Low doses of one of the most commonly used softeners in plastics can aggravate dust-mite allergy, researchers report.
The plasticizer di(2-ethylhexyl) phthalate (DEHP) is ubiquitous in air, water, and most people’s bodies. It’s in plastics used for toys, food packaging, medical products, and housewares.
A few earlier studies had correlated allergy severity with exposure to DEHP in people (SN: 7/24/04, p. 52: Available to subscribers at Dangerous Dust? Chemicals in plastics are tied to allergies). To investigate such associations, physician Hirohisa Takano of the National Institute for Environmental Studies in Tsukuba, Japan, and his colleagues repeatedly injected mice with an allergen produced by dust mites as well as with pure vegetable oil or oil laced with various doses of DEHP.
The allergen, injected into the animals’ outer ears, caused swelling, skin thickening, and some wounds at the injection sites. These symptoms were moderately to dramatically worse in the animals exposed to 1-to-20-microgram doses of DEHP, compared with the reaction in mice receiving no DEHP or 100-µg DEHP doses. Pollutants that resemble hormones, including some phthalates, can be more toxic at lower doses than at higher ones.
In this study, mice getting the lowest DEHP dose had nearly double the number of certain inflammatory white blood cells at the injection site as did mice getting pure-oil injections or the high-pollutant dose. The revved-up production of the cells, which can damage healthy tissue, paralleled higher amounts of other allergy-promoting agents in these mice.
The doses of the plasticizer given to the mice “are comparable to the recently calculated daily [human] intake,” Takano’s team notes in the August Environmental Health Perspectives.