3830 Federal Register / Vol. 90, No. 9 / Wednesday, January 15, 2025 / Notices 

SACC Meeting; Availability; and Request for 

Comment. Federal Register. 89 FR 43847, 

May 20, 2024 (FRL–11760–02–OCSPP). 

5. EPA. Di-isononyl phthalate (DINP); Draft 

Risk Evaluation Under the Toxic Substances 

Control Act (TSCA); Notice of Availability, 

Webinar and Request for Comment. Federal 

Register. 89 FR 71270, September 3, 2024 

(FRL–8806–02–OCSPP). 

6. EPA. Comment Summary and Responses 

for Di-isodecyl Phthalate (DIDP) and 

Diisononyl Phthalate (DINP). December 2024. 

7. EPA. Nontechnical Summary of the 

TSCA Risk Evaluation for Di-isononyl 

Phthalate (DINP). December 2024. (EPA 

Publication ID No. EPA–740–S–25–001). 

8. EPA. TSCA Risk Evaluation for Diisononyl Phthalate (DINP). December 2024. 

(EPA Publication ID No. EPA–740–R–25– 

001). 

Authority: 15 U.S.C. 2601 et seq. 

Dated: January 7, 2025. 

Michal Freedhoff, 

Assistant Administrator, Office of Chemical 

Safety and Pollution Prevention. 

[FR Doc. 2025–00730 Filed 1–14–25; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

[EPA–HQ–OW–2024–0456; FRL–10774–01– 

OW] 

Announcement of Preliminary 

Regulatory Determinations for 

Contaminants on the Fifth Drinking 

Water Contaminant Candidate List 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Request for public comment. 

SUMMARY: The Safe Drinking Water Act 

(SDWA), as amended in 1996, requires 

that the U.S. Environmental Protection 

Agency (EPA) determine whether to 

regulate at least five unregulated 

contaminants every five years. The 

decision to regulate or not to regulate a 

contaminant is known as a regulatory 

determination. In most cases, the 

contaminants chosen for regulatory 

determination are selected from the 

most recent Contaminant Candidate List 

(CCL), which the SDWA requires the 

EPA to publish every five years. This 

document presents the preliminary 

regulatory determinations and 

supporting rationale for contaminants 

listed on the EPA’s fifth CCL (CCL 5). 

Since the fourth round of regulatory 

determinations was published in March 

2021, the EPA has made determinations 

to regulate per- and polyfluoroalkyl 

substances (PFAS), including individual 

determinations for three PFAS: 

perfluorononanoic acid (PFNA), 

perfluorohexanesulfonic acid (PFHxS), 

hexafluoropropylene oxide dimer acid 

and its ammonium salt (HFPO–DA, also 

known as GenX or GenX chemicals); 

and mixtures including two or more of 

these three PFAS and 

perfluorobutanesulfonic acid (PFBS). In 

April 2024, the agency issued a final 

National Primary Drinking Water 

Regulation that includes these four 

PFAS as well as perfluorooctanoic acid 

(PFOA) and perfluorooctanesulfonic 

acid (PFOS). In this Federal Register 

Notice (FRN), the EPA is making 

preliminary determinations not to 

regulate nine additional contaminants 

from CCL 5: 2-aminotoluene, 

cylindrospermopsin, ethoprop, 

microcystins, molybdenum, permethrin, 

profenofos, tebuconazole and tribufos. 

The EPA requests public comment on 

these preliminary determinations and 

other aspects of this FRN. The EPA also 

presents updates on additional 

contaminants from CCL 5, as well as on 

some of those that have been considered 

in previous rounds of regulatory 

determinations and for which the EPA 

has not yet made a regulatory 

determination. The agency is also 

presenting and requesting comment on 

the process and analyses used for this 

round of regulatory determinations (i.e., 

RD 5), the supporting information, and 

the rationale used to make these 

preliminary decisions. 

DATES: Comments must be received on 

or before March 17, 2025. 

ADDRESSES: You may send comments, 

identified by Docket ID No. EPA–HQ– 

OW–2024–0456, by any of the following 

methods: 

• Federal eRulemaking Portal: 

https://www.regulations.gov/ (our 

preferred method). Follow the online 

instructions for submitting comments. 

• Mail: Water Docket, Environmental 

Protection Agency, Mail Code: [28221T], 

1200 Pennsylvania Ave. NW, 

Washington, DC 20460. 

• Hand Delivery: EPA Docket Center, 

[EPA/DC] EPA West, Room 3334, 1301 

Constitution Ave. NW, Washington DC. 

Such deliveries are only accepted 

during the Docket’s normal hours of 

operation and special arrangements 

should be made for deliveries of boxed 

information. 

Instructions: All submissions received 

must include the Docket ID No. for this 

rulemaking. Comments received may be 

posted without change to https://

www.regulations.gov/, including any 

personal information provided. For 

detailed instructions on sending 

comments and additional information 

on the rulemaking process, see the 

‘‘Written Comments’’ heading of the 

SUPPLEMENTARY INFORMATION section of 

this document. 

FOR FURTHER INFORMATION CONTACT: 

George Gardenier, Standards and Risk 

Management Division, Office of Ground 

Water and Drinking Water, MC: 4607M, 

Environmental Protection Agency, 1200 

Pennsylvania Ave. NW, Washington, DC 

20460; telephone number: (202) 564– 

3333; email address: gardenier.george@

epa.gov. 

SUPPLEMENTARY INFORMATION: 

I. General Information 

A. Written Comments 

Submit your comments, identified by 

Docket ID No. EPA–HQ–OW–2024– 

0456, at https://www.regulations.gov 

(our preferred method), or the other 

methods identified in the ADDRESSES

section. Once submitted, comments 

cannot be edited or removed from the 

docket. The EPA may publish any 

comment received to its public docket. 

Do not submit electronically any 

information you consider to be 

Confidential Business Information (CBI) 

or other information whose disclosure is 

restricted by statute. Multimedia 

submissions (audio, video, etc.) must be 

accompanied by a written comment. 

The written comment is considered the 

official comment and should include 

discussion of all points you wish to 

make. The EPA will generally not 

consider comments or comment 

contents located outside of the primary 

submission (i.e., on the web, cloud or 

other file sharing system). For 

additional submission methods, the full 

EPA public comment policy, 

information about CBI or multimedia 

submissions, and general guidance on 

making effective comments, please visit 

https://www.epa.gov/dockets/ 

commenting-epa-dockets. 

When submitting comments, 

remember to: 

• Identify the rulemaking by docket 

number and other identifying 

information (subject heading, Federal 

Register date and page number). 

• Explain why you agree or disagree 

and suggest alternatives. 

• Describe any assumptions and 

provide any technical information and 

data that you used. 

• Provide specific examples to 

illustrate your concerns and suggest 

alternatives. 

• Explain your views as clearly as 

possible. 


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• Make sure to submit your 

comments by the comment period 

deadline identified. 

B. Does this action apply to me? 

Neither these preliminary regulatory 

determinations nor the final regulatory 

determinations, when published, 

impose any requirements on anyone. 

Instead, this action notifies interested 

parties of the EPA’s preliminary 

regulatory determinations for nine 

unregulated contaminants for comment. 

Abbreviations Used in This Document 

Abbreviation Meaning 

AChE ................ Acetylcholinesterase. 

ADAF ................ Age Dependent Adjustment Factor. 

AM .................... Assessment Monitoring. 

ATSDR ............. Agency for Toxic Substances and Disease Registry. 

ATSDR MRL ..... ATSDR Minimal Risk Level. 

AWIA ................ America’s Water Infrastructure Act. 

BAT ................... Best Available Technology. 

BMD .................. Benchmark Dose. 

BMDL10 ............. Lower 95% Confidence Limit on the Benchmark Dose Level Associated with a 10% Response. 

BMDL1SD .......... Lower 95% Confidence Limit on the Benchmark Dose Level Associated with a Difference of One Standard Deviation from 

Controls. 

BW .................... Body Weight. 

CBI .................... Confidential Business Information. 

CCL .................. Contaminant Candidate List. 

CCL 1 ............... First Contaminant Candidate List. 

CCL 2 ............... Second Contaminant Candidate List. 

CCL 3 ............... Third Contaminant Candidate List. 

CCL 4 ............... Fourth Contaminant Candidate List. 

CCL 5 ............... Fifth Contaminant Candidate List. 

CCR .................. Consumer Confidence Report. 

CDR .................. Chemical Data Reporting. 

ChE ................... Cholinesterase. 

CRL .................. Cancer Risk Level. 

CSF .................. Cancer Slope Factor. 

CWA ................. Clean Water Act. 

CWS ................. Community Water System. 

CWSS ............... Community Water System Survey. 

DBP .................. Disinfection Byproduct. 

DDE .................. 1,1-Dichloro-2,2-bis(p-chlorophenyl)ethylene. 

DWI ................... Drinking Water Intake. 

DWI–BW ........... Drinking Water Intake Adjusted for Body Weight. 

EF ..................... Exposure Factor. 

EPA .................. U. S. Environmental Protection Agency. 

EPTC ................ S-Ethyl dipropylthiocarbamate. 

FIFRA ............... Federal Insecticide, Fungicide and Rodenticide Act. 

FQPA ................ Food Quality Protection Act. 

FR ..................... Federal Register. 

FRN .................. Federal Register Notice. 

Gen X ............... Gen X Chemicals (i.e., HFPO dimer acid and its ammonium salt), also known as (2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3- 

heptafluoropropoxy)propanoic acid (CASRN 13252–13–6) or hexafluoropropylene oxide (HFPO) dimer acid (HFPO–DA) 

and 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)propanoate (CASRN 62037–80–3) or HFPO–DA dimer acid and 

its ammonium salt). 

GWUDI ............. Groundwater Under the Direct Influence of Surface Water. 

HA ..................... Health Advisory. 

HAA5 ................ Sum of Five Haloacetic Acids. 

HAB .................. Harmful Algal Bloom. 

HCl .................... Hydrochloride. 

HED .................. Health Effects Division. 

HESD ................ Health Effects Support Document. 

HFPO–DA ......... Hexafluoropropylene Oxide Dimer Acid. 

HHRA ............... Human Health Risk Assessment. 

HRL .................. Health Reference Level. 

HRRCA ............. Health Risk Reduction Cost Analysis. 

IUR ................... Inventory Update Reporting. 

Koc .................... Organic Carbon Partitioning Coefficient. 

Kow .................... Octanol-Water Partitioning Coefficient. 

LOAEL .............. Lowest Observed Adverse Effect Level. 

MAC .................. Maximum Acceptable Concentration. 

MCL .................. Maximum Contaminant Level. 

MCLG ............... Maximum Contaminant Level Goal. 

MOA ................. Mode of Action. 

MRL .................. Minimum Reporting Level. 

NAS .................. National Academy of Sciences. 

NAWQA ............ National Water-Quality Assessment. 

NDBA ................ N-Nitrosodi-n-butylamine. 

NDEA ................ N-Nitrosodiethylamine. 

NDMA ............... N-Nitrosodimethylamine. 


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Abbreviation Meaning 

NDPA ................ N-Nitroso-di-n-propylamine. 

NPYR ................ N-Nitrosopyrrolidine. 

NDWAC ............ National Drinking Water Advisory Council. 

NIRS ................. National Inorganics and Radionuclides Survey. 

NOAEL ............. No Observed Adverse Effect Level. 

NPDWR ............ National Primary Drinking Water Regulation. 

NRC .................. National Research Council. 

NRDC ............... Natural Resources Defense Council. 

NWIS ................ National Water Information System. 

OPP .................. Office of Pesticides Program. 

OW ................... Office of Water. 

PAD .................. Population-Adjusted Dose. 

PCCL ................ Preliminary Contaminant Candidate List. 

PDP .................. Pesticide Data Program. 

PFAS ................ Per- and Polyfluoroalkyl Substances. 

PFBA ................ Perfluorobutanoic acid. 

PFBS ................ Perfluorobutanesulfonic acid. 

PFHxS .............. Perfluorohexanesulfonic acid. 

PFNA ................ Perfluorononanoic acid. 

PFOA ................ Perfluorooctanoic acid. 

PFOS ................ Perfluorooctanesulfonic acid. 

PMP .................. Pilot Monitoring Program. 

PND .................. Postnatal Day. 

POD .................. Point of Departure. 

PPRTV .............. Provisional Peer-Reviewed Toxicity Value. 

PST ................... Pre-Screen Testing. 

PWS ................. Public Water System. 

RBC .................. Red Blood Cell. 

RD 1 ................. Regulatory Determination 1. 

RD 2 ................. Regulatory Determination 2. 

RD 3 ................. Regulatory Determination 3. 

RD 4 ................. Regulatory Determination 4. 

RD 5 ................. Regulatory Determination 5. 

RDX .................. Royal Demolition eXplosive. 

RED .................. Reregistration Eligibility Decision. 

RfD ................... Reference Dose. 

RSC .................. Relative Source Contribution. 

RUP .................. Restricted Use Pesticide. 

SDWA ............... Safe Drinking Water Act. 

SS ..................... Screening Survey. 

SSCT ................ Small System Compliance Technology. 

STORET ........... Storage and Retrieval Data System. 

TCP .................. Trichloropropane. 

TDI .................... Tolerable Daily Intake. 

TRI .................... Toxics Release Inventory. 

TSCA ................ Toxic Substances Control Act. 

TT ..................... Treatment Technique. 

TTHM ................ Total Trihalomethanes. 

UA ..................... Unit Adjustment Factor. 

UCM ................. Unregulated Contaminant Monitoring. 

UCMR ............... Unregulated Contaminant Monitoring Rule. 

UCMR 1 ............ First Unregulated Contaminant Monitoring Rule. 

UCMR 2 ............ Second Unregulated Contaminant Monitoring Rule. 

UCMR 3 ............ Third Unregulated Contaminant Monitoring Rule. 

UCMR 4 ............ Fourth Unregulated Contaminant Monitoring Rule. 

UCMR 5 ............ Fifth Unregulated Contaminant Monitoring Rule. 

UF ..................... Uncertainty Factor. 

UFA ................... Interspecies Uncertainty Factor. 

UFD ................... Database Uncertainty Factor. 

UFH ................... Intraspecies Uncertainty Factor. 

UFL ................... LOAEL-to-NOAEL Extrapolation Uncertainty Factor. 

UFS ................... Subchronic-to Chronic Exposure Duration Uncertainty Factor. 

USDA ................ United States Department of Agriculture. 

USEPA ............. United States Environmental Protection Agency. 

USGS ............... United States Geological Survey. 

WQP ................. Water Quality Portal. 

WQX ................. Water Quality Exchange. 

Table of Contents 

I. General Information 

A. Written Comments 

B. Does this action apply to me? 

II. Purpose and Background 

A. What is the purpose of this action? 

B. Background on the CCL and Regulatory 

Determinations 

1. Statutory Requirements for CCL and 

Regulatory Determinations 


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1An MCLG is the maximum level of a 

contaminant in drinking water at which no known 

or anticipated adverse effect on the health of 

persons would occur, and which allows an 

adequate margin of safety. MCLGs are nonenforceable health goals. (40 CFR 141.2; 42 U.S.C. 

300g–1) 

2An NPDWR is a legally enforceable standard 

that applies to public water systems. An NPDWR 

sets a legal limit (called a maximum contaminant 

level or MCL) or specifies a certain treatment 

technique (TT) for public water systems for a 

specific contaminant or group of contaminants. The 

MCL is the highest level of a contaminant that is 

allowed in drinking water and is set as close to the 

MCLG as feasible using the best available treatment 

technology and taking cost into consideration. 

3The statute authorizes a nine-month extension 

of this promulgation date. 

4Consumer information about Acanthamoeba for 

people who wear contact lenses can be found at 

http://water.epa.gov/action/advisories/ 

acanthamoeba/index.cfm. 

5Health advisories provide information on 

contaminants that can cause human health effects 

and are known or anticipated to occur in drinking 

water. The EPA’s health advisories are nonenforceable and provide technical guidance to 

states agencies and other public health officials on 

health effects, analytical methodologies and 

treatment technologies associated with drinking 

water contamination. Health advisories can be 

found at http://water.epa.gov/drink/standards/ 

hascience.cfm. See also SDWA Section 

1412(b)(1)(F). 

2. The First Contaminant Candidate List 

(CCL 1) and Regulatory Determination 

(RD 1) 

3. The Second Contaminant Candidate List 

(CCL 2) and Regulatory Determination 

(RD 2) 

4. The Third Contaminant Candidate List 

(CCL 3) and Regulatory Determination 

(RD 3) 

5. The Fourth Contaminant Candidate List 

(CCL 4) and Regulatory Determination 

(RD 4) 

6. The Fifth Contaminant Candidate List 

(CCL 5) 

III. Approach and Overall Outcomes for RD 

5 

A. Summary of the Approach and Overall 

Outcomes for RD 5 

1. Phase 1 (Data Availability Phase) 

2. Phase 2 (Data Evaluation Phase) 

3. Phase 3 (Regulatory Determination 

Assessment Phase) 

B. Supporting Documentation for the EPA’s 

Preliminary Determination 

C. Analyses Used To Support the 

Preliminary Regulatory Determinations 

1. Evaluation of Contaminant Occurrence 

and Exposure 

IV. Contaminant-Specific Discussions for the 

RD 5 Preliminary Determination 

A. Summary of the Preliminary Regulatory 

Determinations 

B. Contaminant Profiles 

1. 2-Aminotoluene 

2. Cylindrospermopsin 

3. Ethoprop 

4. Microcystins 

5. Molybdenum 

6. Permethrin 

7. Profenofos 

8. Tebuconazole 

9. Tribufos 

V. Status of the Agency’s Evaluation of 1,2,3- 

Trichloropropane, 1,4-Dioxane, 

Manganese, Quinoline and Strontium 

A. Ongoing Evaluation of Additional Phase 

3 Contaminants 

B. Phase 3 Contaminant Updates 

1. 1,2,3-Trichloropropane 

2. 1,4-Dioxane 

3. Manganese 

4. Quinoline 

5. Strontium 

VI. The EPA’s Request for Comments and 

Next Steps 

VII. References 

II. Purpose and Background 

A. What is the purpose of this action? 

The purpose of this action is to 

request comment on the EPA’s 

preliminary determinations not to 

regulate the following nine 

contaminants under the Safe Drinking 

Water Act: 2-aminotoluene, 

cylindrospermopsin, ethoprop, 

microcystins, molybdenum, permethrin, 

profenofos, tebuconazole and tribufos. 

As required by the SDWA, the EPA is 

seeking comment on these preliminary 

determinations. The agency is also 

presenting and requesting comment on 

the process and analyses used for this 

round of regulatory determinations (i.e., 

RD 5), the supporting information, and 

the rationale used to make these 

preliminary decisions. It should be 

noted that the analyses associated with 

a regulatory determination are distinct 

from the more detailed analyses 

required to develop a National Primary 

Drinking Water Regulation (NPDWR). 

B. Background on the CCL and 

Regulatory Determinations 

1. Statutory Requirements for CCL and 

Regulatory Determinations 

Section 1412(b)(1)(B)(i) of the SDWA 

requires the EPA to publish the CCL 

every five years after public notice and 

an opportunity to comment. The CCL is 

a list of contaminants which are not 

subject to any proposed or promulgated 

NPDWRs but are known or anticipated 

to occur in public water systems (PWSs) 

and may require regulation under the 

SDWA. SDWA section 1412(b)(1)(B)(ii) 

directs the EPA to determine, whether 

to regulate at least five contaminants 

from the CCL every five years. Under 

section 1412(b)(1)(A) of SDWA, the EPA 

may regulate a contaminant in drinking 

water if the Administrator determines 

that: 

(i) the contaminant may have an 

adverse effect on the health of persons; 

(ii) the contaminant is known to occur 

or there is substantial likelihood that the 

contaminant will occur in PWSs with a 

frequency and at levels of public health 

concern; and 

(iii) in the sole judgment of the 

Administrator, regulation of such 

contaminant presents a meaningful 

opportunity for health risk reduction for 

persons served by PWSs. 

SDWA 1412(b)(1)(C) requires that the 

Administrator prioritize selection of 

contaminants that present the greatest 

public health concern. The 

Administrator, in making such 

selections, shall take into consideration, 

among other factors of public health 

concern, the effect of such contaminants 

upon subgroups that comprise a 

meaningful portion of the general 

population (such as infants, children, 

pregnant women, the elderly, 

individuals with a history of serious 

illness or other subpopulations) that are 

identifiable as being at greater risk of 

adverse health effects due to exposure to 

contaminants in drinking water than the 

general population. 

If the EPA determines that these three 

statutory criteria are met and makes a 

final determination to regulate a 

contaminant (i.e., a positive 

determination), the agency must publish 

a proposed Maximum Contaminant 

Level Goal (MCLG) 1 and NPDWR2

within 24 months. After a proposal, the 

agency must publish a final MCLG and 

promulgate a final NPDWR (SDWA 

section 1412(b)(1)(E)) within 18 

months.3 The EPA may also develop 

regulatory determinations and 

associated rulemakings outside of the 

SDWA mandated process. 

2. The First Contaminant Candidate List 

(CCL 1) and Regulatory Determination 

(RD 1) 

The EPA published the final CCL 1, 

which contained 60 chemical and 

microbiological contaminants, in the 

Federal Register (FR) on March 2, 1998 

(63 FR 10273; USEPA, 1998). The 

agency published the final regulatory 

determinations for nine of the 60 CCL 1 

contaminants in the FR on July 18, 2003 

(68 FR 42898; USEPA, 2003). The 

agency determined not to regulate the 

following nine contaminants with 

NPDWRs: Acanthamoeba, aldrin, 

dieldrin, hexachlorobutadiene, 

manganese, metribuzin, naphthalene, 

sodium and sulfate. The agency posted 

information about Acanthamoeba 4 on 

the EPA’s website and issued health 

advisories (HAs) 5 for manganese, 

sodium and sulfate. 

3. The Second Contaminant Candidate 

List (CCL 2) and Regulatory 

Determination (RD 2) 

The agency published the final CCL 2 

in the FR on February 24, 2005 (70 FR 

9071; USEPA, 2005a) and carried 


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forward the 51 remaining chemical and 

microbial contaminants listed on CCL 1. 

The agency published the final 

regulatory determinations for 11 of the 

51 CCL 2 contaminants in the FR on 

July 30, 2008 (73 FR 44251; USEPA, 

2008a). The agency determined not to 

regulate the following 11 contaminants: 

boron, the dacthal mono- and di-acid 

degradates, 1,1-dichloro-2,2-bis(pchlorophenyl)ethylene (DDE), 1,3- 

dichloropropene (Telone), 2,4- 

dinitrotoluene, 2,6-dinitrotoluene, Sethyl dipropylthiocarbamate (EPTC), 

fonofos, terbacil and 1,1,2,2- 

tetrachloroethane. The agency issued 

new or updated HAs for boron, dacthal 

degradates, 2,4-dinitrotoluene, 2,6- 

dinitrotoluene and 1,1,2,2- 

tetrachloroethane. 

4. The Third Contaminant Candidate 

List (CCL 3) and Regulatory 

Determination (RD 3) 

The agency published the final CCL 3, 

which listed 116 contaminants, in the 

FR on October 8, 2009 (74 FR 51850; 

USEPA, 2009a). In developing CCL 3, 

the EPA improved and built upon the 

process that was used for CCL 1 and 

CCL 2. The CCL 3 process was based on 

substantial expert input and 

recommendations from the National 

Academy of Sciences’ (NAS) National 

Research Council (NRC) and the 

National Drinking Water Advisory 

Council (NDWAC) as well as input from 

the public. Based on these consultations 

and input, the EPA developed a multistep process to select candidates for a 

final CCL, which included the following 

key steps: 

(a) Building a broad universe; 

(b) Screening the universe to select a 

Preliminary CCL (PCCL); and 

(c) Classification of PCCL chemicals 

to select a CCL. 

The agency published its preliminary 

regulatory determinations for 

contaminants listed on the CCL 3 in the 

FR on October 20, 2014 (79 FR 62715; 

USEPA, 2014). In that notice, the EPA 

made preliminary determinations for 

five of the 116 contaminants listed on 

the CCL 3, including a preliminary 

positive determination for strontium 

and preliminary negative 

determinations for dimethoate, 1,3- 

dinitrobenzene, terbufos and terbufos 

sulfone. On January 4, 2016 (81 FR 13; 

USEPA, 2016a), the EPA finalized the 

negative determinations for dimethoate, 

1,3-dinitrobenzene, terbufos and 

terbufos sulfone. The EPA announced a 

delay in issuing a final regulatory 

determination on strontium in order to 

consider additional data. Additional 

discussion on strontium is provided in 

section V of this document. 

The EPA also published an off-cycle 

final determination to regulate one CCL 

3 contaminant, perchlorate, on February 

11, 2011 (76 FR 7762; USEPA, 2011) 

during the RD 3 cycle (bringing the total 

number of final determinations to five). 

5. The Fourth Contaminant Candidate 

List (CCL 4) and Regulatory 

Determination (RD 4) 

The final CCL 4 was published on 

November 17, 2016 (81 FR 81099; 

USEPA, 2016b). The final CCL 4 

consisted of 97 chemicals or chemical 

groups and 12 microbiological 

contaminants. Most CCL 4 contaminants 

were carried over from CCL 3. The EPA 

added two contaminants (manganese 

and nonylphenol) to the CCL 4 list 

based on nominations. The EPA 

removed from the list those CCL 3 

contaminants that had been subject to 

recent preliminary or final regulatory 

determinations (perchlorate, 

dimethoate, 1,3-dinitrobenzene, 

terbufos, terbufos sulfone and 

strontium) and three pesticides with 

cancelled registrations (disulfoton, 

fenamiphos and molinate). 

The EPA published its preliminary 

determinations for the fourth CCL in the 

Federal Register on March 10, 2020 (85 

FR 14098; USEPA, 2020a). In that 

notice, the EPA made determinations for 

eight of the 109 contaminants on the 

CCL 4. The EPA determined to regulate 

two PFAS, perfluorooctanoic acid 

(PFOA) and perfluorooctanesulfonic 

acid (PFOS), and determined not to 

regulate six additional contaminants: 

1,1-dichloroethane, acetochlor, methyl 

bromide, metolachlor, nitrobenzene and 

Royal Demolition eXplosive (RDX). The 

EPA published its final regulatory 

determinations for these contaminants 

on March 3, 2021 (86 FR 12272; USEPA, 

2021a). 

6. The Fifth Contaminant Candidate List 

(CCL 5) 

The final CCL 5 was published on 

November 14, 2022 (87 FR 68060; 

USEPA, 2022a). The final CCL 5 

consists of 66 chemicals, 3 chemical 

groups (cyanotoxins, disinfection 

byproducts (DBPs) and PFAS) and 12 

microbial contaminants. The CCL 5 was 

developed based on the existing 

framework used for CCL 3 and CCL 4. 

For CCL 5, the EPA updated the CCL 

process to consider a larger number of 

contaminants, enhance transparency in 

the data evaluation, and improve 

efficiency of information transfer to 

other SDWA processes, such as 

regulatory determinations. 

III. Approach and Overall Outcomes 

for RD 5 

This section describes (a) the 

approach the EPA used to identify and 

evaluate contaminants for RD 5 along 

with the overall outcome of applying 

this approach, (b) the supporting RD 5 

documentation and (c) the technical 

analyses and sources of health and 

occurrence information. 

A. Summary of the Approach and 

Overall Outcomes for RD 5 

The approach taken under RD 5 is 

similar to that used in previous rounds 

of regulatory determination and 

formalized in a written protocol under 

RD 3. The Regulatory Determination 5 

Protocol, found in Appendix B of the 

Regulatory Determination 5 Support 

Document (USEPA, 2024b), like the RD 

3 and RD 4 Protocols, describes a threephase process. The three phases are: (1) 

the Data Availability Phase, (2) the Data 

Evaluation Phase and (3) the Regulatory 

Determination Assessment Phase. 

Figure 1 provides an overview of the 

process the EPA uses to identify which 

CCL 5 contaminants are candidates for 

regulatory determinations and the 

SDWA statutory criteria considered in 

making the regulatory determinations. 

For more detailed information on the 

three phases of the RD 5 process, refer 

to the RD 5 Protocol in Appendix B of 

the Regulatory Determination 5 Support 

Document (USEPA, 2024b). 

BILLING CODE 6560–50–P 


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6A health reference level (HRL) is a health-based 

concentration against which the agency evaluates 

occurrence data when making decisions about 

preliminary regulatory determinations. An HRL is 

not a final determination on establishing a 

protective level of a contaminant in drinking water 

for a particular population; it is derived prior to 

development of a complete health and exposure 

assessment. 

1. Phase 1 (Data Availability Phase) 

In Phase 1, the Data Availability 

Phase, the agency identifies 

contaminants that have sufficient health 

and occurrence data to proceed to Phase 

2 and be included on a ‘‘short list’’ for 

further evaluation. SDWA 

1412(b)(1)(B)(ii)(II) requires that the 

EPA consider the best available public 

health information in making the 

regulatory determination. 

To identify contaminant health effects 

data that are sufficient to make a 

regulatory determination regarding 

potential adverse health effect(s), the 

agency considers whether an EPA 

health assessment or an externally peerreviewed health assessment from 

another agency is available, from which 

a health reference level (HRL) 6

sufficient to inform a regulatory 

determination can be derived. See 

section III.C.1 of this document for 

information about how HRLs are 

derived. To identify ‘‘qualifying’’ health 

assessments, the EPA conducted a 

systematic search in January 2023 for 

the EPA and other authoritative sources 

of human health effects assessments for 

each drinking water chemical 

contaminant on CCL 5. Health 

assessments are considered qualifying if 

they (1) derived one or more toxicity 

values (e.g., oral reference value or oral 

cancer slope factor [CSF]) based on the 

best available science; (2) underwent a 

documented peer-review process; (3) are 

publicly available and final; (4) were 

developed using human health risk 

assessments methods that are 

comparable to current EPA human 

health risk assessment principles and 

approaches (e.g., a weight of evidence 

approach); and (5) are produced from an 

authoritative source that routinely 

develops health assessments (e.g., 

Agency for Toxic Substances and 

Disease Registry [ATSDR]). If a 

qualifying health assessment is not 

available for a contaminant, the 

contaminant will not proceed to Phase 

2. See section B.5.1.1 in Appendix B of 

the Regulatory Determination 5 Support 

Document for a list of sources of Health 

Effects Assessments (USEPA, 2024b). 

After identifying the qualifying peerreviewed health assessments for a 

chemical, the EPA followed a structured 

and transparent process to select the 

assessment(s) for both cancer and 

noncancer HRL derivation. The process 

included expert evaluations applying 

specific criteria. These criteria are 

designed to identify the assessment 

relevant to drinking water that was 

developed using comparable approaches 

to the EPA human health risk 

assessment methods and based on the 

best available science. The EPA used the 

results from the expert evaluations to 

select the health assessment used to 

derive the HRL for the chemical. In 

addition, the EPA applied expert 

judgement when evaluating a set of 

assessments for a given contaminant 

because certain health assessments and 

chemicals can present unique 

challenges. See section B.5.1.2 in 

Appendix B of the Regulatory 

Determination 5 Support Document for 


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Figure 1: The Three Primary Phases of the RD 5 Process 

Phase 3: 

Phase 1: Data Availability Regulatory Determination Assessment 
3836 Federal Register / Vol. 90, No. 9 / Wednesday, January 15, 2025 / Notices 

7Specific types of UCMR monitoring (e.g., 

assessment monitoring and sometimes the 

screening survey) are considered nationally 

representative. These are described further in 

Section III.C.2.a.1 of this notice. 

8Note that the 1⁄2 HRL threshold is based on a 

recommendation from the NDWAC working 

grouping that provided recommendations on the 

first regulatory determination effort (USEPA, 

2000a). 

the decision-logic that was applied for 

all RD 5 chemicals (USEPA, 2024b). 

To identify contaminant occurrence 

data that are sufficient to evaluate with 

respect to the frequency and level of 

occurrence in PWSs, the agency 

considers nationally representative 

finished drinking water data (samples 

collected after the water undergoes 

treatment) when available for making 

regulatory determinations. The 

following sources, administered or 

overseen by the EPA, include finished 

drinking water occurrence data that are 

considered nationally representative: (a) 

the fourth Unregulated Contaminant 

Monitoring Rule (UCMR 4); (b) the third 

Unregulated Contaminant Monitoring 

Rule (UCMR 3); (c) the second 

Unregulated Contaminant Monitoring 

Rule (UCMR 2); (d) the first Unregulated 

Contaminant Monitoring Rule (UCMR 

1); (e) the Unregulated Contaminant 

Monitoring (UCM) program; and (f) the 

National Inorganics and Radionuclides 

Survey (NIRS).7 If a contaminant has 

occurrence data from a nationally 

representative source, it passes the 

Occurrence Data Availability 

Assessment. 

If nationally representative drinking 

water data are not available, the EPA 

identifies and evaluates other sources of 

finished water data, which may include 

other national assessments, regional 

data, state data and more localized 

finished water assessments. For more 

information on sources of occurrence 

that may be evaluated during the 

regulatory determination process, please 

refer to Chapter 2 of the Regulatory 

Determination 5 Support Document 

(USEPA, 2024b). 

In Phase 1, the agency assesses 

whether the non-nationally 

representative finished water 

occurrence data show at least one 

detection at levels >1⁄2 the HRL 8 for the 

critical endpoint. If a contaminant 

without nationally representative 

finished water occurrence data has nonnationally representative finished water 

occurrence data showing at least one 

detection > 1⁄2 HRL, the contaminant 

passes the Occurrence Data Availability 

Assessment. While there may be robust 

non-national data available for certain 

contaminants which can demonstrate 

substantial likelihood of occurrence at a 

frequency and level of public health 

concern (e.g., see PFAS Federal Register 

Notice section III.C), the EPA does not 

rely on non-national data alone to 

determine that there is no or low 

potential for occurrence in the nation’s 

PWSs because these data tend to be 

limited in scope and do not provide a 

sufficiently accurate picture of 

occurrence to support a negative 

determination. 

If a widely available analytical 

method does not exist for monitoring 

occurrence of a contaminant in water, 

the contaminant will not be a viable 

candidate for regulation with a 

Maximum Contaminant Level (MCL). In 

certain limited cases, a contaminant’s 

occurrence data may have been gathered 

using a specialized or experimental 

method that is not in general use. In the 

Analytical Methods Availability 

Assessment, the EPA determines for 

each contaminant whether a widely 

available analytical method for 

monitoring, which employs technology 

that is commonly in use at numerous 

drinking water laboratories, exists. If a 

widely available analytical method 

exists, the contaminant passes the 

Analytical Methods Availability 

Assessment. If a widely available 

analytical method does not exist, the 

EPA may still advance the contaminant 

to Phase 2 if the agency determines that 

indicator or surrogate monitoring, or use 

of a treatment technique (TT), could 

allow for effective regulation and there 

is evidence of occurrence. 

The EPA also may consider issuing a 

regulatory determination for 

contaminant groups and/or mixtures 

that are a contaminant. The EPA has 

made final regulatory determinations for 

contaminant mixtures and regulated 

certain contaminants in drinking water 

collectively. For example, the EPA made 

a determination to regulate mixture 

combinations. containing two or more of 

the following PFAS: PFHxS PFNA, 

HFPO–DA (GenX chemicals), and PFBS. 

Additionally, the EPA has also 

established NPDWRs for groups of 

contaminants (e.g., DBPs; for total 

trihalomethanes [TTHMs] and the sum 

of five haloacetic acids [HAA5], as well 

as radionuclides). After conducting the 

health and occurrence data availability 

assessments, the agency identifies those 

contaminants and contaminant groups 

that meet the following Phase 1 data 

availability criteria: 

(a) An EPA health assessment or an 

externally peer-reviewed health 

assessment from another agency that 

conforms with the current EPA 

guidelines is available, from which an 

HRL can be derived; 

(b) Either nationally representative 

finished drinking water occurrence data 

are available or other finished water 

occurrence data show occurrence at 

levels >1⁄2 the HRL; and 

(c) A widely available analytical 

method for monitoring is available. 

If a contaminant or group meets these 

three criteria, it is placed on a ‘‘short 

list’’ and proceeds to Phase 2. After 

evaluating the 81 CCL 5 contaminants/ 

groups of contaminants and strontium 

in Phase 1, the agency identified 35 

contaminants to evaluate further in 

Phase 2 (contaminants listed in Table 1 

of this document). PFHxS, PFNA and 

HFPO–DA received final positive 

regulatory determinations in 

conjunction with the development of 

the PFAS NPDWR and therefore are not 

included in the contaminants 

considered here as part of the 

preliminary RD 5. For RD 5, the EPA set 

January 31, 2023 as a cutoff date for 

selection of health assessments. Health 

assessments published after this date 

were not considered in RD 5. 

TABLE 1—CONTAMINANTS PROCEEDING FROM PHASE 1 TO PHASE

2 

1,2,3-Trichloropropane. 

1,2,4-Trimethylbenzene. 

1,4-Dioxane. 

2-Aminotoluene (o-Toluidine). 

alpha-Hexachlorocyclohexane. 

Boron. 

Carbaryl. 

Chlorate. 

Cobalt. 

Cylindrospermopsin. 

Dieldrin. 

Dimethoate. 

Diuron. 

Ethoprop. 

Legionella pneumophila. 

Lithium. 

Manganese. 

Methomyl. 

Microcystins. 

Molybdenum. 

N-Nitrosodi-n-butylamine (NDBA). 

N-Nitrosodiethylamine (NDEA). 

N-Nitrosodimethylamine (NDMA). 

N-Nitroso-di-n-propylamine (NDPA). 

N-Nitrosopyrrolidine (NPYR). 

Perfluorobutanoic acid (PFBA). 

Permethrin. 

Profenofos. 

Propachlor. 

Quinoline. 

Strontium. 

Tebuconazole. 

Terbufos. 

Tribufos. 

Vanadium. 

The remaining CCL 5 contaminants 

listed in Chapter 2 of the Regulatory 

Determination 5 Support Document 

(USEPA, 2024b) did not meet one or 


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more of the Phase 1 data availability 

criteria described earlier in this section 

and were not considered further for RD 

5. 

2. Phase 2 (Data Evaluation Phase) 

(a) Evaluation of Adverse Health Effects 

This section describes the approach 

for deriving the HRL for the 

contaminants under consideration for 

regulatory determinations. HRLs are 

health-based drinking water 

concentrations against which the EPA 

evaluates occurrence data to determine 

if contaminants occur at levels of 

potential public health concern in 

drinking water. HRLs are not final 

values for establishing a protective level 

of a contaminant in drinking water for 

any particular population and are 

derived prior to the development of a 

complete health and exposure 

assessment for regulatory determination. 

More specific information about the 

potential for adverse health effects for 

each contaminant is presented in 

section IV.B of this action. 

(i) Derivation of an HRL 

There are two general approaches to 

the derivation of an HRL. One approach 

is used for chemicals with a threshold 

dose-response. For noncancer effects 

and non-linear carcinogens, HRLs are 

obtained by dividing the reference dose 

(RfD) (or equivalent, such as an ATSDR 

minimal risk level) by an exposure 

factor (EF) (i.e., drinking water intake 

rate adjusted for body weight [DWI– 

BW]) relevant to the target population 

and critical effect (USEPA, 2019a) and 

multiplying by a 20% relative source 

contribution (RSC) (USEPA, 2000a). 

Consistent with HRL development for 

previous regulatory determinations, 

HRLs derived for RD 5 are rounded to 

one significant figure. The RSC is used 

to account for exposure via nondrinking water routes in deriving 

health-based drinking water 

concentrations for contaminants with 

threshold effects (noncarcinogens and 

nonlinear carcinogens). A 20% RSC is 

used for all RD 5 contaminants, 

consistent with other regulatory 

determination cycles (USEPA, 2021a), to 

derive the noncancer HRL because (1) 

HRLs are developed prior to completing 

the exposure assessment; and (2) a 20% 

RSC is the lowest that is applied for 

deriving health-based drinking water 

concentrations, therefore resulting in 

the most health protective HRL (USEPA, 

2000a). Should a contaminant proceed 

to a NPDWR, a full exposure analysis is 

conducted and an RSC is derived 

following the Exposure Decision Tree 

approach described in the Methodology 

for Deriving Ambient Water Quality 

Criteria for the Protection of Human 

Health (USEPA, 2000a). 

HRLs for contaminants with a 

threshold dose-response (non-cancer 

and nonlinear cancer endpoints) are 

calculated as follows: 

The second general approach is used 

for chemicals that exhibit a linear, nonthreshold response to dose as is typical 

of carcinogens. For this approach, the 

HRL is calculated for one-in-a-million 

(10¥6) cancer risk expressed as a 

drinking water concentration. HRLs for 

contaminants with a linear doseresponse (typically cancer endpoints) 

are calculated as follows: 

In this second approach, when a 

carcinogen with a linear dose-response 

has a known mutagenic mode of action 

(MOA), the EPA follows the Cancer 

Guidelines (USEPA, 2005b) when 

deriving HRLs (USEPA, 2024b). For 

carcinogens with a MOA, the 2005 

Cancer Guidelines recommend 

consideration of increased risk due to 

early-life exposure. When chemicalspecific data to quantify the increased 

risk from developmental exposure are 

lacking, Age Dependent Adjustment 

Factors (ADAFs) are applied. The 

recommended ADAFs are a 10-fold 

adjustment for exposure during the 

interval from birth to <2 years (infant 

and toddler); a 3-fold adjustment for 

exposure from 2 to <16 years (childhood 

and adolescence); and no additional 

adjustment for exposures for 16 years to 

70 years of age. In cases where the MOA 

cannot be determined, the default lowdose linear extrapolation approach 

without ADAFs (described earlier in 

this section) is used. 

HRLs for carcinogenic contaminants 

with a known mutagenic MOA are 

calculated as follows: 

The following terms are used in these 

questions: 

HRL = Health Reference Level (mg/L), a 

non-regulatory health-based drinking water 

concentration levels of a specific 

contaminant at or below which is not 

anticipated to lead to adverse human health 

effects. 

RfD = Reference Dose (mg/kg/day)—an 

estimate (with uncertainty spanning perhaps 

an order of magnitude) of a daily oral 

exposure of the human population to a 

substance that is likely to be without an 

appreciable risk of deleterious effects during 

a lifetime. The value of this parameter is 

derived in the selected qualifying health 

assessment and is based on the critical effect 

and study identified in that assessment. An 

RfD is considered an oral reference value for 

RD 5 and can also refer to the maximum 

acceptable concentration (MAC), ATSDR 

minimal risk level, point of departure (POD)/ 

uncertainty factor (UF), population-adjusted 

dose (PAD) or tolerable daily intake (TDI). 

DWI–BWi = Drinking water intake (DWI), 

adjusted for body weight (BW), in units of 

liter per kilogram BW per day (L/kg/day) for 

each age group (i). 

RSC = Relative Source Contribution—the 

percentage of the total exposure attributed to 

drinking water sources (USEPA, 2000a) 

where the remainder of the exposure is 

allocated to other routes or sources. 

CSF = Cancer Slope Factor (mg/kg/ 

day)¥1,—an upper-bound estimate of risk per 

increment of dose that can be used to 

estimate cancer risk probabilities for different 

exposure levels (USEPA, 2005b). 

CRL = Cancer risk level,—the target 

incidence used to establish lifetime exposure 

limits for carcinogens, set at one excess 

cancer case in a population of one million (1 

× 10¥6). 

ADAFi = the age dependent adjustment 

factor for each age group (i), used when 

calculating cancer risk concentrations for 

carcinogens that act via a mutagenic MOA; 

by default, ADAF = 10 from birth to two 

years of age; ADAF = 3 from two to sixteen 

years of age; and ADAF = 1 from 16 to 70 

years of age (USEPA, 2005b). 

UA = Unit adjustment factor to convert the 

dose (i.e., CSF) from mg of a chemical to mg 

of the chemical—ensures the ADAF-adjusted 

Unit Risk is in mg/L. This unit adjustment is 

not needed if the CSF is presented in (ug/kg/ 

day)¥1 or if the desired units of the ADAFadjusted concentration (i.e., HRL) is mg/L. A 

different adjustment factor is needed for 

other units. 

Fi = the fraction of life spent in each age 

group (i), used when calculating cancer risk 

concentrations for mutagens (USEPA, 2005b). 

In some cases, the health assessments 

identified for HRL derivation provided 

both cancer and non-cancer toxicity 

values (e.g., an oral reference value and 

oral CSF). When this situation occurred, 

the EPA selected the health assessments 


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CRL 

HRL = CSF * DWI-BW 

RfD 

HRL = DWI-BW * RSC 

CRL 

HRL = -------------

"i.iCCSF * ADAFi * DWI-BWi * UA * Fa 
3838 Federal Register / Vol. 90, No. 9 / Wednesday, January 15, 2025 / Notices 

9The MRL is the minimum concentration that is 

required to be reported quantitatively in a study. 

The MRL is set at a value that takes into account 

typical laboratory capabilities to reliably and costeffectively detect and quantify a compound. 

10Note that other finished water data (i.e., nonnationally-representative occurrence data) tend to 

be limited in scope and the EPA does not use these 

data alone to support a determination that the 

contaminant is not substantially likely to ‘‘occur in 

PWSs with a frequency and at levels of public 

health concern,’’ which would therefore be a 

decision ‘‘not to regulate’’ (i.e., negative 

determination). 

according to the criteria explained 

earlier in this section, derived a 

noncancer HRL and a cancer HRL based 

on noncancer and cancer health effects 

information, respectively, and then 

selected the most health protective (i.e., 

lowest value) to serve as the final HRL 

(USEPA, 2000a). 

(ii) Exposure Factor Selection Process 

for HRL Derivation 

In prioritizing the contaminants of 

greatest public health concern for 

regulatory determination, section 

1412(b)(1)(C) of SDWA requires the 

agency to consider ‘‘among other factors 

of public health concern, the effect of 

such contaminants upon subgroups that 

comprise a meaningful portion of the 

general population (such as infants, 

children, pregnant women, the elderly 

or other subpopulations) that are 

identifiable as being at greater risk of 

adverse health effects due to exposure to 

contaminants in drinking water 

compared to the general population.’’ It 

is also the EPA’s policy to ‘‘protect 

children from environmental exposures 

by consistently and explicitly 

considering early life exposures and 

lifelong health in human health 

decisions’’ (USEPA, 2021b). One way 

that the EPA considers potentially 

sensitive populations or life stages (i.e., 

populations or life stages that may be 

more susceptible or sensitive to a 

chemical exposure) is during the 

selection of EFs for the development of 

HRLs. 

DWI–BW is the EF used to derive 

HRLs for RD 5 (USEPA, 2019a). EFs are 

input values intended to protect the 

general population including sensitive 

populations or life stages from adverse 

effects resulting from exposure to a 

contaminant. The agency selects an 

appropriate DWI–BW for each chemical 

by reviewing the critical effect and 

study used for HRL derivation and 

identifying the interval of exposure (for 

examples, see USEPA, 2022b; USEPA, 

2022c). The critical effect used as the 

basis for the oral reference value or oral 

CSF typically represents the health 

outcome at the lowest dose from the 

critical study among the best available 

studies. Since the critical effect 

typically represents the most sensitive 

adverse effect observed based on the 

available published data for a given 

chemical, it is reasonable to assume that 

the interval of exposure in the critical 

study could inform the selection of a 

DWI–BW protective of sensitive 

populations. Therefore, the EPA uses 

the interval of exposure in the critical 

study to identify potentially sensitive 

life stages as the basis for EF selection. 

When multiple potentially sensitive 

populations or life stages are identified 

based on the interval of exposure in the 

study used for HRL derivation, the EPA 

selects the population or life stage with 

the highest DWI–BW because it is the 

most health protective. See section 

B.6.1.2 in Appendix B of the Regulatory 

Determination 5 Support Document for 

more information regarding the EPA’s 

EF selection process (USEPA, 2024b). 

(b) Occurrence Data Evaluation 

In Phase 2, the agency collects 

additional data on occurrence 

(including finished drinking water data; 

ambient water data; data on use, 

production and release; and information 

on environmental fate and transport) 

and more thoroughly evaluates this 

information (based on factors 

enumerated in the following 

paragraphs) to identify contaminants 

that should proceed to Phase 3. 

In Phase 2, the agency focuses its 

efforts on identifying those 

contaminants or contaminant groups 

that are occurring or have substantial 

likelihood to occur at levels and 

frequencies of public health concern in 

drinking water. As noted in section 

III.A, SDWA 1412(b)(1)(C) requires that 

the Administrator select contaminants 

that present the greatest public health 

concern. To identify such contaminants, 

the agency considers the following 

information: 

(a) How many samples (number and 

percentage) have detections > HRL and 

1⁄2 HRL in the nationally representative 

and other finished water occurrence 

data? 

(b) How many systems (number and 

percentage) have detections > HRL and 

1⁄2 HRL in the nationally representative 

and other finished water occurrence 

data? 

(c) Are there uncertainties or 

limitations with the data or analyses, 

such as the age of the dataset, the 

reporting threshold (i.e., minimum 

reporting level [MRL 9] > HRL), or 

representativeness of the data (e.g., 

limited to a specific region), that may 

cause over- or underestimation of 

occurrence in finished water at levels 

and frequency of public health concern? 

After identifying contaminants that 

are occurring at levels and frequencies 

of public health concern in drinking 

water to proceed to Phase 3 for a 

potential positive determination, the 

agency evaluates the remaining 

contaminants on the ‘‘short list’’ to 

determine which contaminants have no 

or low occurrence at levels of health 

concern that should proceed to Phase 3 

for a potential negative determination. 

The agency considers the following 

information in selecting contaminants of 

no or low potential for public health 

concern to proceed to Phase 3: 

(a) Does the contaminant have 

nationally representative finished 

drinking water data showing no or a low 

number or percent of detections > HRL? 

(b) If a contaminant has other finished 

water data in addition to nationally 

representative finished water data, do 

these data suggest that there is no or low 

potential for occurrence in drinking 

water? 10

(c) Does additional high-quality 

occurrence information support the 

conclusion that there is low or no 

occurrence or potential for occurrence 

in drinking water? For example, is the 

occurrence in ambient/source water at 

levels below the HRL? How are releases 

to the environment or use/production 

changing over time? 

(d) Are critical gaps in health and 

occurrence information/data minimal? 

After evaluating the ‘‘short list’’ 

contaminants (listed in Table 1 of this 

document), the agency identified 14 

CCL 5 contaminants to proceed to Phase 

3 (listed in Table 2 of this document). 

The contaminants are within one of the 

following Phase 2 data evaluation 

categories: 

(a) A contaminant or part of a 

contaminant group occurring or likely to 

occur at levels and frequencies of public 

health concern, or 

(b) A contaminant not occurring or 

not likely to occur at levels and 

frequencies of public health concern 

and no data gaps. 


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TABLE 2—CONTAMINANTS PROCEEDING FROM PHASE 2 TO PHASE 3 

1,2,3-Trichloropropane. Molybdenum. 

1,4-Dioxane. Permethrin. 

2-Aminotoluene (o-Toluidine). Profenofos. 

Cylindrospermopsin. Quinoline. 

Ethoprop. Strontium. 

Manganese. Tebuconazole. 

Microcystins. Tribufos. 

Note that the agency does not have a 

threshold for occurrence in drinking 

water that triggers whether a 

contaminant is occurring with a 

frequency and at levels of public health 

concern. An evaluation of this statutory 

criterion requires consideration of a 

number of factors, some of which 

include the health effect(s), the potency 

of the contaminant, the level at which 

the contaminant is found in drinking 

water, the frequency at which the 

contaminant is found, the geographic 

distribution (national, regional or local 

occurrence), other possible sources of 

exposure, and potential impacts on 

sensitive populations or lifestages. 

Given the many possible combinations 

of factors, a simple threshold is not 

viable. 

The remaining CCL 5 contaminants 

did not proceed to Phase 3 and were not 

considered for RD 5 for reasons that may 

include of one or more of the following 

reasons: 

(a) An updated health assessment 

completed by January 31, 2023 was not 

identified; 

(b) Critical health effects gap (e.g., 

lack of data to support quantification for 

the oral route of exposure); 

(c) Lack of nationally representative 

finished water occurrence data and lack 

of sufficient other data to demonstrate 

occurrence at levels and frequencies of 

public health concern; 

(d) Critical occurrence data limitation 

or gap (e.g., inconsistent results or 

trends in occurrence data requiring 

further research; significant uncertainty 

in occurrence analyses or data); 

or 

(e) The contaminant is being 

evaluated in other actions by the 

agency. 

The agency continues to conduct 

research and collect information to fill 

the data and information gaps identified 

for these contaminants. Three 

contaminants that had previously 

received negative regulatory 

determinations have been re-listed on 

CCL 5 based on new health or 

occurrence information or a 

reevaluation of existing information. 

The EPA made determinations not to 

regulate dieldrin and manganese in RD 

1 and dimethoate in RD 3. These 

contaminants were considered in RD 5. 

Based on preliminary RD 5 evaluations 

of dieldrin and dimethoate, the EPA is 

not proposing a change to its previous 

negative regulatory determinations for 

these two contaminants at this time. 

Manganese is further discussed in 

section V. Additionally, all 29 PFAS 

contaminants that have approved 

analytical methods are being monitored 

under the fifth Unregulated 

Contaminant Monitoring Rule (UCMR 

5). The UCMR 5 occurrence data 

collection began in 2023 and ends in 

2025. 

3. Phase 3 (Regulatory Determination 

Assessment Phase) 

Phase 3, the Regulatory Determination 

Assessment Phase, involves a complete 

evaluation of the statutory criteria for 

each contaminant or group of 

contaminants that proceed from Phase 2 

and have sufficient information and 

data for making a regulatory 

determination. To meet the statutory 

requirement of making at least five 

regulatory determinations, in this phase, 

the agency evaluates the remaining 

contaminants against the following 

statutory criteria (SDWA 1412(b)(1)(A)): 

(a) Statutory Criterion 1—‘‘The 

contaminant may have an adverse effect 

on the health of persons.’’ To evaluate 

the first criterion, the EPA evaluates 

whether a contaminant has an EPA 

health assessment, or an externally peerreviewed health assessment from 

another agency that is publicly available 

and conforms with current EPA 

guidelines, from which an HRL can be 

derived. The HRL derived in or from the 

health assessment takes into account the 

MOA, the critical health effect(s), the 

dose-response relationship for critical 

health effect(s) and impacts on sensitive 

population(s) or lifestages. 

If an acceptable health assessment 

that demonstrates adverse health effects 

is available, the agency answers ‘‘yes’’ to 

the first statutory criterion. Otherwise, 

the agency answers ‘‘no’’ to the first 

statutory criterion. (In practice, it is 

expected that any contaminant that 

reaches Phase 3 would receive a ‘‘yes’’ 

to the first criterion.) 

(b) Statutory Criterion 2—‘‘The 

contaminant is known to occur or there 

is a substantial likelihood that the 

contaminant will occur in PWSs with a 

frequency and at levels of public health 

concern.’’ The EPA compares the 

occurrence data for each contaminant to 

the HRL to determine if the contaminant 

occurs at a frequency and levels of 

public health concern. The types of 

occurrence data used at this stage are 

described in section III.C.1, Evaluation 

of Contaminant Occurrence and 

Exposure, and in Appendix B of the 

Regulatory Determination 5 Support 

Document (USEPA, 2024b). The agency 

may consider the multiple factors when 

identifying contaminants or 

contaminant groups that are occurring at 

frequencies and levels of public health 

concern, including: 

• How many samples (number and 

percentage) have detections > HRL in 

the nationally representative and other 

finished water occurrence data? 

• How many systems (number and 

percentage) have detections > HRL in 

the nationally representative and other 

finished water occurrence data, and, in 

addition to the number of systems, what 

type of systems does the contaminant 

occur in? Does the contaminant occur in 

large or small systems? Does the 

contaminant occur in surface or 

groundwater systems? 

• Is the geographic distribution of the 

contaminant occurrence national, 

regional or localized? 

• Are there significant uncertainties 

or limitations with the data or analyses, 

such as the age of the dataset, the MRL 

(i.e., MRL > HRL), or representativeness 

of the data (e.g., limited in scope to a 

specific region)? 

(c) Statutory Criterion 3—‘‘In the sole 

judgment of the Administrator, 

regulation of the contaminant presents a 

meaningful opportunity for health risk 

reduction for persons served by public 

water systems.’’ The EPA evaluates the 

population exposed at the health level 

of concern along with several other 

factors to determine if regulation 

presents a meaningful opportunity for 

health risk reduction. Among other 

things, the EPA may consider the 

following factors in evaluating statutory 

criterion 3: 


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11 If appropriate and available, the agency 

considers quantitative exposure data applicable to 

sensitive populations or lifestages when deriving 

HRLs for regulatory determinations. When data are 

not available on sensitive populations, the 

derivation of the RfD typically includes an 

uncertainty factor to account for the limitation in 

the database. Additionally, the EPA will use 

exposure factors relevant to the sensitive 

population in deriving the HRL. See Section III.C.1. 

Sensitive populations are also qualitatively 

considered by providing national prevalence 

estimates for a particular sensitive population, if 

available. 

12The statute authorizes a nine-month extension 

of this promulgation date. 

• What is the nature of the health 

effect(s) identified in statutory criterion 

1? 

• Are there sensitive populations that 

may be affected (evaluated either 

qualitatively or quantitatively 11)? 

• Based on the occurrence 

information for statutory criterion 2, 

including the number of systems 

potentially affected, what is the national 

population exposed or served by 

systems with levels > HRL and >1⁄2

HRL? 

• For non-carcinogens, are there other 

sources of exposure that should be 

considered (i.e., what is the RSC from 

drinking water)? 

• What is the geographic distribution 

of occurrence (e.g., local, regional, 

national)? 

• Are there any uncertainties or 

limitations in the health and occurrence 

information or analyses that should be 

considered? 

• Are there any limiting 

considerations related to technology 

(e.g., lack of available treatment or 

analytical methods)? 

If the Administrator, in their sole 

judgement, determines that there is a 

meaningful opportunity to reduce risk 

by regulating the contaminant in 

drinking water, then the agency answers 

‘‘yes’’ to the third statutory criterion. 

The agency may make a positive 

preliminary determination if the agency 

answers ‘‘yes’’ to all three statutory 

criteria in Phase 3 for a particular 

contaminant. Additionally, after 

identifying compounds occurring at 

frequencies and levels of public health 

concern, if any, the agency may initiate 

a systematic literature review to identify 

new studies that may influence the 

derivation of an RfD or CSF. The list of 

potentially relevant health effect studies 

that could affect the derivation of an 

RfD or CSF identified through the 

systematic review process would then 

be placed in the docket at the time of 

the preliminary determination for 

public comment (discussed further in 

section IV of this document). 

If, after considering public comment 

on the preliminary regulatory 

determination, the agency again answers 

‘‘yes’’ to all three statutory criteria, the 

agency then may make a positive final 

determination that regulation is 

appropriate and proceed to develop an 

MCLG and NPDWR. If a final positive 

determination is made, the agency has 

24 months to publish a proposed MCLG 

and NPDWR and an additional 18 

months to publish a final MCLG and 

promulgate a final NPDWR.12

It should be noted that the analyses 

associated with a regulatory 

determination process are distinct from 

the more detailed analyses needed to 

develop an NPDWR. The development 

and promulgation of an NPDWR is a 

multi-step process, which includes 

deriving a proposed MCLG as well as 

conducting a statutorily required health 

risk reduction cost analysis (HRRCA) 

and conducting other analyses required 

to propose an MCL or a TT approach to 

reduce contaminant levels in water 

systems. As part of the proposal, the 

agency must identify best available 

technologies (BATs), small system 

compliance technologies (SSCTs) and 

approved analytical methods if it 

proposes an enforceable MCL. 

Alternatively, if the EPA proposes a TT 

instead of an MCL, the agency must 

identify the TT. The EPA must also 

prepare a HRRCA which includes an 

extensive evaluation of the treatment 

costs and monitoring costs at a system 

level and aggregated at the national 

level. Thus, a decision to regulate is the 

beginning of the agency’s regulatory 

development process, not the end. 

If a contaminant has sufficient 

information and the agency answers 

‘‘no’’ to any of the three statutory 

criteria based on the available data, then 

the agency considers making a negative 

determination that an NPDWR is not 

appropriate for that contaminant at that 

time. A final determination not to 

regulate a contaminant is, by statute, a 

final agency action and is subject to 

judicial review. While a negative 

determination is considered a final 

agency action under SDWA for a round 

of regulatory determinations, the 

contaminant may be relisted on a future 

CCL based on newly available health or 

occurrence information. 

If a negative determination or no 

determination is made for a 

contaminant, the agency may decide to 

develop an HA, which provides nonregulatory concentration values for 

drinking water contaminants at which 

adverse health effects are not 

anticipated to occur over specific 

exposure durations (e.g., one day, ten 

days, or a lifetime). The EPA’s HAs are 

non-enforceable and non-regulatory and 

provide technical information to states’ 

agencies and other public health 

officials on health effects, analytical 

methodologies and treatment 

technologies associated with drinking 

water contamination. See SDWA section 

1412(b)(1)(F). 

After evaluating the CCL 5 

contaminants in Table 3 of this 

document against the three SDWA 

criteria and considering the factors 

listed for each, the agency is making 

preliminary negative regulatory 

determinations for nine CCL 5 

contaminants. Table 5 of this 

documentprovides a summary of the 14 

contaminants evaluated for Phase 3 and 

the preliminary regulatory 

determination outcome for each 

contaminant. The agency seeks 

comment on the preliminary 

determination not to regulate nine 

contaminants (2-aminotoluene, 

cylindrospermopsin, ethoprop, 

microcystins, molybdenum, permethrin, 

profenofos, tebuconazole and tribufos). 

Section IV.B of this document provides 

a more detailed summary of the 

information and the rationale used by 

the agency to reach its preliminary 

decisions for these contaminants. At 

this time, the agency is not making 

preliminary regulatory determinations 

for five of the 14 contaminants that 

proceeded to Phase 3, namely1,2,3- 

trichloropropane (1,2,3-TCP), 1,4- 

dioxane, manganese, quinoline and 

strontium (see section V of this 

document for more information). 

TABLE 3—CONTAMINANTS EVALUATED IN PHASE 3 AND THE REGULATORY DETERMINATION OUTCOME

Number Contaminant Preliminary determination outcome 

1 .................... 2-Aminotoluene (o-Toluidine) ...................................................... Negative Determination. 

2 .................... 1,2,3-Trichloropropane ................................................................ No Determination. 

3 .................... 1,4-Dioxane ................................................................................. No Determination. 

4 .................... Cylindrospermopsin .................................................................... Negative Determination. 


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TABLE 3—CONTAMINANTS EVALUATED IN PHASE 3 AND THE REGULATORY DETERMINATION OUTCOME—Continued 

Number Contaminant Preliminary determination outcome 

5 .................... Ethoprop ...................................................................................... Negative Determination. 

6 .................... Manganese ................................................................................. No Determination.

7 .................... Microcystins ................................................................................ Negative Determination. 

8 .................... Molybdenum ................................................................................ Negative Determination. 

9 .................... Permethrin ................................................................................... Negative Determination. 

10 .................. Profenofos ................................................................................... Negative Determination. 

11 .................. Quinoline ..................................................................................... No Determination. 

12 .................. Strontium ..................................................................................... No Determination. 

13 .................. Tebuconazole .............................................................................. Negative Determination. 

14 .................. Tribufos ....................................................................................... Negative Determination. 

In National Resources Defense 

Council v. Michael S. Regan, 

Administrator, U.S. Environmental 

Protection Agency and Environmental 

Protection Agency (NRDC v. EPA), 67 

F.4th 397 (D.C. Cir., 2023), the D.C. 

Circuit Court of Appeals ruled that 

when the EPA finalizes a positive 

regulatory determination for a 

contaminant under the SDWA, the EPA 

must then promulgate a regulation and 

the EPA does not have the ability to 

withdraw a final positive determination 

during the development of the proposed 

rule. This ruling presents a change to 

the EPA’s understanding of the 

flexibilities afforded to the agency under 

the SDWA. Prior to this ruling, the EPA 

had understood that the agency could 

withdraw a positive determination if, 

during the more-detailed analyses 

conducted during the development of 

the proposed rule, for example, in the 

HRRCA, the EPA determined that the 

potential for health-risk reduction was 

less beneficial than initially predicted. 

Following the NRDC v. EPA ruling and 

the understanding now of the EPA’s 

authorities under the SDWA, the agency 

will need to be more certain of the 

potential for health-risk reduction 

through regulation before making a 

determination to regulate a 

contaminant. As a result, the EPA will 

need to consider preliminary health 

benefits analysis information to support 

the finding that a positive determination 

would provide a meaningful 

opportunity for health risk reduction if 

the agency decides to regulate a 

contaminant under the SDWA. 

Therefore, the EPA is not making a 

regulatory determination for these five 

contaminants at this time, in order to 

gain an understanding of the potential 

for health-risk reduction by conducting 

additional analyses of the potential 

benefits and treatment feasibility prior 

to making positive determinations. 

B. Supporting Documentation for the 

EPA’s Preliminary Determination 

For this action, the EPA prepared 

several supporting documents that are 

available for review and comment in the 

EPA Water Docket. These support 

documents include: 

• The comprehensive regulatory 

support document, Regulatory 

Determination 5 Support Document 

(USEPA, 2024b), summarizes the 

information and data evaluated by the 

EPA on the physical and chemical 

properties, uses and environmental 

release, environmental fate, potential 

health effects, occurrence and exposure 

estimates, analytical methods, treatment 

technologies and preliminary 

determinations. Additionally, Appendix 

B of the Regulatory Determination 5 

Support Document describes the 

approach implemented by the agency to 

evaluate the CCL 5 contaminants in a 

three-phase process and select the 

contaminants for preliminary 

determinations for RD 5. 

• A comprehensive technical 

occurrence support document for UCMR 

4, Occurrence Data from the Fourth 

Unregulated Contaminant Monitoring 

Rule (UCMR 4) (USEPA, 2024c). This 

occurrence support document includes 

more detailed information about UCMR 

4, how the EPA assessed the data 

quality, completeness and 

representativeness, and how the data 

were used to generate estimates of 

drinking water contaminant occurrence 

in support of these regulatory 

determinations. 

C. Analyses Used To Support the 

Preliminary Regulatory Determinations 

1. Evaluation of Contaminant 

Occurrence and Exposure 

The EPA uses data from many sources 

to evaluate occurrence and exposure 

from drinking water contaminants. The 

discussion in this section focuses 

mainly on the following sources of 

finished drinking water occurrence data: 

• Unregulated Contaminant 

Monitoring Rules (UCMR 1, 2, 3 and 4); 

• UCM-State Program Rounds 1 and 

2; and, 

• Data collected by states. 

Several of the primary sources of 

finished water occurrence data are 

designed to be statistically 

representative of the nation. These data 

sources include Assessment Monitoring 

(AM) data collected under UCMR 1–4 

and Screening Survey (SS) data 

collected under UCMR 2 and 3. 

The agency also evaluates 

supplemental sources of information on 

occurrence in drinking water, 

information on occurrence in ambient 

and source water and information on 

contaminant production and release to 

augment and complement these primary 

sources of drinking water occurrence 

data. section III.C.1.a of this action 

provides a brief summary of the primary 

sources of finished water occurrence 

data and sections III.C.1.b and III.C.1.c 

provide brief summary descriptions of 

some of the supplemental sources of 

occurrence information and data. These 

descriptions do not cover all the sources 

that the EPA reviews and evaluates. For 

individual contaminants, the EPA 

reviews additional published reports 

and peer-reviewed studies that may 

provide the results of monitoring efforts 

in limited geographic areas. A summary 

of the occurrence data and the results or 

findings for each of the contaminants 

considered for regulatory determination 

is presented in section IV.B, the 

contaminant profiles section, and the 

data are described in further detail in 

the Regulatory Determination 5 Support 

Document (USEPA, 2024b). 

(a) Primary Sources of Finished 

Drinking Water Occurrence Data 

The following section provides a brief 

summary of the finished water 

occurrence data sources used in RD 5. 

Table 4 in section IV of this document 

lists the primary data source/finding 

used to evaluate each of the nine 

contaminants for which the EPA is 

making preliminary determinations in 

this Federal Register Notice. The 


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13Section 1445 of the Safe Drinking Water Act 

was recently amended by Public Law 115–270, 

America’s Water Infrastructure Act of 2018 (AWIA), 

and now specifies that, effective October 23, 2021, 

subject to the availability of appropriations for such 

purpose and appropriate laboratory capacity, the 

EPA must require all systems serving between 3,300 

and 10,000 persons to monitor and ensure that only 

a representative sample of systems serving fewer 

than 3,300 persons are required to monitor. 

contaminant-specific discussions in 

section IV of this document, provide 

more detailed information about the 

primary data source findings as well as 

any supplemental occurrence 

information. 

Section V of this document provides 

more information about the five Phase 3 

contaminants for which the EPA is not 

making a preliminary regulatory 

determination at this time: 1,4-dioxane, 

1,2,3–TCP, manganese, quinoline and 

strontium. 

• The Unregulated Contaminant 

Monitoring Rules (UCMR 1, UCMR 2, 

UCMR 3 and UCMR 4) 

The UCMR program is the EPA’s 

primary vehicle for collecting 

monitoring data on the occurrence of 

unregulated contaminants in PWSs. 

SDWA section 1412 (b)(1)(B)(ii)(II) 

requires that the EPA include 

consideration of the data collected by 

the UCMR program in making 

regulatory determinations. The UCMR 

program is designed to collect 

nationally representative occurrence 

data in coordination with the CCL and 

regulatory determination processes. The 

UCMR sampling is limited by statute to 

no more than 30 contaminants every 

five years (SDWA section 1445(a)(2)). 

However, the National Defense 

Authorization Act for Fiscal Year 2020 

provided a one-time exception to this 

limit by stating that PFAS monitored 

under UCMR 5 do not count toward the 

limit of 30 contaminants. The EPA 

published the lists and requirements for 

UCMR 1 on September 17, 1999 (64 FR 

50556; USEPA, 1999), and the 

monitoring was conducted primarily 

during 2001–2005. The requirements for 

UCMR 2 were published on January 4, 

2007 (72 FR 367; USEPA, 2007) with 

monitoring conducted primarily during 

2008–2010. Requirements for UCMR 3 

were published on May 2, 2012 (77 FR 

26072; USEPA, 2012a); with monitoring 

conducted primarily during 2013–2015. 

Requirements for UCMR 4 were 

published on December 20, 2016 (81 FR 

92666; USEPA, 2016c) with monitoring 

conducted primarily during 2018–2020. 

(The complete contaminant lists are 

available at: https://www.epa.gov/ 

dwucmr.) On December 27, 2021, the 

EPA published UCMR 5, requiring 

certain PWSs to collect national 

occurrence data for 29 PFAS and 

lithium from 2023 through 2025 (86 FR 

73131; USEPA, 2021c). The final UCMR 

5 dataset is not complete at the time of 

these RD 5 preliminary determinations 

and will not conclude until December 

31, 2026. 

The UCMR program is designed as a 

three-tiered approach for monitoring 

contaminants related to the availability 

and complexity of analytical methods, 

laboratory capacity, sampling frequency, 

relevant PWSs based on contaminants 

and other considerations (e.g., cost/ 

burden). AM is the primary tier and the 

largest in scope. The AM generally 

relies on analytical methods that use 

more common techniques and are 

expected to be widely available. SS 

monitoring is smaller in scope than the 

AM and generally pertains to 

monitoring with less established 

analytical techniques, such that 

laboratory capacity or cost may be a 

concern. A Pre-Screen Testing (PST) tier 

can be customized to meet specific 

monitoring objectives for a specific 

group of PWSs. 

The EPA designed the AM sampling 

frame to ensure that sample results 

would support a high level of 

confidence and a low margin of error 

(see USEPA, 1999 and 2001a, for UCMR 

design details). The AM program 

includes PWSs from all 50 states, the 

District of Columbia, all five U.S. 

territories and Tribal lands across the 

EPA regions. The AM is required for all 

large and very large PWSs, those serving 

between 10,001 and 100,000 people and 

serving more than 100,000 people, 

respectively (i.e., a census of all large 

and very large systems) and a national 

statistically representative sample of 

800 small PWSs, those serving 10,000 or 

fewer people.13 The small system 

sample is stratified and populationweighted and includes some other 

sampling adjustments such as allocating 

a selection of at least two systems from 

each state for spatial coverage. The 

design meets the data quality objective 

for overall exposure estimates (99% 

confidence level with ±1% error 

tolerance, at 1% exposure) while 

providing more precise occurrence 

estimates for categories of small 

systems. The AM, the primary tier, has 

been used for all or a subset of 

contaminants in each UCMR cycle. With 

contaminant monitoring data from all 

large PWSs and a statistical, nationally 

representative sample of small PWSs, 

AM provides a robust dataset for 

evaluating national drinking water 

contaminant occurrence. 

Each system conducts monitoring for 

12 consecutive months during the threeyear monitoring period. The rules 

typically require quarterly monitoring 

for surface water and groundwater 

under the direct influence of surface 

water (GWUDI) systems and twice-ayear, six-month-interval monitoring for 

groundwater systems, and include 

flexibilities for specialized sampling 

(e.g., eight sample events for 

cyanotoxins in UCMR 4). Samples may 

be collected at different sampling points 

or locations within the PWS depending 

on the specific contaminant (e.g., entry 

point to the distribution system). A brief 

outline of the structure of the UCMR 

efforts is provided in the paragraphs 

that follow. 

UCMR 1 included both the AM and 

SS tiers. UCMR1 a.m. was conducted by 

approximately 3,100 large systems and 

approximately 800 small systems and 

resulted in over 33,900 sample results 

for each contaminant. The UCMR 1 SS 

design included approximately 640 

UCMR1 SS PWSs randomly selected 

from those PWSs required to conduct 

AM and was designed to determine if 

additional monitoring would be needed. 

Samples from the 639 PWSs from 

throughout the nation provided over 

2,300 results for each contaminant. 

While the statistical design of the SS is 

national in scope, the uncertainty in the 

results for contaminants that have low 

occurrence is relatively high. Therefore, 

the EPA looked for additional data to 

supplement the SS data for regulatory 

determinations in RD 2. After UCMR 1, 

the SS design was adapted to include 

more PWSs and to be representative of 

national occurrence. 

UCMR 2 also included the AM and SS 

tiers. The UCMR 2 a.m. was conducted 

by approximately3,300 large systems 

and 800 small systems and resulted in 

over 32,000 sample results for each 

contaminant. For the UCMR 2 SS, the 

EPA improved the design to include a 

census of all systems serving more than 

100,000 people, a nationally 

representative, statistically selected 

sample of 320 PWSs serving between 

10,001 and 100,000 people, and a 

nationally representative sample 

including approximately 480 small 

PWSs serving 10,000 or fewer people 

(72 FR 367, January 4, 2007, USEPA, 

2007). With a total of approximately 

1,200 systems participating in the SS, 

sufficient data were generated to 

provide a confident national estimate of 

contaminant occurrence and population 

exposure. The UCMR 2 SS PWSs 

provided between 11,100 to 18,100 

sample results per contaminant 

(depending on the specific sampling 

design for the contaminant). 

UCMR 3 included the AM, SS and 

PST tiers. The UCMR 3 a.m. was 

conducted by approximately 4,100 large 


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systems and approximately 800 small 

systems and resulted in between 36,800 

and 63,000 sample results for each 

contaminant (depending on the specific 

sampling design for the contaminant). 

The UCMR 3 SS monitoring was 

conducted by all large systems serving 

more than 100,000 people, a nationally 

representative sample of 320 large 

systems serving 10,001 to 100,000 

people and a nationally representative 

sample of approximately 480 small 

water systems serving 10,000 or fewer 

people for a total of approximately 1,200 

PWSs. The UCMR 3 SS PWSs provided 

over 11,700 sample result per 

contaminant. The UCMR 3 PST 

monitoring was conducted by 

approximately 800 PWSs including, 

transient noncommunity water systems 

that purchase all their finished water 

from another. See USEPA (2012a) and 

USEPA (2019b) for more information on 

the UCMR 3 study design and data 

analysis. 

UCMR 4 involved only AM and did 

not include any SS or PST efforts. The 

UCMR 4 a.m. was conducted by 

approximately 4,200 large systems and 

two separate nationally representative 

statistical samples of approximately 800 

small PWSs. One set of 800 small 

systems monitored for cyanotoxins, 

while the second set of 800 small 

systems monitored for the remaining 

UCMR 4 contaminants. 

Systems with surface water or GWUDI 

monitored for cyanotoxins and 

conducted eight sampling events over a 

period of four consecutive months. 

Cyanotoxin sampling was conducted 

during the period of March through 

November, when harmful algal bloom 

(HAB) events are more likely to occur in 

the Northern Hemisphere. Groundwater 

systems were excluded from cyanotoxin 

monitoring (USEPA, 2016c). Overall, the 

UCMR 4 a.m. resulted in approximately 

35,000 to 63,000 sample results per 

contaminant (depending on the specific 

sampling design for the contaminant). 

(81 FR 92666; USEPA, 2016c) 

The details of the occurrence data and 

the results or findings for each of the 

contaminants considered for regulatory 

determination are presented in section 

IV.B of this document, the contaminant 

profiles section, and are described in 

further detail in the Regulatory 

Determination 5 Support Document 

(USEPA, 2024b). The national design, 

the statistical sampling frame, any new 

analytical methods and the data analysis 

approach for the UCMR program have 

been peer-reviewed at different stages of 

development (see USEPA, 2001b, 2008b, 

2015a, 2019b). 

The fifth UCMR (UCMR 5) FRN, 

published December 2021, requires 

sample collection and analysis for 29 

PFAS, including PFOA, PFOS, PFHxS, 

PFNA, HFPO–DA and PFBS, to occur 

between January 2023 and December 

2025 using drinking water analytical 

methods developed by the EPA. Section 

2021 of America’s Water Infrastructure 

Act of 2018 (AWIA) (Pub. L. 115–270) 

amended SDWA and specifies that, 

subject to the availability of EPA 

appropriations for such purpose and 

sufficient laboratory capacity, the EPA 

must require all PWSs serving between 

3,300 and 10,000 people to monitor and 

ensure that a nationally representative 

sample of systems serving fewer than 

3,300 people monitor for the 

contaminants in UCMR 5 and future 

UCMR cycles. All large water systems 

continue to be required to participate in 

the UCMR program. As data under the 

UCMR 5 are being collected 

concurrently with the RD 5 evaluation 

process, the complete UCMR 5 dataset 

is not available to inform the regulatory 

determinations in this preliminary RD 5 

FRN. The EPA intends to evaluate the 

full UCMR 5 dataset when it is available 

and to consider making regulatory 

determinations for the included 

contaminants in the future. 

The UCMR program serves as the 

primary occurrence data source for all 

nine preliminary determinations 

included in this FRN. Other examples of 

occurrence data sources considered to 

be nationally representative for RD 5 are 

listed here. These are described in more 

detail in Chapter 2 of the Regulatory 

Determination 5 Support Document 

(USEPA, 2024b). 

• National Inorganics and 

Radionuclides Survey (NIRS) 

• Unregulated Contaminant Monitoring 

(UCM) Program Rounds 1 and 2 

(b) Supplemental Sources of Finished 

Drinking and Ambient Water 

Occurrence Data 

The agency evaluates several sources 

of supplemental information related to 

contaminant occurrence in finished 

water and ambient and source waters to 

augment the primary drinking water 

occurrence data. Some of these sources 

were part of other agency information 

gathering efforts or submitted to the 

agency in public comment or suggested 

by stakeholders during previous CCL 

and regulatory determination efforts. 

These supplemental data are useful to 

evaluate the likelihood of contaminant 

occurrence in drinking water, to more 

fully characterize a contaminant’s 

presence in the environment and 

potentially in source water and to 

evaluate any possible trends or spatial 

patterns that may need further review. 

In cases where there is a sufficient 

amount of non-national data to illustrate 

contaminant occurrence at a national 

level, the EPA may use non-national 

data as the basis for a regulatory 

determination. The descriptions that 

follow do not cover all the sources that 

the EPA used. For individual 

contaminants, the EPA reviewed 

additional published reports and peerreviewed studies that may have 

provided the results of monitoring 

efforts in limited geographic areas. A 

more detailed discussion of the 

supplemental sources of information/ 

data that the EPA evaluated and the 

occurrence data for each contaminant 

can be found in the Regulatory 

Determination 5 Support Document 

(USEPA, 2024b). 

Occurrence data were collected from 

other sources for consideration in RD 5 

as well. Non-national occurrence data 

sources are also discussed in detail in 

Chapter 2 of the Regulatory 

Determination 5 Support Document and 

include: 

• Individual states’ data 

• Community Water System Survey 

(CWSS) Data 

• United States Department of 

Agriculture (USDA) Pesticide Data 

Program (PDP) 

• United States Geological Survey 

(USGS) Pilot Monitoring Program 

(PMP) 

• USGS National Water Quality 

Assessment (NAWQA) 

• National Water Information System 

(NWIS) 

• Water Quality Exchange (WQX)/Water 

Quality Portal (WQP) Data System 

(Formerly the Storage and Retrieval 

Data System [STORET]) 

(c) Supplemental Production, Use and 

Release Data 

The agency reviews various sources of 

information to assess if there are 

changes or trends in a contaminant’s 

production, use and release that may 

affect its presence in the environment 

and potential occurrence in drinking 

water. The cancellation of a pesticide or 

a clear increase in production and use 

of a contaminant are trends that can 

inform the regulatory determination 

process. Examples of such sources are 

listed here. A more detailed discussion 

of the supplemental sources of 

information/data that the EPA evaluated 

and the occurrence data for each 

contaminant can be found in the 

Regulatory Determination 5 Support 

Document (USEPA, 2024b). 

• Inventory Update Reporting (IUR) and 

Chemical Data Reporting (CDR) 

Program (https://www.epa.gov/ 

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• Toxics Release Inventory (TRI) 

(https://www.epa.gov/toxics-releaseinventory-tri-program) 

• Pesticide Usage Estimates (https://

www.epa.gov/pesticides/pesticidesindustry-sales-and-usage-2008-2012- 

market-estimates) 

IV. Contaminant-Specific Discussions 

for the RD 5 Preliminary 

Determinations 

A. Summary of the Preliminary 

Regulatory Determinations 

Based on the EPA’s evaluation of the 

three SDWA criteria (discussed in 

section II.B.1 of this document), the 

agency is making preliminary 

determinations not to regulate nine 

contaminants. For each of the nine 

contaminants discussed in this section 

of this Document, Table 4 of this 

document summarizes information 

about the qualifying health assessment 

that was selected, the critical study, the 

critical effect and the associated oral 

reference value or oral CSF used to 

derive an HRL. Following Table 4, Table 

5 of this document summarizes the 

primary occurrence information used to 

make these preliminary regulatory 

determinations. Section IV.B of this 

document provides a more detailed 

summary of the information and the 

rationale used by the agency to reach its 

preliminary decisions for these nine 

contaminants. For more information 

about the five Phase 3 contaminants that 

are not receiving a preliminary 

regulatory determination, see section 

Vof this document. 

TABLE 4—HEALTH EFFECTS INFORMATION FOR CONTAMINANTS DISCUSSED IN SECTION IV 

RD 5 contaminant Qualifying health assessment selected Critical study Critical effect 

Oral 

reference 

value for 

noncancer 

effects, in 

mg/kg/day 

Oral CSF, in 

(mg/kg/ 

day) ¥1

HRL, in 

μg/L 

2-Aminotoluene ........... EPA PPRTV, 2012 ... Weisburger et al., 

1978.

Subcutaneous fibromas and fibrosarcomas 

in male rats and mice.

n/a 0.016 2 

Cylindrospermopsin ..... EPA OW HESD, 

2015.

Humpage and Falconer, 2002; 

Humpage and Falconer, 2003.

Increased relative kidney weight in male 

mice.

0.0001 n/a 0.6 

Ethoprop ...................... EPA OPP HHRA, 

2015.

Chartier et al., 2005 .. Inhibition of red blood cell (RBC) cholinesterase (ChE) in postnatal day (PND) 11 

rat pups.

6.5 × 10¥5 n/a 0.09 

Microcystins * ............... EPA OW HESD, 

2015.

Heinze, 1999 ............. Liver effects (increased liver weight, slight 

to moderate liver necrosis lesions and increased enzyme levels) in rats.

5 × 10¥5 n/a 0.3 

Molybdenum ................ ATSDR, 2020 ............ Murray et al., 2014 ... Renal proximal tubule hyperplasia ............... 0.06 n/a 100 

Permethrin ................... EPA OPP HHRA, 

2020.

Wolansky et al., 2006 Decreased motor activity in adult male rats 0.44 n/a 3,000 

Profenofos ................... EPA OPP HHRA, 

2015.

Burdock et al., 1981 Inhibition of RBC acetylcholinesterase 

(AChE) in adult rats.

0.00012 n/a 0.7 

Tebuconzole ................ EPA OPP HHRA, 

2021.

Becker and 

Biedermann, 1995.

Increased incidence of skull/neural tube defects including abnormalities of the eyes, 

head and skull.

0.03 n/a 200 

Tribufos ........................ EPA OPP HHRA, 

2015.

Sheets and Gilmore, 

2001.

Inhibition of RBC ChE in adult female rats .. 0.0002 n/a 1 

* Microcystin LR was used as a surrogate for deriving an oral reference value for all microcystin congeners. 

TABLE 5—OCCURRENCE FINDINGS FROM PRIMARY DATA SOURCES

RD 5 contaminant HRL, μg/L Primary 

database 

PWSs with at least 1 

detection >1⁄2 HRL 

Population served by 

PWSs with at least 1 

detection >1⁄2 HRL 

PWSs with at least 1 

detection > HRL 

Population served by 

PWSs with at least 1 

detection > HRL 

2-Aminotoluene ....................................... 2 UCMR 4 AM 0/5,030 (0.00%) ....... 0/249 M (0.00%) ...... 0/5,030 (0.00%) ....... 0/249 M (0.00%). 

Cylindrospermopsin ................................. 0.6 UCMR 4 AM 3/3,484 (0.09%) ....... 30,829/195 M 

(0.02%).

1/3,484 (0.03%) ....... 10,174/195 M 

(0.01%). 

Ethoprop .................................................. 0.09 UCMR 4 AM 3/5,028 (0.06%) ....... 75,032/249 M 

(0.03%).

1/5,028 (0.02%) ....... 14,999/249 M 

(0.01%). 

Microcystins ............................................. 0.3 UCMR 4 AM 7/3,485 (0.20%) ....... 119,725/195 M 

(0.06%).

7/3,485 (0.20%) ....... 119,725/195 M 

(0.06%). 

Molybdenum ............................................ 100 UCMR 3 AM 29/4,922 (0.59%) ..... 600,187/241 M 

(0.25%).

7/4,922 (0.14%) ....... 148,678/241 M 

(0.06%). 

Permethrin ............................................... 3000 UCMR 4 AM 0/5,028 (0.00%) ....... 0/249 M (0.00%) ...... 0/5,028 (0.00%) ....... 0/249 M (0.00%). 

Profenofos ............................................... 0.7 UCMR 4 AM 4/5,028 (0.08%) ....... 85,728/249 M 

(0.03%).

1/5,028 (0.02%) ....... 14,999/249 M 

(0.01%). 

Tebuconazole .......................................... 200 UCMR 4 AM 0/5,028 (0.00%) ....... 0/249 M (0.00%) ...... 0/5,028 (0.00%) ....... 0/249 M (0.00%). 

Tribufos .................................................... 1 UCMR 4 AM 0/5,027 (0.00%) ....... 0/249 M (0.00%) ...... 0/5027 (0.00%) ........ 0/249 M (0.00%). 

B. Contaminant Profiles 

1. 2-Aminotoluene 

(a) Background 

2-Aminotoluene (also referred to as otoluidine or 2-methylaniline) is a 

synthetic aromatic amine and occurs as 

a colorless or light-yellow liquid. It is 

used in the manufacture of dyes, rubber 

vulcanization accelerators, 

pharmaceuticals and pesticides. 

Production data for 2-aminotoluene 

are available from the EPA’s IUR and 

CDR programs. Annual production and 

importation of 2-aminotoluene was last 

reported by IUR for 2005 to be in the 

range of 10 to <50 million pounds. From 

2012 to 2019, annual production was in 

the range of 50 to 100 million pounds 

as reported under CDR. Industrial 

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site surface water discharges have been 

at just under 200 pounds per year since 

2009, with no more than six states 

reporting surface water discharges in a 

given year. 

An overall removal half-life for 2- 

aminotoluene in Rhine River water was 

estimated to be approximately 1 day 

(IPCS, 1998). Volatilization from water 

surfaces is expected to be an important 

fate process. Based on these physical 

and chemical properties, 2- 

aminotoluene is unlikely to be 

environmentally persistent in surface 

water. 

(b) Statutory Criterion 1 (Adverse Health 

Effects) 

The EPA proposes to find that 2- 

aminotoluene meets the first SDWA 

statutory criterion for regulatory 

determinations: exposure to 2- 

aminotoluene may have an adverse 

effect on the health of persons. The 

health assessment selected for RD 5 is 

the 2012 EPA Provisional PeerReviewed Toxicity Value (PPRTV) 

(USEPA, 2012b) because it is the only 

qualifying peer-reviewed health 

assessment identified for 2- 

aminotoluene that derives an oral CSF 

based on the best available science. In 

this health assessment, the EPA 

determined that 2-aminotoluene is 

‘‘likely to be carcinogenic to humans’’ 

by following the process described in 

the EPA’s 2005 Guidelines for 

Carcinogen Risk Assessment (USEPA, 

2005b; USEPA, 2012b). 

In the 2012 EPA PPRTV (USEPA, 

2012b), the EPA selected a chronic 

carcinogenicity diet study in mice and 

rats (Weisburger et al., 1978) as the 

critical study to derive an oral CSF for 

2-aminotoluene (see section 3.3 of 

Chapter 3 in the Regulatory 

Determination 5 Support Document for 

more details about the critical study). 

Increased subcutaneous fibromas and 

fibrosarcomas in male rats was the 

critical effect selected for derivation of 

an oral CSF because it provided the 

most sensitive cancer endpoint (USEPA, 

2012b). Because the Weisburger et al. 

(1978) study exposed experimental 

animals to o-toluidine hydrochloride 

(HCl), the EPA converted the oral CSF 

of 0.02 (mg/kg-day)¥1 o-toluidine HCl to 

account for the molecular weight 

difference of o-toluidine, resulting in a 

computed oral CSF of 0.016 (mg/kgday)¥1 for o-toluidine (2-aminotoluene) 

(USEPA, 2012b). 

Because exposure began during 

postnatal development (i.e., at six to 

eight weeks of age) in the critical study 

(Weisburger et al., 1978), the EPA used 

the DWI–BW representing the 90th 

percentile consumers-only, two-day 

average, direct and indirect community 

water consumption for children (birth to 

<21 years) of 0.0343 L/kg/day (USEPA, 

2019a) to derive the HRL for 2- 

aminotoluene (see decision logic 

provided in section B.6.1.2 of the RD 5 

Protocol, found in Appendix B of the 

Regulatory Determination 5 Support 

Document). 

Following HRL derivation practices, 

the EPA derived an HRL for 2- 

aminotoluene of 2 mg/L after rounding to 

one significant figure, based on a onein-a-million (10¥6) CRL, an oral CSF of 

0.016 (mg/kg/day)¥1 (USEPA, 2012b) 

and a DWI–BW of 0.0343 L/kg/day 

(USEPA, 2019a). 

These analyses formed the basis for 

the EPA’s finding that 2-aminotoluene 

may have adverse effect on the health of 

persons and therefore that Statutory 

Criterion 1 is met. 

(c) Statutory Criterion 2 (Occurrence) 

The EPA proposes to find that 2- 

aminotoluene does not occur with a 

frequency and at levels of public health 

concern in PWSs based on the EPA’s 

evaluation of the following occurrence 

information. 

The primary occurrence data for 2- 

aminotoluene are nationally 

representative drinking water 

monitoring data from the UCMR 4 

program (2018–2020). Under UCMR 4 

a.m., 37,517 samples collected from 

5,030 PWSs were analyzed for 2- 

aminotoluene. Of these systems, 86 

(1.71%) reported detections at or above 

the MRL of 0.007 mg/L. There were no 

detections greater than the HRL (2 mg/ 

L) or the 1⁄2 HRL threshold (1 mg/L) 

(USEPA, 2024b). This comprehensive 

dataset suggests that 2-aminotoluene is 

not present in public water systems at 

concentrations that would pose a risk to 

human health. 

Occurrence data for 2-aminotoluene 

in ambient water are available from the 

NWIS database and STORET. NWIS 

data show no detections of 2- 

aminotoluene in any of the 145 samples 

at 67 sites. The STORET data set had no 

detections of 2-aminotoluene out of 3 

samples collected at 3 sites in 2021– 

2022. 

Based on the evaluation of these data 

sources, the EPA finds that 2- 

aminotoluene does not occur and is not 

likely to occur in PWSs with a 

frequency and at levels of public health 

concern. Therefore, the EPA finds that 

Statutory Criterion 2 is not met. 

(d) Statutory Criterion 3 (Meaningful 

Opportunity) 

Regulating 2-Aminotoluene under the 

SDWA does not present a meaningful 

opportunity for health risk reduction for 

persons served by PWSs based on the 

estimated exposed population, 

including sensitive populations. UCMR 

4 data indicate that the estimated 

population exposed to 2-aminotoluene 

at levels of public health concern is 0%. 

As a result, the agency finds that an 

NPDWR for 2-aminotoluene does not 

present a meaningful opportunity for 

health risk reduction. 

(e) Preliminary Regulatory 

Determination for 2-Aminotoluene 

The agency is making a preliminary 

determination not to regulate 2- 

aminotoluene with an NPDWR after 

evaluating health, occurrence and other 

related information against the three 

SDWA statutory criteria. While data 

indicate that 2-aminotoluene may have 

an adverse effect on human health, the 

occurrence data indicate that 2- 

aminotoluene does not occur, nor is it 

likely to occur in PWSs with a 

frequency and at levels of public health 

concern. 

Therefore, the agency has determined 

that regulating 2-aminotoluene with an 

NPDWR would not present a 

meaningful opportunity to reduce 

health risk for persons served by PWSs. 

The Regulatory Determination 5 

Support Document (USEPA, 2024b) and 

the Occurrence Data from the Fourth 

Unregulated Contaminant Monitoring 

Rule (UCMR 4) (USEPA, 2024c) present 

additional information and analyses 

supporting the agency’s evaluation of 2- 

aminotoluene. 

2. Cylindrospermopsin 

(a) Background 

Cylindrospermopsin is a toxin 

naturally produced and released by 

cyanobacteria. Cyanobacteria, 

sometimes referred to as blue-green 

algae, are photosynthetic bacteria that 

are nearly ubiquitous in freshwater and 

marine environments. HABs of 

cyanobacteria in freshwater 

environments can release quantities of 

cyanotoxins, including 

cylindrospermopsin. 

Cylindrospermopsin is a tricyclic 

alkaloid (USEPA, 2015b). 

Cylindrospermopsin is naturally 

produced in the environment by 

cyanobacteria genera including the 

cylindrospermopsin-producing species 

Aphanizomenon, Dolichospermum 

(previously Anabaena), Lyngbya, 

Raphidiopsis (previously 

Cylindrosperopsis) and Umezakia 

(USEPA, 2022d). Cyanotoxin production 

is influenced by environmental 

conditions that favor the growth of 

particular cyanobacterial species and 

strains. Factors that affect 


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cyanobacterial growth, cyanobacteria 

population dynamics and the 

development of blooms include nutrient 

concentrations, light intensity, water 

turbidity, temperature, competing 

bacteria and phytoplankton, pH and 

turbulence (mixing). The concentrations 

of cyanotoxins released from a bloom 

will depend on the composition of the 

bloom and environmental and 

ecosystem influences on bloom 

dynamics (USEPA, 2015b). 

Cylindrospermopsin may readily 

leach or be released from intact 

cyanobacterial cells into surrounding 

water. Field studies have found that 

from 24% to 100% of 

cylindrospermopsin can be extracellular 

(Chorus and Welker, 2021). 

Cylindrospermopsin is highly watersoluble (WHO, 2020a). Its ability to 

partition from water to sediments is 

affected by the type of sediment, with 

some adsorption to organic carbon 

sediments and little adsorption to sandy 

and silt sediments. Bioaccumulation of 

cylindrospermopsin in freshwater 

organisms has been documented 

(Kinnear, 2010). 

(b) Statutory Criterion 1 (Adverse Health 

Effects) 

Exposure to cylindrospermopsin may 

have an adverse effect on the health of 

persons as supported by the health 

assessments identified for RD 5 (USEPA, 

2015b; WHO, 2020a). The health 

assessment selected to derive an HRL 

for cylindrospermopsin is the 2015 EPA 

Office of Water (OW) Health Effects 

Support Document (HESD) (USEPA, 

2015b) because it is an EPA peerreviewed health assessment that derives 

an oral toxicity value and it uses the 

best available science in its evaluation 

of noncancer risk for 

cylindrospermopsin. 

In the 2015 EPA OW HESD (USEPA, 

2015b), the EPA selected an 11-week 

drinking water toxicity study in mice 

(Humpage and Falconer, 2002; 

Humpage and Falconer, 2003) as the 

critical study to derive an oral reference 

value (see section 4.3 of Chapter 4 in the 

Regulatory Determination 5 Support 

Document for more details about the 

critical study). A No Observed Adverse 

Effect Level (NOAEL) of 30 mg/kg/day 

for increased relative kidney weight in 

mice was the critical effect and point of 

departure (POD) selected to derive an 

oral reference value because this was 

the most sensitive endpoint assessed in 

the critical study (USEPA, 2015b). A 

total UF of 300 was applied to the POD: 

an interspecies UF (UFA) of 10, an 

intraspecies UF (UFH) of 10 and a 

database UF (UFD) of 3. After applying 

the total UF of 300 (details can be found 

in section 4.3 of Chapter 4 in the 

Regulatory Determination 5 Support 

Document), the oral reference value was 

calculated to be 0.0001 mg/kg/day 

(USEPA, 2015b) and the EPA selected 

this oral reference value to derive an 

HRL for RD 5. 

The critical study does not report how 

old the mice were at the onset of 

exposure; however, it does report that 

mice weighed 20 to 25 grams at the 

beginning of the experiment (Humpage 

and Falconer, 2002; Humpage and 

Falconer, 2003). The EPA extrapolated 

the body weight of the rodents to their 

approximate age to determine the most 

sensitive lifestage exposed (Jackson 

Labs, 2023). Because exposure was 

estimated to have begun during 

postnatal development (i.e., at 

approximately six to eight weeks of age), 

the EPA used the DWI–BW representing 

the 90th percentile consumers-only, 

two-day average, direct and indirect 

community water consumption for 

children (birth to <21 years) of 0.0343 

L/kg/day (USEPA, 2019a) to derive the 

to derive the HRL for 

cylindrospermopsin (see decision logic 

provided in section B.6.1.2 of the RD 5 

Protocol, found in Appendix B of the 

Regulatory Determination 5 Support 

Document). 

Following HRL derivation practices, 

the EPA derived an HRL for 

cylindrospermopsin of 0.6 mg/L after 

rounding to one significant figure, based 

on an oral reference value of 0.0001 mg/ 

kg/day (USEPA, 2015b), a DWI–BW of 

0.0343 L/kg/day (USEPA, 2019a) and a 

20% RSC (USEPA, 2000a). Note that 

this value differs from the 10-day HA for 

bottle-fed infants and young children 

(0.7 mg/L) and the 10-day HA for schoolage children through adults (3 mg/L). 

These HA values are considered 

protective of non-carcinogenic adverse 

health effects over a ten-day exposure to 

cylindrospermopsin in drinking water. 

Based on these analyses, the EPA 

finds that cylindrospermopsin may have 

an adverse effect on the health of 

persons and therefore that Statutory 

Criterion 1 is met. 

(c) Statutory Criterion 2 (Occurrence) 

The EPA proposes to find that 

cylindrospermopsin does not occur with 

a frequency and at levels of public 

health concern in PWSs based on the 

EPA’s evaluation of the following 

occurrence information. 

Occurrence data for 

cylindrospermopsin in ambient water 

are available from the USGS NAWQA 

program, the USGS NWIS database, the 

EPA’s legacy STORET Data System and 

several published studies. Additionally, 

a total of 18 states voluntarily adopted 

use of the One Health Harmful Algal 

Bloom System and entered 421 reports 

during 2016–2018 (Roberts et al., 2020). 

The majority of HAB events occurred 

during May–October (98%) and in 

freshwater bodies (90%). 

Cylindrospermopsin was reported as 

present in 4 (1%) of the 421 HAB 

events. 

The primary occurrence data for 

cylindrospermopsin are nationally 

representative drinking water 

monitoring data from the UCMR 4 

program (2018–2020). Under UCMR 

4 a.m., 35,425 samples collected from 

3,484 PWSs were analyzed for 

cylindrospermopsin via EPA Method 

545. Monitoring consisted of sampling 

finished drinking water in PWSs that 

use surface water or GWUDI. 

Groundwater systems were excluded 

from cyanotoxin monitoring. Monitoring 

occurred twice a month for four 

consecutive months during the period 

from March through November (for a 

total of eight sampling events). 

Sampling was conducted at entry points 

to the distribution system. 

In addition to analytical sample 

results, UCMR 4 required systems to 

provide information related to source 

water conditions and cyanobacteria/ 

cyanotoxin occurrence and treatment, 

including bloom occurrence, possible 

bloom treatment and details on changes 

in source water quality conditions. 

Reported UCMR 4 

cylindrospermopsin concentrations 

ranged from 0.09 mg/L (the MRL) to 

0.877 mg/L. Of these sampled systems, 

12 (0.34% of systems, serving 0.23% of 

the PWS-served population) reported at 

least one detection of 

cylindrospermopsin. Three systems 

serving nearly 31,000 people reported at 

least one detection of 

cylindrospermopsin greater than the 1⁄2

HRL threshold of 0.3 mg/L and 1 system 

serving 10,174 people reported at least 

one detection of cylindrospermopsin 

greater than the HRL of 0.6 mg/L. 

Extrapolating these findings from the 

population served by the PWSs 

participating in UCMR 4 to the national 

PWS-served population suggests that an 

estimated 34 PWSs serving around 

488,000 people nationally have at least 

one detection of cylindrospermopsin 

while an estimated 14 PWSs serving 

40,900 people nationally have at least 

one detection of cylindrospermopsin 

greater than the 1⁄2 HRL threshold and 

only 1 PWS, serving 10,200 people, has 

at least one detection greater than the 

HRL. 

Based on the evaluation of these data 

sources, the EPA finds that 

cylindrospermopsin does not occur in 

PWSs with a frequency and at levels of 


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public health concern. Therefore, the 

EPA finds that Statutory Criterion 2 is 

not met. 

(d) Statutory Criterion 3 (Meaningful 

Opportunity) 

Regulating cylindrospermopsin under 

the SDWA does not present a 

meaningful opportunity for health risk 

reduction for persons served by PWSs 

based on the estimated exposed 

population, including sensitive 

populations. The estimated PWS-served 

population exposed to 

cylindrospermopsin at levels of public 

health concern is 0.01% based on 

UCMR 4 finished water data. 

Conventional water treatment 

(consisting of coagulation, 

sedimentation, filtration and 

chlorination) can generally remove 

intact cyanobacterial cells and low 

levels of cyanotoxins from source 

waters. However, water systems may 

face challenges in providing drinking 

water during a severe bloom event when 

there are high levels of cyanobacteria 

and cyanotoxins in source waters. With 

proactive planning, diligent operations 

and maintenance and active 

management, PWSs can reduce the risks 

of cyanotoxins breaking through the 

treatment process and occurring in 

finished drinking water. Because these 

non-regulatory efforts to manage 

cyanotoxins are effective, the agency 

finds that an NPDWR for 

cylindrospermopsin does not present a 

meaningful opportunity for health risk 

reduction. 

(e) Preliminary Regulatory 

Determination for Cylindrospermopsin 

The EPA is making a preliminary 

determination not to regulate 

cylindrospermopsin with an NPDWR 

after evaluating health, occurrence and 

other related information against the 

three SDWA statutory criteria. While 

data suggest that cylindrospermopsin 

may have an adverse effect on human 

health, the occurrence data indicate that 

cylindrospermopsin is not occurring or 

not likely to occur in PWSs with a 

frequency and at levels of public health 

concern. Additionally, because 

conventional water treatment and 

continued efforts by water systems to 

manage cyanotoxins have proven 

effective, an NPDWR for 

cylindrospermopsin does not present a 

meaningful opportunity for health risk 

reduction. 

2. Ethoprop 

(a) Background 

Ethoprop is an organophosphate 

(phosphorodithioate) pesticide and is 

used as an insecticide and nematicide. 

Ethoprop was first registered in the U.S. 

in 1967 (USEPA, 2006a) and is used on 

vegetables, fruits and other plants, 

including potatoes, sweet potatoes, 

beans, cucumbers, cabbage, pineapples, 

bananas, plantains, tobacco and 

ornamentals. Environmental fate 

assessments with organic carbon 

partitioning coefficient (Koc) values of 

70–120 L/kg suggest ethoprop is mobile 

in soil and water (NCBI, 2023a). 

USGS estimates the usage of ethoprop 

has unevenly declined from 1992 to 

2019, with less than 1 million pounds 

of ethoprop used per year since 2012 in 

the United States. According to USGS, 

ethoprop usage has been limited 

geographically in recent years, mainly to 

the Pacific Northwest and California. 

(b) Statutory Criterion 1 (Adverse Health 

Effects) 

Exposure to ethoprop may have an 

adverse effect on the health of persons 

as supported by the health assessment 

identified for RD 5 (USEPA, 2015c; 

USEPA, 2015d). For pesticide chemicals 

currently registered under the Federal 

Insecticide, Fungicide and Rodenticide 

Act (FIFRA), including ethoprop, 

toxicity information from the EPA’s 

Office of Pesticide Programs (OPP) 

Human Health Risk Assessments 

(HHRAs) was used as the basis for HRL 

derivation (USEPA, 2024b). 

The health assessment selected to 

derive an HRL for ethoprop is the 2015 

EPA OPP HHRA (USEPA, 2015c; 

USEPA, 2015d), which provided both 

cancer and noncancer toxicity values 

(i.e., an oral reference value and oral 

CSF) for ethoprop. In 2023, OPP 

conducted exposure assessments for 

ethoprop to estimate human health risks 

resulting from registered uses (USEPA, 

2023a). The cancer classification had 

then changed from ‘‘Likely to be 

Carcinogenic to Humans’’ to 

‘‘Suggestive Evidence of Carcinogenic 

Potential’’ based on the presence of 

thyroid C-cell tumors in male F344 rats 

(USEPA, 2005b; 2023a). Although the 

critical study showed suggestive cancer 

effects from exposure to ethoprop, there 

were no concerns for mutagenicity. As 

a result, OPP recommended using a 

non-linear (i.e., RfD) approach as a 

protective measure of carcinogenic risk 

and did not conduct a new cancer 

assessment (USEPA, 2023a). Therefore, 

for RD 5 the EPA derived a noncancer 

HRL based on the oral reference value 

provided in the 2015 EPA OPP HHRA 

(USEPA, 2015c). 

In the 2015 EPA OPP HHRA, the EPA 

selected a repeat-dosing gavage study in 

rats (Chartier et al., 2005) as the critical 

study to derive the oral reference value 

(see section 5.3 of Chapter 5 in the 

Regulatory Determination 5 Support 

Document for more details about the 

critical study). Benchmark dose (BMD) 

modeling was used to determine the 

lower 95% confidence limit on the BMD 

level associated with a 10% response 

(BMDL10), the response in this case 

being inhibition of cholinesterase (ChE) 

activity (USEPA, 2015c). Inhibition of 

red blood cell (RBC) 

acetylcholinesterase (AChE) activity in 

postnatal day (PND) 11 males was the 

critical effect selected for derivation of 

the oral reference value because it was 

the most sensitive endpoint modeled 

(USEPA, 2015c). Therefore, the 

corresponding BMDL10 of 0.0653 mg/kg/ 

day was selected as the POD for 

ethoprop (USEPA, 2015c). A total 

uncertainty factor (UF) of 1,000 was 

applied to the POD: an interspecies UF 

(UFA) of 10, an intraspecies UF (UFH) of 

10, and a Food Quality Protection Act 

(FQPA) safety factor of 10 to account for 

uncertainty in the human dose-response 

relationship for neurodevelopmental 

effects (USEPA, 2015c). After applying 

the total UF (for more details about the 

selected UF, see section 5.3 of Chapter 

5 in the Regulatory Determination 5 

Support Document), the oral reference 

value was calculated to be 0.000065 mg/ 

kg/day and the EPA selected this oral 

reference value to derive an HRL for 

ethoprop. 

Because exposure began during early 

postnatal development (i.e., 11 days of 

age) in the critical study (Chartier et al., 

2005), the EPA used the DWI–BW 

representing the 90th percentile 

consumers-only, two-day average, of 

direct and indirect community water 

consumption for infants (birth to <1 

year) of 0.143 L/kg/day (USEPA, 2019a) 

to derive the HRL for ethoprop (see 

decision logic provided in section 

B.6.1.2 of the RD 5 Protocol, found in 

Appendix B of the Regulatory 

Determination 5 Support Document). 

Following HRL derivation practices, 

the EPA derived an HRL for ethoprop of 

0.09 mg/L after rounding to one 

significant figure, based on an oral 

reference value of 0.000065 mg/kg/day 

(USEPA, 2015c), a DWI–BW of 0.143 L/ 

kg/day (USEPA, 2019a) and a 20% RSC 

(USEPA, 2000a). 

Based on these analyses, the EPA 

finds that ethoprop may have an adverse 

effect on the health of persons and 

therefore that Statutory Criterion 1 is 

met. 

(c) Statutory Criterion 2 (Occurrence) 

The EPA proposes to find that 

ethoprop does not occur with a 

frequency and at levels of public health 

concern in PWSs based on the EPA’s 

evaluation of occurrence information. 


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The primary occurrence data for 

ethoprop are nationally representative 

drinking water monitoring data from 

UCMR 4 (2018–2020). Ethoprop was 

found in 0.1% of systems (5 of 5,028) 

monitored in UCMR 4 a.m. Of systems 

that reported results for ethoprop, three 

systems, or 0.06%, reported results 

above the 1⁄2 HRL threshold of 0.045 mg/ 

L, and one system (0.02%) reported a 

result above the HRL (0.09 mg/L). 

Extrapolating the UCMR 4 data suggests 

that less than 0.01% of the national 

PWS-served population may be exposed 

to ethoprop in drinking water at levels 

above the HRL. 

Based on the evaluation of these data 

sources, the EPA finds that ethoprop 

does not occur and is not likely to occur 

in PWSs with a frequency and at levels 

of public health concern. Therefore, the 

EPA finds that Statutory Criterion 2 is 

not met. 

(d) Statutory Criterion 3 (Meaningful 

Opportunity) 

The EPA proposes to find that 

ethoprop does not occur with a 

frequency and at levels of public health 

concern in PWSs based on the EPA’s 

evaluation of the occurrence 

information. Therefore, regulation of 

ethoprop under the SDWA does not 

present a meaningful opportunity for 

health risk reduction for persons served 

by PWSs. 

(e) Preliminary Regulatory 

Determination for Ethoprop 

The agency is making a preliminary 

determination not to regulate ethoprop 

with an NPDWR after evaluating health, 

occurrence and other related 

information against the three SDWA 

statutory criteria. While data suggest 

that ethoprop may have an adverse 

effect on human health, the occurrence 

data indicate that ethoprop is not 

occurring or not likely to occur in PWSs 

with a frequency and at levels of public 

health concern. The Regulatory 

Determination 5 Support Document 

(USEPA, 2024b) and the Occurrence 

Data from the Fourth Unregulated 

Contaminant Monitoring Rule (UCMR 4) 

(USEPA, 2024c) present additional 

information and analyses supporting the 

agency’s evaluation of ethoprop. 

3. Microcystins 

(a) Background 

Microcystins are toxins naturally 

produced and released by 

cyanobacteria. Cyanobacteria, 

sometimes referred to as blue-green 

algae, are photosynthetic bacteria that 

are nearly ubiquitous in freshwater and 

marine environments. HABs of 

cyanobacteria in freshwater 

environments can release quantities of 

cyanotoxins, including microcystins. 

Microcystins exist in multiple forms 

(congeners), based on variations in 

amino acid composition; there are 

approximately 100 known microcystin 

congeners (USEPA, 2015e). 

Microcystins are generally distinguished 

using letters that refer to the two 

variable amino acids. Microcystin-LR, 

which includes leucine (L) and arginine 

(R) amino acids, is the most common 

congener and also the most intensively 

studied (USEPA, 2015e). Synonyms for 

microcystin-LR include cyanoginosin 

LR (NCBI, 2022). 

The cyanobacteria genera Anabaena, 

Fischerella, Gloeotrichia, Microcystis, 

Nodularia, Nostoc, Oscillatoria and 

Planktothrix are known to include 

microcystin-producing species (USEPA, 

2015e). Microcystins are the most 

common cyanotoxins found worldwide 

and they have been reported in surface 

waters in most of the U.S. (Funari and 

Testai, 2008 as cited in USEPA, 2015e). 

For the most part, microcystins are not 

released into surrounding waters by 

healthy living cyanobacterial cells. 

Release of microcystins generally results 

from senescence or lysis. Cyanotoxin 

production is influenced by 

environmental conditions that favor the 

growth of particular cyanobacterial 

species and strains. Factors that affect 

cyanobacterial growth, cyanobacteria 

population dynamics and the 

development of blooms include nutrient 

concentrations, light intensity, water 

turbidity, temperature, competing 

bacteria and phytoplankton, pH and 

turbulence (mixing). The concentrations 

of cyanotoxins released from a bloom 

will depend on the composition of the 

bloom and environmental and 

ecosystem influences on bloom 

dynamics (USEPA, 2015f). Microcystins 

have the potential for bioconcentration 

and bioaccumulation in tissue 

(Machado et al., 2017). 

(b) Statutory Criterion 1 (Adverse Health 

Effects) 

Exposure to microcystin congeners 

microcystin-LA, microcystin-LW, 

microcystin-RR, microcystin-YR and 

microcystin-LR, referred to collectively 

throughout this document as 

‘‘microcystins,’’ may have an adverse 

effect on the health of persons as 

supported by the multiple health 

assessments identified for RD 5 (USEPA, 

2015e; HC, 2017; WHO, 2020b). The 

health assessment selected for RD 5 is 

the 2015 EPA OW HESD (USEPA, 

2015e) because it is an EPA peerreviewed health assessment that derives 

an oral toxicity value and uses the best 

available science in its evaluation of 

noncancer risk. 

In the 2015 EPA OW HESD (USEPA, 

2015e), the EPA selected a 28-day 

drinking water study in 11-week-old 

male rats (Heinze, 1999) as the critical 

study to derive an oral reference value 

(see section 6.3 of Chapter 6 in the 

Regulatory Determination 5 Support 

Document for more details about the 

critical study). A Lowest Observed 

Adverse Effect Limit (LOAEL) of 50 mg/ 

kg/day for liver effects in rats orally 

exposed to microcystin-LR was 

identified as the critical effect and used 

to derive an oral reference value because 

this was considered the ‘‘most 

appropriate basis for quantitation as it 

was a common finding among oral 

toxicology studies’’ (USEPA, 2015e). 

Since microcystin-LR is one of the most 

potent microcystin congeners and the 

majority of microcystin toxicity data 

comes from studying this congener, 

microcystin-LR was used as a surrogate 

for deriving an oral reference value for 

all microcystins (USEPA, 2015e). A total 

UF of 1000 was applied to the POD: a 

UFA of 10, a UFH of 10, a LOAEL-toNOAEL extrapolation UF (UFL) of 3 and 

a UFD of 3. After applying the total UF 

of 1000, the oral reference value was 

calculated to be 0.00005 mg/kg/day 

(USEPA, 2015e) and the EPA selected 

this oral reference value to derive an 

HRL for microcystins. 

Because exposure in the critical study 

started post-adolescence (i.e., at 11 

weeks of age), the EPA used the DWI– 

BW EF representing the 90th percentile 

consumers-only, two-day average, direct 

and indirect community water 

consumption for adults (21 years and 

older) of 0.0336 L/kg/day (USEPA, 

2019a) to derive the HRL for 

microcystins (see decision logic 

provided in section B.6.1.2 of the RD 5 

Protocol, found in Appendix B of the 

Regulatory Determination 5 Support 

Document). 

Following HRL derivation practices, 

the EPA derived an HRL for 

microcystins of 0.3 mg/L after rounding 

to one significant figure, based on an 

oral reference value of 0.00005 mg/kg/ 

day (USEPA, 2015e), a DWI–BW of 

0.0336 L/kg/day (USEPA, 2019a) and a 

20% RSC (USEPA, 2000a). 

Based on these analyses, the EPA 

finds that microcystins may have an 

adverse effect on the health of persons 

and therefore that Statutory Criterion 1 

is met. 

(c) Statutory Criterion 2 (Occurrence) 

The EPA proposes to find that 

microcystins do not occur with a 

frequency and at levels of public health 

concern in PWSs based on the EPA’s 


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14Using EPA Method 546, UCMR 4 systems were 

required to report total microcystins values at or 

above the EPA-defined MRL of 0.3 mg/L. If a 

reporting threshold of 0.3 mg/L for total 

microcystins using EPA Method 546 was exceeded, 

systems were required to report values for the six 

included microcystin congeners at or above the 

EPA-defined MRLs for each individual congener 

using EPA Method 544. For more details, see 

USEPA (2024c). 

evaluation of the following occurrence 

information. 

Occurrence data for microcystins in 

ambient water are available from the 

USGS NAWQA program, the USGS 

NWIS database, the EPA’s legacy 

STORET Data System and several 

published studies. Additionally, a total 

of 18 states voluntarily adopted use of 

the One Health Harmful Algal Bloom 

System and entered 421 reports during 

2016–2018 (Roberts et al., 2020). The 

majority of HAB events occurred during 

May–October (98%) and in freshwater 

bodies (90%). Microcystins were 

reported as present in 291 of the 421 

HABs. Of the 35 HABs where multiple 

cyanotoxins were found, microcystins 

were present in 33. Ambient water 

occurrence data are also available in the 

National Lakes Assessment. According 

to the 2017 report (USEPA, 2022e), 

microcystin was found in 21% of lakes. 

The minimum detection level was 0.1 

mg/L. The EPA’s recreational criterion (8 

mg/L) was exceeded in 2% of lakes 

(4,400 lakes). 

The primary occurrence data for 

microcystins are nationally 

representative drinking water 

monitoring data from the UCMR 4 

program (2018–2020). Under UCMR 4 

a.m., 35,000 samples were collected 

from 3,485 PWSs and analyzed for total 

microcystins via EPA Method 546.14

Monitoring consisted of sampling 

finished drinking water in PWSs that 

use surface water or groundwater under 

the influence of surface water (GWUDI. 

Groundwater systems were excluded 

from cyanotoxin monitoring. Monitoring 

occurred twice a month for four 

consecutive months from March 

through November (for a total of eight 

sampling events). Sampling was 

conducted at entry points to the 

distribution system. 

In addition to analytical sample 

results, UCMR 4 required systems to 

provide information related to source 

water conditions and cyanobacteria/ 

cyanotoxin occurrence and treatment, 

including bloom occurrence, possible 

bloom treatment and details on changes 

in source water quality conditions. 

Reported UCMR 4 total microcystins 

concentrations ranged from 0.32 mg/L to 

0.83 mg/L. Seven systems (0.20% of 

systems, serving 0.06% of the PWSserved population) reported at least one 

result at or above the MRL for total 

microcystins. Extrapolating these 

findings suggests that an estimated 29 

PWSs serving 0.06% of the PWS-served 

population nationally may have 

detectable levels of total microcystins. 

While all reported results were above 

the HRL (0.3 mg/L), only eight of the 

35,000 samples collected during UCMR 

4 contained reportable concentrations of 

microcystins. 

Based on the evaluation of these data 

sources, the EPA finds that microcystins 

do not occur and are not likely to occur 

in PWSs with a frequency and at levels 

of public health concern. Therefore, the 

EPA finds that Statutory Criterion 2 is 

not met. 

(d) Statutory Criterion 3 (Meaningful 

Opportunity) 

Regulating microcystins under the 

SDWA does not present a meaningful 

opportunity for health risk reduction for 

persons served by PWSs based on the 

estimated exposed population, 

including sensitive populations. The 

estimated population exposed to 

microcystins at levels of public health 

concern is 0.06% based on UCMR 4 

finished water data. 

Conventional water treatment 

(consisting of coagulation, 

sedimentation, filtration and 

chlorination) can generally remove 

intact cyanobacterial cells and low 

levels of cyanotoxins from source 

waters. However, water systems may 

face challenges in providing drinking 

water during a severe bloom event when 

there are high levels of cyanobacteria 

and cyanotoxins in source waters. With 

proactive planning, diligent operations 

and maintenance and active 

management, PWSs can reduce the risks 

of cyanotoxins breaking through the 

treatment process and occurring in 

finished drinking water. Because these 

non-regulatory efforts are effective, the 

agency finds that an NPDWR for 

microcystins does not present a 

meaningful opportunity for health risk 

reduction. 

(e) Preliminary Regulatory 

Determination for Microcystins 

The agency is making a preliminary 

determination to not regulate 

microcystins with an NPDWR after 

evaluating health, occurrence and other 

related information against the three 

SDWA statutory criteria. While data 

suggest that microcystins may have an 

adverse effect on human health, the 

occurrence data indicate that 

microcystins are not occurring or not 

likely to occur in PWSs with a 

frequency and at levels of public health 

concern. Additionally, because 

conventional water treatment and 

continued efforts by water systems to 

manage cyanotoxins have proven 

effective, an NPDWR for microcystins 

does not present a meaningful 

opportunity for health risk reduction. 

5. Molybdenum 

(a) Background 

Molybdenum is a naturally occurring 

element, which, especially in the form 

of molybdenum trioxide, is commonly 

used in metallurgy, including in alloys 

with cast iron, steel and superalloys. 

Molybdenum compounds are also used 

in catalysts, lubricants and pigments. 

Molybdenum is naturally present in 

soils and additional molybdenum may 

be added by weathering and 

atmospheric deposition and by direct 

human activity such as application of 

molybdenum and phosphate fertilizers 

(Wong et al., 2021; Smedley and 

Kinniburgh, 2017). Anthropogenic 

sources of molybdenum in water 

include effluents from molybdenum, 

uranium and copper mining and milling 

operations, oil production and oil 

refining operations, and coal-fired 

power plants. Molybdenum is generally 

more mobile in water under alkaline 

conditions, with a greater potential for 

bioavailability through water exposure 

(ATSDR, 2020). 

(b) Statutory Criterion 1 (Adverse Health 

Effects) 

Exposure to molybdenum may have 

an adverse effect on the health of 

persons as supported by the health 

assessments identified for RD 5 (USEPA, 

1992; WHO, 2011; ATSDR, 2020). The 

health assessment selected for RD 5 is 

the 2020 ATSDR Toxicological Profile 

(ATSDR, 2020) because it is the most 

recent peer-reviewed health assessment 

identified for molybdenum that derives 

an oral toxicity value, it uses the best 

available science in its evaluation of 

noncancer risk, and its toxicity value is 

based on a more recent critical study 

(Murray et al., 2014) than those of 

previous health assessments (USEPA, 

1992; WHO, 2011). 

In the 2020 ATSDR Toxicological 

Profile (ATSDR, 2020), ATSDR selected 

a 90-day dietary toxicity study in rats 

(Murray et al. 2014) as the critical study 

to derive an intermediate-duration oral 

reference value (see section 7.3 of 

Chapter 7 in the Regulatory 

Determination 5 Support Document for 

more details about the critical study). A 

NOAEL of 17 mg/kg/day for renal effects 

in female rats was identified as the 

critical effect to derive an oral reference 

value because this was the most 

sensitive endpoint identified (ATSDR, 


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2020). After applying the total UF of 100 

and a modifying factor of 3, the 

intermediate-duration oral reference 

value was calculated to be 0.06 mg/kg/ 

day. Because ATSDR did not derive a 

chronic-duration oral reference value, 

and the EPA’s definition of chronic 

exposure is repeated exposure (oral, 

dermal or inhalation) for more than 

approximately 90 days to 2 years 

(USEPA, 2023b), the EPA applied a UF 

for extrapolation from subchronic-to 

chronic exposure duration (UFS) of 3, 

per agency guidelines (USEPA, 2002), to 

the intermediate-duration oral reference 

value that was derived using the 90-day 

study. Therefore, the resulting oral 

reference value used to derive the HRL 

for molybdenum was calculated to be 

0.02 mg/kg/day. 

Because exposure began during 

postnatal development (approximately 

nine weeks of age), the EPA used the 

DWI–BW representing the 90th 

percentile consumers-only, two-day 

average, direct and indirect community 

water consumption for children (birth to 

<21 years) of 0.0343 L/kg/day (USEPA, 

2019a) to derive the HRL for 

molybdenum (see decision logic 

provided in section B.6.1.2 of the RD 5 

Protocol, found in Appendix B of the 

Regulatory Determination 5 Support 

Document). 

Following HRL derivation practices, 

the EPA derived an HRL for 

molybdenum of 100 mg/L after rounding 

to one significant figure, based on an 

oral reference value of 0.06 mg/kg/day 

(ATSDR, 2020), with an additional UFS

of 3, a DWI–BW of 0.0343 L/kg/day 

(USEPA, 2019a) and a 20% RSC 

(USEPA, 2000a). 

Based on these analyses, the EPA 

finds that molybdenum may have an 

adverse effect on the health of persons 

and therefore that Statutory Criterion 1 

is met. 

(c) Statutory Criterion 2 (Occurrence) 

The EPA proposes to find that 

molybdenum does not occur with a 

frequency and at levels of public health 

concern in PWSs based on the EPA’s 

evaluation of the following occurrence 

information. 

The primary occurrence data for 

molybdenum are nationally 

representative drinking water 

monitoring data from the UCMR 3 

program (2013–2015). Under UCMR 3 

a.m., 62,986 samples were collected 

from 4,922 PWSs and analyzed for 

molybdenum. Of these systems, 52% 

reported results at or above the MRL of 

1 mg/L. Seven systems (0.14%) reported 

results above the HRL of 100 mg/L and 

29 systems (0.59%) reported results 

above the 1⁄2 HRL threshold of 50 mg/L. 

Based on the UCMR 3 occurrence data 

set, a national estimate of 216 systems 

and 0.06% of the PWS-served 

population may be exposed to 

molybdenum in drinking water at levels 

exceeding the HRL. 

Occurrence data for molybdenum in 

ambient water are available from the 

NAWQA program and NWIS database. 

Across the three cycles of NAWQA, 

molybdenum was detected in 45% to 

100% of samples. The HRL was 

exceeded in a single surface water 

sample (in Cycle 1) and in 0.12% to 

0.26% of groundwater samples across 

the three cycles. Non-NAWQA NWIS 

data for molybdenum include 47 

finished water samples from 29 sites. 

The highest reported finished water 

concentration (52.5 mg/L) exceeds the 1⁄2

HRL threshold but not the HRL. The 

median concentration of NWIS 

detections was 1.64 mg/L. 

For additional information on 

occurrence data available for 

molybdenum in drinking water please 

see section 7.4 of Chapter 7 in the 

Regulatory Determination 5 Support 

Document (USEPA, 2024b). 

Based on the evaluation of these data 

sources, the EPA finds that 

molybdenum does not occur and is not 

likely to occur in PWSs with a 

frequency and at levels of public health 

concern. Therefore, the EPA finds that 

Statutory Criterion 2 is not met. 

(d) Statutory Criterion 3 (Meaningful 

Opportunity) 

Regulating molybdenum under the 

SDWA does not present a meaningful 

opportunity for health risk reduction for 

persons served by PWSs based on the 

estimated exposed population, 

including sensitive populations. UCMR 

3 data indicate that the estimated 

population exposed to molybdenum 

above the HRL is 0.08%. As a result of 

the low occurrence above the HRL, the 

agency finds that an NPDWR for 

molybdenum does not present a 

meaningful opportunity for health risk 

reduction. 

(e) Preliminary Regulatory 

Determination for Molybdenum 

The agency is making a preliminary 

determination not to regulate 

molybdenum with an NPDWR after 

evaluating health, occurrence and other 

related information against the three 

SDWA statutory criteria. While data 

suggest that molybdenum may have an 

adverse effect on human health, the 

occurrence data indicate that 

molybdenum is not occurring or not 

likely to occur in PWSs with a 

frequency and at levels of public health 

concern. The Regulatory Determination 

5 Support Document (USEPA, 2024b) 

and the Occurrence Data from the Third 

Unregulated Contaminant Monitoring 

Rule (UCMR 3) (USEPA, 2019b) present 

additional information and analyses 

supporting the agency’s evaluation of 

molybdenum. 

7. Permethrin 

(a) Background 

Permethrin is a pyrethroid pesticide 

primarily used as an insecticide, with 

various synonyms including ambush 

and corsair. It was first registered in the 

U.S. in 1979. 

Sources of permethrin include 

agricultural usage and industrial 

activities. TRI provides insight into 

industrial releases of permethrin. There 

have been no reported surface water 

discharges since 2005. Permethrin usage 

in agriculture has been estimated by 

USGS to have peaked in 1995 with 1.4 

million pounds, with a gradual decrease 

to steady usage between around 600,000 

and 800,000 pounds annually 

throughout 2001–2019. 

The EPA’s assessments of permethrin 

include its chemical and physical 

properties, such as very low solubility 

in water (0.006 mg/L) and Koc values of 

10,471–86,000 L/kg, which suggest that 

permethrin will be of low mobility in 

soil and less likely to partition to water. 

Biodegradation is expected to be rapid 

in various environmental conditions, 

since the half-life of permethrin in 

sediment/seawater is <2.5 days, while 

the half-life of permethrin in a model 

ecosystem at 15–19 degrees Celsius and 

a pH of 7.7 was 1.1–3.6 days. 

(b) Statutory Criterion 1 (Adverse Health 

Effects) 

Exposure to permethrin may have an 

adverse effect on the health of persons 

as supported by the health assessment 

identified for RD 5 (USEPA, 2020b; 

USEPA, 2020c). For pesticide chemicals 

currently registered under FIFRA, 

including permethrin, toxicity 

information from EPA’s OPP HED 

HHRAs was used as the basis for HRL 

derivation (USEPA, 2023c). 

The health assessment selected to 

derive an HRL for permethrin is the 

2020 EPA OPP HHRA (USEPA, 2020ba; 

USEPA, 2020c). Following the approach 

described in the EPA’s Guidelines for 

Carcinogen Risk Assessment (USEPA, 

2005b), permethrin was classified in the 

health assessment as having ‘‘Suggestive 

Evidence of Carcinogenic Potential’’ 

based on lung adenomas in female mice. 

However, due to the lack of increased 

hazard from repeated/chronic exposure 

to permethrin, the acute risk estimate 

derived from the non-linear approach is 


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protective of chronic toxicity, including 

carcinogenicity, that could result from 

permethrin exposure (USEPA, 2020c). 

Therefore, the EPA selected an acute 

gavage study in rats (Wolansky et al., 

2006) as the critical study to derive an 

oral reference value (see section 8.3 of 

Chapter 8 in the Regulatory 

Determination 5 Support Document for 

more details about the critical study). 

BMD modeling was performed to derive 

a lower 95% confidence limit on the 

BMD level associated with a difference 

of one standard deviation from controls 

(BMDL1SD) for decreased motor activity 

(Wolansky et al., 2006), which was 

identified as the critical effect for 

dietary exposure, as this was the most 

sensitive endpoint measured (USEPA, 

2020c). The BMDL1SD was calculated to 

be 44 mg/kg. A total UF of 100 was 

applied to the POD: a UFH of 10 and a 

UFA of 10. After applying the total UF 

of 100, the oral reference value was 

calculated to be 0.44 mg/kg/day 

(USEPA, 2020c) and the EPA selected 

this oral reference value to derive an 

HRL for permethrin. 

Because exposure began during 

postnatal development (i.e., at 

approximately nine weeks of age) in the 

critical study (Wolansky et al., 2006), 

the EPA used the DWI–BW representing 

the 90th percentile consumers-only, 

two-day average, direct and indirect 

community water consumption for 

children (birth to <21 years) of 0.0343 

L/kg/day (USEPA, 2019a) to derive the 

HRL for permethrin (see decision logic 

provided in section B.6.1.2 of the RD 5 

Protocol, found in Appendix B of the 

Regulatory Determination 5 Support 

Document, USEPA, 2024b). 

Following HRL derivation practices, 

the EPA derived an HRL for permethrin 

of 3,000 mg/L after rounding to one 

significant figure, based on an oral 

reference value of 0.44 mg/kg/day 

(USEPA, 2020b; USEPA, 2020c), a DWI– 

BW of 0.0343 L/kg/day (USEPA, 2019a) 

and a 20% RSC (USEPA, 2000a). 

Based on these analyses, the EPA 

finds that permethrin may have an 

adverse effect on the health of persons 

and therefore that Statutory Criterion 1 

is met. 

(c) Statutory Criterion 2 (Occurrence) 

The EPA proposes to find that 

permethrin does not occur with a 

frequency and at levels of public health 

concern in PWSs based on the EPA’s 

evaluation of occurrence information. 

The primary occurrence data for 

permethrin are nationally representative 

drinking water monitoring data from the 

UCMR 4 program (2018–2020). Under 

UCMR 4 a.m., 37,291 samples collected 

from 5,028 PWSs were analyzed for 

permethrin. Permethrin was detected in 

0.26% of systems at or above the MRL 

of 0.04 mg/L. There were no reported 

results above the HRL of 3,000 mg/L or 

above the 1⁄2 HRL threshold. This 

comprehensive dataset suggests that 

permethrin is not present in public 

water systems at concentrations that 

would pose a risk to human health. 

To supplement the data obtained from 

UCMR 4, the EPA also reviewed 

ambient water data from the USGS 

NAWQA program. NAWQA Cycle 2 

showed no detections of permethrin. 

NAWQA Cycle 3 showed detections of 

permethrin in 2 of 11 sites (18%) with 

no results above the HRL. 

Based on the evaluation of these data 

sources, the EPA finds that permethrin 

does not occur and is not likely to occur 

in PWSs with a frequency and at levels 

of public health concern. Therefore, the 

EPA finds that Statutory Criterion 2 is 

not met. 

(d) Statutory Criterion 3 (Meaningful 

Opportunity) 

Regulating permethrin under the 

SDWA does not present a meaningful 

opportunity for health risk reduction for 

persons served by PWSs based on the 

estimated exposed population, 

including sensitive populations. UCMR 

4 findings indicate the estimated 

population exposed to permethrin at 

levels of public health concern is 0%. 

(e) Preliminary Regulatory 

Determination for Permethrin 

The agency is making a preliminary 

determination to not regulate 

permethrin with an NPDWR after 

evaluating health, occurrence and other 

related information against the three 

SDWA statutory criteria. While data 

suggest that permethrin may have an 

adverse effect on human health, the 

occurrence data indicate that 

permethrin is not occurring or not likely 

to occur in PWSs with a frequency and 

at levels of public health concern. 

Therefore, the agency has made the 

preliminary determination that an 

NPDWR for permethrin would not 

present a meaningful opportunity to 

reduce health risk for persons served by 

PWSs. The Regulatory Determination 5 

Support Document (USEPA, 2024b) 

presents additional information and 

analyses supporting the agency’s 

evaluation of permethrin. 

7. Profenofos 

(a) Background 

Profenofos is an organophosphate 

pesticide that is applied as an 

insecticide. Synonyms for profenofos 

include curacron and selecron (NCBI, 

2023b). Profenofos was first registered 

in the U.S. in 1982 (USEPA, 2008c). 

Profenofos registration was canceled in 

2018 and it currently has no active 

labels in the EPA’s Pesticide Product 

and Label System database (USEPA, 

2023c). USGS Pesticide Use Maps show 

cotton is the sole crop to which 

profenofos was applied in the years 

before cancellation; usage diminished 

since the mid-1990s and ceased around 

2011 according to these records. 

Environmental fate assessments 

indicate that low to slight mobility in 

soil and transport to water is expected 

based on Koc values. Volatilization from 

water is not expected to occur based on 

the contaminant’s Henry’s Law 

Constant; thus it will remain once 

present in water (NCBI, 2023b). In soil 

and water, biodegradation may occur, 

but profenofos is stable to photolysis in 

these media and is not likely to degrade 

with exposure to sunlight. 

(b) Statutory Criterion 1 (Adverse Health 

Effects) 

Exposure to profenofos may have an 

adverse effect on the health of persons 

as supported by the health assessment 

identified for RD 5 (USEPA, 2015d; 

USEPA, 2015g). For pesticide chemicals 

currently registered under FIFRA, 

including profenofos, toxicity 

information from EPA OPP HED HHRAs 

was used as the basis for HRL derivation 

(USEPA, 2024b). 

The health assessment selected to 

derive an HRL for profenofos is the 2015 

EPA OPP HHRA (USEPA, 2015d; 

USEPA, 2015g). The EPA selected a 

chronic toxicity and carcinogenicity 

study in rats (Burdock et al., 1981) as 

the critical study to derive an oral 

reference value for profenofos (see 

section 9.3 of Chapter 9 in the 

Regulatory Determination 5 Support 

Document for more details about the 

critical study). A BMDL10 of 0.12 mg/kg/ 

day based on RBC AChE inhibition was 

identified as the critical effect and POD 

for dietary exposure, as this was the 

most sensitive endpoint measured 

(USEPA, 2015g). After applying the total 

UF of 1,000, the oral reference value 

was calculated to be 0.00012 mg/kg/day 

(USEPA, 2015g) and the EPA selected 

this oral reference value to derive an 

HRL for profenofos. 

The EPA extrapolated the body 

weight of the rodents to their 

approximate age at the onset of 

exposure in the critical study (Burdock 

et al., 1981) to determine the most 

sensitive lifestage exposed. Because 

exposure was estimated to have begun 

during postnatal development (i.e., at 

approximately seven to eight weeks of 

age), the EPA used the DWI–BW 

representing the 90th percentile 


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consumers-only, two-day average, direct 

and indirect community water 

consumption for children (birth to <21 

years) of 0.0343 L/kg/day (USEPA, 

2019a) to derive the HRL for profenofos 

(see decision logic provided in section 

B.6.1.2 of the RD 5 Protocol, found in 

Appendix B of the Regulatory 

Determination 5 Support Document). 

Following HRL derivation practices, 

the EPA derived an HRL for profenofos 

of 0.7 mg/L after rounding to one 

significant figure, based on an oral 

reference value of 0.00012 mg/kg/day 

(USEPA, 2015d; USEPA, 2015g), a DWI– 

BW of 0.0343 L/kg/day (USEPA, 2019a) 

and a 20% RSC (USEPA, 2000a). 

Based on these analyses, the EPA 

finds that profenofos may have an 

adverse effect on the health of persons 

and therefore that Statutory Criterion 1 

is met. 

(c) Statutory Criterion 2 (Occurrence) 

The EPA proposes to find that 

profenofos does not occur with a 

frequency and at levels of public health 

concern in PWSs after evaluation of 

information from the following sources: 

UCMR 4, Consumer Confidence Reports 

(CCRs) from PWSs, USDA PDP, USGS 

PMP. 

The primary occurrence data for 

profenofos are nationally representative 

drinking water monitoring data from the 

UCMR 4 program (2018–2020). The 

MRL for profenofos was 0.3 mg/L. Under 

UCMR AM, 37,287 samples collected 

from 5,028 PWSs were analyzed for 

profenofos and profenofos was detected 

in only four systems (0.08%). One 

system reported a result above the HRL 

of 0.7 mg/L. This comprehensive dataset 

suggests that profenofos is not present 

in public water systems at 

concentrations that would pose a risk to 

human health. 

Ambient water data from the USGS 

NAWQA program and NWIS database 

were evaluated. In NAWQA Cycle 1, 

profenofos was not detected in any 

samples at any sites. In Cycle 2, 

profenofos was detected only once, in 

surface water, and the detection was 

below the HRL. In Cycle 3, profenofos 

was detected in 0.06% of both 

groundwater and surface water samples. 

The highest concentration observed in 

surface water is less than the 1⁄2 HRL 

threshold. In NWIS, profenofos was 

detected in a single surface water 

sample representing 0.2% of surface 

water sites. There were no detections in 

groundwater. The single surface water 

detection had a profenofos 

concentration of 0.00019 mg/L, which is 

less than the 1⁄2 HRL threshold. 

Based on the evaluation of these data 

sources, the EPA finds that profenofos 

does not occur and is not likely to occur 

in PWSs with a frequency and at levels 

of public health concern. Therefore, the 

EPA finds that Statutory Criterion 2 is 

not met. 

(d) Statutory Criterion 3 (Meaningful 

Opportunity) 

Regulating profenofos under the 

SDWA does not present a meaningful 

opportunity for health risk reduction for 

persons served by PWSs based on the 

estimated exposed population. The 

estimated population exposed to 

profenofos at levels of public health 

concern in drinking water is less than 

0.005%. 

(e) Preliminary Regulatory 

Determination for Profenofos 

The agency is making a preliminary 

determination not to regulate profenofos 

with an NPDWR after evaluating health, 

occurrence and other related 

information against the three SDWA 

statutory criteria. While data suggest 

that profenofos may have an adverse 

effect on human health, occurrence data 

indicate that profenofos is not occurring 

or not likely to occur in PWSs with a 

frequency and at levels of public health 

concern. 

Therefore, the agency has determined 

that an NPDWR for profenofos would 

not present a meaningful opportunity to 

reduce health risk for persons served by 

PWSs. The Regulatory Determination 5 

Support Document (USEPA, 2024b) 

presents additional information and 

analyses supporting the agency’s 

evaluation of profenofos. 

8. Tebuconazole 

(a) Background 

Tebuconazole is a 

monochlorobenzene, triazole and 

tertiary alcohol that is used as a 

fungicide. It was first registered by the 

EPA in 1983 (USEPA, 2023d). 

Synonyms for tebuconazole include 

folicur, terbutrazole, ethyltrianol and 

fenetrazole (NCBI, 2023c). 

The USGS provides estimates for 

annual usage of U.S. pesticides, 

including tebuconazole. The USGS 

pesticide use data show that there has 

been an increase in tebuconazole use 

over the past few decades, peaking in 

2015 at over 2.5 million pounds and 

then remaining steady at around 2.0 

million pounds per year from 2016 to 

2019 (USGS, 2023). 

Tebuconazole is expected to have a 

high likelihood of partitioning to water 

based on its Henry’s Law Constant, and 

volatilization from water is not expected 

(NCBI, 2023c). Tebuconazole is 

expected to be persistent in soils and 

water based on the soil aerobic 

metabolism half-life of approximately 

800 days, as well as resistance to 

photolysis in water and soil (USEPA, 

2000b; NCBI, 2023c). 

(b) Statutory Criterion 1 (Adverse Health 

Effects) 

Exposure to tebuconazole may have 

an adverse effect on the health of 

persons as supported by the health 

assessment identified for RD 5 (USEPA, 

2021d; USEPA, 2021e). For pesticide 

chemicals currently registered under the 

FIFRA, including tebuconazole, toxicity 

information from EPA OPP HED HHRAs 

was used as the basis for HRL derivation 

(USEPA, 2024b). 

The health assessment selected to 

derive an HRL for tebuconazole is the 

2021 EPA OPP HHRA (USEPA, 2021d; 

USEPA, 2021e). The EPA selected a 

developmental toxicity study in mice 

(Becker and Biedermann, 1995) as the 

critical study to derive the oral reference 

value (see section 10.3 of Chapter 10 in 

the Regulatory Determination 5 Support 

Document for more details about the 

critical study). A NOAEL of 3 mg/kg/ 

day for increased incidence of fetal skull 

and neural tube defects was identified 

as the critical effect and POD, as this 

was the most sensitive endpoint 

measured after gestational exposure to 

tebuconazole via gavage (USEPA, 

2021d). A total UF of 100 was applied 

to the POD: a UFA of 10 and a UFH of 

10 (USEPA, 2021d). After applying the 

total UF of 100, the oral reference value 

was calculated to be 0.03 mg/kg/day and 

the EPA selected this oral reference 

value to derive an HRL for 

tebuconazole. 

Because the mice in the critical study 

(Becker and Biedermann, 1995) were 

exposed to tebuconazole during 

gestation only (i.e., gestation days 6 

through 15), the EPA determined that 

the critical effect in the fetus 

corresponds with gestational exposure 

in humans. The EPA used the DWI–BW 

representing the 90th percentile 

consumers-only, two-day average, direct 

and indirect community water 

consumption for females of 

reproductive age (13 to <50 years) of 

0.0354 L/kg/day (USEPA, 2019a) to 

derive the HRL for tebuconazole, as it is 

more health protective (i.e., greater) 

than the DWI–BW for pregnant women 

(0.0333 L/kg/day) (USEPA, 2019a) (see 

decision logic provided in section 

B.6.1.2 of the RD 5 Protocol, found in 

Appendix B of the Regulatory 

Determination 5 Support Document). 

Following HRL derivation practices, 

the EPA derived an HRL for 

tebuconazole of 200 mg/L after rounding 

to one significant figure, based on an 

oral reference value of 0.03 mg/kg/day 


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(USEPA, 2021d; USEPA, 2021e), a DWI– 

BW of 0.0354 L/kg/day (USEPA, 2019a) 

and a 20% RSC (USEPA, 2000a). 

Based on these analyses, the EPA 

finds that tebuconazole may have an 

adverse effect on the health of persons 

and therefore that Statutory Criterion 1 

is met. 

(c) Statutory Criterion 2 (Occurrence) 

The EPA proposes to find that 

tebuconazole does not occur with a 

frequency and at levels of public health 

concern in PWSs based on the EPA’s 

evaluation of the following occurrence 

information. 

The primary occurrence data for 

tebuconazole are nationally 

representative drinking water 

monitoring data from the UCMR 4 

program (2018–2020). Under UCMR 4 

a.m., 37,286 samples collected from 

5,028 PWSs were analyzed for 

tebuconazole. Tebuconazole was found 

at or above the MRL of 0.2 mg/L in three 

of the 5,028 systems, or 0.06%. 

However, there were no exceedances of 

the HRL (200 mg/L) or the 1⁄2 HRL 

threshold (USEPA, 2024b). Reported 

results ranged from 0.21 to 1.96 mg/L. 

This comprehensive dataset suggests 

that tebuconazole is not present in 

public water systems at concentrations 

that would pose a risk to human health. 

To understand the impact of 

tebuconazole use post UCMR 4, the EPA 

assessed ambient water and limited 

finished water data collected after 2020. 

Sources of such data include CCRs from 

Community Water Systems (CWSs), 

PWSs, USDA PDP, the NAWQA 

program, the NWIS database, STORET 

and several published studies. Data on 

tebuconazole were available from CCRs 

prepared by five CWSs from 2018 to 

2021; tebuconazole was not detected in 

any system. Tebuconazole was included 

in the USDA PDP from 2001 to 2013, 

where it was detected in 2.11% of 2,656 

raw water samples and 2.18% of 3,575 

finished water samples, but no detected 

concentrations exceeded the 1⁄2 HRL 

threshold or the HRL (USDA, 2022). 

Cycle 2 and Cycle 3 of the NAWQA 

program found tebuconazole in surface 

water (17.97% to 26.48% of samples) 

and groundwater (0% to 0.11% of 

samples), but no concentrations 

exceeded the 1⁄2 HRL threshold or the 

HRL (WQP, 2023). Non-NAWQA NWIS 

data (1991–023) show no detected 

concentration greater than the 1⁄2 HRL 

threshold or the HRL in ambient water 

(WQP, 2023). Analysis of STORET data 

from 2003 to 2016 shows that in 2,021 

samples tested for tebuconazole there 

were no detectable concentrations 

(WQP, 2023). 

Based on the evaluation of these data 

sources, the EPA finds that 

tebuconazole does not occur and is not 

likely to occur in PWSs with a 

frequency and at levels of public health 

concern. Therefore, the EPA finds that 

Statutory Criterion 2 is not met. 

(d) Statutory Criterion 3 (Meaningful 

Opportunity) 

Regulating tebuconazole under the 

SDWA does not present a meaningful 

opportunity for health risk reduction for 

persons served by PWSs based on the 

estimated exposed population, 

including sensitive populations. The 

estimated population exposed to 

tebuconazole at levels of public health 

concern is 0%, based on UCMR 4 

finished water data from 2018–2020. 

(e) Preliminary Regulatory 

Determination for Tebuconazole 

The agency is making a preliminary 

determination not to regulate 

tebuconazole with an NPDWR after 

evaluating health, occurrence and other 

related information against the three 

SDWA statutory criteria. While data 

suggest that tebuconazole may have an 

adverse effect on human health, the 

occurrence data indicate that 

tebuconazole is not occurring or not 

likely to occur in PWSs with a 

frequency and at levels of public health 

concern and that regulation of such 

contaminant does not present a 

meaningful opportunity for health risk 

reduction served by PWSs. The 

Regulatory Determination 5 Support 

Document (USEPA, 2024b) and the 

Occurrence Data from the Fourth 

Unregulated Contaminant Monitoring 

Rule (UCMR 4) (USEPA, 2024c) present 

additional information and analyses 

supporting the agency’s evaluation of 

tebuconazole. 

9. Tribufos 

(a) Background 

Tribufos is a thiophosphate pesticide 

that is used as an insecticide and cotton 

defoliant. It was first registered for use 

in the United States in 1961 (USEPA, 

2009b). The EPA conducted a 

Reregistration Eligibility Decision (RED) 

for tribufos in July 2006, which 

included a comprehensive review of the 

available data on its environmental and 

human health effects (USEPA, 2006b). 

Tribufos is not listed on the EPA’s most 

recent list of Restricted Use Pesticides 

(RUP) (USEPA, 2022f). Synonyms for 

tribufos include butifos, butiphos, butyl 

phosphorotrithioate and tribuphos 

(NCBI, 2023d). 

According to TRI data for tribufos 

from the years 1995–2022, on-site 

surface water discharges peaked in 1999 

at 161 pounds and no discharges have 

been reported since 2007, with specific 

usage data indicating fluctuations based 

on agricultural demand and cotton 

acreage with an overall reduction in 

usage since 1999. The reports highlight 

the targeted and seasonal application of 

tribufos, reflecting its specific role in 

cotton production rather than 

widespread use throughout the year 

(USEPA, 2024b). 

Environmental fate assessments with 

organic carbon partitioning coefficient 

(Koc) values of 4,870–12,684 L/kg 

suggest that tribufos will have little to 

no mobility in soil (NCBI, 2023d). Its 

strong adsorption to soil organic matter 

suggests limited mobility in soil, 

minimizing leaching into water. 

Tribufos is less mobile in soil and tends 

to remain near the application site. 

Persistence depends on various factors, 

including degradation and 

environmental conditions (USEPA, 

2024b). 

(b) Statutory Criterion 1 (Adverse Health 

Effects) 

Exposure to tribufos may have an 

adverse effect on the health of persons 

as supported by the health assessment 

identified for RD 5 (USEPA, 2015h; 

USEPA, 2015i). For pesticide chemicals 

currently registered under FIFRA, 

including tribufos, toxicity information 

from EPA OPP HED HHRAs was used as 

the basis for HRL derivation (USEPA, 

2024b). 

The health assessment selected to 

derive an HRL for tribufos is the 2015 

EPA OPP HHRA (USEPA, 2015h; 

USEPA, 2015i). The EPA selected a 

subchronic oral neurotoxicity study in 

rats (Sheets and Gilmore, 2001) as the 

critical study to derive an oral reference 

value for tribufos (see section 11.3 of 

Chapter 11 in the Regulatory 

Determination 5 Support Document for 

more details about the critical study). 

BMD modeling was performed to 

determine a BMDL10 for inhibition of 

RBC ChE in adult female rats. The 

BMDL10 of 0.19 mg/kg/day was 

identified as the critical effect and POD, 

as this was the most sensitive endpoint 

measured (USEPA, 2015h). A total UF of 

1,000 was applied to the POD: a UFA of 

10, a UFH of 10 and an FQPA safety 

factor of 10 to account for uncertainty in 

the human dose-response relationship 

for neurodevelopmental effects. After 

applying the total UF of 1,000, the oral 

reference value was calculated to be 

0.0002 mg/kg/day (USEPA, 2015h) and 

the EPA selected this oral reference 

value to derive an HRL for tribufos. 

Because exposure began during 

postnatal development (i.e., at eight 

weeks of age) in the critical study 


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(Sheets and Gilmore, 2001), the EPA 

used the DWI–BW representing the 90th 

percentile consumers-only, two-day 

average, direct and indirect community 

water consumption for children (birth to 

<21 years) of 0.0343 L/kg/day (USEPA, 

2019a) to derive the HRL for tribufos 

(see decision logic provided in section 

B.6.1.2 of the RD 5 Protocol, found in 

Appendix B of the Regulatory 

Determination 5 Support Document). 

Following HRL derivation practices, 

the EPA derived an HRL for tribufos of 

1 mg/L after rounding to one significant 

figure, based on an oral reference value 

of 0.0002 mg/kg/day (USEPA, 2015h; 

USEPA, 2015i), a DWI–BW of 0.0343 L/ 

kg/day (USEPA, 2019a) and a 20% RSC 

(USEPA, 2000a). 

Based on these analyses, the EPA 

finds that tribufos may have an adverse 

effect on the health of persons and 

therefore that Statutory Criterion 1 is 

met. 

(c) Statutory Criterion 2 (Occurrence) 

The EPA proposes to find that tribufos 

does not occur with a frequency and at 

levels of public health concern in PWSs 

based on the EPA’s evaluation of the 

following occurrence information. 

The primary occurrence data for 

tribufos are nationally representative 

drinking water monitoring data from the 

UCMR 4 program (2018–2020). Tribufos 

was found at or above the MRL of 0.07 

mg/L in 3 (0.008%) of the 37,269 a.m. 

samples analyzed during this 

monitoring period. The estimated 

population exposed to tribufos at levels 

of public health concern is 0%. Detected 

concentrations ranged from 0.0742 mg/L 

to 0.4 mg/L. These detections were found 

at three large systems, representing 

0.06% of systems participating in the 

monitoring program. There were no 

exceedances of the HRL or the 1⁄2 HRL 

threshold. This comprehensive dataset 

suggests that tribufos is not present in 

PWSs at concentrations that would pose 

a risk to human health. 

Based on the evaluation of the 

available data, the EPA finds that 

tribufos does not occur and is not likely 

to occur in PWSs with a frequency and 

at levels of public health concern. 

Therefore, the EPA finds that Statutory 

Criterion 2 is not met. 

(d) Statutory Criterion 3 (Meaningful 

Opportunity) 

Regulating tribufos under the SDWA 

does not present a meaningful 

opportunity for health risk reduction for 

persons served by PWSs based on the 

estimated exposed population, 

including sensitive populations. The 

agency finds that an NPDWR for tribufos 

does not present a meaningful 

opportunity for health risk reduction. 

The assessment also took into 

consideration the use patterns and 

regulatory actions related to tribufos, 

which have led to a decrease in its 

application and potential release into 

the environment. These factors, 

combined with the lack of detection in 

the UCMR 4 program, support the 

conclusion that tribufos does not 

currently represent a risk to public 

health for persons served by PWSs. 

(e) Preliminary Regulatory 

Determination for Tribufos 

The agency is making a preliminary 

determination to not regulate tribufos 

after evaluating health, occurrence and 

other related information against the 

three SDWA statutory criteria. While 

data suggest that tribufos may have an 

adverse effect on human health, the 

occurrence data indicate that tribufos is 

not occurring or not likely to occur in 

PWSs with a frequency and at levels of 

public health concern. Therefore, the 

agency has determined that an NPDWR 

for tribufos would not present a 

meaningful opportunity to reduce 

health risk for persons served by PWSs. 

The Regulatory Determination 5 

Support Document (USEPA, 2024b) 

presents additional information and 

analyses supporting the agency’s 

evaluation of tribufos. 

V. Status of the Agency’s Evaluation of 

1,2,3-Trichloropropane, 1,4-Dioxane, 

Manganese, Quinoline and Strontium 

A. Ongoing Evaluation of Additional 

Phase 3 Contaminants 

In addition to the nine contaminants 

discussed in section IV of this document 

for which the EPA is making 

preliminary negative determinations, 

there are five additional contaminants 

that were evaluated according to the RD 

5 Protocol and proceeded to Phase 3 

based on the robust available health 

effects and occurrence data for finished 

drinking water: 1,2,3-TCP, 1,4-dioxane, 

manganese, quinoline and strontium. As 

discussed earlier in section III.A.3 of 

this document, in order to make a 

positive determination, the EPA must 

show that a contaminant meets all three 

statutory criteria relating to health 

effects, occurrence and meaningful 

opportunity for health risk reduction, 

while the agency makes a negative 

determination if any one of the criteria 

is not met. 

The EPA is continuing to analyze the 

available health and occurrence data for 

these contaminants to evaluate whether 

they occur at levels of public health 

concern in finished drinking water and 

to characterize the potential meaningful 

opportunity for health risk reduction if 

they were to be regulated under the 

SDWA. Therefore, the EPA is not 

making preliminary determinations for 

these five contaminants at this time. As 

noted in section III.A.3 of this 

document, the 2023 panel ruling from 

the D.C. Circuit Court of Appeals in 

NRDC v. EPA (D.C. Cir., 2023) 

established that the agency cannot 

withdraw a positive determination even 

if evidence identified during the 

rulemaking would change the EPA’s 

conclusion of the potential for 

meaningful opportunity for health risk 

reduction by regulating a contaminant. 

Prior to this ruling, formal evaluation of 

the potential health benefits and 

analysis of the availability and 

feasibility of treatment options were 

conducted during the rule development 

process as part of the HRRCA. Because 

of the 2023 ruling, however, the EPA 

now has concluded that while the 

SDWA does not require a full HRRCA as 

part of regulatory determination prior to 

rule development, the agency will need 

to conduct preliminary benefits 

analyses, treatment feasibility analyses 

or both prior to making determinations 

for contaminants that may warrant 

regulation under the SDWA. The EPA 

will evaluate for each contaminant the 

population exposed at the health level 

of concern along with several other 

factors to determine if regulation 

presents a meaningful opportunity for 

health risk reduction. Therefore, the 

EPA intends to conduct such analyses 

for each of these five contaminants prior 

to making regulatory determinations, in 

order to better understand whether there 

would be a meaningful opportunity for 

health risk reduction for persons served 

by PWSs if the contaminant were to be 

regulated. 

B. Phase 3 Contaminant Updates 

1. 1,2,3-Trichloropropane 

1,2,3-Trichloropropane (1,2,3-TCP) is 

a synthetic chemical used as an 

industrial solvent, a cleaning and 

degreasing agent and a synthesis 

intermediate. 

Since the EPA last provided an 

update on the evaluation of 1,2,3-TCP in 

the RD 4 FRN (USEPA, 2021a), the EPA 

has continued work on the evaluation of 

this contaminant. Work has focused on 

addressing issues related to the 

analytical method MRL being 

substantially higher than the level of 

public health concern which presents 

uncertainty in assessing the potential 

contaminant concentrations and 

exposure analysis. The fact that the 

MRL is much higher than the HRL 


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suggests that there may be a substantial 

amount of occurrence of 1,2,3-TCP at 

levels of public health concern in water 

systems that would not show up in the 

occurrence data, as any measurement 

results below the MRL would not be 

reported. The EPA did not make a 

regulatory determination for 1,2,3-TCP 

during RD 4 due to this analytical 

method limitation, and the agency 

needs lower-level occurrence 

information prior to making a 

preliminary regulatory determination 

for 1,2,3-TCP. Method development 

work is underway to lower the MRL for 

1,2,3-TCP under Method 524.3, which 

would enable reporting of 

concentrations closer to levels of public 

health concern. The EPA intends to 

consider new information related to the 

improved analytical method in future 

regulatory determination efforts to 

assess whether there would be a 

meaningful opportunity for health risk 

reduction if the EPA were to regulate 

1,2,3-TCP in drinking water. 

2. 1,4-Dioxane 

1,4-Dioxane is a cyclic aliphatic ether 

that is used as a solvent and a solvent 

stabilizer. As a solvent it is used in such 

products as inks, coatings, adhesives, 

oils, resins, waxes, and dyes (USEPA, 

2024b). The EPA is continuing its efforts 

to evaluate 1,4-dioxane to determine in 

what manner to regulate this 

contaminant under SDWA and under 

the Toxic Substances Control Act 

(TSCA). The EPA evaluated 1,4-dioxane 

in RD 4 but did not make a regulatory 

determination at that time (USEPA, 

2021a), referencing the status of the 

TSCA risk evaluation and the Health 

Canada health effects assessment, which 

had not been finalized at that time 

(Health Canada, 2018). During the 

timeframe of preliminary RD 5 

evaluation, the EPA finalized the 2024 

Supplement to the 2020 Risk Evaluation 

and a revised Risk Determination for 

1,4-dioxane under the TSCA program. 

In the TSCA Risk Evaluation, which 

covers all conditions of use of 1,4- 

dioxane, the EPA found that 1,4-dioxane 

presents risk to the general population 

via drinking water sourced from surface 

water contaminated both by industrial 

discharges of 1,4-dioxane and down-thedrain releases of products that contain 

1,4-dioxane (generated as an 

unintentional byproduct). Under section 

6 of TSCA, if at the end of the TSCA risk 

evaluation process, the EPA determines 

that a chemical presents an 

unreasonable risk to health or the 

environment, the agency must 

immediately start the risk management 

process to reduce or eliminate these 

risks. TSCA directs the EPA to 

coordinate actions taken under TSCA 

with actions taken under other federal 

laws administered by the EPA, such as 

the Clean Water Act (CWA) and the 

SDWA. TSCA section 9 also provides 

that, if the EPA Administrator 

determines that a risk to health or the 

environment associated with a chemical 

substance could be eliminated or 

reduced to a sufficient extent by actions 

taken under those other Federal laws, 

the EPA must use those other laws 

unless the Administrator determines, in 

the Administrator’s discretion, that it is 

in the public interest to protect against 

such risk by actions taken under TSCA. 

Input from all stakeholders is critical to 

the risk management process under 

TSCA. The EPA is committed to 

developing risk management actions for 

chemicals in a way that is transparent 

and includes proactive, meaningful 

outreach and education with the public 

and other stakeholders. The EPA is 

working collaboratively across programs 

to address the unreasonable risk 

identified under TSCA and has 

determined that the risk to human 

health associated with 1,4-dioxane 

exposure via drinking water sourced 

from surface water contaminated with 

both industrial discharges and downthe-drain releases of products 

containing 1,4-dioxane is best managed 

by coordinating actions under both 

TSCA and SDWA. 

As described in the EPA 

Administrator’s memorandum 

‘‘Coordinated Risk Management Action 

on 1,4-Dioxane under section 9(b) of the 

Toxic Substances Control Act’’ released 

alongside the TSCA’s program’s final 

2024 Supplement to the 2020 Risk 

Evaluation and the revised Risk 

Determination for 1,4-dioxane, after the 

agency’s regulatory action to address 

this risk under TSCA is implemented, 

the EPA will re-evaluate under SDWA 

whether there is any remaining risk that 

presents a meaningful opportunity for 

health risk reduction by regulating 1,4- 

dioxane in drinking water. 

3. Manganese 

Manganese is a naturally occurring 

element and is ubiquitous in the 

environment as a component of over 

100 minerals (ATSDR, 2012). 

Manganese compounds are used in a 

variety of industrial production 

processes and applications—production 

data from 2011 to 2019 from the EPA’s 

CDR Program shows that fifteen 

manganese substances were produced or 

imported in quantities greater than one 

million pounds in at least one year and 

that elemental manganese was produced 

in quantities greater than 500 million 

pounds in 2018 (USEPA, 2024b). 

The EPA made a negative regulatory 

determination for manganese in RD 1 

(USEPA, 2003). Since then, new health 

effects information developed for the 

2021 World Health Organization’s 

(WHO) Guidelines for Drinking Water 

Quality indicates exposure to elevated 

levels of manganese in drinking water 

contributes to increased risk for adverse 

neurological effects, such as behavioral 

and sensorimotor effects (WHO, 2021). 

Nationally representative occurrence 

data in finished drinking water were 

collected for manganese in UCMR 4 

(USEPA, 2024c). The EPA continues to 

evaluate the health effects and 

occurrence data for manganese and will 

conduct preliminary benefits analysis 

and treatment feasibility analysis to 

inform the potential meaningful 

opportunity for health risk reduction if 

manganese were to be regulated under 

the SDWA in the future. 

4. Quinoline 

Quinoline is an aromatic heterocyclic 

amine used to make paints, dyes and 

other chemicals. Quinoline is also used 

as a solvent, anatomical specimen 

preservative, corrosion inhibitor, 

antimalarial drug and flavoring agent. 

Nationally representative finished 

water occurrence data for quinoline was 

collected under UCMR4. The analytical 

method MRL for quinoline is greater 

than the level of public health concern 

thus there is uncertainty regarding the 

frequency at which quinoline occurs at 

levels of public health concern in PWSs. 

Therefore, the EPA needs more 

information prior to making a 

preliminary regulatory determination 

for quinoline. 

The EPA continues to evaluate the 

health effects and occurrence data for 

quinoline and plans to conduct 

additional analyses of health benefits 

and possible treatment feasibility to 

inform whether regulating quinoline 

under SDWA would present a 

meaningful opportunity for health risk 

reduction to persons served by PWSs. 

5. Strontium 

Strontium is a naturally occurring 

element, an alkaline earth metal 

typically found in the form of mineral 

compounds. Stable strontium tends to 

dissolve in water, and therefore water in 

contact with strontium-laden soils may 

also contain strontium. 

Since the RD 4 FRN was published in 

2021, (USEPA, 2021a) the EPA has 

continued to conduct additional work to 

evaluate the health risks and the 

potential for health risk reduction if 

strontium were to be regulated with an 

NPDWR. For the preliminary RD 5 

evaluation, the EPA identified the 2019 


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15The statute authorizes a nine-month extension 

of this promulgation date. 

Health Canada Guidelines for Drinking 

Water Quality (HC, 2019), because it is 

the most recent health assessment 

identified for strontium and uses the 

best available science in its evaluation 

of noncancer risk. The EPA continues to 

evaluate the UCMR 3 occurrence data in 

light of the newer health effects 

information to determine whether there 

would be a meaningful opportunity for 

health risk reduction if strontium were 

to be regulated under the SDWA. In 

addition, the EPA understands that 

strontium may co-occur with beneficial 

calcium in some drinking water systems 

and treatment technologies that remove 

strontium may also remove calcium. 

The agency is evaluating the 

effectiveness of treatment technologies 

under different water conditions, 

including calcium concentrations. 

The EPA continues to evaluate the 

health effects and occurrence data for 

strontium and plans to conduct 

additional analyses of health benefits 

and possible treatment feasibility to 

inform whether regulating strontium 

under SDWA would present a 

meaningful opportunity for health risk 

reduction to persons served by PWSs. 

In summary, the EPA is not making 

regulatory determinations at this time 

for these five contaminants in this 

document. In light of the decision 

announced in NRDC v. EPA (D.C. Cir., 

2023), the EPA plans to conduct 

preliminary health benefits analyses to 

inform whether there would be a 

potential meaningful opportunity for 

health risk reduction through regulation 

of a contaminant with an NPDWR. In 

addition, the EPA continues to evaluate 

the effectiveness and feasibility of 

treatment methods to lower 

concentrations of these contaminants 

from drinking water systems. 

VI. The EPA’s Request for Comments

and Next Steps

The EPA invites commenters to 

submit any relevant data or information 

pertaining to the preliminary regulatory 

determinations identified in this 

document, as well as other relevant 

comments. The EPA will consider the 

public comments and any new, relevant 

data submitted for the contaminants 

discussed in this document and in the 

supporting rationale. 

The data and information requested 

by the EPA include peer-reviewed 

science and supporting studies 

conducted in accordance with sound 

and objective scientific practices, and 

data collected by accepted methods or 

best available methods (if the reliability 

of the method and the nature of the 

review justifies use of the data). 

Peer-reviewed data are studies/ 

analyses that have been reviewed by 

qualified individuals (or organizations) 

who are independent of those who 

performed the work, but who are 

collectively equivalent in technical 

expertise (i.e., peers) to those who 

performed the original work. A peer 

review is an in-depth assessment of the 

assumptions, calculations, 

extrapolations, alternate interpretations, 

methodology, acceptance criteria and 

conclusions pertaining to the specific 

major scientific or technical work 

products and the documentation that 

supports them (USEPA, 2015j). 

Specifically, the EPA is requesting 

comment and information related to the 

following aspects: 

• The health effects information

considered by the agency in making the 

preliminary determinations described in 

this Document. The EPA requests 

commenters identify any additional 

peer reviewed studies that could inform 

the final regulatory determination. 

• Drinking water occurrence

information considered by the agency in 

making the preliminary determinations 

described in this document. The EPA 

requests commenters identify any 

additional data and studies on the 

occurrence of these contaminants in 

drinking water. 

The EPA intends to evaluate the 

public comments received on the nine 

preliminary determinations and issue 

final regulatory determinations. If the 

agency makes a final determination to 

regulate any of the contaminants, the 

EPA intends to propose an NPDWR 

within 24 months and promulgate a 

final NPDWR within 18 months 

following the proposal.15 In addition, 

the EPA will also consider information 

provided in public comment about the 

five contaminants discussed in section 

V of this document to inform potential 

future regulatory determinations. 

VII. References

Agency for Toxic Substances and Disease

Registry (ATSDR). 2012. Toxicological 

Profile for Manganese. U.S. Department 

of Health and Human Services, Public 

Health Service. https://wwwn.cdc.gov/ 

TSP/ToxProfiles/ToxProfiles.aspx?

id=102&tid=23. 

ATSDR. 2020. Toxicological Profile for 

Molybdenum. U.S. Department of Health 

and Human Services, Public Health 

Service. https://www.atsdr.cdc.gov/ 

ToxProfiles/tp212.pdf. 

Becker, H., and Biedermann, K. 1995. HWG 

1608 Technical (c.n. Tebuconazole): 

Embryotoxicity Study (Including 

Teratogenicity) and Supplementary 

Embryotoxicity Study (Including 

Teratogenicity) in the Mouse: Lab Project 

Number: 106899: 319443: 353294. 

Unpublished study prepared by RCC, 

Research and Consulting Co., Ltd. and 

RCC Umweltchemie AG. 921 p. 

Burdock, G.A., L.E. Dudeck, R.D. Alsacker, D. 

Suchmann-Purvis, and S. Fieser. 1981. 

Two-Year Chronic Oral Toxicity Study 

in Albino Rats with Technical CGA 

15324.Unpublished report No. 483–134 

from Hazleton, Inc., Vienna, Virginia, 

USA. Submitted to WHO by Syngenta 

Crop Protection, Greensboro, North 

Carolina, USA. 

Chartier, SW, L.P. Sheets, and B.S. Gilmore. 

2005. Cholinesterase Inhibition in Young 

Adult and Preweanling Wistar Rats 

Treated by Gavage for Eleven Days with 

Ethoprophos. Bayer Global Report 

Number 201317. https://www.bayer.com/ 

en/agriculture/cholinesterase-inhibitionin-young-adult-and-preweanling-wistarrats-treated-by-gavage. 

Chorus, I. and M. Welker, ed. 2021. Toxic 

Cyanobacteria in Water: A Guide to 

Their Public Health Consequences, 

Monitoring and Management, 2nd 

edition. CRC Press and World Health 

Organization. https://

www.taylorfrancis.com/books/oa-edit/ 

10.1201/9781003081449/toxiccyanobacteria-water-ingrid-chorusmartin-welker. 

D.C. Circuit Court (D.C. Cir.). 2023. National

Resources Defense Council v. Michael S.

Regan, Administrator, U.S. 

Environmental Protection Agency and 

Environmental Protection Agency, 67 

F.4th 397. https://casetext.com/case/natres-def-council-v-regan-1.

Funari, E. and E. Testai. 2008. Human Health 

Risk Assessment Related to Cyanotoxins 

Exposure. Critical Reviews in Toxicology, 

38(2): 97–125. https://doi.org/10.1080/ 

10408440701749454. (As cited in USEPA 

2015e.) 

Health Canada (HC). 2017. Guideline 

Technical Document for Canadian 

Drinking Water Quality: Cyanobacterial 

Toxins. ISBN: 978–0–660–07494–8. 

https://www.canada.ca/en/healthcanada/services/publications/healthyliving/guidelines-canadian-drinkingwater-quality-guideline-technicaldocument-cyanobacterial-toxins.html. 

HC. 2018. 1,4-Dioxane in Drinking Water: 

Guideline Technical Document for 

Public Consultation. August. https://

www.canada.ca/content/dam/hc-sc/ 

documents/programs/consultation-1-4- 

dioxane-drinking-water/pub-eng.pdf. 

HC. 2019. Guideline Technical Document— 

Strontium. Guidelines for Canadian 

Drinking Water Quality. Water and Air 

Quality Bureau, Healthy Environments 

and Consumer Safety Branch. H144–13/ 

14–2019E–PDF. https://

publications.gc.ca/collections/ 

collection_2019/sc-hc/H144-13-14-2019- 

eng.pdf. 

Heinze, R. 1999. Toxicity of the 

Cyanobacterial Toxin Microcystin-LR to 

Rats After 28 Days Intake with the 

Drinking Water. Environmental 

Toxicology, 14(1): 57–60. https://doi.org/ 

10.1002/(SICI)1522- 


lotter on DSK11XQN23PROD with NOTICES1
Federal Register / Vol. 90, No. 9 / Wednesday, January 15, 2025 / Notices 3857 

7278(199902)14:1%3C57::AIDTOX9%3E3.0.CO;2-J. 

Humpage, A.R. and I.R. Falconer. 2002. Oral 

Toxicity of Cylindrospermopsin: No 

Observed Adverse Effect Level 

Determination in Male Swiss Albino 

Mice. Research Report 13. Salisbury, 

South Australia: Cooperative Research 

Centre for Water Quality and Treatment. 

ISBN 1876616156. 

Humpage, A.R. and I.R. Falconer. 2003. Oral 

Toxicity of Cyanobacterial Toxin 

Cylindrospermopsin in Male Swiss 

Albino Mice: Determination of No 

Observed Adverse Effect Level for 

Deriving a Drinking Water Guideline 

Value. Environmental Toxicology, 18(2): 

94–103. https://doi.org/10.1002/ 

tox.10104. 

International Programme on Chemical Safety 

(IPCS). 1998. Concise International 

Chemical Assessment Document 

(CICAD) No. 7: o-Toluidine. https://

www.inchem.org/documents/cicads/ 

cicads/cicad07.htm. 

Jackson Labs. 2023. Body Weight Information 

for C57BL/6J (000664). The Jackson 

Laboratory, Bar Harbor, ME. https://

www.jax.org/jax-mice-and-services/ 

strain-data-sheet-pages/body-weightchart-000664. Accessed July 2023. 

Kinnear, S. 2010. Cylindrospermopsin: A 

Decade of Progress on Bioaccumulation 

Research. Marine Drugs, 8(3): 542–564. 

https://doi.org/10.3390%2Fmd8030542. 

Machado, J., A. Campos, V. Vasconcelos, and 

M. Freitas. 2017. Effects of MicrocystinLR and Cylindrospermopsin on PlantSoil Systems: A Review of Their 

Relevance for Agricultural Plant Quality 

and Public Health. Environmental 

Research, 153: 191–204. https://doi.org/ 

10.1016/j.envres.2016.09.015. 

Marie, P.J., M.T. Garba, M. Hott, and L. 

Miravet. 1985. Effect of Low Doses of 

Stable Sr on Bone Metabolism in Rats. 

Mineral and Electrolyte Metabolism, 

11(1): 5–13. https://pubmed.ncbi.nlm.

nih.gov/3974537/. 

Murray F.J., F.M. Sullivan, A.K. Tiwary, and 

S. Carey. 2014. 90-Day Subchronic 

Toxicity Study of Sodium Molybdate 

Dihydrate in Rats. Regulatory Toxicology 

and Pharmacology, 70(3): 579–88. 

https://doi.org/10.1016/ 

j.yrtph.2013.09.003. 

National Center for Biotechnology 

Information (NCBI). 2022. PubChem 

Compound Summary for CID 445434, 

Microcystin-LR. https://pubchem.ncbi.

nlm.nih.gov/compound/Microcystin-LR. 

Accessed September 9, 2022. 

NCBI. 2023b. PubChem Compound Summary 

for CID 38779, Profenofos. https://

pubchem.ncbi.nlm.nih.gov/compound/ 

Profenofos. Accessed December 8, 2023. 

NCBI. 2023c. PubChem Compound Summary 

for CID 86102, Tebuconazole. https://

pubchem.ncbi.nlm.nih.gov/compound/ 

Tebuconazole. Accessed December 11, 

2023. 

NCBI. 2023d. PubChem Compound Summary 

for CID 5125, Tribufos. Accessed 

December 11, 2023. https://

pubchem.ncbi.nlm.nih.gov/compound/ 

Tribufos. 

Roberts, V.A., M. Vigar, L. Backer, G.E. 

Veytsel, E.D. Hilborn, E.I. Hamelin, K.L. 

Vanden Esschert, J.Y. Lively, J.R. Cope, 

M.C. Hlavsa, and J.S. Yoder. 2020. 

Surveillance for Harmful Algal Bloom 

Events and Associated Human and 

Animal Illnesses: One Health Harmful 

Algal Bloom System, United States, 

2016–2018. CDC MMWR Weekly, 69(50): 

1889–1894. https://doi.org/10.15585/ 

mmwr.mm6950a2. 

Sheets, L.P. and R.G. Gilmore. 2001. A 

Subchronic Neurotoxicity Screening 

Study with Technical Grade Tribufos 

(DEF®) in Wistar Rats. Bayer 

Corporation, Agriculture Division, 

Toxicology, 17745 South Metcalf Ave., 

Stilwell, Kansas, 66085–9104. Laboratory 

report number 110242; March 26, 2001. 

MRID 45369101. Unpublished. 

Smedley, P.L. and D.G. Kinniburgh. 2017. 

Molybdenum in Natural Waters: A 

Review of Occurrence, Distributions and 

Controls. Applied Geochemistry, 84: 

387–432. https://doi.org/10.1016/ 

j.apgeochem.2017.05.008. 

United States Department of Agriculture 

(USDA). 2022. Pesticide Data Program 

Annual Summary Reports. https://

www.ams.usda.gov/reports/pdp-annualsummary-reports. Published December 

21, 2022. Accessed from https://

www.ams.usda.gov/datasets/pdp/ 

pdpdata. 

United States Environmental Protection 

Agency (USEPA). 1992. Molybdenum; 

CASRN 7439–98–7. National Center for 

Environmental Assessment, Integrated 

Risk Information System, Chemical 

Assessment Summary. https://

iris.epa.gov/static/pdfs/0425_

summary.pdf. 

USEPA. 1998. Announcement of the 

Drinking Water Contaminant Candidate 

List. Federal Register, 63(40): 10273, 

March 2, 1998. https://www.govinfo.gov/ 

content/pkg/FR-1998-03-02/pdf/98- 

5313.pdf. 

USEPA. 1999. Revisions to the Unregulated 

Contaminant Monitoring Regulation for 

Public Water Systems; Final Rule. 

Federal Register, 64(180): 50556, 

September 17, 1999. https://

www.govinfo.gov/content/pkg/FR-1999- 

09-17/pdf/99-23030.pdf. 

USEPA. 2000a. Methodology for Deriving 

Ambient Water Quality Criteria for the 

Protection of Human Health (2000). 

Office of Water, Office of Science and 

Technology. EPA/822/B–00/004. 

October. https://www.epa.gov/sites/ 

default/files/2018-10/documents/ 

methodology-wqc-protection-hh2000.pdf. 

USEPA. 2000b. Section 18—Use of 

Tebuconazole on Hazelnuts in Oregon. 

February 29, 2000, memo from Office of 

Prevention, Pesticides and Toxic 

Substances. https://www3.epa.gov/ 

pesticides/chem_search/cleared_

reviews/csr_PC-128997_29-Feb-00_a.pdf. 

USEPA. 2001a. Statistical Design and Sample 

Selection for the Unregulated 

Contaminant Monitoring Regulation 

(1999). Office of Water. EPA–815–R–01– 

004. August. https://nepis.epa.gov/Exe/ 

ZyPURL.cgi?Dockey=20001YZH.txt. 

USEPA. 2001b. Reference Guide for the 

Unregulated Contaminant Monitoring 

Regulation. Office of Water. EPA 815–R– 

01–023. October. https://nepis.epa.gov/ 

Exe/ 

ZyPURL.cgi?Dockey=20001ZBP.TXT. 

USEPA. 2002. A Review of the Reference 

Dose and Reference Concentration 

Process. Risk Assessment Forum. EPA/ 

630/P–02/002F. December. https://

www.epa.gov/sites/default/files/2014-12/ 

documents/rfd-final.pdf. 

USEPA. 2003. Announcement of Regulatory 

Determinations for Priority 

Contaminants on the Drinking Water 

Contaminant Candidate List. Federal 

Register, 68(138): 42898, July 18, 2003. 

https://federalregister.gov/a/03-18151. 

USEPA. 2005a. Drinking Water Contaminant 

Candidate List 2; Final Notice. Federal 

Register, 70(36): 9071, February 24, 

2005. https://federalregister.gov/a/05- 

3527. 

USEPA. 2005b. Guidelines for Carcinogen 

Risk Assessment. Risk Assessment 

Forum. EPA/630/P–03/001F. March. 

https://www.epa.gov/sites/default/files/ 

2013-09/documents/cancer_guidelines_

final_3-25-05.pdf. 

USEPA. 2006a. Reregistration Eligibility 

Decision for Ethoprop. Includes July 31, 

2006, finalization memo and EPA 738– 

R–06–018. Office of Prevention, 

Pesticides, and Toxic Substances. 

https://archive.epa.gov/pesticides/ 

reregistration/web/pdf/ethoprop_red.pdf. 

USEPA. 2006b. Reregistration Eligibility 

Decision for Tribufos. Includes July 31, 

2006, finalization memo and EPA 738– 

R–00–022. Office of Prevention, 

Pesticides, and Toxic Substances. 

https://www3.epa.gov/pesticides/chem_

search/reg_actions/reregistration/red_

PC-074801_31-Jul-06.pdf. 

USEPA. 2007. Unregulated Contaminant 

Monitoring Regulation (UCMR) for 

Public Water Systems Revisions. Federal 

Register, 72(2): 367, January 4, 2007. 

https://www.govinfo.gov/content/pkg/ 

FR-2007-01-04/pdf/E6-22123.pdf. 

USEPA. 2008a. Drinking Water: Regulatory 

Determinations Regarding Contaminants 

on the Second Drinking Water 

Contaminant Candidate List. Federal 

Register, 73(147): 44251, July 30, 2008. 

https://federalregister.gov/a/E8-17463. 

USEPA. 2008b. The Analysis of Occurrence 

Data from the First Unregulated 

Contaminant Monitoring Regulation 

(UCMR 1) in Support of Regulatory 

Determinations for the Second Drinking 

Water Contaminant Candidate List (CCL 

2). EPA 815–R–08–013. https://

www.epa.gov/sites/default/files/2014-09/ 

documents/the_analysis_of_occurrence_

data_from_ucmr1_in_support_of_

rd2.pdf. 

USEPA. 2008c. Profenofos Summary 

Document, Registration Review: Initial 

Docket, June 2008. https://

www.regulations.gov/document/EPAHQ-OPP-2008-0345-0002. 

USEPA. 2009a. Drinking Water Contaminant 

Candidate List 3—Final. Federal 

Register, 74(194): 51850, October 8, 


lotter on DSK11XQN23PROD with NOTICES1
3858 Federal Register / Vol. 90, No. 9 / Wednesday, January 15, 2025 / Notices 

2009. https://federalregister.gov/a/E9- 

24287. 

USEPA. 2009b. Tribufos Summary 

Document, Registration Review: Initial 

Docket, March 2009. https://

www.regulations.gov/document/EPAHQ-OPP-2008-0883-0004. 

USEPA. 2011. Drinking Water: Regulatory 

Determination on Perchlorate. Federal 

Register, 76(29): 7762, February 11, 

2011. https://federalregister.gov/a/2011- 

2603. 

USEPA. 2012a. Revisions to the Unregulated 

Contaminant Monitoring Regulation 

(UCMR 3) for Public Water Systems. 

Federal Register, 77(85): 26071, May 2, 

2012. https://www.govinfo.gov/content/ 

pkg/FR-2012-05-02/pdf/2012-9978.pdf. 

USEPA. 2012b. Provisional Peer-Reviewed 

Toxicity Values for o-Toluidine (CASRN 

95–53–4). Office of Research and 

Development’s National Center for 

Environmental Assessment, Superfund 

Health Risk Technical Support Center. 

EPA/690/R–12/032F. December. https://

cfpub.epa.gov/ncea/pprtv/documents/ 

ToluidineoMethylaniline2.pdf. 

USEPA. 2014. Announcement of Preliminary 

Regulatory Determinations for 

Contaminants on the Third Drinking 

Water Contaminant Candidate List. 

Federal Register, 79(202): 62716, 

October 20, 2014. https://

www.govinfo.gov/content/pkg/FR-2014- 

10-20/pdf/2014-24582.pdf. 

USEPA. 2015a. Occurrence Data from the 

Second Unregulated Contaminant 

Monitoring Regulation (UCMR 2). Office 

of Water. EPA–815–R–15–013. 

December. https://www.regulations.gov/ 

document/EPA-HQ-OW-2012-0155-0030. 

USEPA. 2015b. Health Effects Support 

Document for the Cyanobacterial Toxin 

Cylindrospermopsin. Office of Water, 

Health and Ecological Criteria Division. 

EPA–820R15103. June. https://

www.epa.gov/sites/default/files/2017-06/ 

documents/cylindrospermopsin-supportreport-2015.pdf. 

USEPA. 2015c. Ethoprop: Draft Human 

Health Risk Assessment for Registration 

Review. September 15, 2015, memo from 

Office of Chemical Safety and Pollution 

Prevention, Office of Pesticide Programs, 

Health Effects Division. DP D410028. 

https://www.regulations.gov/document/ 

EPA-HQ-OPP-2008-0560-0028. 

USEPA. 2015d. Pesticide Registration: Draft 

Human Health and Ecological Risk 

Assessments for Sulfonylureas and 

Certain Other Pesticides. Federal 

Register, 80(186): 57812–57816, Sept 25, 

2015. https://www.federalregister.gov/ 

documents/2015/09/25/2015-24452/ 

pesticide-registration-review-drafthuman-health-and-ecological-riskassessments-for-sulfonylureas. 

USEPA. 2015e. Health Effects Support 

Document for the Cyanobacterial Toxin 

Microcystins. EPA–820R15102. June. 

https://www.epa.gov/sites/default/files/ 

2017-06/documents/microcystinssupport-report-2015.pdf. 

USEPA. 2015f. Drinking Water Health 

Advisory for the Cyanobacterial 

Microcystin Toxins. EPA–820R15100. 

June. https://www.epa.gov/sites/default/ 

files/2017-06/documents/microcystinsreport-2015.pdf. 

USEPA. 2015g. Profenofos: Human Health 

Draft Risk Assessment (DRA) for 

Registration Review. September 15, 2015 

memo from Office of Chemical Safety 

and Pollution Prevention. DP D414150. 

https://www.regulations.gov/document/ 

EPA-HQ-OPP-2008-0345-0024. 

USEPA. 2015h. Tribufos: Human Health 

Draft Risk Assessment for Registration 

Review. September 15, 2015, memo from 

Office of Chemical Safety and Pollution 

Prevention. DP D357537. https://

www.regulations.gov/document/EPAHQ-OPP-2008-0883-0011. 

USEPA. 2015i. Pesticide Registration Review; 

Draft Human Health and Ecological Risk 

Assessments for Certain 

Organophosphates; Extension of 

Comment Period. Federal Register, 

80(246): 79888–79889, December 23, 

2015. https://www.govinfo.gov/content/ 

pkg/FR-2015-12-23/pdf/2015-32326.pdf. 

USEPA. 2015j. Peer Review Handbook, 4th 

Edition. Science and Technology Policy 

Council. EPA 100–B–15–001. October. 

https://www.epa.gov/osa/peer-reviewhandbook-4th-edition-2015. 

USEPA. 2016a. Announcement of Final 

Regulatory Determinations for 

Contaminants on the Third Drinking 

Water Contaminant Candidate List. 

Federal Register, 81(1): 13, January 4, 

2016. https://www.govinfo.gov/content/ 

pkg/FR-2016-01-04/pdf/2015-32760.pdf. 

USEPA. 2016b. Drinking Water Contaminant 

Candidate List 4—Final. Federal 

Register, 81(222): 81099, November 17, 

2016. https://www.govinfo.gov/content/ 

pkg/FR-2016-11-17/pdf/2016-27667.pdf. 

USEPA. 2016c. Revisions to the Unregulated 

Contaminant Monitoring Rule (UCMR 4) 

for Public Water Systems and 

Announcement of Public Meeting. 

Federal Register, 81(224): 92666, 

December 20, 2016. https://

www.govinfo.gov/content/pkg/FR-2016- 

12-20/pdf/2016-30469.pdf. 

USEPA. 2019a. Exposure Factors Handbook 

Chapter 3 (Update): Ingestion of Water 

and Other Select Liquids. Office of 

Research and Development. EPA/600/R– 

8/259F. https://cfpub.epa.gov/ncea/efp/ 

recordisplay.cfm?deid=343661. 

USEPA. 2019b. Occurrence Data from the 

Third Unregulated Contaminant 

Monitoring Rule (UCMR 3). EPA 815–R– 

19–007. https://www.regulations.gov/ 

document/EPA-HQ-OW-2019-0583-0005. 

USEPA. 2020a. Announcement of 

Preliminary Regulatory Determinations 

for Contaminants on the Fourth Drinking 

Water Contaminant Candidate List. 

Federal Register, 85(47): 14098, March 

10, 2020. https://www.govinfo.gov/ 

content/pkg/FR-2020-03-10/pdf/2020- 

04145.pdf. 

USEPA. 2020b. Pesticide Registration 

Review: Interim Decisions for Several 

Pesticides. Federal Register, 85(206): 

67538–67540, Oct 23, 2020. https://

www.federalregister.gov/documents/ 

2020/10/23/2020-23504/pesticideregistration-review-interim-decisions-forseveral-pesticides-notice-of-availability. 

USEPA. 2020c. Permethrin: Human Health 

Risk Assessment for New Use on ‘‘Fruit, 

Small, Vine Climbing, Except Fuzzy 

Kiwifruit, Subgroup 13–07F’’; Multiple 

Crop Group Conversions/Expansions; 

and the Establishment of a Tolerance 

without a U.S. Registration for Tea, and 

the Revised Draft Risk Assessment (DRA) 

for Registration Review. March 17, 2020, 

memo from Office of Chemical Safety 

and Pollution Prevention, Office of 

Pesticide Programs, Health Effects 

Division. DPs D449288, D455545. 

https://www.regulations.gov/document/ 

EPA-HQ-OPP-2011-0039-0130. 

USEPA. 2021a. Announcement of Final 

Regulatory Determinations for 

Contaminants on the Fourth Drinking 

Water Contaminant Candidate List. 

Federal Register, 86(40): 12272, March 3, 

2021. https://www.govinfo.gov/content/ 

pkg/FR-2021-03-03/pdf/2021-04184.pdf. 

USEPA. 2021b. 2021 Policy on Children’s 

Health. October 5, 2021, memo from 

Administrator Michael S. Regan. https:// 

www.epa.gov/system/files/documents/ 

2021-10/2021-policy-on-childrenshealth.pdf. 

USEPA. 2021c. Revisions to the Unregulated 

Contaminant Monitoring Rule (UCMR 5) 

for Public Water Systems and 

Announcement of Public Meetings. 

Federal Register, 86(245): 73131, 

December 27, 2021. https://

www.govinfo.gov/content/pkg/FR-2021- 

12-27/pdf/2021-27858.pdf. 

USEPA. 2021d. Registration Review Draft 

Risk Assessment for the Antimicrobial 

Uses of Tebuconazole. March 24, 2021, 

memo from Office of Chemical Safety 

and Pollution Prevention. DP 455145. 

https://downloads.regulations.gov/EPAHQ-OPP-2015-0378-0020/content.pdf. 

USEPA. 2021e. Pesticide Registration 

Review; Draft Human Health and/or 

Ecological Risk Assessments for Several 

Pesticides; Notice of Availability. 

Federal Register, 86(97): 27593–27594, 

May 21, 2021. https://www.govinfo.gov/ 

content/pkg/FR-2021-05-21/pdf/2021- 

10715.pdf. 

USEPA. 2022a. Drinking Water Contaminant 

Candidate List 5—Final. Federal 

Register, 87(218): 68060, November 14, 

2022. https://www.govinfo.gov/content/ 

pkg/FR-2022-11-14/pdf/2022-23963.pdf. 

USEPA. 2022b. Drinking Water Health 

Advisory: Hexafluoropropylene Oxide 

(HFPO) Dimer Acid (CASRN 13252–13– 

6) and HFPO Dimer Acid Ammonium 

Salt (CASRN 62037–80–3), Also Known 

as ‘‘GenX Chemicals.’’ Office of Water, 

Office of Science and Technology. EPA/ 

822/R–22/005. June. https://

www.epa.gov/system/files/documents/ 

2022-06/drinking-water-genx-2022.pdf. 

USEPA. 2022c. Drinking Water Health 

Advisory: Perfluorobutane Sulfonic Acid 

(CASRN 375–73–5) and Related 

Compound Potassium Perfluorobutane 

Sulfonate (CASRN 29420–49–3). Office 

of Water, Office of Science and 

Technology. EPA/822/R–22/006. June. 

https://www.epa.gov/system/files/ 

documents/2022-06/drinking-water-pfbsVerDate Sep<11>2014 18:37 Jan 14, 2025 Jkt 265001 PO 00000 Frm 00072 Fmt 4703 Sfmt 4703 E:\FR\FM\15JAN1.SGM 15JAN1

lotter on DSK11XQN23PROD with NOTICES1
Federal Register / Vol. 90, No. 9 / Wednesday, January 15, 2025 / Notices 3859 

2022.pdf. 

USEPA. 2022d. Learn about Cyanobacteria 

and Cyanotoxins. https://www.epa.gov/ 

cyanohabs/learn-about-cyanobacteriaand-cyanotoxins. Accessed September 8, 

2022. 

USEPA. 2022e. National Lakes Assessment 

2017 Web Report. https://www.epa.gov/ 

national-aquatic-resource-surveys/ 

reports-and-data-national-lakesassessment-2017. 

USEPA. 2022f. Restricted Use Product 

Summary Report (October 31, 2022). 

https://www.epa.gov/system/files/ 

documents/2022-11/RUP-Report-10-31- 

2022.pdf. 

USEPA. 2023a. Ethoprop. Updated 

Occupational and Non-Occupational 

Spray Drift Assessment for Registration 

Review. February 17, 2023, memo from 

Office of Chemical Safety and Pollution 

Prevention, Office of Pesticide Programs. 

https://www.regulations.gov/document/ 

EPA-HQ-OPP-2008-0560-0058. 

USEPA. 2023b. Entry for ‘‘Chronic Exposure’’ 

in the Integrated Risk Information 

System (IRIS) Glossary. https://

www.epa.gov/iris/iris-glossary. 

USEPA. 2023c. Pesticide Product and Label 

System Database. https://

ordspub.epa.gov/ords/pesticides/ 

f?p=PPLS:1. 

USEPA. 2023d. Pesticide Chemical Search 

for tebuconazole: https://

ordspub.epa.gov/ords/pesticides/ 

f?p=CHEMICALSEARCH:3::::21,

3,31,7,12,25:P3_XCHEMICAL_ID:3984. 

USEPA. 2024a. PFAS National Primary 

Drinking Water Regulation: Final Rule. 

Federal Register, 89(82): 32532, April 

26, 2024. https://www.govinfo.gov/ 

content/pkg/FR-2024-04-26/pdf/2024- 

07773.pdf. 

USEPA. 2024b. Regulatory Determination 5 

Support Document. EPA 815–B–24–017. 

USEPA. 2024c. Occurrence Data from the 

Fourth Unregulated Contaminant 

Monitoring Rule (UCMR 4). EPA 815–B– 

24–016. 

United States Geological Survey (USGS). 

2023. Estimated Annual Agricultural 

Pesticide Use. https://water.usgs.gov/ 

nawqa/pnsp/usage/maps/index.php. 

Last updated June 14, 2023. 

Water Quality Portal (WQP). 2023. Water 

Quality Portal Data Warehouse. https://

www.waterqualitydata.us/. Data 

Warehouse consulted September 2023. 

Weisburger, E.K., A.B. Russfield, F. 

Homburger, F., J.H. Weisburger, E. Boger, 

C.G. Van Dongen, and K.C. Chu. 1978.

Testing of Twenty-One Environmental

Aromatic Amines or Derivatives for

Long-Term Toxicity or Carcinogenicity.

Journal of Environmental Pathology and

Toxicology, 2(2): 325–356. https://

doi.org/10.1097/00043764-197911000-

00017.

WHO. 2011. Molybdenum in Drinking-Water. 

Background Document for Development 

of WHO Guidelines for Drinking-Water 

Quality. WHO/SDE/WSH/03.04/11/Rev/ 

1. https://cdn.who.int/media/docs/

default-source/wash-documents/washchemicals/molybdenum.pdf?sfvrsn=

d01920eb_4.

WHO. 2020a. Cyanobacterial Toxins: 

Cylindrospermopsins. Background 

Document for Development of WHO 

Guidelines for Drinking-Water Quality 

and Guidelines for Safe Recreational 

Water Environments. WHO/HEP/ECH/ 

WSH/2020.4. https://apps.who.int/iris/ 

bitstream/handle/10665/338063/WHOHEP-ECH-WSH-2020.4-eng.pdf. 

WHO. 2020b. Cyanobacterial Toxins: 

Microcystins. Background Document for 

Development of WHO Guidelines for 

Drinking-Water Quality and Guidelines 

for Safe Recreational Water 

Environments. WHO/HEP/ECH/WSH/ 

2020.6. 

https://cdn.who.int/media/docs/defaultsource/wash-documents/washchemicals/microcystins-background201223.pdf. 

WHO. 2021. Manganese in Drinking-Water. 

Background Document for Development 

of WHO Guidelines for Drinking-Water 

Quality. WHO/HEP/ECH/WSH/2021.5. 

https://iris.who.int/bitstream/handle/ 

10665/350933/WHO-HEP-ECH-WSH2021.5-eng.pdf. 

Wolansky, M.J., C. Gennings, K.M. Crofton. 

2006. Relative Potencies for Acute 

Effects of Pyrethroids on Motor Function 

in Rats. Toxicological Sciences, 89(1): 

271–277. https://doi.org/10.1093/toxsci/ 

kfj020. 

Wong, M.Y., S.D. Rathod, R. Marino, L. Li, 

R.W. Howarth, A. Alastuey, et al. 2021. 

Anthropogenic Perturbations to the 

Atmospheric Molybdenum Cycle. Global 

Biogeochemical Cycles, 35(2): 

e2020GB006787. https://doi.org/10.1029/ 

2020GB006787. 

Jane Nishida, 

Acting Administrator. 

[FR Doc. 2025–00133 Filed 1–14–25; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

[EPA–HQ–OW–2024–0504; FRL 12451–01– 

OW] 

Draft Sewage Sludge Risk Assessment 

for Perfluorooctanoic Acid (PFOA) and 

Perfluorooctane Sulfonic Acid (PFOS) 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Notice of availability. 

SUMMARY: As part of the Environmental 

Protection Agency’s (EPA’s) 

commitment to safeguarding the 

environment from per- and 

polyfluoroalkyl substances (PFAS), the 

agency is announcing the availability of 

the ‘‘Draft Sewage Sludge Risk 

Assessment for Perfluorooctanoic Acid 

(PFOA) and Perfluorooctane Sulfonic 

Acid (PFOS)’’ for a 60-day public 

comment period. This draft risk 

assessment reflects the agency’s latest 

scientific understanding of the potential 

risks to human health and the 

environment posed by the presence of 

PFOA and PFOS in sewage sludge that 

is land applied as a soil conditioner or 

fertilizer (on agricultural, forested, and 

other lands), surface disposed, or 

incinerated. The draft risk assessment 

focuses on those living on or near 

impacted sites or those that rely 

primarily on their products (e.g., food 

crops, animal products, drinking water); 

the draft risk assessment does not model 

risks for the general public. This draft 

risk assessment underwent independent 

external peer review, and the EPA 

revised the document accordingly. Once 

finalized, the risk assessment will 

provide information on risk from use or 

disposal of sewage sludge and will 

inform the EPA’s potential future 

regulatory actions under the Clean 

Water Act (CWA). 

DATES: Comments must be received on 

or before March 17, 2025. 

ADDRESSES: The EPA has established a 

docket for the ‘‘Draft Sewage Sludge 

Risk Assessment for Perfluorooctanoic 

Acid (PFOA) and Perfluorooctane 

Sulfonic Acid (PFOS)’’ action under 

Docket ID No EPA–HQ–OW–2024–0504. 

You may send comments, identified by 

Docket ID No. EPA–HQ–OW–2024– 

0504, by any of the following methods: 

• Federal eRulemaking Portal:

https://www.regulations.gov/ (our 

preferred method). Follow the online 

instructions for submitting comments. 

• Mail: U.S. Environmental

Protection Agency, EPA Docket Center, 

Office of Water Docket, Mail Code 

28221T, 1200 Pennsylvania Avenue 

NW, Washington, DC 20460. 

• Hand Delivery or Courier: EPA

Docket Center, WJC West Building, 

Room 3334, 1301 Constitution Avenue 

NW, Washington, DC 20004. The Docket 

Center’s hours of operations are 8:30 

a.m. to 4:30 p.m., Monday through

Friday (except Federal Holidays).

Instructions: All submissions received 

must include the Docket ID No. for this 

rulemaking. Comments received may be 

posted without change to https://

www.regulations.gov/, including any 

personal information provided. For 

detailed instructions on sending 

comments and additional information 

on the rulemaking process, see the 

‘‘Public Participation—Written 

comments’’ heading of the 

SUPPLEMENTARY INFORMATION section of 

this document. 

FOR FURTHER INFORMATION CONTACT: 

David Tobias, Health and Ecological 

Criteria Division, Office of Science and 

Technology, Office of Water, 

Environmental Protection Agency; email 

address: biosolidsprogram@epa.gov. 


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