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MC RESPONSE TO COMMENTSACC SACC COMMENTS: Seabirds may be impacted by MC volatilizingfrom surface waters near points of discharge.This pathway should be analyzed for risk.Based on the Guidance for Ecological Soil Screening Levels(EPA, 2003a, b) document, for terrestrial wildlife, relativeexposures associated with inhalation and dermal exposurepathways are insignificant, even for volatile substances, comparedto direct ingestion and ingestion of food (by approximately 1,000fold). MC is not expected to bioaccumulate in tissues, andconcentrations will not increase from prey to predator in eitheraquatic or terrestrial food webs. EPA has added language to thefinal risk evaluation document in Section 4.1.4 explaining thisrationale.SACC, SACC AND PUBLIC COMMENTS:70, 73 EPA omits consideration of a number of possiblesources of MC exposure. MC is present in air,soil, and sediment and will likely exposeterrestrial and sediment-dwelling organisms. EPAnoted that MC was found in 20% of sedimentsamples in the STORET database (p. 26, ProblemFormulation). The rationale for not consideringexposures to sediment-dwelling organisms isunclear. The risk evaluation states that MC insediment is expected to be in the porewater ratherthan sorbed to the sediment organic matter.However, the log Koc of 1.4 indicates that theconcentration in sediment organic matter will be25 times higher than porewater (withoutconsidering volatilization or sedimentdegradation rates).Additionally, based on its vapor density (2.93 relative to air) andpersistence in the atmosphere (photolysis half-life by OH reaction 79 days), MC vapor may accumulate under specific conditions,but typically will disperse readily into the air. For these reasons,the final risk evaluation does not include further analysis of thispathway for risk, and EPA was able to assess risk based onqualitative analysis.Clarifying language about what pathways are addressed underother statutes has been added to Section 1.4.2 of the RiskEvaluation.Additionally, the STORET data showing detections in 20% ofsamples was summarized by Staples et al., 1985, and quoted byATSDR (https://www.atsdr.cdc.gov/toxprofiles/tp14.pdf). Stapleset al. stated that the median concentration measured in sedimentwas 13 μg/kg, equivalent to 13 ppb, which is more than 2 orders ofmagnitude below the chronic (1,800 ppb) and acute concentrationof concern (COC) (36,000 ppb) values estimated for sedimentinvertebrates by read-across from COCs reported for aquaticinvertebrates.Although the log KOC indicates that MC will partition to sedimentorganic carbon, organic matter typically comprises 25% or less ofsediment composition /pdf/of-2006-Page 10 of 246

MC RESPONSE TO COMMENT54, 73PUBLIC COMMENTS: EPA disregarded pathways of exposure tosediment and terrestrial organisms based onestimated partition coefficients that assume thatchemical equilibrium has been established.However, chemicals of concern can occur in highconcentrations in different environmentalcompartments prior to reaching equilibrium. Abetter approximation approach might be theLevel III Fugacity model, as suggested by theSACC, which predicts that 11% of MC will bedistributed to soil, 44.1% to air, 44.8% to water,and the remainder (0.13%) to sediment, ascalculated using EPI Suite 4.11. An 11%distribution to soil cannot be dismissed as deminimis. Because of its high volatility and use as a solventin many open operations, a large fraction of thetotal amount of MC produced is lost to theatmosphere. Estimates of total emissions are highand MC has been widely found in ambient air.SACC has previously criticized EPA’s failure toinclude all environmental exposure pathways inits determinations of health risk, and the MC1053.pdf) of which approximately 40-60% is organic carbon(Schwarzenbach et al., 2003). Based on these values, thesediment-water Kd (where Kd KOC*fOC) is expected to be equalto or less than 3.8, indicating that at equilibrium, concentrations insediment would be expected to be less than four times higher thanin porewater. However, biodegradation can be expected to be rapidin anaerobic sediments and the porewater also interacts withoverlying surface water from which MC may be lost viavolatilization and/or aerobic biodegradation. Thus, concentrationsin sediment and pore water are expected to be equal to or less thanconcentrations in overlying water. A narrative to this effect hasbeen added to the final risk evaluation (Section 2.1). During problem formulation EPA conducted a screening levelanalysis to consider whether pathways of exposure forsediment and terrestrial organisms should be further analyzedand determined that terrestrial organism exposures to MC wasnot of concern partially based on estimates of soilconcentrations being several orders of magnitude belowconcentrations observed to cause effects in terrestrialorganisms. See prior response for more information on thesediment pathway.EPA did not include the emission pathways to ambient airfrom commercial and industrial stationary sources, becausereleases of methylene chloride from stationary source toambient air are under the jurisdiction of and addressed bySection 112 of the Clean Air Act (CAA). Resulting exposurewere out of scope as described in the problem formulation forMC. Clarifying language about what pathways are addressedunder other statutes has been added to Section 1.4.2 of theRisk Evaluation.Spills/leaks Spills and leaks generally are not included within the scope ofa TSCA risk evaluation. EPA is exercising its authority underPage 11 of 246

MC RESPONSE TO COMMENTevaluation has the same weakness. Thecontribution of air emissions to total should beaccounted for, particularly in areas near emittingfacilities, and should be combined with otherroutes of exposure. Due to its high volatility, MC spills and leakswill likely lead to soil vapor intrusion as apotential exposure pathway. This pathway shouldbe considered but was not addressed in the draftrisk evaluation. In addition to the fact that several million poundsof MC are released annually into the air due to itsvolatility, disposal to water may also create aroute of exposure to organisms living at thewater-atmosphere interface (e.g., aquatic plants,amphibians, and/or shorebirds). These organismsmay be disproportionally impacted by MC. In itsliterature review, EPA dismissed a study that notonly identified a BCF of 577 in water moss(Thiebaud et al., 1994), but also found thatconcentrations at the water-atmosphere interfacemay be more significant than aquaticconcentrations. EPA unjustifiably disregarded Theibaud et al.(1994). According to the Systematic ReviewSupplemental File: Data Quality Evaluation ofEnvironmental Hazard Studies, EPA determinedthe study to be of unacceptable quality, despitegiving it a mean score of 1.5 (defined as “high”quality) because one metric, the outcomeassessment methodology (Metric 17), was ratedas “unacceptable” because, according to thecomments, there was “[n]o adverse outcome.This study analyzed the bioaccumulation/concentration factors of DCM” (p. 64). As such,this metric should have been rated as “notTSCA to tailor the scope of the risk evaluation for MC, ratherthan evaluating activities which are determined not to becircumstances under which MC is intended, known orreasonably foreseen to be manufactured, processed,distributed, used, or disposed of, or environmental exposurepathways addressed by another EPA-administered statute andassociated regulatory program. First, EPA does not identify MC spills or leaks as “conditionsof use.” EPA does not consider MC spills or leaks toconstitute circumstances under which MC is manufactured,processed, distributed, used, or disposed of, within TSCA’sdefinition of “conditions of use.” Congress specifically listeddiscrete, routine chemical lifecycle stages within the statutorydefinition of “conditions of use” and EPA does not believe it isreasonable to interpret “circumstances” under which MC ismanufactured, processed, distributed, used, or disposed of toinclude uncommon and unconfined spills or leaks for purposesof the statutory definition. Further, EPA does not generallyconsider spills and leaks to constitute “disposal” of a chemicalfor purposes of identifying a COU in the conduct of a riskevaluation. In addition, even if spills or leaks of MC could be consideredpart of the listed lifecycle stages of MC, EPA has“determined” that spills and leaks are not circumstances underwhich MC is intended, known or reasonably foreseen to bemanufactured, processed, distributed, used, or disposed of, asprovided by TSCA’s definition of “conditions of use,” andEPA is therefore exercising its discretionary authority toexclude MC spills and leaks from the scope of the MC riskevaluation. The exercise of that authority is informed byEPA’s experience in developing scoping documents and riskevaluations, and on various TSCA provisions indicating theintent for EPA to have some discretion on how best to addressthe demands associated with implementation of the full TSCAPage 12 of 246

MC RESPONSE TO COMMENTapplicable” because the study did not seek todetermine whether there was a hazard outcomeand should rather have been considered a studyof the chemical’s environmental fate andtransport. risk evaluation process. Specifically, since the publication ofthe Risk Evaluation Rule, EPA has gained experience byconducting ten risk evaluations and designating forty chemicalsubstances as low- and high-priority substances. Theseprocesses have required EPA to determine whether the casespecific facts and the reasonably available information justifyidentifying a particular activity as a “condition of use.” Withthe experience EPA has gained, it is better situated to discerncircumstances that are appropriately considered to be outsidethe bounds of “circumstances under which a chemicalsubstance is intended, known, or reasonably foreseen to bemanufactured, processed, distributed in commerce, used, ordisposed of” and to thereby meaningfully limit circumstancessubject to evaluation. Because of the expansive andpotentially boundless impacts that could result from includingspills and leaks as part of the risk evaluation, which couldmake the conduct of the risk evaluation untenable within theapplicable deadlines, spills and leaks are determined not to becircumstances under which MC is intended, known orreasonably foreseen to be manufactured, processed,distributed, used, or disposed of, as provided by TSCA’sdefinition of “conditions of use.”Exercising the discretion to not identify spills and leaks of MCas a COU is consistent with the discretion Congress providedin a variety of provisions to manage the challenges presentedin implementing TSCA risk evaluation. See e.g., TSCAsections 3(4), 3(12), 6(b)(4)(D), 6(b)(4)(F). In particular,TSCA section 6(b)(4)(F)(iv) instructs EPA to factor intoTSCA risk evaluations “the likely duration, intensity,frequency, and number of exposures under the conditions ofuse .,” suggesting that activities for which duration,intensity, frequency, and number of exposures cannot beaccurately predicted or calculated based on reasonablyavailable information, including spills and leaks, were notPage 13 of 246

MC RESPONSE TO COMMENTintended to be the focus of TSCA risk evaluations. And, asnoted in the preamble to the Risk Evaluation Rule, EPAbelieves that Congress intended there to be some reasonablelimitation on TSCA risk evaluations, expressly indicated bythe direction in TSCA section 2(c) to “carry out [TSCA] in areasonable and prudent manner.” For these reasons, EPA is exercising this discretion to notconsider spills and leaks of MC to be COUs. Second, even if MC spills or leaks could be identified asexposures from a COU in some cases, these are generally notforms of exposure that EPA expects to consider in riskevaluation. TSCA section 6(b)(4)(D) requires EPA, indeveloping the scope of a risk evaluation, to identify thehazards, exposures, conditions of use, and potentially exposedor susceptible subpopulations the Agency “expects toconsider” in a risk evaluation. As EPA explained in the“Procedures for Chemical Risk Evaluation Under theAmended Toxic Substances Control Act” (“Risk EvaluationRule”), “EPA may, on a case-by-case basis, exclude certainactivities that EPA has determined to be conditions of use inorder to focus its analytical efforts on those exposures that arelikely to present the greatest concern, and consequently meritan unreasonable risk determination.” 82 FR 33726, 33729(July 20, 2017). In the problem formulation documents for many of the first 10chemicals undergoing risk evaluation, EPA applied the sameauthority and rationale to certain exposure pathways,explaining that “EPA is planning to exercise its discretionunder TSCA 6(b)(4)(D) to focus its analytical efforts onexposures that are likely to present the greatest concern andconsequently merit a risk evaluation under TSCA.” Theapproach discussed in the Risk Evaluation Rule and applied inthe problem formulation documents is informed by thelegislative history of the amended TSCA, which supports thePage 14 of 246

MC RESPONSE TO COMMENTAgency’s exercise of discretion to focus the risk evaluation onareas that raise the greatest potential for risk. See June 7, 2016Cong. Rec., S3519-S3520. In addition to TSCA section 6(b)(4)(D), the Agency also hasdiscretionary authority under the first sentence of TSCAsection 9(b)(1) to “coordinate actions taken under [TSCA]with actions taken under other Federal laws administered inwhole or in part by the Administrator.” TSCA section 9(b)(1)provides EPA authority to coordinate actions with other EPAoffices, including coordination on tailoring the scope of TSCArisk evaluations to focus on areas of greatest concern ratherthan exposure pathways addressed by other EPA-administeredstatutes and regulatory programs, which does not involve a riskdetermination or public interest finding under TSCA section9(b)(2). Following coordination with EPA’s Office of Land andEmergency Management (OLEM), EPA has found thatexposures of methylene chloride from spills and leaks fallunder the jurisdiction of RCRA. See 40 CFR 261.33(d)(defining in part a hazardous waste as “any residue orcontaminated soil, water or other debris resulting from thecleanup of a spill into or on any land or water of anycommercial chemical product or manufacturing chemicalintermediate having the generic name listed [40 CFR 261.33(e)or (f)], or any residue or contaminated soil, water or otherdebris resulting from the cleanup of a spill, into or on any landor water, of any off-specification chemical product andmanufacturing chemical intermediate which, if it metspecifications, would have the generic name listed in [40 CFR261.33(e) or (f)]”); 40 CFR 261.33(f) (listing methylenechloride as hazardous waste no. U080). As a result, EPAbelieves it is both reasonable and prudent to tailor the TSCArisk evaluation for methylene chloride by declining to evaluatepotential exposures from spills and leaks, rather than attemptPage 15 of 246

MC RESPONSE TO COMMENTto evaluate and regulate potential exposures from spills andleaks under TSCA. Thiebaud et al. (1994) was evaluated in the Supplemental File:Data Quality Evaluation of Environmental Fate Studies with a“high” quality rating for its assessment of bioaccumulationpotential. It has been incorporated into the fate narrative(Section 2.1.2). The study remains unacceptable for evaluatingenvironmental hazards; it was incorrectly categorized inenvironmental hazards, as a hazard endpoint was not assessed,so there were no data to evaluate from a hazard perspective.The draft risk evaluation ignores regulation under the Clean Water Act (CWA)68PUBLIC COMMENTS:Communication and coordination between program offices withinEPA occurs regularly on TSCA-related efforts. While EPA has The decision to evalua

of Global Automakers, Inc 61 EPA-HQ-OPPT-2019-0437-0061 Mass Comment Campaign sponsored by Environmental Defense Fund (EDF) 62 EPA-HQ-OPPT-2019-0437-0062 Christina Starr, Environmental Investigation Agency (EIA) 63 EPA-HQ-OPPT-2019-0437-0063 Eric Berg, Deputy Chief, California Division of Occupational Safety and Health (Cal/OSHA)