A study published in the journal JAMA showed once again that levels of glyphosate, the main ingredient in the popular herbicide Roundup, in human urine have increased dramatically among Californians in the past 20 years. 
For the study, urine samples were collected from 100 Southern California residents over the age of 50 from 1993-1996, to 2014-2016.
Paul Mills, professor of family medicine and public health at the University of California San Diego, and a team of researchers found that the percentage of people who tested positive for glyphosate skyrocketed 500% during that period. The levels of glyphosate also spiked 1,208% during those years.
During the early phase of the study, Mills said “there were very low levels – and they were only detectable in 12 out of 100 people.” 
“Then over the next 22 years, we found about a 1,000% increase in the levels found in the 100 people, on average.”
Prenatal glyphosate exposure has been linked to shorter gestation times and lower birth weights in babies. Some research suggests, too, that the chemical may be generating deadly antibiotic-resistance.
But glyphosate most often makes headlines for its potential link to cancer. Multiple studies have found that the Roundup ingredient could be carcinogenic. The International Agency for Research on Cancer (IARC) wing of the World Health Organization (WHO) classified glyphosate a probable human carcinogen in 2015.
The group said in 2016, however, that “glyphosate is unlikely to pose a carcinogenic risk to humans from exposure through the diet.”
Yet Mills believes the levels in human urine increased primarily from people eating foods sprayed with the chemical.
“It’s unlikely that all these folks are spraying that much Roundup in their yards every day, to get the levels we observed. Our research is showing that a lot of us across the US likely have fairly significant levels of these compounds, unless we take up an organic diet”
To follow up on his findings, Mills plans to measure factors that track liver disease, to ascertain whether the levels of glyphosate detected in the study are associated with a greater risk of liver problems in humans.
A study from the UK, in which rats were fed low levels of glyphosate throughout their lives, found that the chemical increased the risk of nonalcoholic fatty liver disease in the rodents. According to Mills, the levels of glyphosate found in the people in his study were 100-fold greater than those in the rats, though they were still very low. 
Specifically, Mills wants to find out how much people are exposed to glyphosate through breathing in particles that have been sprayed into the air, especially in agricultural areas.
Glyphosate use is on the rise in the US., and it is the most widely used herbicide chemical in the world. Roundup was developed to eliminate weeds from corn, soy, and other genetically modified crops, however, many weeds have grown resistant to the herbicide. This means that farmers must spray even more of it, potentially increasing the health ramifications of being exposed to the weed-killer.
“From my perspective it’s remarkable that we have been ingesting a lot of this chemical of the last couple of decades. But the biomedical literature hasn’t said much about its effects on people. That’s a gap that we endeavored to address and bring more awareness to with this study.”