Examining fine particulate matter and cause-specific morbidity during the 2017 North San Francisco Bay wildfires

Brian J Malig; David Fairley; Dharshani Pearson; Xiangmei Wu; Keita Ebisu; Rupa Basu

doi:10.1016/j.scitotenv.2021.147507

Examining fine particulate matter and cause-specific morbidity during the 2017 North San Francisco Bay wildfires

Sci Total Environ. 2021 Sep 15:787:147507. doi: 10.1016/j.scitotenv.2021.147507. Epub 2021 May 4.

Authors

Brian J Malig¹, David Fairley², Dharshani Pearson³, Xiangmei Wu³, Keita Ebisu³, Rupa Basu³

Affiliations

¹ Air and Climate Epidemiology Section, Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA, USA. Electronic address: Brian.Malig@oehha.ca.gov.
² Bay Area Air Quality Management District, San Francisco, CA, USA.
³ Air and Climate Epidemiology Section, Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA, USA.

PMID: 35142610
DOI: 10.1016/j.scitotenv.2021.147507

Abstract

Background: Recent increases in wildfire frequency and severity necessitate better understanding of health effects of wildfire smoke to protect affected populations.

Objectives: We examined relationships between fine particulate matter (PM_2.5) and morbidity during wildfires in California, and whether those relationships differed during the fire compared to a similar non-fire period.

Methods: For nine San Francisco Bay Area counties, daily county-level diagnosis-specific counts of emergency department visits (EDVs) and hospitalizations were linked with county-level estimates of daily mean PM_2.5 during the October 2017 Northern California wildfires and similar October days in 2015, 2016, and 2017. Associations were estimated using Poisson regression.

Results: The median difference between county PM_2.5 during the fire versus the non-fire period was 23.4 μg/m³, with days exceeding 80 μg/m³ in some counties. Over the entire study period, PM_2.5 was most consistently linked to EDVs for respiratory disease (RR_EDV(lag0) per 23.4 μg/m³ increase: 1.25, 95% CI: 1.21, 1.30), asthma, chronic lower respiratory disease (CLRD; RR_EDV(lag0): 1.18, 95% CI: 1.10, 1.27), and acute myocardial infarction (RR_EDV(lag0): 1.14, 95% CI: 1.03, 1.25). Increases in acute upper respiratory infections and decreases in mental/behavioral EDVs were observed but were sensitive to model specification, specifically the inclusion of time-related covariates. Comparing fire and non-fire period EDV associations, we observed indications that PM_2.5 during the fire was more strongly associated with asthma (RR_lag0: 1.46, 95% CI: 1.38, 1.55) compared to non-fire period PM_2.5 (RR_lag0: 0.77, 95% CI: 0.55, 1.08)_, and the opposite observed for dysrhythmia, with the asthma difference being particularly robust to model choice. For hospitalizations, the most robust PM_2.5 relationships were positive associations with respiratory, CLRD, and diabetes, and inverse associations with pneumonia. Respiratory and CLRD effect estimates were generally similar or smaller than for EDVs.

Conclusions: Elevated short-term PM_2.5 levels from wildfire smoke appears to impact respiratory and other health domains.

Keywords: Cardiovascular disease; Emergency department visits; Hospitalizations; PM2.5; Respiratory disease; Wildfires.

MeSH terms

Air Pollutants* / adverse effects
Air Pollutants* / analysis
Environmental Exposure
Humans
Morbidity
Particulate Matter / adverse effects
Particulate Matter / analysis
Respiratory Tract Diseases*
San Francisco / epidemiology
Smoke
Wildfires*

Substances

Air Pollutants
Particulate Matter
Smoke