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URL 05414 f-M S*+4 THE SCIENCE OF THE POSSIBLE Paul B. Weisz Selenium: Another window to reality When I emerged from Penn Station, Madison Square Garden's billboard caught my eye: "Zeromania." Was this an apt characterization of our society--the clamor for having the risks of our world reduced to ZERO, chiefly by others (e.g., government)? You know, there's a popular illusion that risks can, in fact, be reduced to zero. 0.1 1 10 ___ 1______ 1__ -- ____10i * 10* 10* ____ i______i -- 10* ^gi'dey -- 1 1 1 1 11 .001 0.01 0.1 1.0 10 r -J--------100 ppm I stepped out on Eighth Avenue to the sound of a police siren, and ventured, an unnerving taxi ride to my hotel Then Deficiency Toxicity I went to the restaurant and ordered lobster. The service was Deeth(?) Death r slow. I drank a glass of water. I found paper and began to scribble. (1 had been reading about toxicity (J, 2).) Figure 1. The window of selenium intake. Upper scale: Total daily Intake by man. Lower scale: Average selenium Let's see, if the water I had drunk contained the average content of food taken by Other mammals. level of trace elements of natural fresh waters in the U.S. (0.02 ppm) (3), then I ingested some 30 quadrillion atoms of selenium, about 2 pg, and "everybody knows that selenium is toxic." (Actually, the standards for drinking 300 ft^/day of selenium, amounts below that magnitude can have serious consequences (10). For example, in China's water set by man are less than 0.01 ppm), so 1 probably took Szechuan Province a juvenile heart deficiency called in only 10 quadrillion atoms.) Keshan's disease is associated with the exceptionally low Now, I have drunk this planet's water all my life. I am a selenium intake in that locality (11). member of a species that evolved through millions of years The story of selenium demonstrates the fallacy of seeking < of adaptation to this earth's environment, including its a "zero" in the exposure to a chemical or physical parameter. natural waters. Common sense dictates that something is Intake of selenium appears undesirable, if not unacceptable, wrong with poorly qualified statements about toxicity--or below as well as above certain finite values. Figure 1 pictures any othqr "evil" property--of a natural substance that has the selenium window of our real world. been consumed by people for eons. The story of selenium The National Research Council's "safe and adequate" research, with its periods of darkness, brightness, confusion, intake of selenium, 50-200per day (12), lies in the range and surprise, provides an excellent insight into that of typical exposure on earth (13). That makes good sense, common-sense thesis. as 1 bad guessed from my evolutionary heritage. ..Selenium is ubiquitous. Bread contains typically 0.4-0.5 Before I knew it my lobster dinner had arrived, and ppm (4), garlic 0.9 ppm (5). one of the finest edible though I enjoyed it I realized that I'd just consumed about mushrooms, Boletus edulis, about 17.8 ppm (1). Yet 50 mg of arsenic (14). But I like crustaceans. Besides, I found selenium was labeled as a cancer hazard more rapidly than that "In rats, 5 ppm arsenic in the drinking water completely it could be proven to be one. prevents signs of selenosis" (15). The initial reports of carcinogenicity were followed by efforts by many researchers, and contradictory findings followed. Then, in 1976, the NAS reported that "Despite an Postscript: I called the promoter of "Zeromania." "What's Zeromania?" I asked. It's a pop group of singers and dancers whose leader is Renato Zero, I learned. initial report of selenium as a carcinogen, chronic experimental exposure of rats and mice to selenium salts over 'a period of 12 years has not induced neoplasia" (6). Meanwhile, a number of reports appeared that demonstrated in animal experiments that selenium had anti-carcinogenic activity, including correlations showing lower human cancer incidence the greater the selenium content in local vegetation, and therefore presumably in the diet for specific population groups (7,3). Whilst these winds were changing in cancer research, other rignlfleant developments arose in nutritional research. It was known that excessive intake of selenium by animals grazing on certain selenium-enriching plant species could lead to sdenoris, diseases known as blind staggers, and alWJi Reference* (1) Nelson. A. A. e( *1. Cancer Ret. 1943,5.20. (2) Shapiro, I. R. Ann. N Y. Acad. Sci. 1972,192,215. (3) Wither, C G. Clin. Toxic. 1980,17(2). 171. (4) "Toxicants Occurring Naturally in Foods"; National Academy of Sciences: Washington, 1973. (5) Goto,T.; Fujino, M. Ciyo To Shokuryo 1967,20(4), 311. (6) "Medical and Biological Effect of Environmental Pollutants, Selenium"; National Academy of Sciences: Washington, 1976. (7) Schrauxer. C. N.; McGinnest, j. E-; Kuehn, K. "Proc. InL Symp. Org. Selenium Tellurium Compounds," 1979, Vo). 3. (8) Janmm, B. Mel. Ions Biol. Syst. 1980,10. 281. (9) See Muth, O H.; Burns. W. Ann. N.Y. Acad. Sci. 1984, III,583. (10) Levander. O A. Ann. N Y. Acad. Sci. 1982,393,70. (11) Keshan Disease Research Croup. Chin. Med. ] 1979,92,471, 477. (12) Pechter. K Prevention 1982,34,55.* (13) G. Environ. Health Perspective* 1981.40,143. (14) Monies-Williams, G. W. 'Trace Elements in Foods"; Chapman and disease (9). But in the period from 1956 to 1963, it was shown that selenium not only had useful metabolic functions, it is Hall Ltd.: London, 1949. (15) Moaon, A. L. Science 1938,88. 81. a necessary trace element in nutrition. Paul B. Weiss, editor of this column, is senior scientist and science advisor. While most people benefit from dietary intake of 60 to Mobil RAD Corp., Princeton. N J. 08540; 600-737-3000. CHEMTECH JANUARY 1983 48 I- i