ADAMSTOWN — The amount of fluoride in the water moving underground off Alcoa Eastalco Works’ property and onto William Renn’s farm in the 5500 block of Mountville Road may contain concentrations of fluoride in excess of what would be safe to drink, environmental and health experts at Johns Hopkins University said.

Right near the property line, a fluoride test on Eastalco’s land was about 100 percent more than what it should be for public consumption, according to a report done by MFG Inc. in 2005. MFG Inc. is an environmental consulting company hired by Eastalco to monitor fluoride.

The contaminated water plume appears to be heading off-site and east of Tuscarora Creek, toward residential properties that are on public water, said Ralph Lightner, an environmental consultant for Johns Hopkins University who reviewed MFG’s report. Mr. Lightner has a Ph.D. in nuclear engineering and has extensive experience in hazardous waste removal.

Even though the contaminated plume is headed toward an area served by public water, which is treated, those in the path of the plume who use well water might want to consider having their drinking wells tested periodically until fluoride in the groundwater is shown to be safe for drinking, Mr. Lightner said.

The maximum safe level for fluoride in drinking water is 4 milligrams per liter, according to the U.S. Environmental Protection Agency. In excess of that, people in general may be susceptible to bone disease, pain and tenderness of the bones.

The fluoride test at the southern tip of Eastalco’s property was 7.8 mg/L in October 2005, according to data in MFG’s report.

A test on Mr. Renn’s farm, just south of Eastalco’s property, contained 0.26 mg/L of fluoride in 2005, well within safety limits, according to MFG’s report. That test was slightly south of the projected path of the plume, which is confined to Mr. Renn’s farm, which has public water, according to county land records.

Outside the path of the plume, to its south and west, are about three dozen private homes and one business. Some of those residents said they wanted to have their wells checked as a precaution.

“I will probably just go ahead and have it done,” said Hope Green, the daughter of a couple who live on a farm directly south of Mr. Renn’s property.

Joyce Marsh, whose home is one of a couple dozen in a subdivision off Mountville Road, said she would like to be sure the fluoride in water from her drinking well is within EPA’s guidelines.

Mr. Lightner doesn’t expect the contamination will get worse over time, as long as the source of has been removed. Eastalco shut down most of its operations in December 2005, keeping just a skeleton crew since then.

“As the contamination spreads over a greater area, it will be diluted,” Mr. Lightner said.

Oscar Fisher, Eastalco’s environmental superintendent, said Alcoa found the source and removed it. While cleaning out a pond in 2004, Eastalco workers noticed a potential problem that led to the discovery that fluoride may be leaking through the pond’s lining, he said. The pond was used to keep contaminated materials prior to hauling them to an industrial waste landfill.

Eastalco stopped using its north holding pond in 2005 and discontinued use of its south pond in July 2006, he said.

Eastalco has been monitoring its grounds since the aluminum company was founded in Adamstown in the late ’60s. Processing aluminum requires many different kinds of chemicals that must be contained and stored to keep people safe.

Removing the source of the problem won’t get rid of the fluoride that has already seeped into the groundwater, and Eastalco is closely monitoring its property to ensure contamination continues to decline, Mr. Fisher said.

MFG estimated it would take four to eight years for the fluoride to become diluted enough to be within the public health standard for safe drinking water, Mr. Fisher said.

Robyn Gilden, a public health nurse and outreach program manager for the Center for Hazardous Substances in Urban Environments at University of Maryland Baltimore School of Nursing said the contamination at Eastalco would be a public health concern only if people drink in excess of two liters a day for many years, she said, according to the federal guidelines established by EPA.

In small amounts, fluoride has beneficial health effects, according to the EPA. Drinking water normally contains between .7 and 1.2 mg/L of fluoride.