Figure 1 Provided by the Walnut Valley Water District
In May 2020, the San Francisco Bay Regional Water Quality Control Board (RWQCB) released interim Environmental Screening Levels (ESLs) for two per- and polyfluoroalkyl substances (PFAS): perfluorooctane sulfonate (PFOS) and perflourooctanoate (PFOA). The new ESLs will be incorporated into the State Water Boards ESL Workbook and User guide as part of the next major update. For more on PFAS see some of our previous blog posts:
Why is this important? Because PFAS, first introduced in the 1940s, had many industrial applications due to their chemical properties and can now be found nearly everywhere. Chains of carbon atoms are attached to fluorine atoms. The Carbon-Fluorine bond is one of the strongest due to the short distance between the atoms, which is what makes these chemicals so hard to break down. PFAS are used in waterproof clothing and shoes. They can be found in non-stick cookware and food wrappers. They coat solar panels and are used in foam fire-suppression systems. They were used in aerospace, automotive, and electronics industries. Production of PFOS and PFOA has declined since 2002. However, PFAS can still be detected in aquifers throughout California, food grown in PFAS contaminated soil, and even in the biological tissue of organisms in PFAS rich environments. Health effects related to prolonged exposure include kidney disease, birth defects, autoimmune disease, developmental disorders, and increased risk of cancer.
Listed below are the Interim PFAS ESLs.
Groundwater ESLs (µg/L): Direct Exposure Human Health Risk Levels
| Chemical | Tapwater: Cancer Risk | Tapwater: Noncancer Risk | Notification Level | Direct Exposure ESL | MCL Priority ESL |
| PFOS | 1.7E-03 | 3.6E-02 | 6.5E-03 | 1.7E-03 | 6.5E-03 |
| PFOA | 5.4E-04 | 9.0E-03 | 5.1E-03 | 5.4E-04 | 5.1E-04 |
Groundwater ESLs (µg/L): Aquatic Habitat Ecotoxicity Levels
| Chemical | Direct Exposure Ecotoxicity: Freshwater | Direct Exposure Ecotoxicity: Saltwater | Secondary Poisioning Ecotoxicity: Freshwater & Saltwater | Ecotoxicity ESL: Freshwater &Saltwater |
| PFOS | 5.6E-01 | 2.6E+00 | 7.5E-02 | 7.5E-02 |
| PFOA | 5.4E+02 | 5.4E+02 | 4.4E+00 | 4.4E+00 |
Groundwater ESLs (µg/L): Aquatic Habitat Seafood Ingestion Levels (µg/L)
| Chemical | Cancer Risk | Noncancer Hazard | Seafood Ingestion ESL: Freshwater & Saltwater |
| PFOS | 4.7E-06 | 3.8E-04 | 4.7E-06 |
| PFOA | 2.2E-05 | 1.4E-03 | 2.2E-05 |
Soil ESLs (mg/kg): Direct Exposure Human Health Risk Levels
| Chemical | Resident Cancer Risk ESLs | Resident Noncancer Hazard ESLs | Com/Ind Cancer Risk ESLs | Com/ind Noncancer Hazard ESLs | CW Cancer Risk ESLS | CW Noncancer Hazard ESLs |
| PFOS | 1.2E-02 | 1.1E-01 | 5.1E-02 | 1.5E+00 | 2.9E-01 | 3.4E-01 |
| PFOA | 3.8E-03 | 2.8E-02 | 1.6E-02 | 3.7E-01 | 9.3E-02 | 8.6E-02 |
Note: Com/Ind = Commercial Industrial Worker; CW = Construction Worker
Soil ESLs (mg/kg): Terrestrial Habitat Levels
| Chemical | Plant & Invert. NOAEL | Mammal & Bird NOAEL | Significantly Vegetated Area ESLs (NOAEL) | Plant & Invert. LOAEL | Mammal & Bird LOAEL | Minimally Vegetated Area ESLs (LOAEL) |
| PFOS | 7.7E+00 | 1.3E-02 | 1.3E-02 | 3.3E+01 | 5.0E-02 | 5.0E-02 |
| PFOA | 8.4E-02 | 5.7E-01 | 8.4E-02 | 8.4E-01 | 1.1E+00 | 8.4E-01 |
Note: Invert. = Invertebrate; NOAEL = No Observed Adverse Effect Levels; LOAEL = Lowest Observed Adverse Effect Levels
Soil ESLs (mg/kg): Leaching to Groundwater Levels
| Chemical | Leaching ESLs: Drinking Water | Leaching ESLs: Aquatic Habitat |
| PFOS | 4.0E-04 | 2.9E-07 |
| PFOA | 9.7E-05 | 4.2E-07 |
These ESLs are important because they are the first ESLs for PFAS. They will be used to inform policy decisions and site specific cleanup standards. Studies regarding the health and environmental effects of PFAS are ongoing, and the ESLs will be updated as new information is available. McAlister GeoScience regularly consults Water Quality Control Board ESLs for all Contaminants of Concern (COCs) during site investigations and we are always sure to use the latest information available.