Philadelphia water officials seek source of iodine

City and state officials are working to determine the source of elevated levels of iodine in Philadelphia’s drinking water.

A federal monitoring program, RadNet, found levels of iodine-131 higher than federal limits several times since 2007. City officials said Monday they didn’t learn about it until last month.

Philadelphia Water Department officials said drinking water tested in April and May has been well under the maximum contaminant level and is safe to drink. Most experts say, even at the highest levels found in recent years, the water posed no short-term public health threat.

Still, officials are testing waste-water treatment plants to figure out where the contamination is coming from–and get levels closer to zero. The higher levels could be the result of a cumulative effect of iodine used in cancer treatments.

“Really, what we’re trying to narrow down is this one, single bad-actor facility with a smoking gun,” said Chris Crockett of the Philadelphia Water Department. “Or is this just a combination of many people getting thyroid treatment and a cumulative effect?”

The Environmental Protection Agency’s John Capacasa said RadNet is not a public health tool, and the EPA doesn’t routinely share its findings with municipalities.

“Its design was not for routine compliance with the Safe Drinking Water Act,” Capacasa said, “but really looking for large-scale events such as terrorist incidents or other man-made threats to the environment.”

Philadelphia tests for a family of radioactive materials, including iodine, once every nine years to comply with federal standards. The last test, in 2002, showed normal levels.

In high doses, iodine-131 has been linked to cancer.