NYCHA says it will test 135,000 public housing apartments to determine exactly how many have lead paint.

The agency is inspecting the apartments using portable X-ray devices that can detect lead through multiple layers of paint. The $88 million testing began at Harlem River Houses on Monday and will continue in other developments next month. The remainder of the city's 175,000 public housing units have either already been inspected or were built after 1978, when the federal government banned lead paint.

Mayor Bill de Blasio said the goal is to get a firm count of how many NYCHA apartments have lead so that it can be abated.

“We want to take the challenge of lead exposure and eradicate it once and for all in New York City,” de Blasio said.

NYCHA said it will post testing results online by May 1st and provide updates every two weeks. Testing will be completed by the end of 2020.