PFAS
What are PFAS?
Per- and polyfluoroalkyl substances (PFAS) are a class of over 12,000 fluorinated compounds used in consumer and industrial products for their non-stick properties. PFAS have been used to manufacture products such as non-stick cookware, food packaging, carpets and rugs, and specialized firefighting foams used to extinguish fuel fires. Releases of firefighting foam, particularly Class B aqueous film-forming foam (AFFF), are a known source of PFAS contamination in U.S. freshwater sources.
PFAS are considered emerging contaminants of environmental and human health concern due to their long half-lives, prevalence, and health risks. Each chemical in the PFAS class contains carbon-fluorine bonds that do not readily break down under environmental conditions, resulting in long residence times in the environment and in blood. PFAS are also highly prevalent. Biomonitoring results indicate that 98% of the U.S. general population has PFAS in their blood, although PFAS concentrations have decreased over time due to the industry’s phase-out of these substances. The most well-studied PFAS, perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), have been positively associated with an increased risk of chronic diseases. Higher serum levels of PFOA and PFOS have been linked to developmental delays, dampened immune responses, preeclampsia, ulcerative colitis, higher cholesterol levels, and certain cancers.
Scientific and regulatory attention has previously focused on a subgroup of PFAS known as perfluoroalkyl acids (PFAAs). PFAAs are perfluoroalkyl substances that have been subject to regulatory scrutiny. Chemicals in the PFAA subgroup are sometimes categorized as short- or long-chain chemicals, as carbon chain length influences their fate and transport characteristics to some extent. PFAAs can be further divided based on whether the chemical has a carboxylic acid or a sulfonic acid functional group. Perfluoroalkyl carboxylic acids (PFCAs) have a carboxylic acid functional group and include PFOA, perfluoroheptanoic acid (PFHpA), and perfluorononanoic acid (PFNA). Perfluorosulfonic acids (PFSAs) have a sulfonic acid functional group and include PFOS, perfluorohexanesulfonic acid (PFHxS), and perfluorobutanesulfonic acid (PFBS). Other subgroups aside from PFAAs include perfluoroalkane sulfonamides (PFSAAs), which often serve as raw materials for surfactant and surface treatment products; fluorotelomers, which are polyfluoroalkyl substances that degrade into PFCAs such as PFOA and PFNA; and next-generation PFAS, sometimes referred to as fluoroalkyl ethers. These include chemicals such as hexafluoropropylene oxide dimer acid (HFPO-DA or GenX), which has been used to replace PFOA in some applications.
PFAS Regulations - Drinking Water
The Third Unregulated Contaminant Monitoring Rule (UCMR3) marked the first instance of PFAS testing mandated by the U.S. Environmental Protection Agency (EPA). Over 4,000 U.S. public water systems serving ≥10,000 individuals, as well as a representative sample of 800 public water systems serving <10,000, monitored their drinking water supplies for six PFAS compounds: PFOA, PFHpA, PFNA, PFOS, PFBS, and PFHxS.
The EPA proposed multiple drinking water guideline values for PFAS over time. Following UCMR3 in 2016, the EPA issued non-enforceable lifetime health advisory levels (LHALs) for PFOA and PFOS set at 70 ng/L (either individually or combined). Some U.S. states and territories, including Guam and the Northern Mariana Islands (CNMI), adopted enforceable drinking water standards.
By late 2021, the EPA announced the Fifth Unregulated Contaminant Monitoring Rule (UCMR5) to examine 29 PFAS in drinking water resources starting in 2023. Under UCMR5, the EPA set the Minimum Reporting Levels (MRLs) for covered PFAS between 2 and 20 ng/L, which are about five times lower than the MRLs under UCMR3 (10–90 ng/L). Due to increasing PFAS concerns, lower Maximum Contaminant Levels (MCLs) are crucial for addressing the impact of these contaminants on the environment and human health.
In April 2024, the EPA finalized federal PFAS drinking water standards for six PFAS compounds: PFOA, PFOS, PFHxS, PFNA, PFBS, and GenX chemicals. There are three main components to the new federal drinking water standards for PFAS: (1) PFOA and PFOS each have an enforceable limit of 4 ng/L; (2) PFHxS, PFNA, and GenX each have an enforceable limit of 10 ng/L; and (3) PFHxS, PFNA, GenX, and PFBS have an enforceable limit of 1.0 as a hazard index. The hazard index is the sum of hazard quotients, where hazard quotients are obtained by dividing each chemical’s concentration in water by its corresponding risk level (10 ng/L for PFHxS, 10 ng/L for PFNA, 10 ng/L for GenX chemicals, and 2,000 ng/L for PFBS).
Guam PFAS
Monitoring Status
PFAS monitoring of Guam’s drinking water production wells began in March 2015 through UCMR3. Overall, six out of 109 wells examined showed detection levels above the MRL (10–90 ng/L) for at least one of the six PFAS listed under UCMR3. PFOS was the most frequently detected PFAS, found in five of the six contaminated wells. These preliminary data indicate that approximately 5% of Guam’s drinking water wells are contaminated. Moreover, PFOS exceedances of the 70 ng/L LHAL were noted in 2.4% of Guam’s wells.
The six PFAS-contaminated wells in Guam are scattered across three regions: a) Tiyan; b) Chalan-Pago Ordot; and c) Hagåtña. Wells NAS-1, A-23, and A-25 are contaminated with PFOS over 70 ng/L. A-23 and A-25 are currently offline. NAS-1 is located in the former Naval Air Station, where AFFFs (a major source of PFAS) were potentially used. PFOS and PFHxS were also detected in wells A-4 and A-13.
After 2020, Guam’s military production wells were also reported to be contaminated with PFAS. For example, one production well at the Naval Hospital was closed in August 2020 due to exceeding LAHLs. Currently, UCMR3 is ongoing (2023-2025), and during a legislative oversight hearing on the Northern Guam Lens Aquifer (January 2024), GWA mentioned that 34 production wells may require PFAS treatment under the new EPA guidelines.
Figure. Concentrations of three major PFAS compounds detected from five GWA production wells between 2013 and 2015.
Guam's PFAS Study
In 2019, Dr. Rainer Lohmann, a Professor of Oceanography at the University of Rhode Island (URI), and Dr. Barry Kim received a PFAS research grant through the Sources, Transport, Exposure & Effects of PFAS (STEEP) project, funded by the National Institutes of Health (NIH). In Guam, GWA well A-25, located in Hagåtña, was the most contaminated with PFOS, but the main PFAS contamination sources were unknown. Dr. Kim’s research team surveyed the area adjacent to well A-25 and identified five potential PFAS contamination sites: 1) near Well A-25, 2) Chaot River, 3) Hagåtña Swamp, 4) Hagåtña Heights Ponding Basins, and 5) Fonte River. In this region, a total of 22 sampling spots were selected, and 34 PFAS compounds were analyzed from soil and sediment samples.
PFAS analysis in soil and sediment samples showed that 1H,1H,2H,2H-perfluorooctane sulfonic acid (6:2 FTS) was detected at nearly all sampling points, with the highest concentration (3.7 µg/kg-dry soil, on average). Hexafluoropropylene oxide dimer acid (HFPO-DA, GenX), perfluorooctanoic acid (PFOA), perfluorobutanoic acid (PFBA), and PFHxS were also detected at most sampling points. PFOS was also detected, but it impacted only nine sampling points, indicating a localized distribution in the region.
Spatial distribution analysis revealed that Chaot River, near a GWA wastewater pump station, was the most contaminated PFAS site. There had been a history of wastewater leaks, suggesting that wastewater exposure may influence PFAS contamination at this site. One ponding basin in Hagåtña Heights, located about 1,000 feet from Well A-25, showed the highest concentration of PFOS (4.8 µg/kg-dry soil). In this region, groundwater generally flows toward the southwest, or toward Well A-25, so the high PFOS level in the ponding basin could likely impact Well A-25. Two stormwater drains near Well A-25 and Hagåtña Shopping Center also showed relatively high PFAS levels. Human activities may also contribute to elevated levels of PFAS. A relatively high amount of PFAS was also detected at the Hagåtña Springs. The Fonte River site showed relatively lower PFAS levels. Water analysis results detected concentrations of PFOS, PFHxS, fluorohexanesulphone amide (FHxSA), 1H,1H,2H,2H-perfluorohexane sulfonic acid (4:2 FTS), perfluorobutanesulfonic acid (PFBS), and perfluorobutanoic acid (PFBA). In addition to PFHxS and PFOS, shorter carbon chain PFAS (4- or 6-carbon) were detected in Well A-25, possibly due to the breakdown of highly soluble PFAS pollutants. Thus, in Hagåtña, PFAS degradation may occur, contributing to the presence of lower molecular weight PFAS in the water.
Overall, surface soil, sediment, and water sampling are key first steps in understanding the spatial distribution of PFAS. Among the five potentially contaminated sites in Guam, four have been linked to exposure from human activities (e.g., dumping) and products (e.g., consumer and industrial goods). Given Guam’s heavy reliance on imported goods and products from the mainland, it is crucial to understand the impact, influence, and persistence of PFAS chemicals on the island’s environment and its inhabitants. Significant research support is also needed to determine whether PFAS degradation is occurring at each of the potentially contaminated locations in Guam. This information can help researchers ascertain whether PFAS detections are from past or current sources.
Saipan PFAS
Monitoring Status
In Saipan, finished water samples from 23 entry points were collected in compliance with UCMR3. Five out of six PFAS chemicals were detected in Saipan’s municipal supply, and five of the 23 entry points had concentrations above reporting limits. Finished water from these five entry points was distributed to approximately 16 villages: Chalan Laulau, Iliyang, Chalan Kiya, As Terlaje, Kannat Tabla, Fina Sisu, San Jose, Garapan, Gualo Rai, Susupe, As Lito, San Antonio, Chalan Kanoa, Oleai, Koblerville, and As Perdido. The national maximum concentrations of PFOS (7,000 ng/L), PFHxS (1,600 ng/L), and PFHpA (410 ng/L) were found in Saipan, specifically in samples collected at IF-208, located 120 feet northeast of a known firefighting training area.
Saipan's PFAS Research
Monitoring Status
In collaboration with the Commonwealth Utilities Corporation (CUC), Dr. Barry Kim conducted PFAS research targeting six entry points and 46 production wells in Southern Saipan. From 2015 to 2020, a total of 94 samples were collected at entry points. Eighty-one of the 94 samples collected for PFAS monitoring in finished water contained PFAS. Seven specific chemicals were detected: PFOS, PFOA, PFHxS, PFBS, PFHpA, PFNA, and PFHxA. Concentrations at the entry points ranged from non-detect to 7,000 ng/L. On average, PFOS and PFHxS dominated the total mass of PFAS in these samples, representing 59% and 26% of the total PFAS concentration, respectively. Analysis of the entry point data indicated that PFHxA was rarely tested for at entry points, yet it was detected in all samples collected (n = 17). Additionally, PFNA, a chemical regulated under CNMI drinking water standards, was not detected at entry points other than IF-208.
At the Isley Field wellfield, 128 groundwater samples were collected from 21 supply wells, including IF-28 and IF-208. All wells tested for PFAS had at least one PFAS-positive sample. The Isley wells are clustered above the firefighting training area. There was considerable variability in concentrations among Isley wells, with average PFOS concentrations ranging over two orders of magnitude (5 to 4,375 ng/L). Distance from the firefighting training area was suspected to be the primary factor in the observed distributions and was further explored. Another potential factor affecting PFAS levels in each well was changes in pumping in 2015–2016 when wells were turned offline, which could have altered hyperlocal groundwater flow.
At the Obyan wellfield, 48 groundwater samples were collected from 19 supply wells. The Obyan wells are located downgradient of Isley Field. Obyan wells were less frequently monitored than Isley Field wells, partly because the Isley Reservoir (the primary entry point for Obyan wells) exceeded fewer advisories than the As Terlaje Tank (the primary entry point for Isley Field wells). Overall, 11 of the 19 monitored Obyan wells had at least one sample with detectable PFAS. Average PFOS levels in the Obyan wellfield ranged from non-detect to 677 ng/L. Higher PFAS concentrations were observed in wells located farther downgradient from the firefighting training area and the Isley wellfield cluster. Additionally, PFHxA, which was detected at Isley Field, was not monitored in Obyan during the study timeframe. Lastly, a time series analysis indicated an increase in PFAS levels over time.
At the Koblerville wellfield, three of the six supply wells were sampled more than once. Located west of the firefighting training area, the Koblerville wellfield was less frequently monitored than Isley Field and Obyan from 2015 to 2020. From the data provided, three wells contained PFAS, with KV-25 being the target well for monitoring (n = 5 samples, maximum total PFAS concentration = 101 ng/L). Since no groundwater flow pattern in southern Saipan travels west, it is suspected that the primary PFAS source in Koblerville is distinct from those in Isley and Obyan. Factors influencing the observed concentrations in Koblerville include changes in reporting/detection limits and source-specific characteristics. Further investigation is needed to evaluate PFAS levels in the Koblerville wellfield.
PFOS distribution pattern in the Saipan International Airport area
We analyzed groundwater levels from monitoring wells in combination with the PFAS data review. The spatial analysis focused on PFOS due to its dominance in 2015–2020 water samples, particularly within the Isley wellfield. Average PFOS concentrations were higher among supply wells in proximity to the firefighting training area. These data were used to define buffer zones around the primary hotspot of AFFF activity.
- Zone I (within a 780 ft radius of the firefighting training area) included seven Isley wells (IF-208, IF-25, IF-24, IF-108, IF-23, IF-22, and IF-101) with an average PFOS concentration over 400 ng/L and a maximum ΣPFAS concentration over 1,000 ng/L.
- Zone II (within 780–1,370 ft) contained four wells: IF-11, IF-12, IF-102, and IF-106. In general, wells in Zone II had average PFOS concentrations between 40–400 ng/L and maximum ΣPFAS concentrations between 80–1,000 ng/L. IF-106, located 300 ft north of IF-11, fell within this zone yet had an average PFOS concentration of 30 ng/L and a maximum ΣPFAS of 173 ng/L.
- Zone III (within 1,370–3,120 ft) included nine wells. Generally, wells in Zone III had average PFOS concentrations between 4–40 ng/L and maximum ΣPFAS concentrations between 10–80 ng/L. One well in Zone III (IF-21) had an average PFOS concentration of 27 ng/L and a maximum ΣPFAS concentration of 122 ng/L.
The exceptions in Zones II and III (IF-106 and IF-21) may reflect the influence of more localized processes affecting PFAS movement in groundwater.
What are PFAS?
Perfluoroalkyl substances (PFAS), also referred as perfluorinated compounds (PFC), have recently received attention as emerging contaminants in drinking water resources. PFAS are a family of complex manmade chemicals synthesized during the 1940s comprised of a fluorocarbon alkyl chain and a carboxylic or sulfonic acid group. They are resistant to heat, grease, and water degradation, which is why they can be found in numerous consumer and industrial products. A health advisory (HA) released in 2016 showed a constituent, perfluorooctanoic acid (PFOA), was detected in 99% of human serums in the U.S. between 1999 to 2012 as a persistent and bioaccumulating environmental compound.
PFAS Monitoring Between 2013-2015
PFAS monitoring between 2013 and 2015 examined six PFAS constituents in 4,900 Public Water Systems (PWS). PWS and the findings were published in the third Unregulated Contaminant Monitoring Rule (UCMR3). Perfluorooctane sulfonate (PFOS) and PFOA were most commonly encountered in all the sampled PWS. These compounds are no longer produced in the U.S., but traces of them can still be found in products coming from other places. The collective drinking water HA was recently revised by USEPA for both compounds, down from 200 ng/L to 70 ng/L. USEPA also requested appropriate remedial actions to be implemented by all public water agencies affected by the new ruling.
Contaminated Wells of Guam
The six contaminated wells of Guam are scattered across three regions: a) Tiyan, b) Chalan-Pago Ordot, and c) Hagåtña. Wells NAS-1, A-23 and A-25 are contaminated with PFOS over 70 ng/L. NAS-1, located in the former Naval Air Station Agana, was occupied by the U.S. Air Force from 1944 to 1995. About a year later of closing, volatile organic chemicals (VOC) were detected in NAS-1.
Dr. Denton, who is the retired WERI professor, analyzed a concentration pattern of PFOS from well A-25, the most contaminated well on Guam. PFOS data collected from June 2017 to January 2018, including three data sets from 2015 to 2016 obtained by GWA, were analyzed with cumulative precipitations recorded 30, 60, 90 and 120 days immediately prior to each sampling event. Second order polynomial regression analysis with a 90-day cumulative rainfall provided the best fit line to all PFOS-rainfall data plots. From these initial findings, variations in the duration and intensity of rain events over the preceding month seemed to have the greatest influence on this estimate, indicating that sources of PFASs may exist within some distance from well A-25.
PFAS contamination sites near well A-25 have not been identified. Thus, now WERI team is collecting soil and water samples from potential PFAS impacted sites. In collaboration with University of Rhode Island (Dr. Rainer Lohmann and Dr. Becanova), Dr. Barry Kim and Ms. Mallary Duenas are investigating the potential contamination sites.
