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### January 28, 2011

Page 1 of 35 ENVIRONMENTAL PROTECTION AGENCY

[EPA
- HQ
- OW
- 2008
- 0692, EPA
- HQ
- OW
- 2009
- 0297; FRL
-

_______ - _______] RIN 2040
- AF08 Drinking Water: Final Regulatory Determination on Perchlorate AGENCY: Environmental Protection Agency (EPA). ACTION: Notice.

SUMMARY: This action presents EPA‘s (or the Agency‘s) final regulatory determination for perchlorate in accordance with the Safe Drinking Water Act (SDWA). Specifically, EPA has determined that perchlorate meets SDWA‘s criteria for regulating a contaminant

— that is, perchlorate may have an adverse effect on the health of persons; perchlorate is known to occur or there is a substantial likelihood that perchlorate will occur in public water systems with a frequency and at levels of public health concern; and in the sole judgment of the Administrator, regulation of perchlorate in drinking water systems presents a meaningful opportunity for health risk reduction for persons served by public water systems. Therefore, EPA will initiate the process of proposing a nation al primary drinking water regulation (NPDWR) for perchlorate.

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### January 28, 2011

Page 2 of 35 DATES: For purposes of judicial review, the regulatory determination in this notice is issued as of [INSERT DATE OF PUBLICATION IN THE FEDERAL REGISTER], as provided in
40 CFR 23.7.

ADDRE SSES: EPA has established dockets for this action under Docket ID numbers EPA

– HQ

– OW

– 2008

– 0692 and EPA

– HQ

– OW

– 2009

– 0297 . All documents in these dockets are listed on the http://www.regulations.gov Web site. Although listed in the index, some information is not publicly available, e.g., Confidential Business Information or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not place d on the Internet, but will be publicly available in hard copy form. Publicly available docket materials are available either electronically through http://www.regulations.gov or in hard copy at the Water Docket, EPA/DC, EPA West, Room 3334, 1301 Constitu tion Ave., NW, Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone number for the Public Reading Room is (202) 566

– 1744, and the telephone number for the EPA Docket C enter is (202) 566

– 2426.

FOR FURTHER INFORMATION CONTACT: Eric Burneson, Office of Ground Water and Drinking Water, Standards and Risk Management Division, at (202) 564

- 5250 or e - mail burneson.eric@epa.gov . For general information contact the EPA Safe Drinking Water Hotline at (800) 426

- 4791 or e

- mail: hotline

- sdwa@epa.gov hotline

- sdwa@epa.gov

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Page 3 of 35 Table of Contents I. General Information Does this Action Impose Any Requirements on My Public Water System? II. Background A. What is the Purpose of This Action? B. Background on Perchlorate Regulatory Determinations C. What is EPA’s Final Regulatory Determination on Perchlorate and What Happens Next? III. Final Regulatory Determination for Perchlorate A. May Perchlorate Have an Adverse Effect on the Health of Persons? B. Is Perchlorate Known to Occur or is There a Substantial Likelihood that Perchlorate Occurs with a Frequency and at Levels of Public Health Concern in Public Water Systems? C. Is There a Meaningful Opportunity for the Reduction of Health Risks from Perchlorate for Persons Served by Public Water Systems? D. Regulatory Determination E. Key Commenter Issues 1. Health Implications of Perchlorate Exposure above the RfD 2. Other Thyroid Inhibiting Chemicals 3. Perchlorate in Food 4. Iodide Nutritional Status Formatted: Default Paragraph Font, Font: Times New Roman, 12 pt, Bold, Do not check spelling or grammar Field Code Changed Formatted: Default Paragraph Font, Font: Times New Roman, 12 pt, Italic, Do not check spelling or grammar Field Code Changed Formatted: Default Paragraph Font, Font: Times New Roman, 12 pt, Bold, Do not check spelling or grammar Field Code Changed Formatted: Default Paragraph Font, Font: Times New Roman, 12 pt, Italic, Do not check spelling or grammar Field Code Changed Formatted: Default Paragraph Font, Font: Times New Roman, 12 pt, Italic, Do not check spelling or grammar Field Code Changed Formatted: Default Paragraph Font, Font: Times New Roman, 12 pt, Italic, Do not check spelling or grammar Field Code Changed Formatted: Default Paragraph Font, Font: Times New Roman, 12 pt, Bold, Do not check spelling or grammar Field Code Changed Formatted

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### January 28, 2011

Page 4 of 35 5. Physiologically

- Based Pharmacokinetic (PBPK) Modeling F. Next Steps

IV. References

Abbreviations and Acronyms CBI

— confidential business information
CCL

— Contaminant Candidate List
EPA

— U.S. Environmental Protection Agency
FR

— Federal Register
HRL

— health reference level kg

— kilogram
L

— liter
MCL

— maximum contaminant level
MRL

— M inimum Reporting Limit
NOEL

— no observed effect level
NPDWR

— N ational Primary Drinking Water Regulation
NRC

— National Research Council
PBPK

— Physiologically

- Based Pharmacokinetic
PWS

— public water system Formatted: Default Paragraph Font, Font: Times New Roman, 12 pt Field Code Changed Formatted: Default Paragraph Font, Font: Times New Roman, 12 pt, Italic, Do not check spelling or grammar Field Code Changed Formatted: Font: Times New Roman, 12 pt, Italic, No underline, Font color: Auto, Do not check spelling or grammar

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### January 28, 2011

Page 5 of 35 RfD

— reference dose
SDWA

— Safe Drinking Water Act
UCMR

— Unregulated Contaminant Monitoring R ule
μg

— microgram (one

- millionth of a gram)
U

. S

. — United States

SUPPLEMENTARY INFORMATION I. General Information

Does this Action Impose Any Requirements on My Pub lic Water System?

Today‘s action notifies interested parties of EPA‘s determination to regulate perchlorate,
but imposes no requirements on public water systems (PWSs)

. However, t his action also initiates the process to develop a national primary drinki ng water regulation (NPDWR) for perchlorate

. At such time as the Agency establishes an NPDWR, certain PWSs will be required to take action to comply with the regulation in accordance with the schedule specified in the regulation.

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Page 6 of 35 II. Background

A. What is the Purpose of This Action?

The purpose of today‘s action is to present EPA‘s final determination to regulate perchlorate in drinking water, the rationale EPA used to make this regulatory determination, and EPA‘s response to certain key issues raised by commenters on previous Federal Register (FR) notices on the drinking water regulatory determination for perchlorate. (All comments are addressed in a Response to Comments document that is available in EPA‘s docket ID No. EPA

HQ

- OW

- 2009

- 0297 for this notice.)

B. Background on Perchlorate Regulatory Determinations

The statutory and regulatory background for this action is described in detail in the October 10, 2008, FR notice discussing EPA‘s preliminary regulatory det ermination for perchlorate (73 FR 60262; USEPA 2008a ). Briefly, SDWA section 1412 (b)(1)(A) , as amended in 1996, requires EPA to make a determination whether to regulate at least five contaminants from its C ontaminant C andidate L ist (CCL) every five years. To regulate a contaminant in drinking water, EPA must determine that it meets three criteria: 1) t he contaminant may have an

a dverse effect on the health of persons; 2) the contaminant is known to occur or there is a

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### January 28, 2011

Page 7 of 35 substantial likelihood that the contami nant will occur in public water systems with a frequency and at levels of public health concern; and 3) in the sole judgment of the Administrator, regulation of such contaminant presents a meaningful opportunity for health risk reduction for persons served by public water systems. Once EPA makes a determination to regulate a contaminant in drinking water, SDWA requires that EPA issue a proposed NPDWR within 24 months and a final NPDWR within 18 months of proposal

. EPA included perchlorate on the first, s econd, and third CCLs that were published in the Federal Register on March 2, 1998 (63 FR 10273; USEPA 1998), February 24, 2005 (70 FR 9071; USEPA 2005a), and October 8, 2009 (74 FR 51850; USEPA 2009a), respectively

. On May 1, 2007, EPA published an updat e on the Agency's evaluation of perchlorate as part of the preliminary regulatory determination for 11 other CCL 2 contaminants (72 FR 24016; USEPA 2007). The Agency did not make a preliminary determination for perchlorate as part of this notice, but requ ested public comment on the options that the Agency was evaluating for perchlorate and requested information that could assist the Agency in its regulatory determination. EPA received eight comment letters in response to the May 2007 notice (72 FR 24016; USEPA 2007) that addressed perchlorate. Public comments on the May 2007 notice can be found online at http://www.regulations.gov (Docket ID No. EPA

- HQ

- OW

- 2007

- 0068). On October 10, 2008, EPA published a preliminary regulatory determination for perchlora te (73 FR 60262; USEPA 2008a) , requesting public comment on its determination that perchlorate did not occur with a frequency and at levels of public health concern and regulation Formatted: No underline, Font color: Auto

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### January 28, 2011

Page 8 of 35 of perchlorate did not present a meaningful opportunity for health risk redu ction for persons served by public water systems ( the second and third criteria for regulati ng a contaminant under SDWA)

. The October 2008 notice describes in detail EPA‘s basis for its preliminary
determination not to develop an NPDWR for perchlorate ( 73 FR 60262; USEPA 2008a ). The Agency received nearly 3 3 , 000 comment letters on the October 2008 notice

. P ublic comments on the October 2008 notice and supporting materials are available electronically at http://www.regulations.gov (Docket ID No. EPA

– HQ

– OW

– 2008

– 0692). On August 19, 2009, EPA published the Perchlorate Supplemental Request for
Comments (74 FR 41883; USEPA 2009b) requesting comment on additional approaches to analyzing data related to EPA‘s perchlorate regulatory determination. The se additional comments were sought in an effort to ensure consideration of all potential options for evaluating whether there is a meaningful opportunity for human health risk reduction of perchlorate through a NPDWR. EPA stated that the alternative analy ses presented in this notice could lead the Agency to make a determination to regulate perchlorate. EPA received over 6,000 comments on the August 2009 notice. EPA has evaluated the approximately 39,000 public comments received on the May 2007 notice, the October 2008 notice, and August 2009 notice. EPA has prepared a response to comment document that addresses the comments related to the perchlorate regulatory determination (USEPA, 2010a). This response to public comment document, the p ublic Formatted: No underline

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### January 28, 2011

Page 9 of 35 comments on the August 2009 notice, and supporting materials are available electronically at http://www.regulations.gov (Docket ID No. EPA

– HQ

– OW

– 2009

– 0297).

C. What is EPA’s Final Regulatory Determination on Perchlorate and What Happens Next?

After careful review and consideration of public comments on the May 2007, October 2008, and August 2009 notices , the Agency has made a determination to regulate perchlorate in drinking water. EPA has found that perchlorate may have an adverse effect on human health. EPA has reversed its October 2008 preliminary determination not to develop an NPDWR for perchlorate based on our August 2009 evaluation of infants and developing children and now concludes , based on the analysis presented in this notice, that there is a substantial likelihood that perchlorate will occur in public water systems with a frequency and at levels of public health concern. Finally, EPA has determined that regulation of perchlorate presents a meaningful opportunity to reduce health risk for persons served by public water systems. EPA is initiating the development of a proposed NPDWR for perchlorate. EPA intends to publish a proposed regulation and analyses required by SDWA for public rev iew and comment within 24 months of this notice. EPA will consider the public comments and expects to promulgate a final regulation within 18 months of the proposal.

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Page 10 of 35 III. Final Regulatory Determination for Perchlorate

In making final regulatory determ inations, EPA uses the criteria mandated by the 1996 SDWA Amendments. Specifically, EPA has found that perchlorate may have an adverse effect on the health of persons, that perchlorate occurs or there is a substantial likelihood that perchlorate will occu r in public water systems with a frequency and at levels of public health concern, and that regulation of perchlorate in drinking water systems presents a meaningful opportunity for health risk reduction for persons served by public water systems.

A. May Perchlorate Have an Adverse Effect on the Health of Persons?

Yes. The perchlorate anion is biologically significant specifically with respect to the functioning of the thyroid gland

. Perchlorate can interfere with the normal functioning of the thyroid gland by inhibiting the transport of iodide into the thyroid , resulting in a deficiency of iodide in the thyroid. Perchlorate inhibits (or blocks) iodide transport into the thyroid by chemically competing with iodide, which has a similar shape an d electric charge. T he transfer of iodide from the blood into the thyroid is an essential ste p in the synthesis of thyroid hormones. The thyroid hormones play an important role in the regulation of metabolic processes throughout the body and are also cri tical to developing fetus es and infant s, especially with respect to brain development. Because the developing fetus depends on an adequate supply of maternal thyroid

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Page 11 of 35 hormone for its central nervous system development during the first and second trimester of pregnancy, iodide uptake inhibition from low

- level perchlorate exposure has been identified as a concern in connection with increasing risk of neurodevelopmental impairment in fetuses of hypothyroid mothers. Poor iodide uptake and subsequent impairment of the thyroid function in pregnant and lactating women have been linked to delayed development and decreased learning capability in their infants and children ( NRC, 2005). Additionally, deficiency during childhood reduces child growth and cognitive moto r function (Zimmerman, 2009) . Therefore, EPA finds that perchlorate has may have an adverse effect on the health of persons.

B. Is Perchlorate Known to Occur or is T here a Substantial Likelihood that Perchlorate
Occurs w ill Occur in Public Water Systems with a Frequency and at Leve ls of Public Health
Concern in Public Water Systems ?

Yes

. EPA has determined that perchlorate occurs or there is a substantial likelihood that perchlorate will occur with a frequency and at levels of health concern in public w ater systems. EPA has made this determination by comparing the best available data on the occurrence of perchlorate in PWSs to health reference levels (HRLs) based on the reference dose ( RfD ) for perchlorate

. potential health reference levels (HRLs) for perchlorate. HRLs are not final determinations about the level of a contaminant in drinking water that is necessary to protect any particular population. Rather they are benchmarks against which EPA compares the

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### January 28, 2011

Page 12 of 35 concentration of a contaminant found in public water systems to determine if it is at levels of public health concern. In January 2005, the National Research Council ( NRC ) published ― Health Implications of Perchlorate Ingestion, ‖ a review of the state of the science regarding potential adverse health effects of perchlorate exposure and mode of action for perchlorate toxicity (NRC, 2005). The NRC recommended that EPA use data from the Greer et al. (2002) human clinical study as the basis for deriving a reference dose for perchlorate (NRC, 2005)

. Although the NRC committee concluded that hypothyroidism is the first adverse effect in the continuum of effects of perchlorate exposure, NRC recommended that ― the most health

- protective and scientifically valid approach‖ was to base the perchlorate RfD on the inhibition of iodide uptake by the thyroid , which the NRC considered a non

- adverse effect (NRC, 2005) . T he NRC recommended that EPA apply an intraspecies uncertainty factor of 10 to the no observed effect level (NOEL ) 1
, t o account for differences in sensitivity between the healthy adults in the Greer et al., (2002) study and the most sensitive population, fetuses of pregnant women who might have hypothyroid ism or iodide deficien cy . They viewed this as conservative and protective of health given th at the NOEL is based on a non

- adverse effect (iodide uptake inhibition), which precedes the adverse effect in a continuum of possible effects of perchlorate exposure. The NRC also noted that ―any decrease (in thyroid hormone) is potentially more likely to have adverse effects in sensitive populations (people with thyroid disorders, pregnant women, fetuses, and infants).

.

1 No observed effect level (NOEL)

- an exposure level at which there are no statistically or biologically significant increases in the frequency or severity of any effect between the exposed population and its appropriate control.

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Page 13 of 35 . ‖ EPA‘s Inte grated Risk Information System (IRIS) adopted the NRC‘s recommendations resulting in an RfD of 0.7 μg/kg/day (USEPA, 2005 b ). In the October 2008 preliminary regulatory determination, EPA had derived a single HRL of 15 μg/L based upon the RfD, an estimate of perchlorate exposure from food for pregnant women, and traditional adult body weight (70 kg) and drinking water consumpt ion (2 L/day) values. This single HRL was derived to reflect exposure to a pregnant woman and her fetus, which the NRC identified as ―the most sensitive population.‖ Since the NRC also identified infants and developing children as additional life stages, EPA derived potential alternative HRLs for 14 life stages ( age groups ) (identified in Table 1 ) using the RfD and l if

e stage

- specific exposure information in the August 9, 2009, notice (74 FR 41883; USEPA 2009b). These HRLs levels range from 1 μg/L to 47 μg/L and are the concentration concentration s of perchlorate in drinking water that may result in total perchlorate exposures (from food and water) greater than the RfD for individuals at this each life stage. These HRLs are calculated based on individuals who consume an average amount of perchlorate from food (except for pregnant women where EPA used a 90 th percentile dietary intake estimate), but who consume equal or more water on a per body weig ht basis than 90 percent of their cohorts. EPA has determined that the HRLs in Table 1 are more appropriate as the levels of public health concern for purposes of th is regulatory determination because the NRC identified infants and developing children as additional sensitive life stages, and the HRL values in Table 1

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### January 28, 2011

Page 14 of 35 account for the greater drinking water consumption on a per body weight basis for infants and developing children. When EPA proposes the NPDWR for perchlorate, the Agency will also
propose a Maximum Contaminant Level Goal (MCLG) for perchlorate. The MCLG is the

― maximum level of a contaminant in drinking water at which no known o r anticipated adverse effect on the health of persons would occur, and whi ch allows an adequate margin of safety. ‖ Maximum contaminant level goals are ― non - enforceable hea l th goals ‖ (CFR 141.2). EPA expects to select an MCLG from among the HRL values for infants, children, and pregnant women in Table 1.

Table 1

– Life S tage

- S pecific HRLs

.

Life Stage RfD

(μg/ kg

day) RSC a 90 th Percentile Ingestion Rate b (mL/ kg

- day) c Life stage

- specific HRL d (μg/L) Birth to < 1 month 0.7 59% 235 e 2 1 to < 3 months 0.7 59% 228 e 2 3 to < 6 months 0.7 59% 148 3 Birth to < 6 months 0.7 59% 184 2 6 to < 12 months 0.7 59% 112 4 1 to < 2 years 0.7 44% 56 6 2 to < 3 years 0.7 44% 52 6 3 to < 6 years 0.7 60% 49 9 6 to < 11 years 0.7 71% 35 14 11 to < 16 years 0.7 84% 26 23 16 to < 18 years 0.7 80% 24 23 18 to < 21 years 0.7 80% 29 19 Pregnant Women f 0.7 62% e 33 e 13 Women 15 to 44 years 0.7 80% 32 18

a R elative S ource C ontribution (RSC) calculated for nearest age range based on the mean dietary intake from FDA‘s Total Diet Study (see Table 5 at 73 FR 60275 ; USEPA 2008a )

. RSC for pregnant women and women ages 15

- 44 based on the 90 th percentile dietary intake from the National Health and Nutrition Examination Survey

- UCMR analysis (see Table 6 at 73 FR 60276 ; USEPA 2008a ). b Ingestion rate is adjusted for the self

- reported body weights from the CFSII.

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### January 28, 2011

Page 15 of 35 c Drinking Water Ingestion Rates for consumers only in Community Water Systems taken from EPA‘s  ̳ ̳Child

Specific Exposure Factors Handbook‘‘ (USEPA, 2008 b ). Except for values for infants from birth to 6 months, which are taken from Tables 5.2.A2 of EPA‘s ― Estimated Per Capita Water Ingestion and Body Weight in the United States

— An Update ‖ (USEPA, 2004), and for Pregnant Women and Women Ages 15

– 44 which are taken from Table 6.2.A2 of EPA‘s ― Estimated Per Capita Water Ingestion and Body Weight in the United States

— An Update ‖ (USEPA, 2 004). d Health reference levels (HRLs) are calculated by the following equation: HRL = RfD x Drinking Water Ingestion Rate x RSC.
e The sample sizes for the estimates of ingestion rates for these life stages do not meet the minimum data requirements as described in the ― Third Report on Nutrition Monitoring in the United States ‖ (LSRO, 1995). f The most sensitive population identified by th e NRC are the fetuses of pregnant women who might have hypothyroidism or iodide deficiency.

EPA has compared these HRL EPA is evaluating these potential alternative HRLs and considers them to be levels of public health concern for purposes of this determination. EPA has compared these values to the data provided by PWSs subject to the first Unregulated Contaminant Monitoring R ule (UCMR 1). EPA collected and analyzed drinking water occurrence data for p er chlorate from 3,865 PWSs between 2001 and 20 05 under the UCMR 1. The minimum reporting level (MRL) for perchlorate under the UCMR 1 was 4 μg/L

. EPA found that 160 (approximately 4.1 percent) of the 3,865 PWSs that sampled and reported had at least 1 analytical detection of perchlorate (in at least 1 sampling point) at levels greater than or equal to the MRL of 4 μg/L. These 160 PWSs are located in 26 States and 2 territories. Of these 160 PWSs, 8 are systems serving 10,000 or fewer people and 152 are systems serving more than 10,000 people. These 160 systems reported 637 detections of perchlorate at levels greater than or equal to 4 μg/L, which is approximately 11.3 percent of the 5,629 samples collected by these 160 PWSs and approximately 1.9 percent of the 34,331 samples collected by all 3 ,865 PWSs

. The average concentration of perchlorate for those

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### January 28, 2011

Page 16 of 35 samples with positive detections for perchlorate was 9.85 μg/L and the median concentration was 6.40 μg/L.
Table 2 1 pr esents the number and percentage of PWSs that reported perchlorate at lev els exceeding the various life stage

- specific HRLs listed in Table 1

. threshold concentrations

. Note that the MRL for perchlorate under the UCMR 1 was 4 μg/L. Table 2 indicates that the number and percentage of PWSs that reported perchlorate at levels exceeding the HRL of 2 μg/L are at least equal to the number and percentage of systems that reported perchlorate concentrations at levels equal to or greater than the MRL

. Therefore, these values would likely be greater if the UCMR 1 MRL had been lower than 4 μ g/L

. EPA plans to develop a Bayesian analysis of the perchlorate occurrence to estimate the additional number of PWSs and entry points where perchlorate is likely to occur at levels between 2 and 4 μg/L. EPA intends to present this analys i s as part of the proposed NPDWR

.

Table 2 1

– Percent Public Water System Estimates for Perchlorate above Life Stage HRLs at 90 th Percentile Drinking Water Ingestion Rates

. Thresholds of Interest Life Stage

- Specific HRL Threshold Concentration a PWSs with at Least 1 Detection > Threshold of Interest PWS Entry or Sample Points with at Least 1 Detection > Threshold of Interest b 2 μg/L a At least 4.1% (160 of 3,865) At least 2.6 % (387 of 14,987) 4 μg/L 4.0% (155 of 3,865) 2.5% (371 of 14,987) 6 μg/L 2.5% (97 of 3,865) 1.5% (219 of 14,987)
9 μg/L 1.5% (56 of 3,865) 0.77% (115 of 14,987)
13 μg/L 0.93% (36 of 3,865) 0.37% (56 of 14,987) 14 μg/L 0.85% 0.32%

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Page 17 of 35 Life Stage

- Specific HRL Threshold Concentration a PWSs with at Least 1 Detection > Threshold of Interest PWS Entry or Sample Points with at Least 1 Detection > Threshold of Interest b (33 of 3,865) (48 of 14,987)
19 μg/L 0.62% (24 of 3,865) 0.20% (30 of 14,987)
23 μg/L 0.39% (15 of 3,865) 0.13% (19 of 14,987)
a Values for 2 μg/L a All occurrence measures in this table were approximated using PWSs with detections conducted on a basis reflecting values greater than or equal to 4 μg/L

. Values would likely be greater if the UCMR 1 minimum reporting limit had been lower than 4 μg/L.

EPA has determined that the listed thresholds. Five systems detected perchlorate concentrations which are greater than the HRLs in Table 1 are the levels of public health concern. EPA has reversed its October 2008 preliminary determination that perchlorate occurs infrequently at levels of health concern in public water systems. In the October 2008 preliminary regulatory determination, EPA had derived a single HRL of 15 μg/L to reflect exposure to a pregnant woman and her fetus. EPA stated in the October 2008 notice that there are a small percentage of public water systems (0.8 percent) where drinking water above the HRL of 15 μg/L , in combination with perchlorate from food, may result in exposures to pregnant women at levels that exceed the EPA reference dose for perchlorate. However, based on EPA‘s selection of the life stage

- specific HRLs in Table 1 (many of which are lower than 15 μg/L) as the more appropriate levels of public health concern, EPA now concludes that perchlorate occurs in PWSs with a frequency and at levels of health concern. EPA estimates that at least 4.1 percent of PWSs have perchlorate exceeding one or more of the HRLs in Table 1 and that some of the consumers of these PWSs may be exposed to perchlorate (from their food and water combined) at levels that may cause them to exceed the RfD. These systems are locate d in 26 S tates and 2 territories. Therefore, EPA has determined that perchlorate occurs with a frequency and at levels of public health concern equal to 4 μg/L and are therefore not presented in this table

. Given the range of potential alternative HRLs , EPA has reversed its October 2008 preliminary determination not to regulate perchlorate in drinking water

. Based on the data in Table 1 and the range of potential alternative HRLs , EPA has determined that perchlorate is known to occur or there is a subst antial likelihood that it will occur with a frequency and at levels of public health concern. Formatted: Font: 11 pt, No underline Formatted: Font: 11 pt, No underline Formatted: Font: 11 pt, No underline

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Page 18 of 35 C. Is There a Meaningful Opportunity for the Reduction of Health Risks from Perchlorate for Persons Served by Public Water Systems?

Yes. EPA estimates that at least 5.2 to 16.8 million people are served by PWSs , for which we have data , that have detected perchlorate and at least 3 50 ,000 to 1.1 million infants and children may be exposed to perchlorate in drinking water at levels that in combination with the perchlorate in their food results in exposures that exceed the RfD for perchlorate

. ( Note that the MRL for perchlorate under the UCMR 1 was 4 μg/L , which is greater than the lowest life stage

specific HRL of 2 μg/L in Table 1. Therefore, EPA approximate d the population who are served water that has perchlorate concentrations above 2 μg/L using the population served by PWSs with perchlorate detections greater than or equal to 4 μg/L. ) T h ese population estimate s would likely be greater if the UCMR 1 MRL had been lower than 4 μg/L

. EPA also estimated that about 20 ,000 to 3 0 ,000 pregnant women would be exposed to perchlorate in drinking water above the ir life stage

- specific HRL of 13 μg/L

. EPA has determined that a NPDWR for perchlorate could reduce perchlorate exposures for these infants, children , and pregnant women to levels below the RfD , and therefore believes that this perchlorate exposure reduction presents a meaningful opportunity fo r the reduction of health risks for persons served by PWSs. EPA has made this determination based on a consideration of the best available peer reviewed science and data collected in accordance with accepted methods related to perchlorate Formatted: Font: 12 pt, No underline, Font color: Auto Formatted: Normal

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Page 19 of 35 occurrence in drinking water, the presence of perchlorate in foods, and the potential health effects of exposure to perchlorate. Table 2 presents EPA‘s estimates of the population served by PWSs that were monitored under UCMR 1 for which the highest reported perchlorate concentration was greater than the thresholds identified in Table 1. EPA has determined that a NPDWR for perchlorate could reduce perchlorate exposures for these populations to levels below the potential alternative HRLs that EPA has identifie d as levels of public health concerns for purposes of this determination, and that such exposure reductions present a meaningful opportunity for the reduction of health risks for persons served by PWSs. Specifically, Table 3 2 presents EPA‘s estimates of t he population served by PWSs that were monitored under UCMR 1 for which the highest reported perchlorate concentration was greater than the HRLs thresholds identified in Table 1. HRLs presented in the table are derived using the 90 th percentile drinking water ingestion rates for the various life stages shown in Table
1. The second column of Table 3 2 presents a range of estimates of the population served by PWSs that had at least one sample with perchlorate concentrations greater t han the
HRL threshold . The population range represents both a high end estimate, as well as a central value estimate. These population estimates were derived using the UCMR 1 monitoring data. The high end estimate of the population served drinking water above a n HRL a threshold is derived by adding the entire system population of all PWSs in which at least one sample was Formatted: Font: 12 pt, No underline, Font color: Auto

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Page 20 of 35 found to contain perchlorate above the HRL threshold

. EPA considers this a high end estimate because it is based on the assumption that t he entire system population is served water from the entry point that had the highest reported perchlorate concentration

. In fact, many PWSs have multiple entry points into which treated water is pumped for distribution to their consumers

. For the PWSs with multiple entry points, it is unlikely that the entire service population receives water from the one entry point with the highest single concentration

. Therefore, EPA also provides a central value e stimate of the population served water with perchlo rate above a n HRL a threshold in the second column in Table 3 2

. EPA developed this central value estimate by assuming the population was equally distributed among all entry points and added only the proportion of the total population served by those entry points in a PWS that had at least one sample with perchlorate concentrations greater than the HRL threshold

. For example, if a PWS with 10 entry points serving 200,000 people had a sample from a single entry point with a concentration at or above a given t hreshold, EPA assumed that the entry point served one

- tenth of the PWS population, and added 20,000 people to the total when deriving the central value population estimate . In contrast, for the high end estimate using the example above, EPA added the enti re PWS population of 200,000 to the total population. The latter is likely an overestimate. The UCMR 1 population estimates in Table 3 2 are for people at all life stages.

Table 3 2

– Population Estimates for PWSs that detected Perchlorate above HRLs Various Thresholds

. Life Stage

- Specific HRL a Threshold a Range of Population Served by PWSs with at Least 1 Detection > HRL b threshold b

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Page 21 of 35 (Million)
2 μg/L c At least 5.2

- 16.8 4 μg/L 5.1

- 16.6 6 μg/L 3.0

- 11.8 9 μg/L 1.6

- 5.2 14 μg/L 0.9

- 2.1 19 μg/L 0.7

- 1.6 23 μg/L 0.4

- 1.0

a HRLs presented in the table are derived using the 90 th percentile drinking water ingestion rates for the various life stages shown in Table 1

. All a All occurrence measures in this table were conducted on a basis reflecting values greater than the listed HRLs threshold s . All population estimates in this table are rounded. b Population estimates are derived from UCMR 1 data.
c Values for 2 μg/L were app roximated using population served by PWSs with perchlorate detections greater than or equal to 4 μg/L. Values are approximated and would likely be greater if the UCMR 1 minimum reporting limit had been lower than 4 μg/L.

Table 4 presents EPA‘s estimates of the portion of the population (from Table 3 ) that is in one of the life stage s identified in Table 1 at any given time and is served by PWSs with perchlorate concentrations above the corresponding life stage

- specific HRL. The life stages (age range) corresponding to each HRL are presented in the first column of Table 4 . The second column of Table 4 shows the range of population estimates for the portion of the population (from column 2 in Table 3 ) that is in an individual life stage at any gi ven time and is potentially served perchlorate above their life stage

- specific HRL. This range of population estimates is derived using U.S. Census data ( U.S. Census Bureau, 2008, using population estimates for July 1, 2005) to estimate the percentage of the total U.S. population in each individual life stage at any given time. The estimated percentages of the total U.S. population for each individual life stage were then multiplied by the estimates of the population served by PWSs (from column 2 of Formatted Table

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Page 22 of 35 Table 3 ) for which the highest reported perchlorate concentration was greater than the ir corresponding life stage

- specific HRLs

. For example, in Table 3 , EPA estimated that 5.1 million to 16.6 million people would be served perchlorate by PWSs above the HRL of 4 μg/L . The life stage at the HRL of 4 μg/L is children from 6 months to less than 12 months of age. Using data from the U.S. Census Bureau (U.S. C ensus Bureau, 2008) , EPA estimated the percentage of the total U.S. population from 6 months to less than 12 months of age at any given time, and then multiplied that percentage by the population of 5.1 million to 16.6 million people to estimate that about 40,000 to 120,000 children from 6 months to less than 12 months of age would be served perchlorate by PWSs with at least 1 detection above their corresponding life stage

- specific HRL of 4 μg/L

. Column 3 of Table 4 presents estimates of the cumulative lif e stage population whose total perchlorate exposure may be reduced to below the RfD if perchlorate levels in their drinking water were reduced from the levels measured under the UCMR to the HRL indicated in Table 4 . Note that at the lower HRLs there are m ore people whose exposure could be reduced below the RfD because generally, the HRLs for the younger life stages are lower than the HRLs for the older life stages. These cumulative estimates were derived by summing the individual life stage populations at any given time (from column 2 of Table 4 ) above each HRL. For example , at the HRL of 6 μg/L , EPA summed the individual life stage populations of all life stages with an HRL of 6 μg/L or greater, which included all life stages from 1 to 21 years of age.

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Page 23 of 35 Table 4

– Estimates of Population above Life Stage

- Specific HRLs

. Life Stage

- Specific HRL a Range of Population in Individual

Life Stage Served by PWSs with at Least 1 Detection > HRL b (Thousand) Cumulative Life Stage Population Served by PWSs whose exposure may be reduced to levels below the RfD if perchlorate levels in drinking water are reduced to the HRL (Thousand) c Birth to < 6 mo. 2 μg/ L d At least 40

– 120 At least 350

– 1,080 6 to < 12 mo. 4 μg/L 40

– 120 310

– 960 1 to < 3 yr. 6 μg/L 80

– 330 280

– 850 3 to < 6 yr. 9 μg/L 60

– 210 190

– 520 6 to < 11 yr. 14 μg/L 60

– 140 130

– 310 18 to < 21 yr. 19 μg/L 30

– 70 70

– 170 11 to < 18 yr. 23 μg/L 40

– 100 40

– 100

a HRLs presented in the table are derived using the 90 th percentile drinking water ingestion rates for the various life stages shown in Table 1. All occurrence measures in this table were conducted on a basis reflecting values greater than the listed HRLs. All population estimates in this table are rounded. b Population estimates are derived using U.S. Census Bureau Annual Estimates of Resident Population by Single

Year of Age and Sex for the U.S. and States: April 2, 2000 , to July 1, 2008 , using population estimates for July 1, 2005 ( U.S. Census Bureau, 2008 available at: http://www.census.gov/popest/states/asrh/ ).
c Cumulative life stage population estimates were derived by summing the individual life stage population estimates above each HRL (From column 2 of Table 4). Note that t he population estimates in this column were rounded after summing the non

- rounded values for the individual life stage population estimates

. d Values for 2 μg/L were approximated using population served by PWSs with perchlorate detections equal to 4 μg/L or greater. Values are approximated and would likely be greater if the UCMR 1 minimum reporting limit had been lower than 4 μg/L.
D. Regulatory Determination EPA has determined that perchlorate meets the criteria for regulating a contaminant in Section 1412(b)(1)(A) of SDWA. As previously discussed in this notice , perchlorate may have

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Page 24 of 35 an adverse effect on the health of persons and perchlorate is known to occur or there is a substantial likelihood that perchlorate will occur in public water systems with a frequency and at levels of public health concern. Moreover, in light of the discussion in this notice and the information available at this time , the Administrator finds that regulation of perchlorate in drinking wate r systems at this time presents a meaningful opportunity for health risk reduction for persons served by public water systems. Therefore, EPA will initiate the process of proposing a NPDWR for perchlorate.

E. Key Commenter Issues

EPA received a total of approximately 39,000 comments from individuals or organizations on the May 2007, October 2008, and August 2009 Federal Register notices regarding the perchlorate regulatory determination. This section briefly discusses a number of the key issues raised by commenters and EPA‘s response to these concerns. Responses to all of the comments received are available in the ―Comment Response Document for the Final Regulatory Determination on Perchlorate‖ (USEPA, 2010a) available at http://w ww.regulations.gov ( D ocket ID No. EPA

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Page 25 of 35 1. Health Implications of Perchlorate Exposure above the RfD

EPA received comments indicating that the levels of perchlorate in drinking water that result in exposures greater than the RfD are not levels of public health concern because the RfD is based on a precursor to an adverse effect. EPA disagrees, and believes the NRC appropriately based the RfD on iodide uptake inhibition to the thyroid, for the reasons discussed in its report.
EPA also received a substantial number of comments supporting the Agency‘s current view

. The EPA notes that t

he data underl ying the definition of iodide uptake inhibition as a precursor effect and the relationship of iodide uptake inhibition to the continuum of adverse outcomes reflects an understanding of effects in adults ; it may not reflect the relationship of the precursor event to adverse outcomes in children. W e know that thyroid hormone status in neonates and infants is less resilient than in adults. That is, in general, neonates and infants , who may not have iodide stores sufficient to offset the effects of reduced iodide uptake. Half

- lives for circulating hormones in neonates and infants are shorter than for adults, making neonates and infants less able to maintain stable hormone levels in the face of a chemical insult. The less resilient neonatal and infant syste m makes the exposure gap between a precursor event (iodide uptake inhibition due to perchlorate) and reduced T3/T4 levels likely to be narrower than for adults, and in fact, the distinction between the two may be blurred for the very young ( Greer et al., 2 002; Savin et al., 2003; van den Hove et al., 1999). T he NRC noted that , ― [T]he minimal prolonged

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Page 26 of 35 decrease in thyroid hormone production that would be associated with adverse health effects is not known; any decrease is potentially more likely to have adv erse effects in sensitive populations (people with thyroid disorders, pregnant women, fetuses, and infants) but data are not available to determine the magnitude of the decrease needed to cause adverse effects in those populations. ‖ The additional sensiti vity of these groups to perturbations in thyroid hormone levels, and the uncertainty about the point in the continuum of effects at which advers e effects

occur are important considerations in concluding that perchlorate exposures above the RfD are likely to have an adverse effect on the health of sensitive life stages. Therefore, we do not agree with those comment e rs who stated that levels of perchlorate in drinking water that result in exposures greater than the RfD are not levels of public health concern.

2. Other Thyroid Inhibiting Chemicals

EPA received a number of comments that the Agency should consider the comparative effect on iodine uptake of perchlorate exposure in drinking water to nitrate and thiocyanate exposure in drinking water i n determining whether there is a meaningful opportunity for risk reduction. Other commenters, including EPA‘s Office of Inspector General (USEPA, 2008c), believe that a NPDWR for a group of chemicals may be appropriate based on a yet

- to

- be

conducted cumul ative risk assessment that assesses and characterizes the combined human health risk from perchlorate, nitrate, and thiocyanate. Formatted: Font: Times New Roman, No underline, Font color: Auto Formatted: Font: Times New Roman

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Page 27 of 35 While EPA acknowledges that nitrate and thiocyanate have the same mode of action as perchlorate, and that the effects of combi ned exposure to perchlorate, nitrate, and thiocyanate are additive , EPA does not believe there are sufficient scientific data currently available to assess and characterize the combined risk of these contaminants. EPA has committed to a drinking
water str ategy that outlines four principles to expand public health protection for drinking water (USEPA, 2010b). One of these principles is to address contaminants as groups. However, EPA does not believe that regulatory action to address perchlorate should be further delayed. Therefore, EPA intends to develop a proposed rule for perchlorate. At such time as a NPDWR is promulgated, EPA is required to review and revise, as appropriate, its drinking water standards at least every six years. A ny revision must at least maintain or improve public health protection. When there are sufficient scientific data to assess the cumulative risks of perchlorate and other contaminants , EPA will review this information to evaluate whether any revisions of NPDWRs are appropria te.

3. Perchlorate in Food

A commenter wrote that a drinking water regulation for perchlorate does not present a meaningful opportunity for health risk reduction because perchlorate contamination in food is widespread. Other commenters indicated t hat EPA should regulate perchlorate in drinking water to reduce the public‘s overall exposure to perchlorate. EPA agrees that perchlorate

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Page 28 of 35 contamination is more widespread in foods than in PWSs; however, EPA does not believe that the widespread presence of perchlorate in food overrides the need for public health risk reduction for persons served by PWSs with perchlorate contamination. The Agency presented an extensive evaluation of dietary exposure to perchlorate in the October 2008 and August 2009 notices ( 73 FR 60262; USEPA 2008a and 74 FR 41883; USEPA 2009b)

. EPA has used this dietary exposure data to account for the relative source contribution (RSC) of perchlorate from food to estimate the HRLs in Table 1. EPA has further evaluated the populations ex posed to perchlorate from both food and drinking water in Table s 3 and 4

. In Table 3 , EPA has estimated the population whose total perchlorate exposure may exceed the RfD (based on the population whose levels of perchlorate in drinking water under UCMR 1 exceed the HRL s ) . In Table 4 , EPA has estimated the cumulative life stage population served by PWSs whose total perchlorate exposure may be reduced t o levels below the RfD if th ose levels in drinking water were reduced to the HRL. range of levels of public health concern. EPA recognizes that a drinking water regulation would not eliminate total perchlorate exposure, but believes that the reduction in perchlorate exposure in drinking water presents a meaningful opportunity for health risk reduction for persons served by PWSs contaminated by perchlorate.

4. Iodide Nutritional Status

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Page 29 of 35 Some commenters stated that public health concerns over iodide uptake inhibition could be addressed more efficiently through promotion of iodide nutrition than through regulation of perchlorate. EPA agrees that promoting iodide nutrition is good public health policy and may have a positive influence in reducing the iodide uptake inhibition effects assoc iated with exposure to perchlorate. However, the Agency does not think it is appropriate to rely on the promotion of iodide nutrition in this case, especially since these activities are outside of EPA‘s SDWA authority. As a result, while the health conce rns associated with perchlorate may be addressed through other means, it is the Administrator‘s judgment that a standard limiting perchlorate in drinking water can reduce health risk, particularly to fetuses, infants and children.

5. Physiologically

- Based Pharmacokinetic (PBPK) Modeling

EPA reviewed, modified, and applied the perchlorate PBPK models, which were originally developed by Merrill et al. (2005) for adults and Clewell et al. (2007) for other life stages, to estimate the iodide uptake inhibition in the thyroid for each life

- stage ( 73 FR 60262;
USEPA 2008a ). Estimated ingestion rates were then used to estimate the internal dose and resulting iodide uptake inhibition for several life stages, including susceptible populations (e.g., pregnant women and their fetuses, as well as breast

- fed and bottle

- fed infants).

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Page 30 of 35 In the August 2009 notice , EPA stated that it was re - evaluating how best to incorporate the PBPK modeling analysis into its evaluation of perchlorate

— if at all . The Agency sought

commen ts on ways to use the PBPK modeling analysis to inform the regulatory determination. Several commenters supported the use of the PBPK model to inform the regulatory determination only if the significant limitations of the current model are addressed. Fo r example,
t he inability of the model to reflect iodide nutritional status was cited by commenters and three of four peer reviewers as an important limitation (USEPA, 2008d). EPA agrees with the stated limitations of the model. Also, several commenters stated that the risks to breast

- fed infants and young children are not adequately addressed by the model. They challenged that the modeling analysis is based on average weight infants and healthy adults , while the sensitive life stages for perchlorate include premature infants and hypothyroid women

. EPA agrees. After further consideration of the peer review and public comments, EPA concludes that the PBPK modeling analysis, in the context of the perchlorate regulatory determination, is useful in examining which life stage s are most susceptible to the effects of perchlor ate. For example, the model indicates that a fetus may be seven times more sensitive to the effects of perchlorate than a pregnant woman. The model also allows for the e stimation of the concentration of perchlorate in breast milk (thus breast

- fed infant exposure) at various maternal perchlorate exposure levels. However, because of the stated limitations, EPA has decided the model does not directly bear on the current dec ision regarding the need for a NPDWR for perchlorate. EPA is continuing to evaluate whether the model could be used in setting a NPDWR for perchlorate.

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Page 31 of 35 F. Next Steps

EPA is initiating the development of a proposed NPDWR for perchlorate. However, this is not the end of a decision process but a middle step in a process that leads to a final drinking water standard. Based on this decision, EPA intends to publish a propo sed NPDWR for public review and comment within 24 months of this notice. 2 EPA will continue to evaluate the science as we develop the proposed NPDWR. E PA will, as part of the proposed NPDWR, present a health risk reduction and cost analyses, an analysis of feasible treatment methods, and an analysis of small system compliance technologies. EPA will also consult with the National Drinking Water Advisory Council, the Science Advisory Board, and the Secretary of Health and Human Services, as required under SDWA.

2 On January 8, 2009, EPA issued an interim health advisory to provide guidance to State and local officials in their efforts to ad dress perchlorate contamination. The interim health advisory (USEPA, 2008e) can be found at: http://www.epa.gov/safewater/contaminants/unregula ted/pdfs/healthadvisory_perchlorate_interim.pdf and in EPA‘s docket ID No. EPA

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- 0297 for this notice

. EPA expects to make a final decision on the interim health advisory at such time as a definitive decision has been made with respect to the promulgation of a final perchlorate regulation. Formatted: Line spacing: single, Adjust space between Latin and Asian text, Adjust space between Asian text and numbers Formatted: Font: Times New Roman, 12 pt

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Page 32 of 35 IV. References Clewell, R.A., E.A. Merrill, J.M. Gearhart, P.J. Robinson, T.R. Sterner, D.R. Mattie, and H.J. Clewell, III. 2007. Perchlorate and radiodide kinetics across life stages in the human: using PBPK models to predict dosimetry and thyroid inhibition and sensit ive subpopulations based on developmental stage. Journal of Toxicology and Environmental Health. Part A. Vol. 70

. Issue 5. p. 408

- 428. Greer, M.A., G. Goodman, R.C. Pleuss, and S.E. Greer. 2002. Health effect assessment for environmental perchlorate cont amination: the dose response for inhibition of thyroidal radioiodide uptake in humans. Environ Health Perspect Vol. 110. p. 927

– 937. Life Sciences Research Office (LSRO), Federation of American Studies for Experimental Biology Prepared for the Interagenc y Board for Nutrition Monitoring and Related Research. 1995. Third Report on Nutrition Monitoring in the United States: Volume 1. U.S. Government Printing Office, Washington D.C. Merrill, E.A., R.A. Clewell, P.J. Robinson, A.M. Jarabek, T.R. Sterner, an d J.W. Fisher. 2005. PBPK model for radioactive iodide and perchlorate kinetics and perchlorate

- induced inhibition of iodide uptake in humans. Toxicological Sciences . Vol. 83 . p. 25

- 43. National Research Council (NRC). 2005. Health Implications of Perchl orate Ingestion . National Academies Press, Board on Environmental Studies and Toxicology. January 2005. 276 p.

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Page 33 of 35 Savin, S., D. Dvejic, O. Nedic, R. Radosavljevic. 2003. Thyroid Hormone Synthesis and Storage in the Thyroid Gland of Human Neonates. J. Pediatri c Endocrinology & Metabolism. Vol. 16. p. 521

- 528.
U.S. Census Bureau

. 2008. U.S. Census Bureau Annual Estimates of Resident Population by Single

- Year of Age and Sex for the U.S. and States: April 2, 2000 to July 1, 2008. Available on the internet at: http://www.census.gov/popest/states/asrh/

. USEPA. 1998. Announcement of the Drinking Water Contaminant Candidate List; Notice. Federal Register . Vol. 63, No. 40. p. 10273, March 2, 1998. USEPA. 2004. Estimated Per Capita Water Ingestion and Body Weight in the United States

- An Update. Office of Science and Technology, Washington, DC; EPA/822/R

- 00

- 001. USEPA. 2005 a . Drinking Water Contaminant Candidate List 2; Final Notice. Federal Regi ster

. Vol. 70, No. 36. p. 9071, February 24, 2005.
USEPA. 2005 b . ―Integrated Risk Information System (IRIS), Perchlorate and Perchlorate Salts.‖ February 2005. Available on the Internet at: http://www.epa.gov/iris/subst/1007.htm

. Accessed February 2, 2005.
USEPA. 2007. Drinking Water: Regulatory Determinations Regarding Contaminants on the Second Drinking Water Contaminant Candidate List

– Preliminary
D eterminations , Federal Register, Vol. 72, No. 83. p. 2401 6, May 1, 2007. USEPA. 2008a. Drinking Water: Preliminary Regulatory Determination on Perchlorate, Federal Register, Vol. 73, No. 198. p. 60262, October 10, 2008. Formatted: Font: Arial, 10 pt, No underline, Font color: Auto Field Code Changed

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Page 34 of 35 USEPA. 2008b. Child

- Specific Exposure Factors Handbook. National Center for Environmental Assessment, Washington, DC; EPA/600/R

- 06/096F. USEPA. 2008c. Scientific Analysis of Perchlorate (External Review Draft). Office of Inspector General, Washington, DC; Assignment No. 2008

- 0010. Available on the Internet at: http:// www.epa.gov/ oig/reports/2010/20100419

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- 0101.pdf

. USEPA. 2008d. Comment Response Summary Report, Peer Review of Drinking Water Health Advisory for Perchlorate. Office of Science and T echnology, Washington, DC; December
2008. USEPA. 2008e. Interim Drinking Water Health Advisory for Perchlorate. Office of Science and Technology, Washington, DC; EPA 822

- R

- 08

- 025. USEPA. 2009a. Drinking Water Contaminant Candidate List 3

- Final. Federal Register. Vol. 74, No. 194. p. 51850, October 8, 2009. USEPA. 2009b. Drinking Water: Perchlorate Supplemental Request for Comments, Federal Register, Vol. 74, No. 159. p. 41883, August 19, 2009. USEPA. 2010a. Comment Response Document for the Final Re gulatory Determination on Perchlorate (Categorized Public Comments). EPA XXX

- XXX. December, 2010. USEPA. 2010b. A New Approach to Protecting Drinking Water and Public Health. EPA 815

- F

10

- 001. Available on the Internet at: http:// water.epa.gov/lawsreg s/rulesregs/sdwa/dwstrategy/index.cfm

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Page 35 of 35 van den Hove , M.F., C. Beckers, H. Devlieger, F. de Zegher, P. De Nayer. 1999. Hormone synthesis and storage in the thyroid of human preterm and term newborns: Effect of thyroxine treatment. Biochimie. Vol. 81. p. 563

- 570. Zimmerman, M. 2009. Iodide Deficiency. Endocrine Reviews. Vol. 30, No. 4. p. 376

- 408.

Dated:

Lisa P . Jackson, Administrator.
BILLING CODE 6560

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