Rodent studies given to U.S. regulators by insecticide makers close to 20 years ago revealed the chemicals could be harmful to the animals’ brain development — data worrisome for humans exposed to the popular pesticides but not properly accounted for by regulators, according to a new research report published on Oct. 1.
The analysis examined five studies that exposed pregnant rats to various types of insecticides known as neonicotinoids (commonly called neonics). The studies found that the offspring born to the exposed rats suffered shrunken brains and other problems.
Statistically significant shrinkage of brain tissue was seen in the offspring of rats exposed to high doses of five types of neonics – acetamiprid, clothianidin, imidacloprid, thiacloprid, and thiamethoxam, the paper states.
The authors said the impacts on the brain appeared similar to the effects of nicotine, which they said is known to disrupt mammalian neurological development.
The animal studies also support the possibility of a link between neonic exposure and attention-deficit/hyperactivity disorder (ADHD), the authors said.
In most cases, the companies submitting the studies did not submit data for all dosage levels, leading the U.S. Environmental Protection Agency (EPA) to assume negative effects were only seen at the high dose, according to the study.
“We found numerous deficiencies in the Environmental Protection Agency (EPA)’s regulatory oversight and data analyses,” the authors state in the paper, published in the journal Frontiers in Toxicology.
The industry studies, which the EPA used to determine what neonic exposure levels are considered safe for humans, were not publicly available and were obtained through a Freedom of Information Act request.
“Consistently, effects were found at the high dose and EPA did not demand data for the lower doses, therefore leaving it unclear how little of a substance it takes to actually cause adverse effects such as reduced size of certain brain regions,” said Bill Freese, the science director for the environmental advocacy group Center for Food Safety and an author of the study.
The study found that the EPA consistently made determinations about what levels of neonic exposure were “safe” for humans without enough data to support its conclusions.
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