Food may be accidentally or deliberately contaminated by microbiological, chemical or physical hazards.
In contrast to microbiologically caused foodborne illness, the link between exposure and effect of chemical hazards in foods is usually complicated by cumulative low doses and the delay between exposure and the onset of symptoms.
Incidents have occurred because of poor harvesting or storage of grain, use of banned veterinary products, industrial discharges, human error and deliberate adulteration and fraud.
[1] Information on the impacts of these incidents is fragmentary and unsystematic, ranging from thousands of dollars to meet the cost of monitoring analysis, to many millions of dollars due to court prosecutions, bankruptcy, product disposal, compensation for revenue loss, damage to brand or reputation, or loss of life.
[1] In 2013, Professor Chris Elliott, Professor of Food Safety and Director of the Institute for Global Food Security at Queen's University Belfast, was asked by the UK's Secretaries of State for Defra and Health to undertake a review of the weaknesses within UK food supply networks and to suggest measures which might be taken to address these issues.