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Hazard of Mineral-oil Mist?

MAN’s insatiable curiosity compels him constantlyto seek in his environment patterns that provide abasis for prediction-sequences of events that connectcauses with effects. But the environment is complexand in a thick jungle of intertwining branches (someliving, some dead and leading nowhere) the patternsare obscure until they have first been seen anddescribed by someone else. Characteristically, there-after it is hard to understand why nobody could seethem before. Those who first see patterns sometimesdo it because by logical deduction from other datathey conceive that a particular pattern must exist.Others do so when the opportunity arises for themto view the jungle from an unusual aspect.In this country there have been two epidemics of

scrotal cancer associated with exposure to mineraloil. The first, which began in the 1880s, was in thecotton industry, and it affected men who leanedacross spindles lubricated by oil. The second, whichprobably started in the late 1940s or early 1950s, isaffecting men who work, particularly as tool-setters,with automatic lathes that are both cooled andlubricated by circulating mineral oil. Under certaincircumstances the rapid movement of machinery hasthe effect of turning mineral oil into an aerosol, sothat clouds of oil mist gather over the machines.Where this happens floors, walls, and the undersideof roofs become covered with a layer of oil, and oilmay actually drip from roof supports. Naturalquestions for the worker and the factory doctor are" does the inhalation of mineral-oil mist predisposeto lung disease ? Does it predispose to lung can-cer ? " If it does either, the pattern of cause andeffect will be hard to see against the background highprevalences of chronic bronchitis in areas of heavyair pollution and of lung cancer among cigarettesmokers.

Studies in animals indicate that oil droplets below2-5 µ in diameter readily pass the nasal filter and thatoil droplets which reach the alveoli tend to be

immediately phagocytosed and transferred to the

pulmonary connective tissue and lymph-nodes. 1The responses of mice to exposure to mineral oilsand edible oils, such as corn oil and peanut oil, forperiods of two to four weeks differed. Exposure to1. Shoshkes, M., Banfield, W. G., Rosenbaum, S. J. Archs ind.

Hyg. occup. Med. 1950, 1, 20.

mineral oil was associated with a vigorous localisedforeign-body reaction and patches of lipid pneu-monia, whereas reactions to peanut oil and corn oilwere negligible. Lipid pneumonia, however, wasnot observed in strain-A mice exposed to low concen-trations of mineral-oil aerosol for up to eleven months,and the incidence of pulmonary tumours, which tendto arise spontaneously in this strain, was not increasedby such treatment.2 2 The incidence of infectious

pneumonia in monkeys exposed to mineral-oil mistwas high, and the frequency of deaths in this speciesfrom severe hyperplastic gastritis suggested to

LUSHBAUGH and his colleagues 2 that much of theinhaled oil was deposited in the nasal passages andswallowed.

In 1961, GRAHAM JONES 3 was apparently the first todescribe the effects of mineral-oil mists on man.The men examined were exposed to oil dropletsproduced during the cold reduction by water ofmineral-oil-coated hot-rolled strip steel. 70% ofthe oil-mist droplets produced under these circum-stances are 1 (J. or less in diameter. 12 out of 19men exposed to this mist for from nine to eighteenyears had increased linear striations in the lungsin chest radiographs. The absence of any cases

of lung cancer among men in this factory wasuninterpretable, because the maximum period sincefirst exposure was only eighteen years. A seriouslack of information about the relationship betweendose and response from either animal or humanstudies and a total void about comparative re-

sponses to different mineral oils makes it very hardto guess the extent of any hazard to health from

occupational exposure to mineral-oil mists.Against this background comes the report from

HOLMES et al.,4 who were struck by the coincidenceof 3 cases of men who had survived carcinoma of thescrotum attributed to exposure to mineral oil onlyto succumb later to primary carcinoma of the lung.They therefore reviewed 187 cases of epithelioma ofthe scrotum registered in the Birmingham RegionalCancer Registry between 1950 and 1967 and foundamong them 22 (as against 8-25 expected) instancesof second primary cancer. The 5 second primariesof the skin were not surprising in view of the knownexposure to mineral oil, but 8 men (compared with2-5 expected) had second primaries of the respiratorytract and a further 7 (compared with 2-5 expected)had second primaries of the digestive tract. The

probability that this excess of respiratory cancers isdue to chance is less than 1 in 200, and for the excesscancers of the digestive tract the probability is about1 in 67. Without further information, particularlyabout the smoking habits of the men concerned, itis unwarranted to assume that the respiratory and

2. Lushbaugh, C. C., Green, J. W., Redemann, C. E. ibid. p. 237.3. Jones, J. G. Ann. occup. Hyg. 1961, 3, 264.4. Holmes, J. G., Kipling, M. D., Waterhouse, J. A. H. Lancet, 1970,

ii, 214.

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digestive cancers resulted from exposure to oil mistin the engineering shops where the men’s skins weresufficiently exposed to mineral oil to give themscrotal cancer; but this must be regarded as a strongpossibility. The observations of HOLMES and his

colleagues should therefore prompt thorough andextended studies of men exposed to oil mist. In anyevent, it seems that an opportunity to view the humanjungle from an unusual aspect has partly revealed apattern that no-one saw before.

Mortality during Regular DialysisTreatment

IT is only ten years since SCRIBNER and his col-leagues 1 discovered that a patient with terminalrenal failure could survive indefinitely with the helpof repeated haemodialysis. Yet at the beginning ofthis year 800 patients were undergoing treatment byregular hærnodialysis in England and Wales; justunder half were treating themselves in their homesand the remainder were being treated in hospital.Staff from more than 30 hospitals were concerned intheir supervision. A similar expansion has takenplace elsewhere, and DRUKKER and his colleagues 2

report that in Europe at least 2800 patients are nowunder treatment, supervised by 217 centres. By farthe largest series of patients in the world is thatcollected from the European dialysis units.2 The

figures for the past three years, analysed by a life-tablemethod, show that 83% of patients survived one yearand 63% three years.3 Figures from 14 differentdialysis units in the U.S.A., similarly analysed,4,5yield a total of 302 patients, of whom 87% were aliveone year after the start of treatment and 67% afterthree years. Survival of 58% of patients at sevenyears was also reported. The results from individualdialysis units are based, of course, on smaller num-bers, but they are rather better. Thus, MOORHEAD andhis colleagues 6 from the Royal Free Hospital, whose109 patients were treated in a combined dialysisand transplant programme, report a survival at oneyear of 94% and at six years of 80°7%. The figuresfor home dialysis (89 patients) are even better: 98-9%at one year and 86% at four years. That results of thiskind are not out of the reach of other units is illus-trated by CAMERON and his colleagues,’ who treated

1. Scribner, B. H., Buri, R., Caner, J. E. Z., Hegstrom, R., Burnell,J. M. Trans. Am. Soc. artif. intern. Organs, 1960, 6, 114.

2. Drukker, W., Haagsma-Schouten, W. A. G., Alberts, C., Baarda, B.Proc. Eur. Dial. Transplant Ass. (in the press).

3. Gurland, H. J., Härlen, H., Henze, H., Spoek, M. G. ibid. (in the press).4. Lewis, E. J., Foster, D. M., de la Puente, J., Scurlock, O. Ann.

intern. Med. 1969, 70, 311.5. Cutler, S. J., Ederer, F. J. chron. Dis. 1958, 8, 699.6. Moorhead, J. F., Baillod, R. A., Hopewell, J. P., Knight, A. H.,

Crockett, R. E., Fernando, O. N., Varghese, Z. Br. med. J. Oct.10, 1970, p. 83.

7. Cameron, J. S., Ellis, F. G., Ogg, C. S., Bewick, M., Boulton-Jones,J. M., Robinson, R. O., Harrison, J. Proc. Eur. Dial. TransplantAss. (in the press).

95 patients with 90% survival at one year and 83% atthree years.Most deaths come at the start of regular dialysis

treatment. Thus, 50% of the deaths in Europe 8were in the first six months and 75% within a year ofthe start of treatment. Once a patient has survivedtwo years, he is likely to survive indefinitely, and noupper limit for the duration of regular dialysis treat-ment has yet been recognised. In the combined

European series, heart-failure (20%), cerebrovascularaccident (16%), and myocardial infarction (9-5%)were the commonest causes of death, and they reflectpre-existing vascular disease and inadequate blood-pressure control. These causes of death have beenmuch less prominent in the smaller series. Thus, ofthe 14 dialysis deaths among the Royal Free patients,6only 2 were attributable to ischasmic heart-diseaseand 1 to a cerebrovascular accident. 4 were associatedwith the dialysis procedure itself and 3 to infections,Only 3 of the 7 deaths in the Guy’s series were dueto vascular disease, and depression was judged to bea major feature in the deaths of 3 other patients.

Clearly, both the methods of selection of patientsfor treatment and the timing of the start of regulardialysis may be expected to influence the results.Most units at first accepted only patients aged be-tween 15 and 50 years who did not have gross vasculardisease and who had no other serious illnesses. Butthe paucity of dialysis places has often meant thatpatients were started on treatment much later than isideal, so that their early dialysis life was precariousin the extreme. With the rapid expansion of

dialysis facilities,2 many older patients will probablybe treated, so a definite mortality attributable to

vascular and other incidental disease is likely to

persist. But this should be balanced by the fact thattreatment will probably start earlier in the course ofthe renal failure and before the patient has becomedebilitated. Only one large series 9 has been con-cerned with patients over 50; and surprisingly theyfared as well as younger patients treated in the sameunit. It will be interesting to see whether this resultis confirmed elsewhere.

Patients who cannot be accepted for regular dialysistreatment die almost invariably within a few weeks ormonths. It is remarkable, therefore, that only tenyears after its introduction this treatment is capableof maintaining survival in up to 86% of patients forfour years. Enthusiasm must be tempered by therealisation that the patient does not lead a completelynormal life/° though between two-thirds and four-fifths of the survivors are able to return to the com-

munity and work full-time or run their homesunaided. 7,10

8. Drukker, W., Haagsma-Schouten, W. A. G., Alberts, C., Spoek,M. G. ibid. 1969, 6, 99.

9. Cohen, S. L., Comty, C. M., Shapiro, F. L. ibid. (in the press).10. Baillod, R. A., Crockett, R. E., Ross, A. ibid. 1968, 5, 97.