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WATER GREMLI-N PUBLIC.HEA.LTH ASOES'SMENT'' PUBLIC. COMMENT DRAFT <br />Table 3; t-DCEA►r Monitoring Results. on the Water Gtemlln Property <br />.:.,.... -... <br />............ <br />East <br /><0.6� <br />52.4 <br />3..4� <br />8.3 <br />North <br /><0.6 <br />93.2 <br />1.8 <br />11.1 <br />Northwest Y <br />_ <0.6 <br />108 <br />1.3 <br />7.9 <br />South <br />-West,__�� _ <br />-0.6` <br />50.5 <br />172._ <br />1:4 <br />1.5 <br />6.8 <br />14.4 <br />When the.mQnitors did notdetect any t DCE, MDH used the detection limit (rather than zero) when calculating the <br />median and average results. This results in median and average values that are biased high (overestimations). <br />MPCA installed additional VOC monitors at Birch Lake Elementary School (north of Water Gremlin) and <br />Columbia Park (northeast of Water Gremlin) to provide off -site air monitoring resuits*8t locations used <br />by the community. These locations.-qre shown on the map in Appendix A. Two 24-hour samples were. <br />collected at these monitors in August 2019*15efore.the t-DCE coating line shut down on August 22,.2019 <br />(Table 4). <br />Table 4: t-DCEAir Monitoring Resultsat Birch Lake Elementary and Columbia Park <br />Prior to -Shut DoWn of Coating Lines.(ug/m3) <br />Sampling continued through the end of November 2019, during the shut -down period, and yielded all <br />nondetect.results. Sampling began again on April*$,2020 and continued -through August;31, 2010 (Table <br />5). The major ty of the results. were nondetect (<2.µg/m3) and the-mediahand:aVerage values' him. <br />overestimations (see Table 5 footnote). <br />Table.5., t-D:CE Air Monitoring Results at Birch take elementary <br />M'pnitorlacation' Minimv_�rn Maximum Median,* l Average_ <br />Birch Lake.Oementary 0.24 9.1 1 2 y2.9 <br />Columbia Park _ I 0.04. Y 17 2.8 <br />*Whenthe monitors did not detect any t-OCE, MDH used the. detection limit (rather than zero) when calculating the <br />median and average: results. This results in median and average values that are biased high (overestimations). <br />MDH Risk Assessment Advice —April 2020 <br />In 2Q20;.MDH conducted a re-evaluation of t-DCE toxicity studies that tould be used to develop.an air <br />guidance Value, because an improvement In -the modeling of the study data used16 dei:liie the 2019 RAA <br />was discovered (California EPA, 2018). MDH, in consultation with the U.S: EPA, decided to use the <br />improved study model data and updated. its chronic inhalation RAA*fort-DCEto 20 µg%m3. MDH also <br />developed o-subchron'ic inhalation value for t-DCE of 200 µgjm3. A subcheonicduration is defined as a <br />repeated exposure for greater than.30 days .an-d up to 109/6 of an. average human lifespan (eight years). <br />( <br />18 <br />