A third round of tests on drinking water at Jefferson Elementary School shows some fixtures, valves and water lines are still leaching high levels of lead, according to Medford School District officials.

A third round of tests on drinking water at Jefferson Elementary School shows some fixtures, valves and water lines are still leaching high levels of lead, according to Medford School District officials.

Out of 80 water samples, 15 on Monday showed levels considered unacceptable by the Environmental Protection Agency.

Schools are required to take actions to reduce the amount of lead in water once it reaches 15 parts per billion, the EPA stipulates.

Fixtures, valves and water lines were replaced in the areas with unacceptable amounts. Results from yet another round of testing are expected Thursday, said Medford schools Superintendent Phil Long.

"It's really been a process of elimination," Long said. "We are essentially following the EPA protocol until we finally find where all the lead is coming from."

He said the district hopes to reduce lead levels to less than five parts per billion. Correction: See below.

Even at small amounts, the toxic metal can have harmful health effects, including behavioral problems and learning disabilities, according to the Environmental Protection Agency. Lead is most dangerous to children 6 and younger who may sustain developmental delays as a result of exposure. In adults, it is more likely to cause high blood pressure and kidney problems. The main route of exposure is breathing in lead paint chips. About 10-20 percent of exposure comes from drinking water, according to the EPA.

— Paris Achen

Correction: The goal for reduced lead levels was misstated in an earlier version of this story. This version is corrected.