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wATE:R. GREMLIN. PUBLIC -HEALTH ASSESSMENT: PUBLIC COMMENT DRAFT about five days (U:5. EPA, 2010.). t-DCE is not expected to settle on soil or surface water and would evaporate back into the air quickly. What Happens to t-DCE in the Body7 t-DCE is :a volatile, fat-soluble compound that is quickly taken: up through the lungs and gastrointestinal tract (ATSDR, 1996). While it is fat-soluble,.there is no solid data indicating accumulation in the liver, brain;. kidney, or other fat tissue.following exposure.:t-DCE.can be metabolized in the liver, as shown: by rodent studies. It is likely broken down into more water-soluble metabolites which are quickly removed by the kidneys (ATSDR, 1996; U:S..EPA; 2010). Some. studies show the body can eliminate t-DCE. by exhaling it (U.S. EPA, 2010). M D H Risk.Assessment Advice —January 2019 In January 2019; M.P(A requested that IVII)H develop a.site-specific air guidance. value that could be: used to determine a safe amount of t-DCE that Water Gremlin. could release into(the air. MDH derived a chronic inhalation value. of 70 µg/m3 (micrograms per cubic meter) as. Risk Assessment Advice (RAA), or an amount that is safe to breathe daily for up to a lifetime. The RAA was developed to be protective for immune system effects observed in mice exposed to t-DCE in drinking water. However, exposums.to t= DCE in amounts greater t.han70 µg/m3 does not me.a.n health effects are likely, especially if they only occur episodically and for less-than�Iifetime durations. As a general rule, the risk ofhealth.effects increases as the amount and duration of chemical exposures increase. MDH's RAA was unable to takeinto account the minor constituents of FluoSoly WS, hydrofluoroethers, because toxicological data are unavailable for them. Hydrofluoroethers are very persiste.rit.cheaticaIs that are added to make the FluoSoly mixture non-flammable. t-DCE Toxicology Studies and Risk. Assessment As noted earlier, risk assessment is a science -based tool used to evaluate the potential effects of a chemical -on human health. The paragraphs below describe the available t-DCE. toxicology studies and how air guidance values are developed. by dlfferentagencies from those studies. The U.S. EPA.comp.leted a review of t-DCE. in 2010 (U.S. EPA, 20.10). EPA describes -that a general overview of the. toxicity studies conducted indicates t-DCE displays "low toxicity." However, a lack of Information regarding the possible health effects from breath ing.t-DCE over long. periiods. is also noted. EPA concluded that there was insufficient Inhalation data to support deriving a safe air value for long- term (chronic) exposures. EPA.also states that there is."inadequate information to`assess the carcinogenic potential" of t=DCE based on the absence of .human or animaI cancer studies. Although there are no chronicstudies of t-DCE,.`several sub.chronic animal studies exist. Five studies' exposed rodents to t-DCE by .drinking water.orfood, and two exposed rodents by inhalation.(one. unpublished). Changes. in liver and kidney weight were the.main effects observed .(U.S EPA,:2010), The results of the two inhalation studies were inconsiste.nt,.A limitation to both was that exposures occurred. .intermittently (six and eight: hours/day) rather than continuously. With intermittent dosing,. exposure concentrations.should be adjusted to reflect a continuous expos ure%to use for calculating health risk values. The earliest study (Fruen.dtet al., 197!).showed an effect of fat accumulation in the liver and liver cells in rodents exposed to t-DCE at 794,000 µg/m3 [equivalent to 2a0 partsper m11.11!on (ppm)]. The Agency for Toxic Substances and Disease Registry (AMR) used this st.udy's results to develop acute and subchronic air values of 790 µg/m3 (dividing the effect level.noted above by an 15