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M[NUTES October 21, 199 6 4 BOARD OF HEALTH <br /> Mr: Gi trelis, resident of the Sampson's MB Road area, questioned fir. <br /> Trowbridge, "How do we know there are not several other T.C.E. plumes several miles <br /> down the road-.13 <br /> Mr-. Trowbridge responded, "we can only base our estimates on what"s been <br /> ava able." "There is not much sampling data upstream at all." '`It's our understanding <br /> there was a release of T.C.E. in 1993."" "what we have been looking at is what people i <br /> the community might have been exposed to and how long.,' `'we felt that the <br /> environmental sampling data from the aquifer was better and that's what we ended up <br /> using." `Using this approach we estimated that computer time and opportune exposure to <br /> T.C.E. on those two houses fell within a range of three months to twelve months whereas, <br /> the exposure to ,P.C.E., the exposure duration Fells within a range from three to seven <br /> ears.' "These duration estimates are based on the amount of time that people were living <br /> at residences because the southern extent of the P.C.E. plume has not been determined we <br /> really were no able to work backwards." "when we look at the southern most port <br /> where P.C.E. was detected you can backtrack to where it looked like it would have passed <br /> expected ells in about 1992." "But, we don't know that that"s the southern most point <br /> so we haven"t made that statement we would rather have used the conservative <br /> a roach.' ane'of the questions is hether P.C.E. and T.C.E. come xom the same <br /> thing." "The answer is no." <br /> l r; Giatrahs questioned, "what about in the work place?" <br /> 1r. Trowbridge responded, "They are both industrial solvents." "P.C. . is- the- <br /> most commonly used in dry cleaning." "T.C.E, is most often used as a degreaser." <br /> "P.C.E. will degrade to T.C.E. but not visa versa." `Now we start looking at the levels of <br /> exposure." "What concentrations are we talking about." "&NAat we are looking at is not <br /> just, data from the private wells but also from the monitoring wells to evaluate what we- <br /> thought to be a fall range of possible exposures."' "That would include work case <br /> estimates." `The area where P.C.E. concentrations are elevated is quite small compared <br /> to the entire length of the plume." "So for us say someone was exposed for seven gears to <br /> that mammum concentration really is not accurately representing a true expo sure."' "In <br /> doing this we also look at the developments within the plume."' "Were they on the edge of <br /> the plume where concentrations tend to be lower, were they right in middle of the plume <br /> or were they upstream or downstream ofthe highest P.C.E. concentrations. If we <br /> compare the levels of these exposures to the toxicological information our best opmron is <br /> that the averse health affects are not expected from these exposures at either of these <br /> 9� <br /> house . "The most sensitive endpoint to T.C.E. exposure <br /> is developmental effects. <br /> `The most sensitive endpoint to P.C.E. is neurotoxiclogical effects. "Preparing the <br /> relative exposure that we saw in this case at hese two horses, ghat was known from <br />