Its tempting to use the English word contamination, but in some contexts, pollution is more appropriate. The following paper gives a useful definition. According to this paper, the difference between pollution and contamination is;
“Contamination is simply the presence of a substance where it should not be or at concentrations above background. Pollution is contamination that results in or can result in adverse biological effects to resident communities. All pollutants are contaminants, but not all contaminants are pollutants.“
https://www.ncbi.nlm.nih.gov/m/pubmed/17027966/