Dangerous dust? Chemicals in plastics are tied to allergies.

Household exposure to synthetic chemicals commonly used in plastics and other products appears to increase a person's risk of developing allergies. At least two such chemicals, called phthalates, are more abundant in dust from homes where children have allergy-related illnesses than in dust from the homes of symptomfree children, a Scandinavian study has found.

Phthalates are ingredients in soft plastics, such as those used to make vinyl flooring. They're also used as softening agents in cosmetics and plastic toys.

To determine whether high concentrations of phthalates in dust correlate with allergies, Carl-Gustaf Bornehag of Karlstad University in Sweden and his colleagues visited the homes of 400 Swedish children. About half the kids had at least two of the following conditions: asthma, eczema, and rhinitis, which is an inflammation of the nose's mucous membrane. The other children selected for the study had none of these.

Children exposed to household dust with the greatest concentrations of di(2-ethylhexyl) phthalate (DEHP) were 2.9 times as likely to have asthma as were children exposed to the lowest concentrations of that phthalate. Similarly, children in homes with the greatest concentrations of butyl benzyl phthalate were 3.0 and 2.6 times as likely as the other children to have rhinitis and eczema, respectively, Bornehag and his colleagues report in an upcoming Environmental Health Perspectives.

Four other phthalates showed no significant link with any of the three disorders.

The new study is the first to reveal different phthalate exposures in children with and without allergy-related illnesses, says toxicologist Gunnar Damgaard Nielsen of the National Institute of Occupational Health in Copenhagen. The allergy-triggering mechanism could be indirect. In mice, Nielsen and his colleagues found evidence that phthalates, while not allergens themselves, amplify the body's response to allergy-causing compounds.

The phthalates in the study may act differently because of their distinct physical and chemical properties, as well as the variations in their abundance in dust, says study coauthor Charles Weschler, a chemist at the Technical University of Denmark in Lyngby. DEHP is the most commonly used phthalate. It's more likely than the other two to come out of plastic in a form that readily attaches to dust particles that can penetrate deep into the lungs, he says.

Flooring materials made from phthalate-bearing vinyl have previously been associated with an increased incidence of asthma, Nielsen notes.

Even so, he adds, "whether there is a causal relationship between phthalates and promotion of asthma is not clear." In its analysis, Bornehag's group didn't include factors that influence the abundance of allergens, such as a home's humidity and cleanliness. Furthermore, Nielsen notes, vinyl flooring is often used in buildings with other cheap materials, some of which may independently promote the growth of allergy-causing molds and dust mites.

To underscore the complexity of identifying environmental triggers for allergies, Nielsen also points out that vinyl flooring is popular in part because it's easy to clean, and cleaning reduces dust and any allergy-triggering material it might carry.