Effects of Wildfire Smoke on Volatile Organic Compound (VOC) and PM2.5 Composition in a United States Intermountain...

With warmer and drier climate there has been an increase in wildfire events in the Northwest US, posing a potential health risk to downwind communities. The Lewis-Clark Valley (LCV), a small metropolitan area on the Washington/Idaho border in the United States Intermountain West region, was studied over the time period of 2017-2018. The main objective was to determine the community's exposure to particulate matter (PM2.5) and volatile organic compounds (VOCs) during wildfire smoke events and estimate the associated health risk. VOCs were analyzed in the LCV using sorbent tube sampling and thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) during several local smoke events in the 2017-2018 fire seasons. PM_2.5 measurements were obtained from nearby agency monitors. PM_2.5 reached up to 200 μg/m³ in 2017 and over 100 μg/m³ in 2018 in the LCV and was observed to be increasing at a rate of 0.10 μg/m³/yr over the past two decades. Benzene, a carcinogen and air toxic, was measured with concentrations up to 11 μg/m³, over ten times the normal level in some instances in the LCV. The health risk in the LCV from benzene was calculated at 7 extra cancers per million for lifetime exposure and 13 extra cancers per million considering all air toxics measured. The other cities monitored showed similar lifetime cancer risk due to benzene of about 6-7 extra cancers per million. This work is important as it measures ground-level exposures of VOCs and demonstrates decreases in PM air quality over time in the region.