AUGUSTA — A legislative effort to promote well-water testing in Maine was nixed this week when legislators failed to override a veto from Gov. Paul LePage.

The bill, sponsored by Rep. Drew Gattine, D-Westbrook, was a response to recent scientific findings on arsenic, a carcinogen occurring naturally in the state’s bedrock, which is a particular problem in central and Down East Maine. Statewide, 150,000 people – one in 10 residents – could be drinking from wells with high arsenic concentrations, according to a Dartmouth University study.

When it was introduced, Gattine’s proposal would have mandated testing on new wells and imposed fees to be used by the state to fund education and remediation for low-income Mainers, but it was scaled back to fund education programs by imposing fees only on tests conducted at the state-run Health and Environmental Testing Laboratory.

The bill passed last month in both chambers of the Legislature in bipartisan votes, but in a Friday veto letter, LePage called the bill “unnecessary,” noting that from 2003 to 2012, the number of Mainers who reported knowing whether their well had been tested rose from 26.5 percent to 45 percent. The governor said the bill would assess fees “to support work that is already being done.”

The House vote fell four votes shy on Tuesday of the 98 needed to override the veto. The Maine Department of Health and Human Services does outreach on well testing under existing resources and won a $300,000, two-year grant in 2013 to support testing at three Healthy Maine Partnerships, but the grant ends this year and advocates say the state needs a steady stream of education funding to increase testing.

“We will continue to try to make sure that people know what they need to do in terms of testing and keeping their kids and themselves safe,” Gattine said.

In the initial House vote, Gattine’s bill, L.D. 1162, was backed by 27 Republicans, including four who represent parts of Kennebec County, where 29 percent of private wells tested by the state from 2005 to 2009 had higher concentrations than the federal arsenic standard for public drinking water, more than any other Maine county.

The issue gained more attention last year, when scientists from Columbia University and the University of New Hampshire released a five-year study of 272 students in grades 3 through 5 at schools in Manchester, Readfield, Monmouth, Wayne, Mount Vernon and Hallowell who were exposed to arsenic in water. It found that exposure to even low levels could lower IQ levels by as many as six points on a test.

One of those Republicans who switched votes to oppose the bill, Rep. Randall Greenwood of Wales, said he has treated his home for arsenic. But in the initial vote, he was “unaware” that the bill would have affected only the state laboratories and said it wouldn’t have accomplished much. But he called arsenic a big problem, saying he hopes the department can fund outreach with existing resources.

But Emma Halas-O’Connor, a coordinator with the Environmental Health Strategy Center, a group that fights toxic chemicals, said in a news release that “this problem isn’t going away unless we take action.”

“We’re committed to continuing our efforts to promote safe drinking water beyond this legislative session,” she said.