Negative impacts of synthetic nano-objects on soil biota and the need for global attention

Abstract Man-made synthetic/manufactured nano-objects (MNOs) are increasingly used in almost every scientific sector, including pharmaceutical, agricultural, food, and drug industries worldwide. Rapid advances in nanotechnology have led to the widespread application of MNOs (1–100 nm) in daily life; however, their potential toxic effects on living organisms have recently gained attention. When MNOs are released into soil through natural or anthropogenic activities particularly from agricultural practices involving nano-weedicides, nano-pesticides, and nano-fertilizers they can negatively influence soil biota and soil microbial communities. Soil organisms, such as earthworms, play a crucial role in soil structure, carbon stabilization, bio-magnification of pollutants, and regulation of microbial communities, while soil microbes contribute to nutrient cycling and crop productivity. Although soil bio-communities maintain ecosystem stability through organic matter decomposition and nutrient recycling, the incorporation of MNOs into soil can adversely affect these essential processes. This review summarizes the toxic effects of various MNOs, including silver, multi-walled carbon nano-tubes, copper oxide, and graphene oxide. The release of these MNOs into soil alters the normal physiological functions of earthworms, nematodes, plants, microbes, and plant–microbe symbiotic systems such as rhizosphere bacteria and mycorrhizal fungi. MNOs can attach to and enter host cells through cell membranes or cell walls, interfering with key biosynthetic organelles such as mitochondria, nuclei, and plastids. Consequently, MNO exposure induces excessive production of reactive oxygen species and other free radicals, leading to cellular dysfunction, reduced crop productivity, and, in severe cases, the death of soil microbiota. Therefore, the establishment of specific rules and regulations is urgently needed to manage the environmental risks associated with the increasing use of MNOs worldwide.