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Contrasting impacts of biodegradable and conventional microplastics on heavy metal bioavailability in soils: A multilevel meta-analysis
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"Biodegradable" plastics are often marketed as the eco-friendly alternative to regular plastic, but this study found they may actually make soil pollution worse: they caused toxic heavy metals like cadmium already lurking in soil to become more available for uptake by plants, by changing soil chemistry and microbial life. This matters because metals absorbed by crops can end up in our food, so switching to biodegradable plastics isn't automatically the safer choice, it may trade one environmental problem for another.
The substitution of conventional non-biodegradable plastics (NBMPs) with biodegradable plastics (BMPs) has been widely advocated as a strategy to alleviate plastic pollution. However, whether this transition alters the geochemical behavior of legacy heavy metals (HMs) in soils remains unclear. Here, using a global dataset, we systematically compared the effects of NBMPs and BMPs on HM bioavailability, chemical speciation, and microbial ecological functions through multilevel meta-analysis and random forest modeling. NBMPs had negligible effects on overall HM bioavailability and speciation, indicating limited interference with soil HM dynamics. In contrast, BMPs significantly increased HM bioavailability, particularly for cationic metals such as Cd, and promoted their transformation toward more labile, acid-extractable fractions, whereas As mobility decreased. These responses were accompanied by coordinated changes in soil chemistry and microbial communities, including pH decline, dissolved organic carbon enrichment, enhanced enzyme activities, reduced microbial diversity, and a shift toward copiotrophic r-strategy taxa. Random forest analysis further identified pH, dissolved organic carbon, and the r/K strategy ratio as the most important predictors of HM bioavailability. Our results demonstrate that the environmental sustainability of BMP substitution should be evaluated not only by degradability, but also by its potential to disrupt soil geochemical balance and amplify ecological risks associated with legacy HMs.
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Microplastic dilemma: Assessing the unexpected trade-offs between biodegradable and non-biodegradable forms on plant health, cadmium uptake, and sediment microbial ecology
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This study compared the environmental effects of biodegradable and conventional plastic microplastics in contaminated sediments, finding that biodegradable plastics actually caused more oxidative stress and greater changes to soil bacteria than conventional plastics. Both types helped plant roots absorb more of the toxic metal cadmium. The surprising finding that biodegradable plastics may pose higher ecological risks challenges the assumption that they are always a safer alternative.
Microplastics impair cadmium adsorption in soils via changes in dissolved organic matter and Fe/Mn oxides
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Microplastics in soil—especially the "biodegradable" and weathered kind—make it harder for soil to trap toxic cadmium, allowing more of it to move around freely instead of staying locked in place. This matters because cadmium is a harmful heavy metal that crops can absorb from soil, so more mobile cadmium could mean more of it ending up in the food we eat. The findings suggest that even "eco-friendly" plastics may create hidden risks by changing soil chemistry in ways that let contaminants spread more easily.
Biodegradable and conventional microplastics affect soil-plant systems through altering microbial community assembly and functions
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"Biodegradable" plastics are often marketed as the eco-friendly choice, but this study found that when they break down into microplastics in soil, they actually harm plant growth and soil health more than regular plastics like polyethylene do, by disrupting the soil bacteria that plants depend on for nutrients. This matters because these microplastics could end up in the crops we eat, and it suggests that switching to "biodegradable" plastics isn't automatically a safer bet for our food supply without more research into how they actually break down in real farm soil.
Effect of biodegradable microplastics and Cd co-pollution on Cd bioavailability and plastisphere in soil-plant system
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Researchers examined how biodegradable microplastics interact with cadmium contamination in agricultural soil where lettuce is grown. They found that the biodegradable plastics indirectly increased cadmium availability to plants by lowering soil pH and changing soil chemistry. The study suggests that even eco-friendly biodegradable plastics may worsen heavy metal contamination risks in farming soils.
PLA vs PE microplastics with cadmium: Time-dependent divergent and microbial disruption of soil carbon and nitrogen cycling in medicinal plant soils
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Scientists studying soil contaminated with both microplastics and cadmium (a toxic heavy metal) found that "biodegradable" plastic, when combined with cadmium, actually disrupted soil health more than regular plastic did—damaging the bacteria that plants like medicinal herbs rely on to get nutrients from soil. This matters because it challenges the common belief that biodegradable plastics are automatically better for the environment, suggesting that in polluted farmland, they could harm soil quality and potentially the safety or nutrient content of crops grown there.
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