The U.S. Food and Drug Administration (FDA) has been sued by a coalition of advocacy groups, seeking to vacate its approvals of several livestock-feed products that are widely used to add weight to farm livestock.

The Wall Street Journal (WSJ) reported that in two different lawsuits filed on Nov. 6 in the U.S. District Court of Northern California in San Francisco, groups including the Center for Food Safety, the Humane Society of the United States and United Farm Workers of America argue that in approving drugs like Topmax, a medicated feed additive used to produce lean muscle instead of fat, the FDA failed to adequately consider the drugs’ collective effects on animal welfare, worker safety, wildlife and U.S. waterways.

The legal action is the latest dispute over a class of drugs known as beta-agonists that were developed to treat asthma in humans. The WSJ reports that in recent years they have become pervasive in U.S. livestock farming to promote muscle gain. The products targeted in the lawsuits are based on ractopamine, which the FDA first approved for use in pigs in 1999.

Merck & Co. in August 2013 suspended sales of a similar product, Zilmax, or zilpaterol, because of concerns in the beef industry that the drug made it hard for some animals to walk, the WSJ reports.

Critics of ractopamine say it also can have detrimental effects on animals, resulting in stiffness, lameness and even death. Some other governments ban the drug, including the European Union and China.

Elanco, the animal-health unit of Eli Lilly & Co., makes Paylean for pigs, Topmax for turkeys and another ractopamine-based product called Optaflexx for cattle, and the WSJ reports that an Elanco spokeswoman says, “FDA approved ractopamine nearly 15 years ago and we remain confident in its safety and the FDA’s approval process.”

Elinore White, a spokeswoman for Zoetis, which recently won approval for two generic ractopamine products for cattle and pigs says, “We at Zoetis stand by the safety and efficacy of our generic ractopamine products and believe they deliver value to our customers.”

The WSJ reports an FDA spokeswoman said the agency doesn’t comment on pending litigation.

Plaintiffs in the lawsuits say that in approving 11 new and combined animal drugs containing ractopamine between 2008 and 2014, the FDA failed to fulfill its duties under the National Environmental Policy Act. The federal law requires the agency to conduct an environmental analysis on the impact of such drugs.

The WSJ reports the drugs targeted in the suits include those in which ractopamine is the single active ingredient, as well as others in which is it combined with antibiotics, some of which belong to the same class as those considered important to human health.

According to the lawsuits, residue from the drugs can remain active in animal waste, and when applied to fields, or escape from manure lagoons, it can imperil the surrounding habitat, contaminating groundwater and endangering wildlife, the WSJ reports.

Click here for the Wall Street Journal story.