The EPA proposed requirements Friday that large garbage dumps reduce emissions released by decomposing trash, including toxic and smog-forming gases and methane - a key greenhouse gas.

The Environmental Protection Agency proposal would establish pollution control standards to achieve a 75 percent reduction in the 255,000 metric tons of non-methane organic gases emitted each year from landfills nationwide. Among other gases, it would cut toxic emissions of benzene and vinyl chloride.The proposed rules also are expected to help address global warming by cutting in half the 10.5 million metric tons of methane that seep out of landfills annually.

Methane, a potent greenhouse gas, has been accumulating in the atmosphere, where it traps heat radiating up from Earth that otherwise would escape into space.

On a third air pollution problem, the new emission controls will ease urban smog by cutting volatile organic compounds that play a key role in the formation of ozone smog.