Routine testing by the Harford County Health Department of local businesses serving food first detected high levels of the gasoline additive methyl tertiary butyl ether (MTBE) at the Exxon in the Fallston area in October 1991, said Herbert M. Meade, chief of the oil-control program for the state Department of the Environment.
The 1991 reading was more than four times the level the state would set, years later, as safe for drinking.
Meade said he required Exxon at the time to test the station’s underground gasoline storage tanks for leaks and to drill monitoring wells to check for ground- water contamination. But 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 the intersection of Routes 152 and 165, near the Baltimore County line.
The pizza shop, the gas station and a Wawa convenience store across the road got water filters to remove the chemical.
But Meade said no broader investigation was done because MTBE levels would wax and wane without apparent explanation. For the next six years, he said, the trouble seemed localized to a few establishments in the immediate neighborhood of the service station, including a dentist’s office.
“The skeptics, the armchair quarterbacks – including myself – would say they were localized because you didn’t go looking,” Meade said yesterday.
This spring, after registering an MTBE level above 300 at a home near the gas station, officials began testing every well they could within a half-mile.
As of earlier this week, the chemical had showed up in 68 of 145 wells tested; eight of those exceeded the state’s 20 parts-per-billion threshold.
A spokeswoman for Exxon Mobil Corp., the corporation that owns the station, said it has no evidence its station is the source of the contamination.
“All the tests would indicate at this point that we have not had a spill or release,” said Patty Delaney, the spokeswoman.
Even so, the company 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 state’s investigation has yet to pinpoint a source or sources, Meade acknowledged, and the station’s tanks appear to be in compliance with all state and federal regulations.
But he added that his agency is convinced that the Exxon station is “a contributor” to the contamination “and is responsible for some level of these MTBEs.” A ground-water sample drawn from beneath the station’s fuel tanks registered 26,000 parts per billion, he said.
Meade said he suspects MTBE vapors somehow bled out of the fuel storage tanks into the ground and tainted the ground water – a theory the ExxonMobil spokeswoman said tests have not supported.
MTBE’s widespread use in gasoline since the late 1970s has made it one of the most common – and troublesome – ground-water contaminants across the nation.
“We’re seeing it more and more every day,” Meade said, noting that he has logged 319 private drinking-water wells across the state that have been tainted with the gas additive.
MTBE also has turned up in about 100 public water systems, though only 13 had worrisome levels.
MTBE, a flammable liquid with a harsh, turpentine-like odor, is added to gasoline to make it burn more cleanly. The U.S. Environmental Protection Agency has required the use of such “oxygenates” in gas since 1990 in areas, including Baltimore, that have unhealthy summer air quality. Federal officials say MTBE has helped to reduce carbon monoxide and ozone air pollution levels nationwide.
Yet the chemical dissolves readily in water and has tainted wells virtually everywhere it has been added to gasoline, causing 17 states to ban or limit its use.
“It has really contaminated ground water in vast areas of the country. … The shame of it is this was done for an environmental benefit,” said Thomas A. Burke, professor of health policy and management at the Johns Hopkins University Bloomberg School of Public Health.
It is unclear what, if any, health threat MTBE poses when ingested at the levels detected in most ground-water samples. EPA considers it a potential cause of cancer in humans.
Rats and mice developed cancer after breathing high doses of MTBE fumes, and some developed kidney and liver problems, among others, according to the federal Agency for Toxic Substances and Disease Registry.
Evidence of human health effects is lacking, though some people who inhaled MTBE fumes while pumping fuel or working at gas stations reported headaches, nausea, dizziness and nose or throat irritation.
Maryland has set 20 parts per billion as a threshold for regulatory action, chiefly because MTBE’s odor can be tasted or smelled at such a low level, rendering the water unpalatable.
While finding low levels of MTBE in a well might not be a definite health hazard by itself, it probably indicates the presence nearby of gasoline in ground water, and other chemicals in gas are known to be harmful, said Edward Bouwer, professor of environmental engineering at Johns Hopkins University. Benzene, for instance, is a known human carcinogen.
While other causes of gasoline getting into the ground water are possible, such as fuel spills or auto accidents, Bouwer said of service stations, “All you need to do is leak a gallon a day for years and really screw up ground water, but you can’t detect a gallon a day.”
<!– CUTLINE TEXTTesting at a Fallston Exxon station has not revealed any fuel leaks.
CUTLINE TEXT–> <!– ART CREDITDOUG KAPUSTIN : SUN STAFF PHOTOS
ART CREDIT–> <!– CUTLINE TEXTResidents around Upper Crossroads in Harford County are concerned about high levels of a gasoline additive found in some wells. Paula Goodwin is hesitant even to wash dishes in the water from her contaminated well.
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