A study of multi-generational PFOS exposure in zebrafish (Danio rerio) is currently underway to provide answers to questions outstanding from results generated in a previous study (Keiter et al., 2012; Aquat Toxicol 118-119: p116). Our study seeks to improve upon the Keiter et al. (2012) multi-generation zebrafish exposure experimental design via an expanded dosing regime, increased replication, analytical chemistry validation, and an expanded suite of endpoints. Briefly, sublethal PFOS exposure concentrations of 0, 0.1, 0.6, 3.2, 20, 100 µg/L were targeted in a flow-through fish exposure system consisting of 5 replicate exposure tanks per treatment and 30 fish per replicate. The 180-d parental generation (P1) fish exposure has been completed, and the first familial generation (F1) fish exposure is underway. Analytical chemistry results for the P1 exposure indicated that PFOS concentrations in exposure water remained stable over the exposure period and matched nominal concentrations within 12.5% on average where independent validation analysis matched within 25% for all concentrations except 0.1 µg/L, which matched within 50%. Average 180-d control-normalized P1 mortality was highest (17%) in the highest PFOS exposure concentration (100 µg/L), although it was not significantly different from controls (P = 0.068). Growth measured at days 30, 60, 90, and 180 days indicated a statistically significant difference in body weight (compared to controls) for the 100 µg/L exposure at day 60 (mean reduction of 21%, P = 0.004), similar to the findings of Keiter et al. (2012). Negative effects on growth were not detected for other exposures, in contrast to Keiter et al. (2012), who noted effects on growth at 0.6 µg/L. Examination of eight weekly breeding trials with P1 fish (conducted starting on day 131) did not identify statistically significant negative effects of PFOS exposure on egg production or viability. In January 2021, the first familial generation (F1) PFOS exposure was successfully launched and will proceed through another 180-d exposure where survival, growth and reproduction will be assessed. Finally, the second familial generation (F2) will be produced and exposed for two weeks to complete the full multi-generational exposure. The three-generation exposure is expected to be compete in August 2021, and final results will be reported in early 2022.

Ashley Kimble

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