01/22/09

Major Study Connects Clean Air and Longer Life

A new study of air quality and life expectancy, published today in the New England Journal of Medicine, concludes that reduction of airborne particulate in the 1980s and 1990s was associated with increased life expectancy.

A team of researchers from Brigham Young and Harvard Universities suggest that particulate air pollution and longevity are inversely proportional. Less pollution means longer life.

Life expectancy is meaningful as a long term measure of public health - people who live longer have a higher quality of life overall.

Particulate air pollution fell dramatically during the 1980s and 1990s as older cars without catalytic converters and dirtier industrial processes were retired.

Those decades witnessed a 2.7 year increase in life expectancy in 51 U.S. metropolitan areas studied.

Scientists attribute 15% of that longevity increment to air quality improvement.

That yields an average five-month increase in life expectancy.

For some dirtier cities, the improvement amounted to a 10-months of additional life.

Of course, we already knew that. Tobacco smoking's decline and socioeconomic factors were responsible for the majority of the longevity gains.

What is at stake here is the degree to which new pollution controls can produce cost effective benefits.

Opponents of clean air rules, including the outgoing Bush administration, argue that squeaky clean isn't needed, that diminishing marginal returns will set in as air quality improves.

Every five years the Environmental Protection Agency re-evaluates standards for airborne fine particulates, with the next appraisal set for 2011.

Average U.S. fine-particulate concentrations fell from about 20 micrograms per cubic meter (ug/m3) in the early 80s to about 14 micrograms by 2000.

Study authors suggested that airborne particulate could be cut by a similar amount in coming decades before additional air cleaning would produce smaller health benefits.

What is important to us is the focus of the study - fine particulates less than 2.5 microns in diameter (PM2.5).

Two micron particles can be detected only by an electron microscope. They originate primarily from burning - vehicle emissions, fireplaces, cigarette smoking, candles, forest fires, power plants, and industrial processes.

These are lung and bloodstream penetrators which have been demonstrated to promote cardiovascular and pulmonary disease.

While these fine particles are not the sole cause of the chronic inflammation now seen as fundamental to degenerative disease, they wreak havoc on those whose internal membranes are weakened by other factors.

Particles between 2.5 and 10 microns in diameter are referred to as "coarse dust particles."

Coarse particles are the size of road dust stirred up by passing vehicles.

These larger particulates, those we can see or which contribute to haze, are less dangerous.

Note that the Clean Air Delivery Rate (CADR) tests currently employed to measure air purifier effectiveness use particulate in the huge 9-micron size range.

Had the study focused on sub-micron particulate, I think results would have been even more dramatic.

The study reaffirmed earlier findings, concluding that removing 10 ug/m3 of urban airborne particulate yielded , an average life span increase of about seven months.

This reinforces my view that properly selected air purifiers can improve well being and possibly longevity.

or Clean Air Sitemap