Washington ? The government proposed tougher guidelines Monday for evaluating cancer risks to children on grounds the very young may be 10 times more vulnerable than adults to certain chemicals.

The guidelines, when made final after a review by the Environmental Protection Agency’s science advisory board, would dramatically alter current policy, which assumes cancer risks to a fetus or an infant are no greater than for a similarly exposed adult.

For the time being, the increased scrutiny would be limited to assessing a group of chemicals that damage a person’s genes by causing them to mutate so that cancer may form more easily later in life. Among these are some pesticides as well as a number of chemicals released in combustion or used in the making of plastics.

The agency said as more information was developed, other cancer-causing pollutants, not those that cause gene mutations, might also be brought under the new guidelines if they were found to pose heightened risk to children.

How to assess cancer risk to the very young from environmental pollution has been an issue vexing the EPA for years. This would be the first time the EPA has proposed formally taking into account the differences between exposure to an adult and a baby or toddler in assessing cancer risks.

The final guidelines are to be reviewed by the EPA science advisory board in May, with a final document to be issued by summer.

The proposed guidelines on risks to children are part of a broader effort by the agency to overhaul the way it evaluates scientific evidence to determine whether to regulate a chemical as a carcinogen.

The EPA also unveiled broader guidance Monday that attempts to refine and make more precise how EPA scientists evaluate cancer risks when deciding how to regulate a chemical. The new guidance would recommend that scientists give greater weight to the latest science and try to develop a more complete picture, said Farland.

But the EPA viewed the question of exposure to children so significant that it decided to develop a separate guidance paper on risks of cancer to the very young, assuming for the first time that fetuses, infants and toddlers are substantially more vulnerable.