FINGERPRINT DETECTION AND MERCURY POISONING

378 intensive, treatment with potassium there is risk of acute hyperkalaemia, which develops when the amount of potassium given exceeds the amount which the cells can assimilate. This risk can be reduced by giving potassium salts by mouth and by making frequent estimations of the plasma-potassium level.

During always a

The difficulty of accurately determining minute quantities of mercury may now be regarded as having been overcome, since Milton and Hoskins (1947) have published a method by which it is possible to determine mercury in urine in. concentrations as low as 0-005 part per million.

PREVIOUS INVESTIGATIONS

SUMMARY

Acute hypokalaemia (plasma-potassium level 1-12 m.eq. per litre) developed in a, woman of 44 with chronic kidney disease. It was combated successfully with parenteral and oral potassium salts. In four.days the patient retained 1072 m.eq. of potassium and was

relieved. The administration of neutral

dramatically

potassium phosphate

and hypocalcæmia, with temporary tetany and inhibition of blood-clotting. The administration of a concentrated solution of potassium chloride without a simultaneous supply of phosphate reduced the serum-phosphate to zero. There were no demonstrable changes in serum-calcium or any caused

hyperphosphataemia

clinical symptoms. In experiments on normal rabbits the administration of sodium phosphate lowered the serum-calcium while the serum-potassium remained constant. The infusion of potassium chloride solution in normal rabbits did not lower the serum-phosphate. These findings agree with the conception that the fall in serum-phosphate is intimately connected with the assimilation of potassium by the potassium-deficient cells. REFERENCES

Bodansky, O. (1949) Amer. J. med. Sci. 218, 567. Butler, A. M., Talbot, N. B., Crawford, J. D., MacLachlan, E. A., Appleton, J. (1946) Amer. J. Dis. Child. 72, 481. Ferris, D. O., Odel, H. M. (1950) J. Amer. med. Ass. 142, 634. Kjerulf-Jensen, K. (1949) Ugeskr. Laeg. 111, 773. Mudge, G. H., Vislocky, K. (1949) J. clin. Invest. 28, 482. Rapoport, S., Dodd, K., Clark, M., Syllm, I. (1947) Amer. J. Dis.

Child. 73, 391. Reyersbach, G. C., Butler, A. M., Talbot, N. B. (1948) Ibid, 75, 450.

FINGERPRINT DETECTION AND MERCURY POISONING T. H. BLENCH M.D., B.Hy. Durh., D.P.H. CITY POLICE

SURGEON, LECTURER

IN FORENSIC MEDICINE

HARRY BRINDLE F.R.I.C., Ph.C.

M.Sc. Mane., B.Sc. Lond.,

PROFESSOR OF PHARMACY

UNIVERSITY OF MANCHESTER

METALLIC mercury and mercurial salts are handled and used in various industries, and as a result considerable attention has been paid to the risk of chronic mercurial poisoning. A comparatively recent development is the use of grey powder (hydrargyrum cum creta) in the investigation of fingerprints. The chief drawbacks which have confronted investigators of industrial mercury poisoning have been : (1) the difficulty of accurately determining minute amounts of mercury ; (2) the fact that the three main manifestations of chronic mercurial poisoning-erethism, tremor, and stomatitis-are, particularly in mild cases, difficult to distinguish from conditions which arise fairly commonly in people who have no contact with mercury in any form ; and (3) the apparently considerable quantitative differences in the reaction of different people to mercury, since it has generally been impossible to trace any correlation between the presence or severity of the symptoms and the probable amounts of mercury absorbed. .

The other difficulties still remain.

A comprehensive survey of the historical aspect of chronic mercury poisoning in industry was made by Buckell et al. (1946). They also investigated workers in a thermometer factory, and the amount of mercury excreted in the urine in twenty-four hours ranged from 136 to 3478 µg. The three characteristic symptoms (ere. thism, tremor, and stomatitis) were looked for and their presence or absence was apparently independent of the urinary mercury level. The average mercury level was about the same in the symptomless workers as in those found to have any or all of these three. One employee had at work an excretion of 2360 mg. After seventeen days’ absence he had an excretion of 1290 mg. indicating that mercury was probably still being absorbed from the clothing. Estimation of the mercury content of the air showed that the rate of excretion was very much more than could be absorbed by respiration. Washings from the hands contained up to 9800 µg. per worker. It was concluded that absorp. tion took place largely through the skin or the alimentary tract. In one case the daily excretion of mercury during two separate weeks ranged from 96 to IOJO ;j!.g. In a further week in the same case the range was 66-270 jjg. In 14 controls free from any contact with mercury the highest excretion of mercury was 90 ug. and the lowest 5 µg., the average being 31.5 µg. Agate and Buckell (1949) examined 32 police officers who used grey powder in the demonstration of finger. prints. In their series only two symptoms were manifest -tremor and erethism-and 4 of the 32 police officers showed both symptoms. Again there seemed to be no relationship between the symptoms and the amounts excreted. The average excretion was higher in the officers without symptoms than in those with one or both

symptoms. At first sight these two investigations seem to indicate that there is no relationship between the presence or severity of the symptoms and the amount of mercury ingested or excreted. There are, however, several factors to consider before such a conclusion is drawn. The chief difficulties in interpreting the figures seem to be :

(1) Except in 2 cases in the thermometer factory, the amount of mercury excreted by each person was estimated

during (2)

one

The

day only ; symptoms

particularly in mild

are

not

easily diagnosed

and assessed,

cases.

difficulty may not have been of much because the observers were skilled and were well aware of the pitfalls, but an indication of what is considered an excessive or toxic dose, apart from idio. syncrasy, would help in other cases. It is clear from the published findings in the above investigations that the first difficulty cannot be neglected. We have found that the amount of mercury excreted varies considerably from day to day, and this is illustrated in the one case reported by Buckell et al. (1946) in which repeated determinations were made. In one week the daily variation was from 96 to 1000 µg., and in another week from 66 to 270 µg. It is evident that care must be exercised in drawing deductions from the excretion on a single day. This must be remembered when interpreting the results of Agate and Buckell (1949), since they also determined the excretion on one day only for each police officer. The second

significance

’

! I

!

379 PRESENT INVESTIGATION

We felt that further information was advisable before the use of mercury with chalk (B.P.) in the detection of fingerprints, particularly since, in spite of the practice being world-wide, no severe case of mercurial poisoning from this cause could be traced. This work was undertaken to find out whether any effect could be detected clinically in men investigating fingerprints with. the mercury powder. The best indication of the probable amount of mercury ingested seemed to be the amount excreted in the urine. Buckell et al. (1946) and other workers have concluded that the bulk of the mercury is probably absorbed through the skin or finds its way into the body by the mouth. The mouth is probably the main source of the intake, and one may assume that the mercury gets to the mouth mainly from the hands via the food. No reliable published figures could be found to correlate the amount excreted in the urine with the quantity ingested, but probably at least a rough relationship exists. Even in cases where the excretion and therefore probably the intake are comparatively large the actual amounts are really very small. Large variations in the daily intake are therefore to be expected, since 1000 µg. of mercury with chalk, containing 330 ug. ofmetallic mercury, is a scarcely visible quantity, and the contamination of the hands and therefore possibly of the food is largely accidental and must be extremely variable. Obviously the amounts of mercury ingested and excreted may bear little relationship to the total amount of exposure to the powder, especially when judged by a single test of the excretion. Much must depend on the technique of using the powder, cleaning the hands and clothes, &c. Two officers, A with twelve years’ and B with nine years’ experience in dusting," volunteered to help in’the investigation and agreed to provide material for examination. Twenty-four hour specimens of urine were taken from both at intervals over a few months to find whether the absorption of mercury, judged by the excretion, could be related to the amount of work done, and whether the amount found could be classed as excessive. It was also decided to try simple means to reduce the intake and to determine if the effect of such No erethism, stomatitis, means would be demonstrable. or tremor was found in either volunteer. This was confirmed by Prof. R. E. Lane, of the department of occupational health in Manchester University, and Dr. J. F. Wilkinson, of the department of haematology, Manchester Royal Infirmary, who made independent examinations. Specimens of handwriting and free line-drawing were without fault. The twenty-four hour samples were taken during ordinary working periods except where otherwise indicated. The process for the determination of the mercury was substantially that given by Milton and Hoskins (1947). The results were as follows :

condemning

11

-

It

A

that the higher figures of to the fact that he performs duty in civilian

thought possible

was were due

of crime during the day, with the clothes he continues the other hand, does most of his work

clothes and visits

scenes

probable further absorption from to

wear.

B,

on

in uniform inside

police headquarters. DISCUSSION

From Nov. 8 to Dec. 28, 1949; no special precautions during " dusting " were taken, the methods being those used by these officers for many years previously. These figures therefore give a picture of the absorption which had been taking place for years. In the case of subject A four samples taken during ordinary working periods gave an average daily excretion of 425 µg., and subject B five samples similarly taken gave 152 µg. daily. It should be emphasised that, though these figures probably represent fairly closely the average excretion, excluding holiday periods, over many years, there were no clinical signs of mercurial poisoning. It is evident that the rate of excretion rapidly follows the rate of intake, since the excretion fell to almost normal proportions after six days’ holiday in the case of A and four days’ holiday in the case of B. After a week’s wearing of overalls during the actual use of the powder and with more careful washing of the hands the findings for each officer were lower than any previously obtained during full working periods. In the case of A the figure was less than half of the previous average, and in the case of B it was two-thirds. The two further samples taken fifteen days and thirty-five days after the start of these simple precautions gave very low figures. Probably the powder previously deposited on the clothes, &c., had been removed by this date. The excretion of A was then about the same as the higher results found by Buckell et al. (1946) in normal people who had no known contact with mercury, and in the case of B well below that of many persons with no known contact. Mercury can cause chronic poisoning but, apart from hypersensitivity and/or idiosyncrasy, only when the intake or absorption exceeds a certain, as yet undetermined, amount. It is evident from the work of Buckell et al. (1946) that mercury in appreciable quantities is excreted by most, if not all, the population, and therefore there must be an intake of mercury, probably in the food. The quantitative factor therefore becomes of paramount importance. Buckell et al. found in fourteen normal no known with (1946) persons contact with mercury in any form a daily range of excretion from 5 to 90 µg., average 31-5 µg. These figures are similar to those observed by us, who obtained a figure of 21 µg. for the average daily excretion in one person. Mercury in various forms has been and is often used medicinally, often over very long periods. A normal dosage for certain purposes would be about gr. 1 (64,800 (Jt.g.) weekly for twelve weeks, a total of about 800,000 µg. Symptoms of mercurial poisoning which then occasionally occur are regarded as indicating hypersensitivity. It is therefore evident that the normal human body detoxicates small quantities of mercury throughout life, and can for fairly long periods deal with comparatively large amounts. We do not wish to belittle the danger of chronic mercurial poisoning in those who regularly handle mercury in any form. We feel, however, that valuable information about the probability of such poisoning can be obtained by estimating fairly often the daily excretion of mercury by such people. The two police officers who were examined have been responsible for all the fingerprint work in the area, and have used grey powder exclusively for many years. They have shown no clinical sign of chronic mercurial poisoning in spite of an average daily excretion of 425 µg. and 152 µg. Simple precautions reduced this excretion to daily averages of 89 (1.g. and

ct 3

380 41 pt.g., which are within the limits observed in persons without any known contact with mercury. We consider it desirable that clinical observations should be made and the urinary excretion of mercury estimated over a considerable period in each of a large number of cases before conclusions are drawn about the possible dangers of chronic mercurial poisoning, particularly in fingerprint detection.

have been observed only in patients with obliterative vascular disease, again with conflicting results, and have not been subjected to direct experiment. Direct measure. ment of changes in the collateral circulation in patients has not yet proved feasible, and in animals such long-term investigations are admittedly difficult and have not been undertaken. ,

SUMMARY

PREVIOUS INVESTIGATIONS

Two police officers heavily engaged for years in fingerprint detection with mercurial powder were examined. No clinical signs of mercurial poisoning were detected by several independent observers. The average daily urinary excretion of mercury over a period of two months with no precautions was 425 ;jt.g. and 152 µg., excluding holiday periods. By care in washing the hands and the wearing of overalls these amounts were reduced by three-quarters. It is suggested that, before the use of mercurial powder for fingerprint detection is considered as representing a definite risk, fairly protracted observations should be made on each of a large number of people who are prepared to exercise care in taking simple hygienic measures. There is some evidence that the urinary excretion of mercury can be used to supply information about the amount ingested. REFERENCES

Agate, J. N., Buckell, M. (1949) Lancet, ii, 451. Buckell, M., Hunter, D., Milton, R., Perry, K. M. A. (1946) Brit. J. industr. Med. 3, 55. Milton, R. F., Hoskins, J. L. (1947) Analyst, 72, 6.

EFFECT OF VENOUS OCCLUSION ON PERIPHERAL ARTERIAL BLOOD-FLOW JOHN R. VANE† JESSE E. THOMPSON* M.D. Harvard From The Nuffield Institute

B.Sc. Oxfd

for

Medical

Research, Oxford

INTERMITTENT venous occlusion, by means of a pneumatic cuff placed round the thigh was introduced in 1936 by Collens and Wilensky for the treatment of patients with obliterative vascular disease. The rationale was that the reactive hyperæmia which follows release of the occluding pressure (Lewis and Grant 1925) might promote the development of the collateral circulation. Collens and Wilensky used intermittent venous-occlusion pressures of 30-90 mm. Hg, with a cycle of two minutes on and two minutes off, and they reported beneficial results in a high proportion of their 124 patients. Since its introduction numerous other investigators have examined the therapeutic effects of intermittent venous occlusion in man, yet there does not seem to be any unanimity about its efficacy. Whereas Collens and Wilensky (1937), Brown and Arnott (1937, 1938), Evoy and de Takats (1948), and Linton (1949) have found it beneficial in the treatment of vascular disease, Allen et al. (1946) and Smithwick (1949) consider it to be of little or no use. Among those who use the method and find it helpful some believe it is of value only in acute arterial emergencies, such as embolism and thrombosis, while others use it also in chronic conditions. SUPPOSED EFFECTS

Two types of vascular change have been supposed to result from intermittent venous occlusion : (1) the acute effects, which include the changes occurring during the period of occlusion and immediately after its release ; and (2) the chronic effects, which may include the changes occurring in the collateral circulation to the limb over a

long period.

The acute effects have been investigated in man and The chronic effects animals with conflicting results. *

During the tenure of

a

T During the tenure of

a

Rhodes scholarship and a Fulbright grant. grant from the Medical Hosearch Council.

Methods used for examining acute effects of intermittent venous occlusion on arterial blood-flow are of two types : (1) the first has been designed to study the circulation in man by various indirect methods when venous occlusion is applied for a limited time; and (2) the second has been designed to study the circulation in laboratory animals by measuring the arterial bloodflow directly during and after short periods of venous occlusion. Allen and McKechnie (1937) studied the effect of inter. mittent venous occlusion on the surface temperature of 19 patients with and without arterial disease, and could find no evidence of significant or consistent vasodilatation resulting from the procedure. Veal and McCord (1939), testing blood-oxygen changes in 11 healthy males after intermittent venous occlusion, con. cluded there was no increase in the rate or volume of blood. flow, and that a true reactive hypersemia was not produced. Abramson et al. (1941), using a plethysmographic method, found no increase in blood-flow either during or after venous occlusion in the leg or forearm, but sometimes observed a slight increase in the hand and foot. Friedland et al. (1943) and et al. (1948), using

Halperin

capillary microscopy, skin-temperature readings, plethysmography, and venous blood-oxygen differences in human patients, concluded that blood-flow in the limbs is not increased during venous occlusion but is usually decreased. They postulated two causes for this observation : (1) a reduc. tion in the pressure gradient from artery to vein, due to increased venous pressure ; and (2) a decrease in the calibre of small vessels in the compressed area causing an increased resistance to flow.

The evidence obtained by indirect methods in man that there is no increase in mean arterial blood-flow during venous occlusion. Linton et al. (1941) reported changes in arterial flow during venous occlusion in dogs. They used a thermostromuhr method. Venous occlusion was produced either with a pneumatic cuff placed round the thigh or by clamping the major veins. During venous occlusion the arterial inflow to the hind limb increased, and immediately after release of the occlusion the arterial flow decreased. The changes were greater when the pneumatic cuff was used than when the major veins were occluded directly. On the basis of this rather surprising result Linton et aI. recommended that the period of venous obstruction be longer than the period of release when - intermittent venous occlusion was to be used for therapy in man. As it did not appear logical that arterial inflow should increase during venous obstruction, Gregg et al. (1948) studied the problem again.

suggests

They used three different types of instruments to measure arterial blood-flow in the dog’s hind leg : (1) a Baldes-Herrick thermostromuhr ; (2) an orifice meter ; and (3) an optically recording rotameter. With the thermostromuhr they obtained the same results as Linton-i.e., an apparent increase in arterial flow during venous occlusion, and an apparent decrease following its release. With the other two methods they consistently found a decrease in arterial flow during venous occlusion and an increase on release. The thermostromuhr is a complicated device which relates the rate of blood-flow to changes in the differential temperature between two thermojunctions, the flowing blood being heated by a unit situated between the two thermojunetions. Tests by Gregg et al. (1948) have revealed serious inaccuracies in the Baldes-Herrick thermostromuhr method of measuring blood-flow, since many factors other than blood-flow influence the results significantly. " The amount of backflow in the flow pattern is particularly important since the flow pattern