The introduction or occurrence of a contaminant in food or food environment.

Source: EUROSTAT

"contamination" means the presence or introduction of a hazard;

Source: EURO-Lex

Introduction into or onto water, air, soil or other media of microorganisms, chemicals, toxic substances, wastes, wastewater or other pollutants in a concentration that makes the medium unfit for its next intended use. 

Source: EEA Glossary