Tag-along toxics
Of the 112 chemical elements known to man, only 16 are essential to plants. Carbon, hydrogen and oxygen are taken from air and water. Nitrogen, phosphorus and potassium are primary nutrients in fertilizers. Ten others are secondary nutrients. Some fertilizers, especially those derived from recycled wastes, also contain the following chemicals of possible health concern - but they are never listed on the fertilizer label.
Lead
Can cause seizures, mental retardation and behavioral disorders. Most vulnerable crops are fruits and grains, mostly from contact with air but also through roots.
Cadmium
Has half-life in soil of 15 to 100 years. Long-term exposure may cause cancer, kidney disease, neurological dysfunction, diminished fertility, immune-system changes and birth defects. Crops most vulnerable are lettuce, corn, wheat and rice.
Arsenic
Comes from mine tailings and smelting residue. Highly toxic to animals; carcinogenic. Plants most vulnerable are root crops such as carrots, onions and potatoes.
The Environmental Protection Agency also has identified these metals as potential health concerns under its standards for land application of sewage sludge: chromium, copper, mercury, molybdenum, nickel, selenium and zinc.
Sources: Agency for Toxic Substances and Disease Registry, U.S. Public Health Service, Environmental Protection Agency
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