Cadmium contamination threatens agricultural productivity and food safety worldwide. At the same time, microplastics are becoming increasingly common in farmland soils. A new global meta-analysis shows that when these two pollutants occur together, microplastics can sometimes reduce the harmful effects of cadmium on plants by limiting its uptake and movement through plant tissues.
The study, published in New Contaminants, analyzed 4,243 paired observations from 60 peer-reviewed studies involving major crops and other plant species. The researchers compared plant responses under cadmium exposure alone, microplastic exposure alone, and combined exposure to both contaminants.
"Our findings show that microplastics do not simply add another layer of toxicity. In many cases, they change how cadmium behaves in the soil and how much of it reaches plant tissues," said corresponding author Wei Wu. "However, this apparent protective effect should not be interpreted as evidence that microplastics are harmless. Their influence varies greatly with particle properties and environmental conditions."
Across the analyzed studies, cadmium exposure alone reduced plant biomass by approximately 29 percent, photosynthetic performance by 28 percent, and protein content by 49 percent. It also increased oxidative damage by 191 percent and raised cadmium concentrations in plant tissues by as much as 12-fold.
When plants were exposed to both cadmium and microplastics, these effects were generally less severe. Biomass declined by about 21 percent, photosynthetic activity decreased by 24 percent, and oxidative damage increased by 92 percent. Cadmium accumulation also rose less sharply, reaching about 3.8 times the level found in uncontaminated plants.
The researchers identified two possible mechanisms behind this pattern. First, microplastic surfaces can adsorb cadmium ions through electrostatic attraction, complexation, and ion exchange. This process may reduce the amount of freely available cadmium in soil water. Second, microplastic particles can form physical barriers near root surfaces, restricting direct contact between cadmium and plant roots and limiting its movement from roots to shoots.
The analysis found that cadmium alone increased root accumulation by 19-fold and shoot accumulation by 5.6-fold. Under combined exposure, these increases were limited to 4.5-fold in roots and 1.6-fold in shoots.
The effects were strongly dependent on microplastic size, polymer type, concentration, exposure duration, growth medium, and pH. Smaller particles generally caused stronger physiological stress than larger particles. Polymer types also behaved differently, with some plastics reducing cadmium availability more effectively than others. Alkaline conditions further limited cadmium uptake, probably because they promoted metal precipitation and strengthened interactions between cadmium and microplastic surfaces.
The study also revealed important trade-offs. Although microplastics often reduced cadmium accumulation and oxidative stress, they could disrupt the uptake of essential nutrients such as iron, manganese, magnesium, phosphorus, and potassium. Combined exposure therefore may protect plants from one form of stress while creating additional nutritional challenges.
"Risk assessments should consider contaminant mixtures rather than evaluating cadmium and microplastics separately," Wu said. "Understanding when microplastics reduce or intensify metal toxicity will be essential for designing effective soil management strategies."
The findings provide a broad evidence base for evaluating agricultural soils contaminated by both plastics and heavy metals. They may also help guide future research and support more targeted approaches to protecting crop productivity and food security.
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Journal reference: Azeem I, Shi Z, Xiong L, Ullah J, Shah F, et al. 2026. Microplastic-mediated modulation of Cd toxicity: evidence from a global meta-analysis. New Contaminants 2: e016 doi: 10.48130/newcontam-0026-0013
https://www.maxapress.com/article/doi/10.48130/newcontam-0026-0013
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About the Journal:
New Contaminants (e-ISSN 3069-7603) is an open-access journal focusing on research related to emerging pollutants and their remediation.
