What is the hazard index for PFAS mixtures in Shelby’s water system?
The hazard index is a calculated metric that helps describe combined potential effects of multiple PFAS compounds when present together, without defining any direct health risk. For Memphis Light, Gas, & Water’s system in Shelby County, the EPA’s UCMR5 survey detected none of the monitored PFAS compounds—such as PFOA, PFOS, PFHxS, PFNA, or HFPO-DA—above reporting levels. This means the compound mixture’s hazard index, based on these nondetections, remains at levels that the EPA does not consider an indicator of health-based concern in this system's groundwater supply.
Why are PFOA and PFOS measured in nanograms per litre and what does four decimal place precision indicate?
Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are quantified in nanograms per litre (ng/L), equivalent to parts per trillion (ppt), reflecting extremely low concentrations. The reporting precision to four decimal places (e.g., 0.004 µg/L) means that the detection method can reliably identify PFAS molecules at or above these tiny thresholds. The Memphis water system’s EPA monitoring from April to October 2024 recorded zero results above these detection limits, implying that any presence of these compounds in the water is below the current analytical capacity of the testing method.
Which household fixtures, appliances, or uses are impacted first by PFAS presence?
PFAS compounds, often called "forever chemicals," are not removed by standard filtration and can accumulate in certain household water-contact points. Kitchen appliances that filter or process drinking water—like water dispensers, ice makers, or refrigerators with water lines—may be affected first in a home with elevated PFAS levels. Similarly, fixtures delivering drinking or cooking water are primary points to consider for targeting PFAS reduction. Because the Memphis public water system’s records show no PFAS concentrations above detection thresholds, typical household equipment failure related to PFAS may prompt individual water testing and targeted solutions.
What do 'detected,' 'median,' and 'range' mean in the Shelby water sampling record?
"Detected" means the compound was measured at or above the method's reporting level in at least one sample. For Shelby’s system, none of the 20 samples for PFAS compounds showed detection above reporting levels during EPA’s recent monitoring. "Median" would represent the middle value if detections occurred, offering a measure of typical concentration, while "range" shows the span of detected concentrations from lowest to highest. Since all results are nondetects, these statistics do not apply here but remain useful concepts for future reference when evaluating water quality data.
What happens when PFAS are left unaddressed in household water over time?
Long-term presence of PFAS in drinking water can lead to their accumulation on activated carbon or ion-exchange media within household treatment systems, potentially reducing the system’s effectiveness over time. Without addressing this build-up, water filtration performance may degrade, leading to unnoticed passage of these substances through domestic water points. While Memphis’s water system does not currently report PFAS detections above limits requiring action, if household treatment equipment has failed, ensuring replacement with technology designed for PFAS management is critical to maintain water quality.
The Pentair PFAS Forever Chemicals Filter ships ready to configure for direct purchase and addresses removal of 'forever chemicals' such as PFOA and PFOS effectively when properly used. It is a documented option for households concerned about PFAS despite local nondetection.
Summary
The Shelby County public water system shows no detectable PFAS compounds above the EPA’s reporting levels, indicating no current measurable issue with these substances in Memphis groundwater supply. However, to verify individual household water quality and address equipment failures, specific testing is necessary, and targeted treatment solutions like the Pentair PFAS Forever Chemicals Filter provide a direct-ship option for ongoing management.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2024-10-02. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR5 monitoring (2023-2025) for MEMPHIS LIGHT, GAS, & WATER (TN0000450), TN: 200 results across 10 listed contaminants, 0 detections above the reporting level; nothing detected above the method reporting level
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