Plastic mulching, and occurrence, incorporation, degradation, and impacts of polyethylene microplastics in agroecosystems

Polyethylene microplastics have been detected in farmland soil, irrigation water, and soil organisms in agroecosystems, while plastic mulching is suggested as a crucial source of microplastic pollution in the agroecosystem. Plastic mulch can be broken down from plastic mulch debris to microplastics through environmental aging and degradation process in farmlands, and the colonization of polyethylene-degrading microorganisms on polyethylene microplastics can eventually enzymatically depolymerize the polyethylene molecular chains with CO2 release through the tricarboxylic acid cycle. The selective colonization of microplastics by soil microorganisms can cause changes in soil microbial community composition, and it can consequently elicit changes in enzyme activities and nutrient element content in the soil. The biological uptake of polyethylene microplastics and the associated disturbance of energy investment are the main mechanisms impacting soil-dwelling animal development and behavior. As polyethylene microplastics are highly hydrophobic, their presence among soil particles can contribute to soil water repellency and influence soil water availability. Polyethylene microplastics have been shown to cause impacts on crop plant growth, as manifested by the effects of polyethylene microplastics on soil properties and soil biota in the agroecosystems. This review reveals the degradation process, biological impacts, and associated mechanisms of polyethylene microplastics in agroecosystems and could be a critical reference for their risk assessment and management.

Is there any biological insight (or respite) for insects exposed to plastics? Measuring the impact on an insects central carbon metabolism when exposed to a plastic feed substrate

Insects used to treat organic waste streams and produce valuable protein products are increasingly exposed to plastic contaminated source material assimilating plastic carbon into organic biomass, which is pervasive and hazardous to organisms. Our understanding of this increased insect-plastic interaction remains limited and needs urgent scientific attention if plastic biodegradation and production rates of quality protein are to be improved. Herein, we investigated the biochemical impact of various plastics using three insect models. Black Soldier Fly (BSF), Mealworm (MW), and Wax Moth (WM) larva were each exposed to a plastic substrate (PET, PE, PS, Expanded PE, PP, and PLA) as the primary carbon source for five days to explore any positive metabolic benefits in terms of insect performance and plastic degradation potential. Central carbon metabolism (CCM) metabolites were analyzed via a targeted tMRM liquid chromatography triple quadrupole mass spectrometry (LC-QqQ-MS) method. Unique expressed pathways were observed for each insect model. When reared on PET, BSF larvae were found to have an elevated pyrimidine metabolism, while the purine metabolism pathway was strongly expressed on other plastics. BSF also exhibited a downregulated Vitamin B6 metabolism across all plastics, indicating a likely gut-symbiont breakdown. The MW and WM model insects were metabolically more active on PLA and expanded foam plastics. Further, WM exhibited an elevation in Vitamin B6 metabolism. This data suggests a positive insect-specific interaction towards certain plastic types that warrants further investigation. It is anticipated that through deeper insight into the metabolic impact and benefits afforded from certain plastics, an insect biotransformation pipeline can be established that links fit-for-purpose insect models to individual plastic types that address our growing plastic waste issue.

The antineoplastic drugs cyclophosphamide and cisplatin in the aquatic environment - Review

Cyclophosphamide (CP) and Cisplatin (CDDP) are antineoplastic drugs widely used in the treatment of neoplastic diseases that have been detected in the aquatic environment. This review summarizes the current knowledge on the presence in the aquatic environment of these two drugs and their effects on freshwater and marine invertebrates, which includes good model species in ecotoxicology and risk assessment programs. The consumption levels, occurrence in freshwater and marine ecosystems, and the impacts exerted on aquatic organisms, even at low concentrations, justifies this review and the selection of these two drugs. Both pharmaceuticals were detected in different aquatic environments, with concentrations ranging from ng L^-1 up to 687.0 μg L^-1 (CP) and 250 μg L^-1 (CDDP). The available studies showed that CP and CDDP induce individual and sub-individual impacts on aquatic invertebrate species. The most common effects reported were changes in the reproductive function, oxidative stress, genotoxicity, cytotoxicity and neurotoxicity. The literature used in this review supports the need to increase monitoring studies concerning the occurrence of antineoplastic drugs in the aquatic environment since negative effects have been reported even at trace concentrations (ng L^-1). Furthermore, marine ecosystems should be considered as a priority since less is known on the occurrence and effects of antineoplastic drugs in this environment comparing to freshwater ecosystems.