Government Sampling Overview for Bexar County's Public Water System

The San Antonio Water System (TX0150018), serving over 2.6 million people through more than 880,000 connections in Bexar County, uses surface water sources and has no EPA health-based violations on record. The latest unregulated contaminant monitoring rule (UCMR5) data from 2023 to 2026 list measurements for various PFAS compounds but show no exceedances of federal maximum contaminant levels (MCLs) established for 2024.

1. Firefighting Foam, Textile Finishing, and Landfill Sources: What Fits Bexar County’s PFAS Record

• No detections of PFOA or PFOS above reporting levels

Neither perfluorooctanoic acid (PFOA) nor perfluorooctane sulfonate (PFOS), common PFAS linked to firefighting foams, were detected above the lowest reporting thresholds in the municipal system's water records.

• Surface water source implies upstream industrial impacts possible but undetected

Because the water originates as surface water, potential inputs from textile finishing or landfill leachates upstream are monitored, but the system’s latest PFAS results reflect no detections of several key compounds above reporting levels.

• Minimal detections of some shorter-chain PFAS compounds

• PFBS detected twice but only slightly above reporting level at max 0.0038 µg/L
• PFBA detected three times, highest at 0.0092 µg/L, all well below federal MCL
• PFPeA detected once slightly above reporting level at 0.0032 µg/L

These low-level detections reflect monitoring sensitivity, not a regulatory concern.

2. Understanding the Hazard Index for Mixtures of Newer PFAS Compounds

• Hazard index estimates are not part of the EPA’s monitoring results but relevant to advanced risk assessment

While the EPA’s UCMR5 data do not include hazard index values, some research applies hazard indices to mixtures of 'forever chemicals' to understand cumulative exposure. Households may consider this when evaluating treatment needs, but the system’s data do not identify a need for health-based intervention.

• Detection below federal limits suggests an overall low measured presence of PFAS mixtures

Since no detection exceeds a federal MCL, the collective PFAS burden measured is below thresholds set for public health guidance.

3. Additional Questions from Commercial or Industrial Water Users Versus Residential Households

• Commercial operations may require testing for PFAS beyond the listed compounds

Businesses often inquire about specific PFAS congeners related to their processes or wastewater discharge permits, which differ from the compounds tracked in UCMR5 for residential water systems.

• Residential households primarily focus on common PFAS like PFOA, PFOS, and related short-chain substances

Households generally need to be aware of the broader category of per- and polyfluoroalkyl substances, while detailed compound-specific monitoring is more typical for industrial water users.

4. Differences Between UCMR5 and UCMR3 in PFAS Surveillance

• UCMR5 monitors a broader set of PFAS compounds with lower reporting levels

Compared to the earlier UCMR3 rule, the current survey adds newly identified PFAS substances and tightens detection limits, improving sensitivity.

• Bexar County water system’s nondetection of key historical PFAS like PFOA and PFOS contrasts with some older data sets

This suggests progress or differences in water source treatment, but the system’s records focus on current federally required analysis frameworks.

5. Considerations for Large Households, Second Homes, or Seasonal Properties

• Larger water usage may increase total exposure if PFAS present but does not change concentration readings

While concentration values remain the same, total daily intake could be higher for large or multi-occupant households, informing treatment capacity needs.

• Second or seasonal homes in Bexar County rely on the same system records but should verify their own water quality

Monitoring does not provide individual home data; a private test is necessary to confirm local water characteristics for any home.

The data discussed here summarize federal EPA UCMR5 monitoring of the San Antonio Water System supplying Bexar County, reflecting surface water sources serving a large population with no health-based PFAS violations recorded to date. For more details and updates, consult the EPA’s public water system records.

Where this information comes from

Source: EPA SDWIS public water system record. Sampled 2026-06-16. These figures describe the public water system's record, not the plumbing inside any individual building.

On record: EPA UCMR5 monitoring (2023-2025) for SAN ANTONIO WATER SYSTEM (TX0150018), TX: 910 results across 10 listed contaminants, 6 detections above the reporting level; compared with the applicable federal MCL, none above