The Trump administration is keeping the weedkiller Roundup on the US market, insisting it is safe for humans despite thousands of lawsuits launched by people who claim it gave them cancer.

The Environmental Protection Agency (EPA) maintains in a new decision that glyphosate, the active ingredient in Roundup, which is made by Monsanto, does not cause cancer or other health problems if it is used according to instruction labels.

Glyphosate is used on more than 100 crops, including genetically modified corn, soy, cotton, canola and sugar beet, according to the EPA. Groups campaigning against glyphosate say it is most dangerous for farmworkers and others applying it but also poses risks for people consuming it in food.

Courts have found in favor of a school groundskeeper who is terminally ill with non-Hodgkin lymphoma and another man who used the chemical for decades and developed the same kind of cancer.

The German company Bayer acquired Monsanto last year. Shareholders have voiced concern about being held liable for cancer cases that may be related to Roundup.

The non-profit Environmental Working Group (EWG) and major retailers of organic food have petitioned the EPA to set a lower level for the amount of glyphosate allowed in oats and to prohibit spraying the chemical just before harvest.

Oat crops are allowed to have 30 parts per million of glyphosate. The advocates want that reduced back to a previous requirement of 0.1 parts per million or lower. In one review, EWG found glyphosate in most cereals marketed to children.

The EPA said its decision that glyphosate does not cause cancer is “consistent with the conclusions of science reviews by many other countries and other federal agencies”.

But another federal agency said earlier this month it could not rule out a link between glyphosate and non-Hodgkin lymphoma. The Agency for Toxic Substances and Disease Registry, within the US health department, published a 257-page report suggesting more research was needed.

Jennifer Sass, a chemicals expert at the Natural Resources Defense Council, said: “Health agencies and credible non-industry experts who have reviewed this question have all found a link between glyphosate and cancer.”

Olga Naidenko, a senior science adviser for the EWG, said more studies were necessary to know, in particular, how much glyphosate children were consuming.

“All of us are exposed and it is not just the risk of cancer because, as the latest research has indicated, for example, glyphosate can have very subtle interference with the endocrine system,” Naidenko said.

In the EPA press release, the US agriculture secretary, Sonny Perdue, said: “If we are going to feed 10bn people by 2050, we are going to need all the tools at our disposal, which includes the use [of] glyphosate.”

Naidenko countered that in the past, farmers had been able to grow crops without it.

The EPA has acknowledged that glyphosate poses an ecological danger. According to a press release, it “is proposing management measures to help farmers target pesticide sprays on the intended pest, protect pollinators and reduce the problem of weeds becoming resistant to glyphosate”.