MassDEP BWSC Regulatory Reform Initiatives



SUMMARY OF RECOMMENDED REVISIONS BASED ON IRIS and AAL Toxicity Value Updates REVIEW DRAFT Updated May, 2012Proposed toxicity value updates for MCP Standards based on revisions of EPA’s Integrated Risk Information System (IRIS) are summarized on pages 1-8. For completeness, the table for each chemical shows all recommended toxicity values in the last column. Those based on IRIS revisions are shown in bold typeface. Page 9 summarizes inhalation toxicity value revisions to be consistent with recently revised Massachusetts Ambient Air Limits (AALs) and Threshold Effects Limits (TELs). The AALs and TELs are used by the Bureau of Waste Prevention for evaluating air emissions from different types of facilities. ORS is in the process of updating these values. The updated methodology for developing AALs, including the methodology for selecting toxicity values, is available at . The toxicity values that have been incorporated into revised AALs are given primary consideration when identifying inhalation toxicity values for use in developing Method 1 Standards. Atachments A and B summarize the perchlorate RfD and the 1,4-dioxane Drinking Water Guideline updates respectively. Carbon Tetrachloride Toxicity Value2008 MCP Toxicity Value2008 MCPTox ValueReferenceIRIS ValuePublished March 2010Value Recommended by DEP in 2012 Chronic Oral RfD7 x 10-4 mg/(kg-day)14 x 10-3 mg/(kg-day)4 x 10-3 mg/(kg-day)Subchronic Oral RfD7 x 10-3 mg/(kg-day)2dNot provided1 x 10-2 mg/(kg-day) (a)Chronic Inhalation RfC4.3 x 10-1 mg/m331 x 10-1 mg/m31 x 10-1 mg/m3Subchronic RfC4.3 x 10-1 mg/m340Not provided1 x 10-1 mg/m3 (b)Oral Cancer Slope Factor1.3 x 10-1 per mg/(kg-day)17 x 10-2 per mg/(kg-day)7 x 10-2 per mg/(kg-day Inhalation Unit Risk Factor1.5 x 10-5 per ?g/m316 x 10-6 per ?g/m36 x 10-6 per ?g/m3References for Method 1 Standards1 U.S. EPA, Integrated Risk Information System (IRIS). On-line search current as of January 10, 2007.2d Withdrawn from HEAST3 CHEM/AAL [NOTE: The 1995 AAL is 0.07. The value of 4.3 is the AAL with the source contribution factor removed.]40 The Subchronic Inhalation Reference Concentration is taken to be equal to the chronic value, absent clear chemical-specific information justifying a higher value.Notes for carbon tetrachloride Table 1 – revisions recommended for 2012The recommended subchronic toxicity value is set at the subchronic value from which the chronic RfD is derived. (The IRIS chronic RfD for carbon tetrachloride incorporates an uncertainty factor of 100.5 for subchronic-to-chronic extrapolation.) The subchronic value is set equal to the chronic value. The chronic toxicity value is based on a chronic study. The available information does not provide guidance for extrapolation to a subchronic value.Cyanide Toxicity Value2008 MCP Toxicity Value2008 MCPTox ValueReferenceIRIS ValuePublished Sept. 2010 Value Recommended by DEP in 2012 Chronic Oral RfD1 x 10-2 mg/(kg-day)4a6 x 10-4 mg/(kg-day)6 x 10-4 mg/(kg-day)Subchronic Oral RfD1 x 10-2 mg/(kg-day)4aNot provided6 x 10-3 mg/(kg-day (a)Chronic Inhalation RfC7 x 10-3 mg/m348 x 10-4 mg/m38 x 10-4 mg/m3Subchronic RfC7 x 10-3 mg/m340Not provided3 x 10-3 mg/m3 (a)Oral Cancer Slope FactorNANANon-carcinogenInhalation Unit Risk FactorNANANon-carcinogenReferences for 2008 MCP Toxicity Values for Cyanide:4a This one-time allowable intake was developed by DEP staff. See files on-line at Developed for the Risk Assessment ShortForm-Residential Scenario (MADEP 1992) by MADEP staff.40 The Subchronic Inhalation Reference Concentration is taken to be equal to the chronic value, absent clear chemical-specific information justifying a higher value.Notes for 2012 Recommended Values The recommended subchronic toxicity value is set at the subchronic value from which the chronic value is derived. (The IRIS chronic RfD for cyanide incorporates an uncertainty factor 10 for subchronic-to-chronic extrapolation. The IRIS chronic RfC incorporates an uncertainty factor of 100.5 for subchronic-to-chronic extrapolation) Dichloromethane Toxicity Value2008 MCPToxicity Value DEP Method 1ReferenceIRIS ValuePublished November 2011Value Recommended by DEP in 2012 Chronic Oral RfD6 x 10-2 mg/kg-day16x10-3 mg/(kg-day)6 x 10-3 mg/(kg-day)Subchronic Oral RfD6 x 10-2 mg/kg-day2Not provided6 x 10-3 mg/(kg-day) (a)Chronic Inhalation RfC3 mg/m320.6 mg/m36 x 10-1 mg/m3Subchronic RfC3 mg/m340Not provided 6 x 10-1 mg/m3 (a)Oral Cancer Slope Factor7.5 x 10-3 per mg/(kg-day)12 x 10-3 permg/(kg-day)2 x 10-3 permg/(kg-day)Inhalation Unit Risk Factor4.7 x 10-7 per ?g/m311 x 10-8 per ?g/m31 x 10-8 per ?g/m3References for 2008 MCP Method 1 Standards for Dichloromethane1 IRIS2 HEAST40 The Subchronic Inhalation Reference Concentration is taken to be equal to the chronic value, absent clear chemical-specific information justifying a higher value.Notes for Recommendations Based on IRIS ValuesThe subchronic value is set equal to the chronic value. The chronic toxicity value is based on a chronic study. The available information does not provide guidance for extrapolating to a subchronic value.Cis-1,2-Dichloroethylene Toxicity Value2008 MCPToxicity Value 2008 MCPTox. ValueReferenceIRIS ValuePublished September 2010Value Recommended by DEP in 2012 Chronic Oral RfD1 x 10-2 mg/kg-day22 x 10-3 mg/(kg-day)2 x 10-3 mg/(kg-day)Subchronic Oral RfD1 x 10-1 mg/kg-day2Not provided2 x 10-2 mg/(kg-day) (a)(b)Chronic Inhalation RfC3.5 x 10-2 mg/m339Not provided6 x 10-3 (c)(d)Subchronic RfC3.5 x 10-2 mg/m340Not provided6 x 10-2 mg/m3 (c)(d)Oral Cancer Slope FactorNANANon-carcinogenInhalation Unit Risk FactorNANANon-carcinogenReferences for 2007 MCP Toxicity Values2 HEAST39 Conversion of the oral Reference Dose to a Reference Concentration, using the equation:RfC = RfD x BW/Ventilation RateRfC = RfD x 70 kg/(20 m3/day)40 The Subchronic Inhalation Reference Concentration is taken to be equal to the chronic value, absent clear chemical-specific information justifying a higher value.Notes for Recommended Cis-1,2-Dichloroethylene Values: The recommended subchronic toxicity value is set at the subchronic value from which the chronic value is derived. (The IRIS chronic RfD for cis-1,2-dichloroethylene incorporates an uncertainty factor of 10 for subchronic-to-chronic extrapolation.) This subchronic value is also provided as the subchronic p-RfD in the PPRTV document for cis-2,2-dichloroethylene.This RfC is based on conversion of the RfD, using the pre-rounding RfD and a conversion factor of 70 kg/20m3. (d) No PPRTV is available.Trans-1,2-Dichloroethylene Toxicity Value2008 MCPToxicity Value 2008 MCPTox Value ReferenceIRIS ValuePublished September 2010Value Recommended by DEP in 2012 Chronic Oral RfD2 x 10-2 mg/(kg-day)12 x 10-2 mg/(kg-day)2 x 10-2 mg/(kg-day)Subchronic Oral RfD2 x 10-1 mg/(kg-day)2Not provided 2 x 10-1mg/(kg-day) (a)Chronic Inhalation RfC7 x 10-2 mg/m339Not provided6 x 10-2 mg/m3(b)Subchronic RfC7 x 10-1 mg/m31kNot provided6 x 10-2 mg/m3 (b)(c)Oral Cancer Slope FactorNANANon-carcinogenInhalation Unit Risk FactorNANANon-carcinogenReferences for 2007 MCP Toxicity Values, Trans-1,2-Dichloroethylene – Table 1:1 IRIS2 HEAST39 Conversion of the oral Reference Dose to a Reference Concentration, using the equation:RfC = RfD x BW/Ventilation RateRfC = RfD x 70 kg/(20 m3/day)1k The subchronic RfC is set equal to a multiple (often, but not always 10) of the chronic RfC based on information about subchronic toxicity presented in the IRIS file.Notes on Recommended Values:The recommended subchronic toxicity value is set at the subchronic value from which the chronic value is derived. (The IRIS chronic RfD for trans-1,2-dichloroethylene incorporates an uncertainty factor of 10 for subchronic-to-chronic extrapolation.) This value is the chronic p-RfC from the PPRTV document for trans-1,2-dichloroethylene. The chronic PPRT RfC incorporates a subchronic-to-chronic uncertainty factor, but the value of the factor is not reported in the PPRTV summary. Until the correct uncertainty factor can be identified, the subchronic RfC will be set equal to the chronic RfC.1,4-Dioxane Toxicity Value2008 MCPToxicity Value 2008 MCPTox. ValueReferenceIRIS ValuePublished August 2010Value Recommended by DEP in 2012 Chronic Oral RfD1 x 10-2 mg/(kg-day)53 x 10-2 mg/(kg-day)3 x 10-2 mg/(kg-day)Subchronic Oral RfD1 x 10-1 mg/(kg-day)5Not provided 3 x 10-2 mg/(kg-day) (a)Chronic Inhalation RfC1.2 x 10-1 mg/m32Not provided1.2 x 10-1 mg/m3 (b)Subchronic RfC1.2 x 10-1 mg/m340Not provided1.2 x 10-1 mg/m3 (b)Oral Cancer Slope Factor1.1 x 10-2 per mg/(kg-day)11 x 10-1 per mg/(kg-day)1 x 10-1 per mg/(kg-day)Inhalation Unit Risk Factor4.1 x 10-6 per ?g/m33Not provided4.1 x 10-6 per ?g/m3References for 2008 MCP Toxicity Values for 1,4-Dioxane:1 IRIS2 HEAST3 CHEM/AAL5 This value was developed by MassDEP air and water toxics staff.40 The Subchronic Inhalation Reference Concentration is taken to be equal to the chronic value, absent clear chemical-specific information justifying a higher value.Notes for Recommended Toxicity Values for 1,4-Dioxane: The subchronic value is set equal to the chronic value. The chronic value is based on a chronic study. The available information does not provide guidance for extrapolating to a subchronic value. This value is the one currently used in the 2008 MCP. No better source of information has been identified. There is no PPRTV for this value.Hexachloroethane Toxicity Value2008 MCPToxicity Value DEP Method 1ReferenceIRIS ValuePublished around 2011Value Recommended by DEP in 2012 Chronic Oral RfD1 x 10-3 mg/(kg-day)17 x 10-4 mg/(kg-day)7 x 10-4 mg/(kg-day)Subchronic Oral RfD1 x 10-2 mg/(kg-day)2Not provided2 x 10-3 mg/(kg-day) (a)Chronic Inhalation RfC3 x 10-3 mg/m333 x 10-2 mg/m33 x 10-2 mg/m3Subchronic RfC3 x 10-3 mg/m340Not provided3 x 10-1 mg/m3 (a)Oral Cancer Slope Factor1.4 x 10-2 per mg/(kg-day)14 x 10-2 per mg/(kg-day)4 x 10-2 per mg/(kg-day)Inhalation Unit Risk Factor4 x 10-6 per ?g/m31Not provided – Withdrawn from IRIS?4 x 10-6 per ?g/m3 (b)References for 2008 MCP Values1 IRIS2 HEAST3 CHEM/AAL40 The Subchronic Inhalation Reference Concentration is taken to be equal to the chronic value, absent clear chemical-specific information justifying a higher value.Notes on Values Recommended by DEP in 2012 The recommended subchronic toxicity value is set at the subchronic value from which the chronic value is derived. (The IRIS chronic RfD for hexachloroethane incorporates an uncertainty factor of 3 for subchronic-to-chronic extrapolation. The IRIS chronic RfC for hexachloroethane incorporates an uncertainty factor of10 for subchronic-to-chronic extrapolation.) This value appears to have been withdrawn from IRIS. The IRIS file updated on September 23, 2011 states: “In the absence of data on the carcinogenicity of hexachloroethane via the inhalation route, an inhalation unit risk has not been derived.”Pentachlorophenol Toxicity Value2008 MCPToxicity Value 2008 MCP Tox. Value ReferenceIRIS ValuePublished September 2010Value Recommended by DEP in 2012 Chronic Oral RfD3 x 10-2 mg/(kg-day)15 x 10-3 mg/(kg-day)5 x 10-3 mg/(kg-day)Subchronic Oral RfD3 x 10-2 mg/(kg-day)2Not provided 5 x 10-3 mg/(kg-day) (a)Chronic Inhalation RfC7 x 10-5 mg/ m3 3Not provided 7 x 10-5 mg/ m3 (b)Subchronic RfC7 x 10-5 mg/m3 40Not provided 7 x 10-5 mg/m3 (b)Oral Cancer Slope Factor1.2 x 10-1 permg/(kg-day)14 x 10-1 permg/(kg-day)4 x 10-1 per mg/(kg-day)Inhalation Unit Risk Factor3.43 x 10-5 per ?g/m335Not provided 1 x 10-4 per ?g/m3 (c)References for 2008 MCP Values:1 IRIS2 HEAST3 CHEM/AAL35 Conversion of the oral Cancer Slope Factor to the inhalation Unit Risk, using the equation: URF = Cancer Slope Factor x Vent. Rate X Constant/BWURF = Cancer Slope Factor x (20 m3/day) x (0.001 mg/?g)/70 kg40 The Subchronic Inhalation Reference Concentration is taken to be equal to the chronic value, absent clear chemical-specific information justifying a higher value.Notes on Recommended Values:The subchronic value is set equal to the chronic value. The chronic value is based on a chronic study. The available information does not support applying a chronic-to-subchronic adjustment factor. No change is recommended.This inhalation unit risk factor is calculated from the oral cancer slope factor using conversion factors of 20 m3/70 kg and 1 mg/1000 ?g.2,3,7,8-Tetrachlorodibenzo-p-dioxinToxicity Value2008 MCPToxicity Value 2008 MCP Tox. Value ReferenceIRIS ValuePublished February 2012Value Recommended by DEP in 2012 Chronic Oral RfDNoneNA7 x 10-10 mg/kg-day7 x 10-10 mg/kg-daySubchronic Oral RfDNoneNANone7 x 10-10 mg/kg-day (a)(b)Chronic Inhalation RfCNoneNANoneNoneSubchronic RfCNoneNANoneNoneOral Cancer Slope Factor1.5 x 105 per mg/(kg-day)2None1.5 x 105 per mg/(kg-day)Inhalation Unit Risk Factor3.3 x 101 per μg/m32None3.3 x 101 per μg/m3References for 2008 MCP Method 1 Standards for 2,3,7,8-Tetrachlorodibenzo-p-dioxin2 HEASTNotes on Values Recommended by DEP in 2012 for 2,3,7,8-Tetrachlorodibenzo-p-dioxinThe subchronic value is set equal to the chronic value. The chronic value is based on a chronic study. The available information does not support applying a chronic-to-subchronic adjustment factor. From IRIS 2012: Although chronic effect levels are not well defined for humans, animal bioassays indicate that duration of exposure is not likely to be a determining factor in toxicological outcomes.1,1,2,2-TetrachloroethaneToxicity Value2008 MCPToxicity Value 2008 MCP Tox Value ReferenceIRIS ValuePublished September 2010Value Recommended by DEP in 2012 Chronic Oral RfDNone2 x 10-2 mg/(kg-day)2 x 10-2 mg/(kg-day)Subchronic Oral RfDNone5 x 10-2 mg/(kg-day)5 x 10-2 mg/(kg-day)Chronic Inhalation RfC9.3 x 10-2 mg/m33Not provided 9.3 x 10-2 mg/m3 (a)Subchronic RfC9.3 x 10-2 mg/m340Not provided 9.3 x 10-2 mg/m3 (a)Oral Cancer Slope Factor2 x 10-1 permg/(kg-day)12 x 10-1 permg/(kg-day)2 x 10-1 permg/(kg-day)Inhalation Unit Risk Factor5.8 x 10-5 per ?g/m31Not provided – withdrawn?5.8 x 10-5 per ?g/m3 (b)References for 2008 MCP Values for 1,1,2,2-Tetrachloroethane:1 IRIS3 CHEM/AAL40 The Subchronic Inhalation Reference Concentration is taken to be equal to the chronic value, absent clear chemical-specific information justifying a higher value.Notes for 2012 Values Recommended by DEP for 1,1,2,2-Tetrachloroethane:This value is the one currently used in the 2008 MCP. No better source of information has been identified. There is no PPRTV for this value. This value appears to have been withdrawn from IRIS. The IRIS Summary states: “In the absence of any data on the carcinogenicity of 1,1,2,2-tetrachloroethane via the inhalation route, an inhalation unit risk has not been derived in this evaluation.TetrachloroethyleneToxicity Value2008 MCP Toxicity Value2008 MCPTox ValueReferenceIRIS ValuePublished March 2010Value Recommended by DEP in 2012 Chronic Oral RfD1 x 10-2 mg/(kg-day)(1)6 x 10-3 mg/(kg-day)6 x 10-3 mg/(kg-day)Subchronic Oral RfD1 x 10-1 mg/(kg-day)(2)None6 x 10-3 mg/(kg-day) (a)Chronic Inhalation RfC4.6 x 100 mg/m3(3)4 x 10-2 mg/m34 x 10-2 mg/m3Subchronic RfC4.6 x 100 mg/m3(40)None4 x 10-2 mg/m3Oral Cancer Slope Factor5 x 10-2 permg/(kg-day)(2c)2 x 10-3 per mg/(kg-day)6 x 10-2 permg/(kg-day) (c)Inhalation Unit Risk Factor5.52 x 10-5 per μg/m3(Note: MassDEP published an interim value of 1 x 10-5 per μg/m3 in 2008)(3)3 x 10-7 per μg/m3 1 x 10-5 per μg/m3 (b)References for Method 1 StandardsU.S. EPA, Integrated Risk Information System (IRIS). On-line search current as of January 10, 2007.HEAST2c This cancer slope factor was taken from a fact sheet distributed by the U.S. EPA Superfund Health Risk Technical Support Center at ECAO-Cincinnati, current as of September 2, 19922d Withdrawn from HEAST3 CHEM/AAL [NOTE: The 1995 AAL is 0.07. The value of 4.3 is the AAL with the source contribution factor removed.]40 The Subchronic Inhalation Reference Concentration is taken to be equal to the chronic value, absent clear chemical-specific information justifying a higher value.Notes for carbon tetrachloride Table 1 – revisions recommended for 2012The subchronic value is set equal to the chronic value. The chronic toxicity value is based on a chronic study. The available information does not provide guidance for extrapolation to a subchronic value.(b) Based on the toxicity values used in 2011-2012 AAL revisions.(c) This value is presented in the IRIS Health Assessment for tetrachloroethylene as the one that would result from including the leukemia data in the development of the oral slope factor. It is derived from and consistent with the proposed inhalation unit risk factor, which also includes consideration of leukemia data. The slope factor recommended on IRIS does not include the leukemia data.1,1,1-Trichloroethane Toxicity ValueMCP 2008Toxicity Value MCP 2008 Method 1ReferenceIRIS ValuePublished in 2007Value Recommended by DEP in 2012 Chronic Oral RfD9 x 10-2 mg/(kg-day)2d2 x 100 mg/(kg-day)2 x 100mg/(kg-day)Subchronic Oral RfD9 x 10-1 mg/(kg-day)2d7 x 100 mg/(kg-day)7 x 100 mg/(kg/day)Chronic Inhalation RfC5.2 x 100 mg/m335 x 100 mg/m35 x 100 mg/m3Subchronic RfC5.2 x 100 mg/m3405 x 100 mg/m35 x 100 mg/m3Oral Cancer Slope FactorNAInadequate dataNon-carcinogenInhalation Unit Risk FactorNAInadequate dataNon-carcinogenReferences for 2008 MCP Values:2d HEAST, Withdrawn.3 CHEM/AAL40 The subchronic RfC is taken to be equal to the chronic RfC, absent clear chemical-specific information justifying a higher value.Trichloroethylene Toxicity Value2008 MCP Toxicity Value2008 ReferenceIRIS ValuePublished Sept. 2011Value Recommended by DEP after Sept. 2011 Chronic Oral RfD2E-3 mg/kg-day45 x 10-4 mg/kg/day5 x 10-4 mg/kg/daySubchronic Oral RfD2E-2 mg/kg-day4NA5 x 10-4 mg/kg-day (b)Chronic Inhalation RfC1.8E-1 mg/m332 x 10-3 mg/m32 x 10-3 mg/m3Subchronic RfC1.8E-1 mg/m340NA2 x 10-3 mg/m3 (b)Oral Cancer Slope Factor1.1E-2 1/ (mg/kg-day)2c5 x 10-2 per mg/(kg-day) (a)5 x 10-2 per mg/(kg-day)Inhalation Unit Risk Factor1.7E-6 1/(?g/m3)2d4 x 10-6 per ?g/m3) (a)4 x 10-6 per ?g/m3References for 2008 MCP Values for Trichloroethylene:4 - Developed for the Risk Assessment ShortForm – Residential Scenario (MA DEP 1992) by MA DEP staff. Documentation of this value may be found in that document.3 - CHEM/AAL40 - The Subchronic Inhalation Reference Concentration for this chemical is taken to be equal to the chronic value, absent clear chemical-specific information justifying a higher value.2c – This Cancer Slope Factor or Unit Risk was taken from a fact sheet distributed by the U.S. EPA Superfund Health Risk Support Center at ECAO-Cincinnati, current as of September 1992.2d – This value has been withdrawn from HEAST, although many consultants may continue to use it, lacking any new information. Consult HEAST for any additional information.Notes on 2012 Recommended Values for Trichloroethylene: Application of ADAFs is recommended for a portion of the cancer risk, but are not included in the DEP recommended value. Noncancer toxicity values consider multiple critical effects, including fetal heart defects following exposure during development, which is a short window of exposure relative to both subchronic and chronic exposure periods. Therefore the chronic RfC and RfD are used for subchronic exposures as well. RfCs based on AAL RevisionsUnits: mg/m3ChemicalChronic RfCSubchronic RfC2008 MCP2008 RefNew AAL – based2008 MCP2008 RefNew AAL-Based RfCArsenic2.5 x 10-632 x 10-52.5 x 10-6402 x 10-5Benzene 3 x 10-211 x 10-29 x 10-21k1 x 10-2Unit Risk Factors Based on AAL RevisionsUnits: Risk per ?g/m3Chemical2008 MCP URF2008 MCP Ref.New AAL-Based ValueArsenic4.3 x 10-313 x 10-3 (Cal EPA 2009)Tetrachloroethylene5.52 x 10-531 x 10-5 (MassDEP 2008)Benzene 7.8 x 10-618 x 10-6 (EPA 2003)References for 2008 Toxicity Values:IRIS1k Subchronic RfC is set at a multiple of the chronic RfC based on information presented in the IRIS file.CHEM/AAL40 Subchronic is set equal to the chronic value.Attachment APerchlorate RfD UpdateIn, June of 2006, ORS published the Update to the “Perchlorate Toxicological Profile and Health Assessment.” The document can be found at: Update provides a perchlorate RfD of 7 x 10-5, which ORS recommends for MCP risk assessment purposes. IRIS contains a different RfD for perchlorate, but DEP does not consider it to be sufficiently protective. Summary:The final chronic RfD for perchlorate recommended by ORS is 7 x 10-5.The Method 1 Standards spreadsheets use the DRAFT RfD of 3 x 10-5 mg/kg-day. To date, the standards have not been updated to incorporate the final value. The recommended RfD is based on acute effects from short-term exposures. Therefore the recommended subchronic RfD is equal to the chronic RfD.Attachment B1,4-Dioxane Drinking Water Guideline UpdateThe revised Massachusetts Drinking Water Guideline for 1,4-dioxane of 0.0003 mg/L was published in June of 2011 in the Standards and Guidelines for Contaminants in Massachusetts Drinking Waters, which can be found on MassDEP’s web site at . A summary of the basis for the revised guideline can be found on DEP’s web site at ability to detect 1,4-dioxane at low levels is a critical issue in setting the drinking water guideline. The text that follows summarizes the consideration of analytical limitations:Identifying an Analytical Method for 1,4-Dioxane in Drinking WaterSummary of Issue:In conjunction with its update of the toxicological basis of its drinking water guidance value for 1,4-dioxane, the MassDEP Office of Research and Standards (ORS) sought input from the analytical community on the feasibility of detecting 1,4-dioxane at a concentration ten-fold lower than its existing guidance value. Based on information indicating that the analytical capability exists to detect 1,4-dioxane at this lower concentration, ORS plans to set the new guideline at its health-based level. This is an Office of Research and Standards Guideline (ORSG) which is presented for the convenience of those who have to interpret data on 1,4-dioxane in drinking water or other water resources. As such there is no Massachusetts mandated requirement for routine monitoring of this chemical. Health Basis:ORS periodically updates its drinking water guidance to reflect new toxicity information issued by the US Environmental Protection Agency (US EPA). ORS evaluates both the non-cancer and cancer information and sets a health-based guidance value that is protective for both non-cancer and cancer health endpoints. The cancer-based toxicity value is set at a concentration corresponding to an Excess Lifetime Cancer Risk of one in one million, or a one-in-a-million chance of getting cancer above background cancer incidence upon daily exposure to that concentration for a lifetime. In the last year, the US EPA revised its cancer potency estimate for 1,4-dioxane by about ten-fold, resulting in a ten-fold decrease in the toxicological basis of the drinking water guidance value for 1,4-dioxane. The current ORSG for 1,4-dioxane, last updated in 2004, is 3.0 ppb. The toxicologically-based value determined in this 2011 most recent update is 0.3 ppb.Analytical Capabilities:One of the considerations in setting drinking water criteria for chemicals is the capability for quantitating the chemical analytically at concentrations as least as low as the criterion level. This level is designated as the analytical Practical Quantitation Limit (PQL) or Reporting Limit (RL).? A drinking water guidance value cannot be set at a concentration below the concentration at which it can be quantified.? If a health-based guidance value for a chemical is below the analytical detection limit for that chemical, the guidance value is set at that detection limit. It is therefore important that the detection limit identified balances the need to detect concentrations of potential toxicological concern with the need to select a detection limit that can be routinely and reliably achieved by the laboratory community.In order to determine the existing capabilities for detecting such a low concentration of this chemical, ORS contacted Ann Marie Allen from the MassDEP Wall Experiment Station (WES) to discuss what an achievable and reasonable PQL for 1,4-dioxane might be. While WES does not typically analyze for this contaminant, she indicated that a variety of modified methods and protocols were currently being used spanning a range of detection limits.EPA Region 1 had a 2003 Standard Operating Procedure (SOP) for 1,4-dioxane with a noted PQL of 1.0 ppb, which was referenced in ORS’ documentation for its 2004 1,4-dioxane guideline. The Region 1 SOP has been updated with a new PQL of 2.0 ppb (US EPA/Reg1, 2004). The reason for this update was not clear and ORS was unsuccessful in finding a person with whom to discuss this from the Region 1 office. ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download