Fires, Smoke, and Health: Impacts and Prevention

Vegetation fire frequency and intensity are expected to increase as a consequence of climate change. Among the impacts of vegetation fires are health effects related to smoke exposure. Approaches to estimate population exposure to fire smoke are required to evaluate these impacts and to develop effective strategies to mitigate human health impacts. Remote sensing-based approaches are especially appropriate as many smoke events impact rural areas or smaller communities without routine surface air quality monitoring. Even when larger communities are affected, air quality monitors may cease to function during major smoke events.

Relative to the other potentially-harmful pollutants in fire smoke, increases in fine particulate matter are the most pronounced and persistent.  These particles remain suspended in the air for days to weeks and therefore can impact air quality over large regions. In addition, such particles readily penetrate into indoor environments.  Extensive epidemiologic literature implicates particles of this size in a wide range of cardiovascular, respiratory and reproductive health effects, with no evidence of a “safe” threshold, suggesting that any increase in fine particulate matter is associated with some increased risk to public health. Review of the literature relative to fine particles from vegetation fire smoke indicates a generally-consistent relationship between smoke exposure and increased risk of respiratory symptoms, hospital admissions, emergency room visits and decreased lung function. Findings related to cardiovascular impacts of vegetation fire smoke are mixed, with several studies indicating systemic inflammatory responses but inconsistency in studies of cardiovascular hospitalizations or mortality. Overall, however, there is little evidence to suggest that particulate matter from vegetation fire smoke elicits different impacts than particulate matter from other sources. 

Given these health impacts, strategies to mitigate the public health impacts are required. Smoke forecasting tools such as BlueSky (in the U.S) and BlueSky Western Canada Wildfire Smoke Forecasting System (in Canada) can be used in combination with available local air quality measures to help individuals and public health professionals prepare for smoke episodes.  The health risks associated with fire smoke can be reduced by limiting exposure to smoke-related particulate matter, especially for individuals with preexisting heart and lung conditions. Specifically, vigorous outdoor activity should be avoided, and indoor environments should be protected from smoke penetration by closing doors and windows (if not too hot) and using air conditioners.  Studies have also shown that properly-sized HEPA-filter air cleaners can effectively reduce fine particulate matter levels indoors. At a community-level, establishment of clean air shelters is recommended while relocation to a more protected environment should be considered in situations where indoor smoke is unavoidable.