20
Jul
Insecticide Chlorpyrifos Interacts with Genes to Increase Autism Risk, Research Finds
(Beyond Pesticides, July 20, 2021) Chlorpyrifos exposure results in the expression of genetic mutations associated with autism spectrum disorder in a laboratory model, finds research published in Environmental Health Perspectives by scientists at Johns Hopkins Bloomberg School of Public Health. “This is a step forward in showing an interplay between genetics and environment and its potential role for autism spectrum disorder,” says study lead Lena Smirnova, PhD, a research associate in the Department of Environmental Health and Engineering at the Bloomberg School. The findings support reams of research already conducted that show strong associations between autism and exposure to hazardous environmental stressors like toxic pesticides.
Scientists conducted their study using a ‘brain organoid’ model, which is essentially a cluster of cells artificially grown in the lab from stem cells in order to mimic a developing human brain. These tests provide certain benefits over animal testing, as they are more relevant to human disease, and can be performed faster with less cost. The organoid model also represents an improvement on typical 2d cell-based models, increasing cell survival, shelf-life, and thus providing opportunity to model for later stages of brain development.
Brain organoids in this study carried a gene called CHD8, which regulates gene activity critical to brain development. With changes in CHD8 representing one of the strongest links to the risk of developing autism, the study aimed to understand whether chlorpyrifos exposure resulted in any of these alterations. Organoids were exposed to chlorpyrifos at four and eight weeks of development, representing a short term, high exposure scenario. “High-dose, short-term experimental exposures do not reflect the real-life situation, but they give us a starting point to identify genetic variants that might make individuals more susceptible to toxicants,” says Dr. Smirnova.
Exposure to chlorpyrifos at these times did result in measurable effects on CHD8 gene expression. Although the lab created brain organoids only carried a single copy of the CDH8 gene and less than the normal amount of CHD8 protein, chlorpyrifos nonetheless was able to lower its expression further. Researchers describe how this finding shows that environmental exposures can make pre-existing genetic problems even worse.
In addition to altering CHD8 expression, a range of other biomarkers in the brain organoid were identified as those usually found in autistic patients. “In this sense, we showed that changes in these organoids reflect changes seen in autism patients,” Dr. Smirnova says. “Now we can explore how other genes and potentially toxic substances interact.”
The findings provide a new way to quickly determine the effect of environmental exposures on gene expression. “The use of three-dimensional, human-derived, brain-like models like the one in this study is a good way forward for studying the interplay of genetic and environmental factors in autism and other neurodevelopmental disorders,” says study co-author Thomas Hartung, MD, PhD, professor and Doerenkamp-Zbinden Chair in the Bloomberg School’s Department of Environmental Health and Engineering.
The U.S. Centers for Disease Control and Prevention estimates that 1 in 54 children have been diagnosed with an autism spectrum disorder. Rates of autism have skyrocketed over the last several decades. While some of the rise can be explained by increased testing, and an expansion of the diagnostic criteria for the disorder, it is unable to entirely account for the increased cases. In 1997, 0.1% of children had autism, while in 2010 that number rose to 1%.
“The increase in autism diagnoses in recent decades is hard to explain—there couldn’t have been a population-wide genetic change in such a short time, but we also haven’t been able to find an environmental exposure that sufficiently accounts for it,” notes Dr. Hartung. “To me, the best explanation involves a combination of genetic and environment factors.”
This determination, and the present study’s findings, are supported by previous scientific literature. A 2018 study published in Pediatric Research reviewed a range of studies linking pesticides to autism and found evidence for an association in both laboratory and epidemiological research. Scientific studies have consistently found elevated rates of autism in areas of high pesticide use. A 2014 study from the University of California, Davis, found that pregnant women living near crops sprayed with organophosphates like chlorpyrifos increased the chance of their child being diagnosed with autism by 60%. For women in their second trimester, chlorpyrifos in particular increased the odds by 3.3x. Another class of insecticides, synthetic pyrethroids, increased autism risk by 87%. Likewise, communities with mosquito adulticide programs were found to be 37% more likely to have higher rates of autism spectrum disorders, according to a 2017 study. Fungicides have also been linked to autism disorders, and a separate study from California researchers connected autism to the herbicide glyphosate, insecticides chlorpyrifos and permethrin, the banned pesticide diazinon, the fumigant methyl bromide, and fungicide myclobutanil.
While some well-meaning health advocates focus on controversial studies relating vaccines to autism, the connection to pesticide exposure is well-researched, and likely a contributing factor to the rise of the disorder over the last several decades. More research is needed to further elucidate the connection, but there is enough evidence available to warrant a precautionary approach, and restrictions on hazardous autism-linked pesticides.
The U.S. Environmental Protection Agency will soon provide a response to a lawsuit urging it to ban all food uses of chlorpyrifos, but even if the agency announces agricultural use cancellations, the chemical will still remain available for golf courses and as mosquito adulticide. In the meantime, parents are taking their fight directly to product manufacturers, and are suing Corteva (DowDupont) for the brain damage and other developmental problems their children suffered while living near chlorpyrifos-treated fields.
Help stop the use of a chemical with strong links to autism by urging EPA to ban chlorpyrifos today. But don’t stop at chlorpyrifos – as banning its use is simply the first step in eliminating other autism-linked neurotoxic pesticides on the market. Tell EPA chlorpyrifos and all brain-damaging pesticides need to be banned immediately.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Environmental Health Perspectives, John Hopkins Bloomberg School of Public Health (press release)
Thank you for using organiods instead of animals in this research. I am autistic, and was exposed to termite poison (diazinon) during pregnancy. However, I do not consider autism to be a disease, or a disorder. I do not “suffer” from it. Autism is part of me. It is a neurodivergent difference.
July 21st, 2021 at 2:00 pm