To reduce weedy competition in vineyards, growers regularly spray herbicides like Roundup between the rows of trellised vines. Is Roundup as benign as growers believe?
Two National Institutes of Health-backed studies link the herbicide to birth defects and miscarriages; one raises the possibility that the product’s inactive ingredients may be the culprits.
“Even we were surprised at our findings,” says Dr. Vincent Garry, who led a team investigating birth defects in Minnesota’s Red River Valley. “Almost everything I’d ever read in the literature had said that Roundup is pretty tame stuff, that it goes where it’s supposed to go, does what it’s supposed to do, and not much else. But then we found this anomaly.”
The “anomaly” linked Roundup to a significantly higher rate of neurobehavioral birth defects, particularly in boys fathered by men who had applied herbicides. Based on an analysis of the timing of herbicide applications, conception, and births, it also uncovered a higher-than-expected percentage of defects in children conceived in the spring, the season when heavy herbicide application usually starts.
Garry says the study didn’t find these effects when pure glyphosate, Roundup’s active ingredient, was used. But Roundup was still implicated, which points toward one of the formulation’s “inert” or “other” ingredients.
Monsanto has resisted disclosing these ingredients and did so only after an Oregon public interest group successfully sued to force the company to list all ingredients. Some formulations contain polyethoxylated tallowamine and in some, the glyphosate is in the form of isopropylamine salt. Some researchers argue that those compounds may be the problem, according to Joseph Mendelson in The Ecologist.
A second study, the 2001 Ontario Farm Family Health Study, associated Roundup with miscarriages. Researcher Tye Arbuckle asked more than 2,100 women about their approximately 4,000 pregnancies and roughly 400 miscarriages, then examined the pesticide application history on the farms, and found “moderate” increases in first-trimester miscarriages when the women had been exposed to any of several popular herbicides before conception. They also found a correlation between early post-conception Roundup use and miscarriages between the twelfth and nineteenth weeks of pregnancy. The study used regression analysis, a technique that allowed researchers to eliminate some chemicals and focus on others.
“This study is important not just because of its size, but because it looked at a lot of popular, specific pesticides and herbicides, rather than just general exposure levels,” says Arbuckle.
The studies are part of a small but growing body of evidence that indicates an ingredient in Roundup might be an endocrine disruptor, interfering with hormones involved in sperm and egg production and in the adrenal gland, which might explain neurobehavioral birth defects.
The focus on endocrine disruption is new, and many questions remain. Toxicologists Philip Harvey and David Everett, writing in the Journal of Applied Toxicology, emphasize that there is no direct evidence that environmental exposure to endocrine-disrupting chemicals has caused adverse human health effects. Yet, citing the unanticipated effects of the hormone drug DES, the authors urge researchers to test for effects on adrenal reproductive function when they do regulatory testing.
Garry and Arbuckle say more studies are essential to back up their research. To implicate Roundup as a direct cause, they both say, other types of proof — such as tissue experiments that would uncover exactly how the alleged disruption happens — are necessary. Some such studies have already been done; a National Institutes of Health study published in Environmental Health Perspectives found that Roundup disrupts a key reproductive protein.
Garry and Arbuckle won’t be doing any follow-up studies. Both say lack of funding has curtailed their research. “I’ve been Bush-whacked,” says Garry.
