A case-crossover study of short-term air pollution exposure and the risk of stillbirth in California, 1999-2009

Varada Sarovar; Brian J Malig; Rupa Basu

doi:10.1016/j.envres.2020.110103

A case-crossover study of short-term air pollution exposure and the risk of stillbirth in California, 1999-2009

Environ Res. 2020 Dec:191:110103. doi: 10.1016/j.envres.2020.110103. Epub 2020 Aug 23.

Authors

Varada Sarovar¹, Brian J Malig², Rupa Basu³

Affiliations

¹ Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA, USA; Division of Biostatistics, School of Public Health, UC Berkeley, Berkeley, CA, USA.
² Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA, USA. Electronic address: Brian.Malig@oehha.ca.gov.
³ Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, CA, USA.

PMID: 32846172
DOI: 10.1016/j.envres.2020.110103

Abstract

Background: Associations between ambient air pollution and stillbirth have recently been explored, but most studies have focused on long-term (trimester or gestational averages) rather than short-term (within one week) air pollution exposures.

Objective: To evaluate whether short-term exposures to criteria air pollutants are associated with increased risk of stillbirth.

Methods: Using air pollution and fetal death certificate data from 1999 to 2009, we assessed associations between acute prenatal air pollution exposure and stillbirth in California. In a time-stratified case-crossover study, we analyzed single day and/or cumulative average days (up to a 6 day lag) of exposure to fine (PM_2.5) and coarse particles (PM_10-2.5), ozone (O₃), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and carbon monoxide (CO) for mothers estimated to reside within 10 km of a pollution monitor based on reported zip code. We also examined potential confounding by apparent temperature or co-pollutants, and effect modification by maternal demographic factors, fetal sex, gestational age, and cause of stillbirth.

Results: Stillbirth cases in the primary analyses ranged between 1,203 and 13,018, depending on the pollutant. For an IQR increase in SO₂ (lag 4), O₃ (lag 4), and PM_10-2.5 (lag 2), we found a 2.8% (95% confidence interval (CI) 0.2%, 5.5%), 5.8% (95% CI 1.6%, 10.1%), and 6.1% (95% CI 0.1%, 12.4%) increase in the odds of stillbirth, respectively. Additional adjustment by apparent temperature had little effect on the SO₂ association but slightly attenuated O₃ (adjusted % change: 4.2% (95% CI -0.2%, 8.9%) and PM_10-2.5 (5.7% (95% CI -1.1%, 13.0%)) associations, while other co-pollutants had minimal impact. Associations were observed specifically for stillbirths from obstetric complications and in women with higher educational attainment.

Conclusions: This study provides evidence for associations between prenatal short-term air pollution exposure, specifically SO₂, O₃_, and PM_10-2.5, and stillbirth in California and warrants replication of findings in other settings.

Keywords: Air pollution; Ozone; Particulate matter; Stillbirth; Sulfur dioxide.

MeSH terms

Air Pollutants* / adverse effects
Air Pollutants* / analysis
Air Pollution* / adverse effects
Air Pollution* / analysis
California / epidemiology
Cross-Over Studies
Environmental Exposure / adverse effects
Female
Humans
Nitrogen Dioxide / analysis
Ozone* / analysis
Particulate Matter / adverse effects
Particulate Matter / analysis
Pregnancy
Stillbirth / epidemiology
Sulfur Dioxide / analysis
Sulfur Dioxide / toxicity

Substances

Air Pollutants
Particulate Matter
Sulfur Dioxide
Ozone
Nitrogen Dioxide