The New Jersey Department of Health released new guidelines this week for testing for dangerous mercury vapors in the state’s schools.

Mercury vapors can’t be seen or smelled. Vapor exposure at any level can be dangerous, potentially causing nervous system and kidney damage. Schools throughout the state could potentially be exposing students to mercury vapors via the schools’ floors.

“On lead in water, schools had to do testing and submit it,” says New Jersey Work Environment Council executive director Debra Coyle McFadden. “We would like to see the same thing done with these floors.”

Phenylmercuric acetate (PMA) is used to treat rubber-like polyurethane floors, commonly found in school gyms. Sometimes wooden floors are built over them. PMA breaks down over time and releases mercury vapors.

The state Health Department is now recommending that schools have floors tested.

“Much more needs to be done. We don’t know how widespread this issue is,” McFadden says.