WASHINGTON -- Babies and toddlers have a 10 times greater cancer risk than adults when exposed to certain gene-damaging chemicals, the government said Monday, in proposing tougher environmental guidelines that would take into account the greater hazards to the young.

If its guidelines are made final, the Environmental Protection Agency would for the first time require that the substantially greater risk to children be weighed in the development of regulations covering a variety of pollutants.

While scientists have long known that young children are more vulnerable than adults to gene-harming chemicals, this is the first time the EPA has formally proposed calculating the difference in assessing the danger from some pesticides and other chemicals.

The guidance on cancer and children, which must still be reviewed by EPA's panel of science advisers and has to be subjected to a lengthy process before becoming final, is part of a broader reassessment of how the EPA evaluates cancer risk.

Environmentalists said they welcomed the EPA acknowledging the increased risk to children from some cancer-causing chemicals.

The document on the risks to children focuses on so-called mutangenic chemicals that cause irrecoverable damage to genes, altering the DNA, and making the individual more susceptible to cancer later in life.

Exposure to these chemicals cause a 10 times greater risk of a future cancer in children under 2 years old and fetuses where the mother is exposed, the EPA said.