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Oxidative stress and gene expression induced by biodegradable microplastics and imidacloprid in earthworms (Eisenia fetida) at environmentally relevant concentrations
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Researchers exposed earthworms to biodegradable microplastics made from polylactic acid (PLA), both alone and combined with a common pesticide. Both treatments caused oxidative stress and DNA damage, and the combined exposure was often more harmful than either pollutant alone. This study is important because it shows that even so-called biodegradable plastics can harm soil organisms and may interact with other agricultural chemicals to create greater environmental damage.
The environmental issues caused by biodegradable microplastics (BMPs) from polylactic acid (PLA) as well as pesticides are of increasing concern nowadays. In this study, the toxicological effects of the single and combined exposure of PLA BMPs and imidacloprid (IMI), a neonicotinoid insecticide, on earthworms (Eisenia fetida) were investigated in terms of oxidative stress, DNA damage, and gene expression, respectively. The results showed that compared with the control, SOD, CAT and AChE activities in the single and combined treatments decreased significantly, and POD activity showed an "inhibition-activation" trend. SOD and CAT activities of combined treatments on day 28 and AChE activity of combined treatment on day 21 were significantly higher than those of the single treatments. For the rest of the exposure period, SOD, CAT and AChE activities in the combined treatments were lower than those in the single treatments. POD activity in the combined treatment was significantly lower than those of single treatments at day 7 and higher than that of single treatments at day 28. MDA content showed an "inhibition-activation-inhibition" trend, and the ROS level and 8-OHdG content increased significantly in both the single and combined treatments. This shows that both single and combined treatments led to oxidative stress and DNA damage. ANN and HSP70 were expressed abnormally, while the SOD and CAT mRNA expression changes were generally consistent with the corresponding enzyme activities. The integrated biomarker response (IBR) values were higher under combined exposures than single exposures at both biochemical and molecular levels, indicating that combined treatment exacerbated the toxicity. However, the IBR value of the combined treatment decreased consistently at the time axis. Overall, our results suggest that PLA BMPs and IMI induce oxidative stress and gene expression in earthworms at environmentally relevant concentrations, thereby increasing the risk of earthworms.
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Exploring the toxicity of biodegradable microplastics and imidacloprid to earthworms (Eisenia fetida) from morphological and gut microbial perspectives
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Researchers found that biodegradable microplastics made from polylactic acid (PLA) combined with the pesticide imidacloprid caused more severe harm to earthworms than either pollutant alone, including higher death rates, tissue damage, and disrupted gut bacteria. This is concerning because PLA plastics are marketed as eco-friendly alternatives, yet they can still break down into harmful microplastics in soil. The study shows that biodegradable plastics may actually make pesticide contamination worse for soil organisms.
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Researchers investigated the combined toxic effects of the insecticide fosthiazate and microplastics on earthworms using both biochemical and genetic analyses. They found that co-exposure increased oxidative stress, DNA damage, and disrupted metabolic pathways more severely than either pollutant alone. The study suggests that microplastics may amplify pesticide toxicity in soil organisms, raising concerns about their combined impact on soil ecosystem health.
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Researchers examined the combined effects of mulch film-derived microplastics and the pesticide atrazine on earthworms over 28 days. They found that co-exposure caused greater oxidative stress than either pollutant alone, with aged microplastics from farmland residues producing more severe effects than unused film-derived particles. The study suggests that agricultural soils contaminated with both degraded mulch film microplastics and pesticides may pose compounding toxic risks to soil organisms.
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Researchers studied the combined effects of polyethylene microplastics and the pesticide carbendazim on earthworms and found that the two pollutants together caused worse damage than either alone. The combined exposure led to growth problems, oxidative stress, and organ damage even at lower concentrations. Since earthworms are essential for soil health and microplastics and pesticides commonly co-exist in farmland, these findings suggest that agricultural soil contamination could have cascading effects on the food system.
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