New data from a four-year study of 11.5 million Medicare enrollees show that short-term exposure to fine particle air pollution from such sources as motor vehicle exhaust and power plant emissions significantly increases the risk for cardiovascular and respiratory disease among people over 65 years of age.
The study, funded by the National Institute of Environmental Health Sciences is the largest ever conducted on the link between fine particle air pollution and hospital admissions for heart- and lung-related illnesses.
The study results show that small increases in fine particle air pollution resulted in increased hospital admissions for heart and vascular disease, heart failure, chronic obstructive pulmonary disease, and respiratory infection. "The data show that study participants over 75 years of age experienced even greater increases in admissions for heart problems and chronic obstructive pulmonary disease than those between 65 and 74 years of age," said National Institutes of Health Director Elias A. Zerhouni, M.D.
The National Institute of Environmental Health Sciences and the U.S. Environmental Protection Agency provided funding to researchers at the Johns Hopkins Bloomberg School of Public Health for the study. The study results are published in the March 8, 2006 issue of the Journal of the American Medical Association.
According to the study, these findings document an ongoing threat from airborne particles to the health of the elderly, and provide a strong rationale for setting a national air quality standard that is as protective of their health as possible.
"These findings provide compelling evidence that fine particle concentrations well below the national standard are harmful to the cardiovascular and respiratory health of our elderly citizens," said NIEHS Director David A. Schwartz, M.D. "Now that the link between inhaled particles and adverse health effects has been established, we must focus our efforts on understanding why these particles are harmful, and how these effects can be prevented."
Fine particle air pollution consists of microscopic particles of dust and soot less than 2.5 microns in diameter - about thirty times smaller than the width of a human hair. These tiny particles primarily come from motor vehicle exhaust, power plant emissions, and other operations that involve the burning of fossil fuels. Fine particles can travel deep into the respiratory tract, reducing lung function and worsening conditions such as asthma and bronchitis.
The researchers based their fine particle analysis on 11.5 million Medicare enrollees who lived in 204 U.S. counties with populations larger than 200,000. Using billing records for 1999 to 2002, they tracked daily counts of hospital admissions for eight major outcomes - heart failure, heart rhythm disturbances, cerebrovascular events such as stroke or brain hemorrhage, coronary heart disease, peripheral vascular disease or narrowing of the blood vessels, chronic obstructive pulmonary disease, respiratory infection, and injury.
The investigators obtained daily measurements of fine particle concentrations from a network of air monitoring stations provided by the Environmental Protection Agency's Aerometric Information Retrieval Service. The average fine particle concentration for the 204 counties over the three-year period was 13.4 micrograms per cubic meter of air, slightly below the national air quality standard of 15 micrograms per cubic meter for an annual average.
"When we analyzed the data for heart failure, we observed a 1.28 percent increase in admissions for each 10 microgram per cubic meter increase in fine particle pollution," said Francesca Dominici, Ph.D., an associate professor of biostatistics with the Johns Hopkins Bloomberg School of Public Health and lead author on the study. "Most of these admissions increases occurred the same day as the rise in fine particle concentration, which suggests a short lag time between the change in pollution and the subjects' response."
The data also showed that the risk for air pollution-related cardiovascular disease was highest in counties located in the Eastern United States. "Identifying the various factors that might contribute to these differences between eastern and western regions is a very complex question that we must address," said Dominici.
According to Dominici, fine particles pose a significant health problem because they penetrate deep into the lungs, and some may even get into the bloodstream. "Now that we know that inhaled particles can affect cardiovascular and respiratory health, we must identify the specific characteristics of fine particles that produce these adverse health effects," she said. "In the meantime, these findings underscore the need for a national air quality standard that adequately protects the respiratory health of our citizens."