Background:Wildfire activity is predicted to increase in many parts of the world due to changes in temperature and precipitation patterns from global climate change. Wildfire smoke contains numerous hazardous air pollutants and many studies have documented population health effects from this exposure.Objectives:We aimed to assess the evidence of health effects from exposure to wildfire smoke and to identify susceptible populations.Methods:We reviewed the scientific literature for studies of wildfire smoke exposure on mortality and on respiratory, cardiovascular, mental, and perinatal health. Within those reviewed papers deemed to have minimal risk of bias, we assessed the coherence and consistency of findings.Discussion:Consistent evidence documents associations between wildfire smoke exposure and general respiratory health effects, specifically exacerbations of asthma and chronic obstructive pulmonary disease. Growing evidence suggests associations with increased risk of respiratory infections and all-cause mortality. Evidence for cardiovascular effects is mixed, but a few recent studies have reported associations for specific cardiovascular end points. Insufficient research exists to identify specific population subgroups that are more susceptible to wildfire smoke exposure.Conclusions:Consistent evidence from a large number of studies indicates that wildfire smoke exposure is associated with respiratory morbidity with growing evidence supporting an association with all-cause mortality. More research is needed to clarify which causes of mortality may be associated with wildfire smoke, whether cardiovascular outcomes are associated with wildfire smoke, and if certain populations are more susceptible.Citation:Reid CE, Brauer M, Johnston FH, Jerrett M, Balmes JR, Elliott CT. 2016. Critical review of health impacts of wildfire smoke exposure. Environ Health Perspect 124:1334–1343; http://dx.doi.org/10.1289/ehp.1409277

Wildfire activity is predicted to increase with global climate change, resulting in longer fire seasons and larger areas burned. The emissions from fires are highly variable owing to differences in fuel, burning conditions and other external environmental factors. The smoke that is generated can impact human populations spread over vast geographical areas. Wildfire smoke is a complex mixture of pollutants that can undergo physical and chemical transformation processes during transport and can have major impacts on air quality and public health. This review looks at the main features of smoke that should be considered in the assessment of public health risk. It describes the current state of knowledge and discusses how smoke is produced, what factors affect emissions and smoke distribution, and what constituents of smoke are most likely to cause adverse health effects.

BackgroundSeveral studies have evaluated the association between forest fire smoke and acute exacerbations of respiratory diseases, but few have examined effects on pharmaceutical dispensations. We examine the associations between daily fine particulate matter (PM2.5) and pharmaceutical dispensations for salbutamol in forest fire-affected and non-fire-affected populations in British Columbia (BC), Canada.MethodsWe estimated PM2.5 exposure for populations in administrative health areas using measurements from central monitors. Remote sensing data on fires were used to classify the populations as fire-affected or non-fire-affected, and to identify extreme fire days. Daily counts of salbutamol dispensations between 2003 and 2010 were extracted from the BC PharmaNet database. We estimated rate ratios (RR) and 95% confidence intervals (CIs) for each population during all fire seasons and on extreme fire days, adjusted for temperature, humidity, and temporal trends. Overall effects for fire-affected and non-fire-affected populations were estimated via meta-regression.ResultsFire season PM2.5 was positively associated with salbutamol dispensations in all fire-affected populations, with a meta-regression RR (95% CI) of 1.06 (1.04-1.07) for a 10 ug/m3 increase. Fire season PM2.5 was not significantly associated with salbutamol dispensations in non-fire-affected populations, with a meta-regression RR of 1.00 (0.98-1.01). On extreme fire days PM2.5 was positively associated with salbutamol dispensations in both population types, with a global meta-regression RR of 1.07 (1.04 - 1.09).ConclusionsSalbutamol dispensations were clearly associated with fire-related PM2.5. Significant associations were observed in smaller populations (range: 8,000 to 170,000 persons, median: 26,000) than those reported previously, suggesting that salbutamol dispensations may be a valuable outcome for public health surveillance during fire events.

Landscape fires can produce large quantities of smoke that degrade air quality in both remote and urban communities. Smoke from these fires is a complex mixture of fine particulate matter and gases, exposure to which is associated with increased respiratory and cardiovascular morbidity and mortality. The public health response to short-lived smoke events typically advises people to remain indoors with windows and doors closed, but does not emphasize the use of portable air cleaners (PAC) to create private or public clean air shelters. High efficiency particulate air filters and electrostatic precipitators can lower indoor concentrations of fine particulate matter and improve respiratory and cardiovascular outcomes. We argue that PACs should be at the forefront of the public health response to landscape fire smoke events.

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Objectives: Our objective was to estimate the burden of mortality attributable to long-term exposure to ambient fine particulate matter (PM 2.5) among adults in two rural regions of British Columbia, the Interior and the North, in order to provide information for public health professionals setting health priorities. Methods: We used the standard method to calculate the fraction of all-cause mortality among adults (≥30 years old) attributable to long-term exposure to ambient PM 2.5 as described in the World Health Organization global burden of disease study. PM 2.5 concentration was either locally measured using tapered element oscillating microbalance (TEOM) continuous monitors or estimated for unmonitored cities. For the base case, we used a conservative PM 2.5 threshold (5.0 ug/m 3); for sensitivity analysis, we set the threshold to estimate all mortality attributable to anthropogenic PM 2.5 (3.1 ug/m 3). We conducted sensitivity analysis for PM 2.5 concentrations estimated in unmonitored cities. Results and Conclusions: Mean annual PM 2.5 concentration ranged from 3.1 to 7.4 ug/m 3 across local health areas in Northern and Interior BC. Sixty percent of the adult population lived in monitored regions. PM 2.5 was estimated to cause 0.20% of all-cause mortality among adults (16 deaths/year). Anthropogenic PM 2.5 was estimated to cause 0.93% of all-cause mortality among adults (74 deaths/year). Estimates were sensitive to both PM 2.5 threshold and estimated PM 2.5 in unmonitored communities. This demonstrates that ambient PM 2.5 air pollution does have an important mortality burden, even in a region with relatively low PM 2.5 concentrations.

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Objective Canadian colorectal cancer screening rates differ across income strata. In the United States, disparities across income strata worsen in rural areas. In Canada, differences in screening across income strata have not been explored by levels of urbanization. This project aimed to estimate up-to-date colorectal cancer (UTD-CRC) screening across income strata by levels of urbanization. Methods Data from the Canadian Community Health Survey (2013/2014) were used to estimate the prevalence of UTD-CRC screening by income quintiles for Canadians aged 50-74 years. UTD-CRC screening was defined as fecal occult blood testing within 2 years or colonoscopy/sigmoidoscopy within 10 years before the survey. Levels of urbanization were defined per Statistics Canada Metropolitan Influenced Zone classifications. Weighted proportions of UTD-CRC screening were calculated and logistic regression was used to assess the effect of income by levels of urbanization. Results Self-reported UTD-CRC screening prevalence among Canadians was 52.0%. UTD-CRC screening rates by income ranged from 47.8% (Q1-low) to 54.0% (Q5-high). Across all levels of urbanization, higher income was associated with increased odds of UTD-CRC screening compared to the lowest income quintile (