Copyright 2020 the authors. Reproduced with permission from Environmental Health Perspectives.

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  • Open

Socio-economic Objectives

Public health (excl. specific population health) not elsewhere classified

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