Water suppliers across New York — including schools, hospitals and mobile home parks — will be required to test for at least three unregulated contaminants, including a probable carcinogen found in trace amounts in Long Island’s aquifers, under the state’s just-passed $163 billion budget.

The legislation also sets up a 12-member water quality council that is tasked with recommending when additional contaminants should be added to the testing list or whether specific drinking water standards should be set outside of what federal regulations require.

“We have to get ahead of some of these issues out there,” said Sen. Todd Kaminsky (D-Long Beach). “This clearly shows having clean water is a serious priority for the state.”

State officials said the new regulation will be the first in the nation requiring nearly all water suppliers to test for contaminants.

Testing will be required every three years for the probable carcinogen 1,4-dioxane, as well as for perfluorooctanoic acid, or PFOA, and perfluorooctane sulfonate, or PFOS.

The provision applies to public and private suppliers that provide water to at least five connections year-round or regularly serve 25 residents, or to entities that provide water regularly to the same 25 people more than four hours per day for an extended time.

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Before the regulation passed Sunday as part of the budget, there was no state requirement for the testing. The initiative is modeled on a U.S. Environmental Protection Agency program that requires all large water suppliers and a sampling of providers serving less than 10,000 people to test for up to 30 unregulated contaminants every five years.

Gov. Andrew M. Cuomo has repeatedly called that population cutoff a loophole, saying it leaves out about 2.5 million New Yorkers served by small water systems.

“We’re going to have a lot more data, a lot more testing going forward,” said Martin Brand, remediation and materials management deputy commissioner for the state Department of Environmental Conservation.

The three chemicals that water suppliers initially must test for showed up during an EPA survey, the results of which were released last year.

The man-made chemical 1,4-dioxane, which is used as an industrial solvent and in consumer products such as detergent and shampoo, was found in Long Island’s groundwater. The highest concentration in the nation was detected in a Hicksville Water District well that has since been taken offline.

In the EPA survey, 71 percent of water suppliers tested on Long Island found the chemical in concentrations high enough to present a 1-in-a-million cancer risk after prolonged exposure. Nationwide, only 4 percent of suppliers tested had similar concentrations.

PFOS, which can affect the immune system, thyroid and other functions, was found near Francis S. Gabreski Air National Guard Base in Westhampton Beach. More than 50 homes using private wells nearby have been connected to public water supplies.

“It will be good to find out if the larger systems are representative of the smaller systems,” said Brad Hutton, deputy commissioner in the state Health Department’s Office of Public Health.

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About a decade ago, authorities in California required all suppliers to test for the unregulated chemical perchlorate, but the state has no current protocol requiring periodic testing, said Robert Brownwood, an assistant deputy director for the California State Water Resources Control Board.

“It’s about getting a handle on whether or not you’ve got a risk to manage,” said Steve Via, director of federal relations for the nonprofit American Water Works Association.

Water suppliers will have to use accredited labs but can seek a hardship waiver for the state to cover costs, according to the legislation.

The Seaview Association on Fire Island runs the Seaview Water Co. and provides water to 360 homes from April through November, said Suzy Goldhirsch, the association’s first vice president.

“If there is enough suspicion on the part of the experts that this is important to track, we’ll track it,” she said.