MTBE Groundwater Impact:
Detection Reports Appear to be Exaggerated, Diminishing
The clean-burning gasoline additive Methyl Tertiary-Butyl Ether (MTBE) was discovered at low levels in groundwater sources in California, notably in Santa Monica (1996) and Lake Tahoe (1997). Since then, MTBE has also been detected at low concentrations in other parts of the country. Invariably, the presence of MTBE in groundwater has been directly linked to underground storage tanks (USTs) leaking gasoline for an extended period of time even years in some instances. These leaks are typically due to inadequate or non-existent UST inspection and/or maintenance practices. Nonetheless, early investigations of the extent of MTBEs perceived groundwater impact, including reports by the University of California and EPAs Blue Ribbon Panel on Oxygenates, largely portrayed the reported MTBE detections as potentially significant. Policy makers, the press and the public were led to believe that future increased contamination rates would threaten the nations drinking water supplies.
These reports largely ignored the fact that the root cause of the problem was leaking gasoline containment systems. They attached a stigma to MTBE that led some state legislators and water quality officials to call for the removal or phase-out of MTBE from gasoline. Others cautioned against a rush to judgment on MTBE, arguing that removing MTBE from gasoline will not solve the gasoline contamination problem, that clean air should not be sacrificed to correct improper gasoline storage and handling practices, and that the nations gasoline supply would be adversely impacted through precipitous action on MTBE.
MTBE is more water soluble and can be transported faster and farther in soil and water than other gasoline constituents. MTBE is also easier to smell and detect in water, even at very low concentrations. As a result, it has become a convenient scapegoat for a larger problem leaking gasoline containment systems. MTBE has rarely, however, been detected in groundwater at levels deemed unsafe by the U.S. EPA. The vast majority of MTBE detections have been at concentrations below five parts per billion (ppb) far below the EPA Consumer Advisory for MTBE that sets a suggested standard for prolonged exposure of 20 to 40 ppb to avoid unpleasant taste and odor. EPA is currently developing a secondary standard for MTBE to incorporate additional taste and odor considerations for the publics acceptance of traces of the chemical in groundwater.
In testimony before the U.S. Senate, Dr. Daniel Greenbaum of the Health Effects Institute, said that reports of MTBE water contamination in California have been overblown. According to Greenbaum, the results of [water sampling] confirm that MTBE is detected in a relatively small number of water sources of those tested, and of those where it is detected, relatively few have levels above existing or proposed levels of concern." Several states have confirmed that MTBE does not pose a threat to public health or water sources. For instance, the New Jersey Department of Environmental Protection reported that data from 400 of the states public community drinking water supplies found no instance where MTBE approached New Jerseys drinking water standard for MTBE. The New Jersey report noted that, "MTBE contamination is not currently a public health concern in New Jersey public drinking water supplies."
As of March 2001, the California Department of Health Services reported that MTBE has been detected in only 0.8 percent of all water sources sampled, with only 0.2 percent of those samples exceeding Californias primary health standard for MTBE. In addition, a report by the engineering consulting firm, Exponent, Inc., concluded that, Despite the negative publicity surrounding MTBE and potential aesthetic issues, MTBE in drinking water should not pose a significant public health hazard in California
Today, it appears that ongoing UST upgrade initiatives have helped control releases of gasoline into the environment as both the frequency and magnitude of reported MTBE detections appear to be declining. The alleged threat to the nations groundwater supplies has never materialized, if it ever truly existed in the first place. The opportunity exists now to more accurately assess any perceived future impact posed by MTBEs continued use in gasoline against its confirmed energy security and air quality benefits.