The state’s proposed guidelines for cleansing toxic waste sites would fall far short of ensuring adequate cleanups at tens of thousands of locations around New York, threatening drinking water supplies and posing other health risks, environmental groups said yesterday.

The groups say the Department of Environmental Conservation’s planned regulations, required under a 2003 law, would set up different tiers for cleanups, depending on the proposed use for the area. The program offers tax incentives for cleaning up former industrial sites, called brownfields.

There are 1,788 sites being remediated under the state’s program. The DEC does not track the number of brownfields in the state.

In some cases, lead levels would be limited to 63 parts per million, the normal level for state rural areas. But for other industrial sites, the DEC would allow 3,900 parts per million, posing a danger to workers and a threat to ground water, the groups said. In most cases, the DEC, which took two years to put the regulations together, would not insist on the higher standards, an employee of the New York Public Interest Research Group, Laura Haight, said.

Contamination from those sites could easily migrate to other areas through ground water or chemical vapors, putting nearby homeowners at risk, an employee of the New York Sierra Club chapter, John Stouffer, said. In some cases, the DEC would allow a company to simply cover a contaminated area with sod.

“That means what’s standing between your kids and lead poisoning is a layer of green grass,” he said. “Perhaps you feel comfortable with that. I don’t feel comfortable with that.”