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10/12/1995 28.44 9153519357 ANNE M FARR PAGE 07 We have so far identified about 30 other sites in Maine where MTBE is a component of the spilled gasoline. This accounts for about 90% of the recent analyses which we have routed through the Public Health Lab. They all seem to follow the same general pattern that: 1)concentrations of gasoline and MTBE in ground water at the center of the plume can be extrememely high. Our record high concentration so far is over 600,000 parts per billion to one household well with the intake pipe beneath floating product in a sand and gravel aquifer. This contrasts with the usual maximum concentration for similar situations without MTBE of about 10-30.000 pans per billion. 2) MTBE can occur as the only contaminant above detection limit over large areas of the plume. In one plume, believed to have originated from a small driveway spill. MTBE was the only detected contaminant of the spill. 3) the MTBE plume seems to occur as a halo around the gasoline-plus-MTBE plume Where the plume is expanding. detection of MTBE precedes detection of gasoline in contaminated wells. Toxicity of MTBE The American Petroleum Institute. and several MTBEproducers have run a battery of toxicity tests to assess its hazards. A summary of the results of these tests is as follows. Within the limits of the testing. MTBE was found to be not very toxic, with effects similar to those which are characteristic of other ether compounds such as diethyl ether, formerly the standard surgical anaesthetic. It appears not to be genotoxic,and because it was "negative with and without activation"on the Ames test. it is probaby not carcinogenic. MTBE is,however, a skin and eye irritant in more than one rodent species at high doses. ARCas health monitoring of thea workers at MTBE manufacturing and transport facilities s seem to indicate no adverse effects at time weighted average doses of up to 3ppm in air But as is commonplace with any ground water contaminant getting into household water supplies, the concern it raises and the aggravation it causes the affected householders is a serious health effect independent of its toxicity. Four reasons for concern over the toxicity of MTBE, and its presence in domestic well water are the following. 1) It is very mobile in ground water. Thus concentrations recorded from a well one week may be quite different the following week Occassionally we have noted increases in the concentration of MTBE in domestic supplies of about an order of magnitude within a couple of days. Thus it is important to reduce concentrations in domestic water supplies as soon as they are discovered. 2) plumes of MTBE in ground water are associated with plumes of gasoline, with its more varied and toxic components. Thus detection of MTBE should be considered a warning bell 3)There is concern over MTBE's irritant pr+apetties. i 4) MTBE is probably a nervous system depressant (like other ethers and the BTX components of gasoline)at high concentrations. With these considerations in mind,the State Toxicologist for Maine has set a recommended maximum concentration level for MTBE in domestic water at 50.parts per billion. the same as for gasoline. 3�i t f