A study released Wednesday by a team of Japanese researchers found emergency room admissions increased when levels of yellow dust originating in China were high.

The team, including Dr. Kayo Ueda, a researcher with the National Institute for Environmental Studies, found the rise could be due to the presence of air pollutants carried together with the yellow dust.

Air pollutants include PM2.5, hazardous particulate matter measuring below 2.5 microns, or 2.5 thousandths of a millimeter, in diameter, which can be absorbed by the lungs and lead to heart and lung diseases. The pollutants are believed to cause asthma, bronchitis and lung cancer.

Ueda and her fellow researchers said they analyzed the cases of about 9,000 adults in the city of Nagasaki who were brought to the emergency rooms between March and May in 2003 to 2007.

The team chose Nagasaki because the had sufficient data on people who were transported to hospitals and other medical institutions mostly by ambulance.

The team's statistical study excluded pregnant women and people with injuries, and factors such as humidity that could have caused people to be brought to the emergency facilities.

Based on their study, the team found the number of people brought to emergency rooms during days with high levels of yellow dust was 12 percent higher than on days without yellow dust. The number tended to increase when yellow dust reached Japan after passing over industrial districts in China's coastal areas at an altitude of less than 2 km, the study showed.

"Air pollutants that come from the industrial areas may have mixed with the yellow dust when it passed at a low attitude," Ueda said.