BOSTON — Home sellers in Massachusetts have for decades been required to tell potential buyers if toxic lead paint or plaster was detected in tests of the property.

But there are no such mandates for lead found in drinking water pipes inside homes, which environmental groups say poses an equally serious threat to public health.

State lawmakers are trying to plug that loophole in the law.

Legislation filed by state Rep. Russell Holmes, D-Boston, and backed by a dozen lawmakers would add lead in plumbing and water pipes to the list of required pre-sale disclosures.

Another proposal, filed by state Sen. Jason Lewis, D-Winchester, would go further by requiring disclosure of lead found in service lines running to residential properties.

While neither of the bills would require testing or remediation of lead contamination, supporters say it would improve public safety.

In a statement, Lewis said the proposed changes would “help reduce lead exposure by raising awareness of hazards so people can take action to reduce risk, helping renters and homebuyers make more informed decisions and creating market incentives to replace potentially harmful pipes.”

“As a matter of public health, we must take action on this issue,” he said.

Under federal and state law, sellers of homes built before 1978 in which a child under 6 will live must tell prospective buyers or renters if lead has been detected in tests.

If contamination is found, they must also certify that a property has been de-leaded.

The state also requires disclosure of tests for radon gas, a leading cause of lung cancer, before the sale of a private home. If detected over a certain level, it must be remediated.

Public health officials say no amount of lead in water is safe. Even low concentrations can be harmful, particularly for young children and the fetuses of pregnant women.

“The problem of lead in drinking water is pervasive,” said Deirdre Cummings, legislative director for the Massachusetts Public Interest Research Group. “We’re just beginning to realize the terrible health impacts of even low levels of lead in our water supplies.”

So far, the state’s real estate industry hasn’t taken a position against the proposals.

“Our realtors are obviously concerned about lead contamination and public safety and have been supportive of the robust lead law we have,” said Michael McDonagh, general counsel and government affairs director at the Massachusetts Association of Realtors.

“If it’s simply something a matter of requiring sellers to disclose something they already have knowledge of, I think people would generally be supportive of it,” he said.

McDonagh pointed out that potential homebuyers can always request testing for lead, including the pipes within a residence, as part of negotiations with a seller.

“They can do that now, even without this legislation,” he said.

Still, if the legislation were amended to mandate lead testing and remediation that would be a concern for real estate agents, McDonagh said, because it could hurt sales.

Worries about lead contamination were highlighted by the recent crisis in Flint, Mich., where as many as 8,000 children under age 6 were exposed to unsafe levels of lead from 2014 to 2015 after a budget-cutting decision to switch drinking-water sources.

Earlier this year, Massachusetts officials disclosed that water testing at more than 1,000 public schools found a majority had at least one sample showing lead levels above regulatory limit.

The state Department of Environmental Protection has made $2.75 million in grant money available to help schools pay for testing and removal of leaded pipes.

A recent report by the Environmental Defense Fund gave Massachusetts and New Hampshire an “F” for having a lack of policies dealing with lead disclosure.

Several states — including Connecticut, New York and Delaware — have passed laws in recent years mandating disclosure of lead contamination in pipes, the nonprofit said.

The U.S. Environmental Protection Agency requires publicly regulated water systems to test for possible lead contamination in only a small number of homes with lead pipes.

Water managers are required to disclose contamination and take remedial action only if the lead tests show more than 10 percent of sampled homes exceed the standard.

Drinking water suppliers have spent hundreds of millions of dollars in recent years to replace aging lead pipes and upgrade their distribution systems, according to Jennifer Pederson, executive director of the Massachusetts Water Works Association.

“We’re trying to be proactive,” she said. “The water systems have made a concerted effort over the years to upgrade water mains so there’s less lead pipes in service.”

“But it’s up to the homeowner to replace the water pipes on their end,” she said.

Still, recent reports have shown that lead is still being detected in water systems.

Earlier this year, an Associated Press review of federal data found 33 of the state’s water systems were among 1,400 systems serving 3.7 million Americans nationwide that have exceeded the federal lead standard at least once since Jan. 1, 2013.

More than half of the waters systems were privately owned and serve a small segment of the state’s population of 6.7 million, the AP said, but a handful of larger municipal systems have had testing samples above the standard of 15 parts per billion.

For cash-strapped local governments, the price tag for replacing aging water systems has weighed heavily as state and federal funding to fix the plumbing has dried up.

A recent report by state Auditor Suzanne Bump estimated cities and towns will need at least $7.24 billion to upgrade water systems over the next two decades. The report calls for at least $50 million a year in additional state aid to help foot the bill for upgrades.

MassPIRG, which recently gave the state a “D” letter grade for its efforts to prevent lead from entering drinking water at schools, said local, state and federal governments need to figure out a way to fund testing of homes and removal of lead contamination.

“We can’t afford to wait to solve this problem,” Cummings said. “We need to act now.”

Christian M. Wade covers the Massachusetts Statehouse for North of Boston Media Group’s newspapers and websites. Email him at cwade@cnhi.com.