The new NTP Center for the Evaluation of Risks to Human Reproduction will assemble a dozen or more scientists with applicable expertise to evaluate the substances in public sessions, according to a center announcement in the Federal Register. The sessions are tentatively planned for August in the Washington, D.C., area.

The center asked scientists to share their latest data on the substances to be reviewed: butyl benzyl phthalate, di(2-ethylhexyl) phthalate, di-isodecyl phthalate, di-isononyl phthalate, di-n-butyl phthalate, di-n-hexyl phthalate, and di-n-octyl phthalate.

The National Institute of Environmental Health Sciences and the National Toxicology Program, which is headquartered at NIEHS, in January announced the creation of the NTP Center for the Evaluation of Risks to Human Reproduction to evaluate risks to human reproduction and child development for regulatory agencies and the public -- and to point to gaps in knowledge that need to be filled by additional research and testing.

"A decline in human sperm counts over recent decades has been reported but not confirmed," officials said in the January announcement, adding that 5 to 10 percent of couples who want children cannot get pregnant and 3 to 5 percent of newborns have major birth defects.

"The panel will look at data to see how likely it may be that phthalates contribute to these reproductive and developmental problems," Michael Shelby, Ph.D., chief of the Laboratory of Toxicology at NIEHS and director of the project. Some phthalates have already been shown to be carcinogenic at some level in animals. As a result, the makers of plastic toys, teethers and pacifiers say they have reduced or restricted some phthalates' use.