The Pittsburgh Water and Sewer Authority remains out of compliance with federal standards for lead in drinking water.

December tests showed that of the 161 homes sampled, 24 had lead levels at or above the EPA threshold of 15 parts per billion. That’s more than 10 percent of homes sampled, which is the metric used by the federal government to determine compliance.

“The 90th percentile is not an average of the presence of lead across PWSA’s water system, but rather a calculation to determine if 10 percent of the worst-case scenario sites that were sampled exceeded the lead action level,” the authority said in a press release.

PWSA said the latest results don’t reflect recent lead line replacements, as only homes known to have lead pipes or solder are included in testing.

The authority first exceeded the federal lead standard in the summer of 2016. Since then, PWSA has been required to replace thousands of lead lines and perform regular lead testing. Tests from summer 2018 showed the authority was in compliance, with a 90th percentile lead level of 10 parts per billion. The authority must continue to test for lead every six months until two consecutive tests show compliance with the federal standard.

PWSA plans to start using a new chemical, orthophosphate, to prevent lead from pipes from leeching into the water. Executive Director Bob Weimar has said that the chemical will be more effective than current corrosion control measures.

According to the EPA, there is no safe level of lead in water.