TUESDAY, March 7, 2006 (HealthDay News) -- More seniors end up in the hospital due to cardiovascular and respiratory diseases on days when air pollution levels rise.
That's the conclusion of a large-scale study in the March 8 issue of the Journal of the American Medical Association that compared air pollution levels to the number and types of hospitalizations occurring at the same time.
"This study provides strong evidence that daily hospital admission rates for cardiovascular diseases and respiratory diseases are higher when the fine particulate matter levels are increased from one day to the next," said study author Francesca Dominici, an associate professor of biostatistics at Johns Hopkins University's Bloomberg School of Public Health.
Dominici said just a small rise -- each 10 micron per cubed meter increment increased -- in the air pollution level results in about 11,000 extra hospitalizations for cardiovascular and respiratory disease.
She said the reason is clear: Small particles of air pollution can travel deep into the lungs.
To get an idea of how small these air pollution particles are, George Thurston, an associate professor of environmental medicine at New York University School of Medicine, said to imagine the width of a human hair. That's about 100 microns. The particulate matter measured in this study was 2.5 microns.
In the late 1990s, the National Ambient Air Quality Standard required a nationwide monitoring system to measure the amount of fine particulate air pollution -- that's air pollution equal to or less than 2.5 microns in size (PM 2.5) -- present on any given day in 204 urban counties.
For the new study, Dominici and her colleagues used information from this monitoring system and compared it to daily rates of hospitalizations for a number of different conditions, including injuries, cardiovascular diseases and respiratory diseases. The hospitalization information came from records of more than 11.5 million Medicare enrollees, who were 65 years and older.
The researchers found that for every 10 micron per cubed meter increment rise in PM 2.5, hospitalizations for heart failure rose by 3,156 per day, respiratory tract infections by 2,085, ischemic heart disease by 1,523, stroke by 1,836 and for chronic obstructive pulmonary diseases such as emphysema by nearly 1,000 per day. The total increase in hospitalizations for each 10 micron per cubed meter rise in fine particulate matter was 11,000 daily.
"I think this is powerful new evidence that fine particulate matter air pollution is indeed a major public health threat," Thurston said.
He pointed out that the researchers didn't find an increase in injuries associated with the days that air pollution was increased, proving the findings of increased cardiovascular and respiratory diseases weren't a chance or random occurrence.
Dominici said the other important finding was that "risks were higher in the Eastern part of the United States."
Both Dominici and Thurston said this was likely because there are more power plants operating in the Eastern portion of the United States than in the West, and power plants are a large source of PM 2.5.
Dominici also emphasized that these results are likely an underestimation of the extent of the problem because they only included people over 65 and monitoring stations are only set up in urban areas. So, while this study was probably the largest done to date on fine particulate matter air pollution, many parts of the country weren't represented.
"This is more evidence that we should do as much as possible to protect the public from this health threat, and the clean air standards are under federal review right now," said Thurston.
"From a policy perspective, this gives more impetus than ever for supporting more stringent clean air standards," he said.
On an individual level, both Dominici and Thurston said there's not much you can do to protect yourself from this type of pollution because it's so small it easily travels indoors. However, Thurston said it probably makes sense to exercise in the morning if you're heading outdoors because this type of pollution is highest in the afternoon.
Additionally, they both said that conserving energy, particularly electricity, helps to keep the air pollution levels lower.
Johns Hopkins has more about fine particulate matter.