The EPA said Monday the chemicals are leaking from old fluorescent light fixtures.
Inspectors found PCB contamination at a Staten Island school earlier this month.
The chemicals were widely used in construction from the 1950s until to the 1970s.
The contamination does not pose an immediate health threat, but officials say long-term exposure to PCBs can cause cancer and other health problems.
New York City is working with the EPA to conduct the inspections and take remedial action.