Residues reviews: Residues of pesticides and other contaminants in the total environment

Review Section REVIEWS

OF RECENT

Nasopharyngeal Carcinoma: Etiology and Control. Edited by G. de-The and Y. Ito. IARC Scientific Publications No. 20. International Agency for Research on Cancer, Lyon, 1978. pp. xvii + 610. Sw.fr. 100.00. Tumours with a high incidence in specific localities are frequently attributed to some environmental factor and it has often been claimed that an intensive study of their biology may provide a valuable insight into the aetiology of human tumours. The attention currently being paid to nasopharyngeal carcinoma is very much in line with such thinking. The incidence of this tumour is high in some Far Eastern countries, notably China, while in others, including Western Europe, it is very low indeed. Furthermore there are indications that certain ethnic groups are more prone than others to its development. The salient features of the research on this disfiguring and fatal form of cancer are presented in these proceedings of an international symposium held in Kyoto, Japan, 2 years ago. The venue for the symposium was particularly appropriate, since a major part of the research effort discussed at the symposium had apparently been carried out in Japan. The communications fell broadly into four main groups, dealing respectively with the histopathological appearances of nasopharyngeal carcinomas, the clinical course of the disease, epidemiological studies and investigations into the aetiology of the tumour. Most of the papers on histopathology were concerned with the definition of the controversial undifferentiated tumours called by some carcinoma and by others lymphoepithelioma. No fresh evidence seems to have been presented for settling this issue, although some serological typing techniques appear to hold promise for the future. The papers on the clinical aspects of the disease emphasized the difficulties of making an early diagnosis: the nasopharynx is surrounded by cranial nerves and by organs of the special senses and the first symptoms are usually referable to one of these rather than to the nasopharynx itself. An excellent account of the clinical course of this disease and its response to radiotherapy revealed that the rate of recurrence after treatment is disturbingly high and bears no clear relation to the histological type of the tumour. Epidemiological studies are being pursued with the aims of defining more clearly the geographical areas where the disease shows the greatest prevalence and of identifying the ethnic groups that seem to be most susceptible to it. The reports presented at the symposium indicated that, in areas of low incidence, epidemiologists were paying greater attention to the identification of certain groups showing an incidence of the tumour that was higher than expected in that particular community as a whole. There are indications that certain occupations offer a greater risk of 429

PUBLICATIONS

tumours of the nasal cavity than do other walks of life. Unfortunately the papers presented made no specific mention of any such occupations, although in view of previous claims that woodworkers appear to be at greater risk of developing this type of tumour than other workers, one might have expected greater attention to be given to the occupations that apparently carry such risk. Considerable attention was devoted to the possibility that a viral agent might be responsible for the development of nasopharyngeal carcinomas. In view of the prevalence of lymphoma-like tumours in the nasopharynx, the Epstein-Barr virus (EBV) has been suspected, presumably because of its connection with malignant lymphoma in some parts of Africa Detailed accounts of the quest for this virus were presented in many of the communications. Several techniques, including ultrastructural and serological studies and nucleic acid hybridization, have been used in the search. Unfortunately the fruits of these extensive-and expensive--efforts have been disappointing. Yet some workers still believe that a viral aetiology is the likely explanation, and the serological investigations have been widened to include a search for viruses other than EBV. It was disappointing to find that the symposium participants had paid so little attention to the possibility of chemical induction of nasopharyngeal carcinoma. Many chemicals can induce this tumour in rodents, not only when inhaled but also when administered by the oral or parenteral routes, and a discussion of relevant studies would have added considerably to the value of this book. In fact, only two out of some forty communications were devoted to chemical induction of the tumour and the fields selected were so narrow and the experimental designs so poor that they make little impact. On the whole the book is aimed at those seeking to understand the nature and epidemiology of the human disease. There is little in it for those involved in occupational medicine or for the scientist working in the field of chemical carcinogenesis. Residue Reviews: Residues of Pesticides and Other Contaminants in the Total Environment. Vol. 69. Edited by F. A. Gunther. Springer-Verlag. New York, 1978. pp. viii + 146. 822.00. Residues Reviews: Residues of Pesticides and Other Contaminants in the Total Environment. Vol. 70. Edited by F. A. Gunther. Springer-Verlag, New York, 1979. pp. viii + 144. $21.80. Volume 69 of Residue Reviews opens with a survey of the physico-chemical interactions of parathion with soils. A-picture is built up of the fate of this organo-

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Reviews of recent publications-Ftl

phosphorus pesticide, which is used to control both plant- and soil-borne insects, and of the speed (or relative slowness) of its degradation. The non-toxic metabolites formed by hydrolysis of the phosphate ester bond tend to be retained by the soil colloids. For many years, toxaphene has been the most heavily used pesticide in the USA, but its importance has not been reflected in the frequency of its appearances in the literature. In recent years, however, research on toxaphene has intensified, and now two US academics, seeking to remedy the literary neglect, have reviewed the available data. Surveying its acute. subacute and chronic toxicity in various species, including man, they conclude that while toxaphene shows, in most animals, an intermediate level of toxicity when compared with other organochlorine pesticides, it is extremely toxic to fish. Data on its biodegradability and on the persistence of its residues in crops, animal tissues and milk present a confusing picture, largely because of the analytical problems presented by a substance said to be a mixture of at least 177 separate components. For the same reason, metabolic studies are still at a very early stage. All in all, the impression remains that here is a fruitful field for study, the success of which will depend on the development of more discriminating and sensitive analytical methods and on the careful recording of all known details about any test samples used, particularly the method of preparation and the toxaphene detection limits of the analytical methods. These two pesticide contributions are separated by a review of the occurrence of polycyclic aromatic hydrocarbons (PAH) in food and their possible significance in terms of human health. This wide-ranging survey considers the types of food in which PAH have been found and identifies 11 that have been shown to be carcinogenic in experimental animals out of the total of 22 detected in foods. Lengthy tables detail the carcinogenicity findings on these 11 compounds and provide other evidence in support of the text. Consideration is also given to the many metabolites of the PAH, including the K-region epoxides. Ideas that the high incidence of stomach cancer in some areas may be related to a high consumption of smoked fish or meat are aired in this review, but the authors conclude that, with this possible exception, there is no epidemiological evidence to link the PAH in foods with any specific human disease. The next issue in this series carries the bright red cover indicating the cumulative indexes for the latest ten volumes. Accompanying these indexes are a survey of chemical, physical and biological methods for the disposal and detoxication of pesticides and a step by-step outline of the field studies necessary to establish safe re-entry intervals after the application of organophosphates to crops. The volume also contains a discussion on the effects of herbicides on the structure and function of plant-cell membranes and, more specifically, on their interaction with the lipid components of the cell membrane. Much has been written recently on the ‘re-entry problem’. The approach offered in this volume is an essentially practical one-re-entry intervals are viewed as occupational health standards and particular attention is paid to study design, project organization, requirements for laboratory work and statisti-

Cosrnrr.

Tosicol.

Vol. 18. no. 4

cal analyses. A brief section at the end of this chapter refers to the establishment of re-entry intervals for applications of carbamates. This topic has previously received little attention but presents special problems, particularly because the reversibility of carbamate effects on cholinesterase activity necessitates great speed in carrying out laboratory procedures. Pharmacological Methods in Toxicology. Edited by G. Zbinden and F. Gross. Pergamon Press Ltd., Oxford, 1979. pp. xi + 612. E57.50. The difficulties encountered in recognizing functional disturbances in conventional toxicological studies call for a careful assessment of the possible application of both established and new experimental techniques adopted by pharmacologists for the study and measurement of organ function. This book is a major response to this need. Derived initially from the proceedings of a 1977 International Workshop on the Use of Pharmacological Methods in Safety Evaluation of New Drugs, it appears to be the first in which a group of distinguished pharmacologists has attempted to provide some guidelines on the apphcation of current pharmacological techniques to the assessment of toxic effects, particularly those reflected in disturbances of organ function. Emphasis is placed on methods that have proved useful in the detection of side effects or adverse reactions. In addition to a large number of individual contributions, the volume contains the reports of the working parties of pharmacologists, toxicologists and clinicians, whose discussions on the possible use of pharmacological methods in the preclinical safety evaluation of new drugs preceded the Workshop. While the introductory chapter, entitled “General concepts” may perhaps be considered somewhat lacking in detail, in comparison with the depth of coverage given to some of the more specific topics, it nevertheless provides an interesting view of the similarities and differences in the approaches of pharmacologists and toxicologists, and outlines the problems involved in applying the methods of the one discipline to the other. At the same time, it pinpoints the justifications for introducing pharmacological methods into some aspects of toxicity testing, and indicates areas where this is likely to be of particular benefit. The rest of the book follows a pattern that has become traditional in the study of pharmacology. Beginning with autonomic pharmacology, it analyses, section by section, the pharmacology of the major organs and systems. Outstanding are the sections on the cardiovascular system, on blood coagulation and platelet function and on behavioural pharmacology. The section on bronchopulmonary function is surprisingly brief in view of the great importance of inhalation as a route of entry and elimination of toxic compounds. The only contribution on this topic is the report of the main working party; no individual contributions are presented, as is the case in all the other sections. Other notable deficiences are the omission of skin pharmacology and immunology from the topics considered at the Workshop. However, it is a common disadvantage of volumes based on the proceedings of meetings, that they lack the comprehensive