Toxicity assessment of pollutants sorbed on microplastics using various bioassays on two fish cell lines

Microplastics are tiny plastic fragments resulted from runoff and weathering breakdown of larger plastics debris. They represent an emerging concern for marine ecosystems. Microplastics impacts on aquatic life are little studied. These small particles could be ingested directly by organisms and cause chronic physical and toxicological effects. Moreover, microplastics are the support for a lot of chemicals present in aquatic environment, especially hydrophobic substances. The aims of this study is to investigate toxicity of environmental microplastics samples collected during the Race for Water Odyssey in fish cell lines. A difference of sensitivity was observed between fish cell lines. Preliminary results obtained here support that RTLW-1 could be an interesting tool to evaluate the potential chemical toxicity of microplastics and sorbed pollutants. Toxicity of extracts from MP collected worldwide suggests a biological impact?

In vitro acute toxicity assessment of tire tread particles using rainbow trout cell lines of gill and intestine

Florian Frédéric Vincent Breider, Benoît Jean Dominique Ferrari, Thibault Béranger Masset, Kristin Schirmer

Tire and road wear particles (TRWP) are generated by the abrasion of tires while driving, and recent questions were raised in regards to their potential contribution to microplastics released into the aquatic environment and their potential toxicological impacts. Our study aimed to determine the toxicity of TRWP and associated chemicals to fish using two rainbow trout (Oncorhynchus mykiss) cell lines representing the gill (RTgill-W1) and the intestinal (RTgut-GC) epithelium. Acute exposure to cryogenically milled tire tread (CMTT) particles and CMTT digestate following in vitro digestion was investigated. To obtain the effective concentrations (EC50) causing a 50% cell viability loss, tests were performed in accordance with OECD TG249: cell viability was assessed after 24 hours exposure using a multiple-endpoint assay indicative of cell metabolic activity, membrane integrity and lysosome integrity. Finally, chemical composition of the exposure medium was analyzed to assess which chemicals could be responsible for the observed acute effects. Our results show that metabolic activity was the most sensitive indicator of CMTT and CMTT digestate toxicity. EC50 values after direct exposure to RTgill-W1 and RTgutGC cells were estimated at 2.01 g/L and 3.80 g/L, respectively. 2-Mercaptobenzothiazole was found at the highest concentration among organic chemicals leaching out from the particles. It could be a major contributor to the loss in metabolic activity based on its toxicity to rainbow trout in vivo, although additional particle or mixture effects cannot be ruled out at this point. For digestate toxicity, EC50 was determined at 12.15 g of tire particle/L of digestive fluid. The observed toxicity could be due to high amounts of Zn, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD), 1,3-Diphenylguanidine (DPG) or 2-Mercaptobenzothiazole leaching out during in vitro digestion. Traces of 6PPD-quinone were also detected in the exposure medium, but additional cytotoxicity assays using the RTgill-W1 cell line showed no significant toxicity of this compound up to 3 mg/L. Overall, our in vitro toxicity data agree with reports of acute fish (in vivo) toxicity and show that acutely toxic concentrations of CMTT are well above concentrations measured in river water (0.3 to 4 mg/L). However, we determined the highest no-observed-effect concentration at 10 mg/L, while up to 100 mg/L were measured in road runoffs.

2021

Endocrine disruption in soil invertebrates

Sophie Campiche

In the past years, it has been observed that some compounds present in our environment can disturb the reproduction and development of animals like fishes, birds, or reptiles by interfering with their endocrine system. Indeed, these endocrine disrupting compounds (EDC) can mimic or antagonize the effects of hormones, alter the pattern of synthesis and metabolism of hormones or modify hormone receptor levels. These substances represent a risk for wildlife, and possibly for humans. Up to now, endocrine disruption was mainly evaluated for vertebrates and aquatic organisms and for oestrogeniclike substances. However, soil invertebrates, which play an important role in soil functioning, have rarely been considered. Moreover, as their endocrine system differs substantially from those of vertebrates (estrogens do not seem to regulate endocrine functions in invertebrates), other substances than can mimic invertebrate hormones should be taken into account. In this sense, insect growth regulators (IGR), which are third generation insecticides specially developed to interfere with insect endocrine system, are interesting compounds. These substances are supposed to have a high specificity for insect pest and a low toxicity for non-target organisms. In the first part of this study, the sublethal effects of six IGR (methoprene, fenoxycarb, precocene II, tebufenozide, hexaflumuron and teflubenzuron) were evaluated on the non-target soil arthropod Folsomia candida. The collembola F. candida represents an integral and beneficial part of the soil ecosystem. It is an euedaphic (subsurface) species which plays an important role in soil respiration and decomposition processes and is therefore vulnerable to the effects of soil contamination. This ecologically relevant organism is one of the most appropriate invertebrate test species for the assessment of environmental quality. It is recommended as test organism by the international standard ISO 11267. The 28-days reproduction tests conducted according to this protocol show that F. candida is affected by the chosen IGR. The most toxic compounds were the two chitin synthesis inhibitors, teflubenzuron and hexaflumuron, with an EC50 of 0.05 mg/kg (dw) for teflubenzuron and an EC50 of 0.6 mg/kg for hexaflumuron. These concentrations are probably environmentally relevant (toxicity/exposure ratios

EPFL2006

Adsorption of progesterone onto microplastics and its desorption in simulated gastric and intestinal fluids

Florian Frédéric Vincent Breider, Dominique Grandjean, Yang Liu, Thibault Béranger Masset, Cécilia Laetitia Carla Siri

The sorption of Hydrophobic Organic Compound (HOC) onto microplastics is relatively well reported in the literature, while their desorption remains poorly investigated, and especially in biological ﬂuids. The present study investigated the sorption and desorption of progesterone on polyethylene (PE), polypropylene (PP) and polystyrene (PS) microplastics. The sorption experiments showed that the equilibrium was reached in a few hours for all plastics. A sorption efﬁciency of 357.1 µg/g was found for PE and PS and 322.6µg/g for PP. Sorption experiments indicated that adsorption would happen certainly via surface sorption and potentially pore-ﬁlling mechanism. The desorption was carried out in Simulated Gastric Fluid (SGF) and Simulated Intestinal Fluid (SIF), whose formulations were more complex than similar models reported so far. It has been found that the desorption was higher in SIF compared to SGF, surely due to micelle formation in SIF promoting the pollutant solubilization. Sorption of pepsin onto microplastics has also been revealed, suggesting a competition between pollutant and pepsin for sorption sites and a potent reduction of pollutant solubilization. This study indicates that microplastics ingestion could be considered as as additional route of exposure of pollutants and therefore emphasizes pollutants bioavailability for aquatic organisms.

2021

In vitro acute toxicity assessment of tire tread particles using rainbow trout cell lines of gill and intestine

Florian Frédéric Vincent Breider, Benoît Jean Dominique Ferrari, Thibault Béranger Masset, Kristin Schirmer

2021

Endocrine disruption in soil invertebrates

Sophie Campiche

EPFL2006