Water sources from two-thirds of Maine schools have been tested for lead under a mandatory state program aimed at reducing childhood exposure as of Wednesday.

Due to a 2019 law, Maine schools are required to submit water samples for testing from all fixtures used for drinking or cooking by the end of the year. The law applies to public and private schools.

As of Wednesday, 15,091 water fixtures have been tested, with 27% showing lead levels above the state’s recommended threshold of 4 parts per billion.

Federal grants are funding the testing program, however school districts are responsible for remediating water fixtures with lead levels above the state threshold.

Maine’s threshold is far lower than the U.S. Environmental Protection Agency action level of 15 parts per billion. An action level is not a standard for establishing a safe level of lead, however it is the concentration at which the agency recommends remediation. There is no safe threshold for lead exposure.

Lead is a toxin which can impair the development of young children, especially those under age 6, according to the Maine Center for Disease Control website. Children are most commonly exposed through old paint dust, which is “almost always the cause of lead poisoning,” it states.

In water, lead often originates from solder or from brass plumbing hardware.