Why PFOA and PFOS Are Measured in Nanograms per Litre and What Four Decimal Places Mean
Understanding PFAS concentrations in Florence's water requires grasping the extremely low levels at which these substances are detected. PFOA and PFOS, two common per- and polyfluoroalkyl substances, are measured in nanograms per litre (ng/L), which is equivalent to parts per trillion (ppt). One nanogram per litre represents one trillionth of a gram in one litre of water. The monitoring results for the Florence City public water system report values with precision extending to four decimal places, reflecting the advanced sensitivity of federal laboratory methods used in surveys like the Unregulated Contaminant Monitoring Rule (UCMR5). Such precision helps detect even trace amounts of 'forever chemicals' that persist in the environment over time.
Firefighting Foam, Textile Finishing and Landfill Sources: Which Fits This Region's Record
Sources of PFAS contamination vary widely, including firefighting foams, textile manufacturing, and landfill leachate. The Florence City public water system relies on surface water sources serving over 79,000 residents, where monitoring from 2024 to 2025 detected PFOA and PFOS in several samples. While exact origins for this region’s detections are not specified by monitoring data, common regional contributions include historic use of aqueous film-forming foams (AFFF) at airports or military installations, runoff from textile finishing facilities, and leaching from landfills. Identifying the precise source requires further environmental investigation beyond these public system test results.
Why Aesthetic Secondary Standards Differ from Health-Based Limits, Applied to This Constituent
It's important to distinguish between aesthetic secondary standards and federally established health-based maximum contaminant levels (MCLs). Aesthetic standards address factors like taste, odor, and staining, but do not indicate health risk. For many PFAS compounds, including PFOA and PFOS, federal MCLs have been set at 4.0 ng/L (4 parts per trillion) to guide safe drinking water practices. Florence's public system recorded up to 0.0067 micrograms per litre (equivalent to 6.7 ng/L) in some samples, which signals detection above those MCL guidelines in a federal survey, but such findings are not violations in this context. Homeowners concerned about taste or staining should note that PFAS aesthetic effects are generally not the issue; the focus remains on health-based thresholds.
How the UCMR5 Survey Differs from UCMR3 in Which Compounds It Looked For and at What Level
The UCMR5 survey, conducted from 2023 to 2025, expanded on previous federal monitoring efforts by targeting a broader range of fluorinated compounds with more sensitive detection limits. Compared to UCMR3, UCMR5 included newer PFAS chemicals such as HFPO-DA and PFBS, with lower reporting levels down to fractions of a nanogram per litre. Florence's system showed no exceedances for some newer PFAS like PFHxS and PFNA during this survey, highlighting changes in monitoring technology and focus over time. This evolving data landscape helps water experts update risk assessments and treatment responses accurately.
What Distinguishes This Problem from the Two Problems Most Often Confused With It
PFAS contamination is often confused with issues like general water hardness or industrial solvents, but it is distinct in chemistry and health impact. Unlike hardness minerals, which affect scale and soap efficiency, PFAS are synthetic fluorinated compounds resistant to breakdown. Unlike volatile organic compounds (VOCs) such as solvents, PFAS remain in water without easily evaporating or degrading. Furthermore, some water treatment equipment may fail to reduce PFAS effectively, which can explain why existing systems in Florence households might no longer meet expectations. Testing your specific water for PFAS presence through a certified lab is essential to confirm your home's condition and guide an effective response.
Conclusion and Record Scope
The public water system record for Florence City, serving 34,162 connections, documents federal surveys of PFAS with multiple detections for PFOA and PFOS at nanogram-per-litre levels. These measurements reflect system-wide sampling of surface water sources, not individual residences. For personalized water quality and treatment needs, homeowners should pursue certified laboratory testing. Government data and monitoring results can be explored further through the EPA's Safe Drinking Water Information System.
This page provides a technical briefing based on federal water quality records and does not substitute for a full water test or professional assessment.
For households seeking to address persistent PFAS water concerns after equipment failure, the C-Series PFAS Forever Chemicals Filter ships ready to configure as a documented technology designed to reduce these compounds from home water supplies.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2025-09-15. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR5 monitoring (2023-2025) for FLORENCE CITY OF (SC2110001) (SC2110001), SC: 280 results across 10 listed contaminants, 18 detections above the reporting level; 7 results above a 2024 federal MCL