Tests have found 68 wells near a Fallston Exxon station to be contaminated with the gasoline additive methyl tertiary butyl ether (MTBE). Eight of them contain levels of MTBE above what the state considers safe. State environmental officials say it might be the worst well contamination in state history.
"I need some answers ... as to why we continue filling the underground tanks with gasoline if the vapor from it is materializing and getting into our ground water," Parrott said.
Exxon officials have said there is no evidence that the service station is the source of the contamination, although officials from the Maryland Department of the Environment have theorized that vapors from the station are a culprit. The highest levels of contamination have been found under the station.
Environmental activists said service stations have been the source of MTBE contamination in many states.
"It's important for people to know that this is happening all over the country, and it's important to make the responsible parties pay," said Brad Heavner, state director for the Maryland Public Interest Research Group.
"It's outrageous," Heavner said of Exxon's role in the Harford case. "They apparently contaminated the water, and they need to clean it up."
Parrott said the company Exxon hired to test the wells should test outside the half-mile radius being examined. State Sen. J. Robert Hooper, a Republican who also represents the area, agreed.
"As they develop the plume, we'll mostly likely have to expand the testing," Hooper said. "If we need to go further, then [Exxon] needs to do that because, obviously, something's not right."
Hooper said he does not think the station should have to close until someone determines a more specific cause of the contamination. He and Parrott both promised to urge state and local officials to pressure Exxon until the problem is solved.
A spokeswoman for Harford County Executive James M. Harkins deflected questions about the wells to county Health Department officials, who said they are playing a supporting role to the Maryland Department of the Environment in following the testing.
Richard McIntire, a spokesman for the MDE, said Exxon and state officials have not ruled out testing in a wider area and plan to conduct sample tests on houses just outside the half-mile radius. He said the test area is larger than those in many similar cases.
Exxon has supplied bottled water to everyone within a half-mile of the station and paid to install water-filtration systems on 20 homes and businesses.
The potentially cancer-causing chemical has been recorded on and off in wells near Fallston for 13 years.
Parrott said she was "very dismayed" that state officials and representatives from the county Health Department had failed to tell Fallston residents of the problem sooner.
Routine testing by the Health Department detected high levels of MTBE at the Exxon station in the Fallston area in October 1991, according to the MDE. The 1991 reading was more than four times the level the state would set, years later, as safe for drinking.
State officials have said they required Exxon to test the station's underground storage tanks for leaks and to drill monitoring wells to check for ground-water contamination. The investigation was closed after no leaks were found and the MTBE levels dropped.
The problem resurfaced in 1998, when health inspectors detected MTBE in water from a pizza shop behind the service station at Routes 152 and 165, near the Baltimore County line.
This spring, state officials recorded a high MTBE level at a home near the gas station and began testing every well they could within a half-mile. As of this week, 68 of 145 wells had tested positive and eight of those exceeded the state's 20 parts-per-billion threshold.
McIntire said those figures had not changed as of yesterday and that he hopes all wells within the half-mile radius will be tested by the end of this week.
MTBE, a flammable liquid that smells like turpentine, has been added to gasoline since the 1970s to make it burn more cleanly. The EPA has required the use of such oxygenates in gasoline since 1990 in areas, including Baltimore, that have unhealthy summer air quality.
The chemical is highly soluble and is known to travel quickly through ground water. As a result, 17 states have banned or restricted its use. In Santa Monica, Calif., Exxon Mobil and another large oil company agreed to pay for a $200 million treatment plant and $30 million in damages after MTBE contaminated the city water system.
It is unclear what health threat MTBE poses, although the EPA considers it a possible cause of cancer in humans. Rats and mice developed cancer after breathing high doses of MTBE fumes, and some developed kidney, liver and other problems, according to the federal Agency for Toxic Substances and Disease Registry.
Experts say that if MTBE is detected, homeowners should try to find out from local or state governments whether they are in the path of a "plume" of contaminated ground water and what is being done to control or reduce the contamination. They say potentially affected homeowners should install filters on their water systems.