Associations between wildfire smoke exposure during pregnancy and risk of preterm birth in California

Sam Heft-Neal; Anne Driscoll; Wei Yang; Gary Shaw; Marshall Burke

doi:10.1016/j.envres.2021.111872

Associations between wildfire smoke exposure during pregnancy and risk of preterm birth in California

Environ Res. 2022 Jan:203:111872. doi: 10.1016/j.envres.2021.111872. Epub 2021 Aug 14.

Authors

Sam Heft-Neal¹, Anne Driscoll², Wei Yang³, Gary Shaw³, Marshall Burke⁴

Affiliations

¹ Center on Food Security and the Environment, Stanford University, Stanford, CA, USA. Electronic address: sheftneal@stanford.edu.
² Center on Food Security and the Environment, Stanford University, Stanford, CA, USA.
³ Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, USA.
⁴ Center on Food Security and the Environment, Stanford University, Stanford, CA, USA; Department of Earth System Science, Stanford University, Stanford, CA, USA; National Bureau of Economic Research, Cambridge, MA, USA.

PMID: 34403668
DOI: 10.1016/j.envres.2021.111872

Abstract

There is limited population-scale evidence on the burden of exposure to wildfire smoke during pregnancy and its impacts on birth outcomes. In order to investigate this relationship, data on every singleton birth in California 2006-2012 were combined with satellite-based estimates of wildfire smoke plume boundaries and high-resolution gridded estimates of surface PM_2.5 concentrations and a regression model was used to estimate associations with preterm birth risk. Results suggest that each additional day of exposure to any wildfire smoke during pregnancy was associated with an 0.49 % (95 % CI: 0.41-0.59 %) increase in risk of preterm birth (<37 weeks). At sample median smoke exposure (7 days) this translated to a 3.4 % increase in risk, relative to an unexposed mother. Estimates by trimester suggest stronger associations with exposure later in pregnancy and estimates by smoke intensity indicate that observed associations were driven by higher intensity smoke-days. Exposure to low intensity smoke-days had no association with preterm birth while an additional medium (smoke PM_2.5 5-10 μg/m³) or high (smoke PM_2.5 > 10 μg/m³) intensity smoke-day was associated with an 0.95 % (95 % CI: 0.47-1.42 %) and 0.82 % (95 % CI: 0.41-1.24 %) increase in preterm risk, respectively. In contrast to previous findings for other pollution types, neither exposure to smoke nor the relative impact of smoke on preterm birth differed by race/ethnicity or income in our sample. However, impacts differed greatly by baseline smoke exposure, with mothers in regions with infrequent smoke exposure experiencing substantially larger impacts from an additional smoke-day than mothers in regions where smoke is more common. We estimate 6,974 (95 % CI: 5,513-8,437) excess preterm births attributable to wildfire smoke exposure 2007-2012, accounting for 3.7 % of observed preterm births during this period. Our findings have important implications for understanding the costs of growing wildfire smoke exposure, and for understanding the benefits of smoke mitigation measures.

Keywords: Pollution; Pregnancy; Preterm birth; Smoke; Wildfire.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Air Pollutants* / adverse effects
Air Pollutants* / analysis
Air Pollution*
California / epidemiology
Female
Humans
Infant, Newborn
Maternal Exposure / adverse effects
Particulate Matter / adverse effects
Particulate Matter / analysis
Pregnancy
Premature Birth* / epidemiology
Premature Birth* / etiology
Smoke / adverse effects
Wildfires*

Substances

Air Pollutants
Particulate Matter
Smoke