Effects of Microplastics on Bioavailability, Persistence and Toxicity of Plant Pesticides: An Agricultural Perspective

Microplastic–pesticide interactions influence pesticide performance, soil health, and environmental safety. This review aims to comprehensively present the effects of microplastic–pesticide interactions on pesticide bioavailability, persistence, and toxicity, along with their agricultural implications on pest control. It reviews more than 90 related articles from established scholarly databases. Most studies indicate that pesticide bioavailability decreases in the presence of microplastics due to adsorption, which is frequently influenced by the hydrophobicity (log Kow) of the pesticides and the surface area and type of microplastics. Higher log Kow results in higher adsorption and lower bioavailability. Aged microplastics have higher surface areas for adsorption, thus reducing pesticide bioavailability. This decreases the effectiveness of systematic and contact pesticides. Lower bioavailability leads to less adsorption of the former by plants to control pest infestation and less contact of the latter with pests in the soil to kill them directly. Higher pesticide adsorption also increases the persistence of pesticides, as indicated by their extended degradation half-lives. However, some studies demonstrate that biodegradable microplastics, especially the aged ones, have less effect on pesticide persistence because they release pesticides for degradation when they break down. Few studies on how microplastics alter pesticide toxicity on target organisms are available, but the available ones point to potentially higher toxicity on crops and beneficial soil organisms. Overall, the review highlights a significant negative effect of microplastics on pesticide bioavailability. This may prompt the application of more pesticides to achieve the desired level of crop protection, which bears cost and environmental consequences.