Assessment of soil microplastics: An overview on toxicity, effects on heavy metals adsorption, solid-phase extraction, and detection techniques

Terrestrial ecosystems face critical environmental challenges due to widespread of microplastic (MP) contamination, which has direct implications for human health. This review examines the sources, human exposure pathways and toxicity of MPs, with a specific focus on their role as vectors for heavy metals. Agricultural practices, such as plastic mulching and the use of sewage sludge, have made soils into dynamic reservoirs for MPs. These MPs cause significant physical, chemical and biological changes in the soil. However, accurately quantifying and analyzing MPs in complex soil matrices is a major challenge because of the lack of standardized methods, which hinders effective environmental monitoring. The review suggests that future progress depends on the adoption of advanced, repeatable analytical techniques such as solid-phase extraction (SPE) to overcome the limitations of traditional methods. This study also details how aged and weathered MPs act as reactive carriers for heavy metals, creating a new type of co-pollution with unpredictable effects. This co-pollution can alter soil properties and disrupt essential microbial communities. Growing evidence shows that MPs are now found in human blood, placenta and breast milk, raising concerns about long-term toxicological effects and potential harm across generations. The review further concludes with an urgent call for action, particularly the need for the scientific community to standardize analytical protocols, research complex copollutant dynamics, and advocate for policies that address the primary sources of soil MP pollution. Safeguarding the health of terrestrial systems requires the translation of scientific understanding into decisive action to protect the future of soil and food security.