Geomedicine is the science dealing with the influence of natural factors on the geographical distribution of problems in human and veterinary medicine. Discussions on potential harmful impacts on human and animal health related to soil chemistry are frequently focused on soil pollution. However, problems related to natural excess or deficiency of chemical substances may be even more important in a global perspective. Particularly problems related to
trace element deficiencies in
soils have been frequently reported in agricultural crops as well as in livestock. Deficiencies in plants are often observed for
boron,
copper,
manganese,
molybdenum, and
zinc. In animals deficiency problems related to
cobalt,
copper,
iodine,
manganese, and
selenium are well known. Toxicity problems in animals exposed to excess intake have also been reported, e.g., for
copper,
fluorine, and
selenium. Humans are similar to mammals in their relations to
trace elements and thus likely to develop corresponding problems as observed in domestic animals if their supply of food is local and dependent on
soils providing
trace element imbalances in food crops. In large parts of Africa, Asia, and Latin America, people depend on locally grown food, and geomedical problems are common in these parts of the world. Well-known examples are
Keshan disease in China associated with
selenium deficiency, large-scale
arsenic poisoning in Bangladesh and adjacent parts of India, and
iodine deficiency disorders in many countries. Not all essential elements are derived only from the soil minerals. Some
trace elements such as
boron,
iodine, and
selenium are supplied in significant amounts to
soils by atmospheric transport from the marine environment, and deficiency problems associated with these elements are therefore generally less common in coastal areas than farther inland. For example,
iodine deficiency disorders in humans are most common in areas situated far from the ocean. There is still a great need for further research on geomedical problems.