NEW YORK (CBS 2/WCBS 880) – A group of politicians and parents is demanding that every New York City school built in the middle of the last century be screened for toxic PCBs.

P.S. 199 is one of the three city schools that tested positive for toxic levels of PCBs. All the windows and fluorescent lights have been replaced, but according to the co-head of the PTA, there are still dangerously high levels of PCBs in some of the kindergarten classrooms.

“What is most alarming to the parents is that we have people in our school that are cleaning, that are changing our light fixtures, that are doing a lot of work, but they still don’t understand this material,” PTA co-president Michelle Ciulla Lipkin said. “They don’t understand why our levels are so high, and that is so alarming.”

The teachers union is joining local politicians and parents to demand that the city test all 740 city schools that were built or renovated from 1950 to 1978, when it was still legal to use PCBs.

“We need to move faster now, because the initial results from the pilot program were so alarming, and much higher than anyone thought they were going to be,” teachers union president Michael Mulgrew said.

LISTEN: WCBS 880′s Marla Diamond reports

Mayor Bloomberg has said the removal of PCBs in all city buildings is an “ongoing project.”

Several parents and lawmakers, however, say the city isn’t moving fast enough. P.S. 183 is on the list to be tested next, but that won’t start until next summer.

“They need to be checked, better sooner than later,” parent Mark Garraway said. “I would hate children to get respiratory issues because of failure to act.”

The city agreed to the pilot testing program after the threat of a lawsuit.

PCBs are chemicals which have been known to pose serious risks to children’s nervous and immune systems, as well as hamper a child’s brain development.