The study, published in Environmental Science & Technology, analysed more than 200,000 births in Southern California from 2006 to 2014 to explore a possible link between prenatal wildfire smoke exposure and later autism diagnoses. Researchers report that exposure during the third trimester was associated with higher odds of an autism diagnosis by age five.
The strongest association occurred among mothers exposed to more than ten days of wildfire smoke in the final three months of pregnancy; children in that group had a 23% higher risk of an autism diagnosis compared with children whose mothers were never exposed. The authors stress the finding is not conclusive but complements earlier studies that connect prenatal air pollution and autism, with heavy metals in particles often suggested as a possible mechanism.
Wildfires produce short spikes of concentrated pollution: burning vegetation and buildings release toxic metals and other pollutants, and fine particles in smoke can cause inflammation and stress when inhaled. In this study, mothers of children later diagnosed with autism tended to be older, more often on their first pregnancy, and had higher rates of pre-pregnancy diabetes and obesity; four times as many boys as girls received autism diagnoses.
The research was led at Tulane University and conducted with Kaiser Permanente Southern California, the University of Southern California, Harvard University and Sonoma Technology, Inc. Corresponding author Mostafijur Rahman and lead author David Luglio say further study is needed, and that understanding any relationship is important as climate change increases wildfire frequency and intensity.
Difficult words
- prenatal — relating to the period before a baby is born
- trimester — a three-month period during a pregnancythird trimester
- exposure — being in contact with something that may harm
- odds — the likelihood or chance of something happening
- particle — very small piece of solid or liquid matterparticles
- inflammation — reaction of the body causing redness and swelling
- mechanism — a process that explains how something happens
- intensity — the strength or power of an event or force
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- What public health measures could help protect pregnant people during periods of heavy wildfire smoke? Give reasons based on the study.
- Why do the authors say further study is needed before concluding a causal link?
- How might the individual risk factors mentioned in the article (older maternal age, first pregnancy, pre-pregnancy diabetes, obesity) influence research on prenatal exposure and autism?
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