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(2) A quorum consists of five is not placed on the Internet, but will be NOEL—no observed effect level members. publicly available in hard copy form. NPDWR—National Primary Drinking Water Regulation * * * * * Publicly available docket materials are available either electronically through NRC—National Research Council Dated: February 2, 2011. PBPK—Physiologically-Based http://www.regulations.gov or in hard Thomas L. Strickland, Pharmacokinetic copy at the Water Docket, EPA/DC, EPA PWS—public water system Assistant Secretary for Fish and Wildlife and West, Room 3334, 1301 Constitution Parks, Department of the Interior. RfD—reference dose Ave., NW., Washington, DC. The Public SDWA—Safe Drinking Water Act Dated: January 18, 2011. Reading Room is open from 8:30 a.m. to UCMR—Unregulated Contaminant Beth G. Pendleton, 4:30 p.m., Monday through Friday, Monitoring Rule μ Regional Forester, USDA—Forest Service. excluding legal holidays. The telephone g—microgram (one-millionth of a gram) U.S.—United States [FR Doc. 2011–2959 Filed 2–10–11; 8:45 am] number for the Public Reading Room is BILLING CODE 3410–11–P; 4310–55–P (202) 566–1744, and the telephone I. General Information number for the EPA Docket Center is (202) 566–2426. Does this action impose any requirements on my public water FOR FURTHER INFORMATION CONTACT: Eric ENVIRONMENTAL PROTECTION system? AGENCY Burneson, Office of Ground Water and Drinking Water, Standards and Risk Today’s action notifies interested 40 CFR Part 141 Management Division, at (202) 564– parties of EPA’s determination to regulate perchlorate, but imposes no [EPA–HQ–OW–2008–0692, EPA–HQ–OW– 5250 or e-mail [email protected]. 2009–0297; FRL–9262–8] For general information contact the EPA requirements on public water systems Safe Drinking Water Hotline at (800) (PWSs). However, this action also RIN 2040–AF08 426–4791 or e-mail: hotline- initiates the process to develop a [email protected]. national primary drinking water Drinking Water: Regulatory regulation (NPDWR) for perchlorate. At SUPPLEMENTARY INFORMATION: Determination on Perchlorate such time as the Agency establishes an AGENCY: Environmental Protection Table of Contents NPDWR, certain PWSs will be required Agency (EPA). I. General Information to take action to comply with the ACTION: Regulatory determination. Does this action impose any requirements regulation in accordance with the on my public water system? schedule specified in the regulation. SUMMARY: This action presents EPA’s (or II. Background II. Background the Agency’s) regulatory determination A. What is the purpose of this action? for perchlorate in accordance with the B. Background on Perchlorate Regulatory A. What is the purpose of this action? Determinations Safe Drinking Water Act (SDWA). The purpose of today’s action is to Specifically, EPA has determined that C. What is EPA’s final regulatory determination on perchlorate and what present EPA’s final determination to perchlorate meets SDWA’s criteria for regulate perchlorate in drinking water, regulating a contaminant—that is, happens next? III. Final Regulatory Determination for the rationale EPA used to make this perchlorate may have an adverse effect Perchlorate regulatory determination, and EPA’s on the health of persons; perchlorate is A. May perchlorate have an adverse effect response to certain key issues raised by known to occur or there is a substantial on the health of persons? commenters on previous Federal likelihood that perchlorate will occur in B. Is perchlorate known to occur or is there Register (FR) notices on the drinking public water systems with a frequency a substantial likelihood that perchlorate water regulatory determination for will occur in public water systems with and at levels of public health concern; perchlorate. (All comments are and in the sole judgment of the a frequency and at levels of public health concern? addressed in a Response to Comments Administrator, regulation of perchlorate document that is available in EPA’s in drinking water systems presents a C. Is there a meaningful opportunity for the reduction of health risks from docket ID No. EPA–HQ–OW–2009–0297 meaningful opportunity for health risk perchlorate for persons served by public for this regulatory determination.) reduction for persons served by public water systems? water systems. Therefore, EPA will D. Regulatory Determination B. Background on Perchlorate initiate the process of proposing a E. Key Commenter Issues Regulatory Determinations national primary drinking water 1. Health Implications of Perchlorate The statutory and regulatory regulation (NPDWR) for perchlorate. Exposure above the RfD background for this action is described DATES: For purposes of judicial review, 2. Other Thyroid Inhibiting Chemicals 3. Perchlorate in Food in detail in the October 10, 2008, FR the regulatory determination is issued as 4. Iodide Nutritional Status notice discussing EPA’s preliminary of February 11, 2011, as provided in 40 5. Physiologically-Based Pharmacokinetic regulatory determination for perchlorate CFR 23.7. (PBPK) Modeling (73 FR 60262; USEPA 2008a). Briefly, ADDRESSES: EPA has established dockets F. Next Steps SDWA section 1412(b)(1)(A), as for this action under Docket ID numbers IV. References amended in 1996, requires EPA to make EPA–HQ–OW–2008–0692 and EPA– Abbreviations and Acronyms a determination whether to regulate at HQ–OW–2009–0297. All documents in least five contaminants from its these dockets are listed on the http:// CBI—confidential business information Contaminant Candidate List (CCL) every www.regulations.gov Web site. Although CCL—Contaminant Candidate List five years. To regulate a contaminant in listed in the index, some information is EPA—U.S. Environmental Protection Agency drinking water, EPA must determine FR—Federal Register not publicly available, e.g., Confidential HRL—health reference level that it meets three criteria: (1) The Business Information or other kg—kilogram contaminant may have an adverse effect information whose disclosure is L—liter on the health of persons; (2) the restricted by statute. Certain other MCL—maximum contaminant level contaminant is known to occur or there material, such as copyrighted material, MRL—Minimum Reporting Limit is a substantial likelihood that the

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contaminant will occur in public water additional approaches to analyzing data mandated by the 1996 SDWA systems with a frequency and at levels related to EPA’s perchlorate regulatory Amendments. Specifically, EPA has of public health concern; and (3) in the determination. These additional found that perchlorate may have an sole judgment of the Administrator, comments were sought in an effort to adverse effect on the health of persons, regulation of such contaminant presents ensure consideration of all potential that perchlorate occurs or there is a a meaningful opportunity for health risk options for evaluating whether there is substantial likelihood that perchlorate reduction for persons served by public a meaningful opportunity for human will occur in public water systems with water systems. Once EPA makes a health risk reduction of perchlorate a frequency and at levels of public determination to regulate a contaminant through a NPDWR. EPA stated that the health concern, and that regulation of in drinking water, SDWA requires that alternative analyses presented in this perchlorate in drinking water systems EPA issue a proposed NPDWR within notice could lead the Agency to make a presents a meaningful opportunity for 24 months and a final NPDWR within determination to regulate perchlorate. health risk reduction for persons served 18 months of proposal. EPA received over 6,000 comments on by public water systems. EPA included perchlorate on the first, the August 2009 notice. second, and third CCLs that were EPA has evaluated the approximately A. May perchlorate have an adverse published in the Federal Register on 39,000 public comments received on the effect on the health of persons? March 2, 1998 (63 FR 10273; USEPA May 2007 document, the October 2008 Yes. The perchlorate anion is 1998), February 24, 2005 (70 FR 9071; notice, and August 2009 notice. EPA has biologically significant specifically with USEPA 2005a), and October 8, 2009 (74 prepared a response to comment respect to the functioning of the thyroid FR 51850; USEPA 2009a), respectively. document that addresses the comments gland. Perchlorate can interfere with the On May 1, 2007, EPA published an related to the perchlorate regulatory normal functioning of the thyroid gland update on the Agency’s evaluation of determination (USEPA, 2010a). This by inhibiting the transport of iodide into perchlorate as part of the preliminary response to public comment document, the thyroid, resulting in a deficiency of regulatory determination for 11 other the public comments on the August iodide in the thyroid. Perchlorate CCL 2 contaminants (72 FR 24016; 2009 notice, and supporting materials inhibits (or blocks) iodide transport into USEPA 2007). The Agency did not make are available electronically at http:// the thyroid by chemically competing a preliminary determination for www.regulations.gov (Docket ID No. with iodide, which has a similar shape perchlorate as part of this regulatory EPA–HQ–OW–2009–0297). and electric charge. The transfer of determination, but requested public iodide from the blood into the thyroid C. What is EPA’s final regulatory comment on the options that the Agency is an essential step in the synthesis of determination on perchlorate and what was evaluating for perchlorate and thyroid hormones. The thyroid happens next? requested information that could assist hormones play an important role in the the Agency in its regulatory After careful review and regulation of metabolic processes determination. EPA received eight consideration of public comments on throughout the body and are also critical comment letters in response to the May the May 2007, October 2008, and to developing fetuses and infants, 2007 document (72 FR 24016; USEPA August 2009 notices, the Agency has especially with respect to brain 2007) that addressed perchlorate. Public made a determination to regulate development. Because the developing comments on the May 2007 document perchlorate in drinking water. EPA has fetus depends on an adequate supply of can be found online at http:// found that perchlorate may have an maternal thyroid hormone for its central www.regulations.gov (Docket ID No. adverse effect on human health. EPA nervous system development during the EPA–HQ–OW–2007–0068). has reversed its October 2008 first and second trimester of pregnancy, On October 10, 2008, EPA published preliminary determination not to iodide uptake inhibition from low-level a preliminary regulatory determination develop an NPDWR for perchlorate and perchlorate exposure has been for perchlorate (73 FR 60262; USEPA now concludes, based on the analysis identified as a concern in connection 2008a), requesting public comment on presented in this regulatory with increasing risk of its determination that perchlorate did determination, that there is a substantial neurodevelopmental impairment in not occur with a frequency and at levels likelihood that perchlorate will occur in fetuses of hypothyroid mothers. Poor of public health concern and regulation public water systems with a frequency iodide uptake and subsequent of perchlorate did not present a and at levels of public health concern. impairment of the thyroid function in meaningful opportunity for health risk Finally, EPA has determined that pregnant and lactating women have reduction for persons served by public regulation of perchlorate presents a been linked to delayed development water systems (the second and third meaningful opportunity to reduce and decreased learning capability in criteria for regulating a contaminant health risk for persons served by public their infants and children (NRC, 2005). under SDWA). The October 2008 notice water systems. Additionally, deficiency during describes in detail EPA’s basis for its EPA is initiating the development of childhood reduces child growth and preliminary determination not to a proposed NPDWR for perchlorate. cognitive motor function (Zimmerman, develop an NPDWR for perchlorate (73 EPA intends to publish a proposed 2009). Therefore, EPA finds that FR 60262; USEPA 2008a). The Agency regulation and analyses required by perchlorate may have an adverse effect received nearly 33,000 comment letters SDWA for public review and comment on the health of persons. on the October 2008 notice. Public within 24 months of this regulatory B. Is perchlorate known to occur or is comments on the October 2008 notice determination. EPA will consider the there a substantial likelihood that and supporting materials are available public comments and expects to perchlorate will occur in public water electronically at http:// promulgate a final regulation within systems with a frequency and at levels www.regulations.gov (Docket ID No. 18 months of the proposal. EPA–HQ–OW–2008–0692). of public health concern? On August 19, 2009, EPA published III. Final Regulatory Determination for Yes. EPA has determined that the Perchlorate Supplemental Request Perchlorate perchlorate occurs or there is a for Comments (74 FR 41883; USEPA In making final regulatory substantial likelihood that perchlorate 2009b) requesting comment on determinations, EPA uses the criteria will occur with a frequency and at

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levels of health concern in public water They viewed this as conservative and 90th percentile dietary intake estimate), systems. EPA has made this protective of health given that the NOEL but who consume equal or more water determination by comparing the best is based on a non-adverse effect (iodide on a per body weight basis than 90 available data on the occurrence of uptake inhibition), which precedes the percent of their cohorts. EPA is perchlorate in PWSs to potential health adverse effect in a continuum of evaluating these potential alternative reference levels (HRLs) for perchlorate. possible effects of perchlorate exposure. HRLs and considers them to be levels of HRLs are not final determinations about The NRC also noted that ‘‘any decrease public health concern for purposes of the level of a contaminant in drinking (in thyroid hormone) is potentially more this determination. EPA has compared water that is necessary to protect any likely to have adverse effects in these values to the data provided by particular population. Rather they are sensitive populations (people with PWSs subject to the first Unregulated benchmarks against which EPA thyroid disorders, pregnant women, Contaminant Monitoring Rule (UCMR compares the concentration of a fetuses, and infants). EPA’s Integrated 1). EPA collected and analyzed drinking contaminant found in public water Risk Information System (IRIS) adopted water occurrence data for perchlorate systems to determine if it is at levels of the NRC’s recommendations resulting in from 3,865 PWSs between 2001 and public health concern. an RfD of 0.7 μg/kg/day (USEPA, 2005 under the UCMR 1. The minimum In January 2005, the National 2005b). reporting level (MRL) for perchlorate Research Council (NRC) published In the October 2008 preliminary under the UCMR 1 was 4 μg/L. ‘‘Health Implications of Perchlorate regulatory determination, EPA had EPA found that 160 (approximately Ingestion,’’ a review of the state of the derived a single HRL of 15 μg/L based 4.1 percent) of the 3,865 PWSs that science regarding potential adverse upon the RfD, an estimate of perchlorate sampled and reported had at least 1 health effects of perchlorate exposure exposure from food for pregnant analytical detection of perchlorate (in at and mode of action for perchlorate women, and traditional adult body least 1 sampling point) at levels greater toxicity (NRC, 2005). The NRC weight (70 kg) and drinking water than or equal to the MRL of 4 μg/L. recommended that EPA use data from consumption (2 L/day) values. This These 160 PWSs are located in 26 States the Greer et al. (2002) human clinical single HRL was derived to reflect and 2 territories. Of these 160 PWSs, 8 study as the basis for deriving a exposure to a pregnant woman and her are systems serving 10,000 or fewer reference dose for perchlorate (NRC, fetus, which the NRC identified as ‘‘the people and 152 are systems serving 2005). Although the NRC committee most sensitive population.’’ more than 10,000 people. These 160 concluded that hypothyroidism is the Since the NRC also identified infants systems reported 637 detections of first adverse effect in the continuum of and developing children as additional perchlorate at levels greater than or effects of perchlorate exposure, NRC life stages, EPA derived potential equal to 4 μg/L, which is approximately recommended that ‘‘the most health- alternative HRLs for 14 life stages (age 11.3 percent of the 5,629 samples protective and scientifically valid groups) using the RfD and life stage- collected by these 160 PWSs and approach’’ was to base the perchlorate specific exposure information in the approximately 1.9 percent of the 34,331 RfD on the inhibition of iodide uptake August 9, 2009, notice (74 FR 41883; samples collected by all 3,865 PWSs. by the thyroid, which the NRC USEPA 2009b). These levels range from The average concentration of considered a non-adverse effect (NRC, 1 μg/L to 47 μg/L and are the perchlorate for those samples with 2005). The NRC recommended that EPA concentrations of perchlorate in positive detections for perchlorate was apply an intraspecies uncertainty factor drinking water that may result in total 9.85 μg/L and the median concentration of 10 to the no observed effect level perchlorate exposures (from food and was 6.40 μg/L. (NOEL),1 to account for differences in water) greater than the RfD for Table 1 presents the number and sensitivity between the healthy adults in individuals at each life stage. These percentage of PWSs that reported the Greer et al., (2002) study and the HRLs are calculated based on perchlorate at levels exceeding various most sensitive population, fetuses of individuals who consume an average threshold concentrations. Note that the pregnant women who might have amount of perchlorate from food (except MRL for perchlorate under the UCMR 1 hypothyroidism or iodide deficiency. for pregnant women where EPA used a was 4 μg/L.

TABLE 1—PERCENT PUBLIC WATER SYSTEM ESTIMATES FOR PERCHLORATE ABOVE THRESHOLDS OF INTEREST

PWS entry or sample points a PWSs with at least 1 detection Threshold concentration > threshold of interest with at least 1 detection > threshold of interest b

4 μg/L ...... 4.0% 2.5% (155 of 3,865) (371 of 14,987) 6 μg/L ...... 2.5% 1.5% (97 of 3,865) (219 of 14,987) 9 μg/L ...... 1.5% 0.77% (56 of 3,865) (115 of 14,987) 13 μg/L ...... 0.93% 0.37% (36 of 3,865) (56 of 14,987) 14 μg/L ...... 0.85% 0.32% (33 of 3,865) (48 of 14,987) 19 μg/L ...... 0.62% 0.20% (24 of 3,865) (30 of 14,987)

1 No observed effect level (NOEL)—an exposure biologically significant increases in the frequency or severity of any effect between the exposed level at which there are no statistically or population and its appropriate control.

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TABLE 1—PERCENT PUBLIC WATER SYSTEM ESTIMATES FOR PERCHLORATE ABOVE THRESHOLDS OF INTEREST— Continued

PWS entry or sample points a PWSs with at least 1 detection Threshold concentration > threshold of interest with at least 1 detection > threshold of interest b

23 μg/L ...... 0.39% 0.13% (15 of 3,865) (19 of 14,987) a All occurrence measures in this table were conducted on a basis reflecting values greater than the listed thresholds. Five systems detected perchlorate levels equal to 4 μg/L and are therefore not presented in this table.

Given the range of potential population estimates were derived using TABLE 2—POPULATION ESTIMATES alternative HRLs, EPA has reversed its the UCMR 1 monitoring data. The high FOR PWSS THAT DETECTED PER- October 2008 preliminary determination end estimate of the population served CHLORATE ABOVE VARIOUS THRESH- not to regulate perchlorate in drinking drinking water above a threshold is OLDS water. Based on the data in Table 1 and derived by adding the entire system the range of potential alternative HRLs, population of all PWSs in which at least Range of population EPA has determined that perchlorate is one sample was found to contain served by PWSs with at known to occur or there is a substantial Threshold a least 1 detection perchlorate above the threshold. EPA b likelihood that it will occur with a > threshold considers this a high end estimate (million) frequency and at levels of public health because it is based on the assumption concern. that the entire system population is 4 μg/L ...... 5.1–16.6 μ C. Is there a meaningful opportunity for served water from the entry point that 6 g/L ...... 3.0–11.8 9 μg/L ...... 1.6–5.2 the reduction of health risks from had the highest reported perchlorate 14 μg/L ...... 0.9–2.1 perchlorate for persons served by public concentration. In fact, many PWSs have 19 μg/L ...... 0.7–1.6 water systems? multiple entry points into which treated 23 μg/L ...... 0.4–1.0 water is pumped for distribution to their Yes. EPA has made this determination a All occurrence measures in this table were based on a consideration of the best consumers. For the PWSs with multiple conducted on a basis reflecting values greater available peer reviewed science and entry points, it is unlikely that the entire than the listed thresholds. All population esti- data collected in accordance with service population receives water from mates in this table are rounded. b Population estimates are derived from accepted methods related to perchlorate the one entry point with the highest UCMR 1 data. occurrence in drinking water, the single concentration. Therefore, EPA presence of perchlorate in foods, and also provides a central value estimate of D. Regulatory Determination the potential health effects of exposure the population served water with EPA has determined that perchlorate to perchlorate. perchlorate above a threshold in the meets the criteria for regulating a Table 2 presents EPA’s estimates of second column in Table 2. EPA contaminant in Section 1412(b)(1)(A) of the population served by PWSs that developed this central value estimate by SDWA. As previously discussed in this were monitored under UCMR 1 for assuming the population was equally regulatory determination, perchlorate which the highest reported perchlorate distributed among all entry points and may have an adverse effect on the health concentration was greater than the added only the proportion of the total of persons and perchlorate is known to thresholds identified in Table 1. EPA population served by those entry points occur or there is a substantial likelihood has determined that a NPDWR for in a PWS that had at least one sample that perchlorate will occur in public perchlorate could reduce perchlorate with perchlorate concentrations greater water systems with a frequency and at exposures for these populations to than the threshold. For example, if a levels of public health concern. levels below the potential alternative PWS with 10 entry points serving Moreover, in light of the discussion in HRLs that EPA has identified as levels 200,000 people had a sample from a this regulatory determination and the of public health concerns for purposes single entry point with a concentration information available at this time, the of this determination, and that such at or above a given threshold, EPA Administrator finds that regulation of exposure reductions present a perchlorate in drinking water systems assumed that the entry point served meaningful opportunity for the presents a meaningful opportunity for one-tenth of the PWS population, and reduction of health risks for persons health risk reduction for persons served added 20,000 people to the total when served by PWSs. by public water systems. Therefore, EPA Specifically, Table 2 presents EPA’s deriving the central value population will initiate the process of proposing a estimates of the population served by estimate. In contrast, for the high end NPDWR for perchlorate. PWSs that were monitored under UCMR estimate using the example above, EPA 1 for which the highest reported added the entire PWS population of E. Key Commenter Issues perchlorate concentration was greater 200,000 to the total population. The EPA received a total of approximately than the thresholds identified in Table latter is likely an overestimate. The 39,000 comments from individuals or 1. The second column of Table 2 UCMR 1 population estimates in Table organizations on the May 2007 presents a range of estimates of the 2 are for people at all life stages. document, and the October 2008, and population served by PWSs that had at August 2009 Federal Register notices least one sample with perchlorate regarding the perchlorate regulatory concentrations greater than the determination. This section briefly threshold. The population range discusses a number of the key issues represents both a high end estimate, as raised by commenters and EPA’s well as a central value estimate. These response to these concerns. Responses

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to all of the comments received are that assesses and characterizes the persons served by PWSs contaminated available in the ‘‘Comment Response combined human health risk from by perchlorate. Document for the Final Regulatory perchlorate, nitrate, and thiocyanate. 4. Iodide Nutritional Status Determination on Perchlorate’’ (USEPA, While EPA acknowledges that nitrate 2010a) available at http:// and thiocyanate have the same mode of Some commenters stated that public www.regulations.gov (Docket ID No. action as perchlorate, and that the health concerns over iodide uptake EPA–HQ–OW–2009–0297). effects of combined exposure to inhibition could be addressed more perchlorate, nitrate, and thiocyanate are efficiently through promotion of iodide 1. Health Implications of Perchlorate additive, EPA does not believe there are nutrition than through regulation of Exposure Above the RfD sufficient scientific data currently perchlorate. EPA agrees that promoting EPA received comments indicating available to assess and characterize the iodide nutrition is good public health that the levels of perchlorate in drinking combined risk of these contaminants. policy and may have a positive water that result in exposures greater EPA has committed to a drinking water influence in reducing the iodide uptake than the RfD are not levels of public strategy that outlines four principles to inhibition effects associated with health concern because the RfD is based expand public health protection for exposure to perchlorate. However, the on a precursor to an adverse effect. EPA drinking water (USEPA, 2010b). One of Agency does not think it is appropriate believes the NRC appropriately based these principles is to address to rely on the promotion of iodide the RfD on iodide uptake inhibition to contaminants as groups. However, EPA nutrition in this case, especially since the thyroid, for the reasons discussed in does not believe that regulatory action these activities are outside of EPA’s its report. EPA also received a to address perchlorate should be further SDWA authority. As a result, while the substantial number of comments delayed. Therefore, EPA intends to health concerns associated with supporting the Agency’s current view. develop a proposed rule for perchlorate. perchlorate may be addressed through EPA notes that the data underlying the At such time as a NPDWR is other means, it is the Administrator’s definition of iodide uptake inhibition as promulgated, EPA is required to review judgment that a standard limiting a precursor effect and the relationship of and revise, as appropriate, its drinking perchlorate in drinking water can iodide uptake inhibition to the water standards at least every six years. reduce health risk, particularly to continuum of adverse outcomes reflects Any revision must at least maintain or fetuses, infants and children. an understanding of effects in adults; it improve public health protection. When 5. Physiologically-Based may not reflect the relationship of the there are sufficient scientific data to Pharmacokinetic (PBPK) Modeling precursor event to adverse outcomes in assess the cumulative risks of neonates and infants, who may not have perchlorate and other contaminants, EPA reviewed, modified, and applied iodide stores sufficient to offset the EPA will review this information to the perchlorate PBPK models, which effects of reduced iodide uptake. The evaluate whether any revisions of were originally developed by Merrill et less resilient neonatal and infant system NPDWRs are appropriate. al. (2005) for adults and Clewell et al. makes the exposure gap between a (2007) for other life stages, to estimate precursor event (iodide uptake 3. Perchlorate in Food the iodide uptake inhibition in the inhibition due to perchlorate) and A commenter wrote that a drinking thyroid for each life-stage (73 FR 60262; reduced T3/T4 levels likely to be water regulation for perchlorate does USEPA 2008a). Estimated ingestion narrower than for adults, and in fact, the not present a meaningful opportunity rates were then used to estimate the distinction between the two may be for health risk reduction because internal dose and resulting iodide blurred for the very young (Greer et al., perchlorate contamination in food is uptake inhibition for several life stages, 2002; Savin et al., 2003; van den Hove widespread. Other commenters including susceptible populations (e.g., et al., 1999). The NRC noted that, ‘‘[T]he indicated that EPA should regulate pregnant women and their fetuses, as minimal prolonged decrease in thyroid perchlorate in drinking water to reduce well as breast-fed and bottle-fed hormone production that would be the public’s overall exposure to infants). associated with adverse health effects is perchlorate. EPA agrees that perchlorate In the August 2009 notice, EPA stated not known; any decrease is potentially contamination is more widespread in that it was re-evaluating how best to more likely to have adverse effects in foods than in PWSs; however, EPA does incorporate the PBPK modeling analysis sensitive populations (people with not believe that the widespread into its evaluation of perchlorate—if at thyroid disorders, pregnant women, presence of perchlorate in food all. The Agency sought comments on fetuses, and infants) but data are not overrides the need for public health risk ways to use the PBPK modeling analysis available to determine the magnitude of reduction for persons served by PWSs to inform the regulatory determination. the decrease needed to cause adverse with perchlorate contamination. The Several commenters supported the effects in those populations.’’ Agency presented an extensive use of the PBPK model to inform the evaluation of dietary exposure to regulatory determination only if the 2. Other Thyroid Inhibiting Chemicals perchlorate in the October 2008 and significant limitations of the current EPA received a number of comments August 2009 notices (73 FR 60262; model are addressed. For example, the that the Agency should consider the USEPA 2008a and 74 FR 41883; USEPA inability of the model to reflect iodide comparative effect on iodine uptake of 2009b). EPA has used this dietary nutritional status was cited by perchlorate exposure in drinking water exposure data to account for the relative commenters and three of four peer to nitrate and thiocyanate exposure in source contribution (RSC) of perchlorate reviewers as an important limitation drinking water in determining whether from food to estimate the range of levels (USEPA, 2008d). Also, several there is a meaningful opportunity for of public health concern. EPA commenters stated that the risks to risk reduction. Other commenters, recognizes that a drinking water breast-fed infants and young children including EPA’s Office of Inspector regulation would not eliminate total are not adequately addressed by the General (USEPA, 2008c), believe that a perchlorate exposure, but believes that model. They challenged that the NPDWR for a group of chemicals may be the reduction in perchlorate exposure in modeling analysis is based on average appropriate based on a yet-to-be- drinking water presents a meaningful weight infants and healthy adults, while conducted cumulative risk assessment opportunity for health risk reduction for the sensitive life stages for perchlorate

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include premature infants and Toxicology and Environmental Health. USEPA. 2008c. Scientific Analysis of hypothyroid women. Part A. Vol. 70. Issue 5. p. 408–428. Perchlorate (External Review Draft). After further consideration of the peer Greer, M.A., G. Goodman, R.C. Pleuss, and Office of Inspector General, Washington, review and public comments, EPA S.E. Greer. 2002. Health effect DC; Assignment No. 2008–0010. concludes that the PBPK modeling assessment for environmental Available on the Internet at: http:// perchlorate contamination: The dose www.epa.gov/oig/reports/2010/ analysis, in the context of the response for inhibition of thyroidal 20100419-10-P-0101.pdf. perchlorate regulatory determination, is radioiodide uptake in humans. Environ USEPA. 2008d. Comment Response useful in examining which life stages Health Perspect Vol. 110. p. 927–937. Summary Report, Peer Review of are most susceptible to the effects of Life Sciences Research Office (LSRO), Drinking Water Health Advisory for perchlorate. For example, the model Federation of American Studies for Perchlorate. Office of Science and indicates that a fetus may be seven Experimental Biology Prepared for the Technology, Washington, DC; December times more sensitive to the effects of Interagency Board for Nutrition 2008. perchlorate than a pregnant woman. The Monitoring and Related Research. 1995. USEPA. 2008e. Interim Drinking Water Third Report on Nutrition Monitoring in Health Advisory for Perchlorate. Office model also allows for the estimation of the United States: Volume 1. U.S. the concentration of perchlorate in of Science and Technology, Washington, Government Printing Office, DC; EPA 822–R–08–025. breast milk (thus breast-fed infant Washington, DC. USEPA. 2009a. Drinking Water Contaminant exposure) at various maternal Merrill, E.A., R.A. Clewell, P.J. Robinson, Candidate List 3—Final. Federal perchlorate exposure levels. However, A.M. Jarabek, T.R. Sterner, and J.W. Register. Vol. 74, No. 194. p. 51850, because of the stated limitations, EPA Fisher. 2005. PBPK model for radioactive October 8, 2009. iodide and perchlorate kinetics and has decided the model does not directly USEPA. 2009b. Drinking Water: Perchlorate perchlorate-induced inhibition of iodide Supplemental Request for Comments, bear on the current decision regarding uptake in humans. Toxicological Federal Register, Vol. 74, No. 159. p. the need for a NPDWR for perchlorate. Sciences. Vol. 83. p. 25–43. 41883, August 19, 2009. EPA is continuing to evaluate whether National Research Council (NRC). 2005. the model could be used in setting a Health Implications of Perchlorate USEPA. 2010a. Comment Response NPDWR for perchlorate. Ingestion. National Academies Press, Document for the Final Regulatory Board on Environmental Studies and Determination on Perchlorate F. Next Steps Toxicology. January 2005. p. 276. (Categorized Public Comments). EPA XXX–XXX. December, 2010. EPA is initiating the development of Savin, S., D. Dvejic, O. Nedic, R. Radosavljevic. 2003. Thyroid Hormone USEPA. 2010b. A New Approach to a proposed NPDWR for perchlorate. Protecting Drinking Water and Public However, this is not the end of a Synthesis and Storage in the Thyroid Gland of Human Neonates. J. Pediatric Health. EPA 815–F–10–001. Available on decision process but a middle step in a Endocrinology & Metabolism. Vol. 16. p. the Internet at: http://water.epa.gov/ process that leads to a final drinking 521–528. lawsregs/rulesregs/sdwa/dwstrategy/ water standard. Based on this decision, U.S. Census Bureau. 2008. U.S. Census index.cfm EPA intends to publish a proposed Bureau Annual Estimates of Resident van den Hove, M.F., C. Beckers, H. Devlieger, NPDWR for public review and comment Population by Single-Year of Age and F. de Zegher, P. De Nayer. 1999. within 24 months of this regulatory Sex for the U.S. and States: April 2, 2000 Hormone synthesis and storage in the determination.2 EPA will continue to to July 1, 2008. Available on the Internet thyroid of human preterm and term newborns: Effect of thyroxine treatment. evaluate the science as we develop the at: http://www.census.gov/popest/states/ asrh/. Biochimie. Vol. 81. p. 563–570. proposed NPDWR. EPA will, as part of USEPA. 1998. Announcement of the Zimmerman, M. 2009. Iodide Deficiency. the proposed NPDWR, present a health Drinking Water Contaminant Candidate Endocrine Reviews. Vol. 30, No. 4. p. risk reduction and cost analyses, an List; Notice. Federal Register. Vol. 63, 376–408. analysis of feasible treatment methods, No. 40. p. 10273, March 2, 1998. Dated: February 2, 2011. and an analysis of small system USEPA. 2004. Estimated Per Capita Water Lisa P. Jackson, compliance technologies. EPA will also Ingestion and Body Weight in the United consult with the National Drinking States—An Update. Office of Science Administrator. Water Advisory Council, the Science and Technology, Washington, DC; [FR Doc. 2011–2603 Filed 2–10–11; 8:45 am] EPA/822/R–00–001. BILLING CODE 6560–50–P Advisory Board, and the Secretary of USEPA. 2005a. Drinking Water Contaminant Health and Human Services, as required Candidate List 2; Final Notice. Federal under SDWA. Register. Vol. 70, No. 36. p. 9071, DEPARTMENT OF HEALTH AND IV. References February 24, 2005. USEPA. 2005b. ‘‘Integrated Risk Information HUMAN SERVICES Clewell, R.A., E.A. Merrill, J.M. Gearhart, P.J. System (IRIS), Perchlorate and Robinson, T.R. Sterner, D.R. Mattie, and Perchlorate Salts.’’ February 2005. 45 CFR Parts 144 and 147 H.J. Clewell, III. 2007. Perchlorate and Available on the Internet at: http:// [CMS–9981–P] radioiodide kinetics across life stages in www.epa.gov/iris/subst/1007.htm. the human: Using PBPK models to Accessed February 2, 2005. RIN 0950–AA20 predict dosimetry and thyroid inhibition USEPA. 2007. Drinking Water: Regulatory and sensitive subpopulations based on Determinations Regarding Contaminants Student Health Insurance Coverage developmental stage. Journal of on the Second Drinking Water Contaminant Candidate List— AGENCY: Centers for Medicare & 2 On January 8, 2009, EPA issued an interim Preliminary Determinations, Federal Medicaid Services (CMS), HHS. health advisory to provide guidance to State and Register, Vol. 72, No. 83. p. 24016, May ACTION: Proposed rule. local officials in their efforts to address perchlorate 1, 2007. contamination. The interim health advisory USEPA. 2008a. Drinking Water: Preliminary SUMMARY: (USEPA, 2008e) can be found at: http:// This document contains a Regulatory Determination on proposed regulation that would www.epa.gov/safewater/contaminants/unregulated/ Perchlorate, Federal Register, Vol. 73, pdfs/healthadvisory_perchlorate_interim.pdf and in No. 198. p. 60262, October 10, 2008. establish rules for student health EPA’s docket ID No. EPA–HQ–OW–2009–0297 for insurance coverage under the Public this notice. EPA expects to make a final decision USEPA. 2008b. Child-Specific Exposure on the interim health advisory at such time as a Factors Handbook. National Center for Health Service Act and the Affordable definitive decision has been made with respect to Environmental Assessment, Washington, Care Act. The proposed rule would the promulgation of a final perchlorate regulation. DC; EPA/600/R–06/096F. define ‘‘student health insurance

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