A new study is linking many composting facilities on Long Island to major groundwater contamination in surrounding areas.

The Suffolk County Department of Health study took 233 samples of groundwater from 36 wells around 11 composting facilities across the Island. The results showed all the test sites had high levels of toxic metals, including manganese. One site had manganese levels 160 times greater than normal groundwater standards.

The facilities include four in Manorville, two in Yaphank, and one each in Speonk, Ronkonkoma, Eastport, East Farmingdale and Medford.

While manganese at a low level is OK in groundwater, environmentalists say the Department of Conservation must now step in to regulate compost facilities further to prevent any more groundwater contamination.

"It's particularly troubling since manganese is linked to impaired nervous system development, as well as brain development in children," says Jordan Christensen, of the Citizens Campaign for the Environment.

Long Island Compost in Yapank says it was informed about its groundwater pollution a few years ago by the state and has implemented procedures to reduce the pollution. It tells News 12 Long Island that "this is obviously of great concern, which is why we have taken an active leadership role in addressing these findings."

The Suffolk County Water Authority says residents should not be concerned about their drinking water. They say they are actively monitoring all of their drinking water for any increase in pollutants.

The Department of Environmental Conservation told News 12 it's in the process of changing the rules when it comes to regulating composting sites.

It will be holding a public comment session on the new rules later this month.