Soils and terrestrial ecosystems have been widely ignored as part of the problem of environmental contamination with plastic wastes, even though this resource is likely the main source of microplastics to aquatic systems. In the last few years, several studies have been carried out on terrestrial ecosystems and some of them highlighted the potential negative impacts of small plastic wastes (microplastics and nanoplastics) on soil properties and soil biota. This chapter makes an overview of existing information and aims to demonstrate how scarce and limited it still is in order to give a clear idea of whether the soil ecosystem is really at risk. Realizable exposure assessments are constrained by extraction and analytical methodologies and effects assessment is restricted to a reduced number of species, a great variety of polymers, concentrations and exposure conditions, which globally provide few data for a quantitative risk assessment. However, and being aware of the difficulties to clean soils of all the plastic wastes (especially smaller particles) accumulated for decades, efforts should be concentrated on the risk assessment of biodegradable polymers and on specific regulations to control the use of these new polymers.