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Federal Register / Vol. 86, No. 40 / Wednesday, March 3, 2021 / Rules and Regulations regulatory determination RD 3 in order to further consider additional studies related to strontium exposure.
Of the eight remaining CCL 4
contaminants PFOS, PFOA, 1,1dichloroethane, acetochlor, methyl bromide, metolachlor, nitrobenzene, and RDX evaluated in Phase 3 against the three statutory criteria, including an evaluation of level and frequency of occurrence in drinking water, the size of the population exposed to concentrations of health concern, and information on sensitive populations and lifestages 1 e.g., pregnant women, infants and children, the Agency made preliminary regulatory determinations to regulate PFOS and PFOA and to not regulate the remaining six contaminants. These preliminary determinations, with their supporting analyses and documentation, were published in the Federal Register on March 10, 2020, for public comment USEPA, 2020a. The public comment period was initially intended to run through May 11, 2020. In response to stakeholder requests, on April 30, 2020, EPA extended the comment period by 30 days to June 10, 2020.

B. Consideration of Public Comments EPA received comments from approximately 11,600 organizations and individuals on the March 10, 2020, Federal Register document including 12
states California, Colorado, Connecticut, Indiana, Massachusetts, Michigan, Missouri, New Hampshire, New Mexico, South Carolina, West Virginia, and Wisconsin. Comments on specific contaminants, and EPAs responses, are briefly summarized in the sections below. The Agency prepared a response-to-comments document for this action USEPA, 2021b that is available in the Public Docket at www.regulations.gov under Docket ID
No. EPAHQOW20190583. The response-to-comments document is organized in a manner similar to this document and generally contains more detailed responses to the public comments received than those found in this document.
IV. EPAs Findings on Specific Contaminants After considering the public comments, EPA is making final regulatory determinations to regulate PFOS and PFOA and to not regulate 1,1dichloroethane, acetochlor, methyl
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bromide, metolachlor, nitrobenzene, and RDX.
This document provides a brief description of the Agency findings on these contaminants. Details on the background, health and occurrence information, and analyses used to evaluate and make final determinations for these contaminants can be found in the Final Regulatory Determination 4
Support Document USEPA, 2021a and the Federal Register publication for the preliminary regulatory determination USEPA, 2020a.
For each contaminant, the Agency reviewed the available human and toxicological data, derived a health reference level HRL,2 analyzed data on occurrence in drinking water, and estimated the population likely exposed to concentrations of the contaminant at levels of health concern in public water systems. The Agency also considered whether information was available on sensitive populations. The Agency used the findings to evaluate the contaminants against the three SDWA
statutory criteria. Table 1 gives a summary of the health and occurrence information for the eight contaminants with final determinations under RD 4.

TABLE 1SUMMARY OF THE HEALTH AND OCCURRENCE INFORMATION AND THE FINAL DETERMINATIONS FOR THE EIGHT
CONTAMINANTS RECEIVING A FINAL DETERMINATION UNDER RD 4
Occurrence findings from primary data sources Health reference level HRL, g/L

Primary database
PWSs with at least 1 detection >12 HRL

Population served by PWSs with at least 1 detection >12 HRL

PWSs with at least 1 detection >HRL

PFOS

0.07

UCMR 3 AM

95/4,920 1.93%

46/4,920 0.93%

PFOA

0.07

UCMR 3 AM

53/4,920 1.07%

1,1-Dichloroethane Acetochlor

1,000
100

UCMR 3 AM
UCMR 1 AM

0/4,916 0.00%
0/3,869 0.00%
UCMR 1.

UCMR 2 SS

0/1,198 0.00%
UCMR 2.

Methyl Bromide 100
Bromomethane.
Metolachlor 300
Nitrobenzene 10

UCMR 3 AM

0/4,916 0.00%

10,427,193/241 M
4.32%.
3,652,995/241 M
1.51%.
0/241 M 0.00%
0/226 M
0.00%
UCMR 1.
0/157 M
0.00%
UCMR 2.
0/241 M 0.00%

UCMR 2 SS
UCMR 1 AM

0/1,198 0.00%
2/3,861 0.05%

RDX

UCMR 2 AM

0/4,139 0.00%
>15 g/L
3/4,139 0.07%

RD 4 contaminant
30 noncancer
0.4 cancer

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>0.2 g/L

1 https www.epa.gov/children/childhoodlifestages-relating-childrens-environmental-health.
2 An HRL is a health-based concentration against which the Agency evaluates occurrence data when
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0/157 M 0.00%
255,358/226 M
0.11%.
0/229 M 0.00%
>15 g/L
96,033/229 M
0.04%.
>0.2 g/L

13/4,920 0.26%
0/4,916 0.00%
0/3,869 0.00%
UCMR 1.
0/1,198 0.00%
UCMR 2.
0/4,916 0.00%
0/1,198 0.00%
2/3,861 0.05%
0/4,139 0.00%
>30 g/L
3/4,139 0.07%
>0.4 g/L

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
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Population served by PWSs with at least 1 detection >HRL
3,789,831/241 M
1.57%.
490,480/241 M
0.20%.
0/241 M 0.00%
0/226 M
0.00%
UCMR 1.
0/157 M
0.00%
UCMR 2.
0/241 M 0.00%
0/157 M 0.00%
255,358/226 M
0.11%.
0/229 M 0.00%
>30 g/L.
96,033/229 M
0.04%.
>0.4 g/L.

Final determination
Regulate.
Regulate.
Do not regulate.
Do not regulate.

Do not regulate.
Do not regulate.
Do not regulate.
Do not regulate.

and exposure assessment and can be considered a screening value. See Section E.5.1 of the Final Regulatory Determination 4 Support Document for information about how HRLs are derived USEPA, 2021a.

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