The E.P.A.’s bedrock mission is to protect public health and welfare. Its basic tools are 50 years of federal clean air and water laws meant to limit Americans’ exposure to environmental poisons and pollutants.

Every so often an administration comes along that seems to forget this mission. We have one now. Andrew Wheeler, the agency’s acting administrator, is clearly a great improvement in moral terms over his ethically challenged and thankfully departed predecessor, Scott Pruitt. Mr. Wheeler’s ideology and policies, however, are much the same, weighted in favor of the industries Mr. Wheeler once represented as a handsomely paid lobbyist, and against the health needs of Americans. Like the president he serves, Mr. Wheeler displays little concern for climate change and its epochal challenges.

The latest example is a proposal his agency sent to the White House for review and approval that would, in broadest terms, greatly devalue the public health benefits of reducing air pollution. The proposal is specifically aimed at a 2011 finding by the Obama administration that when the agency devises rules to control a particular pollutant — mercury, in this case — it must take into account not only the compliance costs to industry but the additional health benefits that arise from the reduction in other harmful gases like soot and smog that occur as a side effect. Though the health benefits of controlling mercury alone were quite small, and the costs to industry large, those costs were outweighed by savings to the country in annual health costs and lost workdays when the co-benefits were factored in.

The Wheeler proposal would disallow any calculation of these side benefits and allow only those associated with the regulated pollutant. Mr. Wheeler promises that existing mercury emissions limits will remain in place. He also acknowledges that industry has already invested billions of dollars on new technology to comply with the mercury rule, and that many companies have done so. But weakening the foundation on which that rule was promulgated could invite lawsuits to overturn it entirely, and — even more ominously — could make it easier for the Trump administration or a like-minded one to ignore important ancillary public health benefits when devising other environmental regulations in the future.

So chalk up another win for Robert Murray, the far-right Trump confidante and chief executive of the Murray Energy Corporation, a big coal producer for which Mr. Wheeler served as an attorney and lobbyist. Mr. Murray requested the mercury rollback as one of 16 items on a wish list he presented last year to the Trump administration. He is one of several coal barons who lobbied the administration to revisit the cost-benefit rules to set a precedent for future regulations.