Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic organofluorine compounds used in many commercial applications, household products, and industrial processes since the 1940s. PFAS are termed “forever chemicals” due to their high environmental persistence and the concern around their bioaccumulation, and toxicity continues to rise. Most notably known for non-stick cookware, PFAS are also found in water- and stain-repellent fabrics, food packaging, cosmetics, fire-fighting foams and numerous other consumer products. Several thousands unique known structures are identified as PFAS in the Toxic Substances Control Act Inventory (https://comptox.epa.gov/dashboard/chemical_lists/PFASSTRUCTV3) including legacy PFAS (e.g., perfluorooctanesulfonic acid (PFOS)) and alternative/replacement PFAS (e.g., 6:2-fluorotelomersulfonic acid (6:2 FTS)).
Recently, PFAS were added to SPoT analyte list to track spatial and temporal trends of these highly persistent and bioaccumulative contaminants and prioritize monitoring efforts. In 2023, a suite of 40 PFAS including perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkyl sulfonic acids (PFSAs) and replacement PFAS were measured at 40 sites with high urban land use. Data from 2021 and 2022 showed low detection frequency for most PFAS across sites due to analytical errors and variability and will be omitted from future trend analyses.
Sum PFAS and percent contributions to total PFAS burdens were calculated for individual compounds. Sum PFAS in 2023 ranged from 0-14 ng/g dry sediment weight as shown below. Samples with higher sums were often found to be dominated by PFOS. PFOS also had the highest detection frequency across sites (35 out of 40 sites). Long-chain carboxylic acid with 12 carbons perfluorododecanoic acid (PFDoDa) and alternative PFAS, 6:2 FTS had high percent contributions to total PFAS at some sites. These data provide valuable information on sediment contaminant profiles across California watersheds indicating presence of complex PFAS mixtures. Ongoing work will identify trends at regional and statewide levels and assist in prioritizing monitoring strategies.
Recently, PFAS were added to SPoT analyte list to track spatial and temporal trends of these highly persistent and bioaccumulative contaminants and prioritize monitoring efforts. In 2023, a suite of 40 PFAS including perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkyl sulfonic acids (PFSAs) and replacement PFAS were measured at 40 sites with high urban land use. Data from 2021 and 2022 showed low detection frequency for most PFAS across sites due to analytical errors and variability and will be omitted from future trend analyses.
Sum PFAS and percent contributions to total PFAS burdens were calculated for individual compounds. Sum PFAS in 2023 ranged from 0-14 ng/g dry sediment weight as shown below. Samples with higher sums were often found to be dominated by PFOS. PFOS also had the highest detection frequency across sites (35 out of 40 sites). Long-chain carboxylic acid with 12 carbons perfluorododecanoic acid (PFDoDa) and alternative PFAS, 6:2 FTS had high percent contributions to total PFAS at some sites. These data provide valuable information on sediment contaminant profiles across California watersheds indicating presence of complex PFAS mixtures. Ongoing work will identify trends at regional and statewide levels and assist in prioritizing monitoring strategies.
Percent contributions of different compounds to total PFAS at top three sites with highest sum PFAS.