The Trouble with Older Homes
Unfortunately, there's not a certain type of home or even part of the country where the living is easy or healthier when it comes to indoor air, according to the Healthy Indoor Air for America's Homes' Michael Vogel.

Each type of home and locale brings with it unwanted visitors, says Vogel, executive director of the consumer-focused initiative, sponsored by U.S. Environmental Protection Agency, the U.S. Department of Agriculture and Montana State University. But, the bedroom and basement are particularly prone to cultivating airborne health hazards.

"In older homes, you're definitely more likely to find lead-based paints and asbestos," according to Vogel, also a Montana State University professor. Banned for residential use since the 1970s, asbestos and lead-based paint still exist in many homes. Left undisturbed, these contaminants are generally safe and cause no health problems, experts say. However, if disturbed and released in the air during home remodeling projects, lead or asbestos dust can be dangerous.

For example, lead poisoning can damage the brain and permanently effect other organs, and is tied to reduced intelligence and behavioral problems. More than 800,000 American children younger than age 6 have lead blood levels of concern, reports the Centers for Disease Control and Prevention.<

And older homes are more likely to have older fossil fuel heating systems, which pose problems with carbon monoxide and other dangerous gases. However, inhabitants of homes heated by natural gas and newer homes are still at risk. For example, hot water heaters or other appliances not properly venting will emit harmful gases. "Gas ranges and stoves can produce extremely high levels of carbon monoxide," Vogel adds.

"Carbon monoxide is probably at the top of the list [of health hazards]," relating to bad indoor air, says Dr. Clifford Mitchell, an assistant professor in environmental health sciences at the Johns Hopkins School of Public Health. From a public health viewpoint, lead and asbestos are top concerns, as well as so-called bio-aerosols, such as dust mite and cockroach, that cause or trigger respiratory problems.

"In older homes, which are going to be remodeled more often, you'll find more dust and more problems with mold [too]," Vogel says. Older homes don't have a monopoly on mold and mildew, both major sources of allergies and asthma, but are more susceptible to these invaders, as are homes in the Southeast and Pacific Northwest because of humidity. However, humidifiers and water seepage can attract mold and mildew in dry areas.

Newer Homes: Built to Trap Chemicals
"For years, a lot of the focus has been on lead and asbestos in the home, but the more recent emphasis is on indoor allergens and asthma," says Dr. Darryl Zeldin, who heads the National Institute of Environmental Health Sciences' clinical studies program and director of its asthma program. One key suspect for the rise in prevalence of asthma and allergies, which impact nearly a quarter of Americans, are allergens in the home.