Micro- and nanoplastics released from biodegradable and conventional plastics during degradation: Formation, aging factors, and toxicity.

The use of biodegradable plastics may solve the pollution caused by conventional plastics in the future. However, microplastics and nanoplastics are produced during the aging process of biodegradable plastics. This work evaluated the formation of secondary microplastics and nanoplastics and the effects of aging factors (UV radiation and mechanical forces) during the degradation processes of various biodegradable plastics (poly(butylene adipate co-terephtalate) (PBAT), poly(butylene succinate) (PBS), and polylactic acid (PLA)) and conventional plastics (polyethylene (PE), polystyrene (PS), and polyvinyl chloride (PVC)). This study also assessed the combined toxicity of secondary microplastics and Triclosan (TCS) on Tigriopus japonicas. The results showed that PLA and PBS could produce many microplastics. Most secondary microplastics were smaller than 50 µm. Primary pellets were more likely to generate microplastics through mechanical degradation than via photooxidation. In contrast, PBAT/PLA and PE bags were more likely to form microplastics through photooxidation than mechanical degradation. The secondary microplastics did not affect the survival of T. japonicas and the toxicity of TCS. This study highlights that risk assessment of biodegradable plastics, especially secondary microplastics, and nanoplastics, should be assessed in future studies.

Rhodamine B dye staining for visualizing microplastics in laboratory-based studies.

In the recent years, microplastics have attracted much attention as new emerging environmental pollutants. Previously, several studies were performed to understand the source and fate of microplastics in the environment, organisms, and food webs. To track microplastics and improve their legibility, labeling them is a very effective method during laboratory experiments. This study presents an effective Rhodamine B dye (RhB) staining method for microplastics. The method is crucial for the visual observation of white or transparent plastics by dyeing them in purple or pink, as well as makes the microplastics to fluoresce under common microscope fluorescence filter ranges. Five types of microplastic polymers, namely polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyurethane were used as the test materials. The efficiencies of ethanol, acetone, and distilled water as possible solvents for dissolving RhB were investigated. Next, the fluorescence stability in various conditions was assessed. The results indicated that ethanol was the most appropriate solvent in dissolving RhB used in staining the microplastics. RhB was fluorescently stable under varying conditions (light and gut fluid) or different solutions (KOH, nitric acid, and saturated NaCl). Additionally, RhB staining exhibited an insignificant effect on the Raman spectra of the microplastics. Our proposed method is simple and robust and helps to visualize the different types of microplastic polymers tested in laboratory experiments, particularly the transparent, white, and small size microplastics.

Adsorption and Desorption of Triclosan on Biodegradable Polyhydroxybutyrate Microplastics.

Biodegradable plastics have been increasingly used as a solution to the problem of plastic pollution in recent years. However, there are few studies on the negative effects of biodegradable microplastics. Triclosan, a widely used disinfectant, is a highly toxic substance. In the present study, the adsorption and desorption processes of triclosan on a type of biodegradable plastics, polyhydroxybutyrate (PHB), were investigated and also compared with one conventional plastic type, polyethylene. The adsorption equilibrium quantities of polyethylene and PHB were 3431.85 and 9442.27 µg/g, respectively. The adsorption rate and equilibrium adsorption capacity of triclosan on PHB are much higher than on polyethylene. Physical adsorption of triclosan on PHB and polyethylene microplastics may play a dominant role in this process. The desorption hysteresis indices are all less than zero; this indicates that triclosan is easily released from PHB and polyethylene microplastics under physiological conditions. Our results indicate that biodegradable PHB microplastics are stronger carriers for triclosan than the conventional polyethylene microplastics in the aquatic environment. Environ Toxicol Chem 2021;40:72-78. © 2020 SETAC.

Occurrence and identification of microplastics in tap water from China.

Microplastics as new emerging pollutants in aquatic environments have received much attention in recent years. However, up to now, microplastic contamination in tap water has only been investigated by few studies. Therefore, this study investigated the presence of microplastics in tap water. 38 tap water samples were taken at different cities of China. The amount of microplastics in tap water varied from 440 ± 275 particles L-1. Particles smaller than 50 µm significantly predominated in most of the tap water samples. Further, according to the shape of these particles, fragments, fibers and spheres were found in tap water samples, while fragments were the most abundant morphotype in most samples. Despite these particles were identified as 14 different materials by micro-Raman spectroscopy, the majority of the microplastics comprised of polyethylene and polypropylene. Based on this investigation, drinking water treatment plants seemingly have to face the problem of microplastic pollution in tap water due to their potential eco-toxicological effects on humans.