Exposure to toxic pesticides before birth may not be tied to autism symptoms after all, according to new research.
Autism is now diagnosed in one in 31 children in the United States, up sharply from one in 150 in the early 2000s, prompting scientists to look more closely at possible causes as well as better ways to identify the condition earlier.
Environmental pollution has been a major focus of that search, including pesticides used in agriculture that can make their way into the food supply, especially through fruits and vegetables.
Researchers have suspected for years that such chemicals could contribute to brain inflammation or disrupt neurotransmitters including dopamine and serotonin, potentially influencing traits associated with autism, such as communication challenges and hyperactivity.
But a new study of mother-child pairs exposed during pregnancy to organophosphate pesticides — a class of chemicals known to be toxic to humans — found no significant link between those exposures and autism-related traits in children, researchers at NYU Langone in New York City reported.
The reason for the findings is not yet clear, though the researchers suggested one possibility: the health benefits of eating plenty of fruits and vegetables, including lower inflammation, could help counterbalance potential pesticide-related risks.
The team cautioned that the study does not prove pesticides are safe for pregnant women or children, but said the results indicate the chemicals may not be connected to autism in the way some earlier research has suggested.
Further research, they added, could help shape future rules and restrictions on pesticide use, particularly because these chemicals have also been associated with neurological diseases such as Parkinson’s disease and with several types of cancer.
Researchers in New York have found that pesticides, which have long been linked to autism, may not cause the condition’s hallmark characteristics(stock image)
‘While we know that organophosphate pesticides can harm the developing brain, they were not a major driver of characteristics seen in autism at the relatively low exposure levels we observed,’ Dr Haleigh Cavalier, lead study author and doctoral student at NYU Langone Health’s Departments of Population Health and Pediatrics, said.
‘These results should not be interpreted to mean that such pesticides are safe, nor do they rule out autism-related risks at higher exposures or among more vulnerable groups.’
The study, published in JAMA Pediatrics, looked at data from 3,339 pairs of mothers and children enrolled at 20 medical centers in the US National Institutes of Health’s Environmental Influences on Child Health Outcomes (ECHO) Program, a nationwide study that examines the impact of environmental, social and biological factors on a child’s health.
The researchers measured levels of metabolites, byproducts of chemical breakdown in the body, in urine samples during pregnancy. The tests revealed 99 percent of mothers had detectable levels of organophosphate pesticides in their urine.
The team then looked for associations between metabolite levels and how the children scored on the Social Responsiveness Scale, a 65-item questionnaire designed to identify social communication issues and autism-related traits such as eye contact avoidance, difficulty understanding people’s emotions and needing to follow specific routines.
Children were evaluated between five and seven years old on average.
There were no consistent associations between the levels of metabolites detected in urine and autism-related traits when adjusting for sex and dietary factors, the study found.
The authors note that one limitation is that metabolites are short-lived in the human body, so exact levels can vary over time. Additionally, individual metabolism can impact levels.
This means the markers may not provide the full picture in terms of pesticide exposure, but additional studies may strengthen the findings.
‘Our results demonstrate that there is still much more to be learned about autism,’ Dr Akhgar Ghassabian, senior study author and associate professor in the Department of Pediatrics at the NYU Grossman School of Medicine, said.
‘Careful, long-term research can help clarify which environmental exposures matter most so that communities and policymakers can make more informed decisions.’
