Prenatal Exposure to Wildfire and Autism in Children

Area of Science:

• Environmental Health
• Neurodevelopmental Disorders
• Epidemiology

Background:

• Chronic health impacts of wildfire fine particulate matter (PM2.5) on neurodevelopment remain largely unknown.
• Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition with potential environmental risk factors.

Purpose of the Study:

• To assess the association between prenatal exposure to wildfire PM2.5 and autism diagnoses in a Southern California pregnancy cohort.
• To investigate specific exposure metrics including concentration, number of exposed days, and smoke waves.

Main Methods:

• Utilized Cox proportional hazard models on a pregnancy cohort (2006-2014) with 3356 autism diagnoses by age 5.
• Estimated exposure using three wildfire PM2.5 metrics: mean concentration, days of smoke exposure, and waves of smoke exposure.
• Conducted sensitivity analyses for non-moving pregnant individuals and restricted analysis to PM2.5 concentration thresholds (3 and 5 μg/m³).

Main Results:

• Increased autism risk was associated with a higher number of wildfire-exposed days during the third trimester.
• The association was strongest for non-moving individuals, with hazard ratios (HR) up to 1.225 for >10 exposed days.
• Risk increased per wildfire wave exposure during the third trimester (HR 1.073 for all, 1.267 for non-movers).
• No association was found with mean wildfire PM2.5 concentration alone.

Conclusions:

• Prenatal exposure to wildfire smoke, particularly during the third trimester, may elevate the risk of autism in children.
• Exposure metrics related to smoke presence (days, waves) were more strongly associated with autism risk than average concentration.
• Further research is warranted to elucidate the mechanisms linking wildfire smoke exposure and neurodevelopmental outcomes.