Researchers at the National Institute of Environmental Health Sciences, based in Research Triangle Park, found that people with elevated levels of 1,4-dichlorobenzene, once common in such air fresheners, were more likely to have impaired lung function.

The research, using data collected years ago, doesn't make an airtight cause-and-effect case. But it could be reason enough for some people to avoid all products containing the chemical, said Dr. Stephanie London, the senior NIEHS scientist in the study.

"These are optional things you may just choose to live without. It's not like they are essential to life," said London, a physician who studies the genetic and environmental roots of asthma and other lung ailments.

A trade group whose clients include air-freshener manufactures, however, said Thursday that this study could distort more than inform. Companies that produce so-called urinal blocks already are abandoning 1,4-dichlorobenzene, which easily vaporizes from a solid form, said Andy Hackman of the Consumer Specialty Products Association.

Makers of home air fresheners stopped using the chemical about 10 years ago, he said.

"To a large extent, it's irrelevant to today's products," Hackman said, with one exception being some air fresheners that drivers hang from rearview mirrors. The NIEHS says the chemical also can be present in some mothball products.

When London and colleagues, including NIEHS epidemiologist Leslie Elliott, dug into old data collected to evaluate risks from volatile organic compounds, they saw good reason to suspect harm from 1,4-dichlorobenzene. As blood concentrations of the chemical increased, lung function declined, according to blood and breathing tests conducted between 1988 and 1994.

The harm wouldn't disable healthy people, but it could have noticeable effects on people already living with lung deficiencies, much like consistent exposure indoors to secondhand cigarette smoke, London said.

From London's point of view, the particulars merit more study. Elliott, whom London supervises, is applying for funding for experiments that would test the lung function of participants, expose them to low levels of 1,4-dichlorobenzene and then check to see whether breathing worsened.

Insight into the action of this chemical might shed light on impacts of other volatile organic compounds, which are still found in many products in people's homes, London said. Those include some paints, cleaning supplies, building materials, even upholstered furniture.

"I'm not saying people should run out and panic. But if you are the kind of person like me who likes to limit your exposure, this is something you should think about," London said.

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