# Prenatal Exposure to Wildfire and Autism in Children

## TL;DR

Exposure to wildfire smoke during pregnancy, especially in the third trimester, may increase the risk of autism in children.

## Contribution

This study identifies a potential link between prenatal wildfire smoke exposure and autism risk, focusing on exposure duration and timing.

## Key findings

- Increased wildfire smoke exposure days in the third trimester correlated with higher autism risk.
- Nonmovers had the strongest association between wildfire exposure and autism diagnosis.
- Mean PM2.5 concentration alone was not significantly linked to autism risk.

## Abstract

Chronic health effects
of wildfire PM2.5 on neurodevelopmental
outcomes are largely unknown. Therefore, the effects of wildfire PM2.5 on autism were assessed in a southern California-based
pregnancy cohort using Cox proportional hazard models. Exposure was
estimated from 2006 to 2014 at maternal addresses across pregnancy
and individual trimesters using three metrics: (1) mean wildfire PM2.5 concentration, (2) number of days of smoke exposure, and
(3) number of waves of smoke exposure. Analysis was restricted to
days over specific PM2.5 concentration thresholds (3 and
5 μg/m3). Nonmovers during pregnancy (75% of cohort)
were assessed in sensitivity analyses. There were 3356 autism diagnoses
by age 5. Autism risk was associated with increased number of wildfire-exposed
days during the third trimester and was strongest for nonmovers. Nonmover
hazard ratios (HR) with exposure to 1–5, 6–10, and >10
wildfire days in the third trimester (compared to none) were 1.108
(95% CI: 1.010,1.215), 1.118 (0.957,1.307), and 1.225 (1.043,1.440),
respectively. HR per wildfire wave increase (>3 μg/m3 for 2 consecutive days) during the third trimester were 1.073
(1.009,1.140)
and 1.267 (1.054,1.205) for the entire cohort and nonmovers, respectively.
There was no association with the mean wildfire PM2.5 concentration
alone. Prenatal exposure to wildfire smoke may increase risk of autism
among children.