Virgin and UV-weathered polyamide microplastics posed no effect on the survival and reproduction of Daphnia magna.

Although evidence suggests that microplastic (MP) particles pose a risk to organisms, the effects of virgin and weathered MP should be evaluated separately as their effects may be different. In this work, we provide new information on the toxic potential of virgin and UV-weathered polyamide, one of the commonly used plastics worldwide. Polyamide MP particles were subjected to UV-weathering in wet conditions over 26 days in a customized irradiation chamber equipped with UV-C light tubes (15 W each, max. wavelength 254 nm). The toxicity of virgin and UV-weathered polyamide MP (< 180 µm in one dimension, 100 and 300 mg L-1) was evaluated by studying Daphnia magna reproduction in natural lake water spiked with MP, following the 21-day OECD 211 test guideline. In parallel, a nonionic surfactant Tween 20 (7 mg L-1) was added to the test medium to improve the suspendability of the MP. The results of the tests showed no adverse effects of either virgin or UV-weathered polyamide MP on the reproduction of D. magna. In addition, presence of Tween 20 in the test medium had no effects on the test results. These results bring a new perspective on the potential long-term impact of polyamide particles on aquatic organisms, especially considering that the polyamide has received marginal attention in the ecotoxicological research. However, standard test endpoints (survival and reproduction) may still miss long-term adverse effects of insoluble e.g., plastic particles and additional studies may be necessary.

Assessment of the mutagenic potential of the water of an urban river by means of two Tradescantia-based test systems.

River pollution can be caused by anthropogenic or natural factors. When testing water quality for the presence of toxic substances, higher plants as bioindicators for the genotoxic effects of complex mixtures are effective and appropriate. Hence, in this work the Tradescantia (clone 02) stamen hair mutations (Trad-SHM) and Tradescantia micronuclei (Trad-MCN) were used to determine mutagenic and clastogenic potential of an urban river. A significant increase in the level of all studied endpoints as well as morphological changes, including pink cells (PC) and colorless cells (CC) in stamen hairs, stunted hairs (SH), tetrads with micronuclei (MN) and MN in tetrads of pollen microspores in the Tradescantia was observed compared to the negative control (tap water). As an example riverine system, part of the River Hrazdan (Armenia) flowing through a highly urbanized and industrial area was studied. The positive control (10 mM CrO3) showed the highest genotoxicity for the SHM assay (PC: 5.1 / 1000, CC: 17.9 / 1000) and for the MCN assay (12 MN / 100 tetrads and 9.4 ± 0.53 tetrads with MN). Genetic responses were analyzed in conjunction with the concentrations of select elements in the riverine water. Reasons for observing such a high level of genetic markers in the riverine water and applicability of the Tradescantia (clone 02) test-systems in environmental risk assessment and biomonitoring are discussed.

Polyamide microplastic exposure elicits rapid, strong and genome-wide evolutionary response in the freshwater non-biting midge Chironomus riparius.

Susceptibility to hazardous materials and contamination is largely determined by genetic make-up and evolutionary history of affected organisms. Yet evolutionary adaptation and microevolutionary processes triggered by contaminants are rarely considered in ecotoxicology. Using an evolve and resequencing approach, we investigated genome-wide responses of the midge C. riparius exposed to virgin polyamide microplastics (0-180 µm size range, at concentration 1 g kg-1) during seven consecutive generations. The results were integrated to a parallel life-cycle experiment ran under the same exposure conditions. Emergence, life-cycle trait, showed first a substantial reduction in larval survival, followed by a rapid recovery within three generations. On the genomic level, we observed substantial selectively driven allele frequency changes (mean 0.566 ± 0.0879) within seven generations, associated with a mean selection coefficient of 0.322, indicating very strong selection pressure. Putative selection targets were mainly connected to oxidative stress in the microplastics exposed C. riparius population. This is the first multigenerational study on chironomids to provide evidence that upon exposure to polyamide microplastic there are changes on the genomic level, providing basis to rapid adaptation of aquatic organisms to microplastics.

Evaluation of the potential toxicity of UV-weathered virgin polyamide microplastics to non-biting midge Chironomus riparius.

The relevance of the environmental hazard evaluation of virgin plastics particles is problematic, as plastics almost never occur in a virgin state after being discarded into the environment. However, the producers or importers must evaluate the environmental effect of their products as they are produced. Many plastic types e.g., polyamide, polyethylene are already under pre-registration, according to the database of the European Chemicals Agency (ECHA), in order to restrict the placing on the market of polymers (as defined by Article 3(5) of EU's REACH regulation (Registration, Evaluation, Authorization & Restriction of Chemicals), as a substance or in a mixture (ECHA, 2019). However, the hazard of microplastics could not be evaluated without relevant data on its (eco)toxic effects. In this work, the long-term toxicity of virgin polyamide microplastic (PA-MP) (size from 0 to 180 µm) and UV-weathered virgin PA-MP was investigated in the controlled life cycle experiments conducted in accordance with the OECD guidelines for testing of chemicals using Chironomus riparius (OECD test 218). In addition, a three-generation test was conducted to understand the trans-generational toxicity potential of virgin PA-MP. After UV irradiation (26 d) the buoyancy and color of the particles was changed and the share of smaller particles (of a few micrometer size range) increased. The exposure of C. riparius larvae to UV-weathered PA-MP (1000 mg kg-1) during their life cycle (28 d), negatively affected their development and subsequent emergence as adults. However, the exposure to virgin PA-MP throughout the life cycle and also over three consecutive generations did not significantly reduced the number of emerged adults. From the point of view of environmental hazard, the virgin polyamide plastics have probably no long-term hazard to chironomids. While it may not be relevant as environmental pollutant in the strict sense, UV-weathering may turn it hazardous.

Ingestion and effects of virgin polyamide microplastics on Chironomus riparius adult larvae and adult zebrafish Danio rerio.

Secondary microplastics (MP) produced by fragmentation of plastic in the environment or as a result of human activities can easily be taken up by organisms. The harmful effects of MP depend on e.g., the type, dimensions, sorption capacity and concentration of MP. In this study the ingestion of virgin irregularly-shaped polyamide microplastics (PA-MP; up to180 µm) by two different species was evaluated: 3rd - 4th instar larvae of midge Chironomus riparius and adult fish Danio rerio. More specifically, in the case of C. riparius larvae their feeding strategy, i.e. the ability to differentiate between food and non-food material (PA-MP) and the impact of pseudo-satiation by PA-MP on larval growth, development and emergence was evaluated. Two feeding regimes (with and without food supply) and two PA-MP concentrations (100 mg kg-1 and 1000 mg kg-1) were applied. Fish were exposed to two PA-MP concentrations (30 and 330 mg L-1) for 48 h followed by 48 h of depuration. The fish were fed during both periods. Both, chironomid larvae and adult zebrafish actively ingested PA-MP. Remarkably more PA-MP was ingested when larvae were not fed during the exposure to PA-MP. In the case of fish, the ingested particles were effectively evacuated from the gastrointestinal tract. Even the highest PA-MP concentrations did not cause obvious harmful effects to either species. The obtained data are informative for risk evaluation of PA-MP as polyamide is registered in the database of the European Chemicals Agency (ECHA) in the framework of the EU's REACH (Registration, Evaluation, Authorization & Restriction of Chemicals) regulation.

Hazard evaluation of polystyrene nanoplastic with nine bioassays did not show particle-specific acute toxicity.

Plastic is a wide-spread pollutant and must be evaluated for potential adverse effects of its breakdown product, microplastic (≤5 mm) along with its subfraction, nanoplastic (1-100 nm). Risk assessment of pollutants cannot be conducted without their toxicity (dose-response) data. In this study, toxicity of polystyrene nanoplastics (PS-NPL) was evaluated using 8 acute and 1 subchronic toxicity assays with 10 organisms of different biological complexity (bacteria, yeast, algae, protozoans, mammalian cells in vitro, crustaceans, midge larvae). Commercial 26 and 100 nm carboxylated PS-NPL spheres were chosen as model and tested in nominal concentrations up to 100 mg/L (1.025·1016 26 nm and 1.83·1014 100 nm particles/L). In most of the assays, both PS-NPL proved non-toxic (L(E)C50 > 100 mg/L) but three tests (V. fischeri, R. subcapitata, D. magna) flagged toxicity in 'as received' 26 nm PS-NPL and D. magna also in 100 nm PS-NPL (EC50 ranging from 13 to 71 mg/L). As, according to manufacturers, both PS-NPL suspensions contained additives (surfactants and biocidal NaN3), the three toxicity tests were repeated also on dialysed PS-NPL and on NaN3. Non-toxicity of dialysed PS-NPL indicated that the toxicity of 'as-received' PS-NPL was not particle-specific but false positive due to water-soluble additives in the PS-NPL preparations. NaN3 was very toxic to D. magna (48 h EC50 = 0.05 ± 0.03 mg NaN3/L), toxic to R. subcapitata (72 h EC50 = 4.97 ± 3.7 mg NaN3/L) and non-toxic to V. fischeri. Toxicity of 'as-received' PS-NPL was not fully explainable by NaN3 but also attributable to other additives in the suspensions. Toxicity research of microplastic using commercial model particles must always consider the potential influence of additives, e.g. test the toxicity of dialysed NPL for comparison. In our study, D. magna, R. subcapitata and V. fischeri were the most sensitive to PS-NPL water-soluble additives and flagged their presence in NPL preparations.

Evaluation of the hazard of irregularly-shaped co-polyamide microplastics on the freshwater non-biting midge Chironomus riparius through its life cycle.

Plastics pollution is increasingly attracting societal and political attention. However, despite extensive research effort recently dedicated to the hazard of plastics in the environment, the data obtained are often redundant and essential knowledge gaps exist: available freshwater ecotoxicity data mostly concern Daphnia magna and are derived from acute exposure to spherical particles. In this paper, we address this gap by exploring the biological effects of irregularly-shaped co-polyamide (PA, 10-180 µm) on Chironomus riparius - a very versatile organism that during its life-stages inhabits both sediment and water column - relevant compartments for microplastics (MP) pollution. C. riparius represents an important part of the freshwater food chain and is also a standard OECD test organism. Different toxicity endpoints along the life cycle of C. riparius (28 days) were used as described in OECD 218: emergence, time to emergence, sex ratio of imagoes and the number of egg clutches per female. Chironomid larvae were exposed to 100 mg PA kg-1 (i.e., 10,100 particles kg-1) sediment throughout. Soluble Zn-salt (1 mg Zn L-1) was used as a positive control and as a co-pollutant in combination with PA. We demonstrated that the tested concentrations of PA and Zn alone as well in combination showed no adverse effects for C. riparius in chronic exposures. 100 mg PA kg-1 also did not affect the life cycle traits of the offspring of PA-exposed parent Chironomids. The data obtained will be useful for environmental risk assessment of PA when actual environmental concentrations of PA will be available.

Effects of a hypothetical escape of CO2 gas from subterranean storage sites on water flea Daphnia magna.

The impacts of a hypothetical CO2 gas leak from freshwater sediments on the survival and reproduction of freshwater flea Daphnia magna were analyzed. Another objective was to assess the performance of standard toxicity testing protocols for CO2-induced acidification research in freshwaters. Four pH levels (7.5, 7.0, 6.5, and 6.0) and two sediments with different contamination level were tested. The results revealed that the D. magna are susceptible to a gradual but relatively rapid CO2 enrichment of the water column causing a change from circumneutral to acidic conditions. Standard 48-h immobilization test with D. magna tended to underestimate the toxicity at CO2-induced acidity condition. Dissolved aluminum may be implicated in the toxicity to the parental daphnids exposed. Metal outflux from sediments and behavior in elutriate have been discussed.

The influence of ph and waterborne metals on egg fertilization of the blue mussel (Mytilus edulis), the oyster (Crassostrea gigas) and the sea urchin (Paracentrotus lividus).

This study evaluated the combined effect of pH and metals on the egg fertilization process of two estuarine species, the blue mussel (Mytilus edulis), the oyster (Crassostrea gigas) and a marine species, the sea urchin (Paracentrotus lividus). The success of egg fertilization was examined after exposure of gametes to sediment extracts of various degrees of contamination at pH 6.0, 6.5, 7.0, 7.5 and 8.0. At the pH levels from 6.5 to 8.0, the egg fertilization of the different species demonstrated different sensitivity to metal and/or acidic exposure. In all species, the results revealed that egg fertilization was almost completely inhibited at pH 6.0. The egg fertilization of the blue mussel M. edulis was the least sensitive to the exposure while that of the sea urchin P. lividus demonstrated a concentration-dependent response to the pH levels from 6.5 to 8.0. The results of this study revealed that acidity increased the concentration of several metal ions (Cr, Ni, Cu, Zn, Cd, and Pb) but reduced its availability to the organisms, probably related to the reactivity of the ions with most non-metals or to the competition among metals and other waterborne constituents.

Dredged material characterization and management frameworks: A case study at the port Vilagarcia (NW, Spain).

The potential impact of dredged sediment has been assessed at sixteen areas of the high-traffic port of Vilagarcia (Northwest Spanish Atlantic coast). The assessment has been done by three weight-of-evidence tools, which integrated data on sediment characteristics and toxicity responses of Ampelisca brevicornis, Vibrio fischeri and eggs and embryos of Paracentrotus lividus. Two of the tools also represented management options regarding the disposal of dredged material. The comparison of the logic in these tools revealed essential differences in the type and the necessity of bioassays and threshold values for chemical concentrations. However, despite this difference, assessment results and the derived management options coincided in most of the sediments. The potential toxicity of sediments was relatively low especially for eggs and embryos possibly due to different contaminant availability in solid and liquid phases. The importance of a battery of toxicity tests in the dredged material quality assessment has been emphasized to avoid an underestimation of sediment toxicity for solid phase organisms, if only liquid phase responses are considered. The potential false implications, which may result from the application of the third tool, were highlighted. The strengths and weaknesses of the tools were discussed from the dredged material management perspective.