BOSTON (AP) _ Homeowners should air out their houses when painting inside with latex paint because of the possibility of mercury fumes, health experts said today.

Federal researchers reported in the New England Journal of Medicine that hazardous traces of mercury were found in people's bodies after they painted with latex paint containing mercury as a preservative.

Mercury poisoning can cause a variety of problems, including leg cramps, rash, low fever, personality changes and nerve problems.

Because of the danger, 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, one-third of all interior latex paint contained mercury. It was added to prevent fungal and bacterial growth and prolong shelf life. Oil-based paint contains no mercury.

''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. ''Whether or not paint has mercury, we recommend that people ventilate their houses when painting.''

She said mercury levels are probably highest during the first few weeks after the paint is applied. She did not recommend removing latex paint from walls.

Agocs is a researcher with the federal Centers for Disease Control in Sacramento, Calif.

Her study was conducted on 74 people living in 19 suburban Detroit houses that had been painted about a month earlier with mercury-bearing paint.

Their bodies contained almost four times as much mercury as did 28 people in 10 houses who did not use the paint.

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

Concern about mercury in paint arose last year after a 4-year-old Michigan boy suffered mercury poisoning when his home was painted.