The Milroy Lectures on the Hygienic Aspects of the Coal-Mining Industry in the United Kingdom
Delivered before the Royal College of Physicians of London. By Frank Shufflebotham, M.A., M.D. Cantab., J.P. Medical referee under the Workmen’s Compensation Act for the North Staffordshire District.
Mr. President and Gentlemen - In the first place, I wish to thank you for the great honour you have conferred upon me in appointing me to be the Milroy Lecturer for this year, and I specially appreciate this distinction because it gives me the opportunity of bringing before the College, as representing the medical profession, the hygienic aspect of what may be regarded as the most important industry in the United Kingdom - that of coal-mining.
Whether it be looked at from the point of view of numbers or of skilled work or from an economic aspect, it may be said that the coal-mining industry occupies the premier position of all industries in this country, and from a medical point of view the manifold problems which are associated with the coal-miner’s life and work are of the greatest scientific interest, and at the same time they affect the life and well-being of all the workers engaged in this industry. More than a million men and boys are engaged in coal-mining in Great Britain, and they are distributed in the different coalfields in the various parts of the country. The miner‘s work is peculiar in that he not only works away from the light of day, but also because he is working underground in an atmosphere which has to be artificially treated to make it possible for him to conduct his daily work, and at great depths under varying conditions of temperature, humidity, and atmospheric pressure. His work involves at daily struggle with the forces of nature, and it is common knowledge that he is subject from the very nature of his employment to conditions which make this industry one of the most dangerous in which any man can find employment.
History of the Industry
Although this country was celebrated for its mineral productions from the remotest times, we know nothing of the coal industry until the thirteenth century, although the Romans could not have been wholly unacquainted with coal during their occupation of the country.
The earliest records point to the sea coast of Northumberland and the shores of the Firth of Forth as the localities where the industry had its beginning, and in these districts the coal was found as an outcrop of the carboniferous strata. which were exposed to the seashore. In the fifteenth and sixteenth centuries successful endeavours were made to obtain coal from greater depths, and with this development the natural ventilation of the mine became a matter of difficulty, and the gases of the mine were recognized as having a poisonous effect upon the miners. It is interesting to note that the first medical man who speaks of the question of poisonous gases of mines was the famous Dr. Caius, at one time President of the Royal College of Physicians, who, writing in the middle of the sixteenth century of certain coal mines in the northern part of Britain, said: "The unwholesome vapours whereof are so pernicious to the hired labourers that they would immediately destroy them if they did not get out of the way as soon as the lame of their lamps becomes blue and is consumed."
One of the earliest records of an accident due to fire-damp is that contained in the register of St. Marys Church, Gateshead, in 1621, where reference is made to a man who was "burned in a pit"; und in 1640 an explosion is recorded in a colliery at Mostyn in Flintshire, which was sunk to the depth of between 20 and 30 fathoms. From time to time precautions of all kinds have been adopted with the object of preventing explosions, but unfortunately there has been no cessation in their occurrence up to the present day, even with the discovery of the safety lamp and the improvements which have taken place in the construction of this device from time to time. With increased knowledge and the application of science to the practice of mining, and even with the advantage of stringent mining laws and systematic inspections by trained engineers, at the present time we cannot say that the miner is free from the terrible risks.
The recent explosion at Senghenydd in South Wales has been the greatest mining disaster this country has ever experienced, 427 lives being lost, although the death roll in this case is easily surpassed by the Courrieres disaster, which took place in the North of France in 1906, when 1,100 miners were killed.
Distribution of Coalfields
The coalfields in this country are situated in the North of England, in the Midlands, South Wales, and Scotland, and there are undeveloped coalfields of considerable extent in Nottingham, South Yorkshire, and the southeast part of Kent, districts which are now given up to agriculture, but which in the near future may be coal-mining centres. In Ireland there are only between 800 and 900 employed.
The number of coal mines worked at the present time in this country approximate 3,300; 1,089,000 persons are engaged in or about the mines, of which number 879,000 work underground. Of the underground workers 50,000 are boys between the ages of 14 and 15. Of the surface workers, 210,000 in number, 6,500 are females, of whom 900 are under the age of 16. At the present time the law forbids females working underground, and the employment of women and girls on the surface is practically limited to Scotland and Lancashire.
During the last twenty years there has been an increase, steady and almost regular, in the number of employees in this industry.
Conditions of Work Underground
The conditions of work underground depend to a large extent upon the depth and the temperature of the mine. Professor Cadman of Birmingham has published observations which have been made in many mines of different depths and in different parts of the globe with the object of finding the ratio of the increase of temperature with the increase of depth. The temperature of gradient, when measured in feet per increase of 1° F., differs from 49.2 to as much as 220 ft. per degree, but the average gradient for coal mines in Great Britain works out at about 72 ft. per 1° F. The temperature of mines may also be influenced by the direct oxidation of the coal seam during the process of mining, but from a medical point of view the consideration of the temperature of the mine air read with the wet bulb thermometer is what concerns us most from a practical standpoint with regard to the working efficiency of the collier whose work lies in mines of such temperatures. In a report to the Royal Commission on Mines on the ventilation of coal mines Cadman and Walley found in many mines the wet bulb readings exceeding 80° F., and in one instance 87° was recorded.
These considerations are of the greatest importance from a health point of view when applied to mines of great depth. There are many mines in this country at the present time over half a mile deep, and in Lancashire there is one mine whose depth approaches 4,000ft. In the future, in the development of the unworked coal seams of this country, there is no doubt that the coal seams will only be obtained at increased depth.
With regard to the illumination of mines, one can only regret that with the most efficient forms of safety lamps the candle-power is so low. Speaking generally, the candlepower of the ordinary Davy lamp is only 0.12, while the types of lamps of improved pattern now generally used in coal mines rarely have a candle-power which exceeds 0.5, even when new and in a thoroughly clean condition. Electric lamps give a better light than the ordinary safety lamp, but it must be remembered that the functions of the safety lamp are not only those of illumination, but, equally important, they are the means by which in the hands of expert miners inflammable gas can be detected, and the great drawback to the employment of the electric lamp is that its only use is illumination, and therefore it can never be used universally without the concurrent use of the ordinary safety lamp.
The sanitation of mines is it question which has been entirely neglected in the mines of this country up to a few years ago, but now it is incumbent upon all colliery owners to provide proper sanitary arrangement in their mines, Through lack of sanitation, ankylostomiasis played a great havoc for many years among the coal-miners of Westphalia, Belgium, and Austria, and it was a piece of good luck for the English coal-miner that the mines of this country never became infected. An epidemic of typhoid fever which broke out among the miners at Leigh, in Lancashire, some years ago undoubtedly assumed serious proportions on account of the insanitary condition of the mines.
Considerable attention has been paid of late years to the housing conditions of miners. Mining villages have often to be created away from centres of population, and in too many instances the houses provided have been houses for miners and not homes for men, necessitating the special attention of the authorities. Where coalfields existed there soon arose a large number of mining villages and towns, and the vital statistics of a county were soon profoundly altered in consequence.
For instance, one may begin the subject of infantile mortality. A study of this rate in England and Wales shows that the infantile mortality is highest in the counties which are the seat of the textile industries and in those counties which are the centres of the mining industry, In the former there exists to a large extent the employment of female labour and of married women, but this factor in the case of mining can be ignored. Any inquiry into the cause of the high infant death-rate in mining communities soon leads to the consideration of the habits, and above all the domestic conditions under which the miner lives. The chief factors in the production of a high infantile mortality are poverty, intemperance, and defects of sanitation.
Poverty in the case of miners can be practically passed over as a determining agent, as it is much more likely to be secondary to other causes. The miners wage is relatively a high one, and it is significant that police proceedings for drunkenness are highest in the mining counties. This, in itself, while pointing to intemperance as a contributory factor, opens up the question of habits, which is of no slight import in the investigation of death rates, or of the sanitary conditions of the home. It may be briefly stated here that all the circumstances seem to have an interacting effect on each other, so that a vicious circle of conditions is continually in operation.
That the domestic circumstances of the miner are generally deplorable is evident from the reports of the medical officers of the mining counties in Scotland to the Local Government Board. From these reports it appears that in the counties of Midlothian, Linlithgow, Kinross, Stirling, Dumbarton, and Lanark, out of 53,355 houses occupied by miners, 18,582 (which is equivalent to 55.7 percent. of the whole) are only two-roomed tenements, while 3,866 (or 11.3 per cent.) are only one-roomed dwellings. We thus see that of the mining houses in these counties 67 per cent. of them have only either one or two rooms.
In some districts the housing accommodation is so deficient near the mine that miners are obliged to walk considerable distances from their homes to their work. This is particularly the case where the mines are situated in some agricultural districts, and in North Staffordshire and Shropshire there are many cases where the miners walk or cycle six and seven miles to and from work at the beginning and end of the shift.
The mine owners of South Yorkshire and Nottinghamshire have recognized the advantages and the necessity of better housing conditions by providing houses that are larger, more sanitary, and are built in surroundings which admit of a freer and better ventilation, thus realizing that the social conditions of the miner form a very important part in the welfare of the whole industry.
Mortality of Miners
Accidents are the chief danger to which miners are exposed in the course of their employment, and more deaths are attributable to accidents than to any other individual cause. The Registrar-General’s returns for England and Wales have consistently shown that the coalmining industry has a. higher mortality figure for accidents than all other industries, with the exception of seamen and fishermen and general labourers in industrial districts. Dr. Tatham’s report to the Registrar General for 1908 shows the comparative mortality from various causes of all males, both occupied and retired, and the corresponding figures for coal-miners.
Mortality Figures from Accidents.
All occupied males . . . . . . . . . . . . . . . . . . . 100
Platelayers, railway labourers, etc. . . . . . .158
Railway engine-drivers, guards, etc. . . . . 174
Dock and wharf labourers . . . . . . . . . . . . . 185
Coal-miners . . . . . . . . . . . . . . . . . . . . . . . . . 212
General labourers in industrial districts . 209
Bargemen and lightermen . . . . . . . . . . . . .407
Seamen, etc. . . . . . . . . . . . . . . . . . . . . . . . . .459
From this table it appears that the mortality figure from accidents is more than twice as great as the figure for accidents for the whole male community, which, of course, includes miners, and among miners it is nearly twice as great as that of diseases of the respiratory system. The lives of railway workers and dock and wharf labourers appear to be no great advantage as compared with that of a coal-miner.
It is, however, very satisfactory to note that among colliers the mortality figure from accidents has diminished by 25 per cent. during the last ten years. Coalminers appear to suffer to a large extent from diseases of the lungs; on the other hand, the death-rate from tuberculous phthisis is abnormally low, and it should be noted that deaths from alcoholism and diseases of the liver and of the kidneys are very much below the average of occupied men in this country. Further, while the figures due to accidents are abnormally high, the "mortality figure " from all causes of death is only 88 for coal-miners, as compared with 100 for all occupied males, indicating that as far as "mortality figures" show, the coal-miners occupation compares favourably with that of the average worker.
From one cause or other in the last ten years 12,750 men and boys have been killed in the mines of this country. The average for these ten years is greater than the average for any of the three previous decades, but, if one estimates the death-rates from accidents per 1,000 persons employed, we find that for the last ten years, from 1903 to 1912, the average is 1.33. and it is lower than it has ever been before in any decade.
Between 1893 and 1902 the average was 1.39
Between 1883 and 1892 the average was 1.81
Between 1873 and 1882 the average was 2.24
The figures relate to all employed persons in and about collieries, including those who work on the surface. If one reviews the death-rate among underground workers only, one finds that the death rate per 1,000 is higher:
1873 to 1882 2.57
1883 to 1892 2.01
1893 to 1902 1.52
1903 to 1912 1.46
When one compares the death-rate from accidents per 1,000 persons employed in the principal mining countries in Europe - France, Prussia, Belgium, and Great Britain- and after remembering that 1906 was an abnormal year in France owing to the Courriéres disaster, the figures show that death from accidents in mines in France is less than it is in both Prussia and Great Britain, and the figures for Prussia seem to be extraordinarily high as compared with those of the three other countries.
Further, during the past thirty years there has been a great improvement in the death rate from accidents per million tons of mineral obtained, the figures being as follows:
Average Death-rate Per Million Tons.
1873 to 1882 ......... 7.42
1883 to 1892 ......... 5.65
1893 to 1902 ......... 4.7
1903 to 1912 ......... 4.76
This table shows very little improvement in the last ten years, but this apparent state of things is due to the fact that in 1905, 1909, and 1910 there were explosions of either fire-damp or coal dust which caused death to over 100 people, and as a result the figures for the last ten years have been materially swollen.
The official statistics do not show the number of non-fatal accidents which occurred each year prior to 1908, but in the years from 1908 to 1912 no less than 771,500 work-people were injured in the mines to such an extent that they were incapacitated from work for more than one week, and in the year 1911 the figures rose for that year
alone to 166,615.
For every million tons of coal that is brought from the mine to the surface, between four and five persons are killed and more than 550 are injured, and, speaking generally, 17 per cent. of underground workers are injured every year in the pursuit of their employment.
The number of accidents, both fatal and non-fatal, for the year 1912 shows a reduction in all the coal districts in England, and this is due to the fact that during the coal strike the majority of the pits in the country were closed for six weeks.
Causes of Accidents
The chief source of both fatal and nonfatal accidents in mines is due to falls of ground, that is to say, falls of the roof or sides in the working places or roadways of the mines. One can say that for many years fatal accidents due to this cause constitute nearly one-half of the total number of fatal accidents which take place underground. The same thing may be said of the non-fatal accidents which occur in mines.
Next to falls of ground, haulage accidents of various kinds and shaft accidents occupy the most important position, and the number of deaths and injuries produced by explosions of fire-damp or coal dust is comparatively small in number.
Among other causes of accidents, one must mention those produced by explosives, eruptions of water, electricity, machinery, and underground fires, as well as those which occur on the surface.
The Nature and Severity of Non-Fatal Accidents
It has been found that in addition to 1,200 or 1,300 men being killed in the mines of this country each year, more than 160,000 each year are injured by accidents which are not fatal. From the information gained by statistics drawn up by the Home Office in connexion with the Workmen’s Compensation Act, we learn that a greater number of persons are disabled for two to four weeks than for any other stated period. In 1910, 80,000 persons were disabled for this period of time, and in 1911, 86,000 were so disabled. Roughly speaking, 50,000 miners are injured every year in such a way as to incapacitate them for work for between one month and three months. The number of injuries which cause incapacity between one week and two weeks is extremely small, being about 8 per cent. of the total; but almost as important as the yearly death-roll is the number of miners who are incapacitated each year, and who have not recovered at the end of one year. This number amounts to something like 12,000 a year. This large number does not only represent so many broken bones or lost limbs, but it includes many diseased conditions, directly set up as a result of the injury they have sustained, and medical men who work in colliery districts have almost daily experience of the effect of trauma as a causation of disease or the aggravation of some pathological condition which had previously existed. I feel that we are only beginning to understand to what extent trauma does influence disease, and in the mining districts we have a great mass of material upon which observations can be made in this direction.
Injury and Disease
In concluding the lecture, I wish to speak of the subject of disease set up or aggravated by accident, with special reference to the influence of injury upon tuberculosis, not only because of the many thousands of people who are afflicted with this disease, but also because of the far-reaching effects of injury upon the onset and course of this disease. Briefly, one may say that tuberculous arthritis may be set up as a result, or certainly be aggravated as a result, of an injury to a joint; a crushed chest may be regarded as the beginning of tuberculous pleurisy or phthisis; or an injury such as a strain, apart from more violent injuries, may aggravate a tuberculous condition of the lungs, so as to even result in a fatal issue; and in cases where tuberculous meningitis has followed a blow on the head or where tuberculous peritonitis has dated back to an injury of the abdomen, one can reasonably infer that there is some direct connexion between the original injury and the subsequent pathological condition. In the same way, periostitis, nephritis, cystitis of a tuberculous nature, may in certain cases be said to result from an injury to the region of the diseased part; and undoubtedly trauma may play a prominent part in the etiology of Pott’s disease of the spine. We thus see what an important part injury plays in the onset and course of tuberculosis, and the same may be said of many other diseases.
The sedentary life imposed on a miner by an accident might produce, in those who have previously led vigorous lives, fatty degeneration of the muscles and even of the heart; gout and rheumatism may be set up as a result of the same cause, and it is common experience among medical men who practise in a mining district to find that enforced sedentary habits among miners frequently lead to indigestion, constipation, and haemorrhoids.
I feel I cannot leave this subject without referring to the various nervous diseases which may result from accident or injury. The influence of injury upon diseases of the nervous system has been more fully considered than that on any other part of the human body. Pearce Bailey has written an exhaustive work upon this subject, and he gives us not only the benefit of his own experience, but he examines all the literature upon this important subject, and he comes to the conclusion that trauma has a decided influence upon the causation of many well-known recognized nervous conditions, such as neuralgia, neuritis, locomotor ataxy, paraplegia, disseminated sclerosis, paralysis agitans, epilepsy, insanity, and the functional conditions which we know as hysteria and neurasthenia.
The commonest nervous sequela of all kinds of injuries among miners is neurasthenia. I do not suppose that there is any class of men so liable to this condition as colliers, and I attribute this frequency to the dangerous nature of the collier's work and to the influence of heredity. There is no industry where heredity plays such an important part as in the mining industry. Officials and workmen alike are sons and grandsons of those who have worked in the pits before them. The risks to which the miner is subject must have some effect upon his nervous system, and his appearance going to work shows a marked difference from the appearance of workmen engaged in other industries. Pottery employees are found early in the morning whistling and laughing as they go to work, but my experience of colliers is that their facial expression indicates mental sadness, although the collier would probably deny that that was so. As far as I can judge, a miner‘s frame of mind on going to work is one of unconscious apprehension, and the effect of this mental condition from one year to another, and from one generation to another, has an important influence, in my opinion, upon the etiology of neurasthenia in this class of men.
Want of Proper Treatment
The nature of the work and heredity are the two pre- disposing causes. The exciting cause is some injury, generally an injury to the back, of a comparatively trivial character, and I believe that the neurasthenia in many cases is a direct result of want of proper treatment in the early stages of the injury As a rule, a miner who sustains a sprained back is treated with some local application, either of the nature of plaster or liniment; he is under the treatment of either his club or panel doctor, or he may attend very occasionally the outpatient department of a local hospital. But, apart from this, he has no treatment, and he simply loafs about with a stiff and painful back, and soon develops a neurasthenic condition. If these patients were treated at the very onset with massage and movements, their incapacity for work would be extremely short in the vast majority of cases, and the men would return to work without having contracted an functional nervous symptoms. Want of treatment is most disastrous to the man, to his family, and to his employer, because when neurasthenia is definitely set up in these cases the treatment which would deal satisfactorily with his condition is not at the man’s disposal. In these cases only Weir Mitchell treatment is of any avail, yet how seldom can a miner working in mining districts, remote from great hospital centres, have the advantage of what is the only treatment which will result in an efficient cure!
I have seen so many of these neurasthenic cases in North Staffordshire that I feel convinced that malingering plays practically no part in this class of case, and it should not be forgotten that one attack of neurasthenia, even if the condition improves to such an extent that the man is able to resume some form of employment, may predispose to another attack, even after a slight injury, and on one occasion I saw a coal miner with typical symptoms who had met with no injury at all ; he had been working with another man as his companion in a new cutting when the roof fell in and injured his fellow-worker, and the uninjured man was so upset at this occurrence that he became very nervous, and within a few days he presented characteristic symptoms of neurasthenia. [The British Medical Journal, Vol. 1, No. 2774 (Feb. 28, 1914), pp. 467-470]
Causes of Explosions.
Up to a comparatively short time ago colliery explosions were attributed to the inflammability of fire-damp; but in a modern well-ventilated mine, while the explosion of fire-damp may be the initial agent, it plays practically no part in the actual explosion in the workings. An explosion can be produced readily by firing a mixture of coal dust and air, and the proportions necessary to form an inflammable mixture are, roughly speaking, 1 lb. of coal dust to 160 cubic feet of air.
Coal Dust Watering.
The finer the coal dust the more explosive. While fire-damp explosions begin at the working face, coal dust explosions usually take place in the main haulage roads. The coal dust may be ignited either by blown-out shot (a shot that had been put into the hole in such a manner as to be blown backwards without blasting the rock or coal), or by the exposed flame of a broken safety lamp, by a fused electric cable, or by sparks emitted from coal-cutting machines. In other cases, however, there has been an initial explosion of fire-damp at the working face, carried through the workings by the ignition of coal dust, and a large number of explosions have been caused through the ignition of fire-damp by naked lights in pits where safety lamps are not employed.
Fire-damp explosions can be and are prevented by improved methods of ventilation and by the early detection of the fire-damp in small quantities by means of the cap over the flame of the safety lamp. In considering the prevention of coal dust explosions, the first problem is how to prevent the accumulation of coal dust. The presence of coal dust is inevitable in a mine. The removal of dust by periodical sweeping of the roadways, sides, and roof has been advocated, but a more effective method is by watering the roadways, a method practised for some years in Germany and Belgium, and successfully adopted in many mines in this country. It is necessary to water the sides and roof as well as the roadways. It is, however, the general opinion that watering can never, for various reasons, be universally adopted, and spraying might under certain conditions have an injurious effect upon the miners’ health. Again, falls of ground are more numerous in wet mines than in dry. Dust removal and spraying may be of some use, but they do not entirely remove the danger, though it may be hoped that as a result of the Government experiments at Eskmeals a possible remedy is near at hand.
The poisonous gases found naturally in mines are black damp, fire-damp, carbonic acid, and, in small quantities, sulphuretted hydrogen and sulphurous acid; as a result of explosives we may also find oxides of nitrogen. Carbon monoxide is invariably generated as the result of an explosion, whether of fire-damp or coal dust.
This is the residual gas after oxidation of materials present in the coal, oxygen of the air being taken up with the formation of carbonic acid. It is found more or less in all mines, and always in the return air of the upcast ventilating shaft.
The composition of black-damp varies under different conditions, but, speaking generally, it is a mixture containing about 87 per cent. of nitrogen and 13 per cent. of carbon dioxide. It is probably formed in the process of oxidation of iron pyrites which is present in the coal. This sulphide is oxidized to sulphuric acid and sulphate of iron, and as calcium carbonate in the form of calcite is also present in the coal, calcium sulphate is formed with the liberation of carbonic acid, and, according to Haldane, the process may be represented by the following equation:
4FeS2 +15O2 + 8CaCO3 - 8CO2 + 8CaSO4 +2Fe2O3
Black-damp as a rule has a greater specific gravity than air, and consequently is found on the floor in low-lying workings, but there are cases in which black-damp is lighter than air, cases in which the black-damp contains less than 5 per cent. of carbonic acid (Cadman), or when it is mixed with other gases, such as fire-damp. When there is an accumulation of black-damp lighter than air it is most important that it should not be examined except with a safety-lamp, on account of the possibility of the presence of fire-damp. With a falling barometer the percentage of black-damp may be very greatly increased, and to such an extent in some workings that it is necessary for the miners to suspend their operations.
This gas is recognized by the safety lamp from the fact that when present in small quantities the flame will only burn dimly and when in larger quantities the flame may be extinguished altogether. This is due to the lack of oxygen, and not to the presence of carbonic acid.
The effects of black-damp on the human subject are due to the presence of carbonic acid and the deficiency of oxygen. The initial symptoms are shortness of breath, quickened pulse, and increased respiration-rate, followed by headache and giddiness. If the victim is unable to get away he may be overcome with drowsiness, and if the black-damp be of sufficiently high percentage he may become insensible and eventually die. Before death there may be marked cyanosis, and the heart may continue to beat for some little time after the breathing has stopped. Death is always due to suffocation or to injuries produced as the result of a fall when the miner is overcome by the gas.
Treatment. - It is most important to get the victim into pure air as soon as possible, and if breathing has stopped, artificial respiration should be resorted to without delay. If the heart has not stopped and oxygen be administered at the same time there is every chance of recovery. Lf oxygen be available in the pit the rescuer should administer the gas to the sufferer if he be unconscious without removing him, and artificial respiration should be carried out by a colleague.
The post- mortem appearances due to black-damp poisoning are similar to those of asphyxia.
The constitution of fire-damp is at the present time a matter of controversy. Dr. Haldane holds that it is pure methane, and he has found that the firedamp met with in lead mines, shale mines, and the Cleveland ironstone mines has also reacted as pure methane On the other hand, Le Chatelier finds that firedamp in French coal mines apparently consists of two constituents, one of which is combustible and the other non-combustible, the former constituting in some cases about 95 per cent. of the whole. Chamberlin, in the United States, has found that, in addition to methane, paraffines and olefines are also present in small percentages, and in Germany, associated with certain kinds of coal, ethane is also said to be found as a constituent of fire-damp. Methane (CH4), a completely colourless and odourless gas, exists in the coal seams at a high pressure, which sometimes may be as great as 400 lb. to the square inch. The air in abandoned workings often contains a considerable, percentage of methane, derived not only from the coal, but from the decomposition of old timber props.
The specific gravity is 0.559, air being 1, and thus the gas is always found in the highest places of the mine. It burns with a bluish flame, and when mixed with air forms an explosive mixture, the explosive character of which varies with the proportions of the two gases, the most explosive mixture being reached when methane forms about 10 per cent. of the mixture with air. The lower limit of inflammability is 5.5 per cent. of fire-damp in a mixture of methane and air, and this limit seems to be pretty well established; the upper limit of inflammability does not extend beyond 15 per cent., and the combustion in many instances may not be complete when the proportion is greater than 13 per cent. of methane. No explosion can take place in a mixture of methane and air if the temperature of the flame be lower than 740° C. The limit of inflammability will depend to some extent upon the atmospheric pressure, and by increasing the pressure a mixture containing less than 5.5 per cent. of methane may become explosive, and conversely if the pressure be diminished a mixture containing a greater percentage of methane than 5.5 may not explode.
When methane is present the flame of the safety lamp flickers and a pale, non-luminous, slightly blue cap is seen above the ordinary flame. The observations and experiments of Professor Cadman have made it possible to estimate roughly the percentage of methane in mine air by measuring the height of the cap as compared with a test flame of a standardized and measured height. His observations when recorded in an atmosphere containing 3.7 per cent. of fire-damp show as follows:
Height of Testing Flame in Inches . . . . .Height of Cap in Inches.
0.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.85
0.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1
0.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4
0.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.75
0.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cap not seen; testing flame too luminous.
While a mixture is not inflammable unless 5.5 per cent. of methane is present, methane can be detected by means of the luminous cap when it is present to the extent of only 1 per cent.; but it is impossible to see the tip of the cap unless at least 2 per cent. of methane is present in the mine air.
Fire-damp has no direct deleterious effect on man. It simply dilutes the oxygen of the air so that its action may be regarded as the same as that of nitrogen, or, to put it in other words, it is due to deficiency of oxygen. Life is not endangered until the percentage of fire-damp reaches somewhere about 70, although when the percentage is between 40 and 50 the respiration-rate and the pulse rate will be increased, and there will be palpitation of the heart, cyanosis of the face, and pronounced muscular weakness. Fatal accidents sometimes result from miners walking into an accumulation of pure fire-damp.
When the mine air contains fire-damp to the extent of 5.5 per cent., or the lower limit of inflammability, even if there is no explosion, the dame of the safety lamp is extinguished; this fact is an indication of the presence of fire-damp, and should be of great use to exploring
Treatment. - The treatment of poisoning by fire-damp consists in restoring the patient to pure air, and the application of artificial respiration in severe cases. Oxygen should be applied wherever available in all serious cases.
The post-mortem appearances after poisoning by fire-damp are not unlike those found in cases of black-damp poisoning; they are those of asphyxia.
This term is applied to the gases after an explosion. Haldane has described it as a variable mixture of nitrogen, carbonic acid, and carbon monoxide, together with air ; in dust explosions there may also be present a little sulphurous acid or sulphuretted hydrogen and various products of the dry distillation of coal. While sulphurous acid and sulphuretted hydrogen are highly poisonous bodies, still the deleterious properties of after-damp are undoubtedly due in nearly every case to carbon monoxide. After-damp may be found under several different conditions as a result of incomplete combustion, as from a gob-fire, or as a product of combustion of a blasting explosive.
When fire-damp ignites in the presence of an excess of air, carbonic acid and water are formed, but when the proportion of air is not sufficient for complete oxidation, carbon monoxide is produced as well as carbonic acid. We may infer from port-mortem observations that death in the vast majority of cases is due to carbon monoxide poisoning, and that, speaking generally, there is never sufficient air to bring about complete oxidation. When sulphurous acid or sulphuretted hydrogen are present the after-damp acquires a characteristic and unpleasant smell, but otherwise it is odourless. Carbon monoxide has an affinity for haemoglobin which at the ordinary body temperature is more than 300 times greater than that of oxygen, producing the stable body carboxyhaemoglobin. The effect of the gas is cumulative; 0.4 per cent. in the air will produce a fatal result if the air be breathed for a sufficiently long time, but after an explosion from 2 to 5 per cent. of carbon monoxide is generally found and as a consequence death rapidly ensues. Leonard Hill regards 0.05 per cent. as the highest allowable limit at after-damp in the atmosphere of a mine. Pure carbon monoxide burns in air with a bluish flame, but when diluted to the extent found in after-damp a naked candle and a safety lamp will continue to burn in it. After-damp is best detected by means of a mouse or a small bird, such as a canary, either of which will show symptoms of poisoning very much sooner than the human owing to the rate of metabolism in these small animals being very many times greater than that of man.
Symptoms.—The symptoms of carbon monoxide poisoning depend upon the amount of gas inhaled and the amount of carboxyhaemoglobin formed in the blood. If the air, contain only a small percentage of the gas the symptoms are headache, nausea and palpitation, and shortness of breath and giddiness on exertion; with a larger amount of gas headache may be accompanied by singing or buzzing in the ears and throbbing of the temples, but the most striking symptom is always muscular weakness. If the gas be present in the air to the extent of 0.05 per cent. the limit which Dr. Hill has laid down, slight giddiness results after inhaling it for half an hour; if carbon monoxide be present to the extent of 0.1 per cent. there is inability to walk after half an hour; if 0.2 per cent. be present there is loss of consciousness after half an hour, and with 1 per cent. loss of consciousness results after a few minutes and death rapidly ensues. Drowsiness, and even unconsciousness, occur in a large number of non-fatal cases. and in fatal cases death may be ushered in by convulsions and coma. Exposure to this gas in cases which recover may produce a deep-red blotchy appearance of the face, which has been noticed for as long as fourteen days after the explosion, and in some cases the characteristic rosy flush which is associated with carbon monoxide poisoning has been observed. Chauffard has found an extreme exaggeration of the olecranon reflex, while the knee-jerks were not exaggerated to the same extent, and he noticed that Babinski’s sign was positive on both sides. Sometimes we find incontinence of the bowels and retention of the urine, and transient glycosuria may be observed for a few days. The pupils may be fully dilated and insensible to light, and Ruata records as a symptom acute delirium, which in one case lasted for five days.
Examination of the Blood.- If blood be saturated with carbon monoxide it has a bright scarlet or cherry colour, but the blood from the body of a man directly killed by carbon monoxide has a dark purplish-red colour, the dark colour being due to an admixture of carboxyhaemoglobin with reduced haemoglobin. On spectroscopic examination blood which contains carbon monoxide shows two definite observation bands between D and E. lf the blood be saturated with carbon monoxide, the addition of ammonium sulphide produces no effect, thus differing in this respect from healthy blood. Haldane has devised a colorimetric test which is both simpler and much more delicate than the spectroscope. A drop of blood from a patient who is supposed to be suffering from carbon monoxide poisoning is diluted with about a hundred times its volume of water, and compared with a solution of the same depth of colour from normal blood obtained from the lobe of the ear or a prick of the finger. Part of the solution of normal blood is saturated with coal gas and changes from yellow to pink. We thus have three solutions: (1) The solution of blood from the supposed case of carbon monoxide poisoning, (2) a solution of normal blood diluted to the same extent as No. 1, and (3) the normal blood through which coal gas has passed. These three solutions are then poured into narrow test tubes of equal diameter, and a comparison is made. If the depth of colour of the first solution appears to be greater than that of the other two solutions water must be added until the tints are exactly the same, but if the depth of colour is less than the two solutions then a few more drops of blood are added for the same purpose. We are now able to compare the tints of the three solutions, and a rough estimate can be made of the degree of saturation by noting the amount of water or blood, as the case may be, which it has been necessary to add to the first solution to ensure the same depth of colour. Normal blood, when diluted with water, is yellow in colour, while blood containing carboxyhaemoglobin is pink, and it is upon this observation that the colorimetric test is made.
Notes on After-damp Poisoning at Senghenydd.
I paid a visit to Senghenydd two days after the terrible explosion which occurred there in October, 1913, and had the opportunity of examining many men who were rescued from the pit on the day following the explosion. The principal clinical features of these cases were that in those who had been badly gassed the pulse-rate was most irregular, not only as regards frequency, but as regards volume and character, and examination of the pulse gave no indication of the physical condition of the patient. At one time the pulse might be slow, feeble, and irregular, apparently the pulse of a patient slowly sinking; but, without apparent cause, ten minutes afterwards the pulse would be of normal rate and would have materially improved in quality. Dr. Philip James of Senghenydd, the principal medical officer to the colliery, told me that this was a special feature of these cases, and it made it impossible to give a correct prognosis to the friends of the patient.
The large majority of these cases showed large crythematous patches of a bright cherry colour with clearly defined margins, but of irregular shape; they varied in size from areas of 6 in. long by 4 or 5 in. broad down to areas 1 1/4 in. long by 1/2 in. broad. They were tender and tense, with a considerable amount of induration around the patches. The patches were principally located upon the buttocks, sometimes only on one side. When both sides of the buttocks were affected the patches were not symmetrical. I am not aware that this condition had been described before, and in some cases they were reported to me as superficial burns. I am sure they were not burns, not only because of the location of the rash, but also because there was no blister over any of these areas; further, some patches developed for days after the explosion. The induration was very slow in clearing up. Six weeks after the explosion the patches were smaller and the induration had subsided to a large extent, but not completely. The skin over the-patches was discoloured, and there was desquamation, while the follicles were prominent. The oedema around the patches had disappeared, and there was hyperaesthesia over the patch of skin which remained, and anaesthesia over the area of skin which had been originally affected.
The third striking clinical point was the development of peroneal palsy or ankle-drop, in many of the cases who were rescued. Previous writers have recorded paralysis of different kinds as being a symptom of carbon monoxide poisoning, but I have never found any special reference to peripheral neuritis affecting the peroneal nerve and causing ankle-drop. This symptom developed from two to four days after the explosion. The early symptoms were pains in the legs, there was tenderness along the peroneal nerve and talipes equino-varus. The peroneal paralysis passed on from the acute to the chronic stage, and in some casces I fear that the paralysis will be permanent. Six weeks after the explosion the symptoms were loss of power of dorsifiexion of the foot. In one or two instances there was complete paralysis in this respect, and in some diminished power of plantar flexion. The cutaneous reflexes were absent over the area of skin supplied by the peroneal nerve and in some cases irregular areas of skin, apart from the distribution of this nerve, were similarly affected.
After many explosions it has been frequently observed that pneumonia of a particularly dangerous type was a frequent sequela, and the Senghenydd explosion was no exception. Several of the patients developed pneumonia almost immediately they had been rescued. The temperature was very little raised, the pulse was variable in frequency and quality, the respirations were quick, and the expectoration from the onset contained blood of a dark blue colour, Examination showed irregular patches of dullness on both sides of the lung.
Retention of urine was a striking symptom in every case, and in two cases there was paralysis of the sphincter ani.
I do not propose to give details of the cases which I examined at Senghenydd, as they are being carefully observed by Dr. Ivor Davies, of Cardiff, who will shortly publish an account of the clinical aspect of after-damp poisoning.
After-effects of Carbon Monoxide Poisoning.
The after-effects of carbon monoxide poisoning are often serious, and may be so varied as to suggest the possibility that the patient is suffering from some other disease. Headache may persist for weeks, and I have known severe headache to persist for six months. Symptoms of indigestion may also persist for an equally long time. In cases which recover within a few weeks we may find that muscular weakness, pains in the legs, and aching of the knees and ankles are complained of as after effects for some days, and there are recorded cases in which these symptoms were present for a week or two after the explosion. Other noticeable symptoms are coldness, heaviness, and numbness of the legs and feet, and, occasionally, shooting pains. These symptoms are, in my opinion, due to neuritis.
The after-effects of carbon monoxide poisoning upon the human subject are entirely confined to the central nervous system. Mental symptoms, disturbance of memory, changes in the voice and speech, hemiplegia, and monoplegia all denote some toxic effect on the brain; sclerosis of the spinal cord, poliomyelitis indicate pathological changes in the spinal cord, and we have seen that peripheral neuritis is one of the most frequent sequelae of this poison, and these toxic effects produced by carbon monoxide are so similar to the toxic effects produced by other poisons that it almost seems as if toxaemia, no matter how produced, has the same effects upon the central nervous system.
A large number of miners are pale, and it is a matter of speculation whether the paleness is due to the daily inhalation of very small quantities of carbon monoxide. This peculiarity cannot be the result of working underground for forty-eight hours each week without some further cause, and it may be a subject for further observation, and even research, whether this condition might not result from breathing some deleterious gas, such as carbon monoxide, in very small quantities. I have taken blood counts of many miners, and have examined the blood for carbon monoxide, but with only negative results. Sir Thomas Oliver has questioned whether miner’s nystagmus may not be due to the toxic effect upon the central nervous system of small quantities of carbon monoxide continuously inhaled while the miner is at work in the pit.
It is important to remove the man into fresh air with as little delay as possible and without undue exertion, and it is equally important that he should be kept warm so as to diminish the risk of after-complications. In some cases artificial respiration must be resorted to, and it is generally admitted that Schafer’s method is the best. In apparently hopeless cases patients have been revived after artificial respiration has been practised for three or four hours. The artificial respiration must be carried out in fresh air on the surface and not in the vitiated atmosphere of the mine.
Oxygen is of the greatest assistance in restoring patients suffering from after-damp, but it should be warmed by passing from the cylinder into an india-rubber bag placed in a bucket of hot water; the gas may thus be brought to the atmospheric temperature or a little higher.
Wilcox and Collingwood have recommended the inhalation of alcoholic vapour along with oxygen, and they claim than this mixture has a most beneficial action on the heart. Stimulants are of the greatest use in assisting the action of the heart, and of these sal-volatile by the mouth or hypodermic injections of strychnine have been found useful; adrenalin and pituitrin have also been recommended to increase the blood pressure. Venesection and transfusion of defibrinated blood have been tried in individual cases, and Mr. William Sheen of Cardiff has recommended in severe cases, where there is unconsciousness, that the patient be transfused with defibrinated blood on one side and that venesection be carried out on the other side.
The burns very often are of a serious nature and require special care. The skin affections, especially those which are angioneurotic, are best treated with powders rather than ointments, although if there be great pain it may be necessary to apply an opium lotion.
As the treatment of pneumonia, is very largely a matter of nursing it is essential that patients should be attended by trained nurses from the very onset of the pneumonia symptoms. While Red Cross nurses may be very willing to do what they are told and may have very good intentions, unless they have been properly trained as nurses their efforts in cases such as these may be in many cases of little avail. I wish to emphasize this point because I feel that it is useless to rescue men from a mine after an explosion at great personal risk to the members of the rescue parties unless everything possible is done to save the lives of those who are rescued. There should be some proper arrangements for the immediate treatment of men who are rescued from explosions. I suggest that a few beds should be kept in the office to meet the immediate needs of men who are gassed, that in each colliery district there should be a cottage hospital with a few beds so that ordinary accidents may be treated in an efficient way and without delay, and then in the big centre we should have the large general hospital where serious injuries may be dealt with if no risk is incurred to the patient in removing him from the mine or from the cottage hospital.
The experience at Senghenydd clearly points to the fact that cases of peripheral neuritis will not cure themselves, and it is most important for patients to have the advantage of massage and electric treatment carried out under medical supervision and in a. systematic way at the earliest possible moment. In the Senghenydd cases the amount of damage done to the nerves by the carbon monoxide was extensive, judging from the rapidity with which atrophy of the muscles set in, and it is not sufficient in such cases for the patients to be treated at home, and probably by themselves, with simply liniments and medicines. As systematic massage and electric treatment can only be carried out in hospitals or institutions, it is most desirable that the patient be admitted for this treatment at the earliest possible moment, and before atrophy of the muscles supervenes.
The post-mortem appearances due to afterdamp poisoning are for the most part characteristic of poisoning by carbon monoxide, but they may be associated with other conditions—the bodies may be severely burned as a result of exposure to flames, or there may be extensive wounds due to falls of ground produced by the explosion. Pneumonia in some instances may be the cause of death.
Sulphuretted hydrogen may be found in mines under varying circumstances. It may be found mixed with fire-damp, or it may be found associated with gases which are given off from coal which has undergone spontaneous combustion, known as white-damp, choke-damp, or in some districts gob-stinks. It may also be a product of the chemical action of the ignition of some of the explosives. It is an extremely poisonous gas; it causes irritation of the eyes and the respiratory tract, with conjunctivitis, nasal catarrh, and pharyngitis; in severe cases there may be bronchitis, bronchopneumonia or lobar pneumonia, sometimes of a septic type.
In the case of an underground fire, smoke may be emitted in such large quantities as to be of danger to the workers, not only in the immediate vicinity of the fire but in any part of the workings where the smoke may be carried by the ventilating current. Carbon monoxide is the dangerous constituent of the smoke, although traces of sulphuretted hydrogen and sulphurous acid and nitrous fumes may also be present.
Sulphurous acid is sometimes produced in small quantities along with after-damp. It causes irritation of the eyes and of the respiratory passages; with 0.003 per cent. the symptoms of irritation are most marked, and as little as 0.001 per cent. may produce some irritation of the conjunctiva and the air passages. Apart from conjunctivitis, the most common symptom noticed after inhaling an atmosphere containing sulphurous acid is bronchitis; the expectoration may contain blood mixed with the mucus, and as a result of the violent paroxysms of coughing in severe cases haemoptysis may be noticed. In some cases we find symptoms which affect the digestive organs, and dyspepsia of a more or less severe type may be set up.
Nitrous fumes are very dangerous to life. The nitrous oxide (NO2), which is the principal irritating constituent of nitrous fumes, when inhaled and absorbed into the system, unites with the haemoglobin of the blood and displaces the oxygen. While the patient is exposed to the fumes there may be momentary symptoms of irritation, such as smarting of the eyes, cough, expectoration, feeling of suffocation, and sickness; but these symptoms may pass away for some hours; then, sometimes quite suddenly, more serious symptoms may arise—shortness of breath, cough, feeling of suffocation, cyanosis, and difficulty of breathing. Septic bronchitis and broncho-pneumonia are frequent sequelae, and the patient may die within a few days. In non-fatal cases the illness may extend over several weeks, and if the exposure to the gas has taken place in the early or mid winter there may be chronic bronchitis until the warm weather appears again. If a strip of white blotting paper be moistened with a solution of starch and a little potassium iodide and slightly acidified and exposed to nitrous fumes, even when present to a very low percentage, it becomes blue owing to the liberation of free iodine.
Rambousek says that in the treatment of patients who have been exposed to nitrous fumes the inhalation of oxygen is perhaps the most important remedy, and should always be tried. He also states that chloroform may be used, not because it produces any actual curative effect, but because some of the symptoms may be abated by its inhalation, and narcosis in this way induced.
Cases due to Explosives.
When miners are using the cartridges which contain the explosives, the men who are working at that place seek safety at some distance before the shot is fired. Gunpowder, gelignite, bobbinite, and samsonite are the four explosives most commonly used in the coal mines of this country. Gunpowder is a mechanical mixture of sulphur, potassium chlorate, and charcoal, and when it explodes gives of carbonic acid and nitrogen in large quantities along with a small quantity of sulphuratted hydrogen and carbon monoxide. Gelignite is a mixture of nitroglycerine and sodium nitrate, and contains 65 per cent. of the former body. On detonation it gives off carbon monoxide. There are two kinds of bobbinite, both of which contain about 65 per cent. of potassium nitrate, from 18 to 20 per cent. of charcoal, and 2.5 per cent. of sulphur; but in one preparation there is added a mixture of the sulphates of ammonium and copper, while in the other we find a mixture of rice or maize starch with paraffin wax. With this explosive nitrous fumes and sulphuretted hydrogen in addition to carbon monoxide may be given off.
We are thus faced with the same problems in connexion with the gassing as a result of explosives as we have been in gassing after explosions. Haldane points out that the most serious accidents in mines from gases from explosives are due to the accidental burning of the explosives and not due to detonation. When these explosives burn quietly it is found that a large proportion of nitrous fumes are produced. [The British Medical Journal, Vol. 1, No. 2775 (Mar. 7, 1914), pp. 527-531]