Maine has the highest prevalence of asthma in the nation, according to a new survey by the Centers for Disease Control and Prevention in Atlanta.

The national study of more than 180,000 people showed about 8.9 percent of Mainers say they currently have asthma compared to a 7.2 percent nationwide average.

“We were surprised that Maine is number one,” said Edward Miller, president of the Maine chapter of the American Lung Association. “That should trigger the same sort of public health reactions as when we found out Maine was number one in young adult smoking.”

The study is important because it is the first time the CDC has done a major survey of the rate of asthma across the 50 states. Miller said he knew Maine would rank among states with high asthma rates despite the widely held belief that urban dwellers have more asthma than rural dwellers.

He explained about four years ago his organization did a small, informal study in Maine that hinted at the problem. Those findings startled a visiting CDC expert who called them incredible at the time, Miller said.

People in cities may have to deal with high concentrations of diesel fumes and other airborne contaminants that trigger asthma, but many Mainers live in rural houses with molds and poor ventilation, Miller said.

Scientists are working to determine the sources of asthma, a chronic ailment that causes the lungs’ airways to constrict and may be accompanied by wheezing and coughing. In an asthma attack, the immune system identifies a substance like animal dander as a threat, unleashing a reaction. Though the dander poses little danger itself, the system senses a significant enemy.

Although the exact causes of asthma aren’t understood completely, Dr. Dora Ann Mills, director of Maine’s Bureau of Health, said indoor and outdoor air quality are two leading culprits.

Maine has a higher percentage of older homes than many states, and when they are renovated to make them weatherproof, ventilation is given little attention, she said. With tight weatherstripping and little air movement, houses trap airborne particulates that can trigger asthma. Smoke from wood stoves and cigarettes and vapors from household cleaners contribute to poor indoor air quality, she said.

Jan Thompson, pediatric asthma educator for Eastern Maine Medical Center, said many more cleaners are being used today that can pollute indoor air.

“We also have one of the highest rates of smoking and that’s certainly going to contribute to triggering asthma,” Thompson said. Even smoking in the cellar can pollute a house’s air, she said.

While asthma experts are more worried about indoor air quality, outdoor air quality also has its place in causing asthma, they say.

Maine sits at the end of the jet stream in the United States, which brings it contaminants released across the nation. One particularly bad problem is industrial pollution from smokestacks in the Midwest, she said.

Maine’s asthma rates weren’t that far ahead of other places. Besides Maine, the states with the highest current rates were Arizona, Ohio, Wyoming, Massachusetts, Oregon, Rhode Island, Wisconsin, Montana, Nevada and New Hampshire.

Nevada had the highest rate of people – 13.4 percent – in the country who said they have suffered from asthma at some time in their lives. Maine was the second-ranked state by that measure, at 12.5 percent.

The CDC reported that no regional pattern could be determined. However, the prevalence of asthma decreased as family income increased. Also, women are more likely to have asthma than men, the study found.

Asthma is the only chronic disease in Maine that is as prevalent among the young as among adults, Mills said.

Mills and Miller both said the emphasis should be on getting people to better manage the disease. Mills suggests those with asthma should routinely see a doctor who has an interest and expertise in the disease.

In addition, every hospital in the state has an asthma educator who is available to educate the public and physicians about the best ways to control the disease in individuals, Miller said.

“Asthma is treatable and manageable,” Mills said.

Maine is among a handful of states that recently won CDC grants to study asthma trends.

“This is a snapshot in time that we have in this study,” Miller said. “We need more information.”

Asthma rates have more than doubled nationally since 1980. One theory is that germ-conscious Americans are shielding their infants so much that immune system development is stunted, and immune cells overreact to normally harmless substances like dust.