DRAFT Guidance in Developing Health Criteria for Determining Unreasonable Risks to Health October, 1990 Office of Drinking Water U.S. Environmental Protection Agency Washington, DC 20460 Printed on Recycled Paper ------- Purpose The purpose of this guidance is to provide information and recommendations on the health based criteria that should be considered in determining an unreasonable risk to health (URTH) for drinking water contaminants. This guidance will assist States having primacy in the issuance of a variance or exemption from a Maximum Contaminant Level (MCL). In this guidance, EPA is providing several ways that an URTH value might be determined. Actual values are stated for various contaminants with an upper bound URTH level that is recommended. This document provides EPA's guidance to States on determining URTH values. It-does not establish or affect legal rights or obligations. It does not establish a binding norm and is not finally determinative of the issues addressed. Agency decisions in any particular case will be made applying the law and regulations on the basis of specific facts and actual action. Background Under Sections 1415 and 1416, respectively, of the Safe Drinking Water Act (SDWA) of 1974, as amended in 1986, States with primacy may grant a variance or exemption to a public water supply (PWS) from an MCL if the State finds that the variance or exemption will not result in an unreasonable risk to health to persons served by the PWS. -1- ------- In 1979, EPA developed a guidance document on the issuance of variances or exemptions. This document listed four criteria to be considered in determining the *unreasonableness1 of risk: 1. The degree to which the MCL is or will be exceeded and the health effects resulting therefrom; 2. The duration of the requested variance or exemption; 3. Historical data (how long the problem has existed); and 4. The type of population exposed. Utilizing these criteria, an URTH level was generally determined as any concentration of a contaminant that was greater than two times the MCL. After the 1986 Amendments of the SDWA, the 1979 URTH guidance was reevaluated. This document replaces the 1979 guidance and has expanded on the above criteria to better characterize the potential health risks that may result with the exceedance of an MCL. Under SDWA section 1415, a variance may be issued to a PWS only after the system has applied the best technology or treatment technique that the Administrator finds available. A variance is usually granted to a system because the characteristics of the raw -2- ------- water supply available to the system are such that the system cannot meet the requirements of the MCL(s) despite application of the best available technology. At the time a variance is granted, Section 1415(A)(i) provides that the primacy Stats shall prescribe a schedule for compliance with the MCL(s). The compliance schedule may include increments of progress and the implementation of additional control measures by the PWS to meet the MCL(s). Under SOW A section 1416, an exemption for a PWS may be granted if the PWS is unable to comply with an MCL or treatment technique for a drinking water contaminant. The inability to comply may be due to compelling factors such as economic constraints. An exemption is granted for one year with an exten-sion for two additional years, if necessary. In instances where a PWS serves 500 or less service connections, an exemption may be renewed for one or more 2-year periods if the system demonstrates that it is taking all practicable steps for compliance. Approach for Developing Health Criteria In developing the Health Criteria for determining URTH, the toxicity exhibited by each contaminant is evaluated individually. This is done^ in part, by considering any available risk assess- ments conducted for each contaminant. The various types of risk assessments that could be considered are discussed below. In evaluating the assessments, carcinogenic risks should be compared with risks for non-cancer health effects. This comparison serves -3- ------- to balance the potential- risks. Thus, the consideration of one type of risk such as cancer would not exclude the consideration of another endpoint of toxicity such as reproductive effects. Risk Aas< The Environmental Protection Agency (EPA) regulates contami- nants that may pose an adverse health risk and are known or anticipated to occur in water. Because of the chemical make up and behavior of a given contaminant, each contaminant may elicit a toxic response that differs from another contaminant. The toxicity for a given contaminant is considered in developing the Maximum Contaminant Level Goal (MCLG), a non-enforceable health goal. Under the SOW A, the MCL, or enforceable standard, is set as close to the MCLG as feasible. Usually the MCL will equal the MCLG. In some cases (e.g., carcinogens), however, the MCL may exceed the MCLG based on feasibility. Although the MCL may be somewhat higher than the health goal, it represents a level of acceptable risk that the Agency considers to be reasonable. Thus, MCLs are determined for each contaminant considering the toxicity exhibited by that contaminant, technological capabilities, costs and residual risk. Since MCLs are determined contaminant by contaminant, the level above an MCL that constitutes an unreasonable risk to health should also be evaluated v , -4- ------- The mechanism for producing a toxic response for a given contaminant may be considered as threshold or non-threshold. For a threshold response, exposure to a specific dose can result in a toxic outcome, whereas for non-threshold response, exposure to any level can theoretically lead to a toxic outcome. However, the hypothetical risk at low levels can be very small. Most non- cancer health effects are thought to result from a threshold level. The biological mechanism for carcinogenesis is not well understood; therefore, a non-threshold mechanism is assumed. EPA assesses the health risks for threshold effects differently from non-threshold effects. Threshold; A quantitative risk assessment for threshold contaminants can be derived through first determining a Reference Dose (RfD). The RfD can be summarized as an estimate of a daily exposure to the human population, including sensitive subpopula- tions, that is not likely to produce any adverse health effects over a lifetime. The RfD is calculated by dividing a no- or lowest-observed-adverse-effect level (NOAEL or LOAEL) by uncertainty factors. The NOAEL or LOAEL is identified from an experimental study of appropriate exposure duration in humans or animals reflecting a sensitive endpoint in a sensitive species. The uncertainty factors may range from 1 to 10,000 or more, depending on the data base for the chemical. The uncertainty factors are used to account for differences in response to toxicity within and between species. Additional factors may be used when a NOAEL has not been identified or to account for data base -5- ------- quality. For threshold contaminants, the RfD serves as the basis of the MCLG. The RfD is adjusted for a 70-kg adult consuming an average of 2 liters of water per day over a lifetime (70 years). The resulting value is called a Drinking Water Equivalent Level (DWEL), and assumes that all of the exposure comes from drinking water. Since this often is not the case, the DWEL is adjusted by an assumed or actual exposure (the relative source contribution; RSC) from drinking water. If actual data are not available, a range of 20 to 80% may be used for the RSC. This final value is the MCLG. In addition to the RfD, risk assessments are also conducted for less-than-lifetime exposures to drinking water contaminants. These are expressed by EPA in non-enforceable Health Advisories (HAs). The HAs are based on non-cancer endpoints of toxicity and are developed for exposures of one day, ten days, longer-term (up to seven years) , as well as lifetime (70 years) . They are calcu- lated in a manner similar to the RfD with the exception that the NOAELs and LOAELs are identified from studies where the exposure duration is comparable to that which the HA represents in terms of percentage of lifetime exposed. In addition, less-than-lifetime HAs are calculated for a 10 kg child consuming 1 liter of water per day. Other sources of exposure are generally not considered since water is assumed, to be the major source o£ exposure for a short period such as an accidental spill. One-day HAs are based on acute -6- ------- exposure studies of 1 to. 7 days. 'The Ten-day HA is derived from human or animal studies with 30 days exposure or less. The Longer- term HA, calculated for both a child and an adult, is derived from subchronic studies based on exposure periods correlating to approximately 10 percent of an individual's lifetime. Assuming a 70-year lifetime, the Longer-term HA correlates to an exposure period of up to 7 years. The Lifetime HA is determined in the same way as the MCLG. Non-threshold: The EPA assumes, in the absence of any contrary data, that carcinogenicity is a toxic response that does not have a threshold. In other words, any exposure can lead to a carcinogenic response. The EPA evaluates contaminants that may be carcinogenic qualitatively as well as quantitatively. Table l summarizes the EPA cancer classification scheme. This scheme qualitatively ranks chemicals as to their carcinogenic potential in humans based on weight of evidence presented in the available toxicological and epidemiological literature. If toxicological evidence leads to the classification of a contaminant as a human (Group A), probable human (Group B) or in some instances possible human (Group C) carcinogen, mathematical models can be used to calculate a theoretical upper-bound excess cancer risk associated with the ingestion of the contaminant in drinking water. Using these models, risks from oral exposure can be estimated for excess cancers compared to the population (e.g., one in 10,000 [10*4] to one in one million [10**]). The 10"* to 10" -7- ------- 6 risk range is the target for setting MCLs for human or probable human carcinogens. Often data used in these estimates come from lifetime exposure studies in animals. MCLGs for non-threshold contaminants are set at zero as an aspirational goal. The MCL, then, is set as close to zero as feasible, generally falling in the excess cancer risk range of 10" 4 to 10"6. MCLGs for Group C contaminants are usually derived from the RfD approach with an additional uncertainty factor of 1 to 10 to account for possible carcinogenicity. If an RfD is not available for a Group C contaminant, the HCLG nay be set in the range of 10"5 to 10"6. -8- ------- Group A; Human carcinogen Sufficient evidence in epidemiologic or occupational studies to support causal association between exposure and cancer in humans. Group B; Probable human carcinogen Limited evidence in human studies (Group Bl) and/or sufficient evidence from animal studies (Group B2) Group Ct Possible human carcinogen Limited evidence from animal studies and inadequate or no data in humans Group D; Not classifiable Inadequate or non human and animal evidence of carcinogenicity Group E; No evidence of carcinogenicity for humans No evidence of carcinogenicity in at least two adequate animal tests in different species or in adequate human and animal studies Source: USEPA 1986. Federal Register 51:33992-34003. Sept. 24. Risk Assessments for Determining URTH The above risk assessment methodologies used to develop HAs, MCLGs and MCLs are used in determining the health criteria for URTH levels. As stated earlier, contaminants classified as carcinogens may also exhibit noncancer related health effects such as reproductive texicity. Thus, the risk assessments for both cancer and noncancer effects must be compared. Exposure duration should also be considered. The risk -9- ------- assessments for both cancer and noncancer effects are time dependent. Cancer assessments usually assume a lifetime exposure, while the risk assessments for noncancer effects cover less-than- lifetime and lifetime exposures. Ideally, the variance or exemption period will cover a less-than-lifetime exposure period. In addition, past exposure to a given contaminant may not be known. Some of the values for URTH provided in this document are based on the Longer-term HA which assume exposures of seven years or less. Therefore, EPA recommends that variances or exemptions not exceed seven years when URTH is based on noncarcinogenic health effects. The risk assessments for URTH are presented as a range from the MCL to an upper-bound (least stringent) level. The EPA recommends that the upper-bound not be exceeded when determining URTH. However, the State may determine URTH to lie within or outside the range based on site-specific considerations. These considerations may include, for example, site-specific exposures, past exposure (if known), population sensitivity or volatility of the contaminant. The types of risk, assessment values used in developing the range of health criteria are: 1. The MCLG and MCL. 2. The Longer-term Health Advisory for a child. 3. DWEL. 4. Cancer classification. 5. The 10"* cancer risk level. -10- ------- 6. MCLG multiplied by a factor of one to ten for Group c contaminants. When determining the upper-bound URTH level, EPA considered that : for threshold contaminants where the MCL is based on 0 Acute toxicity: the MCL is appropriate to use for URTH whenever the MCL for a contaminant is based on an acutely toxic response and there is little margin of safety above the MCL. Where there is a greater margin of safety, some exceedance of the MCL based on scientific judgment may be reasonable. 0 Subchronic and chronic toxicity: the Longer-term HA for a child could be used for URTH. This level of exposure is considered protective of a potentially sensitive subgroup over a seven year period. 0 the DWEL may be used for URTH when data to calculate a Longer-term HA are not available. for nonthreshold contaminants 0 where the MCL is set at or above the 10"* excess cancer risk, the MCL is appropriate for URTH. 0 where the MCL is set at a concentration less than the -11- ------- 10 risk level, the 10" cancer risk level may be used for URTH if this value does not exceed the DWEL or Longer-term HA for a child. The lower of these values would then be recommended as URTH. 0 where the MCL for a Group C contaminant includes an additional safety factor of 1 to 10, the removal of the factor could be used as URTH, provided that the Longer-term HA for a child or DWEL is not exceeded. The lower of these values would be recommended as URTH. Table 2 summarizes examples of how the above strategy can be applied and lists the recommended risk assessments that could be considered in determining URTH levels for drinking water contaminants. Following Table 2 is a more complete description of those values for each contaminant and EPA's recommendations for which of these values should be applied as the URTH level. ISSUES TOR COKMBHT EPA is seeking comment on the proposed approach for determining URTH. The following table and chemical specific discussions are provided as examples of how this approach could be applied. Issues to address include: 1. Is it appropriate to base URTH on the Longer-term HA for £ child fcr threshold contaminants? -12- ------- 2. Is it appropriate to base URTH on the 10"4 cancer risk for nonthreshold contaminants? Could a higher risk such as 10"3 be justified for a short period of time if noncancer risks were not exceeded? 3. Is it reasonable to limit the URTH for noncarcinogens to seven years? Should the same guidance be recommended for carcinogens? 4. Should other types of risk assessments not mentioned here be considered for determining URTH? -13- ------- Table 2. DEVELOPMENT OF URTH RANGE (MGIL) Compound INORGANICS Asbestos >10 (jm Cadmium Copper Fluoride Mercury Nitrate Nitrite Nitrate/Nitrite Selenium MICROBIOLOGICAL Total Coliforms ORGANICS Acrylamide Alachlor Atrazine Benzene MCLG • 7 MFL 0.005 1.3 4 0.002 10 1 10 0.05 0 0 0 0.003 0 Longer- Term HA MCL Child 7 MFL ~ 0.005 0.005 1.3 4 0.002 ~ 10 10 1 1 10 0.05 5%/1% - TT 0.02 0.002 - 0.003 0.06 0.005 (10 day Cancer t(T**» DWEL Class Risk A 700 0.02 B1 D D 0.01 D D .. _ 0.1 — 0.007 B2 0.001 0.4 B2 0.04 0.2 C A 0.1 URTH Level Group C Recommended MCLGxW V EPA 70 7 MFL 0.005 1.3 5 0.01 10 child 1 child, 10 child 0.1 5%/1% 0.001 0.04 0.03 0.03 -0.01 Carbofuran = 0.2) 0.04 0.04 0.05 0.2 0.05 (Continued on next page) -13- ------- Table 2. DEVELOPMENT OF URfH RANGE fMG/L) (Continued] Compound MCLG MCL Longer- Term HA Child DWEL Cancer 1O*** Class Risk URTH Level Group C Recommended MCLGxIO tiy EPA Carbon Tetrachloride Chlordane 2.4-D DBCP cis-1,2-DCE trans-1,2-DCE o-DCB p-DCB ^ichloroethane 1,1-Dichloroethylene 1,2-Dichloropropane 0 0.005 0.07 0 0.002 » 0.07 0.07 0.1 0 0.0002 -- 0.07 0.07 3 0.1 0.1 2 0.6 0.6 9 0.075 0.075 10 0 0.005 0.7 0.007 0.007 1 0 0.005 - 0.03 B2 0.002 B2 D 0.4 0.4 0.6 4 4 0.4 B2 D D D C B2 C B2 0.03 0.003 0.003 0.2 0.75 0.04 0.02 0.07 0.06 0.03 0.003 0.1 0.003 0.4 2 9 0.75 0.04 0.07 0.06 Epfchlorohydrin Ethylbenzene EDB Heptachlor Heptachlor Epoxide LJndane Methoxychlor Monochlorobenzene PCBs TT 0.07 0.7 1 0.00005 - 0.0004 0.005 0.07 3 B2 D B2 0.02 B2 0 0.7 0 0 0 0.0002 0.0001 0.0004 B2 0.0002 0.0002 0.03 0.01 C 0.4 0.4 0.5 2 D 0.1 0.1 2 0.7 D 0 0.0005 0.001 - B2 fnti. inued on next page) 0.4 0.00004 - 0.0008 - 0.0004 ~ 0.003 0.002 0.0005 - 0.07 1 0.00005 0.0008 0.0004 0.002 0.5 2 0.0005 -14- ------- Table 2. DEVELOPMENT OF URTH RANGE (MGIL) (Continued! Compound Tetrachloroethylene Toxaphene 2.4.5-TP 1,1,1 -Trichloroethane Trichloroethylene Vinyl Chloride Xylenes MCLG 0 0 0.05 0.2 0 0 10 MCL 0.005 0.003 0.05 0.2 0.005 0.002 10 Longer- Term HA Child 1 ~ 0.07 40 — 0.01 40 DWEL 0.5 0.003 .0.3 1 0.3 — 60 Cancer Class B2 B2 D D B2 A D TO4*" Group C Risk MCLGxIO 0.07 0.003 — .. 0.3 0.0015 - .. URTH Level Recommended toy EPA 0.07 0.003 0.07 1 0.3 0.002 40 TT = Treatment technique TBD = To be determined ** = 10^ Lifetime Risk -15- ------- INORGANICS Asbestos The EPA proposed an MCLG of 7 and an MCL of 7 million fibers per liter (MFL) for asbestos fibers greater than 10 /m in length based on equivocal evidence of carcinogenicity in male rats following ingestion of chrysotile fibers. There are insufficient data to determine a Longer-term Health Advisory for a child or a drinking water equivalent level. Asbestos is classified in Group A: Human carcinogen for inhalation, according to EPA's classification scheme. The 10"4 excess cancer risk estimated for asbestos is 700 MFL. There is limited evidence that asbestos may be carcinogenic by ingestion. It is unlikely that asbestos, if found in the water, would exceed 7 MFL; thus, URTH may be considered any concentration above the MCL. Cadmium The EPA proposed an MCLG of 0.005 and an MCL of 0.005 mg/L for cadmium based on renal dysfunction. The Longer-term Health Advisory for a child is also 0.005 mg/L, and the drinking water equivalent level is 0.02 mg/L. cadmium is classified in Group Bl: probable human carcinogen by inhalation with no evidence of carcinogenicity by ingestion according to the EPA's classification scheme. Based on this information and the bioaccumulative potential for cadmium, an upper-bound unreasonable risk to health level of 0.005 mg/L based on the MCLG and the Longer-term Health Advisory is recommended for a period of up to 7 years. -17- ------- Copper The EPA proposed an MCLG of 1.3 and an MCL of 1.3 mg/L for copper based on acute gastrointestinal effects in humans. A Longer-term Health Advisory for a child and the drinking water equivalent level has not been determined. Copper is classified in Group D: not classifiable for human carcinogenicity according to the EPA's classification scheme. Based on this information, an upper-bound unreasonable risk to health level of 1.3 mg/L is recommended based on acute toxicity. Fluoride The EPA promulgated an MCLG of 4 and an MCL of 4 mg/L for fluoride based on crippling skeletal fluorosis in humans. Only two cases of crippling skeletal fluorosis have been observed in this country associated with the consumption of drinking water containing fluoride levels of 8 mg/L or more. It is generally believed that the consumption of approximately 20 mg of fluoride per person per day over at least a twenty year period will increase the risk of crippling skeletal fluorosis. Thus, persons who chronically consume inordinately large amounts of water, i.e., 4 liters/day, (perhaps 1% of the population) would be at risk of crippling skeletal fluorosis at a level greater than 5 mg/L. Based on this information, an upper bound unreasonable risk to health level of 5 mg/L is recommended. -18- ------- Marcurv The EPA proposed an MCLG of 0.002 and an MCL of 0.002 mg/L for mercury based on absence of toxicity in rats following subchronic exposure to mercury. The Longer-term Health Advisory for a child has not been determined, but the drinking water equivalent level is 0.01. Mercury is classified in Group D: not classifiable as to human carcinogenicity according to the EPA's classification scheme. Based on this information, an upper-bound unreasonable risk to health level of 0.01 based on the drinking water equivalent level is recommended for a period of up to 7 years. Nitrate as M. Nitrate and Nitrate + Nitrite (measured as Nl Nitrate The EPA proposed an MCLG of 10 and an MCL of 10 mg/L (N) for nitrate based on acute toxicity in infants following ingestion of water with nitrate. Infants and particularly those with gastrointestinal disease (e.g., diarrhea) are considered the most sensitive members of the population. The consumption of biologically contaminated water (e.g., £. coin may contribute to the problem, resulting in diarrhea which may render an infant much more sensitive to nitrate and/or nitrite toxicity. -19- ------- Nitrate in drinking"water at levels in excess of the current 10 mg/L MCL has been responsible for serious methemoglobinemia and mortality in some infants under the age of approximately six months. Based on this information the URTH value for infants up to 6 months of age is 10 mg/L nitrate (as N) . Based on available epidemiology data, the URTH value for nitrate for all individuals except infants up to 6 months of age is 20 mg/L (as N) . In addition, biological water quality standards must be met in both cases. Nitrite Nitrate is toxic because it is metabolized within the human body to yield nitrite, which in turn reacts with hemoglobin to yield methemoglobin (i.e., nitrate per se does not react with hemoglobin). Nitrite may also occur in drinking water. The URTH level for nitrite should not exceed 1 mg/L as N based on methemoglobin formation following short-term exposure. Nitrate and Nitrite As both nitrate and nitrite may occur in drinking water and as exposure to either may lead to methemoglobinemia, it is reasonable to conclude that the toxicity of nitrate and nitrite •j may be additive. As a consequence, the URTH level for combined levels of nitrate and nitrite should not exceed 10 mg/L (i.e., the sun of nitrate and nitrite, as nitrogen, shall not exceed 10 mg/L). -20- ------- Selenium The EPA proposed an MCLG of 0.05 mg/L and an MCL of 0.05 mg/L for selenium based on a human study evaluating selenium deficiency. The Longer-term Health Advisory for a child is not established, but the drinking water equivalent level is 0.1 mg/L. Selenium is classified in Group D: not classifiable as to human carcinogenicity according to the EPA's classification scheme. Based on this information, an upper-bound unreasonable risk to health level of 0.1 mg/L based on the drinking water equivalent level is recommended for a period of up to 7 years. MICROORGANISMS Total Coliforms The EPA promulgated an MCLG of 0 and an MCL of 5%/l% detections for total col i forms based on acute gastrointestinal disorders. Based on the acute pathogenicity implied by the presence of total col i forms, an upper-bound unreasonable risk to health level is any exceedance of the criteria specified for the MCL. ORGXKICS The EPA proposed an MCLG of zero and a treatment technique for acrylamide based on carcinogenicity. The Longer-term Health Advisory for a child is 0.02 mg/L, and the drinking water -21- ------- equivalent level.is O.OQ7. Acrylamide is classified in Group B2: probable human carcinogen according to the EPA's classification scheme. The 10~*. excess cancer risk estimated for aery 1 amide is 0.001 mg/L. Based on this information, &n upper-bound unreasonable risk to health level of 0.001 mg/L based on the 10'4 excess cancer risk is recommended. Alaehlor The EPA proposed an MCLG of zero and an MCL of 0.002 mg/L for alachlor based on feasibility based on carcinogenicity. The Longer-term Health Advisory for a child has not been calculated, but the drinking water equivalent level is 0.4 mg/L. Alachlor is classified in Group B2: probable human carcinogen according to the EPA's classification scheme. The 10"4 excess cancer risk estimated for alachlor is 0.04 mg/L. Based on this information, an upper-bound unreasonable risk to health level of 0.04 mg/L based on the 10"* excess cancer risk is recommended. Atratine The EPA proposed an MCLG of 0.003 and an MCL of 0.003 mg/L for atrazine based on cardiac effects in dogs fed atrazine for one year. The Longer-term Health Advisory for a child is 0.05 mg/L, and the drinking water equivalent level is 0.2 mg/L. Atrazine is classified in Group C: possible human carcinogen according to the EPA's classification scheme. EPA applied an additional 10-fold uncertainty f*etrvr in calculating the MCLG for atrazine to account for possible carcinogenicity; without ttiis additions! factor, the -22- ------- MCLG would have been 0.03 mg/L. • Based on this information, an upper-bound unreasonable risk to health level of 0.03 mg/L based on the removal of.the extra 10-fold UF and the Longer-term Health Advisory for a child is recommended for a period of up to 7 years. Benzene The EPA promulgated an MCLG of zero and an MCL of 0.005 mg/L for benzene based on feasibility. There are insufficient data to calculate a Longer-term Health Advisory for a child or a drinking water equivalent level for non-cancer health effects. However, a Ten-day Health Advisory of 0.2 mg/L has been estimated. Benzene is classified in Group A: human carcinogen according to the EPA's classification scheme. The 10*4 excess cancer risk estimated for benzene is 0.1 mg/L. Ordinarily, the 10"4 excess cancer risk would be recommended for the upper bound URTH. However, the 10~* risk of 0.1 mg/L is virtually the same as the Ten-day Health Advisory of 0.2 mg/L. Also, taking into consideration that benzene is also classified in Group A, the upper bound urth for this compound is recommended at the 10"5 cancer risk of 0.01 mg/L. Carbofuraii The EPA proposed an MCLG of 0.04 and an MCL of 0.04 mg/L for carbofuran based on absence of cholinesterase or reproductive effects in dogs fed carbofuran one year. The Longer-term Health Advisory for a child is 0.05 mg/L, and the drinking water equivalent level is 0.2 mg/L. Carbofuran is classified in Group E: no evidence of human carcinogenicity according to the EPA's -23- ------- classification scheme. .Based on this information, an upper-bound unreasonable risk to health level of 0.05 mg/L based on the Longer- term Health Advisory is recommended for a period of up to 7 years. Carbon tetrachloride The EPA promulgated an MCLG of zero and an MCL of 0.005 mg/L for carbon tetrachloride based on carcinogenicity. The Longer- term Health Advisory for a child is 0.07 mg/L, and the drinking water equivalent level is 0.03 mg/L. Carbon tetrachloride is classified in Group B2: probable human carcinogen according to the EPA's classification scheme. The 10"4 excess cancer risk estimated for carbon tetrachloride is 0.03 mg/L. Based on this information, an upper-bound unreasonable risk to health level of 0.03 mg/L based on the drinking water equivalent level is recommended. Chiordan• The EPA proposed an MCLG of zero and an MCL of 0.002 mg/L for chlordane based on carcinogenicity and technological feasibility. The Longer-term Health Advisory for a child has not been calculated, but the drinking water equivalent level is 0.002 mg/L. Chlordane is classified in Group B2: probable human carcinogen according to the EPA's classification scheme. The 10"* excess cancer risk estimated for chlordane is 0.003 mg/L. Based on this information, an upper-bound unreasonable risk to health level of 0.003 mg/L based on the 10"* cancer risk is recommended. -24- ------- The EPA proposed an MCLG of 0.07 and an MCL of 0.07 mg/L for 2,4-D based on liver and kidney effects in animals. The Longer- term Health Advisory for a child is 0.1 -ng/L, and the drinking water equivalent level is 0.4 mg/L. 2,4-D is classified in Group D: not classifiable as to human carcinogenicity according to the EPA's classification scheme. Based on this information, an upper-bound unreasonable risk to health level of 0.1 mg/L based on the Longer-term Health Advisory is recommended for a period of up to 7 years. DBCP The EPA proposed an MCLG of zero and an MCL of 0.0002 mg/L for DBCP based on carcinogenicity. The Longer-term Health Advisory for a child and the drinking water equivalent level has not been calculated. DBCP is classified in Group B2: probable human carcinogen according to the EPA's classification scheme. The 10*4 excess cancer risk estimated for DBCP is 0.003 mg/L. Based on this information, an upper-bound unreasonable risk to health level of 0.003 mg/L based on the 10*4 cancer risk is recommended. ei«-l. 2-Diehloroetlivlene The EPA proposed an MCLG of 0.07 and an MCL of 0.07 mg/L for cis-l,2-DCE based on absence of effects in a subchronic study in animals. The Longer-term Health Advisory for a child is 3 mg/L, and the drinking water equivalent level is 0.4 mg/L. cis-l,2-DCE -25- ------- is classified in Group D: not classifiable as to human carcinogenicity according to the EPA's classification scheme. Based on this information, an upper-bound unreasonable risk to health level of 0.4 mg/L based on the drinking water equivalent level is recommended for a period of up to 7 years. trans—l,2—Dlchloroethvlene The EPA proposed an MCLG of 0.1 and an MCL of 0.1 mg/L for trans-l,2-DCE based on absence of effects in a subchronic study in animals. The Longer-term Health Advisory for a child is 2 mg/L, and the drinking water equivalent level is 0.6 mg/L. trans-1,2- DCE is classified in Group D: not classifiable as to human carcinogenicity according to the EPA's classification scheme. Based on this information, an upper-bound unreasonable risk to health level of 2 mg/L based on the Longer-term Health Advisory is recommended for a period of up to 7 years. o-Dichloroben«ene The EPA proposed an MCLG of 0.6 and an MCL of 0.6 mg/L for o- dichlorobenzene (DCS) based on absence of effects in a subchronic study in rodents. The Longer-term Health Advisory for a child is 9 mg/L, and the drinking water equivalent level is 3 mg/L. o- DCB is classified in Group D: not classifiable as to human carcinogenicity according to the EPA's classification scheme. Based on this information, an upper-bound unreasonable risk to haalth level of 3 sg/L based cr. the Longer-term Health Advisory is recommended for a period of up to 7 years. -26- ------- p-Dichlorobenaene The EPA promulgated an MCLG of 0.075 and an MCL of 0.075 rag/L for p-dichlorobenzene (p-DCB) based on kidney effects observed in rats exposed to p-DCB for two years. The Longer-term Health Advisory for a child is 10 mg/L, and the drinking water equivalent level is 3 mg/L. p-DCB is classified in Group C: possible human carcinogen according to the EPA's classification scheme. EPA applied an additional 10-fold uncertainty factor to the MCLG for p-DCB to account for possible carcinogenicity; without this additional uncertainty factor, the MCLG would have been 0.75 mg/L. Based on this information, an upper-bound unreasonable risk to health level of 0.75 mg/L based on removal of the extra 10-fold UF is recommended for a period of up to 7 years. The EPA promulgated an MCLG of zero and an MCL of 0.005 mg/L for 1,2-dichloroethane based on carcinogenicity. The Longer-term Health Advisory for a child is 0.7 mg/L, and the drinking water equivalent level has not been calculated. 1,2-Dichloroethane is classified in Group B2: probable human carcinogen according to the EPA's classification scheme. The 10*4 excess cancer risk estimated for 1,2-DCE is 0.04 mg/L. Based on this information, an upper-bound unreasonable risk to health level of 0.04 mg/L based on the 10*4 excess cancer risk is recommended. -27- ------- 1.i-Dichloroethvlena The EPA promulgated an MCLG of 0.007 and an MCL of 0.007 mg/L for 1,1-dichloroethylene based on mild liver effects and possible carcinogenicity. The Longer-term Health Advisory for a child is 1 mg/L, and the drinking water equivalent level is 0.4 mg/L. 1,1- DCE is classified in Group C: possible human carcinogen according to the EPA's classification scheme. EPA applied an additional 10- fold uncertainty factor to the MCLG for 1,1-DCE; without this additional factor, the MCLG would have been 0.07 mg/L. Based on this information, an upper-bound unreasonable risk to health level of 0.07 mg/L based on removal of the extra 10-fold UF is recommended for a period of up to 7 years. 1.2-DiehloroproDan* The EPA proposed an MCLG of zero and an MCL of 0.005 mg/L for 1,2-dichloropropane (DCP) based on carcinogenicity. The Longer- term Health Advisory for a child and the drinking water equivalent level have not been calculated* 1,2-DCP is classified in Group B2: probable human carcinogen according to the EPA's classification scheme. The 10"* excess cancer risk estimated for 1,2-DCP is 0.06 mg/L. Based on this information, an upper-bound unreasonable risk to health level of 0.06 mg/L based on the 104 excess cancer risk is recommended. -28- ------- Epichlorohvdrin The EPA proposed an MCLG of zero and a treatment technique for epichlorohydrin based on carcinogenicity and technological feasibility. The Longer-term Health Advisory for a child is 0.07 mg/L, and the drinking water equivalent level is also 0.07 mg/L. Epichlorohydrin is classified in Group B2: probable human carcinogen according to the EPA's classification scheme. The 10"4 excess cancer risk estimated for epichlorohydrin is 0.4 mg/L. Based on this information, an upper-bound unreasonable risk to health level of 0.07 mg/L based on the Longer-term Health Advisory is recommended for a period of up to 7 years. Ethvlbenaene The EPA proposed an MCLG of 0.7 and an MCL of 0.7 mg/L for ethylbenzene based on kidney and liver effects in animals. The Longer-term Health Advisory for a child is 1 mg/L, and the drinking water equivalent level is 3 mg/L. Ethylbenzene is classified in Group D: not classifiable as to human carcinogenicity according to the EPA's classification scheme. Based on this information, an upper-bound unreasonable' risk to health level of 1 mg/L based on the Longer-term Health Advisory is recommended for a period of up to 7 years. Bthvlene dibreaide (BDBi The EPA proposed an MCLG of zero and an MCL of 0.00005 mg/L for EDB based on carcinogenicity. The Longer-term Health Advisory for a child and the drinking water equivalent level have not been -29- ------- calculated. EDB is classified -in Group B2: probable human carcinogen according to the EPA's classification scheme. The 10"' excess cancer risk estimated for EOB is 0.00004 mg/L. Based on this information and considering that the MCL for EDB is at the 10" 4 risk level, an upper-bound unreasonable risk to health level of 0.00005 mg/L is recommended. Heptachlor The EPA proposed an MCLG of zero and an MCL of 0.0004 mg/L for heptachlor based on carcinogenicity. The Longer-term Health Advisory for a child is 0.005 mg/L, and the drinking water equivalent level is 0.02 mg/L. Heptachlor is classified in Group B2: probable human carcinogen according to the EPA's classification scheme. The 10"* excess cancer risk estimated for heptachlor is 0.0008 mg/L. Based on this information, an upper- bound unreasonable risk to health level of 0.0008 mg/L based on the 10"4 excess cancer risk is recommended. Heptachlor epoxide The EPA proposed an MCLG of zero and an MCL of 0.0002 mg/L for heptachlor epoxide based on carcinogenicity. The Longer-term Health Advisory for a child is 0.0001 mg/L, and the drinking water equivalent level is o.ooo4 mg/L. Heptachlor epoxide is classified in Group B2: probable human carcinogen according to the EPA's classification scheme. The 10*4 excess cancer risk estimated for heptachlor epoxide is 0.0004 mg/L. Based on this information, an upper~tour.d unreasonable risk t© health level of 0.0004 mg/L based -30- ------- on the 10"* excess cancer" risk is recommended. Lindan* The EPA proposed an MCLG of 0.0002 and an MCL of 0.0002 mg/L for lindane based on liver and kidney effects in rodents. The Longer-term Health Advisory for a child is 0.03 mg/L, and the drinking water equivalent level is 0.01 mg/L. Lindane is classified in Group C: possible human carcinogen according to the EPA's classification scheme. EPA applied an addition 10-fold uncertainty factor to the MCLG to account for possible carcinogenicity; without this additional factor, the MCLG would be 0.002 mg/L. Based on this information, an upper-bound unreasonable risk to health level of 0.002 mg/L based on removal of the 10-fold UF is recommended for a period of up to 7 years. Mathoxvchlor The EPA proposed an MCLG of 0.04 and an MCL of 0.04 mg/L for methoxychlor based on reproductive effects in rodents. The Longer- term Health Advisory for a child is 0.5 mg/L, and the drinking water equivalent level is 2 mg/L. is classified in Group D: not classifiable as to human carcinogenicity according to the EPA's classification scheme. Based on this information, an upper-bound unreasonable risk to health level of 0.5 mg/L based on the Longer- term Health Advisory is recommended for a period of up to 7 years. -31- ------- Monochlorob«nz«n< The EPA proposed an MCLG of 0.1 and an MCL of 0.1 mg/L for ' monochlorobenzene based on liver and kidney effects in a subchronic study with rodents. The Longer-term Health Advisory for a child is 2 mg/L, and the drinking water equivalent level is 0.7 mg/L. Monochlorobenzene is classified in Group D: not classifiable as to human carcinogenicity according to the EPA's classification scheme. Based on this information, an upper-bound unreasonable risk to health level of 2 mg/L based on the Longer-term Health Advisory is recommended for a period of up to 7 years. Polychlorinated biphenvls (PCBs) The EPA proposed an MCLG of zero and an MCL of 0.0005 mg/L for PCBs based on carcinogenicity. The Longer-term Health Advisory for a child is 0.001 mg/L, and the drinking water equivalent level has not been calculated. PCBs are classified in Group B2: probable human carcinogen according to the EPA's classification scheme. The 10"4 excess cancer risk estimated for PCBs is 0.0005 mg/L. Based on this information, an upper-bound unreasonable risk to health level of 0.0005 mg/L based on the 10"4 risk is recommended. Tetracaicroernvi«n« The EPA proposed an MCLG of zero and an MCL of 0.005 mg/L for tetrachloroethylene based on carcinogenicity. The Longer-term Health Advisory for a child is 1 mg/L, and the drinking water equivalent level is Or5 mg/L. Tetrachloroethylene is classified -32- ------- in Group B2: probable human carcinogen according to the EPA's classification scheme. The 10~4 excess cancer risk estimated for tetrachloroethylene is 0.07 mg/L. Based on this information, an upper-bound unreasonable risk to health level of 0.07 mg/L based on the 10"4 excess cancer risk is recommended. Toxaphene The EPA proposed an MCLG of zero and an MCL of 0.003 mg/L for toxaphene based on carcinogenicity. The Longer-term Health Advisory for a child has not been calculated, but the drinking water equivalent level is 0.003 mg/L. Toxaphene is classified in Group B2: probable human carcinogen according to the EPA's classification scheme. The 10** excess cancer risk estimated for toxaphene is 0.003 mg/L. Based on this information, an upper- bound unreasonable risk to health level of 0.003 mg/L based on the 10"* excess cancer risk is recommended. 2.4.5-TP The EPA proposed an MCLG of 0.05 and an MCL of 0.05 mg/L for 2,4,5-TP based on absence of effects in a dog study. The Longer- term Health Advisory for a child is 0.07 mg/L, and the drinking water equivalent level is 0.3 mg/L. 2,4,5-TP is classified in Group D: not classifiable as to carcinogenicity according to the EPA's classification scheme. Based on this information, an upper- bound unreasonable risk to health level of 0.07 mg/L based on the Longer-term Health Advisory is recommended for a period of up to 7 years. -33- ------- 1.1,l-Trichloro«thane The EPA promulgated an MCLG of 0.2 and an MCL of 0.2 mg/L for 1,1,1-trichloroethane based on liver and kidney effects in animals. The Longer-term Health Advisory for a child is 40 mg/L, and the drinking water equivalent level is 1 mg/L. 1,1,1-Trichloroethane is classified in Group D: not classifiable as to carcinogenicity according to the EPA's classification scheme. Based on this information, an upper-bound unreasonable risk to health level of 1 mg/L based on the drinking water equivalent level is recommended for a period of up to 7 years. Trichleroethvlene The EPA promulgated an MCLG of zero and an MCL of 0.005 mg/L for trichloroethylene based on carcinogenicity. The Longer-term Health Advisory for a child has not been calculated, but the drinking water equivalent level is 0.3 mg/L. Trichloroethylene is classified in Group B2: probable human carcinogen according to the EPA's classification scheme. The 10"4 excess cancer risk estimated for trichloroethylene is 0.3 mg/L. Based on this information, an upper-bound unreasonable risk to health level of 0.3 mg/L based on the 10*4 excess cancer risk is recommended. Vinvl Chloride The EPA promulgated an MCLG of zero and an MCL of 0.002 mg/L for vinyl chloride based on carcinogenicity. The Longer-term Health Advisory for a child is 0.01 mg/L; a drinking water equivalent level has not been calculated. Vinyl chloride is -34- ------- classified in Group A: .human car'cinogen according to the EPA's classification scheme. The 10"4 excess cancer risk estimated for vinyl chloride is 0.0015 mg/L. Based on this information, an upper-bound unreasonable risk to health level of 0.002 mg/L based on the MCL, which slightly exceeds the 10"4 excess cancer risk is recommended. The EPA prbposed an MCLG of 10 and an MCL of 10 mg/L for xylenes based on body weight effects in rats. The Longer-term Health Advisory for a child is 40 mg/L, and the drinking water equivalent level is 60 mg/L. Xylenes are classified in Group D: not classifiable as to human carcinogenicity according to the EPA's classification scheme. Based on this information, an upper-bound unreasonable risk to health level of 40 mg/L based on the Longer- term Health Advisory is recommended for a period of up to 7 years. -35- ------- |