October 24 (HealthDay News) -- High levels of nitrogen dioxide emissions from gas stoves can aggravate asthma symptoms in inner-city children, especially pre-schoolers, a new study says.

Nitrogen dioxide (NO2) is an irritating and toxic form of nitrogen oxide gas that is often present in industrial zones but can also be found at higher levels in poor homes with unvented gas stoves.

Researchers from John Hopkins University, reporting in the October issue of Environmental Health Perspectives, tied asthma flare-ups in young children directly to high concentrations of NO2 in their Baltimore homes, most of which had gas stoves and/or natural gas heat. The stoves or ovens were often used for heating as well as cooking.

"Because using stoves as heat sources is a hallmark of urban poverty, our study tellingly points to how profound and direct the effects of purely social and environmental factors can be on a child's health," lead researcher Dr. Nadia Hansel, a Johns Hopkins lung expert, said in a news release issued by the university. "Doctors caring for children with asthma should always inquire about the home's heating and cooking appliances and urge those using gas-based stoves and space heaters to switch to electric heating and cooking, if possible, or at least properly vent the exhaust gases."

Each 20 point increase in nitrogen dioxide levels led to 10 percent more days of cough and 15 percent more days with limited speech due to wheezing, the researchers said.

Asthma affects 6.2 million children in the United States and is most prevalent in inner-city children. Doctors believe poor access to regular health care and added exposure to indoor allergens such as mouse and cockroach dander, dust, cigarette smoke and automobile fumes make the condition worse for these children.

SOURCE: Johns Hopkins Medicine, news release, Oct. 13, 2008