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Abstract: Increasing attention is being given to the question of the real or apparent safety of foodstuffs at least in the United States. The attention is directed both by government and many private consumer groups. Ignorance of potential problem areas can well have serious economic consequences to inadequately informed and prepared industries, as was vividly exemplified following the recent revelations concerning excess mercury in certain seafoods. Since mushrooms are associated with affluent and well informed classes of people, and comprise a relatively limited market, they would be particularly liable to adverse publicity. At I.M.P. we have implemented a study on translocation and bioconcentration by mushrooms (Agaricus bisporus) of toxicologically significant elements and organic compounds. Since our continuing success depends on a vigorous mushroom industry, we are clearly concerned with all topics implicating safety and health. Although tentative, the little work to date has produced some noteworthy items which clearly call for additional study. Thus we find mushrooms have relatively high levels of certain metals (chromium, copper) but not others (mercury). Also, mushrooms translocate and may concentrate synthetic organic compounds as the PCB's (Arochlors), chlorinated hydrocarbons and organo-phosphate pesticides. Lindane was demonstrated earlier by Willems and Martens (1965) to be transferred from casing to mushrooms. Neilsen and Rasmussen (1952), using isotopes in a fine series of experiments, showed phosphorus to be translocated over distances of nearly two metres between spawning and third flush. Our interest in aflatoxins stemmed from the favourable economics of purchasing contaminated cottonseed and peanut meals in southern California. The situation provides well accepted high protein supplements at about one-half cost of the normal product, since they cannot be used for animal feeding. Aflatoxins are produced by various strains of the mold Aspergillus flavus when grown on high protein oilstock seeds and nuts under conditions of high heat and moisture. They were first described from England as the agents responsible for Turkey 'X' disease. Four natural forms are produced: B1, B2, G1 and G2 (Goldblatt, 1969). Aflatoxin Bj, the best studied, is the most potent known hepatocarcinogen in rats (Butler, 1965). At the molecular level, the toxin appears to act by suppressing messenger ribonucleic acid (RNA) synthesis. Some studies indicate the toxin also binds with DNA, inhibiting synthesis (Ciegler and Lillehou, 1968). The U.S. Food and Drug Administration has consequently established that foodstuffs can show no evidence of aflatoxin, and feeds are limited to 20 parts per billion (ppb). Any evidence of transfer of the toxin to, and/or toxic concentration in mushrooms, would preclude use of contaminated meals. Dialogues with FDA chemists indicated definitive experiments would be in order. An early experiment was conducted in late 1969 at California Mushroom Farms and involved peanut meal containing 300 ppb Aflatoxin B1 and 75 ppb aflatoxin B2. Supplementation of compost prior to phase II with amounts up to 1 lb contaminated meal per sq ft were attempted. Only treatments of less than 3/4 lb per sq ft prevented timely ammonification. One treatment was supplemented again at spawning to give a total of 1.5 lb meal per sq ft. Data indicated that between 35 and 60% of the aflatoxin was lost during phase II, none survived in the compost to the time of the first sample taken at the second break, and none was recovered from mushrooms between the second and fifth breaks.
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