Brit. J. in(lhstr. Med., 1952, 9, 50.

VANADIUM POISONING FROM CLEANINGOIL-FIRED BOILERS

BY

N. WILLIAMSFrom the London Transport Executive

(RECEIVED FOR PUBLICATION MAY 1, 195 1)

The vanadium content of crude oil ash variesconsiderably according to its source. It may be ashigh as 45%)O in Venezuelian and 14% in Iraniancrude oil.or as low as a trace in Wyoming crude oiland none in the Pennsylvanian product (Dunstan,1938). As fuel oils are residual oils left after thedistillation of the more volatile hydrocarbons, theywill contain a higher proportion of vanadium thanthe corresponding crude oils. Thus an oil with anash content of 01%" containing 40% of vanadiumas V205 would produce 1 lb. of vanadium pentoxidefor I1 tons of oil bumt. A significant proportionof the vanadium accumulates in the gas passages ofboilers. This paper describes the symptoms andclinical findings in men cleaning oil-fired boilers,and sets out evidence that vanadium was responsible.

After the recent war a generating station waspartly converted to burning fuel oil owing toshortage of coal. After cleaning the oil-fired boilersthe men noticed symptoms which they associatedwith the work. Before this conversion there hadbeen no complaints from the boiler-cleaners of anyharmful effect on their health.The boilers are probably the largest oil-fired land

inistallations in this country, each boiler consumingabout 150 tons of fuel oil per week. The lowerpart of the boiler, into which is sprayed the atomizedoil, is known as the combustion chamber, which islined by refractory fire-bricks, and on its rear andside walls are the vertical generating tubes. In theupper part of the boiler are more generating tubesinterspersed between which are the superheatertubes. Considerable quantities of petroleum sootare deposited in both the combustion and super-heater chambers.

Each boiler requires cleaning once a year in orderto maintain its efficiency, and it has been foundnecessary at these times to renew the fire-bricklining. It takes a gang of eight men about five

days to clean a boiler, after which the brickkiversenter to dismantle the fire-brick walls and build newones.The boiler cleaning methods in use when the

investigation began produced large quantities ofdust. The combustion chamber was cleaned bybrushing the soot off the walls, and the boiler tubesby tapping with a rod, the soot falling off as a resultof the vibration. In the superheater chamberthe banks of tubes had to be cleaned by acompressed air jet from a nozzle, as it was difficultto reach them by other means (Fig. 1). Dismantlingthe fire-brick walls also produced dust, and thebricklayers complained of similar, though lesssevere, symptoms than those described by the boiler-cleaners (Fig. 2). The scaffolders, who are the firstto enter the boiler in order to erect the platformsfrom which the cleaners work, have had symptomssimilar to those of the bricklayers, but the casesreported in this paper are all boiler-cleaners.

Methods of AnalysisThe vanadium content of the urine samples was

determined by a colorimetric method described bySandell (1950) in which sodium tungstate is used.The method was checked by estimating vanadiumin the urines of men not exposed to petroleum soot,none being detected in these samples, and urinesto which known quantities of ammonium meta-vanadate were added. It was found that the methodwas accurate in determining quantities as low as002 mg. per specimen. Samples of dust werecollected from different parts of the boilers duringcleaning operations. Measured volumes of dust-laden air were drawn through distilled water con-tained in an aspirator packed with Lessing rings,a guard aspirator also being fitted as a precaution.Three separate samples of 3 7, 4-5, and 6-8 cu. m.were collected, the air being passed at about 7 1 cu.

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VANADIUM POISONING FROM BOILER CLEANING

FIG. 1.-Boiler-cleaners demonstrating methodsof dislodging soot from generator andsuperheater tubes. The one on the left isusing a compressed air lance, and on theright the cleaner is tapping the tubes with arod.

FIo. 2.-Bricklayers dismantling a fire-brickIi

wall. The man on the right is sprayingthe bricks with water.

FIG. 1

F1G. 2

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52BRITISH JOURNAL OF INDUSTRIAL MEDICINE

m. per hour. Vanadium was estimated both in theresultant solution and suspended solids. Thermalprecipitator samples were used to estimate particlesize and concentration. The microscope techniqueinvolved the use of both 4 mm. and 2 mm. objec-tives. Particles counted ranged from 11 to 044microns with the 4 mm. objective, and 4 to 0-15microns using the 2 mm. objective.

SymptomatologyBoiler-Cleaners' Complaints.-All the eight men

engaged on this work complained of symptomsassociated with cleaning oil-fired boilers. The firstsymptoms usually occurred between half and onehour after starting work, but in some cases weredelayed for 12 hours. They consisted of rhinor-rhoea, sneezing, watering of the eyes, soreness ofthe throat and behind the sternum. This group ofsymptoms can be described as the primary symp-toms, the secondary ones appearing after a period ofsix to 24 hours. They were dry cough, wheezing,severe dyspnoea causing the man to rest afterclimbing a 20-foot ladder, lassitude, and depressionwith a disinclination to follow the usual eveningactivities. A greenish-black coating developed onthe tongue which faded two or three days aftercontact with petroleum soot was over. Some of themen noted that the cough became paroxysmal andproductive.These symptoms continued while at work and

only became less severe three days after ceasingwork. In one man the wheezing and dyspnoeapersisted for over a week, but none noticed anypermanent ill-effects.

Personal Observations.-I entered one of the oil-fired boilers while it was being cleaned and remainedthere for about one hour to obtain first-handexperience of the symptoms. Rhinorrhoea, sneez-ing, and watering of the eyes occurred within 15minutes. Three hours later the secondary symptomsbegan to develop: dry cough, wheezing, dyspnoea,and soreness behind the sternum. Cough andwheezing continued throughout the night disturbingsleep. During the next day dyspnoea became moreintense, it being impossible to walk at even amoderately brisk pace on the level. Climbing 30stairs necessitated a short period of rest beforecontinuing. There was a general feeling of depres-sion, and it was difficult to take the usual interest inwork. Cough became productive after the secondday. The bronchospasm was not relieved by" benadryl " but ephedrine and stramonium gavesome relief. The dyspnoea had disappeared by theend of one week, but the cough persisted for afurther week. It had at one time been suggested

that the symptoms were due to sulphur dioxide,but the absence of the characteristic smell and thedelay in the onset of the symptoms excluded thispossibility.

Clinical ReportsAll eight boiler-cleaners were examined beforc and

after work, that is after exposures lasting approxim-ately one week. It was obvious from a knowledgeof the men's previous personalities that they werein low spirits, looked tired, listless, and pale. Oneman complained that coughing had been sufficientlysevere to produce vomiting. Another noticed thatthe tips of his cigarettes turned green.

Examination of the tongue revealed a coatingon the dorsum varying from greenish-black togreenish-yellow. It was not possible to remove thediscoloration by scraping. In two of the men therewere signs of generalized bronchospasm andbronchitis. Two other men had developed rales inthe right axillary region. Cardiac examinationrevealed no abnormality. In two men slight tremorof the hands developed.

X-ray films of the chest, electrocardiograms, androutine examination of the urine for albumin, sugar,and blood revealed no abnormality.

Case ReportsCase 1.-This man, aged 38, had been a boiler-cleaner

from 1947 to 1949. He was examined after five days'cleaning on an oil-fired boiler. He complained of sneezingwithin two hours of starting work and developed a coughthe same evening. He was dyspnoeic the next day onladder climbing, was depressed, and felt tired. Henoticed that cigarette tips turned green. Examinationrevealed a greenish-black coating on the tongue, manyhigh-pitched rhonchi throughout the chest, and rales inthe right axillary region. Blood pressure was 110/70(pre-exposure 138/65). A radiograph of the chest revealedno abnormality. Urine analysis showed 0-08 mg.vanadium in 210 ml. urine passed during the day and0-02 mg. vanadium in an early morning specimen of297 ml.

Case 2.-Aged 40, he had been a boiler-cleaner from1946 to 1949. He was examined after two days' exposure.He developed rhinorrhoea and sneezing within threehours of starting work and a dry cough the same evening.He felt drowsy, and was dyspnoeic on climbing stairs.Examination revealed a yellowish-green coating on thetongue, scattered rhonchi over both lungs with rales atboth bases. Blood pressure was 110/75 (pre-exposure140/95). A radiograph of the chest was normal. Novanadium was detected in the urine.

Case 3.-This man, aged 32, had been a boiler-cleanerfrom 1947 to 1949. He was examined two days afterceasing two days' work in an oil-fired boiler. Hedeveloped rhinorrhoea and sneezing half an hour afterstarting work. He noticed tightness of the chest the sameevening, and felt depressed. Next day dry cough began,

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VANADIUM POISONING FROM BOILER CLEANING

and he became dyspnoeic and orthopnoeic. He had tosit down after climbing a flight of stairs. Examinationrevealed a yellowish-green coating on the tongue. Afine tremor of the hands was evident. No physical signswere detected in the chest. Blood pressure was 120/82(pre-exposure 145/90). A radiooph of the chest wasnormal. No vanadium was detected in the urine.

Case 4.-Aged 43, he had been a boiler-cleaner from1946 to 1949. He was examined after five days' exposure.He developed rhinorrhoea and sneezing within half anhour of starting work and later soreness of the throatand chest. Dry cough started later the same day. Nextday he became dyspnoeic and had to rest after climbinga ladder. He felt depressed. By the fifth day cough hadbecome paroxysmal and induced vomiting. Examinationrevealed a pale green coating on the tongue. No physicalsigns were detected in the chest. Blood pressure was105/70 (pre-exposure 128/80). A day sample of 230 ml.urine contained a trace of vanadium.

Case 5.-This man, aged 39, had been a charge handboiler-cleaner from 1946 to 1949. He was examinedafter five days' exposure. No symptoms appeared onthe first day, but rhinorrhoea and cough developed on thesecond day, with some wheezing and a tight feelingacross the chest. Cough was productive on the third day.The patient was dyspnoeic on climbing stairs, and feltlistless. Examination revealed that he was paler thannormal; the tongue was light green posteriorly. Nophysical signs were detected in the chest. Blood pressurewas 110/65 (pre-exposure 125/80). A radiograph of thechest was normal. No vanadium was detected in theurine.

Case 6.-The patient was aged 35 and had been aboiler-cleaner from 1948 to 1949. He was examined fourdays after ceasing boiler-cleaning, an operation lastingthree days. He developed rhinorrhoea and coughtowards the end of the first day, but had no wheezing.He lacked concentration. Cough ceased two days afterexposure ended. Examination showed a pale yellowcoating over the tongue and a few rales in the rightaxilla. Blood pressure was 110/70 (pre-exposure 150/80).A radiograph of the chest was normal. The urine,152 ml., contained a trace of vanadium.

Case 7.-This man, aged 39, had been a boiler-cleanerfrom 1948 to 1949. He was examined after five days'exposure. He developed sneezing and rhinorrhoeawithin six hours of starting work. Cough began nextday and soon became productive. He was dyspnoeicon climbing a ladder and had to rest at the top. Examina-tion showed a greenish-black coating on the tongue, anda fine tremor of the hands. No physical signs weredetected in the chest. Blood pressure was 150/90 (pre-exposure 150/90). A radiograph of the chest was normal.No vanadium was detected in the urine.

Case 8.-The last patient, aged 26, had been a boiler-cleaner from 1947 to 1949. He had had occasionalcough cleaning coal-fired boilers. He was examinedafter five days' exposure. He developed rhinorrhoea,sore throat, and cough within one hour of starting work,

and felt a tightness of the chest the same evening. -Hewas dyspnoeic next day and had to rest after climbing aladder. He noticed a bitter taste in the mouth, and feltdepressed. Examination showed a thick, dark greencoating on the tongue. No physical signs in the chestwere detected. Blood pressure was 120/75 (pre-exposure130/90). A radiograph of the chest was normal. Novanadium was detected in the urine.

Vanadium in UrineSpecimens over a period of 24 hours, on the last

day of working at boiler cleaning, were collectedfrom each man, precautions being taken to preventcontamination by dust from the clothes and hands.The largest amounts of vanadium were detected

in the urine samples from Case I (0-4 mg. and 0 07mg. per litre). It is interesting to note that this manwas regarded clinically as being the most severelyaffected.

Traces were found in the specimens of Cases 4and 6, one of whom had severe symptoms and theother mild. Vanadium was not detected in theurine of the remaining cases.

Atmospheric DustTable 1 gives the average results obtained from

two thermal precipitator samples taken in thesuperheater. On the average the numerical con-centration of dust particles not exceeding 11 micronsin diameter was 3,526 particles per 1 ml. of air, andof these 93 60, did not exceed 1 micron in size.Although there was such a numerical preponderanceof fine particles these accounted for only a smallproportion of the weight of dust in the air. Theweight concentration of particles within differentsize ranges has been computed on the assumptionsthat the particles are spherical in shape, and thatthe dust has a specific gravity of 2. The resultsof these calculations are shown in the fourth columnof Table 1, where it is seen that the mass con-centration of dust below 1 micron in size was only0-36 mg. per cu. m. In the last column of Table 1the weight concentrations of particles of varioussizes are shown as percentages of the total estimatedweight concentration of particles not greater than11 microns. It should be remembered, however,that the estimate of the total weight concentration(12-3 mg. per cu. m.) of particles of this range ofsize can give no indication of the weight concentra-tion of the whole dust when there are present manyparticles greatly exceeding 11 microns in diameter.That is made clear by comparing the weight con-centrations in Table 1 with those in Table 2 which,gives the results of the three samples taken fromboilers during cleaning operations, by aspiratingair through distilled water (Table 2). The range ofparticle size of the vanadium dust is not known but

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BRITISH JOURNAL OF INDUSTRIAL MEDICINE

TABLE 1

THERMAL PRECIPITATOR SAMPLES TAKEN FROM SUPERHEATER DURING CLEANING OPERATION

Diameter of Particles Number of Particles Numerical Concen- Weight Concentration Weight ConcentrationDiameter!(pe_ __.ir tration of Particles of Particles of Particles

(-) (per 1 ml. air) __ (%) (mg. per cu. .) ()

0 15-1 0 3,300 93-6 0-36 2-910-55 217 614 409 33-35 5-11 9 0 26 7 85 63-8

TABLE 2

ANALYSIS OF DUST FROM BOILER DURING CLEANING

Sampling Point Dust Vanadium Vanadium(mg./cu. m. air) (as % of dust) (mg./cu. m. air)

Superheater chamber .. .. .. .. 659 6-1 40(2Superheater chamber .. .. .. .. 239 7T2 17-2Combustion chamber .. .. .. 489 12 7 58 6

when advising on the use of suitable respirators it issafer to assume that the smallest dust particlescontain vanadium.

Preventive MeasuresEfforts were made to prevent or reduce the

amount of the dust produced, but the main problemwas to prevent the inhalation of the dust by theboiler-cleaners.

It was found that a large part of the boiler couldbe cleaned by an operator standing outside theboiler at the manhole using a lance several feet long,from which a jet of compressed air boosted to a

very high pressure was ejected. The soot was

drawn away from the operator and up the flue tothe outside atmosphere by the induced draught fan.As certain parts of the boiler could not be reachedby this method, men wearing dust respirators(Mark IV, Siebe Gorman), a type approved for usewhere there is a silicosis hazard, entered the boileritself in order to complete the cleaning. When theinduced draught fan could be used to advantage thiswas switched on.

Much soot dust was produced when the fire-brick walls were dismantled and a water spray wastherefore used on the bricks as they were beingdislodged. A tarpaulin was stretched over the topof the combustion chamber to prevent soot particles,dislodged from the boiler tubes by vibration, fallingfrom the superheater chamber into the combustionchamber where men were working.Two boilers have been cleaned using these methods

without a single complaint of symptoms from theboiler-cleaners, scaffolders, or bricklayers.More recently, two boiler-makers and two brick-

layers have been engaged on repairs in a boilerwhich had not been previously cleaned. Theywore their respirators only when it appeared tothem that there was dust in the atmosphere and itis not surprising that they developed minor symp-toms of vanadium intoxication. The vibration ofthe repair work must have caused a small amount ofsoot to get into the air of the combustion chamber.It has therefore been tecommended that all menentering boilers which have not previously beencompletely cleaned should wear suitable res-pirators.

DiscussionA search of the literature has failed to disclose

any reference to symptoms caused by this type ofwork, although it has been known for many yearsthat petroleum and petroleum soot containedvanadium in varying proportions. Respiratorysymptoms of vanadium poisoning among workersextracting vanadium from petroleum soot, obtainedfrom the boilers of oil-fired liners, were describedby Wyers (1946). Information obtained from aboiler-cleaning company revealed that they havepaid increased wages since 1924 for men cleaningoil-fired boilers. The reasons for this have beenobscured by time, but it would appear that therewere two possible reasons: the dirtier nature ofthe petroleum soot and the unpleasant respiratorysymptoms experienced. The management statedthat the men still complained of a wheezing of thechest, but medical advice on this, as an industrialproblem, had never been sought. They had, how-ever, provided the men with a light mask with acotton wool filter.

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VANADIUM POISONING FROM BOILER CLEANING5

Sjoberg (1949) recorded four cases of broncho-pneumonia, one of lobar pneumonia, and one ofpleurisy among workers exposed to vanadium dust.The sick records of the boiler-cleaners over the lasttwo years were examined, but they revealed no

significant increase in sickness absence from any

cause. This would appear to be in accordance withthe views of Symanski (1939) who, in a very fullaccount of vanadium poisoning, concluded that thework should be intermittent in order to allowrecovery from adverse effects. In the present seriesof cases the system of working had, in fact, producedthese conditions as the men work on oil-fired boilersfor only about two weeks in every three months.The blood pressure of the boiler-cleaners taken

after exposure were in no case higher than the pre-exposure readings as might have been expectedfrom the experience of Wyers (1946). In fact theywere lower. No explanation is offered for thesefindings but possibly the men had become accus-

tomed to medical examination by the time the laterreadings were taken.Dutton (1911) described vanadium poisoning

with symptoms and signs referable to disorders ofthe gastro-intestinal and renal systems. These were

anorexia, nausea, and vomiting, and albumin,blood, and casts in the urine. He also observedanaemia, with a reduction both in the number ofcells and of haemoglobin. No cases in the presentseries had symptoms or signs referable to thesesystems, though one man did develop a degree ofpallor. Symanski (1939) also failed to observe anyof these changes. However, two of the boiler-cleaners developed a fine tremor of the hands, asign which Dutton and subsequent writers haveobserved.

In view of the risks of vanadium intoxicationsinvolved in cleaning oil-fired boilers, it is suggested

that methods of cleaning these boilers should bereviewed and means devised which do not involveexposure to the harmful effects of the petroleumsoot. Even intermittent exposures may lead tobronchitis or pneumonia. Men working on theseboilers should be under medical supeivision. It isprobable that much respiratory disease occursamong boiler-cleaners, the true cause of which isnot recognized. Finally, it is hoped that this papermay be of some value in drawing attention to theexistence of the hazard.

SummaryVanadium intoxication in eight men cleaning

oil-fired boilers is described.The method of investigation of the original

complaint, the preventive measures instituted, andthe results achieved are discussed.

It is suggested that methods of cleaning oil-firedboilers should be reviewed, and that men workingon these boilers should be medically supervisied.

I am indebted to Mr. A. T. Wilford, the late super-intendent of laboratories, and to Mr. H. E. Styles, presentsuperintendent of laboratories, and their staff for theanalyses of the dust and urine; to Mr. H. Branton,Generating Station Superintendent, for his help andcooperation; and to Dr. L. G. Norman, the ChiefMedical Officer, for his advice in the preparation of thispaper. The thermal precipitator estimations werecarried out by the Fuel Research Station, Department ofScientific and Industrial Research.

REFERENCESDunstan, A. E. (1938). " The Science of Petroleum," vol. 2, p. 1053,

London.Dutton, W. F. (1911). J. Amer. med. Ass., 56, 1648.Sandell, E. B. (1950). " Colorimetric Determination of Traces of

Metals," 2nd ed. (Chemical Analysis, vol. 3.) London.Sjoberg, S. G. (1949). Nord. Med., 41, 500.Symanski, H. (1939). Arch. Gewerbepath. Gewerbehyg., 9, 295.Wyers, H. (1946). British Journal of Industrial Medicine, 3, 177.

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