Sewage sludge is prized by many gardeners and farmers as a rich fertilizer. But environmental groups have long questioned the safety of the material, which may contain dangerous chemicals such as dioxin.

The panel, led by Thomas Burke of Johns Hopkins University's department of health policy, urged the EPA to assess the health risks of sewage sludge for those who come into contact with it or live near treated land.

"There is a serious lack of health-related information about populations exposed to treated sewage sludge," Burke said. "To ensure public health protection, the EPA should investigate allegations of adverse health effects and update the science behind its chemical and pathogen standards."

For example, chemicals in sewage sludge may be absorbed by vegetables or affect water quality, the report said.

Ellen Harrison, a Cornell University researcher and member of the National Academy panel, said she was most concerned about residents living near farms or reclaimed mines, where huge amounts of sewage sludge are used. The wind can blow particles into homes and heavy rain can wash the material into groundwater, she said.

Cornell University's Waste Management Institute has collected the claims of nearly 250 people clustered in areas of California, Florida, New Hampshire, Pennsylvania and Virginia who blamed sewage sludge for illness. Their symptoms included headaches, open sores, nose bleeds and breathing problems.

Three deaths have been blamed by families on the sludge.

EPA REVIEWING STANDARDS

The EPA said that the panel could not find any documented scientific evidence that federal sludge standards did not protect the public.

Still, Ben Grumbles, deputy assistant director of EPA's water office, admitted there were "gaps" in the science behind the agency's sludge standards and that the EPA was reviewing them.

"The (sludge) program could benefit from updating and strengthening the scientific underpinnings," he said.

Cornell's Harrison said she was convinced that many of the illnesses in the university's database are due to the thick layers of sludge applied to farmland or to reclaim mines.

"In my personal opinion, I am convinced that some of the situations in which people are getting sick are linked to sewage sludge," she said in an interview.

"There have been no scientific investigations or documentation of health impacts by the EPA. But the lack of information doesn't mean there is a lack of health impacts," she added.

About 5.6 million tons of sewage sludge is generated annually in the United States. More than half of it is applied to land, and the rest is buried in landfills or burned.

The agency developed sewage sludge standards in 1993 that included limits on arsenic, cadmium, chromium, copper, lead, mercury, molybdenum, nickel, selenium and zinc.

However, other chemicals also occur in sewage sludge. Those include foaming agents in laundry detergents, flame retardants used in furniture and chemical fragrances from shampoos.

Under EPA rules, sewage sludge must be treated at wastewater plants to destroy illness-causing bacteria such as salmonella and campylobacter. However, the panel said the agency's decade-old rules do not cover emerging pathogens such as E. coli 0157:H7 and listeria. Both can be deadly to small children, pregnant women or people with chronic illnesses.

Two years ago, the U.S. Agriculture Department dropped a plan to allow sewage sludge in growing organic-certified fruits and vegetables after an outpouring of criticism.