Fine particles of soot in the air we breathe

Up in the Air

Imagine a particle of soot so small that thirty particles placed side by side would be about the same width as a human hair.

Environmentalists call this a “fine particle.” It’s measurement is PM 2.5; particulate matter equal to or less than 2.5 microns in diameter. But put enough of those fine particles of soot in the air we breathe and the result is not so fine at all. In fact, for older people the results may be deadly.

Particle response

The Environmental Protection Agency (EPA) maintains a national monitoring network known as AIRS: the Aerometric Information Retrieval Service. This network measures air quality factors, including fine particles generated by power plants and automobile exhaust.

In a recent study partly funded by the EPA, researchers from Johns Hopkins Bloomberg School of Public Health assessed potential health risks of short-term exposure to fine particles, which can deeply penetrate the respiratory tract.

The Hopkins team compared daily AIRS data collected throughout the U.S. between 1999 and 2002. This data was compared with hospital admission records from the same time period for more than 11 million Medicare patients. Researchers specifically looked for hospital admissions that were prompted by a variety of cardiovascular and respiratory problems, including coronary heart disease, heart failure, stroke, chronic obstructive pulmonary disease and respiratory infection.

Results revealed a short-term increase in hospital admissions for all of these conditions on days when levels of PM 2.5 were elevated. The most significant association was for heart failure.

In a press release from the National Institute for Environmental Health Sciences, lead researcher Francesca Dominici, Ph.D., stated that most of the spikes in hospital admissions occurred on the same day as the rise in fine particle concentration, suggesting “a short lag time between the change in pollution and the subjects’ response.”

Air quality right now

Dr. Dominici noted that it’s not yet known exactly what characteristics of fine particles produce adverse reactions. She also stated that a national air quality standard needs to be established to protect respiratory health.

We’ll leave the cause and effects mystery of fine particles to researchers, and future air quality standards to the EPA. For our purposes the Hopkins study points up the importance of those air quality alerts that are often included in local weather reports, especially in the summer when oppressive conditions sometimes trap and contain unhealthy air at ground level.

But you don’t have to wait for your local news broadcast to find out what the air quality is like in your area. Dozens of local and federal government agencies have pooled their air quality measurement resources in support of a web site called Air Now (airnow.gov). This site lists current air quality index (AQI) information for towns and cities throughout the country. For instance, last Friday (3/17/06) you could have visited Air Now to find out that the PM 2.5 reading for Port Angeles, WA, was “moderate,” which is considered safe for “sensitive groups.”

The Air Now site is easy to navigate and provides a clear, daily snapshot of the AQI across the nation and in your community.

Sources:
“Fine Particulate Air Pollution and Hospital Admission for Cardiovascular and Respiratory Diseases” Journal of the American Medical Association, Vol. 295, No. 10, 3/8/06, jama.ama-assn.org
“Elderly Have Higher Risk for Cardiovascular, Respiratory Disease From Fine Particle Pollution” National Institute for Environmental Health Sciences press release, 3/8/06, niehs.nih.gov