New government regulations proposed to control lead in drinking water could affect more than half of all U.S. water suppliers and could cost families as much as an extra $340 in annual bills.

The Environmental Protection Agency has proposed the sweeping new controls on lead in an effort to reduce health risks from the toxic metal for 138 million Americans, particularly children.EPA Administrator Lee Thomas said Wednesday that the new regulations, which face 60 days of public comment before they can become law, would be worth all extra costs because of the widespread health benefits.

"This proposal will reduce lead in the drinking water of 138 million Americans and will be especially beneficial to young children, who are at much greater risk than adults," Thomas said.

Even relatively low levels of lead in blood can reduce birth weight, cause premature delivery and impair physical and mental development of children.

In adults, low levels can cause hearing loss and increase blood pressure while high exposure can cause anemia, kidney damage and mental retardation.

The current lead standard was set in 1975, but EPA officials said a tougher standard is needed in view of recent health studies showing humans are more sensitive to lead contamination than previously thought.

The new regulations would be expected to affect more than half of all U.S. water suppliers, officials said, and could cost a family anywhere from an additional $1 to $340 a year on a water bill, with those served by smaller systems bearing the highest costs.

For systems with persistent lead problems, the government would require public education programs in which water suppliers would help homeowners identify lead contamination problems in their plumbing.

The two-pronged EPA program would reduce by tenfold the maximum allowable levels of lead in drinking water as it leaves local treatment plants.

But EPA officials said the major thrust of their program was aimed at reducing lead contamination that occurs when drinking water leaves the treatment plant and enters distribution and home plumbing systems.

They said most lead gets into drinking water through corrosion of pipes and other plumbing fixtures made of lead and the acidity of water was the key factor in determining lead leaching rates.

The new rules would impose requirements on water supply systems to monitor the acidity of their water and take steps to reduce acidity if it is found to be too corrosive or lead levels are too high.

Under the program, corrosion-control measures would be required if water samples taken at customer taps contain more than 10 parts per billion of lead or show acidity levels below eight on the pH scale. Samples would have to be taken in buildings most likely to have lead problems.