The latest study to look at the long-term effects of Roundup, a popular weed killer developed by Monsanto in the 1970s, raises questions about the herbicide’s possible contributions to poor health in certain communities.
The study, published Tuesday in JAMA, tracked people over the age of 50 in southern California from 1993-1996 to 2014-2016, with researchers periodically collecting urine samples during that time.
Researchers led by Paul Mills, professor of family medicine and public health at the University of California San Diego, found that the percentage of people who tested positive for a chemical called glyphosate, which is the active ingredient in the herbicide Roundup, shot up by 500% in that time period. The levels of glyphosate also spiked by 1208% during that time.
Exactly what that means for human health isn’t quite clear yet. There are few studies of the chemical and its effects on people, although animal studies raise some concerns. One trial from the UK, in which rats were fed low levels of glyphosate throughout their lives, found that the chemical contributed to a higher risk of nonalcoholic fatty liver disease, a condition in which fat accumulates in the liver and contributes to inflammation and scarring of the tissue. Mills says that the levels of glyphosate documented in the people in his study were 100-fold greater than those in the rats.
To follow up on these results, Mills plans to measure factors that track liver disease, to see if the levels of glyphosate he found are actually associated with a greater risk of liver problems in people. He heads the Herbicide Awareness & Research Project at UCSD, an ongoing research project in which he invites people to provide urine samples to test glyphosate levels. By gathering more information about people’s exposure, he is planning to tease apart how much of it comes from actually ingesting products sprayed with the chemical, and how much can be attributed to breathing in particles that have been sprayed into the air, especially in farm communities.