Already under fire for seeming to write off tens of millions of Americans who back President Obama because they receive federal assistance, a liberal group Tuesday claimed that Mitt Romney would essentially poison and kill 21,600 if given the opportunity as president to trim air pollution rules he doesn't like and that punish GOP donors.

The Center for American Progress Action Fund, founded by Obama advisor John Podesta, issued a report that said Romney's bid to align with House Republicans trying to curb Clean Air Act rules enacted just under President Obama would "lead to 21,600 unnecessary premature deaths, 199,000 asthma attacks, and 12,540 hospitalizations every year."

Citing Obama-backed measures that "shield children, seniors, and other vulnerable people from mercury, carcinogens, and carbon pollution," the think tank said Romney and vice presidential running mate Rep. Paul Ryan want to "invalidate defenses against industrial chemical hazards would have tragic health consequences for hundreds of thousands of Americans."

And the cost of that assault on American health, according to the report titled "Permitting Poison in the Air Means More Money for the Romney-Ryan Campaign": $187 billion annually due to premature deaths, health care expenses, and lost productivity.

All, the group adds, because the GOP wants to curry favor with coal, oil and utility companies that have provided some $3 million in contributions.

The report comes as the House this week considers H.R. 3409, a bill to block the Environmental Protection Agency from imposing rules to reduce mercury, carcinogens, soot, smog, and carbon pollution from power plants and other sources.

On his website, Romney doesn't have a special section for the environment but has a long energy policy that includes eliminating carbon dioxide from Clean Air Act rules and stopping federal spending on technologies that are "particular politically favored."