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Toxic chemicals in agriculture and food storage
SHORT REVIEWS
41
including toxicological and other pertinent data, published and unpublished, on those pesticides known to leave residues in food when used according to good agricultural practice, and to issue the conclusions in the form of "acceptable daily intakes", suppo.rted by explanations of the basis for each value. TOXIC HAZARDS OF PESTICIDES TO MAN The Twelfth Report by the WHO Expert Committee on Insecticides (Wld. Hlth. Org. techn. Rep. Ser. 1962, 227) covers a rather narrower field than ,the title suggests. The Committee confines itself to reporting on the acute toxic effects, resulting from the use of certain insecticides employed in public health work, and the preventative measures to reduce this hazard. The restricted approach is due to the fact that two other WHO committees are to discuss other aspects of health hazards due to insecticides. Safety aspects of insecticide residues in food were discussed on 9-16th October 1961 by the Joint FAO/WHO Expert Committee and there was a WHO/ILO Committee meeting in April, 1962 to discuss occupational hazards to workers in agriculture. The Committee considers the status of the chlorinated hydrocarbon insecticides in public health use and the success that has been achieved by their use. With regard to the safety aspect, the Committee merely says that no significant toxic hazard has resulted from the use of this class of compound. The absence of a detailed examination of the toxicity aspect of these agents is disappointing; the Committee might usefully have considered the chronic hazard to public health operatives resulting from accumulation in body fat of chlorinated hydrocarbons, for on this particular aspect their views would have been especially valuable. In their recommendations however, they ask the WHO to advise them on the manner in which long-term surveys on the health of public health operatives exposed to insecticides over extended periods can best be carried out; the value of such information in assessing chronic hazards resulting from insecticides is realized. Further research is suggested on insecticide levels in the body fat of such operatives. The Committee stresses the importance of close co-operation between national and international agencies having an interest in public health, agriculture, food protection or occupational health, in respect of the evaluation and prevention of acute, subacute, and long-term toxicity risks to man from the use of insecticides. They recommend that the Director-General of WHO explore how this may be made more effective than at present. TOXIC CHEMICALS IN AGRICULTURE AND FOOD STORAGE In their introduction to this Report, the Research Study Group on Toxic Chemicals in Agriculture and Food Storage (H.M.S.O., London, 1962), recognizes that there is some public anxiety about pesticides and the dangers they may occasion. The risks to humans, include that faced by agricultural workers applying them and the general one resulting from their persistence in food. The Group considers the types of insecticides available, the need for them, the extent to which they are used, and measures which are in force to control their sale and use. It reviews the evidence on the hazards to consumers and concludes that the Notification of Pesticides Scheme gives the consumer effective protection in respect of these residues. Possible risks from any cumulative effects of these residues in food are considered but are not thought to represent a danger to man. The special risk of carcinogenesis, however, needs to be constantly reviewed; study of this possibility is to be undertaken by the standing
42
SHORT REVIEWS
Panel on Carcinogenic Hazards in Food Additives and Food Contaminants set up by the Ministry of Health, London. More research is recommended upon many points; the proposals for more research into new assay methods for pesticides and their metabolites, and the study of levels of residues in home produced and imported foodstuffs are the principal points in relation to food hazards. ANTIBIOTICS IN ANIMAL FEEDING The Joint Committee of the Agricultural Research Council and the Medical Research Council on Antibiotics in Animal Feeding (H.M.S.O., London, 1962) was set up in March 1960 with the following terms of reference: " T o examine the possible consequences of the feeding of antibiotics to farm animals, and to consider whether this use constitutes any danger to human or animal health". The Therapeutic Substances (Prevention of Misuse) Act, 1953, permits the addition of penicillin, chlortetracycline and oxytetracycline to the diet of young pigs and poultry. Detailed evidence on the potential hazards this practice may present to animal and human subjects was examined by a Scientific Subcommittee of the Main Committee. In addition, the hazards that might arise from the use of antibiotics in the preservation of poultry earcases or other foods were considered. The Subcommittee finds that there is no evidence to suggest that feeding antibiotics at the permitted levels exerts any harmful effects on the animals themselves and after slaughter there are no more than traces of antibiotics in the carcases or in the animal products. The only potential hazard to animals or human health that can be foreseen arises from the effect of antibiotics on bacterial populations. With regard to the use of antibiotics as preservatives, the Subcommittee notes that the use of antibiotics in preservation of poultry carcases and other human foodstuffs is also being examined concurrently by a Panel of the Ministry of Agriculture, Fisheries and Food Committee on Food Preservatives. The Subcommittee has studied the experimental data so far obtained and subject to the findings of this Panel does not advise any departure from the present prohibition of antibiotics as food preservatives. The Subcorfimittee discusses the changes produced in the bacterial flora of the alimentary tract of treated animals. These include a reduction in the numbers of certain species, particularly Clostridium welchii and the emergence of drug-resistant strains of Escherichia coli and Salmonella species. It notes that there is firm evidence that drug-resistant strains of intestinal pathogens can become established in farm animals following the use of antibiotics in the feed, and some evidence that these strains are transmitted within individual herds or flocks. To the present time these resistant strains have not significantly prejudiced the treatment of animal infection with antibiotics, but a deterioration of the situation is possible. The Subcommittee recommends that the addition of penicillin, chlortetracycline and oxytetracycline to feedstuffs for young pigs and poultry should be allowed to continue and that this practice should also be extended to include young calves. It does not recommend any relaxation of the present prohibition on the use of antibiotics in the feed of adult livestock, including laying poultry, in view of the greater potential risks of such prolonged usage. Finally, the use of additional antibiotics in feedstuffs would not be desirable unless it could be shown that a particular antibiotic has little or no therapeutic application, that its use would be unlikely to reduce the efficacy of other antibiotics used for therapeutic purposes, and that its use in the feed would be economically valuable.
41
including toxicological and other pertinent data, published and unpublished, on those pesticides known to leave residues in food when used according to good agricultural practice, and to issue the conclusions in the form of "acceptable daily intakes", suppo.rted by explanations of the basis for each value. TOXIC HAZARDS OF PESTICIDES TO MAN The Twelfth Report by the WHO Expert Committee on Insecticides (Wld. Hlth. Org. techn. Rep. Ser. 1962, 227) covers a rather narrower field than ,the title suggests. The Committee confines itself to reporting on the acute toxic effects, resulting from the use of certain insecticides employed in public health work, and the preventative measures to reduce this hazard. The restricted approach is due to the fact that two other WHO committees are to discuss other aspects of health hazards due to insecticides. Safety aspects of insecticide residues in food were discussed on 9-16th October 1961 by the Joint FAO/WHO Expert Committee and there was a WHO/ILO Committee meeting in April, 1962 to discuss occupational hazards to workers in agriculture. The Committee considers the status of the chlorinated hydrocarbon insecticides in public health use and the success that has been achieved by their use. With regard to the safety aspect, the Committee merely says that no significant toxic hazard has resulted from the use of this class of compound. The absence of a detailed examination of the toxicity aspect of these agents is disappointing; the Committee might usefully have considered the chronic hazard to public health operatives resulting from accumulation in body fat of chlorinated hydrocarbons, for on this particular aspect their views would have been especially valuable. In their recommendations however, they ask the WHO to advise them on the manner in which long-term surveys on the health of public health operatives exposed to insecticides over extended periods can best be carried out; the value of such information in assessing chronic hazards resulting from insecticides is realized. Further research is suggested on insecticide levels in the body fat of such operatives. The Committee stresses the importance of close co-operation between national and international agencies having an interest in public health, agriculture, food protection or occupational health, in respect of the evaluation and prevention of acute, subacute, and long-term toxicity risks to man from the use of insecticides. They recommend that the Director-General of WHO explore how this may be made more effective than at present. TOXIC CHEMICALS IN AGRICULTURE AND FOOD STORAGE In their introduction to this Report, the Research Study Group on Toxic Chemicals in Agriculture and Food Storage (H.M.S.O., London, 1962), recognizes that there is some public anxiety about pesticides and the dangers they may occasion. The risks to humans, include that faced by agricultural workers applying them and the general one resulting from their persistence in food. The Group considers the types of insecticides available, the need for them, the extent to which they are used, and measures which are in force to control their sale and use. It reviews the evidence on the hazards to consumers and concludes that the Notification of Pesticides Scheme gives the consumer effective protection in respect of these residues. Possible risks from any cumulative effects of these residues in food are considered but are not thought to represent a danger to man. The special risk of carcinogenesis, however, needs to be constantly reviewed; study of this possibility is to be undertaken by the standing
42
SHORT REVIEWS
Panel on Carcinogenic Hazards in Food Additives and Food Contaminants set up by the Ministry of Health, London. More research is recommended upon many points; the proposals for more research into new assay methods for pesticides and their metabolites, and the study of levels of residues in home produced and imported foodstuffs are the principal points in relation to food hazards. ANTIBIOTICS IN ANIMAL FEEDING The Joint Committee of the Agricultural Research Council and the Medical Research Council on Antibiotics in Animal Feeding (H.M.S.O., London, 1962) was set up in March 1960 with the following terms of reference: " T o examine the possible consequences of the feeding of antibiotics to farm animals, and to consider whether this use constitutes any danger to human or animal health". The Therapeutic Substances (Prevention of Misuse) Act, 1953, permits the addition of penicillin, chlortetracycline and oxytetracycline to the diet of young pigs and poultry. Detailed evidence on the potential hazards this practice may present to animal and human subjects was examined by a Scientific Subcommittee of the Main Committee. In addition, the hazards that might arise from the use of antibiotics in the preservation of poultry earcases or other foods were considered. The Subcommittee finds that there is no evidence to suggest that feeding antibiotics at the permitted levels exerts any harmful effects on the animals themselves and after slaughter there are no more than traces of antibiotics in the carcases or in the animal products. The only potential hazard to animals or human health that can be foreseen arises from the effect of antibiotics on bacterial populations. With regard to the use of antibiotics as preservatives, the Subcommittee notes that the use of antibiotics in preservation of poultry carcases and other human foodstuffs is also being examined concurrently by a Panel of the Ministry of Agriculture, Fisheries and Food Committee on Food Preservatives. The Subcommittee has studied the experimental data so far obtained and subject to the findings of this Panel does not advise any departure from the present prohibition of antibiotics as food preservatives. The Subcorfimittee discusses the changes produced in the bacterial flora of the alimentary tract of treated animals. These include a reduction in the numbers of certain species, particularly Clostridium welchii and the emergence of drug-resistant strains of Escherichia coli and Salmonella species. It notes that there is firm evidence that drug-resistant strains of intestinal pathogens can become established in farm animals following the use of antibiotics in the feed, and some evidence that these strains are transmitted within individual herds or flocks. To the present time these resistant strains have not significantly prejudiced the treatment of animal infection with antibiotics, but a deterioration of the situation is possible. The Subcommittee recommends that the addition of penicillin, chlortetracycline and oxytetracycline to feedstuffs for young pigs and poultry should be allowed to continue and that this practice should also be extended to include young calves. It does not recommend any relaxation of the present prohibition on the use of antibiotics in the feed of adult livestock, including laying poultry, in view of the greater potential risks of such prolonged usage. Finally, the use of additional antibiotics in feedstuffs would not be desirable unless it could be shown that a particular antibiotic has little or no therapeutic application, that its use would be unlikely to reduce the efficacy of other antibiotics used for therapeutic purposes, and that its use in the feed would be economically valuable.