<p data-bluf="true"> The Inland Empire draws its tap water from a mix of local groundwater and imported surface water treated by Metropolitan Water District. Per- and polyfluoroalkyl substances (PFAS) have been detected in portions of California's drinking water supply, affecting millions of residents statewide. In April 2024, the EPA finalized Maximum Contaminant Levels for six PFAS compounds, the first legally enforceable federal drinking water limits for these chemicals. California's own scientists, however, set a Public Health Goal for PFOA at 0.007 parts per trillion, compared to the federal enforceable limit of 4.0 parts per trillion. That gap of 571 times is the central data point in the Inland Empire PFAS story: a utility can be in full regulatory compliance while delivering water that California scientists consider potentially unsafe at those concentrations. Under a 2022 State Water Resources Control Board order, 1,296 California water sources belonging to 384 public water systems were required to test for 25 PFAS compounds. This article synthesizes that public record for IE homeowners. </p>
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The California State Water Resources Control Board identifies four major pathways through which PFAS enters drinking water supplies: fire training and response sites, industrial facilities, landfills, and wastewater treatment plants and biosolids land application. The Inland Empire has all four.
The region has a significant history of aerospace and defense manufacturing, active and former military installations, and industrial operations where products containing PFAS were used. Aqueous film-forming foam (AFFF), which contains high concentrations of PFAS, was standard equipment for aircraft firefighting and firefighting training exercises at military installations across Southern California. March Air Reserve Base, located in Riverside County adjacent to Moreno Valley, is a federal facility with documented contamination history from its operational use of AFFF over several decades. Norton Air Force Base, now San Bernardino International Airport, operated in San Bernardino County from 1942 through 1994 with similar contamination legacy.
PFAS compounds do not break down under normal environmental conditions. Once they reach groundwater, they migrate slowly through the aquifer, following the direction of groundwater flow. The Inland Empire's alluvial groundwater basins, including the San Bernardino Valley basin and the Chino Basin, are directly connected to the region's drinking water supply for millions of residents. The San Bernardino Valley basin provides supply to San Bernardino Municipal Water Department, the City of Redlands, and other utilities. The Chino Basin serves portions of Rancho Cucamonga, Ontario, Chino, and Fontana.
For context on other groundwater quality issues in the region, see our analysis of iron and manganese in San Bernardino County water and chromium-6 and hardness in Rancho Cucamonga water.
Imported water from Metropolitan Water District, blended with local groundwater at spreading grounds and in distribution systems, brings a different PFAS profile than local groundwater. The proportion of imported versus local supply in any utility's blend varies by season and drought conditions and is reported in each utility's annual Consumer Confidence Report.
The most significant number in the Inland Empire PFAS story is not a detection level at a specific utility. It is the regulatory gap between what California scientists concluded and what federal law currently enforces.
California's Public Health Goals
California's Office of Environmental Health and Hazard Assessment (OEHHA) adopted Public Health Goals for PFOA and PFOS on April 5, 2024. PHGs are science-based concentrations at which state toxicologists determined there is no significant health risk from lifetime exposure. They are not enforceable standards. They represent the state's health-science answer to the question: at what level is this compound actually safe?
OEHHA set the PHG for PFOA at 0.007 parts per trillion. For PFOS, the PHG is 1 part per trillion.
The federal MCLs
The EPA finalized Maximum Contaminant Levels on April 10, 2024, the first legally enforceable federal limits for PFAS in drinking water. PFOA and PFOS are each limited to 4.0 parts per trillion. Four additional compounds have individual MCLs at 10 parts per trillion: PFHxS, PFNA, and HFPO-DA (commonly called GenX). A Hazard Index MCL of 1 applies to certain mixtures of PFHxS, PFNA, PFBS, and HFPO-DA.
The compliance-safety gap
| Compound | Federal MCL (legally enforceable) | California PHG (health-based goal) | PHG is more protective by |
|---|---|---|---|
| PFOA | 4.0 ppt | 0.007 ppt | 571 times |
| PFOS | 4.0 ppt | 1 ppt | 4 times |
| PFHxS | 10 ppt | Not yet established | Requested by DDW |
| PFNA | 10 ppt | Not yet established | Under evaluation |
| HFPO-DA (GenX) | 10 ppt | Not yet established | Under evaluation |
Sources: OEHHA Public Health Goals for PFOA and PFOS, April 5, 2024 (<a href="https://oehha.ca.gov/water/public-health-goal/public-health-goals-pfoa-and-pfos" rel="nofollow noopener" target="_blank">oehha.ca.gov</a>); U.S. EPA PFAS National Primary Drinking Water Regulation, April 10, 2024 (<a href="https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas" rel="nofollow noopener" target="_blank">epa.gov/sdwa</a>); California SWRCB PFAS monitoring page (<a href="https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/pfas.html" rel="nofollow noopener" target="_blank">waterboards.ca.gov</a>).
What this means practically: a water system that tests at exactly 4.0 ppt PFOA is in full federal compliance. California scientists determined the health-protective threshold for PFOA to be 571 times lower than that level. Regulatory compliance and health-science-based safety are not the same thing for PFAS.
Under Assembly Bill 756 (2019), the SWRCB was authorized to require PFAS monitoring at public water systems without waiting for a formal rulemaking. The Division of Drinking Water used that authority to issue a series of general monitoring orders.
On October 31, 2022, the SWRCB issued General Order DW-2022-0001-DDW. This order required 384 California public water systems, covering 1,296 individual water sources, to test for 25 PFAS compounds quarterly beginning in 2023. The systems selected were those whose water sources are at risk for PFAS contamination based on proximity to other sources with confirmed detections. (Source: California SWRCB, <a href="https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/pfas.html" rel="nofollow noopener" target="_blank">waterboards.ca.gov</a>.)
A 2024 draft monitoring order extends requirements further, requiring additional community water systems to conduct PFAS initial monitoring consistent with the federal UCMR5 program.
The Environmental Working Group's tap water database, which aggregates utility testing data for California, found that 177 water systems serving approximately 18.9 million California residents had detections of one or more PFAS at concentrations above EWG's health-protective benchmarks (EWG Tap Water Database, 2023 to 2025 data, <a href="https://www.ewg.org/tapwater/" rel="nofollow noopener" target="_blank">ewg.org/tapwater</a>). EWG applies its own health guidelines, which are more conservative than current federal MCLs.
Nationally, the federal UCMR5 monitoring program covering public water systems serving more than 10,000 people collected data from January 2023 through December 2025. The EPA publishes results at the UCMR occurrence data page (<a href="https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-monitoring-rule" rel="nofollow noopener" target="_blank">epa.gov/dwucmr</a>) and is expected to release the complete UCMR5 dataset as systems finalize reporting in 2026.
For the scale of what PFAS contamination looks like when it reaches a Southern California groundwater basin, see our Orange County PFAS data article, which documents how 106 wells serving north and central OC were taken offline due to PFAS detections.
On May 18, 2026, the EPA proposed to rescind the Maximum Contaminant Levels for four of the six PFAS it regulated in April 2024: HFPO-DA (GenX), PFHxS, PFNA, and the Hazard Index mixture standard. The EPA stated the reason as a procedural deficiency in the original rulemaking, not as a finding that these compounds are safe. The science on the health effects of these four compounds has not changed.
The MCLs for PFOA and PFOS are retained. Compliance deadlines for PFOA and PFOS have been extended to April 2031. If the proposed rescission is finalized, utilities will not face a federal compliance obligation for GenX, PFHxS, or PFNA detections above the now-proposed-to-be-rescinded thresholds.
For Inland Empire homeowners, this matters because several compounds proposed for rescission, including PFHxS and PFNA, have been detected in AFFF-impacted groundwater and have documented health effects at low concentrations. The proposed rollback reduces regulatory pressure on utilities to treat for those compounds, but it does not change the underlying exposure risk.
California's state-level standards provide additional benchmarks independent of federal MCL status. California's notification level for PFHxS (the concentration at which utilities must notify the public) is 3.0 parts per trillion. The response level, at which utilities should consider taking a source offline or treating it, is 10 parts per trillion. These California-specific thresholds remain in effect regardless of whether a federal MCL exists. (Source: California SWRCB, <a href="https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/pfas.html" rel="nofollow noopener" target="_blank">waterboards.ca.gov</a>.)
Our California PFAS overview covers how these state standards interact with the federal regulatory framework for homeowners across the state.
Several factors can produce PFAS exposure at the tap even when a utility is in full compliance with current rules.
The compliance timeline. Full compliance with the retained PFOA and PFOS MCLs is not required until April 2031. Until that deadline, utilities are required to monitor and notify customers but are not yet required to install treatment if they exceed the MCL. A system currently reporting PFOA at, say, 8 parts per trillion is in a monitoring period, not yet in a violation.
Compounds without an MCL. UCMR5 requires monitoring for 29 PFAS. Federal MCLs currently cover only two (PFOA and PFOS, if the proposed rescission is finalized for the others). If a utility detects other PFAS at any concentration, there is no federal compliance obligation for those compounds.
The PHG gap. As the table above shows, PFOA at 4 parts per trillion is full federal compliance and 571 times the California PHG. Regulatory compliance is a legal status, not a health-safety certification.
Seasonal supply variation. Inland Empire utilities blend local groundwater with MWD-imported surface water in ratios that shift by season and drought conditions. PFAS concentrations may differ between the two supply sources. Annual CCR averages reflect the annual blend, not peak local groundwater use during summer months when MWD curtailments sometimes increase local pumping.
These dynamics apply similarly to Riverside County water users and across the Inland Empire water supply.
Two technologies have certified, documented performance for PFAS removal in residential settings.
Reverse osmosis (NSF/ANSI 58 certified) is the most effective point-of-use option. A properly installed and maintained RO system removes 90 to 99 percent of PFOA, PFOS, and most other PFAS compounds from drinking water at the tap. The NSF/ANSI 58 certification specifically covers PFAS reduction performance. Look for this certification mark on the system, not a generic "reduces contaminants" claim. For details on when a reverse osmosis installation makes sense for a given household, see our guide to signs you need a reverse osmosis system.
Service is available in Rancho Cucamonga, Fontana, San Bernardino, and throughout San Bernardino County and the Inland Empire. Every installation starts with a free water test at your tap.
Granular activated carbon (NSF/ANSI 53 certified) reduces longer-chain PFAS but is less effective for shorter-chain variants like GenX and PFBS. A whole-house activated carbon system provides a first layer of PFAS reduction across all water uses, including showers and appliances. For a full review of whole-house filtration options, see our guide to whole-house water filtration systems.
Water softeners do not remove PFAS. Ion exchange softeners target hardness minerals (calcium and magnesium) through a process that does not affect PFAS molecules. If your concern is both hardness, which is significant across the IE (see our Inland Empire water hardness by city data), and PFAS exposure, separate systems are required. Our whole-house water filtration in San Bernardino page covers combination approaches.
Every California public water system must publish a Consumer Confidence Report (CCR) annually by July 1. Once UCMR5 results are required to be included, the CCR will list PFAS detections at or above minimum reporting levels. CCRs are available directly from your utility and are searchable through the California Drinking Water Watch database at <a href="https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/DWW.html" rel="nofollow noopener" target="_blank">waterboards.ca.gov/dww</a>.
The EPA's UCMR5 Data Finder tool at <a href="https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-monitoring-rule" rel="nofollow noopener" target="_blank">epa.gov/dwucmr</a> allows you to search by water system name and state to find PFAS monitoring results above the minimum reporting level. Entering your utility name and filtering to PFAS parameters returns any detections the system reported.
For Inland Empire homeowners, the practical action list is short:
We offer free water testing in Fontana, free water testing in San Bernardino, and throughout the Inland Empire. A free water test covers hardness, pH, chlorine, TDS, and other common parameters and gives you a baseline on your overall water quality before any treatment decision.
Schedule your free water test today. Call (949) 873-1129 or book online.
For the companion dataset on neighboring counties, see PFAS in Orange County drinking water and Riverside County water quality data.
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