Meta-analysis reveals the combined effects of microplastics and heavy metal on plants

The combined pollution of microplastics and heavy metals is becoming increasingly serious, and its effects on toxicology and heavy metal accumulation of plants are closely related to crop yield and population health. Here, we collected 57 studies to investigate the effect of microplastics on heavy metal accumulation in plants and their combined toxicity. An assessment was conducted to discover the primary pollutant responsible for the toxicity of combined pollution on plants. The study examined the influence of microplastic characteristics, heavy metal characteristics, and experimental methods on this pollutant. The results showed that combined toxicity of plants was more similar to heavy metals, whereas microplastics interacted with heavy metals mainly by inducing oxidative stress damage. Culture environment, heavy metal type, experimental duration, microplastic concentration and microplastic size were the main factors affecting heavy metal accumulation in plants. There was a negative correlation between experimental duration, microplastic concentration and microplastic size with heavy metal accumulation in plants. The interactions among influencing factors were found, and microplastic biodegradation was the core factor of the strong interaction. These results provided comprehensive insights and guiding strategies for environmental and public health risks caused by the combined pollution of microplastics and heavy metals. Because plants can transmit accumulated contaminants via the food chain, it is necessary to research the effects of microplastic and heavy metal pollution on phytotoxicity. However, the results of previous studies in this field appear to be contradictory. This study employed meta-analysis to comprehensively investigate the effects of combined pollution of microplastics and heavy metals on plants, identify the primary influencing factors and assess whether there was interaction. This will help to evaluate the potential environmental risks caused by their combined pollution and has certain reference value for the development of MPs pollution management measures and remediation technologies.