Contamination of food with inorganic contaminants, including the corresponding organometallic complexes. The most important contaminants are mercury, cadmium, and lead. The major types of food involved are cereal grains (bread, flour), meats (beef, pork, beef liver, canned meats, sausages), fish (canned salmon, shellfish, whitefish), dairy products (milk, cheese, butter), fruits, vegetables (fresh and canned), eggs (white and yolk), and beer. Fish and other seafoods are particularly affected, as the mercury in fish occurs in its most toxic form, the methyl form. Mercury can be observed in various forms: the elemental form (HgO), the inorganic or ionic form (Hg²+), or the organic complex form (R-Hg+). Elemental mercury can be oxidized to the inorganic form in the blood and other animal tissues, a process which is mediated by the enzyme catalase. Outside the body, such as in sediments, the oxidation can take place nonenzymatically in the presence of oxygen and organic matter. The formation of organic mercury (by methylation) can occur under a variety of conditions, both in environmental systems and in the animal body. Exposure to organic complexes of mercury, especially methylmercury, is more toxic than exposure to elemental or inorganic mercury. The clinical signs of methylmercury poisoning in humans include numbness and tingling of the extremities, mouth, and lips; loss of hearing and coordination; gross narrowing of the visual fields; reflex changes; progressive psychologic and mental deterioration; sweating and salivation; and muscle fasciculation and atrophy. The total daily intake of mercury per individual in the United States and in Western Europe is estimated at 1-20 mg. The tolerable weekly intake is 300 mg, of which not more than 200 mg should be in the form of methylmercury.
Substances that are included unintentionally in foods.
The presence, introduction, or development of infectious or toxic material in food. Food may be contaminated by bacteria (Salmonella , E. coli, Listeria), viruses (hepatitis A, Norwalk), protozoa (Giardia), worms (tapeworms and roundworms), molds (Aspergillus), or toxins (botulinum, staphylococcal enterotoxin).