A new study by the Italian Ramazzini Institute links exposure to glyphosate, the active ingredient in the world’s most widely applied herbicide, at concentrations considered to be safe with effects on the endocrine systems of male and female rats. Melissa Perry, SciD, MHS, professor and chair of the George Washington University Milken Institute School of Public Health, is a coauthor of the new study.
“The possible effects of exposure to glyphosate-based herbicides, which include Roundup, on human health have been the subject of intense public debate,” said Perry, who is a fellow of the Collegium Ramazzini and collaborates with researchers at the Ramazzini Institute.
Relatively few human studies assessing the effects of exposure to glyphosate have been conducted, and the evidence to date is too limited to draw conclusions. The results and interpretation of animal and cell-based studies involving exposure to both high and low doses of glyphosate herbicides have been mixed. Some studies have linked exposures to statistically significant effects on the endocrine system, including changes in concentrations of testosterone, 17β-estradiol, sexual maturation, sperm counts and pituitary hormones.
An evaluation of glyphosate by the U.S. Environmental Protection Agency’s (EPA’s) Endocrine Disruptor Screening Program showed that glyphosate had no impact on the estrogen pathway. The European Food Safety Authority concluded that the weight of evidence did not support endocrine disrupting properties of glyphosate-based herbicides on the estrogen, androgen, thyroid or steroidogenesis modes of action.
In the courts, two juries have now found that exposure to Roundup played a substantial role in the cause of the cancer Non-Hodgkin lymphoma in two different men. The more recent case is the first to be tried in federal court, and whether Roundup’s manufacturer, Monsanto, is liable has yet to be determined. Last August, jurors in California awarded a former school groundskeeper $289 million in damages, an amount that a judge reduced to $78 million. Thousands of similar cases are pending at the federal and state levels.
The research team led by the Ramazzini Institute exposed pregnant Sprague Dawley rats to glyphosate and Roundup at levels considered to be safe based upon the U.S. EPA’s Acceptable Daily Intake reference dose and evaluated the effects on the rat pups.
The team found that the rats’ exposure to Roundup and glyphosate induced endocrine effects and altered reproductive developmental parameters in male and female rats. The effects included increasing the ano-genital distance in rats of both sexes, which is associated with impacts on the androgen system.
“This was a pilot study, and the developmental impacts on rats were notable,” Perry said.
“The Ramazzini Institute 13-week pilot study glyphosate-based herbicides administered at human-equivalent dose to Sprague Dawley rats: effects on development and endocrine system” is published in Environmental Health.