In the last decades plastic pollution has become a universal problem. A lot of focus has been on the marine environment so far. Now there is a shift also to other environments like soil. Contamination of soil has become a global environmental threat that immensely affects terrestrial organisms as well as soil properties. Biodegradable, sometimes bio-based, materials have been proposed as a solution to this problem. However, often the biodegradation process of these polymers is still poorly understood along with the ecotoxicological effects they can have on organisms. Soil is a vital part of our ecosystem as well as the substrate on which other organisms get direct nourishment from and reside. Earthworms are an important component of the soil invertebrate fauna and hence they play a crucial role in soil ecotoxicological studies. However, the selection of appropriate test set up, execution & reproducibility of these tests plus the interpretation of results needs to be thoroughly thought through in order not to come up with false assumptions.