An Environment Agency committee on Tuesday added a plastic-softening chemical to its priority list of suspected hormone disrupters after finding it in high concentrations in a study of umbilical cords.

Diethylhexyl phthalate (DEHP) -- commonly used in items such as transparent food-handling gloves and the packaging for "bento" boxed lunches -- is the eighth substance to be added to the Environment Agency's priority study list for fiscal 2000. The agency will evaluate the risk it poses to humans through laboratory animal tests and other experiments.

The agency plans to examine the potential risks of a total of 40 substances in the three years from fiscal 2000.

Results from U.S. laboratories have shown that DEHP impairs the sexual function of male rats at concentrations of 500 parts per million.

The chemical was subsequently upgraded in the United States to the level of "serious concern" and targeted for further study.

A domestic study of postbirth umbilical cords found the chemical in six of 10 surveyed, with the highest showing levels of 160 ppm.

In Japan, DEHP will join a list of seven other chemicals identified as most likely to disrupt hormones, out of 65 substances earmarked for further study.

Some so-called environmental hormones have been shown to cause irreversible changes when present in minute concentrations in the womb, affecting brain, sexual and immune system development.

Experts say there are around 300 synthetic chemicals suspected of being endocrine disrupters, but the number will likely grow.

There is still no internationally accepted definition of what an endocrine-disrupting chemical is and how the chemicals may wreak havoc on the endocrine system is still being researched as countries struggle to develop standards for screening, testing or monitoring the chemicals.