Contamination by chemicals or other toxins is the final source of foodborne illnesses after bacteria, viruses, parasites, and mold. Food and Drug Administration lists chemical contaminants, metals, natural toxins, and pesticides as the primary causes of non-pathogenic foodborne illnesses. Natural toxins are generally a byproduct of food processing techniques, and do not include toxins associated with inherently poisonous foods, such as some species of mushrooms or fish. Allergies are immunological conditions that are triggered by allergens, but allergic reactions are not considered a foodborne illness. Detergent is considered a chemical contaminant. While detergent is often used in dishwashers and at the pot washing station, when it comes to consuming food, having a chemical detergent present in the food is certainly an example of a chemical hazard. Glycerol, also known as glycerine or propanetriol, is a non-toxic artificial sweetener, so it is not a contaminant.
Unwashed vegetables may have residual pesticides on them, but they are more likely to harbor biological contaminants such as disease. The level of water activity required for microbial growth is 0.85.