The Environmental Protection Agency took its first step on Thursday toward a comprehensive overhaul of the cost-benefit calculations that underpin the entire array of its regulations, notably any actions to rein in global warming.

In a notice inviting the public to comment on whether and how to adjust its methods, the agency signaled a potential wave of revisions to how it seeks balance in its rules under laws governing air, water, solid waste, pesticides and climate change.

One option it flagged, which could have far-reaching effects on rules involving fossil fuels, the main source of greenhouse gases, would do away with expansive calculations of benefits when rules meant to control one form of pollution also serendipitously cut back on another.

Because burning fossil fuels gives off many kinds of harmful pollution, regulators have commonly cited the full range of ancillary benefits that arise whenever new rules suppress the use of coal, oil and natural gas. At the request of industry, the EPA's notice said, the agency will consider changing this approach.

Even if some proposed rule could bring greenhouse gas emissions down to zero, such as by replacing fossil fuels with clean alternatives, the agency would not count the benefits to public health that would result as choking smog and soot vanished along with the carbon dioxide.

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EPA Administrator Scott Pruitt made plain that he wants to challenge the cost-benefit justifications not just for climate-related rules put forward by the Obama administration, but also for many other regulations that polluting industries find onerous.

"Many have complained," Pruitt said, "that the previous administration inflated the benefits and underestimated the costs of its regulations through questionable cost-benefit analysis."

That is a common complaint from the fossil fuel industries, and one that Pruitt himself turned to when, as Oklahoma's attorney general, he sued the agency he now runs.

Among his main targets now are the Clean Power Plan's limits on carbon dioxide emissions from coal-fired power plants, controls on oilfield emissions of methane, goals for automotive fuel efficiency and tailpipe emissions, and other rules that the Trump administration has said it wants to freeze, roll back or repeal.

Social Cost of Carbon Already Targeted

The Trump administration has already taken some steps along these lines, the EPA said in announcing the latest move.

For example, it has revised the way it calculates what economists call the "social cost of carbon," an attempt to measure in today's dollars the costs imposed on future generations every time a ton of carbon dioxide is emitted. Under the Obama administration this estimate was set at about $35 per ton of CO2, a figure that many economists consider much too low to reflect the true harm of global warming. Under the Trump approach it would be about $5.

And when EPA proposed its repeal of the Clean Power Plan, it eliminated from the cost-benefit analysis any consideration of the public health benefits that would come from controlling sooty particles from burning coal, even though public health scientists estimate that particulate pollution sickens and kills tens of thousands of people.

Industry Groups Requested Changes, EPA Says

In its formal notice seeking public comment, the EPA observed that industry groups had requested this kind of change when the agency solicited public views on "a myriad of regulatory reform issues" in early 2017.

As an example, the agency cited regulations controlling emissions of mercury from power plants. Many coal-fired plants have shut down rather than invest in the required pollution controls. As a result, soot emissions have been reduced significantly, too, a benefit the Obama EPA considered when setting the rules.

Exposure to mercury can damage developing brains, among other harms. But when put in dollar terms, the Trump EPA said, the benefits of controlling mercury exposure are less than the costs to industry. Even though the public's lungs were protected from soot while its central nervous systems were protected from mercury, the agency reasoned in its new notice, this cost-benefit analysis was flawed.

'Cooking the Books'?

Sara Chieffo, vice president of government affairs for the League of Conservation Voters, said the Trump administration was trying to put its thumb on the scale to help polluters.

"Scott Pruitt has shown us once again that he doesn't care about the costs of pollution to human health. His claim that benefits have been inflated in EPA regulatory decision making is simply not borne out by the facts and in today's far-reaching announcement, he is doing nothing short of cooking the books so that polluters always win, and people always lose."

Public comments will be accepted for 30 days after the rule is formally published in the Federal Register.