A March 8, 2018 in NEJM looks at the potential health effects of the smokes form wildfires. This Perspective article was entitield “The New England Journal of Medicine — Where There’s Wildfire, There’s Smoke.”
This article looks at the increased number of wildfires and their potential health effects. The recent Napa wildfires
Fine particles are regulated by the EPA because there is robust epidemiologic evidence of associations between short-term exposures to PM2.5 and cardiopulmonary mortality, as well as increased risk of acute respiratory and cardiovascular outcomes, including exacerbations of asthma and chronic obstructive pulmonary disease, acute lower respiratory tract infections, myocardial infarction, stroke, and arrhythmias.2 In addition, adverse neurologic and metabolic outcomes have also been associated with chronic exposure to PM2.5. There is some controversy about whether wood-smoke PM2.5 is as toxic as that generated by combustion of fossil fuels in motor vehicle engines and power plants. Recent reviews of the literature on community health effects from wildfire smoke found strong support for an association with respiratory morbidity, with less clear evidence of a link to cardiovascular outcomes.3,4 Mental health can also be affected.4 The groups most susceptible to the adverse health effects of PM2.5 are the very young and people with preexisting cardiovascular or respiratory disease, but older children and adults are also at risk.
Particulate matter (PM) — typically a mixture of solid particles and liquid droplets — is the principal pollutant of health concern from wildfire smoke for the relatively short-term exposures (hours to weeks) typically experienced by the public. Most PM in wood smoke is very small (0.4 to 0.7 μm), and particles of this size can be inhaled into the alveoli. The 24-hour air-quality standard set by the U.S. Environmental Protection Agency (EPA) for fine particles (PM2.5, particles smaller than 2.5 μm in mass median aerodynamic diameter) is 35 μg per cubic meter. For comparison, during the Sonoma–Napa wildfires in October 2017, the air quality in terms of PM2.5 was the worst that has ever been recorded in the San Francisco Bay area, with 24-hour concentrations exceeding 200 μg per cubic meter in Napa and 70 μg per cubic meter in Oakland on October 13.1
The practice of public health involves analysis of threats to a population’s health followed by recommendations for efforts that communities can make to address the threats. Catastrophic wildfires are indeed an increasingly important threat to public health. In addition to global warming and drought, a risk factor for large wildfires in the western United States is a legacy of fire suppression that has allowed overgrowth of underbrush and small trees in forests where periodic lightning-sparked wildfires are part of the natural ecosystem. Worldwide, as populations grow, housing development has created greater urban–wildland interface, straining fire-suppression resources.