MUTAGENS OF POTENTIAL SIGNIFICANCE 195 



TABLE 3 



Category III : Drugs and other chemicals to which a large part 

 of the population is exposed for long periods of time. 



Ethyl alcohol. 



Nicotine. 



Water additives: chlorine, fluoride. 



Foods and food additives. 



Insecticides. 



Industrial air pollutants. 



Vitamins and trace metals. 



Contraceptive jellies and creams. 



Oral contraceptive: norethynodrel. 



Caffeine and theobromine. 



The first compound in this category is ethyl alcohol. At 0.5 M in the 

 Alliurn test it produces abnormality in 50 per cent of all metaphase 

 figures (6) . Ethyl alcohol is a drug to which the human race has long 

 been exposed, and to which individuals are exposed at irregular inter- 

 vals throughout adult life. The concentrations established in the body 

 are considerable. Very minor intoxicating effects occur at a blood level 

 of about 1 mg/ml (0.02 M). The lethal concentration is around 5 

 mg/ml. Chronic exposure will differ significantly between wine- (or 

 beer-) drinking countries and others. Ethyl alcohol is metabolized 

 through acetaldehyde, and whenever ethyl alcohol is present there is 

 also a small but measurable level of acetaldehyde. This raises again 

 the question of mutagenicity of aldehydes. A recent report (40) indi- 

 cates that in mammals, including man, ethyl alcohol is present as a 

 product of normal metabolism at about 1 mM. This endogenous level 

 is so low compared with exposure levels in drinkers, it can probably be 

 neglected. 



Nicotine is a drug to which there is very widespread exposure. There 

 are figures, of course, on the number of cigarette smokers and the 

 amount of nicotine that is absorbed. I think you probably all know 

 that the total amount of nicotine contained in a cigarette is in the 

 lethal range. It was once said that nicotine is so toxic that one drop on 

 the tip of a cat's tail would kill a man. 



Nicotine is usually absorbed in the amount of approximately 1 mg 

 per cigarette, but sometimes much more, depending on the way a per- 

 son smokes and whether he inhales deeply (54). There is certainly 

 a circulating blood level of nicotine during smoking, and, in fact, if 

 there were not a circulating blood level whereby nicotine reaches the 

 brain, people who smoke for psychic pleasure would not smoke. 



