Frequently Asked Questions

PFAS are manmade compounds that have been used to make carpets, clothing, fabrics for furniture, paper packaging for food, electronics, personal hygiene products, and other materials (e.g., cookware) designed to be waterproof, stain-resistant, or non-stick. Of particular interest are six compounds Perfluorooctanoic Acid, more commonly referred to as PFOA, Perfluorooctane Sulfonic Acid (PFOS), Perfluorobutane Sulfonic Acid (PFBS), Perfluorohexanesulfonic Acid (PFHxS), Perfluorononanoic Acid (PFNA), and Hexafluoropropylene Oxide (HFPO) Dimer Acid (HFPO-DA) and its Ammonium Salt (together known as “GenX chemicals”).  While PFOA, PFOS, PFBS, and PFHxS have notification levels issued by the State of California, on April 10, the United States Environmental Protection Agency (USEPA) set drinking water standards (known as maximum contaminant levels) for PFOA, PFOS, PFHxS, PFNA and GenX chemicals in drinking water.

In recent years people have become more familiar with the term PFAS. Although awareness of these manmade chemical compounds is recent, PFAS have been in wide use since the 1940s.

Used in many consumer and industrial products for their ability to repel stains, water, and oil, PFAS are persistent in the environment and do not readily degrade.  They also are prevalent in many items we encounter daily – inside and outside the home. While items imported from outside the United States may contain PFAS, its use is being phased out in the US.  

• PFOA, PFOS, PFBS, and PFHxS are man-made compounds that have been used to make carpets, clothing, fabrics for furniture, paper packaging for food, electronics, personal hygiene products, and other materials (e.g., cookware) designed to be waterproof, stain-resistant, or non-stick.
• PFOA and PFOS were also used for firefighting at airfields and in several industrial processes.
• PFNA is similar, in function and use, to PFOA.    It is mainly used in the non-stick, stain repellent, and chemically inert coatings.
• PFBS has been identified in the environment and consumer products, including surface water, dust, carpeting and carpet cleaners, floor wax, and food packaging.
• HFPO dimer acid and its ammonium salt are also known as “GenX chemicals” because they are the two major chemicals associated with the GenX processing aid technology. GenX chemicals are used to make high-performance fluoropolymers (such as Teflon) without the use of perfluorooctanoic acid (PFOA).
• PFAS are persistent in the environment and do not breakdown easily.

According to the US EPA, there is evidence that exposure to PFAS can lead to adverse health outcomes in humans. If humans, or animals, ingest PFAS (by eating or drinking food or water than contain PFAS), the PFAS are absorbed, and can accumulate in the body. PFAS stay in the human body for long periods of time. As a result, as people get exposed to PFAS from different sources over time, the level of PFAS in their bodies may increase to the point where they suffer from adverse health effects.

Studies indicate that PFOA, PFOS, PFBS, and PFHxS can cause reproductive and developmental, liver and kidney, and immunological effects, and decreased thyroid hormone levels in laboratory animals.  The most consistent findings from human epidemiology studies are increased cholesterol levels among exposed populations, with more limited findings related to:

• infant birth weights,
• effects on the immune system,
• cancer (for PFOA), and
• thyroid hormone disruption (for PFOS and PFBS).
• effects on kidneys (PFBS and HFPO-DA)
• growth and development in fetuses, infants, and young children (PFHxS)
• increased total cholesterol and LDL cholesterol (PFNA)
• possible liver damage (HFPO-DA)

In August 2019, the California State Water Resources Control Board, Division of Drinking Water (DDW) set the customer Notification Level of 5.1 parts per trillion (ppt) for PFOA and 6.5 ppt for PFOS, and in February 2020, set new Response Levels of 10 ppt for PFOA and 40 ppt for PFOS. In March 2021, DDW issued the notification level and response level for PFBS of 500 ppt and 5000 ppt, respectively.  In October 2022, DDW issued the notification level and response level for PFHxS at 3 ppt and 20 ppt, respectively.

A notification level is a nonregulatory, precautionary health-based measure for concentrations of chemicals in drinking water that warrant notification and further monitoring and assessment.

A response level is a nonregulatory, precautionary health-based measure that is set higher than a notification level and represents a recommended level that water systems consider taking a water source out of service or provide treatment if available to them.

In March 2019, the DDW began a state-wide PFAS investigation and issued orders to approximately 200 water utilities throughout California to test groundwater wells that are in close proximity to fire training/fire response sites (e.g., airfields), industrial sites, landfills, and/or wastewater treatment plants for PFAS. Since ACWD groundwater sources are not located in close proximity to potential sources of contamination, ACWD was not issued orders to monitor for PFOA, PFOS, or PFBS by DDW.  

Furthermore, Assembly Bill 756 that took effect on January 1, 2020, authorized the State Board to more broadly order water systems to monitor for PFAS and report their detections. Again, ACWD was not issued an order under the Assembly Bill. However, ACWD began voluntary monitoring of PFAS in June of 2020, at which time low levels of PFAS were detected in local groundwater sources.

In October 2022, DDW issued monitoring orders to numerous water agencies, including ACWD, to monitor all groundwater sources effective January 1, 2023.  The provisions of the Order are similar to the voluntary monitoring program that ACWD began in June 2020.  ACWD will continue to monitor sources on a quarterly basis.

On April 10, 2024, EPA set new limits on select PFAS compounds in drinking water to better protect human health.  These limits are called Maximum Contaminant Levels (MCLs).  EPA is setting limits for five individual PFAS:  PFOA PFOS, PFNA, PFHxS, and HFPO-DA (GenX Chemicals), and  also setting a Hazard Index Level for when two or more of four PFAS compounds are present as a mixture:  PFNA, PFHxS, HFPO-DA, and PFBS.  The final MCLs established by the Federal EPA are listed below:

Public water systems must monitor for these PFAS and have until 2027to complete initial monitoring.  Additionally, water systems have until 2029to be compliant with these MCLs.

ACWD tested drinking water supplies for PFOA and PFOS compounds in 2014, as required by the USEPA under the third Unregulated Contaminant Monitoring Rule (UCMR). ACWD did not detect PFOA or PFOS in the drinking water in 2014, however the lowest analytical detection at the time was approximately ten times higher than today.

Since 2014, advances in testing technologies since have allowed us to detect substances at increasingly low levels. Therefore ACWD, in June 2020, voluntarily sampled several water supply sources ahead of any regulatory requirement.  This proactive monitoring allows ACWD to ensure the best water quality is available to our customers and take measures to treat our source supplies.

Since 2020, ACWD has continued to test its drinking water served to its customers, including UCMR monitoring in 2024,, and has adjusted and optimized operations such that PFAS levels in all treated water delivered to customers has remained below the notification levels or non-detectable.

Our voluntary testing identified low levels of PFOA in our groundwater sources between non-detect and 5.5 ppt, with some sources above the customer notification level of 5.1 ppt.  However, all treated water delivered to customers had no detections of PFOA.

PFOS was detected in most groundwater sources at low levels, between non-detect and 16 ppt, with some sources above the customer notification level of 6.5 ppt set by the DDW.  However, all treated water delivered to customers was below the notification level or non-detectable.

PFBS was detected in some groundwater sources at low levels, between non-detect and 9.4 ppt, with all sources below the customer notification level of 500 ppt.  All treated water delivered to customers had no detections of PFBS.

PFHxS was detected in most groundwater sources, between non-detect and 15 ppt, with most of the sources above the customer notification level of 3 ppt. Since the establishment of the notification level, ACWD has optimized operations to ensure all treated water delivered to customers remain below notification levels.

PFNA and HFPO-DA, were not detected in any ACWD water sources or any treated water delivered to customers.

Results from this same monitoring program did not detect PFOA, PFOS, PFBS, PFNA, PFHxS, or HFPO-DA in surface water supplies which account for almost two-thirds of ACWD’s total water delivered to our customers.

Samples were collected by trained sampling staff from locations where other regulatory water quality samples are collected and analyzed by a State Certified Laboratory.

As per DDW’s Monitoring Order issued in October 2022 which became effective January 1, 2023, ACWD will continue quarterly groundwater monitoring as it has been doing voluntarily since June 2020.

ACWD already has optimized operations at our treatment facilities to ensure that all water served to customers have remained below the State of California’s notification levels for PFAS, and  have further optimized our operations to account for the new MCL criteria.

ACWD has existing water treatment facilities in place to effectively safeguard your water supply with the use of reverse osmosis technology at our Newark Desalination Facility and the blending of groundwater and surface water at our Blending Facility. Both methods are already implemented at our treatment facilities and are operated to keep the detections below the notification levels, thereby ensuring the treated water supplied to our customers meets all health-based standards. 

While ACWD adjusted operations to ensure water delivered to our customers is below California’s Notification Levels and the USEPA’s newly established MCLs for PFAS, this has reduced production capacity at ACWD’s Blending Facility, which blends groundwater from the ACWD wellfields with imported surface water.

In anticipation of PFAS regulations, ACWD has designed and is currently building a treatment facility to address PFAS in groundwater at our Blending Facility.  Currently under construction, the facility will treat up to 6 million gallons per day (MGD) of PFAS-impacted groundwater and may be expanded to treat up to 15 MGD in the future, if needed.  In addition, the facility will restore reduced capacity that resulted from operational changes needed to minimize PFAS levels in the treated water delivered to customers.

ACWD routinely posts PFAS sampling results on its website and additionally provide the sample results to the State Water Resources Control Board Division of Drinking Water who will also post it on their website.

The latest data is available at acwd.org/PFAS

More information on PFAS compounds  is available at https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas or the California Water Board Frequently Asked Questions https://www.waterboards.ca.gov/pfas/docs/pfas_general_faq.pdf.