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Microplastics exhibit lower carrying effects on the bioaccessibility and cytotoxicity of lead than montmorillonite
Peng Liu1, Jiamin Dai2, Jingxuan Liu2
1College of Natural Resources and Environment, Northwest A & F University, Yangling 712100, China; Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, Yangling 712100, China.
Abstract:
Microplastics (MPs) in the environment are always colonized by microbes, which may have implications for carrying effect of pollutants and exposure risk in organisms. We present the crucial impacts and mechanisms of microbial colonization on the bioaccessibility and toxicity of Pb(II) loaded in disposable box-derived polypropylene (PP) and polystyrene (PS) MPs and montmorillonite (MMT) clay particles. After 45 d incubation, higher biomass measured by crystal violet staining were detected in MMT (1.23) than in PP and PS (0.400 and 0.721) indicating preferential colonization of microbes in clay particles. Microbial colonization further enhanced the sorption ability toward Pb(II), but inhibited the desorption and bioaccessibility of enriched Pb(II) in zebrafish and decreased the toxicity to gastric epithelial cells in an order of MMT > PS ≈ PP. The crucial effects were mainly because microbe-colonized substrates possessed higher oxygen functional groups and specific surface area and exhibited stronger interactions with Pb(II) and digestive component (i.e., pepsin) than pure substrates. This decreased the available soluble pepsin for complexing with sorbed Pb(II). The findings highlight the role of microbial colonization in modulating the exposure risks of artificial and natural substrate-associated pollutants and suggest that the risks of MPs may be overestimated compared to clay particles.
Insights
Microbial colonization on microplastics (MPs) and clay particles affects lead (Pb(II)) bioaccessibility and toxicity. Colonization reduces Pb(II) exposure risk from MPs and clay, with clay posing less risk than MPs.
Area of Science:
- Environmental Science
- Microbiology
- Toxicology
Background:
- Microbes colonize environmental particles like microplastics (MPs) and clay.
- This colonization can alter the behavior and toxicity of associated pollutants, such as lead (Pb(II)).
Purpose of the Study:
- To investigate the impact of microbial colonization on Pb(II) bioaccessibility and toxicity associated with polypropylene (PP) and polystyrene (PS) MPs and montmorillonite (MMT) clay.
- To elucidate the mechanisms behind these observed effects.
Main Methods:
- Incubation of PP, PS MPs, and MMT clay with Pb(II) for 45 days.
- Quantification of microbial biomass using crystal violet staining.
- Assessment of Pb(II) desorption and bioaccessibility in zebrafish.
- Evaluation of toxicity to gastric epithelial cells.
Main Results:
- Microbial biomass was significantly higher on MMT clay compared to PP and PS MPs.
- Microbial colonization enhanced Pb(II) sorption but inhibited desorption and bioaccessibility.
- Toxicity to gastric cells decreased in the order MMT > PS ≈ PP.
- Colonized substrates showed increased oxygen functional groups and surface area, leading to stronger interactions with Pb(II) and pepsin.
Conclusions:
- Microbial colonization plays a critical role in modulating the exposure risks of pollutants associated with both artificial (MPs) and natural (clay) particles.
- The bioaccessibility and toxicity of Pb(II) are reduced by microbial colonization, particularly on clay particles.
- Environmental risk assessments of microplastics may overestimate exposure risks compared to clay particles due to microbial interactions.
