Clean air act may be saving more lives than thought

The number of Americans who die each year from inhaling fine-particle pollutants has dropped dramatically since 1970, thanks to laws that originated from the U.S. Environmental Protection Agency.

That finding stems from an investigation, led by Massachusetts Institute of Technology (MIT) researchers, into the impact of EPA rules enacted by the 1970 Clean Air Act and amendments added to it in 1990.

The legislation regulated air pollutant emissions and promoted efforts to find clean alternatives.

The EPA itself had estimated in 2011 that the agency's efforts had translated into an estimated 100,000 lives saved every year from 2000 to 2010.

However, the MIT analysis found that the EPA had underestimated its impact.

The agency had neglected to factor in the effect of its efforts to limit exposure to so-called "organic aerosol," the researchers said. That's a pollutant that stems largely from such things as car emissions, residential burning and wildfires.

"The EPA report showed a very large impact from the decline in particulate matter, but we were surprised to see a very little change in the organic aerosol concentration in their estimates," study author David Ridley noted in an MIT news release. "The observations suggest that the decrease in organic aerosol had been six times larger than estimated between 2000 and 2010 in the EPA report."

The decline in organic aerosol may account for more lives saved than the EPA had estimated, according to the MIT report.

"There are costs and benefits to implementing regulations such as those in the Clean Air Act, but it seems that we are reaping even greater benefits from the reduced mortality associated with particulate matter because of the change in organic aerosol," Ridley said. He's a research scientist with MIT's civil and environmental engineering department.

The MIT findings were published online Dec. 26 in the Proceedings of the National Academy of Sciences.

LONDON -- Drinking alcohol may cause irreversible damage to the DNA of stem cells and increase the risk of developing certain cancers, a new study has revealed.

Using genetically modified mice, British scientists found that acetaldehyde, a toxin produced as the body processes alcohol, can slice through the DNA within blood stem cells and cause permanent damage.

In the study, published recently in the journal Nature, the mice lost their ability to reproduce fresh blood after being given diluted alcohol for 10 days.

Sequencing the genome of the stem cells indicated that their DNA had been scrambled to the point that the cells no longer functioned.

When healthy stem cells are faulty, they can give rise to cancerous cells, particularly in the mouth, throat, esophagus, breast and so on.

The effects of such damage can be neutralized, however, by the body's two-layer defense mechanism. The first layer is a protective enzyme called aldehyde dehydrogenase 2 (ALDH2), which prevents build-ups of acetaldehyde, and the second repairs the DNA damage.

In the study, mice lacking ALDH2 suffered four times as damage compared with the other ones.

About 8 percent of the world's population, mostly those of East Asian ancestry, are born with a deficiency in ALDH2.

"Our study highlights that not being able to process alcohol effectively can lead to an even higher risk of alcohol-related DNA damage and therefore certain cancers," said Ketan Patel, who led the research at the MRC Laboratory of Molecular Biology in Cambridge. (Xinhua)