(NVR) - Since reaching the market more than 40 years ago, glyphosate has become the most common of all weed-killing chemicals in the world’s farms and fields. In recent months, an activist group has turned the spotlight toward the presence of glyphosate in one of California’s most visible exports – its wines.

Laboratory testing on 10 California wines cited by Moms Across America, a campaigner against farm chemicals and genetically engineered crops, showed trace amounts of the herbicide widely known by the Roundup brand name.

Whether the reported amounts of glyphosate are a health concern has become a point of debate between Moms Across America, which decries the weed killer as a contributor to higher cancer rates and other maladies, and skeptics who describe such warnings as overblown.

“It has to stop now,” said Zen Honeycutt, a Mission Viejo mother of three boys who helped found Moms Across America in 2013. “It is poisoning America and destroying future of this great country.”

In recent days, however, some wine industry groups have struck back against the group’s claims, saying the report exaggerates the effect of trace amounts of glyphosate.

“You would have to drink 2,500 glasses of wine a day for 70 years to reach the EPA’s level of concern,” said Gladys Horiuchi, spokeswoman for The Wine Institute of San Francisco, an advocacy group for about 1,000 winemakers and related businesses. “We are talking about minuscule, trace amounts.”

In a March 24 press release, Moms Across America said an anonymous supporter had sent various California wines – some organic and others conventionally made – for analysis at Microbe Inotech Labs of St. Louis. Testing on the wines, whose brands and regions the group did not identify, revealed glyphosate levels ranging from 0.659 to 18.74 parts per billion, the group reported.

By comparison, the U.S. Food and Drug Administration sets a maximum safe level of glyphosate residue at 200 parts per billion on fresh grapes, and 700 parts per billion in drinking water.

“We focus so much on whether it could or could not be a carcinogen when bigger question is, ‘is it dangerous at the levels we are exposed to?’” said Dr. Carl Winter, a food science specialist at UC Davis. “The levels we are exposed to are many orders lower than doses required.

“The first principle is that the dose makes the poison. It’s the amount of exposure to the substance, and not its presence or absence, that determines the potential for harm.”

First sold in 1974 by Monsanto Co. under the Roundup name, glyphosate is a broad-spectrum herbicide that can kill numerous plant species and has gained wide and global use in farms and gardens alike. Its popularity has fed, and been fed by, the creation of “Roundup Ready” corn, soybeans, cotton and other crops genetically engineered to withstand the chemical while surrounding weeds die.

The herbicide has become a target in recent years of critics questioning its safety to humans.

A 2015 report from the World Health Organization’s International Agency for Research on Cancer described glyphosate as “probably carcinogenic,” citing a survey of existing studies of the compound. California regulators cited the WHO declaration in its proposal to add it to a state list of known cancer-causing substances, a move that led Monsanto to sue the state in January. At the federal level, the Environmental Protection Agency is reviewing the safety of glyphosate, which it listed in the 1990s as not cancer-causing.

A recent meeting of the WHO and the Food and Agriculture Organization of the United Nations, which was intended to clarify glyphosate’s risk level, has instead led to accusations of conflicts of interest, according to media reports.