CHICAGO (Reuters) - One of the most popular herbicides in U.S. agriculture can be dangerous to animals and fish and leaves behind worrisome residue levels, the Environmental Protection Agency said on Thursday in a draft report that sparked outrage among farmers.

The agency’s assessment of atrazine could lead to tighter regulatory limits on the product, manufactured by Swiss-based Syngenta AG. That could ultimately prevent farmers from being able to use it to control weeds, according to agricultural groups that blasted the report as flawed.

Atrazine is primarily used on corn, sorghum and sugarcane to fight weeds and increase yields in the Midwest.

The EPA’s review adds to a debate about the safety of leading crop chemicals after a branch of the World Health Organization said last year that the herbicide glyphosate was “probably” able to cause cancer in humans.

The EPA said atrazine’s effects exceeded its “levels of concern” for chronic risk by 198 times for mammals and 62 times for fish. The agency will accept comments on the preliminary findings and consider whether to require label changes after it publishes a final risk assessment.

The EPA republished the findings after it said it inadvertently posted the same report, along with other related documents, online this spring in an error that has sparked criticism from U.S. lawmakers.

Syngenta, which is set to be acquired by Chinese state-owned ChemChina, said atrazine is safe and that the EPA report “contains numerous data and methodological errors and needs to be corrected.”

If the EPA’s report is finalized as written, it could cause label restrictions so severe that they would “effectively ban the product from most uses,” the Iowa Corn Growers Association said.

“EPA’s flawed atrazine report is stomping science into the dirt and setting farmers up for significant economic hardship,” said Gary Marshall, executive director of the Missouri Corn Growers Association.

The U.S. House of Representatives’ agriculture committee is looking into EPA actions related to its multi-year review of potential risks tied atrazine and glyphosate.

In April, the agency posted documents online, including a report that said glyphosate was not likely to be carcinogenic to humans. It later pulled them down.

The agency said it plans to release its draft cancer risk assessment for glyphosate by year’s end.