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Per- and polyfluoroalkyl substances (PFAS) are chemicals resistant to degradation. While such a feature is desirable in consumer and industrial products, some PFAS, including perfluorooctanoic acid (PFOA), are toxic and bioaccumulate. Hexafluoropropylene oxide dimer acid (HFPO-DA), an emerging PFAS developed to replace PFOA, has not been extensively studied. To evaluate the potential toxicity of HFPO-DA with a cost- and time-efficient approach, we exposed C. elegans larvae for 48 h to 4 × 10 -9 -4 g/L HFPO-DA in liquid media and measured developmental, behavioral, locomotor, and transcriptional effects at various exposure levels. Worms exposed to 1.5-4 g/L HFPO-DA were developmentally delayed, and progeny production was significantly delayed (p < 0.05) in worms exposed to 2-4 g/L HFPO-DA. Statistically significant differential gene expression was identified in all fourteen HFPO-DA exposure groups ranging from 1.25 × 10 -5 to 4 g/L, except for 6.25 × 10 -5 g/L. Among 10298 analyzed genes, 2624 differentially expressed genes (DEGs) were identified in the developmentally delayed 4 g/L group only, and 78 genes were differentially expressed in at least one of the thirteen groups testing 1.25 × 10 -5 -2 g/L HFPO-DA exposures. Genes encoding for detoxification enzymes including cytochrome P450 and UDP glucuronosyltransferases were upregulated in 0.25-4 g/L acute exposure groups. DEGs were also identified in lower exposure level groups, though they did not share biological functions except for six ribosomal protein-coding genes. While our transcriptional data is inconclusive to infer mechanisms of toxicity, the significant gene expression differences at 1.25 × 10 -5 g/L, the lowest concentration tested for transcriptional changes, calls for further targeted analyses of low-dose HFPO-DA exposure effects., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

In this study, density plume visualizations and statistical comparisons were made of enterococci bacteria (the main marine recreational microbial water quality indicator) densities, both before and after the upgrade of the discharge from the South Bay Ocean Outfall (SBOO) to secondary treatment level, so that the effect of this upgrade on ocean microbial water quality could be assessed. During the dry weather (bathing) season, reduction in enterococci densities was rather limited with only 2 shore stations and one kelp station showing significant reductions, and none showing increased compliance frequency. During the wet weather season, although the signature of land-based sources of bacterial pollution were evident, a majority of both shore (7 of the 11 stations) and kelp (4 of the 7 stations) stations showed statistically significant (p ≤ 0.05) reductions enterococci densities pointing to the role of the upgrade to secondary treatment in improving microbial water quality., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)