By Cleve Bryan

TRENTON, N.J. (CBS) — Water tests revealed high lead levels in 20 out of 26 Trenton public school buildings. The testing which began in summer took samples from faucets and drinking fountains.

The federal “action level” for lead is 15 parts per billion and in one instance a sink showed levels as high as 2,100 parts per billion.

Health officials say lead exposure can cause development disabilities, especially in small children.

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The Trenton School District says they have shut off contaminated drinking water sources where they could and put up warning signs on faucets they couldn’t shut off. They have also begun replacing some plumbing components.

In July the state Board of Education mandated all public schools test water for lead this year and make results public.

“We will do what we need to do to get safe drinking water and that’s why we’re doing the testing. That’s why I required the testing- to find out,” Governor Chris Christie told Eyewitness News on Wednesday.

Isles, a Trenton-based community development and environmental organization has been raising flags about lead exposure to children for decades.

They say, mostly because of old paint and partly because of water, children in 13 New Jersey communities have more lead in their blood than children in Flint, Michigan.

Isles president Martin Johnson says schools need to whatever is necessary to get the lead out.

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“We have to come to terms as a society because we’re at a point now where it’s really expensive to not solve this problem. It’s going to be expensive to solve this problem but it’s really expensive not to solve this problem,” says Johnson.