MEDICAL ASPECTS OF RADIATIONS USED IN INDUSTRY *

BY

ETHEL BROWNING

From the Factory Department, Ministry of Labour and National Service

Present knowledge of the potential danger ofmany varieties of radiation, and of the measuresnecessary to safeguard industrial workers againstsuch danger, is based first upon the actual experienceof early research workers in this field, and, second,upon preventive measures instituted by variousmedical bodies for personnel engaged in x-ray andradium therapy.The radiations with which industry is chiefly con-

cerned are x-rays, infra-red, light, and ultra-violetrays, radium, and to a much smaller extent, ultra-short waves.

X-raysThe story of the injuries received by pioneers in

the x-ray field is a sad one, so well known that onlybrief reference need be made to it. It is interestingto note, however, that Rontgen himself, who dis-covered x-rays in 1895, escaped injury chieflybecause most of his experiments were photographiconly, and also because he used x-ray tubes placedin a zinc box and protected by lead screens.

Reports of soreness of the eyes, dermatitis andloss of hair began to come in about 1896, but evenin 1899 it was still believed by many authorities thatthese were due to chemical or electrical conditionsin the skin or, as in the case of Dr. Hall Edwardswho eventually died of x-ray cancer, to the developerused. The first case of x-ray cancer in a workmanemployed in making x-ray tubes, and developingfrom a lesion on the back of the hand, was describedin 1902 ; but Dr. Hall Edwards' reports on his owninjuries in 1904 provide the classical description ofthis fatal condition. The redness of the skin, trans-verse lines on the brittle nails, cracks of the epithe-lium, warty growths, sores which would not heal,and the very severe pain, finally necessitating ampu-tation of fingers and forearm, form a picture whichwas to be repeated in other unfortunate victimsbefore the necessity for suitable preventive measureswas fully recognized.

Injuries due to X-rays. Injuries to the skin areperhaps the best known signs of x-ray damage,perhaps because they are so obvious, especially inthe acute stage. An x-ray burn may consist onlyof a patch of acute erythema, which gradually dis-

* A post-graduate lecture given at Manchester University, January30, 1944.

appears in the course of a few weeks, but it may goon to necrosis and ulceration which is extremelydifficult to heal. It is probable, however, that asingle burn never initiates cancer. Chronic x-raydermatitis is a different and entirely characteristicpathological condition, involving processes of bothatrophy and regeneration. Side by side withatrophic loss of the epidermal appendages andobliteration of small blood vessels, leading to areasof necrosis beneath the epidermis, goes reparativeproliferation of surrounding tissues. The clinicalsigns of this combination of atrophy and repair arethickening of the epidermis, hyperkeratosis, cracks,with degenerative changes in the deeper tissues-inother words, a pre-cancerous condition.There are also the later skin reactions, appearing

only some time after exposure has ceased, even aslong as several years after. These may consist oftelangiectases, areas of pigmentation and atrophy,localized thickenings and warts, generally on thedorsum of the hand, or later ulceration due toobliterative endarteritis and lymphangitis.The blood changes caused by excessive exposure

to x-rays are shown first of all by the white cells.A gradually increasing leucopenia, sometimes pre-ceded by a transient leucocytosis, is the most con-stant diagnostic sign. The leucopenia is oftenaccompanied by a lymphopenia, since the lympho-cytes are specially sensitive to x-rays, or sometimesby a relative lymphocytosis. If this condition isdetected at an early stage and the subject removedfrom exposure, it is entirely curable, but if allowedto progress it may culminate in severe and even fataldepression of the bone marrow-aplastic anaemia.Cases of leukaemia as the final stage have also beenreported, but there appears to be some doubt as tothe direct connection between the condition andgeneral x-ray radiation. There seems no scientificreason, however, why leukaemia should not be theend-result of an aplastic marrow, possibly as anover-compensatory regenerative process. We doknow that benzol poisoning, which characteristicallycauses aplasia of the bone marrow, does at timesend fatally, with the bone marrow in a condition ofhyperplastic leukaemia; and, in fact, benzolleukaemia, though not nearly so common as benzolanaemia, is a recognized clinical entity.

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MEDICAL ASPECTS OF RADIATIONS USED IN INDUSTRY

With regard to the generative organs, sterility hasbeen known to occur in some male radiographerswhen protection has been inadequate. Some ofthese cases have eventually recovered. In femaleradiographers and nurses the percentage of sterilityhas been found to be high, and there is said to havebeen a rather high percentage of developmentaldefects in any children born, but the evidence is notconclusive.

Industrial Uses. The use of x-rays for detectingflaws in castings and other metal articles and indiffraction processes is constantly increasing andthe voltage of the apparatus varies considerably.For small castings of light alloys the range is usuallyfrom 30 to 100 kilovolts; for heavy large castings,such as bomb-carriages, from 100 to 200 kv. andin some cases up to 400 kv. In America muchmore powerful installations-up to 1000 kv.-areused, but have not yet been introduced into thiscountry.The chief danger to x-ray operatives arises when

the work is chiefly screening, rather than photo-graphy. Protection from the direct beam can, ofcourse, be afforded by lead screening of the tube.The danger of scatter radiation is less obviousand therefore often less carefully guarded against,and it has not been unusual, until fairly recently, tofind x-ray rooms littered with numerous articlesawaiting examination, all acting as contributorysources of scatter radiation.

Preventive Measures. The measures at presentrecommended to all users of industrial x-rays arebased on the original recommendations of theBritish X-ray and Radium Protection Committee,which was formed in 1921 with the object of pre-venting casualties to x-ray and radium workers.These formed the basis of the International Recom-mendations adopted at Stockholm in 1928 by theSecond International Congress of Radiology. Theyincluded general hygienic conditions for x-ray rooms-size, ventilation, temperature and layout of theapparatus; protection of the x-ray tube by a suffi-cient thickness of lead or its equivalent; the use ofmirrors; provision of screens for fluorescent work;protection against scatter radiation by placing theoperator outside the x-ray room behind walls con-taining the necessary lead or its equivalent; pro-tective clothing; a working week of not more than35 hours with four weeks' holiday a year; andperiodical blood examinations. These recommenda-tions are designed to limit the exposure received bythe operator to what is considered the tolerancedose of one R per week, and to detect the earliestsigns of injury.

Application to Industrial X-ray Exposure.-Thesepreventive measures apply with equal force to theprotection of industrial x-ray operatives, thoughthey are not at present statutory. Naturally, acontinuous check is kept by the Factory Depart-ment on the conditions obtaining in the x-rayindustrial field. It has to be remembered that, evenwith a well installed and well protected x-rayapparatus, the human factor comes into play more

markedly with the industrial worker, who is lesslikely to be aware of the danger and more likely totake liberties with it, than with the trained medicalradiographer. X-ray burns, for instance, shouldnot occur with a fully protected installation andlead rubber gloves, but even where these conditionshave been fulfilled and where advice and instructionshave been given, they have occurred, because theworker has been unable to realize that putting hisuncovered hands in the track of an invisible rayeven for a short time could do any harm.

It will be appreciated that the work in factoriesdiffers from that in hospitals; longer hours andmore continuous spells may have to be worked,and the risk of scatter radiation may be greater.The Chief Inspector of Factories decided therefore,in 1942, after consultation with representatives ofvarious interested bodies, to have a preliminarysurvey made of the actual conditions of exposure infactories using x-rays. A circular letter was sent tomanagements inviting them to co-operate- in ascheme by which the National Physical Laboratoryundertook to measure the dosage revealed by dentalfilms worn for one week by the operatives. If theseshowed evidence of a dosage greater than thetolerance dose of one R per week, the NationalPhysical Laboratory would investigate the plant,and the operative in question would be asked toundergo a blood examination. In this way it ishoped to link up actual exposure with the con-dition of health of the workers. The results sofar have been very encouraging with regard tothe dosage which industrial x-ray workers on thewhole are receiving. In nearly all the large numberalready investigated the dosage varied from 0-1 to0 3 R per week-well below the tolerance dose.

Infra-red Rays and LightCertain industrial occupations, such as welding

or brass foundry work, involve exposure to all threevarieties of radiation-infra-red, light, and ultra-violet; in glass manufacture it has been shown thatinfra-red is the chief harmful component; and inelectro-welding the light and ultra-violet rays formthe greater hazard. Exposure to excessive light, asin gazing at bright objects, may cause transientscotomata which disappear on rest and can beprevented by wearing suitable glasses such as thoseprescribed by the British Standard SpecificationPamphlet No. 679. Infra-red radiations physio-logically produce vasodilatation of the skin vessels,and stimulation of cell activity, thus promotinghealing and tissue repair. They do not penetratevery far before being converted into heat, but somedo penetrate the dermis and may cause an actualrise of body temperature. In excessive dosage theyproduce severe metabolic disturbance, skin burnsand lesions of the eye.

Industrial Exposure and Injury. The chief pro-cesses in which excessive exposure to infra-redradiation is likely to occur are foundry work,welding, glass manufacture, and some varieties offurnace work. Heat cramps are, of course, a

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BRITISH JOURNAL OF INDUSTRIAL MEDICINEsevere metabolic effect which includes the inevitable:- -period of from 4 to 12 hours- and lasts for a timedehydration of the tissues and loss of salt. Thee 'depending on the severity of the exposure. Theprovision of saline drinks is a well-recognized pre-' degree of pigmentation produced, now known toventive measure for the heat colic from which those be a protective reaction, is not directly related towho work in excessive heat frequently complain. the intensity of the erythema. The effects on the

On the skin, infra-red rays produce an erythema blood are seen in an increase in the number of redwhich may amount to severe burning, followed by cells, and a slight increase in the total white cor-pigmentation which is sometimes permanent and puscles for which the lymphocytes rather than themay also be accompanied by chronic inflammatory polymorphs are responsible. There is also anchanges. increase in blood platelets and serum calcium.

Changes in the blood are not so well recognized Industrial Uses and Injuries. There- are manyas a consequence of infra-red radiation but some modern industrial processes in which ultra-violetauthorities believe that severe and continuous rays are used, as it were, deliberately, for their reveal-exposure may cause anaemia and leucopenia. ing power, just as x-rays are. The examination of

Cataract.-The industrial injury which is the chief golf balls to detect defects in the painting and under-recognized effect of infra-red radiation, and which coating, the examination of blue-prints and razoris subject to compensation, is cataract following blades, of linen marked with invisible ink, and ofexposure to molten glass or red-hot metal. Histori- luminized dials, are some examples of this type ofcally, glass-workers' cataract is of great interest. use. In these processes there is very little risk ofIt has been observed in Germany since 1896, and in injury to the eyes since both lamps and personnel1903 Dr. Robinson, surgeon to the Sunderland and are usually well protected and, also, since many ofDurham County Eye Infirmary, published a paper this kind of apparatus emit not true ultra-violet butdrawing attention to the frequency of cataract in ' near' ultra-violet with a wavelength of 3000 tobottle finishers in the glassworks of that district. 4000 A.U. The destructive effects of ultra-violetThis was followed up by Sir Thomas Legge, who radiations on the eye tissues is greater the shortercompared the incidence of cataract in glass workers the wavelength; that is to say, it rises sharplywith that of a large number of operatives who were between 2000 and 2400, is more gradual from 2400not glass workers and who showed that changes in to 2900, and is almost negligible when the wave-the lens were in fact about five times as frequent in length is greater than 3000 A.U. The chief troubleglass workers between 30 and 40 years of age, twice arises when ultra-violet rays are emitted duringas frequent between 41 and 50, and three times as processes for which they are not specifically desired,frequent over 50. such as electro-welding. The eye injuries causedThe character of the cataract differs from that of by excessive ultra-violet radiation show themselves,

the ordinary senile variety in that it always com- like the skin erythema, after a latent period of somemences at the posterior pole of the lens and involves hours. They begin with symptoms of severe con-the cortex, whereas in senile cataract the charac- junctivitis, smarting, lachrymation, photophobiateristic change usually develops in the form of and sometimes chemosis. In severe cases the cornearadiating lines from the periphery, the central may become inflamed and corneal ulceration andpupillary area remaining free. The explanation iritis may follow. Many authorities believe alsogiven by Robinson of the difference was that the that the lens may be injured and that cataract mayposterior pole was practically the optical centre be a final result, as it is of infra-red radiation.where the principal rays from the furnace crowd Prevention. The most logical and successfultogether, cross, and pass on without refraction. prevention of injury to the eyes by infra-red, actinicThat it was the infra-red rather than the ultra-violet or ultra-violet rays, is the provision of either spec-rays which were responsible for the cataract was tacles or screens of glass which intercept the wave-shown by Sir William Crookes during his researches length in question. For processes involving ex-on suitable protective glasses; he found heat rays posure to these wavelengths eye protective glassesin far greater abundance than ultra-violet in the are available, designed according to the Britishradiations from molten glass. Standard Specification. These glasses are graded

according to the proportion of the different radia-tions absorbed by them and are suitable for different

Ultra-Violet Rays types of work-for example, Grade A for lead-Modern knowledge of the effects of ultra-violet burning, lead-brazing and melting furnaces up to

rays is really due to Finsen. It is rather curious about 16000 C., Grade B for acetylene welding,that Finsen should at first have devoted his studies Grades C and D for metal-arc lamps, and Grade Eentirely to the harmful effects of ultra-violet radia- for carbon-arc lamps used in carbon-arc weldingtion and only later, in 1897, turned his attention to and cutting. For protection against ultra-violettheir beneficial action in the treatment of lupus radiation alone, for example from a distant arc,vulgaris. Crookes' special glass is suitable. It absorbs veryThe physiological effects of ultra-violet rays are little visible light but all the dangerous ultra-violet.

exerted chiefly on the skin, the superficial blood A detailed description of all the various glasses willvessels and the haematopoietic system in general. be found in the B.S.S. pamphlet on ' ProtectiveThe erythema produced only appears after a latent Glass for Welding, 1936, No. 679.'

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MEDICAL ASPECTS OF RADIATIONS USED IN INDUSTRYRadium

The credit for the actual discovery of radium goes,of course, to the Curies, who isolated it in 1898,though Becquerel had previously shown thaturanium gave off active radiation.

Injuries due to Radium. The first evidence thatthis potent substance might cause injury to livingtissue was shown, as in the case of x-rays, by skinlesions. Pierre Curie suffered from radium derma-titis, but the best-known example of its acute effectwas the burn received by Becquerel in 1901. Hecarried a tube containing some decigrammes ofimpure radium chloride in his waistcoat pocket forsix hours, and was surprised later to find a patch ofacute erythema on his abdominal wall, followed byulceration which took over a month to heal.Much more serious consequences followed ex-

posure to radium in America from 1917 to 1924.The luminizers of New Jersey are the classicalexample of true radium poisoning, caused by theaccumulation in the tissues of radium which hadalmost certainly been ingested, owing to the habitof the luminizers of pointing with their lips thebrushes which they used for applying the luminouspaint. The necrosis and in some cases sarcoma ofthe jaw which preceded death in 15 cases was nodoubt partly due to local infiltration by this modeof entry, but probably also to the fact that thetrabecular structure of the jawbone makes for lowresistance to infection. Combined with theselesions of the jaw was severe aplastic anaemia. Inten other fatal cases there were malignant tumoursof other bones. Dr. Robley Evans of Massachu-setts Institute of Technology has also called attentionto cases of rarefying- osteitis with spontaneous frac-ture. It is noteworthy that only those luminizerswho had been employed one to two years or longerwere affected, and in many the disease did not showitself until as long as 5 or 6 years after they hadceased work.

These cases are the outstanding examples ofradium poisoning due to the cumulative effect ofradium deposited in the body, but other similarcases have occurred following the ingestion of radio-active medicaments such as radio-active waterscontaining as much as 2 microgrammes of radiumin a two-ounce bottle. One case described by apathologist who was present at the post-mortemexamination was that of a man who had died ofaplastic anaemia of apparently unknown origin.It was discovered, however, that he had drunkradio-active water for rheumatism for the past12 years, and examination of the tissues showed thepresence of a considerable amount of radium. Itshould be mentioned here that the natural radio-active water of some British spas contains only the-most minute traces of radium and, of course, thehuman body normally contains traces of radio-active material.

In considering the injuries which may be causedby radium it is necessary to remember that all threetypes of radiation which it emits, as well as theradon gas which is constantly emanating from it,

have separate potentialities for harm. Alphaparticles, which are the most destructive, are fortu-nately also the least penetrating and their entranceinto the tissues from outside can be most easilyguarded against. But in cases where radium hasbeen deposited in the body, especially in the bones,either by ingestion or long-continued inhalation ofradium dust, alpha particles can keep up a con-tinuous bombardment of the bone marrow andother tissues, with serious results.

Beta particles are less destructive to tissue buthave more penetrating power than alpha particles;they need several millimetres of metal or glass forcomplete screening. Their chief action is on the skin,causing radium dermatitis.Gamma rays are a true radiation of great pene-

trating power; only half of their intensity is lostafter passing through about 1-5 cm. of lead. Theirchief action is upon the blood-forming organs,causing depression of the bone marrow, which ifallowed to continue might lead to fatal aplasticanaemia.Radon is a colourless gas, without taste or smell,

which is being continuously formed from radiumand which is itself continuously being transformedinto the next radio-active element, radium A.It is obvious that prolonged and continuous in-halation of radon must in time add to the risksof damage from external radiation or ingestion ofradium dust.

In considering the risks to health of radiumworkers, therefore, four possibilities must be bornein mind. (1) True radium poisoning.-This wasseen in its worst form in the New Jersey cases.(2) Respiratory lesions.-These have been observedchiefly among the uranium workers in Joachim-sthal in Bohemia, where the incidence of lungcancer is high. This disease, known locally as'Bergkrankheit,' was at one time thought to bedue to inhalation of either arsenic or other metallicparticles, but more recent authorities have con-sidered it due to inhalation of radon given off bythe radium chloride in the uranium ore. (3) Injuryof the blood-forming organs.-A gradual depressionof the white cell count, leading in time to aplasticanaemia. (4) Skin injury.-Like x-rays, radiummay produce an acute burn or patch of erythema,or a chronic dermatitis of atrophic character. It isbelieved, however, that chronic radium dermatitisis less likely to develop into skin cancer than thedermatitis caused by x-rays.

Industrial Uses. The chief use of radium in thiscountry is the application of' luminous compound '

to aeroplane and watch dials, compasses, gun sightsand various electrical instruments.Luminous compound in its dry form is a powder

consisting of zinc sulphide with a small admixtureof radium or mesothorium, the usual proportionbeing 70 micrograms of radio-active substance per1 gramme of compound. By far the greater partof the luminous compound in this country is usedin the form of a paint, made by the addition to thepowder of various mucilages and solvents; a small

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4BRITISH JOURNAL OF INDUSTRIAL MEDICINEamount is used dry. The reason for the addition ofradio-active material to zinc sulphide, which is initself phosphorescent, is to prolong the period ofluminescence when any source of light is removed.

Prevention of Injury to the Health of Luminizers.The preventive measures for the luminizing industryare embodied in the Factories (Luminizing) Healthand Safety Provisions Order of 1942, and theAmendment to the Order 1943. In addition to thestatutory obligations imposed on both employerand employee by this Order, two further pre-cautionary measures have been in use for sometime. These are the six-monthly blood examina-tions of every luminizer, and estimations of theradon content of their exhaled air and of the air ofthe luminizing room. So far it would appear thatstrict enforcement of the provisions of the Lumi-nizing Order and continual instruction to theluminizers themselves has prevented consequencesof anything like the severity of the New Jerseyoccurrence. There have been no cases of fatalradium poisoning, none even of true aplasticanaemia, and the skin effects which have beenobserved have been slight and in most cases transient.

In order to prevent the occurrence of chronicdermatitis from direct contact with luminous com-pound or with radiation from open containers, aprotective covering, consisting of a section of brasstubing with the oblique top filled in with a perspexlid through a small hole in which the applicatorwas inserted, was designed by Professor Mayneordof the Royal Cancer Hospital (see fig. 1). Mostmanagers have accepted this appliance with greatwillingness.Blood Examinations.-In no case has evidence of

true aplastic anaemia been found. Slight leucopeniahas occurred in comparatively few cases, nearlyalways in supervisors who usually weigh out andmix the luminous compound and who are thereforeexposed to heavier dosage than the girls using smallquantities of paint at a time. In all cases whereleucopenia has occurred at successive blood examina-tions this has been brought to the notice of theExamining Surgeon who has then suspended theluminizer for three months; at the end of that timeshe is re-examined and only reinstated if her totalwhite count has returned to normal. The red cellsand haemoglobin have shown very little variation,except that during the first few months of employ-ment the values are rather higher than one wouldexpect in girls of this age and probable nutritiona\level. It is not at all unusual to find counts of5 million r.b.cs. and over, and haemoglobin per-centages of 100-102 per cent.The most interesting and striking feature of the

blood picture of a large proportion of these girls,especially during the first six months, is a highdegree of relative lymphocytosis with a total whitecell count of 6000-8000, or even higher. In theselatter cases this amounts, of course, to an absolutelymphocytosis. In addition, the stained smearsfrequently contain immature cells such as premye-locytes, Tuirk cells, and even occasionally myelo-

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blasts. Usually these abnormalities subside in thecourse of a year or eighteen months and the countremains normal for as long as they remain inemployment. It has not been possible to followtheir further development, because many of thesegirls have changed their work, or married, but in avery few cases who have shown this tendency at thebeginning, and then become normal, and who havestayed on for a number of years, a trend towards agradual lowering of the total white count has beenobserved. The statutory obligation under the

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MEDICAL ASPECTS OF RADIATIONS USED IN INDUSTRYAmendment Order that all luminizers employedmore than a year shall have three months of com-plete removal from exposure will no doubt preventthis trend towards a depressive effect from de-generating into a true leucopenia. Consultationwith many haematologists as to the significance, ifany, of the initial lymphocytosis and the presenceof abnormal cells, appears to confirm the author'sopinion, which is that it represents an initial stimu-lative effect of small doses of radio-active material.In itself the phenomenon is not necessarily harmful,but it must be remembered that hyper-stimulationover a long period might eventually producedepression.Radon Estimations.-An attempt is being made

here, as has already been done by Robley Evans inAmerica to keep a further check on the health ofluminizers by estimation of radon in their exhaledair, in order to ascertain whether in fact any radiumis deposited in the tissues. Research is being carriedout on these lines, under the direction of the M.R.C.by Professor Russ of the Middlesex Hospital, andit is hoped to make further use of the results, butthere are great difficulties of technique and ofarriving at definite conclusions. The method will,it is hoped, be a valuable adjunct to the preventionof serious effects.A dental film test, similar to that for x-ray

workers, is also being worked out by the NationalPhysical Laboratory.

It will be seen, therefore, that while at present thereis no reason to fear for the health of luminizers, itis very necessary in view of the cumulative effect ofradium, and again taking into account the humanfactor which sometimes defeats the strictest regula-tions, not to relax a single precaution and to keep aconstant watch on any developments that mightarise. So far as the Factory Department is con-cerned, this is being done.

Short WavesA brief reference must be made to ' short waves.'

As in the case of x-rays and radium, most of ourknowledge of the biological effects of this variety ofadiation comes from the clinical field, where short-wave therapy has been in use for some time in thetreatment of inflammatory conditions, rhinitis,asthma, sepsis and the results of trauma. Inindustry, short waves are not at present widely used.Before the war there was a gradually increasingmanufacture of television receivers and of medicalshort-wave apparatus, and both these sources ofshort-wave radiation will no doubt increase duringthe post-war years. It is necessary, therefore, tohave some idea what danger, if any, is to be appre-hended if their use becomes more extensive.So far the only symptoms complained of have

been discomfort from sensations of heat, headacheand drowsiness. It appears more than probablethat these are entirely a heating effect, since inactual short-wave therapy, as in diathermy, heatingof the tissues is a known and desired effect.

It has often been stated that the favourable effectof short-wave therapy is due chiefly to dilatation ofcapillaries, but recent observations, by means ofspecial microscopic technique, of human capillarieswhile short-wave therapy was being carried out,showed that there was no marked alteration in thecalibre of the capillaries; there was, however, amarked increase in the rate of blood flow, whichprobably accounted for the rapid subsidence ofoedema and resolution of septic processes. It hasbeen suggested that the chief danger to personsexposed to short waves might arise from theirselective absorption by the body owing to the greatvariation in resistance of the various organs andtissues, and that over-heating of the blood might beassociated first with the possibility of thrombosis,and second with damage to projecting parts of thebody because of the reversal of the normal coolingprocess-that is to say, these parts would receiveheat from the blood instead of having it taken away.

In actual practice, so far as all inquiries haveshown, no such dangers have arisen, and the dis-comfort from overheating can be minimized bysuitable precautions. These include: (1) Keepingout of the field as much as possible. Distant con-trol of the apparatus is the obvious solution.(2) Using the apparatus in atmospheric conditionswhich best provide regulation of the body heat.This could, of course, be achieved by artificialmovement of the air. (3) Suitable screening. Atthe same time it must be emphasized that beyondthe physiological effects described little is known ofany other biological or possibly cumulative pro-perties of these rays, and if their use ever becomesan industrial problem of any magnitude a promisingfield of research and of vigilance will be open tothe industrial medical officer.

SummaryX-rays. Used for detecting flaws in metal. Screening

more dangerous than photography; 'scatter' radiationrequires special precautions. Injuries-skin lesions(burns, dermatitis, pigmentation, warts, malignancy);blood changes (leucopenia, aplastic anaemia, even finalleukaemia); sterility is rare. Prevention by limitationof exposure.

Infra-Red Rays. Injuries-heat cramps, skin erythema,cataract-in foundry and furnace work, welding, glassmanufacture.

Ultra- Violet Rays. Injuries-conjunctivitis, cornealulcer, iritis-in electro-welding. Prevention by spectaclesor protective glass screens.

Radium. Used in luminizing. Injuries-due to alphaor beta particles, gamma-rays, or radon-causing trueradium poisoning (jaw necrosis, bone malignancy,aplastic anaemia); respiratory lesions (including cancer);aplastic anaemia; dermatitis. Prevention by legislation;Mayneord's protective container; periodic blood ex-aminations; radon estimations of exhaled air; dentalfilm test.

Short Waves. Exposure in manufacture of televisionand therapeutic apparatus. Serious risk to health im-probable.

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