Consumer groups, scientists and food companies are testing substances — including breakfast cereal and breast milk — for residues of the world’s most widely used herbicide, concerned about its possible links to disease.

The focus is on glyphosate, the active ingredient in Roundup.

Testing has increased in the past two years, and scientists say requests spiked after a World Health Organization research unit said last month that it was classifying glyphosate as “probably carcinogenic to humans.”

“The requests keep coming in,” said Ben Winkler, laboratory manager at Microbe Inotech Laboratories in St. Louis.

The business has received three to four requests a week from a variety of groups to test foods and other substances for glyphosate residues vs. only three to four requests a year in the past.

(Lucy Nicholson/Reuters)

Abraxis, a diagnostics company based in Warminster, Pa., has also seen a “measurable increase” in glyphosate testing, said Dave Deardorff, one of the company’s partners.

An April 1 blog post by Monsanto, the maker of Roundup, said, “According to physicians and other food safety experts, the mere presence of a chemical itself is not a human health hazard. It is the amount, or dose, that matters.”

Trace amounts are not unsafe, said Monsanto senior toxicologist Kimberly Hodge-Bell.

While numerous studies have determined glyphosate to be safe, others have linked it to human ailments. Critics worry that glyphosate is so pervasive that extended exposure to even trace amounts may be harmful.