BY JEFF DONN
Associated Press

A common fern has been found to soak up extraordinary amounts of arsenic without any ill effects, potentially offering a natural way of cleaning up polluted soil and water.

The plant, known as the brake fern, grows naturally in the Southeast and California.

``It looks lush green,'' said Lena Ma, a soil chemist who led the research at the University of Florida.

``When I take people to my greenhouse to look at a fern with 8,000 parts per million of arsenic, they can't imagine it's toxic waste.''

The brake fern, whose scientific name is Pteris vittata, is the first plant known to accumulate arsenic in extremely high concentrations and still flourish, scientists said.

The discovery is reported in today's issue of the journal Nature.

The Florida researchers were looking for a plant that could take in soil arsenic in high concentrations and then be hauled away. They tested 14 species from an abandoned lumber yard contaminated by arsenic in Archer, near Gainesville.

Their tests showed that the brake ferns growing there concentrated as much as 200 times the arsenic level in the soil. In other tests, the researchers spiked soil with varying levels of arsenic and found that brake ferns absorbed the poison at 10 to 64 times the original concentrations.

Arsenic taints many sources of drinking water in the United States and abroad. People who drink arsenic-contaminated water over long periods are believed to run a higher risk of bladder, lung and skin cancer, as well as other heart and lung ailments.

Some arsenic is naturally present in soil.

It also comes from some farm chemicals, wood preservatives and other industrial products.

Ma said that, unlike many ferns, this one likes the sun.

It potentially could be cultivated in water and act as a natural arsenic filter. And the fern's arsenic-loving genes potentially could be spliced into other plants.

``The fact that it can take something that is toxic at extremely low concentration and accumulate it at high concentrations is very useful,'' said Stephen Ebbs, a plant researcher at Southern Illinois University.

Some plants already are used to remove other pollutants from the environment, a process known as phytoremediation.

But the plants do not concentrate the toxins as strongly as the brake fern.

The report of the fern's special properties comes at a time of intensified worry about arsenic in drinking water.

Last year, a World Health Organization study said that as many as 77 million of Bangladesh's people are at risk of poisoning from naturally occurring arsenic in drinking water.