Determining the Impact of Wildland Fires on Ground Level Ambient Ozone Levels in California

Abstract

Wildland fire smoke is visible and detectable with remote sensing technology. Using this technology to assess ground level pollutants and the impacts to human health and exposure is more difficult. We found the presence of satellite derived smoke plumes for more than a couple of hours in the previous three days has significant impact on the chances of ground level ozone values exceeding the norm. While the magnitude of the impact will depend on characteristics of fires such as size, location, time in transport, or ozone precursors produced by the fire, we demonstrate that information on satellite derived smoke plumes together with site specific regression models provide useful information for supporting causal relationship between smoke from fire and ozone exceedances of the norm. Our results indicated that fire seasons increasing the median ozone level by 15 ppb. However, they seem to have little impact on the metric used for regulatory compliance, in particular at urban sites, except possibly during the 2008 forest fires in California.

The Measured Impact of Wildfires on Ozone in Western Canada From 2001 to 2019

“…Identification of wildfire‐impacted days using NOAA's Hazard Mapping System (HMS) reported increases in MDA8 values in the U.S. during wildfire periods ranging from 3 to 36 ppbv (Brey & Fischer, 2016; Pan & Faloona, 2022). The most similar study to this one measured the increase in O 3 in California across all times (i.e., not just the MDA8) between 2006 and 2016 from wildfires identified using the HMS (Cisneros et al., 2020). This study noted a median increase of 1.5 ppbv in O 3 for all years (except 2008, which increased a median amount of 7.8 ppbv) which is very comparable to our study with median values of 2 ppbv for all wildfire periods, and median values of 8 ppbv for O 3 measurements in the evening of smoke plumes transported an average of 12 hr, with PM 2.5 measurements above 50 μg/m 3 and below 100 μg/m 3 .…”

“…Statistical modeling has been previously used to understand the effect of wildfires on O 3 and can account for variability arising from changes in temperature, solar irradiance, relative humidity and more (Brey & Fischer, 2016; Cisneros et al., 2020; Gong et al., 2017). Briefly, these statistical methods relate the measured O 3 to factors which affect the O 3 mixing ratio to determine an unbiased baseline to compare to the measurements during wildfires.…”

Adverse Health Impacts of Outdoor Air Pollution, Including from Wildland Fires, in the United States: “Health of the Air,” 2018–2020

“…Because of a combination of climate change ( 9 – 11 ) and a century of fire suppression ( 12 ), wildfire seasons are lengthening and increasing in intensity, producing emissions that may soon counteract decades of regional PM 2.5 reductions ( 13 , 14 ). Primary pollutants emitted from wildland fires also contribute to the formation of downwind ground-level ozone (O 3 ), although conditions near fires may constrain O 3 formation ( 15 , 16 ). Because the Clean Air Act’s exceptional events rule excludes wildfire smoke from National Ambient Air Quality Standards attainment decisions, complete reliance on these standards cannot currently address issues of increasing adverse health impacts from wildland fires.…”