Wildfire Smoke Composition
We know that without major changes to human activity, global warming will continue and wildfires will burn with more fury and devastation. Thus, it's essential to understand how increased smoke exposure will affect our health. Wildfire smoke is composed of fine and coarse particulate matter, carbon monoxide, carbon dioxide, methane, nitrous oxide, and volatile organic compounds along with numerous other gases. PM2.5 (fine particulate matter under 2.5 microns) is the most concerning pollutant to human health because of its ability to penetrate deeply into the lung. Fine particulate constitutes a substantial proportion of wildfire-generated particulate. However, particulate size can vary depending on the intensity of the fire, type of fuel, and whether the fire is flaming or smoldering. Therefore, the composition of smoke particulate from natural wildfires burning in the dry season versus a prescribed fire intentionally set during the wet season may vary substantially. The two different types of wildfires could have markedly different effects on health, however this has not yet been studied.
In Cascio’s 2018 Systemic review, the authors found multiple studies reporting strong associations between wildfire smoke PM2.5 and respiratory exacerbations. They found increased ER visits and admissions for COPD, asthma, bronchitis and pneumonia. In the same review, the data on cardiovascular disease was inconclusive with mixed results of associations between wildfire smoke and CHF, MI and cardiac arrests.
Reid and colleagues modeled daily wildfire PM2.5 exposure from a large 2008 northern California wildfire. They found that for each 5µg/m3increase in PM2.5, the risk of emergency department visits for asthma and COPD increased. They also found that effects were more prominent in women, in people living in low socioeconomic regions, and in elderly adults. A study by Liu and colleagues confirmed these results.
Studies of wildfire firefighters pre-and post-season demonstrate a decrease in pulmonary function. The most significant and consistent finding in Black’s review of six studies was a decline in forced expiratory capacity in 1 second (FEV1). Two of the six studies were able to follow up and noted that after several months FEV1 returned to baseline. When pre-and post-shift FEV1 were compared, there was no difference in FEV, suggesting the decline is due to continual exposure instead of an acute event. However, the long term health effect of repeated wildfire smoke injury is not yet known. Similarly, it is hypothesized that children are susceptible to long term effects from wildfire smoke exposure. Prior research demonstrates when children are exposed to chronic air pollution (non-wildfire sources) during susceptible periods of childhood they develop significantly decreased FEV1.