disorders of nutrition
Food Additives and Contaminants
Contaminants
Foods may be contaminated because the air, water, and soil are polluted, for example, by heavy metals (such as lead, cadmium, and mercury) or PCBs (polychlorinated biphenyls). PCBs used to be used as coolants and in many other products and are now present in the air, soil, and water in many places. Foods may be contaminated by pesticides or packaging materials or during cooking or processing. In addition, so-called endocrine-disrupting chemicals in the environment (such as some insecticides, petrochemicals, and industrial solvents) can affect the body's endocrine system and alter hormone levels, causing alterations in sex organs, immune function, nervous system function, growth and development, and certain cancers; they may also promote obesity. Foods may also be contaminated by drugs (such as antibiotics and growth hormone) that are given to animals. Sometimes limited amounts of contaminants are allowed in foods because the contaminants cannot be completely eliminated without damaging the foods. Common contaminants include Pesticides Heavy metals Nitrates (in green leafy vegetables) Aflatoxins, produced by molds (in nuts and milk) Growth-promoting hormones (in dairy products and meat) Levels that have not caused illness or other problems in people are considered safe. However, determining whether a small amount of a contaminant has caused a problem is very difficult. Thus, safe levels are often determined by general agreement rather than by hard evidence. Whether problems can result from consuming a small amount of some contaminants over a long time is unclear, although with very tiny amounts, such problems are unlikely. Foods may contain animal hairs, animal feces, and insect parts in such tiny amounts that removal is impossible. 