Researchers analyzed 28 years’ worth of weather reports in Seattle ending in 1995, and matched the weather data to mortality data. The study found 0.5 percent more deaths from cardiovascular events one day after an increase in stagnant weather, and 2 percent more deaths from respiratory problems and chronic obstructive pulmonary disease four days after an increase in air stagnation.
Stagnant air is measured by the number of hours that the wind speed is 1.5 miles per hour or less. In the Seattle area, whole days may go by without an hour of stagnant air; but it is not uncommon to have days with four to five stagnant hours.
The increase in deaths “confirms the guidelines – if the air has been stagnant and you have pulmonary disease, it’s good to restrict your outdoor activities,” said one of the researchers, Dr. Therese Mar of the EPA Northwest Research Center for Particulate Air Pollution and Health, a program in the UW School of Public Health and Community Medicine.
Researchers are now trying to determine if there is a relationship between the number of deaths and changes in air pollution amounts over the years.
Air quality researchers often use stagnant air as an indicator of the presence of air pollution; they use the weather statistic, in part, because there is no comparable measurement of air pollution itself over 28 years. The researchers conducted this particular study because previous work in their program found that emergency room visits for asthma in children are associated with persistent stagnation.
Other researchers who participated in the project are Dr. Jane Koenig, professor of environmental health, and Dr. Timothy Larson, professor of civil and environmental engineering.
For more information about air quality and health, see http://www.epa.gov/airnow/aqibroch/ on the Internet.