"Right now we are working with the Department of Environmental Protection to locate the source of the chemical," she said.

The state drinking water standard for EDB is 0.05 parts per billion, but the level found in the university's supply was 0.13 parts per billion.

The source of the EDB is presently unknown, and Ruskin said many possibilities exist to explain how the substance found its way into the water supply.

"It is probably related to gasoline, because that makes up most of its usage, but there is a wide range of human activities that use gas," he said, including driving automobiles, gas leaks and spills.

Rick Schuhmann, instructor of environmental engineering, said EDB has also been used as a soil fumigant or insecticide.

Ruskin said this was the first time EDB was detected in any of the university's drinking water sources, and it has not been detected again since then.

"We confirmed it was there Oct. 17, but subsequent testing in an Oct. 28 re-sampling could not detect any," he said. "We are confident that Penn State's water is safe to drink."

Fong said the university's water supply is tested every three months for EDB, in accordance with state and federal guidelines.

She said the university's drinking water, which supplies all buildings on campus, comes from several wells in a nearby well field called Big Hollow, beyond the area where the Penn State Blue Band practices. Currently, six of the wells are in use.

Ruskin said the multi-well system provides greater protection from health risks. If the water in one well is contaminated, it mixes with the water from the other wells and is diluted before reaching humans.

"Even with an elevated level [of EDB], by the time the water gets to the tap it has an even lower concentration of the chemical," he said.

He said it takes many years of EDB exposure to cause health problems.

"This was a single instance; it was detected once in one well," he said. "This is not long-term exposure, so the risk is minimal."

But Schuhmann said even small amounts of EDB pose a significant health risk.

"It is a very potent chemical with a very high toxicity," he said. "It is classified as a probable human carcinogen, meaning that it has induced tumors in rats and mice, but they have no worker studies because they can't test on humans."

He said short-term effects include reproductive problems, such as changes in sexual behavior for females and lowered sperm count and sterility for males.

Margaret Spear, director of University Health Services, said they have not seen any cases of illness due to EDB exposure or a contaminated water supply.

"There has been nothing we have seen that suggests that at all," she said.

Penn State's drinking water has been contaminated before. Dangerously high levels of a carcinogenic dry-cleaning solvent called perchloroethylene was found in the university's water supply in 1998. The university shut down two affected wells and transferred a third to golf course irrigation.