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Population Cytogenetics: Studies in Humans

mutagenic drugs are valuable and no one wishes to ban them. There is, however, a general consensus among genetic toxicologists that their use ought to be restricted to situations where the benefit can be seen to justify the risk. This could lead in certain instances to an erosion of the practitioner's right to prescribe, in principle not necessarily a bad thing as the untoward consequences of mutagenic action are not confined only to the treated individual-for example induction ofneoplasms-but may contribute toward the genetic burden of the whole population. In order to make a proper (as distinct from subjective) risk-benefit evaluation it is necessary to obtain an estimate ofrisk that is quantitative even ifapproximate. Despite the fact that screening tests for mutagens are well developed, the estimation of risk is still a relatively unexplored area. Liane Brauch Russell, in a chapter on numerical sex chromosome anomalies in mammals, discusses approaches that may well be useful in the assessment of genetic risk. Another factor in the evaluation of genetic risk is the study of effects in man-in particular, visible chromosomal effects. While the biological consequence of chromosome aberrations in the somatic cells of man is uncertain, their presence may be used to indicate the action within the body of genetically active agents. When applied to an industrial situation, cytogenetic analysis may be used to monitor the effectiveness of hygiene procedures in preventing exposure ofworkers who could come into contact with mutagens. It may also be used to detect the existence of a possible hazard previously unsuspected. A few of the larger chemical companies are now carrying out regular cytogenetic monitoring of their labour force. This represents a major commitment for any company, as may be seen in the chapter by Kilian and Picciano of the Dow Chemical Company. The volume also contains a lucid and concise survey by Evans ofcurrently available cytological techniques for mutagen detection along with a more detailed discussion by Schmid of the micronucleus method. Completing the volume is a characteristically encyclopaedic survey of atmosphere mutagens by Fishbein, and excellent reviews on the use in genetic toxicology testing of the fruit fly Drosophila and of plant systems by Vogel and Sobels and by Nilan and Vig, respectively. B. A. BRIDGES