A recent study may contribute to explaining why autism spectrum disorder (ASD) rates are rising so rapidly in the US. The CDC reports that 1 in 36 children have autism spectrum disorder as of 2020!! Researchers and physicians agree that things in the environment (e.g., pesticides) are playing a role in this increase.
Even though the study was conducted in mice, it examined the impact of pesticides called pyrethroids on neurological development. They found that even at low levels that humans are typically exposed to, there were neurological effects on mice who were exposed during pregnancy. Their behaviors were altered in a negative way, for example an increase in repetitive behaviors.
Pyrethroids are being used in increasing amounts in the US for all sorts of insect treatments, both inside and outside of homes. It's very frequently used against mosquitos. Studies find that 70 to 80% of the US population have pyrethroid breakdown products (metabolites) in the blood. This is because we are exposed to chronic low levels - whether in the air, in water, around our homes or workplace.
The researchers wrote in the published research that scientists are especially concerned with pyrethroid exposure because it has a harmful effect on fetal development in both humans and animals. Studies are finding links from pyrethroid exposure during pregnancy or infancy and developmental delays.
"Critically, evidence from recent epidemiology and longitudinal studies suggests that ambient prenatal exposure to pyrethroid pesticides poses a risk for autism, developmental delay, and neurodevelopmental disorders in general. Analysis of data from the CHARGE study showed a significant increase in risk for either ASD or developmental delay from exposure during pregnancy to pyrethroid pesticides being applied up to 1.5 km from the home. A regional study in New York showed an association between areas where aerial application of pyrethroid pesticides was used, and ASD and developmental delay prevalence in the area. Additionally, the presence of pyrethroid metabolites in blood or urine correlates with risk for ADHD in children."
Bottom line: Avoid using pyrethroids around the home and yard. Look into IPM (Integrated Pest Management) or organic and natural ways to deal with pests. Pyrethroids are also toxic to bees, and we need bees. Synthetic pyrethroids (which is what is commonly used) are not like natural extracts from the chrysanthemum flower, and don't let someone tell you they are.
Excerpts from Medical Xpress: Research links common insecticide to neurodevelopmental disorders
A new study from The University of Toledo suggests early exposure to a common class of insecticides called pyrethroids may increase the risk of autism and other developmental disorders, even at levels currently recognized as safe by federal regulators.
The findings, which come from a study of mice, were published in PNAS Nexus.
Pyrethroids are some of the most widely used insecticides in the country, appearing in both consumer products and industrial preparations.
"If you have someone who comes and sprays in your house, this is likely what they're spraying. It's used in landscaping, it's what they fog in the streets for mosquitos. It's everywhere," said Dr. James Burkett, an assistant professor of neuroscience in the UToledo College of Medicine and Life Sciences and the paper's corresponding author. "Our study, however, adds to the evidence that these chemicals might not be as safe for children and pregnant women as we once believed."
Interest in a possible link between autism and pyrethroids has grown after several epidemiological studies documented higher rates of neurodevelopmental disorders in areas where the pesticides were used.
The new UToledo-led research sought to build on those population-based studies by analyzing the specific behavioral changes attributable to low-level exposure to pyrethroids.
Working with a team that included scientists from Columbia, Emory, and the University of Southern California, Burkett examined the offspring of female mice who were exposed to small doses of the pyrethroid insecticide deltamethrin before, during and immediately after pregnancy.
The researchers found those mice exhibited increased hyperactivity and repetitive behaviors, less vocalization, and were more likely to fail basic learning tests compared to controls. The young mice also experienced disruptions in their dopamine system.
"These are all similar to symptoms human patients with neurodevelopmental disorders might have," Burkett said. "We are not saying these mice have autism or that they have ADHD. That's not the goal here. What we are saying is that something in their brain has been altered by this exposure and it's resulting in the same kinds of behaviors that we see in children with autism."
"We have reduced our exposures to many classes of dangerous pesticides over the past few decades through restrictions and regulations." Miller said. "This study adds to a growing body of literature that the widely used pyrethroids are not without adverse effects and should be further evaluated for their safety."