Johnston County Water Quality: 2 Cities Ranked by the Records
Johnston County, North Carolina: 2 city reports built from EPA and utility records. A county has many suppliers; each city shows the system that serves it.
Highest result for each contaminant
One row per contaminant: the highest result any system in the county reported, against its limit. Open a row for the systems behind it.
Perfluorooctanoic acid (PFOA)Detected in 2 systems4.0 ng/L federal MCL (2024) · US EPAHighest8.2 ng/L
- CLAYTON, TOWN OF8.2 ng/LSample date: 2024-01-23 to 2024-10-15
- SMITHFIELD, TOWN OF4.7 ng/LSample date: 2024-08-13
Perfluorooctanesulfonic acid (PFOS)Detected in 2 systems4.0 ng/L federal MCL (2024) · US EPAHighest8.1 ng/L
- CLAYTON, TOWN OF8.1 ng/LSample date: 2024-01-23 to 2024-10-15
- SMITHFIELD, TOWN OF7.7 ng/LSample date: 2024-08-13
Perfluorobutanesulfonic acid (PFBS)Detected in 2 systems2,000 ng/L EPA health advisory (screening, not a legal limit) · US EPAHighest4 ng/L
- CLAYTON, TOWN OF4 ng/LSample date: 2024-01-23 to 2024-10-15
- SMITHFIELD, TOWN OF3 ng/LSample date: 2024-08-13
Perfluorohexanoic acid (PFHxA)Detected in 2 systems400,000 ng/L Michigan EGLE state MCL (strictest US state) · Michigan EGLEHighest5.9 ng/L
- CLAYTON, TOWN OF5.9 ng/LSample date: 2024-01-23 to 2024-10-15
- SMITHFIELD, TOWN OF3.1 ng/LSample date: 2024-08-13
Perfluorobutanoic acid (PFBA)Detected in 1 system of 2 testedNo federal or state limit; shown for transparencyHighest6 ng/L
- SMITHFIELD, TOWN OF6 ng/LSample date: 2024-08-13
- CLAYTON, TOWN OFNot detected · below 5.0 ng/L lab reporting limitSample date: 2024-01-23 to 2024-10-15
Perfluoropentanoic acid (PFPeA)Detected in 2 systemsNo federal or state limit; shown for transparencyHighest6.4 ng/L
- CLAYTON, TOWN OF6.4 ng/LSample date: 2024-01-23 to 2024-10-15
- SMITHFIELD, TOWN OF4.2 ng/LSample date: 2024-08-13
25 substances tested, none detected in any systemShow
Tested in these 2 systems: CLAYTON, TOWN OF, SMITHFIELD, TOWN OF
- 11-Chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS)
- 1H, 1H, 2H, 2H-perfluorodecane sulfonic acid (8:2 FTS)
- 1H, 1H, 2H, 2H-perfluorohexane sulfonic acid (4:2 FTS)
- 1H, 1H, 2H, 2H-perfluorooctane sulfonic acid (6:2 FTS)
- 4,8-Dioxa-3H-perfluorononanoic acid (ADONA)
- 9-Chlorohexadecafluoro-3-oxanone-1-sulfonic acid (9Cl-PF3ONS)
- Hexafluoropropylene oxide dimer acid (HFPO-DA) (GenX chemicals)
- Lead (90th percentile)
- Lithium
- N-ethyl perfluorooctanesulfonamidoacetic acid (NEtFOSAA)
- N-methyl perfluorooctanesulfonamidoacetic acid (NMeFOSAA)
- Nonafluoro-3,6-dioxaheptanoic acid (NFDHA)
- Perfluoro (2-ethoxyethane) sulfonic acid (PFEESA)
- Perfluoro-3-methoxypropanoic acid (PFMPA)
- Perfluoro-4-methoxybutanoic acid (PFMBA)
- Perfluorodecanoic acid (PFDA)
- Perfluorododecanoic acid (PFDoA)
- Perfluoroheptanesulfonic acid (PFHpS)
- Perfluoroheptanoic acid (PFHpA)
- Perfluorohexanesulfonic acid (PFHxS)
- Perfluorononanoic acid (PFNA)
- Perfluoropentanesulfonic acid (PFPeS)
- Perfluorotetradecanoic acid (PFTA)
- Perfluorotridecanoic acid (PFTrDA)
- Perfluoroundecanoic acid (PFUnA)
Cities ranked by the records
Ranked by the Purity Score of each city's main water system, highest first. Scores belong to water systems; there is no county score. The score is computed only from contaminants measured in the published EPA record, so this ranks the record, not which city's water is safest. How the score works.
0of 2 cities above the 15 µg/L action level
Based on each system's 90th-percentile result. Lead from household plumbing isn't in this record.
Lead in North CarolinaLargest water systems
- ClaytonCLAYTON, TOWN OF · NC035102030,876 served
- SmithfieldSMITHFIELD, TOWN OF · NC035101012,900 served
Frequently asked
How does Johnston County tap water compare across cities?
PurityMap ranks 2 cities in Johnston County by the Purity Score of each city's main water system, computed only from contaminants measured in the published EPA record. Scores belong to water systems, not to cities. The highest published score is Clayton's main water system: CLAYTON, TOWN OF · PWSID NC0351020 · Purity Score 57 (Fair) · Confidence: moderate · Assessed at the water-system level. The ranking compares the records, not which city's water is safest, and your own tap can differ with household plumbing.
How many Johnston County cities had a PFAS sample above a 2024 EPA limit?
2 of 2 Johnston County city reports had a PFAS sample above a 2024 EPA limit in EPA's UCMR 5 testing, including Clayton (PFOA 8.2 ng/L), Smithfield (PFOS 7.7 ng/L). That limit is judged on a yearly average, and water systems have until 2029 to meet it, so a single sample is not a violation. PFAS were detected at any level in 2.
Is there lead in Johnston County tap water?
Utilities report lead as a 90th-percentile result from home taps. 0 of 2 Johnston County cities reported a value above zero, and none was above the 15 µg/L federal action level. Lead usually comes from a building's own pipes and fixtures, so only a test at your tap tells you what you drink.
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