Sorption of tetrabromobisphenol A onto microplastics: Behavior, mechanisms, and the effects of sorbent and environmental factors.

Microplastics (MPs) and halogenated organic pollutants coexist in ambient water and MPs tend to sorb organic pollutants from surrounding environments. Herein, a study on the sorption behavior of tetrabromobisphenol-A (TBBPA) onto four different MPs, namely, polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC) was carried out. Effects of MPs properties and environmental factors, including the type, surface charge and pore volume as well as the ionic strength (Ca2+) and humic acid (HA) on the sorption of TBBPA were discussed. Results showed that the sorption of TBBPA onto the MPs could reached an equilibrium within 24 h, and the sorption capacities decreased in the following order -PVC (101.85 mg kg-1) >PS (78.95 mg kg-1) >PP (58.57 mg kg-1) >PE (49.43 mg kg-1). Adsorption kinetics data fitted by intraparticle diffusion model revealed both surface sorption and intraparticle diffusion contributed, in the interfacial diffusion stage approximately 11-29% of TBBPA slowly diffused onto the surface of the MPs, and finally, in the intraparticle diffusion stage. The increase of Ca2+ concentration could promote the sorption of TBBPA by PE, PP, and PS, but no significant alteration for PVC. For all the four MPs, HA was found to exert a negative effect on TBBPA sorption. The adsorption was mainly driven by hydrophobic partition and electrostatic interactions.

Health assessment based on exposure to microplastics in tropical agricultural soil.

Microplastic (MP) pollution of agricultural soils has caused global alarm over its widespread distribution and potential risks to terrestrial ecosystems and human health. This study assessed human health based on exposure to soil MPs through a comprehensive investigation of the factors influencing their occurrence and spatial distribution on Hainan Island, South China. The results showed that the abundance of soil MPs was 1128.6 ± 391.5 items·kg-1, whereas the normalized abundance of MPs based on using a power-law function was 19,261.4 items·kg-1. Regarding the extent of population exposure to agricultural soil MPs, the average daily exposure dose (pADD) model revealed that using mass as an indicator to assess the health risks associated with MP intake is more reliable than using abundance. However, abundance-based exposure assessments are also relevant because MPs with smaller particle sizes are more harmful to human health. Moreover, for adults, the normalized pADD values based on abundance and mass were 1.68E-02 item MPs·kg BW-1·d-1 and 7.23E-02 mg MPs·kg BW-1·d-1, respectively. Although the multidimensionality of MPs should be further aligned and quantified, the preliminary findings of this study contribute to the development of human health risk assessment frameworks for soil MPs.

Polystyrene microplastics (PS-MPs) toxicity induced oxidative stress and intestinal injury in nematode Caenorhabditis elegans.

To understand the toxicity and mechanism of polystyrene microplastics (PS-MPs) exposure, Caenorhabditis elegans (C. elegans) was exposed to various concentrations (0, 0.1, 1, 10, and 100 µg/L) of PS-MPs, and the levels physiological, biochemical, and molecular parameters were measured as endpoints. Subacute exposure to 1-100 µg/L of PS-MPs resulted in adverse physiological effects in C. elegans, and PS-MPs were ingested and accumulated in the intestine of C. elegans. Exposure to 100 µg/L of PS-MPs significantly increased reactive oxygen species (ROS) production, lipofuscin accumulation, and the expression oxidative stress-related genes, which suggests that PS-MPs exposure induced oxidative stress by ROS. In addition, exposure to 100 µg/L of PS-MPs caused a hyperpermeable state of the intestinal barrier and altered the expression of genes related to intestinal development, which indicates intestinal damage in C. elegans. According to Pearson correlation analyses, oxidative stress and intestinal damage were significantly correlated with adverse effects of PS-MPs in C. elegans. Therefore, it was speculated that the toxicity induced by PS-MPs resulted from the combination of oxidative stress and intestinal injury.