Autism is a developmental disorder that affects approximately 1 in 160 children, according to the World Health Organization, and its symptoms usually begin in childhood and continue into adolescence and adulthood.
Exactly what causes autism and how it develops is still up for debate, but it is widely recognized that there is likely an interaction between environmental and genetic factors.
Recently, scientists from Columbia University’s Mailman School of Public Health in New York City joined forces with researchers from the University of Turku and the National Institute of Health and Welfare, both in Finland to investigate whether there could be links between pesticide exposure and autism risk. In particular, they were interested in dichlorodiphenyltrichloroethane (DDT).
What is DDT?
Initially synthesized in 1874, DDT kills a wide range of disease vectors and was used during World War II to control typhus and malaria in Europe and the South Pacific. It is such an effective pesticide that typhus has almost been eradicated in parts of Europe. By 1945, it was widely used in both private homes and agricultural businesses.
Although legitimate and effective safety concerns were raised, DDT was eventually banned in many countries.
However, just stopping the use of DDT did not remove the chemical . DDT is a persistent organic pollutant, which means that it decomposes slowly over decades and easily enters the food chain. Over time, this chemical builds up in the body, especially in adipose tissue.
Although the exact impact of long-term exposure to DDT on human health has not yet been confirmed, it is believed to be an endocrine disruptor and a possible carcinogen.
Because short-term exposure to the pesticide is considered relatively safe, it is still used to control mosquitoes and other pests in areas with particularly high rates of malaria, such as certain parts of sub-Saharan Africa.
Worryingly, DDT can cross the placenta. So if a woman already carries some of the pesticide, it can affect her unborn baby.
To find out if DDT is linked in any way to the development of autism in some people, they used data from the Finnish Prenatal Autism Study. The scientists analyzed serum samples from more than 750 children with autism and a large number of healthy control subjects.
The DDT-autism link
The team measured levels of p, p’-dichlor diphenyl dichloroethylene (DDE), a breakdown product of DDT. They found that a child’s risk of developing autism was one-third higher if his mother had elevated levels of DDE in her blood.
Similarly, the risk of a child having autism with intellectual disability more than doubled when the mother’s DDE levels were at the 75th percentile or higher.
The authors write that their findings ” provide the first biomarker-based evidence that maternal exposure to insecticides is associated with autism in the offspring. These chemicals are still present in the environment and are in our blood and tissues.” explains Alan S. Brown, leader of the work.
“Our findings suggest that prenatal exposure to DDT toxin can trigger autism,” he concludes.
According to experts, it is a partnership. Even after removing potential confounders, such as maternal age and previous psychiatric conditions, the findings remained highly significant.
Reference: Association of Maternal Insecticide Levels With Autism in Offspring From a National Birth Cohort Alan S. Brown, Keely Cheslack-Postava, Panu Rantakokko, Hannu Kiviranta, Susanna Hinkka-Yli-Salomäki, Ian W. McKeague, Heljä-Marja Surcel, Andre Sourander. American Journal of Psychiatry . 2018
