The use of plastics is increasing globally, and recycling is considered key to conserving resources and closing the material cycle. During recycling, the structure of the polymer may be damaged. Plastic can be composed of various polymers and contain various substances that are added to improve the properties of the plastic (additives). Certain substances can migrate from recycled plastic into the aqueous medium, such as metals that are an integral part of additives. The aim of the work is to examine the differences in the properties of PP (polypropylene) plastic during the recycling process. Recycling was carried out in an extruder, by mechanical recycling of PP with additional intentional contamination of the sample in different recycling cycles. The change in the polymer structure by increasing the number of recycling cycles was monitored by particle size distribution and DSC analysis (differential scanning calorimetry). Concentration of metals that comes out of the structure of recycled plastics and ends up in the water medium was determined by ICP-MS analysis (inductively coupled plasma with mass spectroscopy) and socalled metal migration tests. The analysis determined the concentrations of the following metals Sb, Ca, Mg, Na, K, V, Ga, Rb, Sr, Ag, Sn, Pb, Cd, Cr, As, Ni, Mn, Zn, Al, Ba, Co, Cu, Fe and Li. In order to get a broader picture of the potentially negative effect of recycling, the samples after the metal migration test were subjected to ecotoxicity and biodegradability tests. Ecotoxicity was tested on two types of organisms: the freshwater daphnia Daphnia Magna and the marine bacterium Vibrio Fischeri. Biodegradability was determined using COD (chemical oxygen demand) and BOD5 (biochemical oxygen demand in 5 days) tests. After the analysis, it was determined that the PP structure was damaged by increasing the recycling cycle. Based on the results on the distribution of particle sizes, an increase in the brittleness of the material was determined, while the DSC analysis showed an increase in the proportion of the crystalline phase. Tests of metal migration from the sample determined a lower concentration of migrated metals with an increased number of recycling cycles due to the incorporation of metals into the polymer structure. The ecotoxicity of water samples after the process of testing the migration of metals from recycled samples increases with the number of recycling cycles, while the biodegradability decreases with increasing recycling cycles.