Snowball, the pig in George Orwell’s “Animal Farm,” uses this catchy adage to summarize his view that people are enemies and animals are friends: “Four legs good, two legs bad.” Bizarrely, the Trump administration appears to have been persuaded, announcing a policy that will harm human health to protect animals used in laboratory experiments. The move will compromise an important source of evidence of the impacts of contaminants.

This month, Andrew Wheeler, the administrator of the Environmental Protection Agency, announced that the agency would significantly curtail its reliance on the use of mammals in toxicological studies conducted to determine whether environmental contaminants have an adverse impact on human health. Under this plan, the E.P.A. will reduce its requests for, and funding of, mammal studies by 30 percent by 2025 and eliminate them altogether by 2035, though some may still be approved on a case-by-case basis.

The new policy is likely to have adverse impacts on public health. Laboratory animal testing, particularly on rodents, has long been an important means for determining the toxicity of chemicals and other environmental contaminants. According to Mr. Wheeler, new methods are available to effectively provide information on chemical hazards without relying on animal testing. Experts don’t seem to agree with him. As Tracey Woodruff, a professor at the University of California, San Francisco, School of Medicine, has said, only animal testing, and not the methods extolled by Mr. Wheeler, is currently robust enough to gauge the full range of the impacts of contaminants on human populations. Even Scott Gottlieb, the Food and Drug Administration commissioner, stated last year, “Without animal research, it would be impossible to gain some of the important knowledge needed to prevent human and animal suffering for many life-threatening diseases.”

Mr. Wheeler asserted that the reason for this move was to protect animals used in laboratory experiments. Attempting to address skepticism about whether his motive was genuine, he stressed that this issue had been of “longstanding interest” to him, that when he was young his mother had told him about the “ethical problems” of animal testing and that one of his sisters was a zoologist and another was a veterinarian. Animal rights groups, including the Humane Society, praised the move.