BOSTON, OCT. 17 -- Walls painted with latex paint that was manufactured before August can give off enough mercury to be potentially harmful, especially to children, according to a new study.

The study, published in Thursday's New England Journal of Medicine, found relatively high levels of mercury in the bodies of people whose homes were painted inside with latex paint that contained mercury as a preservative.

Because of the problem, the Environmental Protection Agency prohibited adding mercury to paint after Aug. 20. However, paint manufactured before the ban can still be sold.

Experts estimate that until recently, about one-third of all interior latex paint contained varying levels of mercury. Oil-based paint does not contain mercury.

The study was conducted on people whose homes had been painted with mercury-bearing paint during the preceding month. Their bodies contained almost four times as much mercury as the bodies of people not exposed to the paint.

None of the exposed people appeared to be sick. However, some had mercury levels in their bodies that have been associated in the past with symptoms of mercury poisoning. The mercury levels were highest in children.

"If I was a consumer, I would contact the paint company to determine if the paint I was using had mercury in it," said Dr. Mary M. Agocs of the federal Centers for Disease Control, principal author of the study. "Whether or not paint has mercury, we recommend that people ventilate their houses when painting."

Health officials do not recommend removing latex paint from walls.