LEWISTON – Arsenic levels in an estimated 20 percent of Maine’s public water supplies are higher than those now considered safe for human consumption, according to state officials.

For Mainers who draw their water from private sources, the percentage could be higher.

Arsenic, a common element in the Earth’s crust, has been linked to bladder and lung cancer and other illnesses.

Surface water is relatively free of arsenic, which collects in rocks and seeps into underground water sources, according to state geologist Robert Marvinney. Arsenic has never been a problem in places such as Lewiston-Auburn, Greater Portland and other large water systems that draw from lakes and ponds.

Tests by the state of arsenic levels in water come at a time when the Bush administration has delayed lowering the federal limit on arsenic, pending further study.

State toxicologist Dr. Andrew Smith said the current federal arsenic standard of 50 parts per billion presents a lifetime risk of cancer at 1 person in 1,000 – a level he said is widely recognized as too risky.

Smith said he recommends a 10 parts per billion limit endorsed by the World Health Organization in 1999, which lowers the risk to 1 in 10,000.