The Associations Between Clinical Respiratory Outcomes and Ambient Wildfire Smoke Exposure Among Pediatric Asthma Patients at National Jewish Health, 2012–2015

Abstract

Wildfires are a growing threat in the United States. At a population level, exposure to ambient wildfire smoke is known to be associated with severe asthma outcomes such as hospitalizations. However, little work has been done on subacute clinical asthma outcomes, especially in sensitive populations. This study retrospectively investigated associations between ambient wildfire smoke exposure and measures of lung function and asthma control, Forced Expiratory Volume in 1 Second (FEV1) and the Asthma Control Test (ACT) and Children's Asthma Control Test (CACT) test scores, during nonurgent clinic visits. The study population consisted of pediatric asthma patients (ages 4–21; n = 1,404 for FEV1 and n = 395 for ACT/CACT) at National Jewish Health, a respiratory referral hospital in Denver, Colorado, and therefore represents a more severe asthma phenotype than the general pediatric asthma population. Wildfire smoke‐related PM2.5 at patients' residential ZIP codes was characterized using satellite‐derived smoke polygons from NOAA's Hazard Mapping System combined with kriging of ground‐based U.S. EPA monitors. Mixed effect models were used to estimate associations between clinical outcomes and smoke PM2.5 exposure, controlling for known risk factors and confounders. Among older children aged 12–21 we found that wildfire PM2.5 was associated with lower FEV1 the next day but higher FEV1 the day after. We found no associations between wildfire PM2.5 and FEV1 in younger children or between wildfire PM2.5 and asthma control measured by the ACT/CACT in all ages. We speculate that rescue medication usage by older children may decrease respiratory symptoms caused by wildfire smoke.

Particulate matter and emergency visits for asthma: a time-series study of their association in the presence and absence of wildfire smoke in Reno, Nevada, 2013–2018

“…However, it is also possible that patients with asthma change their behavior in other ways that would ameliorate the harmful effects of wildfire smoke, such as increasing their use of rescue medications. Lipner et al [32] observed that lung function in children aged 12-21 years initially decreased following a smoke exposure event (at a 1 day lag) but subsequently increased to above normal (at a 2 day lag). They speculated that this was due to older children effectively managing their symptoms using rescue medications.…”

“…Thus, there appears to be factors other than increased PM concentration that contribute to the increased harmfulness of wildfire smoke. More research is needed to understand these factors, but current research suggests that the harmfulness of wildfire PM may be affected by fuel source and burn rate [24], ambient temperature [26], behavioral changes [31][32][33], and smoke transport distance [23].…”

Impact of Wildfire Smoke on Adverse Pregnancy Outcomes in Colorado, 2007–2015

“…Wildfire smoke PM 2.5 and non-smoke PM 2.5 were jointly characterized using a previously published method [28] that has been used in a prior health study [29]. This method combines NOAA’s satellite imagery-based Hazard Mapping System [30,31,32] to determine daily smoke plume extent with spatial interpolation of ground-based PM 2.5 monitor values downloaded from the US EPA Air Quality System (AQS).…”

Particulate matter and emergency visits for asthma: a time-series study of their association in the presence and absence of wildfire smoke in Reno, Nevada, 2013-2018

“…Lipner et al [32] observed that lung function in children aged 12-21 initially decreased following a smoke exposure event (at a 1 day lag) but subsequently increased to above normal (at a 2 day lag). They speculated that this was due to older children effectively managing their symptoms using rescue medications.…”

“…Thus, there appears to be factors other than increased PM concentration that contribute to the increased harmfulness of wildfire smoke. More research is needed to understand these factors, but current research suggests that the harmfulness of wildfire PM may be affected by fuel source and burn rate [24], ambient temperature [26], behavioral changes [31][32][33], and smoke transport distance [23]. Tables Table 1 -Daily mean, range, and standard deviation for asthma visits, PM, and weather factors.…”