Particulate Air Pollution May Hospitalize Elderly

BALTIMORE, March 8 - Short-term exposure to ultrafine particulate air pollution increased the risk of Medicare-age hospital admissions for cardiovascular and respiratory ailments, according to a national database study.

Evidence for the health risks of inhaling particles as fine as 2.5 µm in aerodynamic diameter (PM2.5) came from a database of hospital admissions for 11.5 million Medicare enrollees in 204 U.S. urban counties, reported Francesca Dominici, Ph.D., of Johns Hopkins. Particles this small have a much greater chance of reaching the small airways and the alveoli than do larger particles, she and colleagues wrote in the March 8 issue of the Journal of the American Medical Association.

A new standard for small particles of less than or equal to 2.5µm was established in 1997 by the Environmental Protection Agency in response to growing evidence of adverse health effects from chronic exposure to airborne pollution. But the EPA also maintained the former indicator of PM10 for particulate matter.

The PM10 for airborne particles does not protect public health with "an adequate margin of safety," which the EPA is required to maintain, concluded Dr. Dominici and colleagues.

In the study, all individuals lived an average 5.9 miles from a PM2.5 monitor where particulate levels tend to be uniform.

To assess the health risks of particles 2.5 µm in size, the researchers undertook an analysis of county-wide hospital admissions between 1999 and 2002 and found a short-term increase in hospital admissions for almost all the events analyzed.

Hospitalizations included a primary diagnosis of cerebrovascular disease, peripheral and ischemic heart disease, heart rhythm irregularities, heart failure, chronic obstructive pulmonary disease, and respiratory disease.

The largest association was with heart failure, which had a 1.28% (95% CI, 0.78%-1.78%) increase in risk per 10-µm/m3 in same-day PM2.5. Cardiovascular risks tended to be highest in the eastern and southern regions of the U.S, including the northeast, southeast, south, and midwest, the researchers said.

Mechanisms underlying these adverse effects remain a focus of research, Dr. Dominici said, but leading hypotheses emphasize inflammatory responses in the lung and the release of cytokines with local and systemic consequences. Particulate matter may exacerbate underlying lung disease and reduce the efficacy of lung-defense mechanisms.

Cardiovascular effects may reflect neurogenic and inflammatory processes. Animal studies suggest that particulate matter may accelerate the development of atherosclerosis, the researchers said.

"Our findings" the investigators concluded, "indicate an ongoing threat to the health of the elderly population from airborne particles and provide a rationale for setting a PM2.5 National Ambient Air Quality Standard that is as protective of their health as possible." The emphasis of research, they added, should shift toward identifying those characteristics of particles that determine their toxicity.

This article was published by Environmental Health Perspectives, copyright 2006. It can be accessed online at the following link.

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Elderly Have Higher Risk for Cardiovascular, Respiratory Disease from Fine Particle Pollution
Particulate Air Pollution May Hospitalize Elderly
The Effects of Air Pollution on Hospitalizations for Cardiovascular Disease in Elderly People
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