Water tested by the Pittsburgh Water and Sewer Authority included 7.05 parts per billion (ppb) of lead—less than half of the 15 ppb lead action level set by the U.S. Environmental Protection Agency and Pennsylvania Department of Environmental Protection.

Samples were collected from 136 houses with a known lead service line or a history of lead lines between July and December 2021.

PWSA officials say the drop is thanks to orthophosphate, a food-grade additive which forms a “protective layer” inside of lead lines and helps prevent corrosion. Orthophosphate was initially added to the water supply in April 2019, while PWSA works to replace all of the lead lines in the city.

PWSA first came into compliance with the Lead and Copper Rule, which regulates lead and copper in drinking water, in July 2020. Test results showed a 20 year low of 5.1 ppb.

This result is only slightly above PWSA’s lowest lead testing result in over 20 years, 5.1 ppb, which was reported in July of 2020.

Since 2016, PWSA has replaced more than 8,800 public lead lines in the city. It has an estimated 8,000 lead lines left to replace.