STATE COLLEGE, — Levels of lead and nitrates in private water wells across Pennsylvania have fallen sharply over the last 25 years, but many wells still don't meet state safe drinking water standards, a study found.

Forty percent of the more than 700 private wells tested statewide over the last two years contained excessive levels of at least one contaminant, according to research from the Penn State Cooperative Extension. Pennsylvania has 3 million people relying on more than 1 million private wells for drinking water.

Specifically, 33 percent of the wells tested had some presence of coliform bacteria, though the state standard is "basically zero," said Brian Swistock, extension water resources specialist.

Coliform bacteria is essentially harmless, but its presence could signal that it might be easier for more dangerous bacteria such as E. coli to contaminate drinking water, Swistock said Tuesday.

The larger issue, Swistock said, is that so many owners of dirty wells were unaware of the problems, in part because the pollutants tested had no obvious taste, stain or odor. The only way to detect the contaminants was through lab testing.

About 20,000 new wells are drilled every year in Pennsylvania, the study said.

The Department of Conservation and Natural Resources requires that private wells be drilled by state-licensed operators, and that reports be filed with the state upon completion of the well.

Wells with good construction were less likely to be contaminated, Swistock said.

However, there are no state requirements for their construction.

The Department of Environmental Protection recommends that homeowners on private wells get water tested regularly by a state-certified lab, spokesman Tom Rathbun said.

DEP recommends that owners should also get wells tested if their property is disturbed for mining, new construction or other reasons.

The Penn State study was funded mainly by the Center for Rural Pennsylvania, a legislative agency of the General Assembly. The private well study was suggested by a member of the center's board, which includes legislators, the governor's office and university officials or professors, said Barry Denk, the center's director.

"To ensure safe drinking water for private water system owners in Pennsylvania, the state should consider using a combination of educational programs for homeowners and new regulations," the report said.

"The combination of these two approaches will make certain that existing well owners will become aware of water quality issues and proper management of wells," it said.

The study also found that 12 percent of wells had levels of lead above the state standard, down from 20 percent in 1993. Swistock attributed that decline to the aftereffects of the federal ban on lead plumbing in 1992.

"That's a real success story," Swistock said.

Just 2 percent of private wells had nitrate levels above state standards, down from 13 percent in the mid-1980s and 12 percent in 1993.

That could be due to the effects of better nutrient management by the state, as well as fewer farms in Pennsylvania, from which potentially harmful runoff could flow into the well, Swistock said.