Contamination is the presence of an unwanted foreign substance
or material (a contaminant) in the body, food supply, physical
environment or natural environment. Contaminants range from
toxins, pathogens and poisons to pollutants and radioactive
waste. In the natural environment, contamination can occur in
land (groundwater), air (pollution) and sea. In the body,
pathogenic contaminants include viruses, bacteria, toxins, and
radiation, etc. (Photo: Shutterstock)