IT'S ELEMENTAL!

SELENIUM LIU TUNGSHENG, CHINESE ACADEMY OF SCIENCES, BEIJING

IN I 9 3 5 , A TERRIBLE DISEASE WAS

spreading wantonly in some rural ar­eas of Heilongjiang province in north­eastern China. Women of childbear-ing age and children were its primary

victims. Particularly cruel, the disease fre­quently occurred without warn­ing and led to the death of a large number of people. At the time, nobody understood the cause of this disease, so it was called "Ke­shan disease" because it was first reported in Keshan County of Heilongjiang province. Today, Keshan disease is known to be an endemic myocardial disease. It still occurs in some rural areas.

The idea that environmental selenium deficiency could be the cause of Keshan disease came about as the result of the discovery of a special ecolog­ical phenomenon in the Keshan disease re­gion. In the summer of 1967, my colleagues and I went to Heilongjiang province to in­vestigate the geological and geochemical environment of the disease districts. We were surprised to learn that local residents

0ELE8&ATIN0 C&Stt'S

80TH ANJtiVEftSARY

E P ID E MIC Map of the distribution of Keshan disease on the Chinese mainland, showing a belt crossing the country from the northeast to the southwest.

believed that Keshan disease was coming from the local water and soil, because, they reasoned, a person could avoid the disease by moving from the disease district to an­other place. In particular, we were told by a local veterinarian that sheep in the dis­ease district were contracting white mus­cle disease. The main pathological change for white muscle disease is injury of the

sheep's heart. This was noted as similar to the pathological changes seen in Keshan disease patients. The cause of the white muscle disease was attributed to selenium deficiency in the environment. And, in­deed, by adding appropriate selenium in

the form of Na2Se03, white muscle disease can be treated and prevented in sheep. So we had a clue for investigating Ke­shan disease in humans.

For the next 10 years, Chinese scientists studied Keshan disease in three ways. First, they used fluorospectrophotometry with 2,3-diaminonaphthalene to de­termine trace levels of selenium. Simultaneously, a multidiscipli-nary research team consisting of

both Earth and medical scientists was es­tablished and studied environmental geol­ogy, geochemistry, geography, hydrology, soil science, epidemiology, nutrition, and pathology The investigation plan was based on a unique geo-ecological phenomenon that I had previously discovered, that is, that Keshan disease has a distribution that

forms a belt crossing China from northeast to southwest. The belt region is a transitional area from the eastern plane, which has a wet­ter climate, to the west­ern mountains, which are drier and where weathering and leach­ing actions are strong and both loss of water and soil erosion are se­rious problems.

Aresearch team took samples of rock, soil, water, and staple food grains (corn, wheat, mil­let, and so on). Human hair specimens were ob­

tained from people who lived in the disease districts and in the nondisease districts. A number of chemical components, includ­ing selenium and more than 10 other trace elements, as well as some organic com­pounds, were analyzed. The data indicated that the concentrations of selenium are low­er in the disease-district samples.

So we suggested that adding selenium to

SELENIUM AT A GLANCE Name: From the Greek setene, moon-Atomic mass: 78.96. History: Discovered in 1817 by Swedish chemist Jons Jakob Berzelius after an­alyzing an impurity that was contami­nating the sulfuric acid being produced at a factory in Sweden. _ _ Occurrence: Occurs naturally in the rare minerals eucairite, crooksite, and clausthalite. Obtained commercially as a by-product of copper refining. Appearance: Exists as two atlotropes: red and gray. Red selenium, the less stable of the two, is an amorphous pow-der; gray selenium is a silvery metal. Behavior: Burns in air, but is unaffect­ed by water. Although ordinarily a poor conductor of electricity, gray selenium is a photoconductor, meaning it be­comes an excellent conductor in the presence of light. Uses: Used In photoelectric cells, pho­tocopiers, solar cells, and semiconduc­tors. Because it is a powerful photo-conductor, gray selenium is valuable as a light sensor and is used in robot­ics, light-switching devices, and light meters. Compounds containing seleni­um are useful in controlling dandruff and are often added to shampoos.

the diets of local residents could halt the spread of Keshan disease. Chinese med­ical scientists carried out a series of animal studies designed to determine the meta­bolic, toxicological, and biochemical char­acteristics of selenium supplementation. On the basis of the results of these stud­ies, residents of disease-prone districts took supplements of Na2Se03 under med­ical supervision. At the same time, a series of biochemical and environmental obser­vations were made. Ten years' worth of data show that taking Na2Se03 tablets is an effective measure for controlling the spread of Keshan disease.

While we still do not know for certain whether selenium deficiency is the only fac­tor leading to Keshan disease, it is certain­ly one of the most important factors. And we can also say that lack of selenium in the environment is potentially harmful to the health of humans and animals and is thus worth our attention.

Liu Tungsheng is a research professoratthe In­stitute of Geology & Geophysics, Chinese Acade­my of Sciences, Beijing. Hong Yelang, aprofes-sor at the Institute of Geochemistry, Chinese Academy of Sciences, contributed to this essay.

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