The ability of the blood vessels to control blood flow was impaired in adults with diabetes on days with elevated levels of particles from traffic and coal-burning power plants.

The researchers evaluated several kinds of fine particles found in urban air pollution. These included sulfate particles, which come mainly from coal-burning power plants, as well as ultra-fine particles and black carbon soot, which are generated primarily by diesel- and gasoline-powered vehicles.

"Our strongest finding was that blood vessel reactivity was impaired in people with diabetes on days when concentrations of sulfate particles and black carbon were higher," said Marie O'Neill, Ph.D. "Impaired vascular reactivity has been associated with an increased risk of heart attack, stroke and other heart problems."

"Previous studies have shown that when air pollution levels are higher, people with diabetes have higher rates of hospitalization and death related to cardiovascular problems," said NIEHS Director David Schwartz, M.D. "These changes in blood vessel reactivity may help explain this phenomenon."

Researchers recruited 270 greater Boston metropolitan residents and divided them into two groups. The first group consisted of subjects with a positive diagnosis of type I or type II diabetes. The second group included subjects who were not diabetic, but who had a family history of diabetes or blood sugar levels slightly higher than normal.

The investigators used a technique called brachial artery ultrasound to assess blood vessel response in the study subjects. The measurement was obtained by applying a pressure cuff to the subject's upper arm and cutting off the blood flow through the arm's main artery. Researchers then released the cuff, allowing the blood to rush through. The researchers then evaluated changes in the diameter of the main artery as a result of the physical stress placed on the vessel.

"We observed an 11 percent decrease in diabetics' vascular reactivity on days when sulfate particle concentrations were higher than normal," said O'Neill. "We also noted a 13 percent decrease in their vascular reactivity on days with higher-than-normal black carbon concentrations."

Research conducted in Montreal, Quebec from 1984 to 1993 showed that hospitalizations and deaths related to cardiovascular problems increased among diabetics when levels of air pollution were higher.