Feeding Ration Impacts Larval Pimephales Promelas 7-Day Subchronic Growth Endpoint: Case Study with Perfluorooctanesulfonic Acid.

The larval fathead minnow, Pimephales promelas, 7-day subchronic survival and growth standard toxicity test method is commonly used for research and regulatory testing of effluents and compounds, including emerging contaminants such as Perfluorooctanesulfonic Acid (PFOS). Existing feeding guidelines for testing are described in multiple methods but are open to interpretation. The current study sought to determine the impact of feeding ration on P. promelas survival and biomass during a subchronic exposure to PFOS. The study was conducted in two phases: (1) a control experiment to determine the most significant feeding ration factors that maximize biomass, with consideration to laboratory logistics, and (2) application of down-selected feeding rations in a PFOS exposure to determine toxicity reference values. The control optimization study supported that feeding ration and feeding frequency were significant factors in fish biomass. In the subsequent PFOS study, fish were fed a high or low ration of Artemia twice daily, while exposed to 0.3 to 3.4 mg/L PFOS. Fish fed a high ration of Artemia had significantly (p < 0.05) greater biomass than fish fed a low ration in all exposure concentrations except 3.4 mg/L, where survival was low in both treatments. The feeding ration was not a significant factor on the survival endpoint for either treatment, but the PFOS concentration was (p < 0.0001) (high ration LC50 = 2.44 mg/L; low ration LC50 = 2.25 mg/L). These findings contribute to a better understanding of the impact feeding ration has in toxicity assessments and downstream regulatory decisions.

Acute Toxicity of Eight Aqueous Film-Forming Foams to 14 Aquatic Species.

Researchers have developed numerous per- and polyfluoroalkyl substances (PFAS)-free aqueous film-forming foam (AFFF) formulations to replace PFAS-containing AFFF used for fire suppression. As part of the Department of Defense's Strategic Environmental Research and Development Program (SERDP), we examined the direct lethal effects of seven PFAS-free AFFF and a PFAS-containing AFFF on 14 aquatic species using a series of lethal concentration (LC50) tests. We assessed the LC10, LC50, and LC90 values using log-logistic and logit analyses. Across all aquatic species tested, we discovered that exposure to at least one PFAS-free AFFF was more or as toxic as exposure to the PFAS-containing AFFF. For most cases, National Foam Avio F3 Green KHC 3% and Buckeye Platinum Plus C6MILSPEC 3% were the most and least toxic formulations, respectively. Moreover, we found consistency among results from multiple experiments using the same minnow species (Pimephales promelas) and among closely related taxa (e.g., daphnids, amphibians). Lastly, the LC50 values for AFFF formulations trended lower for tested marine species as compared to those of freshwater species. These results dramatically increase the current knowledge on the potentially toxic effects of AFFF but also highlight the need for additional research and the development of new PFAS-free AFFF that are more "ecologically friendly" than those containing persistent PFAS.

Chronic Toxicity of Per- and Polyfluoroalkyl Substance-Free Firefighting Foams to Aquatic Organisms.

Amid global concern regarding the health and environmental impacts of per- and polyfluoroalkyl substances (PFAS), there is an urgent need to develop and implement alternative products without PFAS. Consequently, PFAS-free firefighting foams used for fire suppression have been developed for use in military and residential settings. To facilitate the selection of lower-risk PFAS-free foams, the present study focused on the chronic toxicity of seven PFAS-free and one PFAS-containing foam to six aquatic species. Target species included two cladocerans, Daphnia magna and Ceriodaphnia dubia; the chironomid Chironomus dilutus; the mysid Americamysis bahia; and two fish species, Pimephales promelas and Cyprinodon variegatus, with endpoints including growth, development, reproduction, and survival. To facilitate comparison and product toxicity rankings, effective concentrations (20%, 50%) and no- and lowest-observed-effect concentrations (NOECs and LOECs, respectively) were calculated. Effective concentrations, NOECs, and LOECs varied by over an order of magnitude among foams and species, with several of the PFAS-free formulations ranked as highly toxic based on US Environmental Protection Agency alternatives assessment hazard criteria. Overall, the PFAS-free foams were found to exhibit either similar or greater toxicity compared to the PFAS-containing reference foam across several species and endpoints. Nonmonotonic and hormetic dose responses were observed in D. magna for several of the tested foams, with increased reproduction and growth at intermediate exposures. Generally, tested foam toxicity rankings were consistent with a related acute toxicity study using the same species and formulations, and other research using soil invertebrates. Combined with related efforts for other taxa including mammals, birds, and plants, the present research will facilitate the selection of appropriate PFAS-free firefighting foams that minimize harm to the environment. Environ Toxicol Chem 2024;00:1-19. © 2024 SETAC.

Sensitivity of the Marine Calanoid Copepod Pseudodiaptomus pelagicus to Copper, Phenanthrene, and Ammonia.

There are limited acute toxicity test methods for native North American marine species that are considered zooplankton for their entire life cycle. Examples of standardized marine zooplankton methods include mussel, bivalve, and echinoderm development tests that use a relatively short-lived planktonic larval stage, chronic life-cycle toxicity tests using epibenthic copepods, and a 24-h Acartia tonsa copepod test method. The objectives of the present study were to: 1) develop and evaluate a novel, 48-h acute toxicity test method using the marine North American copepod Pseudodiaptomus pelagicus that is planktonic for its entire life cycle, and 2) determine the sensitivity of P. pelagicus relative to commonly tested marine toxicity test species. The average (±1 standard deviation) median lethal concentrations (LC50s) for copper (Cu), phenanthrene, and un-ionized ammonia were 32 ± 15 µg/L, 161 ± 51 µg/L, and 1.08 ± 0.30 mg NH3 /L, respectively. These results placed P. pelagicus on the more sensitive end of Cu and phenanthrene species sensitivity distributions. The copepod was less sensitive to un-ionized ammonia than commonly tested marine species. This finding suggests that the acute P. pelagicus test method will allow a focus on assessing the impacts of persistent contaminants of concern with less confounding impact from naturally occurring ammonia released to the water from sources such as suspended sediments. Environ Toxicol Chem 2019;38:1221-1230. Published 2019 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Estrogen protects cardiac myogenic (H9c2) rat cells against lethal heat shock-induced cell injury: modulation of estrogen receptor alpha, glucocorticoid receptors, heat shock protein 70, and iNOS.

In the present study we have established that exposure of rat cardiac myoblasts (H9c2 cells) to 46 degrees C for 1 hour (lethal heat shock) resulted in optimal cell injury as determined by lactate dehydrogenase release. Pretreatment of H9c2 cells for 24 hours with 17beta-estradiol significantly protects myoblasts against subsequent lethal heat shock exposure in a concentration-dependent manner with maximum protection obtained at 1 microM of 17beta-estradiol. With Western blotting, it was observed that 17beta-estradiol-protected cells had significantly higher levels of the estrogen receptor alpha and inducible heat shock protein 70 (hsp70) as well as inducible nitric oxide synthase (iNOS) levels compared with lethal heat shock-exposed cells. In contrast, lethal heat shock-exposed cells had significantly higher levels of total cellular glucocorticoid receptors (GR), both cytoplasmic and nuclear, compared with 17beta-estradiol-protected cells. Immunofluorescence technique using confocal microscopy revealed nuclear localization of the glucocorticoid receptors (GR) in lethal heat shock-exposed H9c2 cells while 17beta-estradiol-protected cells had primarily extranuclear localization of GR. We conclude that (1) 17beta-estradiol protects H9c2 cells against lethal heat shock insult by a receptor-independent mechanism, and (2) the protective effects are likely mediated by modulation of GR, hsp 70, and iNOS expression.