Alan S. Brown, M.D.
Mothers with high levels of the pesticide DDT in their blood during pregnancy are more likely to bear children who develop autism, according to an NIEHS-funded study. The study was the first to connect DDT with autism using a direct measure of exposure in maternal blood.
The researchers measured levels of DDT and polychlorinated biphenyl (PCB) metabolites in blood samples collected during the Finnish Prenatal Study of Autism. The study involved more than a million women and children born between 1987 and 2005 in Finland. The scientists compared 778 children diagnosed with autism, and their mothers, to 778 child-mother pairs without an autism diagnosis. The children with and without autism were matched for date of birth, sex, and place of residence.
The analysis revealed that mothers with DDT metabolite levels in their blood in the highest 25th percentile were 32 percent more likely than women with lower DDT levels to give birth to children who developed autism. The likelihood of having a child with autism accompanied by intellectual disability was twice as high in mothers with elevated DDT levels compared with those with lower levels. They found no association between PCB metabolites and autism.
The researchers offered two possible explanations for their observation that maternal exposure to DDT was related to autism but maternal PCB exposure was not. Low birth weight and premature birth, which are known risk factors for autism, have both been previously linked to maternal exposure to DDT, but not to PCBs. Maternal DDT exposure has also been shown to inhibit androgen receptor binding, which is a key process to neurodevelopment.
Citation: Brown AS, Cheslack-Postava K, Rantakokko P, Kiviranta H, Hinkka-Yli-Salomaki S, McKeague IW, Surcel HM, Sourander A. 2018. Association of maternal insecticide levels with autism in offspring from a national birth cohort. Am J Psychiatry doi: 10.1176/appi.ajp.2018.17101129. [Online 16 Aug 2018].