Study Connects Neonicotinoids to Liver Damage Ignored by EPA
(Beyond Pesticides, January 11, 2022) Neonicotinoid insecticides can have detrimental effects on liver health, according to research published in the Journal of Hazardous Materials. While this is the first study to investigate how these chemicals harm the liver, there is increasing evidence that neonicotinoids, otherwise notorious for their effects on pollinators and aquatic life, can cause direct harm to human health. As the U.S. Environmental Protection Agency (EPA) continues to protect the pesticide industry from any measure of meaningful regulation around these hazardous products, the job falls to advocates to place pressure on elected officials to make the changes necessary to safeguard long-term health and well-being.
Scientists postulated that neonicotinoids are neither metabolized by the liver nor excreted by urine. To test that hypothesis, 201 individuals from a hospital in China were enrolled into a study. Of the enrolled, Â 81 were cancer patients, and 120 were not. These individuals underwent a procedure called endoscopic retrograde cholangiopancreatography whereby samples of their bile, a fluid produced in the liver, were retrieved and analyzed. Researchers also performed a series of blood tests, measuring a range of biomarkers, including cholesterol, bilirubin, bile acids, white blood cells, platelets, and others. Lastly, scientists determined the amount of eight neonicotinoids in bile samples, including acetamiprid, clothianidin, dinotefuran, imidacloprid, imidaclothiz, nitenpyram, thiacloprid, and thiamethoxam. Â Â
Researchers found their hypothesis to be correct. Of all samples taken, at least one neonicotinoid was detected in 99% of individuals tested. However, different neonicotinoids were found to act in different ways. While the detection of acetamiprid was low (1% of samples), 97% contained nitenpyram. The widely used insecticide dinotefuran was detected in 86% of bile. Detections did not appear to differ between participants of different health backgrounds.
The results led scientists to believe that neonicotinoids found in bile will eventually be absorbed again by the intestines, make their way into blood, and eventually oneâ€™s liver. Biomarkers tested, such as cholesterol, bilirubin, and bile acids, were found to correlate with higher concentrations of certain neonicotinoids. Of the various neonicotinoids, dinotefuran, thiamethoxam, and clothianidin were found to pose the greatest risk to liver health.
In this context, it may be interesting for readers to see how far EPA got in making a determination on liver health and neonicotinoids. Using dinotefuran as an example, here is a link to the Human Health Draft Risk Assessment the agency produced in 2017. As part of tests on the absorption, distribution, metabolism, and elimination studies on dinotefuran, EPA requires one single â€śspecial studyâ€ť on neonatal rat metabolism to determine how the chemical absorbs once in the body. The results (EPA does not provide methodology, only results in its review documents) indicate that in 12 day old rats, â€śabsorption was high (absorption could not be adequately determined but may have approached 80%) and the radiolabel was widely distributed within the body.â€ť Furthermore, the results indicate that, â€śThe test material was essentially not metabolized, the parent compound accounting for >97% of the radiolabel in the excreta, plasma, kidneys, and stomach, and nearly 61-83% in intestines (and contents), and liver.â€ť
Thus, EPA has enough evidence to show that dinotefuran barely metabolizes at all in oneâ€™s body. Yet this result did not tip EPA off in any way. No further testing was conducted to understand or characterize the hepatotoxic (injurious to liver) nature of the insecticide, and it does not appear as though the results influenced any changes in the agencyâ€™s determination around use patterns. In other words, EPA has enough data to investigate this issue and make even minor protective changes. Instead, after decades of this chemical being on the market, it has taken an independent, peer reviewed study to extrapolate and further investigate the critical details of how a near complete lack of dinotefuran adsorption in the body affects the liver.
Most disturbingly, this is not the only neonicotinoid health impact that the agency has failed to address. EPA is now being sued for long-term failure to screen and regulate pesticides that have the potential to disrupt the endocrine (hormone) system. In the context of neonicotinoids, there is growing evidence that exposure to these chemicals can result in hormone-dependent breast cancer. A 2019 study found that imidacloprid and thiacloprid can increase expression of a gene linked to breast cancer, and a 2022 study also found associations between neonicotinoid exposure and breast cancer.
In addition to the direct effects of cancer and liver toxicity, the latest evidence also shows these chemicals are indirectly killing hundreds of thousands of people around the world each year as a result of their detrimental impact to pollinator populations relied on for healthy, nutrient-dense food. Â
Join us in urging the Biden Administration, EPA and Congress to adopt a new direction for pesticide regulation, and Congress to once and for all pass the Saving Americaâ€™s Pollinator Act. Â
All unattributed positions and opinions in this piece are those of Beyond Pesticides.