"Their attitude is, 'Why take the risk that a product may be harmful if we don't have to?' " he said. Sales at Seventh Generation have grown 30 to 40 percent a year for five years, to hit annual sales of $50 million, he said, led by products like unbleached diapers.

Parents' buying patterns can lead to industry changes. While phthalates can be used in some children's toys in the United States, parental pressure led the Consumer Product Safety Commission in 1998 to ask manufacturers to take them out of teething rings and pacifiers, according to Dr. Welshons. "The science was there for some time before, but until parents exerted pressure, such as by not buying the toys, they didn't change the formulation," he said.

The same grapevine that encourages parents to stop buying some products can help sales of others. Since August, the Center for Environmental Health, a nonprofit group in Oakland, Calif., has sued 24 lunchbox makers and retailers, after their vinyl lunchboxes were found by two independent labs to contain lead. E-mail messages flew from parent to parent.

Cool Tote, a company in Sparks, Nev., that makes lead-free nylon and cloth lunchboxes, found an immediate increase in sales on its Web site. "We started getting a lot more interesting to people," said Bruce Clancy, the chief executive. Another site, Reusablebags.com also started to offer the product line and now sells about 100 Cool Tote lunch bags a week.

In response to public concerns, the Consumer Product Safety Commission tested 60 vinyl lunchboxes made by a variety of manufacturers, including some named in the suits, and found that "in most cases, children would have to rub their lunchbox and then lick their hands more than 600 times every day, for about 15-30 days," to create a health hazard.

Not everyone agrees with the government's conclusions. The safety commission "has always lagged behind the most current science where lead toxicity is concerned," said Dr. Herbert L. Needleman, professor of psychiatry and pediatrics at the University of Pittsburgh School of Medicine and a co-author of "Raising Healthy Children in a Toxic World." "Most scientists who are actively working in the area now agree that there is no safe lead exposure level for children."

A spokesman for the safety commission, Scott Wolfson, said, "We recognize there are differences in the opinions, but we all desire the same thing — that no child have lead poisoning." He added, "There are federally agreed-upon levels of accessible lead beyond which children should not be exposed."

IT may take a long while for parents to get much scientific information on what is toxic to their children. In 2000, Congress authorized the National Children's Study, to follow 100,000 children from the womb to age 21. The goal was to understand how natural and synthetic environmental factors affect child development. The study would also examine why conditions like asthma, developmental disabilities, obesity and childhood cancer were on the rise.