b'SENSE, NONSENSE AND SCIENCEBY: JOE SCHWARCZTHE HUMAN FACTOR - PEANUTS, TURKEYS AND CANCERS o, tell me, what is the relationshipBy the time Yamagiwa made his dis- was happening outside the laboratory between mouldy corn and Ottocovery, epidemiologists had realized thatas well. Epidemiological surveys con-Preminger\'s last movie? The filmsome occupations other than chimneyfirmed a high rate of liver cancer in areas we\'re talking about is The Human Factor,sweeps also were associated with higherof high aflatoxin exposure, particularly an adaptation of Graham Greene\'s 1978rates of certain cancers. By the 1930s theChina, where rice often is contaminated spy novel. In a nutshell, the story is aboutexistence of a link between certain indus- by moulds. As many as one in ten Chinese a suspected "mole" in the British Foreigntrial chemicals and cancer had becomeadults develop liver cancer. Studies in Office who is thought to be leaking infor- clear. Nobody, though, thought that foodAfrica confirmed the theory. Both in mation to the Russians. A decision iscould also be a factor. At least not untilKenya and Mozambique peanut meal is a taken to eliminate the traitor without any1960, when turkeys began to die on massstaple of the diet, but storage conditions adverse publicity by poisoning him. Ofon poultry farms in England. differ. Calculations show that in Kenya course, a poison that works swiftly wouldthe average daily intake of aflatoxins is raise suspicion, so a physician working for3.5 nanograms per kg of body weight (a the foreign office decides on aflatoxin B, ananogram is a billionth of a gram) while in chemical that triggers cancer of the liver.Mozambique it is 220 nanograms per kg. Pretty ingenious and at least in theory,The liver cancer incidence in Mozambique feasible!In North Americais thirteen times higher than in Kenya. Aflatoxins are naturally occurringIn North America stored grains toxins produced by moulds of the genusstored grains are routinely assayed for aflatoxins. For Aspergillus flavus, which can infect nutsare routinelycorn, a common method is to shine green-and grains, particularly corn when theseish-yellow light on the kernels which will are stored under warm, humid condi- assayed forthen fluoresce if they are contaminated tions. The aflatoxin story is an interestingwith Aspergillus. A fascinating new tech-one because these compounds were theaflatoxins. nique to detect the mould uses sound. first to be recognized as dietary carcino- Corn kernels are heated by infrared radi-gens. They were not the first carcinogensation and are then quickly cooled. Those to be identified; that honour goes to sub- that are contaminated make a different stances found in snuff. In 1761, John Hill,sound when they contract, and computer an English physician, noted that snuffanalysis of the frequencies produced can users were more likely to develop nasalWithin a few months, over 100,000determine the extent of contamination. If tumours. Then in 1775, Percival Potts, abirds perished from what came to be calledAspergillus is found, a laboratory analy-surgeon, discovered that chimney sweepsTurkey X Disease. When ducks andsis is carried out, and corn with aflatoxin had an unusually high incidence of skinpheasants began to die as well, scientistslevels greater than 20 parts per billion cancer on their scrotum. The sticky mate- looked for a common cause and found itis deemed unfit for consumption. Of rial inside chimneys, known as creosote,in the feed the birds were given. The tur- course, this does not mean that we have was the likely candidate. Researcherskeys, ducks and pheasants all had been fedno exposure because obviously not every began to explore this possibility by paint- on Brazilian peanut meal. Within a year,lot of every grain can be tested. Nobody ing creosote on the skin of animals to seethe culprit was identified as the mouldknows how many cases of liver cancer in if tumours could be induced. For aboutAspergillus flavus, which produced theNorth America may be attributed to afla-150 years these experiments went on spo- appropriately named aflatoxins. toxins. Judging by a fascinating case of radically and unsuccessfully. The turkey episode raised questionsattempted suicide, probably not many. A ThenalongcameKatsusabur about a potential risk to humans whoyoung American woman tried to kill her-Yamagiwa, a medical researcher in Japan.consumed aflatoxin contaminated food.self by ingesting 5.5 mg of aflatoxin B (a He had something that apparently hisThe concern became very real when ithigh dose) that she had stolen from a lab-predecessors in this research area didbecame apparent that crops damagedoratory. Nothing happened. Six months not have. Patience. Yamagiwa carefullyby drought, not an unusual occurrence,later, she tried again with a total of 35 painted the ears of 137 rabbits every daywere particularly prone to contamination.mgs over two weeks. Again, nothing. She for over a year. Finally, tumours beganAnd the red flag was raised high whenthen decided life was worth living after to appear on seven of the rabbits. Thislaboratory studies showed that aflatox- all, and 14 years later she was still well could not happen by chance; Yamagiwains could induce cancer. It didnt takewith no liver problems. Oh well, it worked had found a carcinogen. long for scientists to discover that thisin The Human Factor. EUROPEAN-SEED.COMIEUROPEAN SEED I 31'