625 We believe that breast
feeding
in
early infancy
is
a com-
mendable practice. If, however, prevention of the formation of is sought, the elimination of cow’s milk from be thorough. We regard with suspicion the common procedure of feeding neonates with cow’s milk-based formulas at delivery hospitals in the night-time. Our study shows that minor quantities of cow’s milk protein can elicit the production of milk-specific IgE. Our data even suggest that large quantities of antigen might inhibit this response.
milk-specific IgE the diet
must
We thank Pharmacia for reagents. for Allergic Diseases and Children’s Hospital,
Hospital
FRED BJÖRKSTÉN ULLA M. SAARINEN
University of Helsinki, SF-00250 Helsinki 25, Finland
PROPHYLACTIC CO-TRIMOXAZOLE IN LEUKÆMIA
SIR,-Dr Enno and colleagues show (Aug. 19, p. 395) that co-trimoxazole reduces the incidence of infection in neutropenic patients being treated for acute leukaemia. They also show that giving prophylactic non-absorbable antibiotics and nursing their neutropenic patients in single rooms with reverse isolation is a waste of time, since 94% of their controls became infected despite these measures. It seems that prophylactic cotrimoxazole should be used to replace other expensive and labour-intensive measures, not to supplement them. Pathology Department, Royal West Sussex Hospital, Chichester, West Sussex
C.
PO19 4SE
**This letter has been shown lows.-ED.L.
to
Dr
Catovsky,
J. T. BATEMAN whose
reply fol-
SIR,-Dr Bateman concludes from our study that because the addition of co-trimoxazole was useful in reducing the incidence of infection, the other prophylactic measures were not necessary. Previous controlled studies have shown the value of gut prophylaxis and reverse isolation in the management of patients with acute myeloid leukaemia (A.M.L.).1-4 Recent studies at the Baltimore Cancer Center (Dr P. Wiernik, personal communication) have shown that co-trimoxazole alone may be as effective as gut prophylaxis with oral gentamicin, vancomycin, and nystatin in preventing infection in A.M.L. A study in Winnipeg,5 on the other hand, showed that co-trimoxazole was better than no prophylaxis in neutropenic patients. A formal trial to see whether the non-absorbable antibiotics used for gut prophylaxis may be redundant if co-trimoxazole is used has not yet been carried out, but we are about to do so. Although the end-point of our study was the development of fever and infection, the final outcome (i.e., the successful treatment of the infection and clinical remission) is the most important objective and should be kept in perspective. Serious infections in patients with A.M.L. are most commonly due to gram-negative bacteria thought to be derived from the patient’s own gut flora. Gut prophylaxis may not only reduce the rate of infection but also may reduce the number of invading organisms and thus prevent overwhelming septicxmia and death from shock, for this has been uncommon in our unit since the routine use of oral non-absorbable antibiotics. We now rarely see serious perianal infections, a common and fatal problem in the past. Although the need for additional gut prophylaxis was not tested in our controlled study, we do not yet feel able to aban1. Schimpff, S. C.,
Greene, W. H., Young, V. M., Fortner, C. L., Jepsen, L., Cusack, N., Block, J. B., Wiernik, P. H. Ann. intern. Med. 1975, 82, 351. 2 Storring, R. A, McElwain, T. J., Jameson, B., Wiltshaw, E., Spiers, A. S. D., Gaya, H. Lancet, 1977, ii, 837. 3. Levine, A. S. Clins Hemat. 1976, 5, 409. 4. Rodriguez, V., Bodey, G. P., Freireich, E. J., McCredie, K. B., Gutterman, J. U., Keating, M J., Smith, T. L., Gehan, E. A. Medicine, 1978, 57, 253. 5. Gurwith, M J. Antimicrob. Chemother. 1978, 4, 302.
don this and other in previous studies.
prophylactic
measures
shown
to
be useful
,
M.R.C. Leukæmia Unit and Department of Bacteriology,
A. ENNO
D. CATOVSKY
Royal Postgraduate Medical School,
J. DARRELL
London W12 0HS
HEALTH SCREENING IN RESIDENTIAL HOMES
SIR,—Iwas interested in the paper by Professor Brocklehurst and his colleagues (July 15, p. 141) as I have just participated in a survey of four local-authority residential homes in this district.’ We were studying, not new -referrals, but an established population in the homes, and no clear indication was available as to the fitness of individuals at the time of their admission. Nevertheless, the results are revealing. 183 residents were examined medically and assessed for daily living activities. Even in this "captive" group, for whom one might reasonably have expected a greater degree of awareness and thoroughness of surveillance on the part of their medical attendants, 763 significant medical conditions were found of which only 299 were apparently known (or at any rate heeded) by the doctors concerned. Most of the previously unknown conditions were minor, but at least two-thirds of them were treatable. Furthermore, over 1 in 4 residents had conditions which needed prompt referral to their general practitioners. 15 residents were regarded as below standard for residential care, and 6 of them were accepted (or referred) for admission to hospital immediately. For a variety of reasons and after discussion with home staff it was decided to leave the remainder in the homes. At the other end of the scale 27 individuals were judged fit for less sheltered accommodation. The implications of this finding at first led to some misunderstanding with the local social services department, as it was seen as a criticism of the judgment of social workers. This was not our intention, and I’ am glad to say that amity has been restored. Clearly, health and fitness are major considerations in assessing need for part m accommodation but equally clearly doctors must allow the social services sovereignty of final decision in their own departments. Locally, we now hope to cooperate even more closely in the more rational assessment and allocation of scarce residential places. Trinity Hospital, PETER F. ROE
Taunton, Somerset
S!R,—The importance of medical screening of elderly people who are on the verge of moving from independence to institutional living was demonstrated by Professor Brocklehurst and his colleagues in your issue of July 15. In Copenhagen such medical screening has been assured since 1973 as a consequence of a regulation, passed by the municipal authorities, to the effect that no elderly person can be accepted for institutional care without having been examined at one of the five geriatric departments in the city, either in outpatient departments or after hospital admission. The geriatric department concerned receives two referral documents for every pensioner referred-one filled in by the elderly person’s general practitioner and the other by the district nursing services. An analysis of 196 consecutive referrals2 revealed the following items. Disability affecting the elderly person’s ability to cope independently were recorded many times, the most common being difficulty in walking (38%), vertigo, falls, or fainting (35%), mental disturbances (dementia, psychosis, neurosis) (27%), decreased vision (20%), cardiopulmonary troubles (dyspnoea, angina pectoris) (18%), decreased hearing (13%), urinary incontinence (12%), compromised function of upper 1. Roe, P F., Guillem, V. L. Hlth Soc Serv. 2. Krakauer, R. Ugeskr. Læg. (in the press).
J. 1978, 88,
168.
626 extremities (10%), unspecified debility (3%), and speech troubles (2%). Combinations of disabilities were common. There was considerable variation between the assessment made by the G.P., the district nursing services, and the geriatric department regarding the incidence of these types of disabilities. The numbers cited correspond to the assessment made by the geriatric department. Two-thirds of the referred pensioners wished for, or at least contemplated, a change of accommodation. Requests for allocation of accommodation in nursing-homes were met in about 50% of the cases, whereas only 23% of the requests for sheltered housing were met. After assessment, treatment and provision of necessary services and improvements in living conditions it was decided, in 51% of cases, that the referred pensioner could and should remain at home. Almost all of the pensioners had been referred because of imminent or established breakdown in their ability to cope independently in their own homes. The figures demonstrate that geriatric assessment and consequent action help many elderly people to continue independent living outside institutions -and such assessments reduce (by half) the need for institutional care for frail elderly people. Middelfart Sygehus, 5500 Middelfart, Denmark
R. KRAKAUER
SALTED FISH AND NASOPHARYNGEAL CARCINOMA IN SOUTHERN CHINESE
SiR,—The unusually high incidence of nasopharyngeal carcinoma (N.P.C.) in southern Chinese both in and outside China has been known for over fifty years and is thus likely to be the product of a traditional environment peculiar to southern Chinese. The age-specific incidence curves for southern Chinese of both sexes rises steeply after the age of 19-24 years. Ho,’-3 has suggested that the aetiology involves an interaction between a genetically determined susceptibility, early infection by the ubiquitous Epstein-Barr virus (E.B.v.), and consumption of a traditional preserved food by southern Chinese from early childhood. Salted fish, a traditional food frequently consumed during weaning and post-weaning periods, contains a variety of volatile nitrosamines,4-6 compounds which induce turnours in the nasal cavities and/or nasopharyngeal tube in animals.7-11 Carcinomas appeared in the nasal cavity and maxillary sinus of 4 of 22 albino rats fed salted fish for 12-24 months (ref. 11 and unpublished). We have applied the Ames mutagenicity test12 using the TA100 and TA98 strains of Salmonella typhimurium and mammalian microsomal (S-9 mix) activation to extracts of salted fish and to the urine of albino rats which had consumed such fish. Salted-fish extracts were prepared by mincing and suspension in dimethylsulphoxide (2 ml/g of fish) with vigorous shaking for 24 h and centrifugation at 10 000 rev/ min for 10 min at room temperature. The Ames test was done with the supernatants: Urine samples were collected for 72 h from 4 pairs of fish-consuming rats and 4 pairs of controls (matched for sex, age
and body-weight). The test animals were fed daily with steamed cooked salted fish and fresh water, whereas the control rats were given fresh water and animal chow salted to the concentration found in the salted fish. Pooled urine from each pair of rats was concentrated about a 100-fold, dissolved in 4 ml dimethylsulphoxide, and subjected to the Ames test. Mutagenic activity for both TA100 and TA98 was found in all the salted-fish preparations tested and all showed a doseresponsive curve (see figure). Since TA100 and TA98 detect different mutagens, there was probably more than one mutagen in the preparations tested. In most cases mutagenic activity was enhanced by liver microsomal activation, and in some cases also by preincubating the bacteria with S-9 mix at 25 °C for 20 min before the test.’4 This procedure causes selective enhancement of the activity of N-nitroso compounds, suggesting that some of the mutagens in the samples tested are N-nitroso compounds. Mutagenic activity was also found in urine from the experimental rats with a dose-response relationship. Our findings may explain the induction of carcinoma in rats fed with salted fish 16 and the high incidence of N.P.C. in southern Chinese, although one must be cautious in extrapolating events in animals, especially under experimental conditions, to the human situation. We thank the World Health Foundation (Hong Kong) and the Hong Kong Anti-Cancer Society for financial assistance. Medical and Health Department, Institute of Radiology and Oncology, Queen Elizabeth Hospital,
J.H.C.Ho
Kowloon, Hong Kong
D.P.HUANG
Department of Biochemistry, University of Hong Kong
Y.Y.FONG
FAMILIAL AND SPORADIC HODGKIN’S DISEASE ASSOCIATED WITH OCCUPATIONAL WOOD
EXPOSURE 1. 2.
Ho, H. C. J. R. Coll. Surg. Edin. 1975, 20, 223. Ho, H. C. in Cancer in Asia, Opportunity for Prevention, Detection and Treatment. Gann Monograph on Cancer Research no. 18. p. 49. 1974. 3. Ho, J. H. C. Int. J Radiat. Oncol. Biol. Phys. 1978, 4, 181. 4. Fong, Y. Y., Chan, W. C. Nature, 1973, 243, 421. 5. Fong, Y. Y., Chan, W. C. Fd Cosmet. Toxicol. 1976, 14, 95. 6. Huang, D. P., Ho, J. H. C., Gough, T. A., Webb, K. S. J. Food Safety, 1977, 1, 1. 7. Cardesa, A., Pour, P., Haas, H., Althoff, J., Mohr, U. Cancer, 1976, 37, 346. 8. Althoff, J., Mohr, U., Page, N., Reznik, G. J. natn Cancer Inst. 1974, 53, 795.
Pour, P., Kruger, F. W., Cardesa, A., Althoff, J., Mohr, U. J. natn Cancer Inst. 1973, 1, 1019. 10. Haas, H., Mohr, U., Kruger, F. W. J. natn Cancer Inst. 1973, 51, 1295. 11. Huang, D. P., Saw, D., Teoh, T. B., Ho, J. H. C. Paper presented at the 9.
International Symposium on Etiology and Control of Nasopharyngeal Carcinoma in Kyoto, April 1977 (to be published). 12. Ames, B. N., McCann, J., Yamasaki, E , Mutat. Res. 1975, 31, 347
SIR,-The aggregation of Hodgkin’s disease in communities the influence of environmental risk infectious nature.’ Evidence implicating industrial or chemical agents has been scarce, although an excess risk has been reported among woodworkers2 and organic chemists.4 An occupational exposure may have contributed to a fami-
and families has
suggested
factors, particularly of
an
13. Yamasaki, E., Ames, B. N. Proc. natn Acad. Sci. U.S.A., 1977, 74, 3555. 14. Yahagi, T., Nagao, M., Seino, U., Matsushima, T., Sugimura, T., Okada, M. Mutat. Res. 1977, 48, 121. 1 Gutensohn, N., Cole, P. Int. J. Cancer, 1977, 19, 595. 2. Milham, S., Hesser, J. E. Lancet, 1967, ii, 136. 3. Grufferman, S., Duong, T., Cole, P. J. natn Cancer Inst. 1976, 57, 1193. 4. Olin, R. Lancet, 1976, ii, 916.
feeding
in
early infancy
is
a com-
mendable practice. If, however, prevention of the formation of is sought, the elimination of cow’s milk from be thorough. We regard with suspicion the common procedure of feeding neonates with cow’s milk-based formulas at delivery hospitals in the night-time. Our study shows that minor quantities of cow’s milk protein can elicit the production of milk-specific IgE. Our data even suggest that large quantities of antigen might inhibit this response.
milk-specific IgE the diet
must
We thank Pharmacia for reagents. for Allergic Diseases and Children’s Hospital,
Hospital
FRED BJÖRKSTÉN ULLA M. SAARINEN
University of Helsinki, SF-00250 Helsinki 25, Finland
PROPHYLACTIC CO-TRIMOXAZOLE IN LEUKÆMIA
SIR,-Dr Enno and colleagues show (Aug. 19, p. 395) that co-trimoxazole reduces the incidence of infection in neutropenic patients being treated for acute leukaemia. They also show that giving prophylactic non-absorbable antibiotics and nursing their neutropenic patients in single rooms with reverse isolation is a waste of time, since 94% of their controls became infected despite these measures. It seems that prophylactic cotrimoxazole should be used to replace other expensive and labour-intensive measures, not to supplement them. Pathology Department, Royal West Sussex Hospital, Chichester, West Sussex
C.
PO19 4SE
**This letter has been shown lows.-ED.L.
to
Dr
Catovsky,
J. T. BATEMAN whose
reply fol-
SIR,-Dr Bateman concludes from our study that because the addition of co-trimoxazole was useful in reducing the incidence of infection, the other prophylactic measures were not necessary. Previous controlled studies have shown the value of gut prophylaxis and reverse isolation in the management of patients with acute myeloid leukaemia (A.M.L.).1-4 Recent studies at the Baltimore Cancer Center (Dr P. Wiernik, personal communication) have shown that co-trimoxazole alone may be as effective as gut prophylaxis with oral gentamicin, vancomycin, and nystatin in preventing infection in A.M.L. A study in Winnipeg,5 on the other hand, showed that co-trimoxazole was better than no prophylaxis in neutropenic patients. A formal trial to see whether the non-absorbable antibiotics used for gut prophylaxis may be redundant if co-trimoxazole is used has not yet been carried out, but we are about to do so. Although the end-point of our study was the development of fever and infection, the final outcome (i.e., the successful treatment of the infection and clinical remission) is the most important objective and should be kept in perspective. Serious infections in patients with A.M.L. are most commonly due to gram-negative bacteria thought to be derived from the patient’s own gut flora. Gut prophylaxis may not only reduce the rate of infection but also may reduce the number of invading organisms and thus prevent overwhelming septicxmia and death from shock, for this has been uncommon in our unit since the routine use of oral non-absorbable antibiotics. We now rarely see serious perianal infections, a common and fatal problem in the past. Although the need for additional gut prophylaxis was not tested in our controlled study, we do not yet feel able to aban1. Schimpff, S. C.,
Greene, W. H., Young, V. M., Fortner, C. L., Jepsen, L., Cusack, N., Block, J. B., Wiernik, P. H. Ann. intern. Med. 1975, 82, 351. 2 Storring, R. A, McElwain, T. J., Jameson, B., Wiltshaw, E., Spiers, A. S. D., Gaya, H. Lancet, 1977, ii, 837. 3. Levine, A. S. Clins Hemat. 1976, 5, 409. 4. Rodriguez, V., Bodey, G. P., Freireich, E. J., McCredie, K. B., Gutterman, J. U., Keating, M J., Smith, T. L., Gehan, E. A. Medicine, 1978, 57, 253. 5. Gurwith, M J. Antimicrob. Chemother. 1978, 4, 302.
don this and other in previous studies.
prophylactic
measures
shown
to
be useful
,
M.R.C. Leukæmia Unit and Department of Bacteriology,
A. ENNO
D. CATOVSKY
Royal Postgraduate Medical School,
J. DARRELL
London W12 0HS
HEALTH SCREENING IN RESIDENTIAL HOMES
SIR,—Iwas interested in the paper by Professor Brocklehurst and his colleagues (July 15, p. 141) as I have just participated in a survey of four local-authority residential homes in this district.’ We were studying, not new -referrals, but an established population in the homes, and no clear indication was available as to the fitness of individuals at the time of their admission. Nevertheless, the results are revealing. 183 residents were examined medically and assessed for daily living activities. Even in this "captive" group, for whom one might reasonably have expected a greater degree of awareness and thoroughness of surveillance on the part of their medical attendants, 763 significant medical conditions were found of which only 299 were apparently known (or at any rate heeded) by the doctors concerned. Most of the previously unknown conditions were minor, but at least two-thirds of them were treatable. Furthermore, over 1 in 4 residents had conditions which needed prompt referral to their general practitioners. 15 residents were regarded as below standard for residential care, and 6 of them were accepted (or referred) for admission to hospital immediately. For a variety of reasons and after discussion with home staff it was decided to leave the remainder in the homes. At the other end of the scale 27 individuals were judged fit for less sheltered accommodation. The implications of this finding at first led to some misunderstanding with the local social services department, as it was seen as a criticism of the judgment of social workers. This was not our intention, and I’ am glad to say that amity has been restored. Clearly, health and fitness are major considerations in assessing need for part m accommodation but equally clearly doctors must allow the social services sovereignty of final decision in their own departments. Locally, we now hope to cooperate even more closely in the more rational assessment and allocation of scarce residential places. Trinity Hospital, PETER F. ROE
Taunton, Somerset
S!R,—The importance of medical screening of elderly people who are on the verge of moving from independence to institutional living was demonstrated by Professor Brocklehurst and his colleagues in your issue of July 15. In Copenhagen such medical screening has been assured since 1973 as a consequence of a regulation, passed by the municipal authorities, to the effect that no elderly person can be accepted for institutional care without having been examined at one of the five geriatric departments in the city, either in outpatient departments or after hospital admission. The geriatric department concerned receives two referral documents for every pensioner referred-one filled in by the elderly person’s general practitioner and the other by the district nursing services. An analysis of 196 consecutive referrals2 revealed the following items. Disability affecting the elderly person’s ability to cope independently were recorded many times, the most common being difficulty in walking (38%), vertigo, falls, or fainting (35%), mental disturbances (dementia, psychosis, neurosis) (27%), decreased vision (20%), cardiopulmonary troubles (dyspnoea, angina pectoris) (18%), decreased hearing (13%), urinary incontinence (12%), compromised function of upper 1. Roe, P F., Guillem, V. L. Hlth Soc Serv. 2. Krakauer, R. Ugeskr. Læg. (in the press).
J. 1978, 88,
168.
626 extremities (10%), unspecified debility (3%), and speech troubles (2%). Combinations of disabilities were common. There was considerable variation between the assessment made by the G.P., the district nursing services, and the geriatric department regarding the incidence of these types of disabilities. The numbers cited correspond to the assessment made by the geriatric department. Two-thirds of the referred pensioners wished for, or at least contemplated, a change of accommodation. Requests for allocation of accommodation in nursing-homes were met in about 50% of the cases, whereas only 23% of the requests for sheltered housing were met. After assessment, treatment and provision of necessary services and improvements in living conditions it was decided, in 51% of cases, that the referred pensioner could and should remain at home. Almost all of the pensioners had been referred because of imminent or established breakdown in their ability to cope independently in their own homes. The figures demonstrate that geriatric assessment and consequent action help many elderly people to continue independent living outside institutions -and such assessments reduce (by half) the need for institutional care for frail elderly people. Middelfart Sygehus, 5500 Middelfart, Denmark
R. KRAKAUER
SALTED FISH AND NASOPHARYNGEAL CARCINOMA IN SOUTHERN CHINESE
SiR,—The unusually high incidence of nasopharyngeal carcinoma (N.P.C.) in southern Chinese both in and outside China has been known for over fifty years and is thus likely to be the product of a traditional environment peculiar to southern Chinese. The age-specific incidence curves for southern Chinese of both sexes rises steeply after the age of 19-24 years. Ho,’-3 has suggested that the aetiology involves an interaction between a genetically determined susceptibility, early infection by the ubiquitous Epstein-Barr virus (E.B.v.), and consumption of a traditional preserved food by southern Chinese from early childhood. Salted fish, a traditional food frequently consumed during weaning and post-weaning periods, contains a variety of volatile nitrosamines,4-6 compounds which induce turnours in the nasal cavities and/or nasopharyngeal tube in animals.7-11 Carcinomas appeared in the nasal cavity and maxillary sinus of 4 of 22 albino rats fed salted fish for 12-24 months (ref. 11 and unpublished). We have applied the Ames mutagenicity test12 using the TA100 and TA98 strains of Salmonella typhimurium and mammalian microsomal (S-9 mix) activation to extracts of salted fish and to the urine of albino rats which had consumed such fish. Salted-fish extracts were prepared by mincing and suspension in dimethylsulphoxide (2 ml/g of fish) with vigorous shaking for 24 h and centrifugation at 10 000 rev/ min for 10 min at room temperature. The Ames test was done with the supernatants: Urine samples were collected for 72 h from 4 pairs of fish-consuming rats and 4 pairs of controls (matched for sex, age
and body-weight). The test animals were fed daily with steamed cooked salted fish and fresh water, whereas the control rats were given fresh water and animal chow salted to the concentration found in the salted fish. Pooled urine from each pair of rats was concentrated about a 100-fold, dissolved in 4 ml dimethylsulphoxide, and subjected to the Ames test. Mutagenic activity for both TA100 and TA98 was found in all the salted-fish preparations tested and all showed a doseresponsive curve (see figure). Since TA100 and TA98 detect different mutagens, there was probably more than one mutagen in the preparations tested. In most cases mutagenic activity was enhanced by liver microsomal activation, and in some cases also by preincubating the bacteria with S-9 mix at 25 °C for 20 min before the test.’4 This procedure causes selective enhancement of the activity of N-nitroso compounds, suggesting that some of the mutagens in the samples tested are N-nitroso compounds. Mutagenic activity was also found in urine from the experimental rats with a dose-response relationship. Our findings may explain the induction of carcinoma in rats fed with salted fish 16 and the high incidence of N.P.C. in southern Chinese, although one must be cautious in extrapolating events in animals, especially under experimental conditions, to the human situation. We thank the World Health Foundation (Hong Kong) and the Hong Kong Anti-Cancer Society for financial assistance. Medical and Health Department, Institute of Radiology and Oncology, Queen Elizabeth Hospital,
J.H.C.Ho
Kowloon, Hong Kong
D.P.HUANG
Department of Biochemistry, University of Hong Kong
Y.Y.FONG
FAMILIAL AND SPORADIC HODGKIN’S DISEASE ASSOCIATED WITH OCCUPATIONAL WOOD
EXPOSURE 1. 2.
Ho, H. C. J. R. Coll. Surg. Edin. 1975, 20, 223. Ho, H. C. in Cancer in Asia, Opportunity for Prevention, Detection and Treatment. Gann Monograph on Cancer Research no. 18. p. 49. 1974. 3. Ho, J. H. C. Int. J Radiat. Oncol. Biol. Phys. 1978, 4, 181. 4. Fong, Y. Y., Chan, W. C. Nature, 1973, 243, 421. 5. Fong, Y. Y., Chan, W. C. Fd Cosmet. Toxicol. 1976, 14, 95. 6. Huang, D. P., Ho, J. H. C., Gough, T. A., Webb, K. S. J. Food Safety, 1977, 1, 1. 7. Cardesa, A., Pour, P., Haas, H., Althoff, J., Mohr, U. Cancer, 1976, 37, 346. 8. Althoff, J., Mohr, U., Page, N., Reznik, G. J. natn Cancer Inst. 1974, 53, 795.
Pour, P., Kruger, F. W., Cardesa, A., Althoff, J., Mohr, U. J. natn Cancer Inst. 1973, 1, 1019. 10. Haas, H., Mohr, U., Kruger, F. W. J. natn Cancer Inst. 1973, 51, 1295. 11. Huang, D. P., Saw, D., Teoh, T. B., Ho, J. H. C. Paper presented at the 9.
International Symposium on Etiology and Control of Nasopharyngeal Carcinoma in Kyoto, April 1977 (to be published). 12. Ames, B. N., McCann, J., Yamasaki, E , Mutat. Res. 1975, 31, 347
SIR,-The aggregation of Hodgkin’s disease in communities the influence of environmental risk infectious nature.’ Evidence implicating industrial or chemical agents has been scarce, although an excess risk has been reported among woodworkers2 and organic chemists.4 An occupational exposure may have contributed to a fami-
and families has
suggested
factors, particularly of
an
13. Yamasaki, E., Ames, B. N. Proc. natn Acad. Sci. U.S.A., 1977, 74, 3555. 14. Yahagi, T., Nagao, M., Seino, U., Matsushima, T., Sugimura, T., Okada, M. Mutat. Res. 1977, 48, 121. 1 Gutensohn, N., Cole, P. Int. J. Cancer, 1977, 19, 595. 2. Milham, S., Hesser, J. E. Lancet, 1967, ii, 136. 3. Grufferman, S., Duong, T., Cole, P. J. natn Cancer Inst. 1976, 57, 1193. 4. Olin, R. Lancet, 1976, ii, 916.
