Primary and Secondary Plastic Particles Exhibit Limited Acute Toxicity but Chronic Effects on Daphnia magna.

Nanoplastics (NPs; <0.1 µm) are speculated to be a bigger ecological threat due to their predicted wider distribution, higher concentrations, and bioavailability. Primary NPs are manufactured to be that size, while secondary NPs originate from fragmentation of bigger debris. To date, the long-term impact of NPs in freshwater systems, particularly secondary NPs, is not well-understood. Thus, we employed a freshwater invertebrate, Daphnia magna, to investigate the chronic effects of model primary NPs, fluorescent polystyrene nanospheres (PS-NPs; 20 nm), and water leachate of weathered single-use plastics that contained micro- and nanosized particles. In experiment 1, parent Daphnia (F0) were exposed to 1 and 50 mg/L PS-NPs until the production of the neonates (F1) followed by a two-generation recovery. PS-NPs were mainly detected in the intestine and brood chamber in F0 and transferred to F1 and F2. PS-NPs significantly decreased the appendage curling and heartbeat rate in F0 and reduced reproduction in F2. In experiment 2, the plastic leachate also reduced the appendage curling rate but increased growth and reproduction. The results suggest that the acute toxicity of primary and secondary plastic particles is low even at high concentrations, but their chronic and sublethal effects should not be overlooked.

Weathering pathways and protocols for environmentally relevant microplastics and nanoplastics: What are we missing?

To date, most studies of microplastics have been carried out with pristine particles. However, most plastics in the environment will be aged to some extent; hence, understanding the effects of weathering and accurately mimicking weathering processes are crucial. By using microplastics that lack environmental relevance, we are unable to fully assess the risks associated with microplastic pollution in the environment. Emerging studies advocate for harmonization of experimental methods, however, the subject of reliable weathering protocols for realistic assessment has not been addressed. In this work, we critically analysed the current knowledge regarding protocols used for generating environmentally relevant microplastics and leachates for effects studies. We present the expected and overlooked weathering pathways that plastics will undergo throughout their lifecycle. International standard weathering protocols developed for polymers were critically analysed for their appropriateness for use in microplastics research. We show that most studies using weathered microplastics involve sorption experiments followed by toxicity assays. The most frequently reported weathered plastic types in the literature are polystyrene>polyethylene>polypropylene>polyvinyl chloride, which does not reflect the global plastic production and plastic types detected globally. Only ~10% of published effect studies have used aged microplastics and of these, only 12 use aged nanoplastics. This highlights the need to embrace the use of environmentally relevant microplastics and to pay critical attention to the appropriateness of the weathering methods adopted moving forward. We advocate for quality reporting of weathering protocols and characterisation for harmonization and reproducibility across different research efforts.

Targeted screening of 11 bisphenols and 7 plasticizers in food composites from Canada and South Africa.

A sensitive method based on ultrasound-assisted liquid extraction coupled with liquid chromatography was applied to screen 18 plastic-related contaminants in 168 food composites (namely fish fillets, chicken breast, canned tuna, leafy vegetables, bread and butter) collected in Montreal (Canada), Pretoria and Vhembe (South Africa). Bisphenol A (BPA), bisphenol S (BPS) and seven plasticizers (di-n-butyl phthalate (DBP), diethyl phthalate (DEP), (2-ethylhexyl) phthalate (DEHP), di-(2-ethylhexyl) adipate (DEHA), di-isononyl phthalate (DINP), di-(isononyl)-cyclohexane-1,2-dicarboxylate (DINCH)) were detected in different foods from both countries. DBP and DEP were the most frequently detected contaminants in food collected in Montreal (75% for both) and DINP was the most frequently detected contaminant in food from South Africa (67%). DEHA concentration in packaged fish were significantly higher than the values for non-packaged fish (p < 0.01) suggesting that the packaging film can be one source of DEHA in fish.

Non-targeted screening of plastic-related chemicals in food collected in Montreal, Canada.

A non-targeted screening method based on ultrasound-assisted extraction followed by high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (HPLC-QTOF-MS) was developed to screen for the presence of plastic-related chemicals (PRCs) in different types of food (fish, chicken, canned tuna, leafy vegetables, bread and butter). Eleven bisphenols were used as targeted compounds. Instrument linearity (r2 ≥0.98), inter-day precision (RSD ≤9.0%) as well as method detection limits (MDLs below 3.6 ng g-1) were satisfactory. Recoveries of the eleven bisphenols ranged from 76% to 122% among the different food matrices. The method was applied to food collected from Montreal, Canada in 2017-2018. The non-targeted screening approach identified a range of contaminants in different food matrices, including BPA, BPS, bis(2-ethylhexyl) adipate, dibutyl adipate, hexadecyl methacrylate and Irganox®1076. Further research is suggested to investigate the concentration of these PRCs, the consumption habits of average and specific populations and the potential routes of contamination.

Suspect screening of plastic-related chemicals in northern pike (Esox lucius) from the St. Lawrence River, Canada.

Environmental contaminant monitoring traditionally relies on targeted analysis, and very few tools are currently available to monitor "unexpected" or "unknown" compounds. In the present study, a non-targeted workflow (suspect screening) was developed to investigate plastic-related chemicals and other environmental contaminants in a top predator freshwater fish species, the northern pike, from the St. Lawrence River, Canada. Samples were extracted using sonication-assisted liquid extraction and analyzed by high performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (HPLC-QTOF-MS). Ten bisphenol compounds were used to test the analytical performances of the method, and satisfactory results were obtained in terms of instrumental linearity (r2 > 0.97), recoveries, (86.53-119.32%), inter-day precision and method detection limits. The non-targeted workflow data processing parameters were studied, and the peak height filters (peak filtering step) were found to influence significantly the capacity to detect and identify trace chemicals in pike muscle extracts. None of the ten bisphenol analogues were detected in pike extracts suggesting the absence of accumulation for these chemicals in pike muscle. However, the non-targeted workflow enabled the identification of diethyl phthalate (DEP) and perfluorooctanesulfonic acid (PFOS) in pike extracts. This approach thus can be also applied to various contaminants in other biological matrices and environmental samples.

The permeation liquid membrane as a sensor for free nickel in aqueous samples.

There are currently a limited number of techniques to study nickel speciation in aqueous samples. This work reports on the use of the permeation liquid membrane (PLM) for that objective. In this paper, the composition of the organic phase was studied to maximize the Ni flux (thus the sensitivity of the device) over a wide Ni2+ concentration range (50 nM to 100 microM) in order to verify its ability to determine free Ni2+ in the presence of Ni complexes. A mixture containing 1,10-didecyl-1,10-diaza-18-crown-6 ether (22DD) and di(2-ethylhexyl)phosphoric acid (D2EHPA) in toluene/phenylhexane was selected as the optimized organic phase for the PLM. The PLM was shown to be a reliable tool to measure free nickel concentrations down to 10(-7) M. The effect of pH on Ni transport was also studied. Fluxes below pH 6 were reduced significantly, i.e. an order of magnitude smaller than fluxes above pH 7.8. Finally, as part of a broader study examining the ability of trace metals to induce antibiotic resistance in bacteria, we used the PLM to quantify the formation, at pH = 7.2, of a weak complex between Ni and Imipenem (a member of the carbapenem class of beta-lactam antibiotics) or its hydrolysis product(s).