[Photodegradation of Plastic Blends in Seawater and Its Risk to the Marine Environment].

The production and use of plastic blends have been gradually increasing owing to their versatility and low cost. However, the photodegradation of plastic blends in seawater and the potential risk to the marine environment are still not well understood. In this study, plastic blends including polypropylene/thermoplastic starch blends(PP/TPS) and polylactic acid/poly(butylene adipate-co-terephthalate)/thermoplastic starch blends(PLA/PBAT/TPS) were investigated. The corresponding neat polymers, namely polypropylene(PP) and polylactic acid(PLA), were set as control groups. We investigated the formation of MPs and the changes in the physicochemical properties of plastic blends after photodegradation in seawater. The size distribution of MPs indicated that PP/TPS and PLA/PBAT/TPS were more likely to produce small-sized particles after photodegradation than PP and PLA owing to their poorer mechanical properties and lower resistance to UV irradiation. Noticeable surface morphology alterations, including cracks and wrinkles, were observed for plastic blends following photodegradation, whereas PP and PLA were relatively resistant. After photodegradation, the ATR-FTIR spectrum of PP/TPS and PLA/PBAT/TPS showed a significant decrease in the characteristic bands of thermoplastic starch(TPS), indicating the degradation of their starch fractions. The C 1s spectra demonstrated that aged plastic blends contained fewer -OH groups than the pristine MPs did, further confirming the photodegradation of TPS. These results indicate that PP/TPS and PLA/PBAT/TPS had a higher degree of photodegradation than PP and PLA and thereby generated more small-sized MPs. In summary, plastic blends may pose a higher risk to the marine environment than neat polymers, and caution should be taken in the production and use of plastic blends.

Occurrence of microplastics in three types of household cleaning products and their estimated emissions into the aquatic environment.

Microplastics (MPs) in household cleaning products are a significant source of primary MPs. However, their presence in these products remain largely unknown. In this study, three types of common household cleaning products (laundry detergents, toilet bowl cleaners, and dishwashing detergents) were examined to assess the presence of MPs. The potential global emissions of MPs into aquatic environments resulting from the use of these products were estimated using statistics on global wastewater treatment plants (WWTPs) and household cleaning product markets. The average abundance of MPs in household cleaning products was 564.97 ± 327.83 n·kg-1, with toilet bowl cleaners having a significantly higher abundance than the other two products. The most commonly detected polymers in these products were polyamide (PA), silicone, polyurethane (PU), acrylate copolymer (ACR), polyethylene (PE), and polyethylene terephthalate (PET), while the size of the MPs ranged from 21.34 to 442.97 µm, with 81.52 % being <50 µm and 87.32 % being fragment-shaped. The estimated annual MP emissions from these three types of household cleaning products were 3.88 × 1013 ± 1.35 × 1013, with toilet bowl cleaners accounting for 56.44 % of the total emissions. MPs directly released without treatment in WWTPs (2.46 × 1013 n year-1) accounted for 63.40 % of the total emissions, highlighting the importance of increasing the treated rate of wastewater to reduce MP emissions. Sensitivity tests indicated that increasing the MP removal rates of secondary and tertiary WWTPs could also effectively reduce MP emissions. Moreover, gross and per capita MP emissions in 149 countries showed significant differences, which could be attributed to population, market size, demand for household cleaning products, and the level of MP removal among different countries. The findings of this study provide important insights into controlling MP contamination in household cleaning products.

Potential risk of microplastics in processed foods: Preliminary risk assessment concerning polymer types, abundance, and human exposure of microplastics.

The occurrence of microplastics (MPs) has been widely reported in human foodstuffs, and their potential negative effects on human health have been brought into focus. Processed foods are more susceptible to MPs as contamination can be introduced during processing and packaging. However, the risk posed by MPs in processed foods remained unclear. This work aims to critically review the available data for MPs in 11 types of possessed foods and to conduct a preliminary risk assessment of MPs in processed foods. For a comprehensive evaluation, three indicators were selected and determined, namely chemical risk, pollution load, and estimated daily intake (EDI). Our results suggest that nori has the highest chemical risk, followed by canned fish, beverages, table salt, and other food items. In the case of pollution load, nori and milk fall into the risk category of Ⅳ and Ⅲ respectively. Table salts, bottled water, and sugar exhibited lower MPs pollution load (risk category of Ⅱ), whereas the pollution loads of other foods were calculated to be category Ⅰ. Moreover, a correlation between the pollution load of sea salts and MPs pollution level in ambient seawater was found. Regarding EDI of MPs from different processed foods, MPs intakes through bottled water (14.3 ± 3.4 n kg-1 d-1) and milk (6.6 ± 2.4 n kg-1 d-1) are significantly higher than that of the other foods (< 1 n kg-1 d-1). The probabilistic estimation of MPs daily intake indicated that children (19.7 n kg-1 d-1) are at a higher health risk than adults (female: 17.6 n kg-1 d-1, male: 12.6 n kg-1 d-1). Nevertheless, the exposure dose used in toxicological studies was about 10 times higher than the MPs intake via processed foods. Therefore, we argued that MPs in processed foods only carry limited risk. Overall, this study would provide the basis for risk management of MPs in processed food products.

[Distribution Characteristics of Microplastics in Qingdao Coastal Beaches].

Microplastics (MPs, plastic fibers, debris, or particles that are generally smaller than 5 mm in diameter) can serve as carriers for hazardous substances, which are ingested by organisms in the ocean and can affect their growth and metabolism. Moreover, MPs will spread with ocean currents, and MP pollution has become a global problem. In this study, the MP abundance distribution of four typical beaches near the coast of Qingdao was studied by the combination of ordinary microscope and fluorescence microscope methods. In addition, the distribution of MPs collected from various beaches in different particle size ranges, shapes, and chemical compositions was discussed. Abundances on the sea surface varied between 5.05×103 particles·m-3 and 1.25×104 particles·m-3, and the concentration of MPs in sand varied between 1.91×103 particles·m-2 and 4.35×103 particles·m-2, with no significant differences detected among the four beaches examined. The results show the pervasiveness of MP pollution in coastal environments of Qingdao. The size of particles found in this study ranged from 5 mm to 50 µm, and increases in abundance were detected with the decreasing particle size. Polypropylene (PP), polyethylene (PE), polystyrene (PS), polyethylene terephthalate (PET), polyvinyl chloride (PVC), 96% polystyrene+4% butadiene copolymer (SB), polymethyl acrylate (PMA), and polyamide (PA) were present in seawater in coastal environments of Qingdao, and compared with the seawater samples, no PA or PMA were found in sand. Research results indicated that fiber was dominant in seawater and sand. MPs in the sand were similar to those in seawater in terms of the particle size, shape, and composition, thus indicating that the seawater and sand of the bathing beaches in Qingdao may have the same pollution sources, e. g., the packaging industry, clothing textile industry, and tourism. This paper studies the distribution and sources of MPs in the bathing beaches of Qingdao, and it provides basic data for research and supervision of environmental MP pollution in Chinese coastal zones.