Flame retardants spark new concern.

Breakdown products of some commonly used flame retardants may perturb the normal production of sex hormones, according to preliminary test-tube experiments conducted by Dutch and Swedish scientists. The residues are from polybrominated diphenyl ethers (PBDEs), which are used to fireproof products ranging from furniture cushions to computer cases. Many surveys of blood chemistry have revealed that PBDE residues circulate in most people.

The researchers used cultures of human adrenal gland cells, which are normally responsible for making weak male hormones such as dehydroepiandrosterone, or DHEA. Ordinarily, these steroids circulate throughout the body and transform into potent sex hormones, such as estrogen and testosterone. Pivotal to creating the feedstock steroids is an adrenal enzyme designated as CYP17.

Thomas Sanderson of the University of Utrecht in the Netherlands and his coworkers measured the enzyme's activity in cells that had been incubated with various PBDEs or with breakdown products created as the body attempts to rid itself of PBDEs.

Animal research has indicated that some PBDEs, such as BDE-47 and BDE-99, may impair reproductive development and that BDE-99 may also impair learning and memory (SN: 10/25/03, p. 266).

Sanderson's team tested several common PBDEs, none of which had an effect on CYP17 activity. However, products from the metabolic breakdown of BDE-47, BDE-99, and, to a lesser extent, BDE-49 reduced the enzyme's potency.

"How, we're not sure," Sanderson acknowledges, but he adds that the finding "would suggest that at high concentrations, these metabolites could impair [sex hormone] synthesis--which would be deleterious."

Sanderson cautions that the PBDE and metabolite doses he used in the test-tube studies were high. His group has now begun studying the effects in rats of doses closer to those found in people and the environment.--J.R.