The new DDTautism link

Pregnant women with signs of high DDT exposure in their blood are more likely to have children with autism spectrum disorder, a just-released study of Finnish women has found. DDT (dichlorodiphenyltrichloroethane) was widely used in Europe in the 1940s to kill disease-carrying mosquitos, but the insecticide was banned in many Western countries in the 1970s and 1980s (including New Zealand, in 1989). But residues can persist in the food chain for decades and have been found to pass across the placenta to the fetus.

A team at Columbia University in New York analysed blood samples taken from more than a million pregnant women in Finland between 1983 and 2005. They found levels of DDE – a breakdown product of DDT – were higher in those who went on to have children with ASD. The findings, published last month in the American Journal of Psychiatry, suggest high exposure to DDT increases the likelihood of having a child with autism by about a third.

The results are not conclusive – some pregnant women with high levels of DDE did not go on to have children with ASD – but further studies are expected to be undertaken to see if DDT is a cause of autism or linked in another way. In the meantime, an initiative to rid New Zealand of DDT and other obsolete pesticides containing persistent organic pollutants is in its final stages. Since 2015, The Great DDT Muster, funded by the Waste Minimisation Fund and managed by the Hastingsbased 3R Group, has collected some 20 tonnes of dangerous chemicals from sheds and garages on rural properties and, alarmingly, in suburban kitchen cupboards – in the 1960s, DDT was promoted as part of a pest-eradication application before vacuuming.

DDT was used in household insecticides.