The joint effect of air pollution exposure and copy number variation on risk for autism.
Dokyoon Kim, Heather Volk, Santhosh Girirajan and 11 others
PMID 28448694WHAT IT FOUND
Children with high genetic copy number burden and high ozone exposure had substantially elevated autism risk compared to those with low levels of both.
Ozone alone showed no association with autism risk in children without high genetic susceptibility.
Key findings
01The combination of high ozone exposure and high copy number duplication burden was associated with a nearly three-fold greater risk of autism compared to low levels of both factors.
02Ozone exposure alone, or in children without high genetic susceptibility, showed essentially no association with autism risk.
03High PM 2.5 and PM 10 exposure was associated with autism risk specifically in children with low copy number burden, particularly involving deletions.
STILL TO COME
How it was doneWhat they found
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What it does not show
The sample size of 305 children is small, which limits statistical power for detecting subtle interactions and prevents analysis of narrower time windows like specific trimesters. The study did not distinguish between inherited and de novo copy number variants, so it cannot determine if air pollution altered the genetic burden or if the interaction occurred on a pre-existing genetic background. Only a few confounding factors (maternal education, child sex, race/ethnicity, and Regional Center) were controlled for, leaving open the possibility that other unknown risk factors influenced the results. Ozone measures were highly correlated over time, making it difficult to pinpoint a specific critical period of vulnerability. The analysis involved many comparisons (multiple pollutants, time periods, and genetic measures), increasing the chance that the significant ozone finding could be a statistical fluctuation.
Declared interests
Not explicitly stated in the provided text, but the study is part of the CHARGE project at the UC Davis MIND Institute, funded by the National Institute of Environmental Health Sciences (NIEHS) and the National Institute of Mental Health (NIMH).
The easy way to misread this
Do not interpret the strong association between ozone and autism as evidence that ozone causes autism in the general population. The increased risk was observed only in children with a specific high genetic susceptibility (high copy number duplication burden). Ozone exposure alone showed no association with autism risk in children without this genetic profile.