Assessing interactive mixture toxicity of carbamate and organophosphorus insecticides in the yabby (Cherax destructor)

Comparative evaluation of SPE methods for biotoxicity assessment of water and wastewater: Linkage between chemical extracting efficiency and biotoxicity outcome

Biotoxicity assessment results of environmental waters largely depend on the sample extraction protocols that enrich pollutants to meet the effect-trigger thresholds of bioassays. However, more chemical mixture does not necessarily translate to higher combined biotoxicity. Thus, there is a need to establish the link between chemical extracting efficiency and biotoxicity outcome to standardize extraction methods for biotoxicity assessment of environmental waters. This study compares the performance of five different extraction phases in solid phase extraction (SPE), namely HLB, HLB+Coconut, C18 cartridge, C18 disk and Strata-X, and evaluated their chemical extracting efficiencies and biotoxicity outcomes. We quantitatively assessed cytotoxicity, acute toxicity, genotoxicity, estrogenic activity, and neurotoxicity of the extracts using in vitro bioassays and characterized the chemical extracting efficiencies of the SPE methods through chemical recoveries of 23 model compounds with different polarities and total organic carbon. Using Pareto ranking, we identified HLB+Coconut as the optimal SPE method, which exhibited the highest level of water sample biotoxicity and recovered the most chemicals in water samples. We found that the biotoxicity outcomes of the extracted water samples significantly and positively correlated with the chemical extracting efficiencies of the SPE methods. Moreover, we observed synchronous changing patterns in biotoxicity outcome and chemical extracting efficiencies in response to increasing sample volumes per cartridge (SVPC) during SPE. Our findings underscore that higher chemical extracting efficiency of SPE corresponds to higher biotoxicity outcome of environmental water samples, providing a scientific basis for standardization of SPE methods for adequate assessment of biotoxicities of environmental waters.

Assessment of the impacts of GABA and AChE targeting pesticides on freshwater invertebrate family richness in English Rivers

Globally, riverine system biodiversity is threatened by a range of stressors, spanning pollution, sedimentation, alterations to water flow, and climate change. Pesticides have been associated with population level impacts on freshwater invertebrates for acute high-level exposures, but far less is known about the chronic impact of episodic exposure to specific classes of pesticides or their mixtures. Here we employed the use of the UK Environment Agency's monitoring datasets over 40 years (covering years 1980 to 2019) to assess the impacts of AChE (acetylcholinesterase) and GABA (gamma-aminobutyric acid) receptor targeting pesticides on invertebrate family richness at English river sites. Concentrations of AChE and GABA pesticides toxic to freshwater invertebrates occurred (measured) across 18 of the 66 river sites assessed. For one of the three river sites (all found in the Midlands region of England) where data recorded over the past 40 years were sufficient for robust modelling studies, both AChE and GABA pesticides associated with invertebrate family richness. Here, where AChE total pesticide concentrations were classified as high, 46 of 64 invertebrate families were absent, and where GABA total pesticide concentration were classified as high, 16 of 64 invertebrate families were absent. Using a combination of field evidence and laboratory toxicity thresholds for population relevant endpoints we identify families of invertebrates most at risk in the selected English rivers to AChE and GABA pesticides. We, furthermore, provide strong evidence that the absence of the invertebrate family Polycentropodidae (caddisfly) from one field site is due to exposure effects to AChE pesticides.

Mixture Toxicity of Three Unconventional Gas Fracking Chemicals, Barium, O-Cresol, and Sodium Chloride, to the Freshwater Shrimp Paratya australiensis

The 96-h acute toxicity of barium (Ba²⁺ ), o-cresol, and sodium chloride (NaCl) to Paratya australiensis was assessed in single, binary, and ternary combinations in addition to three biochemical assays: glutathione S-transferase, acetylcholinesterase, and sodium-potassium adenosine triphosphatase. The 96-h lethal concentrations that expressed 50% mortality (LC50) in the single-toxicant exposures were Ba²⁺  = 23.4 mg/L, o-cresol = 12.2 mg/L, and NaCl = 4198 mg/L. Mortality from o-cresol exposure occurred between 11 and 22 mg/L, whereas Ba²⁺ was more gradual across 10-105 mg/L, and most of the NaCl mortality occurred between 2050 and 4100 mg/L. Toxic units were used to assess the binary and ternary interactions of the toxicants. A more than additive effect was observed for most combinations in the binary chemical exposures, with the ternary combinations yielding highly synergistic interactions. Greater synergism was observed with the 96-h LC50 of o-cresol in combination with the three concentrations of NaCl (1025, 2050, and 3075 mg/L) compared with Ba²⁺ , with toxic units of 0.38, 0.48, and 0.10 (o-cresol) and 0.71, 0.67, and 0.50 (Ba²⁺ ). No notable enzyme activity trends were observed in the enzyme biomarker responses from both individual and mixture exposures. Although acute single-species toxicity tests tend to underestimate the effects of Ba²⁺ , o-cresol, and NaCl on populations, communities, and ecosystems in seminatural (e.g., mesocosms) and natural systems, there are currently no published acute toxicity data available for P. australiensis and the three toxicants used in the present study. The present study shows that chemicals with different toxicity mechanisms can potentially lead to more synergistic responses. Environ Toxicol Chem 2023;42:481-494. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Synthetic organic chemicals (flame retardants and pesticides) with neurotoxic potential induced behavioral impairment on zebrafish (Danio rerio): a non-invasive approach for neurotoxicology

Behavior responses of organisms can be used as a non-invasive method for neurotoxicology studies since it directly links the nervous system's functioning and biochemical activities. Among different behavioral activities, aquatic organisms' swimming behavior (fitness) is the essential factor for health assessment; thus, it is practiced routinely in neurotoxicological studies. Zebrafish (Danio rerio) are excellent models for neurotoxicology studies. Based on the above information, we hypothesized that zebrafish's swimming behavior is a potential biomarker for neurotoxic effect assessment. We exposed zebrafish (length, 3-4 cm; weight, 0.2-0.3 g) to different synthetic organic chemicals (organophosphorus flame retardants (tri-cresyl phosphate and cresyl diphenyl phosphate) and neurotoxic pesticides (cypermethrin and methomyl) for 15 days. For each test chemical, we chose two different concentrations (Treatment-I 5 μL/L and Treatment-II 25 μL/L) to study their eco-toxicity. The swimming strength of zebrafish was quantified using an online monitoring system. The swimming strength of zebrafish decreased under different treatments (Treatment-I (5 μL/L) and -II (25 μL/L)) of target chemicals. The circadian rhythm of zebrafish was predominantly not affected in this study. Higher neurotoxic effect (behavioral impairment) was observed in Treatment-II when compare to Treatment-I of organophosphorus flame retardants and pesticides groups. Responses of zebrafish under organophosphorus flame retardant (tri-cresyl phosphate and cresyl diphenyl phosphate) treatments were identical with pesticide (cypermethrin and methomyl) treatments. Based on the results, we conclude that swimming behavior could be an ideal non-invasive biomarker to assess waterborne contaminants' neurotoxic effect.

Synergistic effect of fenpropathrin and paclobutrazol on early life stages of zebrafish (Danio rerio)

Aquatic organisms are usually exposed to various co-existing pollutants. However, toxic effects of pesticide mixtures on aquatic organisms and its potential underlying mechanism still remain unclear. The joint effects of fenpropathrin (FEN) and paclobutrazol (PAC) on zebrafish (Danio rerio) using diverse toxicological endpoints were investigated in the current work. Our data exhibited that the 96-h LC₅₀ values of FEN to zebrafish at multiple life phases ranged from 0.0029 (0.0013-0.0042) to 0.16 (0.082-0.23) mg a.i. L^-1, which were lower by comparison to PAC ranging from 13.16 (8.564-21.03) to 23.43 (17.94-29.91) mg a.i. L^-1. Combination of FEN and PAC displayed synergistic effect on embryonic zebrafish. Activities of T-SOD, Cu/Zn-SOD and CYP450 were remarkably changed in the majority of single and mixture treatments by comparison to the untreated group. The mRNA levels of 17 genes related to oxidative stress, cellular apoptosis, immune system and endocrine system were assessed, and the data suggested that embryonic zebrafish were affected by both single pesticides and their mixtures. Five genes (P53, tsh, ERα, crh and cxcl-clc) showed greater alterations when exposed to pesticide mixtures by comparison to their individual chemicals. Therefore, it is urgently necessary to conduct more studies on mixture toxicities of different pesticides to explore the chemical mixtures with synergistic interactions.