This project aims to conduct initial ecotoxicity assessments of new per- and polyfluoroalkyl substance (PFAS)-free surfactant formulations on terrestrial plants and soil invertebrates. Two of the short-chain aqueous film forming foam (AFFF) formulations will be included as comparisons. Specifically, this project aims to:

1. Study chronic phytotoxicity of the test formulations on one environmentally-relevant plant species, the field mustard (Brassica rapa);
2. Study chronic toxicity of the test formulations on two model soil invertebrates, the nematode Caenorhabditis elegans and the microarthropod Folsomia candida;
3. Compare the bioconcentration potential among the test formulations and identify the chemicals within each formulation with relatively high bioconcentration potential in biota samples (plant and invertebrate tissues) via nontarget analysis.

Six formulations will be chosen for evaluation, including four new PFAS-free foams that will be identified by SERDP as candidate AFFF-alternatives, and two of the short-chain AFFF foams that are currently in use by the Department of Defense. One environmentally-relevant plant species, the field mustard (Brassica rapa), and two invertebrate animal models representing lower trophic levels of soil food web, the soil nematode Caenorhabditis elegans and the soil microarthropod Folsomia candida, will be used as the test organisms. Study on chronic phytotoxicity will be conducted in a greenhouse using field soil sample. Toxicity tests with soil invertebrates will be performed using the same soil under laboratory conditions. Endpoints that will be measured include: 1) the growth of plants and production of seeds for chronic phytotoxicity; and 2) reproduction rate for chronic toxicity to invertebrates. Moreover, to investigate the bioconcentration potential of individual chemicals within the foams, the project team will develop a nontarget analysis method using ultrahigh-resolution mass spectrometry (Orbitrap liquid chromatography–mass spectrometry) to determine biota-to-soil accumulation factor of individual chemicals.

The ultimate benefits of this project will be the generation of 1) the knowledge of the potential environmental risk of new PFAS-free foam formulations on terrestrial plants and soil invertebrates; 2) a rank order of the relative ecotoxicity of test formulations; and 3) a list of high-priority chemicals within the test formulations that possess high bioconcentration potential in plants and soil invertebrates. These outcomes will assist in the final selection of new formulations and mitigate potential exposures and/or future environmental cleanup. (Project Completion - 2023)

Wu, X., H. Nguyen, K. Damian, and H. Peng. 2022. Chronic Toxicity of PFAS-free AFFF Alternatives in Terrestrial Plant Brassica rapa. Science of the Total Environment, 850:158100. doi.org/10.1016/j.scitotenv.2022.158100.

Xingli, Y., J.A. Ceja-Navarro, and X. Wu. 2022. Sublethal Toxicity of Fluorine-Free Firefighting Foams in Soil Invertebrate Caenorhabditis elegans. Environmental Science and Technology Letter, 9(6):561-566. doi.org/10.1021/acs.estlett.2c00219.