Employers must have proof of potential fetal damage before they can fire or refuse to hire pregnant or fertile women in jobs with exposures to toxic chemicals or radiation under new federal guidelines.

"A policy that expressly excludes women on the basis of pregnancy or capacity to become pregnant on its face discriminates against women on the basis of sex" in violation of a 1982 amendment to the Civil Rights Act, the Equal Employment Opportunity Commission said Monday.To justify such exclusions, the EEOC said employers must support their decisions with "reputable, objective, scientific evidence" that a hazard adversely affects the potential offspring only through the female parent and not the male.

"This approach prevents unnecessary limitations on women's employment opportunities, while preserving the employers' - and society's - legitimate interest in protecting the health of offspring."

The commission addressed the issue amid a growing log of court cases and estimates that as many as 15 million to 20 million jobs in the country expose workers to chemicals that might cause reproductive injuries.

In addition, new "high tech" industries are posing previously unsuspected hazards. "Video display workers and semiconductor manufacturers, in particular."

While evidence so far of reproductive risks is largely inconclusive, the commission said, the "same impulse that has led some employers to exaggerate the risks of employing handicapped workers can also lead to exaggeration of risks to offspring."