75

H.—44a

The Mines Department publishes each year a detailed description of the facts and surrounding circumstances of individual accidents, exhibiting precisely the conditions in which the accidents occurred. This permanent and accurate record should be of great value in devising means of minimizing the number of serious accidents in the future. Judging by the evidence given by a medical officer in a large mining district the liability to alight accident is considerable. In one mine with about three hundred and fifty workers it was stated that accidents of this nature, for which miners medical officer, occurred at the rate of eighteen a month from January to August of 1918, the average duration of the patient's absence from employment on account of such accident being estimated at three to four weeks. The same medical practitioner stated that there is not much interruption of work among miners owing to illness apart from the results of accident, although he is of opinion that coal-mining makes a greater drain on the nervous and muscular systems than the work of agricultural or general labourers. There is no doubt, too, that the use of the ordinary safety-lamp has harmful effects on eyesight. The influence of their occupation upon the health and average length of life of coal-miners has been the subject of much scientific investigation abroad of recent years, to which brief reference may be , made in view of the absence of any considerable body of reliable local data. The ascertainment of the true connection between occupation and health and longevity is hedged round with difficulties, because of (i) the rapid change in medical knowledge and the power of diagnosing the true nature of diseases ; (ii) the movement of individuals from one occupation, where they may have developed the disease ultimately causing death, into a different trade ; (iii) the existence of numerous occupational diseases which do not directly cause death ; (iv) the occurrence of secondary and ultimate diseases which cover up the condition that originally caused or accelerated death ; and (v) the presence along with the occupational factors, such as coal-dust, of other factors due to locality, &c, which may vary greatly over different coalfields. Coal-workers generally show a high proportionate rate of death from accidental violence, though, as pointed out above, this rate is low in New Zealand compared with countries in general. They show a low proportionate death-rate from pulmonary tuberculosis or consumption of the lung, and this relative freedom has been proved to be the resultant of occupational conditions whicli in some manner protect coal-miners from the fatal consequence of tuberculous infection. Dr. J. S. Haldane, F.R.S., writing in September, 1.918, summarizes the more important results of recent research in Great Britain into diseases peculiar to coal-miners. He says, — " Goal-mining in Great Britain is on the whole a very dusty occupation, but there is no evidence in the mortality returns for either young or old colliers that dust-inhalation has hitherto caused appreciable danger to life in British coal-mining. The death-rate among miners from lung-disease is in England at all ages up to fifty-five not only far below the average for other employments, but even slightly lower than for farm labourers. The death-rate for phthisis alone is also slightly lower than for farm labourers. It is proved that coal-dust and shale-dust, unlike flint-dust or quartzite dust, entirely disappears from the lungs and body in time. It can be realized quite readily what is happening in the lungs of a coal-miner breathing large quantities of coal-dust and shale-dust, as compared with what is happening in the lungs of a gold-miner breathing quartzite dust. As fast as the dust goes in day by day to the coal-miner's lungs it is carried out again by the dust-cells. His lungs, it is true, are probably always more or less black ; but, on the other hand, what lie coughs up is black and full of the dust on its way out again. His black spit is in truth his salvation. On exposing the animals experimented on to relatively small daily doses of coal-dust or shale-dust, and continuing this over a long period, it was found that after a few days the dust in the lungs ceased to increase. The intake of dust was thus balanced by the output. From all that is known about similar physiological processes one may be fairly sure that the capacity for eliminating dust-particles grows with use. If this is so, the practice of constantly getting rid of coal-dust and shaie-dust may help the lungs in eliminating other kinds of harmful particles such as tubercle bacilli, and may thus account for the remarkable fact that coal-miners are, and always have been since statistics were first available sixty years ago, extremely free from phthisis." Experiments carried out in England by the Medical. Research Committee under the National insurance Act have given very reassuring results as far as coal-mining is concerned. So long as the dust in a coal-mine is not explosive, and is not breathed in excessive quantities, it seems to do no harm, and possibly even does some good. Many authorities hold that coal-dust has certain germicidal or antiseptic properties; others that it stimulates the lung-tissue and the growth of connective tissue. Goal-dust particles are round, unlike, in shape as in composition, the sharp flinty particles of stone-dust; but it is to be noted that much coal-dust contains a certain amount of stony particles, and that there is sufficient reason for pursuing the inquiry whether the excessive mortality from non-tuberculous respiratory diseases, such as bronchitis, asthma, and pneumonia, among miners is due to dust-inhalation. The occurrence of these among miners has, however, undoubtedly diminished with the improvement of mine-ventilation, and may result in part, as miners themselves often claim, from the fumes of explosives. The opinion of the Chief Inspector is that permitted explosives do not give as much noxious fumes as gelignite, and that if properly used in an adequately ventilated place they produce no noxious fumes whatever. Where the miner fires without under-cutting or side-cutting, making the explosive do much of the work which the coal-pick should have done, more explosive is used than ordinarily, and more smoke produced. In an indifferently ventilated place this would be injurious to health, and for it the men share the responsibility with the management.