LOW-DOSE RADIATION

1027

ways-by a direct effect of the deficiency, and by potentiating an existing primary or secondary immunodeficiency. In view of the wide variety of abnormal responses described in chronic mucocutaneous candidiasis, no firm conclusions can be drawn from small series. It is possible that the individuals described by Mackie have a specific form of immunological tolerance which is independent

factors and overrides their effects. Takeya et al.ll found abnormally high antibody titres together with impaired cell-mediated immunity, but their patients were more severely affected and the immune abnormalities were non-specific. Deficiencies of nutrients such as iron,16,17 folate,16,24 pyridoxine, 17 ,25 and vitamin AI7,26 have been reported in individuals from all groups. Their clinical role in the presence of immunodeficiency has still to be fully evaluated. In view of the beneficial effects of replacement reported in some patients with various defects of immune response, both specific" and non-specific,25,27 correction of nutritional deficiencies is important. Iron in particular may promote epithelial integrity as well as help maintain immunological competence. It could prove an important adjunct to immunotherapy in some types of immunodeficiency. In those individuals who remain unresponsive to hostdirected therapy and whose lesions are suitably confined, surgical excision may offer an alternative.

of other

pathogenic

LOW-DOSE RADIATION THE recommendations of the International Commission on Radiological Protection and the many national and supranational bodies concerned with radiological protection are in accord: man’s exposure to radiation above the natural background must be strictly controlled, and the lessons learned from military, occupational, and therapeutic mishaps suggest that exposure at work should not exceed 5 rem per annum and that population exposure should be held below a tenth of this figure. Few people now believe that there is a radiation dose which is absolutely safe, so the formal statements of the I.C.R.P. have to be translated into terms that everyone can understand. One approach, much favoured by advocates of nuclear power, is analogy: risks are equated with those borne by people who wear wristwatches with luminous dials, who smoke a few cigarettes a day, or who are simply a man of sixty for several minutes. Another approach, illustrated by Dr Bonnell and Dr Harte on p. 1031, is to estimate by how much the natural risk of malignant disease will be increased by exposure to radiation within I.C.R.P. limits. In the argument about the future of nuclear power the acceptability of the cancer risk implied in the I.C.R.P. limits has been 24.Jenkins, W.M.M., MacFarlane, T. W., Ferguson, M. M., Mason, D.K. Int. J.oral Surg.1977, 6, 204. 25.Higgs, J.M., Wells, R.S.Guy’s Hosp.Reps. 1973, 122, 135. 26. Montes, L.F., Krumdieck, C., Cornwell, P. E.J. infect. Dis. 1973, 128, 227. 27.Imperato, P.J., Buckley, C.C., III, Calloway, J. L. Archs Derm. 1968, 97, 139. 1.Hill, J.Sylvanus Thompson memorial lecture, delivered to the British Institute of Radiology, in London on April 14, 1978.

questioned, and so has the ability of engineers to ensure that these limits are not exceeded,2 but what of the I.C.R.P. recommendations themselves? Some scientists, notably in the aftermath of the Windscale inquiry, are claiming that I.C.R.P. limits are too high, and factors of 10 or 20 have been mentioned. It might be thought that errors of great magnitude would have come to light by now in countries such as the U.K. and U.S.A. where civil and military nuclear installations have flourished for a generation. In practice, however, average occupational exposures have been kept far below the 5 rem/year figure, and hitherto nuclear installations have not provided unequivocal evidence either that mortality from, say, leukaemia has increased unexpectedly in nuclear workers or that the I.C.R.P. is right. In a letter this week Dr Stewart replies to criticisms made by the Hon. Mr Justice Parker3 about her evidence against an application to extend the British Nuclear Fuels plant at Windscale. The statistical method which she and her colleagues usedis not easy to grasp and nor is the proof that it is more sensitive than conventional methods. This difficulty-together with the unsuitability of a quasijudicial inquiry in a Whitehaven civic hall as a forum for scientific debatemay have contributed to the scepticism with which the so-called Mancuso report has been greeted. This study was exposed to critical scrutiny long before it was published, as it has been since and at a meeting on radiation safety held in Vienna. Two features of this study (it has been updated by two years5) seem to be survivingnamely, a tendency (only above 2.5rad) for the proportionate mortality from cancer among Hanford nuclear workers who have died to increase as the lifetime exposure to radiation rises, and a tendency for badge readings to be higher than average among men who died from malignancies at sites known to be susceptible to radiation.

Professor Colton’s inquiry into U.S. naval dockyard where nuclear submarines are refitted (p. 1018) will also be controversial if early reactions to a newspaper report and other unsatisfactory accounts of their findings is anything to go by. Official statistics permit calculation of the proportion of deaths in all U.S. males that are due to a specific cause (here cancer). This proportionate mortality was similar to that found in a series of deaths in shipyard workers not thought to have been exposed to radiation, while deaths in those whose next of kin recalled that the dead man had worn a radiation badge while at work contained an unexpectedly high proportion of cancers. The findings seem striking for leukasmia, but the numbers are very small. The average age at death was different for the exposed and non-exposed groups, a point meriting discussion even though the method of analysis allows for it. Next of kin may well have been aware of the association between radiation and cancer, and bias in their answers to questions cannot be ruled out. Dr

deaths

Najarian and at a

Commission Environmental Pollution. Sixth Report: Nuclear Power and the Environment. Cmnd 6618. H.M. Stationery Office, 1976. 3. The Windscale Inquiry: report by the Hon. Mr Justice Parker; vol. i. H.M. Stationery Office, 1978. 4. Mancuso, T. F., Stewart, A., Kneale, G. Hlth Phys. 1977, 33, 369. 5. Kneale, G. W., Stewart, A. M., Mancuso, T. F. Paper presented to International Atomic Energy Agency in Vienna in March, 1978. 2.

Royal

1028

Calculations on the experience of early arrivals at the of the Hiroshima A bombing also suggest that the I.C.R.P. risk factors are wrong6 for leukaemia and that survivors of the Japanese A-bombings may have been selected for fitness to outlive the initial blast, thus adversely affecting the extrapolations made from follow-up data. Prof. Edward P. Radford, chairman of an influential committee of the U.S. National Academy of Sciences, is another challenger, which should add interest to the latest B.E.I.R. report when it reaches the U.K. And, at an anecdotal level, the experience of U.S. soldiers rashly exposed to fall-out from a bomb test in 1957 is worrying-8 deaths from leuksemia when only 2 would have been expected. Buried in the records of employing authorities in the U.S.A. and U.K. there may lie sufficient data for a casecontrol study, which is, perhaps, the only approach that will convince epidemiologists. On the basis of records kept, the United States may be the better equipped of the two; certainly one attempt by the National Radiological Protection Board to show that U.K. nuclear workers were no worse off than the rest of the population was not universally well received. Clearly, this material must be made accessible to those who know best how to handle it. There are signs on both sides of the Atlantic that such studies will encounter more cooperation than formerly. scene

CONTAGIOUS EQUINE METRITIS 1977 DURING 1977 a previously unrecognised disease was observed among mares on 29 stud farms in and around Newmarket. In retrospect the disease seems to have been present in Ireland in 1976,8 and more recently it has been reported from France, Australia, and the United States. Cases were first reported in May last year by Crowhurst,9 who emphasised the copious vaginal discharge and the contagious nature of the disease, which was evidently being transmitted venereally although associated stallions remained clinically healthy. The most serious effect was that infected mares failed to conceive and the financial implications were considerable. A scientific committee under the chairmanship of Sir David Evans, F.R.s., was set up by the Horse Race Betting Levy Board to coordinate investigations and to make recommendations for its control. Venereal spread was not the only mode of transmission, and stud farms were advised to look to their standards of hygiene. 10 After several weeks of intensive work to determine the causal agent a small fastidious gram-negative coccobacillus was isolated in the Regional Public Health Laboratory, Cambridge, from nine of ten typically affected mares." The organism proved to be susceptible to ben-

zylpenicillin, ampicillin, erythromycin, nitrofurantoin, and chlorhexidine; moderately resistant to clindamycin, lincomycin, sulphamethoxazole, and trimethoprim; and highly resistant to streptomycin (M.iC. greater than 500 6. Rotblat, J. New Scientist, Aug. 25, 1977, p. 475. 7. Powell, D. G. Equine vet.J. 1978, 10, 1. 8. O’Driscoll, J. G., Troy, P. T., Geoghegan, F. J. Vet. Rec. 1977, 101, 359. 9. Crowhurst, R. C. ibid. 1977, 100, 476. 10. David, J. S. E., Frank, C., Powell, D. G. ibid. 1977, 101, 189. 11. Platt, H., Atherton, J. G., Simpson, D. J., Taylor, C. E. D., Rosenthal, R. O., Brown, D. F. J., Wreghitt, T. G. ibid. p. 20.

mg/1).

All efforts to identify the organism with any known bacterium have so far failed. A detailed account of its properties is in the press. 12 Soon after a putative pathogen had been isolated, workers at the Equine Research Station, Newmarket, reproduced the disease in pony mares by inserting pure cultures of the organism into the uterine cervix during oestrus. Clinical signs similar to those seen under natural conditions followed within a few days and the same gram-negative coccobacillus was recovered from the purulent dischargey,13 Attempts to isolate the same organism from the genital tract of stallions were initially unsuccessful because cultures were quickly overgrown by organisms of the normal flora. When streptomycin was incorporated in the culture medium, however, the organism was readily isolated, confirming that stallions could be symptomless carriers. Eradication of the carrier state has been more successful in stallions than in mares. So far persons handling or otherwise in contact with infected horses have not shown any clinical evidence of infection likely to be caused by the coccobacillus, but in a letter this week (p. 1038) Dr Taylor and Mr Rosenthal report the finding of agglutinins to the organism in the serum of three groups of human beings-patients attending a genito-medical clinic, healthy adults, and women attending an antenatal clinic. Among women attending the genito-medical clinic the percentage having serum agglutinins at a dilution of 1 in 20 was ten times that in women attending the antenatal clinic and three times that in healthy non-pregnant women. The prevalence among males attending the genito-medical clinic was three times that in healthy men. As Taylor and Rosenthal take care to say, the meaning of these preliminary findings is open to speculation. The fact that they did not find agglutinins in the serum of veterinary surgeons in exceptionally close contact with infected horses suggests that the infection is not readily transmitted from horses to man. Nevertheless, the observed reactions seem specific and clearly need fuller

investigation. WELL-INTENTIONED, BUT... ON Tuesday the Government announced a scheme for compensating those injured as a result of immunisation (see p. 1056). This offer of special treatment is wrong in principle! and a recipe for frustration in practice. The Government denies that its decision rules out a Royal Commission’s proposal2 for weekly payments to parents of all children with severe handicaps, whatever the a cause. Are affected families to get ;10,000 plus k4 a week plus the right to sue area health authorities without having to prove negligence? There are said to be 700 cases eligible for consideration. If this list grows, parents who think they are eligible are likely to be disappointed-if they are not, then official immunisation policy will be in ruins-and those whose children have handicaps of unknown cause wil be equally embittered. A bad precedent has been set. O., Brown, D. F. J., Lapage, (in the press). 13. Platt, H., Atherton, J. C., Simpson, D. J. ibid. (in the press).

12.

Taylor,

L. R.,

C. E. D., Rosenthal, R. Legros, R. M. Equine vet.

1. Lancet, 1977, ii, 910. 2. ibid. March 25, 1978, p.

644.

S. P., Hill,