ISN'T it odd, asks Henry Waxman, a Democratic congressman from California, how the same Republicans who make such a fuss about abortion do not seem to care if the unborn are poisoned by toxic chemicals such as mercury? Isn't it strange, Republicans retort, that people like Mr Waxman, who profess to care about working Americans, cheer on bureaucrats determined to smother business and destroy jobs? It may be hard to discern amid the melodramatic rhetoric, but the two sides are talking about the Environmental Protection Agency, and the various new rules it has in the works to curb pollution. Besides the endless toing and froing about government spending, it has become the most fiercely debated topic in Congress.

As soon as they took control of the House of Representatives in January, Republicans began summoning Lisa Jackson, the head of the EPA, and several of her underlings to answer questions about their job-killing ways. Fred Upton, the head of the committee responsible for energy and environmental regulation, joked that she would be on Capitol Hill so often she would need her own parking space.

The Republicans' chief concern is the EPA's authority, as affirmed by the Supreme Court in 2007, to regulate emissions of greenhouse gases. But more broadly they worry that the EPA is constantly tightening restrictions on pollution, at ever higher cost to business but with diminishing returns in terms of public health. They point to a slew of new rules about industrial boilers, cooling water at power plants, the disposal of coal ash, and emissions of mercury, ozone and other chemicals from smokestacks, which cumulatively, they say, will have a crippling effect on power generation and other industries. “Even God,” says Joe Barton, a Republican congressman, “couldn't meet some of the ozone standards.”

Mr Barton is among the many Republicans in Congress who question whether global warming is caused by human activity, let alone whether the EPA should be trying to mitigate it by limiting emissions of greenhouse gases. The House has passed a measure that would rescind the EPA's authority to do so, although it was blocked in the Senate, which the Democrats still control. The Republican leadership in the House has accused the administration of plotting to raise the price of energy through onerous regulation, in an effort to promote otherwise uncompetitive green technologies. It wants the EPA to give more weight to the impact on the economy and jobs when drawing up future rules.

Republicans outside Congress are warming to the theme. In late May Chris Christie, the much-feted governor of New Jersey, withdrew his state from a regional pact to reduce greenhouse-gas emissions from power plants. Several prominent Republican candidates for president have recanted past support for curbs on greenhouse gases. One of them, Newt Gingrich, a former speaker of the House, says the EPA should be abolished altogether and an “environmental solutions agency” more sympathetic to business set up in its stead.

EPA officials appear baffled by this barrage of hostility. All the regulations they are promulgating, they point out, are based on laws passed by Congress, usually on a bipartisan basis. The Clean Air Act, for example, which is the basis of the EPA's proposed regulation of greenhouse gases, was signed by Richard Nixon, and strengthened with the support of George Bush senior, both Republicans. The agency, they say, already conducts cost-benefit analyses of all important regulations, in addition to submitting them for expert review and public comment. Every dollar spent on pollution controls mandated by the Clean Air Act, including the ozone restrictions that Mr Barton is complaining about, will bring $30 in benefits to public health, the EPA reckons.

Under Mrs Jackson many of the most significant new rules are also being subjected to a separate review of the impact on jobs; though since onerous environmental restrictions can be labour-intensive, that is not always a good measure of the overall economic benefit. Moreover, the EPA is producing so many regulations at once in part because it is legally bound to. One of the rules the Republicans are complaining about, regarding mercury, arsenic and other toxic chemicals released by power plants, has been in the works for over 20 years. The EPA's original regulations on the subject were thrown out by the courts as too lax. Anyway, so a combative official told her Republican interrogators earlier this year, complaints about the toll on business of pollution controls are almost always wildly exaggerated.

Yet the EPA is clearly stung by the criticism. The White House recently announced that the agency had scrapped a rule requiring leaks of dairy products to be treated as oil spills, as part of a government-wide review of red tape that may be impeding economic growth. It is now considering revisions to a further 31 regulations. It has also delayed the implementation of the new regulations concerning industrial boilers, after loud complaints from the businesses affected. And it seems in no hurry to use its authority over greenhouse gases, settling instead for a lengthy rule-drafting period that could forestall the imposition of any restrictions until after next year's elections.

That is in part, presumably, because at the mid-terms last year the Republicans succeeded in portraying the Democrats' plans to restrict emissions via a cap-and-trade scheme as an all-out assault on the economy, to great effect. John Shimkus, another Republican congressman, says Republicans will benefit again if environmental regulation remains a fraught issue next year. But Democrats like Mr Waxman argue that the Republicans are reading too much into their victory last year. Voters may put their immediate economic concerns ahead of more amorphous worries about global warming in the wake of the recession, he says, but they are still not willing to tolerate a broader assault on regulations that protect public health.

In short, both the Democrats and the Republicans think they have found a winning theme in the other party's environmental policies. And they may both, in fact, be right. Most polling suggests that the environment is not a critical issue in the eyes of many voters. But talking about it is a great way to fire up activists and donors on both sides.