The phrase "such contamination" refers to the presence of harmful substances or impurities that can make something dirty, polluted, or dangerous. Full definition
In order to avoid such contamination in breeding it is a good idea to have all mates tested through a simple blood test available through your veterinarian. (pitbullregistry.com)
Basic geology prevents such contamination from starting below ground. (popularmechanics.com)
The forensic scientists who testified dismissed such contamination as highly unlikely. (newscientist.com)