Chapter XXIV: Ganister Crushing

Workers engaged in crushing basic slag, in the breaking of certain rocks, in the manufacture of millstones, in stone-mason’s work and kindred occupations, are peculiarly liable to chronic inflammation of the air-tubes, caused by the inhalation of dust of an irritant kind. This, it is believed, leads to lung fibrosis. Where the operatives form part of a large community in which individuals are employed in many and varied trades, it is conceivable that fibrosis of the lung may be mistaken for tubercular pulmonary consumption, and it may not be realised that the cause is due to the occupation of the sufferer. The late Dr Arlidge, in a public lecture on “The Sanitation of Industries and Occupations,” referring to china clay as a silicious material, states that the dust is most destructive to lung function and lung integrity, as it sets up chronic inflammation of the air-tubes and of the lung tissues, itself accompanied by bronchitis and asthma. The disease thus established terminates in fibrosis of the lung, “a lesion which symptomatically closely resembles pulmonary consumption.”

The risks referred to have in late years more than ever engaged public attention. Already great strides have been made in the provision of remedies. To medical men practising in districts where these dusty trades form the principal occupation, we may look for information of a definite and exact nature as to the health of the workers. A highly interesting article, entitled “Ganister Disease,” was published in the _Journal of the Sanitary Institute_ for April 1900. The writer, Dr C. L. Birmingham, lived for several years in the valley of the Don, the principal centre of this mining industry.

To the general reader it may be well to explain that ganister or calliard is a hard, close-grained, silicious stone which often forms the stratum that underlies the coal seam. A footnote in Dr Percy’s _Fuel_ says--“Dinas rock is believed to be a millstone grit of the carboniferous system, and the geological equivalent of the bed termed ‘Ganister’ at Sheffield.” It is found in Yorkshire, Durham, North and South Wales, and elsewhere. When crushed and ground into dust it is used as a fire-resistant, chiefly for lining Bessemer and other steel-converters, for the manufacture of bricks likely to be subjected to great and continuous heat, and it is sometimes mixed with, or substituted for, Stannington or other clays, which, together with ground cinders and old ground pot, are used for the manufacture of crucibles in which certain kinds of steel are made.

The persons liable to suffer are the ganister miners and those who manipulate the material in mills known as “breaker-mills.” During the mining process much dust is generated in the various stages of blasting, and little doubt exists that it is to this that we must look for a solution of the very high mortality returns. By many it is held that the products of combustion from the blasting charges are liable, when inhaled, to cause (or to predispose the worker to) chest affections. The ganister, in large lumps, is brought from the mines to the mills in small trucks running on metals. Where necessary, these lumps are broken by hand with heavy sledge-hammers, the process being known as “sledging.” Whilst this is being done a certain amount of dust arises. The material is next thrown into breaker-mills of various patterns, for crushing. The mills are in the open air, or in open sheds. As the lumps are thrown into the mouth of the mill where the crushing takes place, clouds of dry dust rise in the face of the workers, and to this operation is attributable much of the illness. Happily, a remedy generally accepted has been found and is being adopted. It is simply a jet of steam playing into the mouth of the mill, damping the material and preventing the dust from rising. In some works, small fine jets of water, such as would run from an ordinary water can, are preferred. Time has not yet allowed practical men to say with certainty that this is an absolute remedy, but they are very hopeful.

The crushed ganister, in pieces about the size of “metal” used for road-making, is carried from the breaker-mills by shoots to edge-runner mills, to be pulverised into a fine dust. During the whole of this process it is thoroughly saturated with water, rendering the escape of dust a practical impossibility. In this state it is ready to be converted into bricks, or to be taken away in railway trucks, carts, or other conveyances, for use elsewhere. It is sometimes found that the ganister mortar is too moist, in which case it is “tempered,” that is, dry ganister-dust, to the necessary amount, is mixed with it. In this process some dust may here arise, but it is hardly in sufficient quantity to affect the health of the workers.

The bricks are made in hand presses. It is not a dusty process until just before closing the press, when many operatives take a handful of ganister dust and throw it over the surface of the brick, to secure a clear and clean impress, showing the name of the maker, etc. This is a dangerous and unnecessary step; damp sawdust is equally efficacious and is now generally used. The floors of ganister brick-drying sheds, as in other brick works where the same method of drying is adopted, are more or less dusty. Under these floors there are pipes heated by steam or hot air, for the purpose of drying the bricks. Each time a dry brick is lifted, dry dust is liberated, but seeing that there is little or no traffic on these floors (except in passages, which can easily be kept clean), the dust rests on the floor, and does not permeate the atmosphere. Mechanical fans have been suggested, but practical men would find it extremely difficult, if not impossible, to find any fan that would carry this dust, and such men certainly would be sceptical as to the wisdom of creating draughts where the desire is to keep the dust on the floor, and not to cause it to fly about. It will be realised that although fans may be, and are, used with the greatest advantage in certain dusty occupations, it does not follow that they will answer in all.

It has been stated, and probably with some degree of accuracy, that the “setter’s” work involves exceptional risk. The process consists in placing the bricks in the kilns for baking, after they have been dried in the sheds. A man standing in an elevated position catches the bricks, which are thrown to him by the man at the mouth of the kiln. As they are thrown, dust is liberated, and seeing that this work is done in a confined space, it is quite conceivable that injurious results to health may follow.

In some works ganister is ground dry in what are known as “sieve mills.” These are ordinary edge-runner mills, with a sieve at the bottom of the pan. The fine ganister passes through the sieve, and is taken by elevators to the sifting machine, where what is fine enough is carried away to the receptacle for holding it, the coarser material being carried by shoots to be again ground in the mill. In many works the ganister, although nominally dry, is damped sufficiently to prevent any escape of dust, and it has been stated by experienced manufacturers that the damping in no way damages the material, nor does it hinder the work. This dry ganister crushing is in most cases a subsidiary process, the quantities required being small, it only being used for the purpose of making a cement, or mortar, for joining silica bricks or other fire resistants.

Ganister workers are peculiarly liable to those ailments incidental to occupations exposing the operatives to extremes of heat and cold, to damp, and to draughts, but the writer believes that he has, in general terms, defined the peculiar and exceptional risks incurred in this occupation. Having done so, it seems difficult to account for the alarming mortality returns published in Dr Birmingham’s article. A possible solution may be found in the fact that where ganister works are situated there are also large numbers of fireclay works in which are made fire-resisting bricks, tuyeres, pipes, gas-retorts, etc. To the uninitiated it might appear that ganister and fire-brick workers were engaged in one and the same occupation, nor would this be unreasonable when the constitution of the two substances is considered. Ganister is stated to contain 95 per cent. of silica, whereas, according to _Chambers’s Encyclopedia_, from which the following extract is taken, it will be seen that fireclay contains from 54.2 to 65.1 per cent. of silica.

“Ordinary fireclay is chiefly found in beds not usually
much exceeding two feet in thickness, in the coal measures,
interstratified with seams of coal and other rocks. In the
British Islands it is most largely worked about Glasgow,
Newcastle-on-Tyne, and Stourbridge in Worcestershire, at which
last place it is said to have been discovered about 1555 by
some wandering glass-makers from Lorraine. But it occurs, more
or less, in most places where true coal is found. It is mined
in Germany, Belgium, France, the United States, and other
countries. Stourbridge fireclay, owing to its excellent quality,
is largely exported to foreign countries, as well as bricks and
other objects made of it. Refractory clays are found, although
more rarely, in other formations besides the coal measures.
For example, some of Tertiary age found in Dorsetshire and
Devonshire are made into firebricks. The following table shows
the principal constituents of fireclay:--

+----------------+--------+--------+--------+--------+--------+
| | No. 1. | No. 2. | No. 3. | No. 4. | No. 5. |
+----------------+--------+--------+--------+--------+--------+
| Silica | 65.10 | 51.10 | 59.49 | 53.52 | 54.20 |
| Alumina | 22.22 | 31.35 | 28.95 | 33.68 | 33.80 |
| Potash | 0.18 | ... | ... | Trace | Trace |
| Lime | 0.14 | 1.46 | Trace | 0.76 | Trace |
| Magnesia | 0.18 | 1.54 | ... | 0.14 | 0.02 |
| Oxide of iron | 1.92 | 4.63 | 1.05 | 0.52 | 0.01 |
| Water | 9.28} | 10.47 | {11.05 | 11.34 | 10.86 |
| Organic matter | 0.58} | | { ... | ... | 0.15 |
+----------------+--------+--------+--------+--------+--------+

No. 1, Stourbridge; No. 2, Newcastle-on-Tyne; No. 3, Gartsherrie, Scotland; No. 4, Poole, Dorsetshire; No. 5, Morgantown, West Virginia, United States.”

Ganister is pulverised in the wet state. Fireclay is not moistened, but ground into a fine dry powder, certainly suggesting greater risk to the workers.

Into other industries, such as the manufacture of steel-melters’ composition, the crushing of ganister largely enters. This composition is used for the manufacture of heavy castings, and contains large proportions of old ganister and fireclay crucibles, bricks, mortar, etc., which are ground in open edge-runner mills in the dry state, fed, and often sifted by hand. The work is generally done in the open air or in open sheds, where the dust is blown about, and where it is a practical impossibility for the worker to avoid inhalation of this irritant. The use of closed mills, closed cylindrical worm-screw conveyers, and mechanical sieves, would largely avoid unnecessary risk, and these labour-saving appliances (the writer believes) would soon more than repay any original cost.

The sickness and mortality amongst ganister workers engaged the attention of the poor-law authorities in the district of Deepcar, near Sheffield. Statistics were prepared for them, and a very carefully considered report dealing fully with the subject was submitted by Dr Robertshaw of Stockbridge, Medical Officer of Health for the division.

The attention of Dr Legge, H.M. Medical Inspector of Factories, was called to the subject recently, and he obtained from Dr Robertshaw the lung of a ganister miner, who had presumably died from pneumoconiosis. The following is an extract from the valuable report by Dr F. W. Andrews, Pathologist to St Bartholomew’s Hospital, of the anatomical changes in this lung induced by the inhalation of ganister dust, published in Dr Legge’s Report to the Chief Inspector of Factories for the year 1900.

_Report on Portions of Lung from a Ganister Miner._

The upper lobe is densely indurated, black and fibrotic. The pleura is thickened, especially at the apex. The lower lobe shows less advanced changes; numerous blackish nodules, about the size of a hemp-seed, are scattered throughout its substance with tolerable uniformity. Under a lens many of these indurated patches are seen to contain a minute cavity, as if they had been formed around minute bronchi or blood-vessels. The intervening lung tissue is greyish, scarcely at all pigmented, and not indurated; it has the appearance of slight uniform emphysema. The large and medium-sized bronchi stand out prominently. To the naked eye the lung nowhere shows any evidence of tubercle.

_Microscopic Examination._--Seven different blocks of lung tissue were selected illustrating as far as possible the different degrees of fibrotic change present, from an area almost normal up to the densest induration. These were sectioned. The method of staining found most suitable was that known as Van Giesson’s--viz., staining in hæmalum, followed by a counterstain of acid fuchsin with picric acid. In this way the distribution of the fibrous tissue was demonstrated with great minuteness. Nuclear staining was not very well marked, because the tissue had been lying so long in spirit.

All sections show an abundance of foreign mineral particles of a black or brownish colour. The majority of these are minute, irregular, sometimes angular in form. Seen singly they are semi-transparent and brownish, but they are commonly collected into blackish heaps, included in cells, and then appear opaque. Careful focussing, however, reveals the presence of the angular semi-transparent particles in these accumulations. The pigment masses have not the soft and rounded outline of the carbon masses seen in the lungs of town dwellers; nevertheless very finely divided jet black particles are present, which are probably carbon, but they are less abundant than the brownish semi-transparent masses. The pigment masses occur chiefly in connection with the fibrotic areas.

A few simple chemical tests were applied to microscopic sections, and their effect watched under the microscope. Caustic potash (10%) produced no change whatever in the pigment. Glacial acetic acid likewise caused no change. Fuming nitric acid caused liberation of gas bubbles under the coverglass, but the colour and amount of the pigment were in no way altered. From this it may be concluded that the colour does not depend upon altered blood or any organic product, but that the pigment is purely mineral in character--carbonaceous or siliceous. The liberation of gas by nitric acid indicates the presence of traces of carbonates.

The characters of the fibrotic change and its localisation and development could be traced from its earliest commencement. Sections of the least affected portions of the lung present the following appearances. The pleura is scarcely thickened over much of the lower lobe. There is a slight degree of diffuse emphysema; apart from the indurated patches there is a very slight increase in the amount of fibrous tissue present in the alveolar walls generally, but in some places this is barely perceptible. Careful search in the alveolar walls reveals the presence of scanty mineral particles scattered in the tissue. In places these form larger clumps. Some few detached epithelial cells, laden with pigment, are seen here and there in the alveoli; but on the whole, except around the fibroid nodules, the pulmonary epithelium shows no sign of proliferation or catarrh. There is no evidence of general broncho-pneumonia and none of vascular congestion.

The development of the fibroid nodules appears to take place in the first instance around the small arteries, veins, and bronchi. Where a vessel chances to be cut longitudinally, the perivascular thickening is seen to be irregular and patchy, whence arises the appearance of discrete fibroid nodules. When cut transversely, nearly all the blood-vessels display some degree of perivascular fibrosis. This is true also of the bronchi; but these have undergone so much loss of mucous membrane that it is not always easy to say which are bronchi and which blood-vessels. It is not possible to be sure that all the young fibroid nodules have this perivascular or peri-bronchial origin. Some appear to be independent of vessels or bronchi, but it is possible that they are tangential sections of such thickenings. It seems clear, however, that most own such an origin. In any case the relation between the accumulation of mineral particles and the production of new fibrous tissue is obvious and beyond dispute.

Older and denser nodules, such as are visible to the naked eye, as the hemp-seed structures above described, illustrate the further development of the process. In those the vessel or bronchus around which they have presumably arisen has usually disappeared, and they present concentric zones which represent different stages in their formation, and illustrate the manner in which they increase in size. The outermost zone shows the earliest stage: large black pigment-laden cells accumulate; they may be in part leucocytes, in part pulmonary epithelial cells or fixed connective tissue corpuscles. The pulmonary epithelium is here often in a condition of catarrhal proliferation--a localised broncho-pneumonia--each cell full of mineral particles. The next zone consists of a loose connective tissue, the meshes of which contain the large pigment-laden cells previously mentioned. The mineral matter is almost entirely intracellular. The central mass is composed of a dense fibrous tissue in which the cells have almost entirely disappeared, the mineral particles now becoming free and less conspicuous because they are no longer aggregated into dense black clumps. It is easy to realise from the structure of such nodules how they increase in size at the expense of the lung tissue. Beneath the pleura a similar development of new pigmented fibrous tissue similarly occurs. It is to be observed that all this fibrotic change corresponds in its localisation with the distribution of the lymphatic system of the lungs. The lymphatics, originating by stomata between the pulmonary epithelium, fall into two sets--(1) the sub-pleural network, and (2) those which closely accompany the blood-vessels and bronchi, forming a perivascular and peri-bronchial network.

The final stages in the process are shown by sections taken from the upper lobe of the lung, in which the fibrosis is much more dense and complete. Here the individual nodules have so encroached upon the lung tissue that they have more or less completely coalesced. In the most advanced portions, little or no normal lung tissue can be seen, although the focal character of the fibrosis is still perceptible, since islands of dense fibrous tissue are connected by areas in which the pigmental cells are enclosed in a looser connective tissue. The mineral particles are here even more abundant and conspicuous than in the lower lobe of the lung. In one single nodule (in the lower lobe) calcification was seen, but this stage is absent elsewhere.

Although to the naked eye there is no evidence of tubercle in the lung, yet microscopically such evidence exists in at least one of the seven blocks. The process of fibrosis has been traced from its earliest stages, and is most positively non-tubercular in its origin. The evidence of tuberculosis is present, as a recent and accessory phenomenon, only in the most advanced stages of the fibrotic change. It consists in the presence of small miliary tubercles embedded in the fibrous tissue, and showing the characteristic structure of tubercles, with typical giant cells. Even in these no tubercle bacilli can be demonstrated.

The conclusions to be drawn from the preceding observations are as follows:--

The inhaled mineral particles are, in the first place, deposited uniformly in the pulmonary parenchyma. They are at once taken up hence by the lymphatics and carried along by the lymph stream. The lymphatics have a perivascular, peri-bronchial, and sub-pleural distribution, and in these situations the mineral matter specially accumulates, because the amount is greater than can be got rid of by the lymphatics. It is here chiefly found enclosed in cells (phagocytes), and exercises an irritant action leading to the production of new fibrous tissue in these situations. The fibroid areas increase at the expense of the adjacent lung, in part at least by the development of a localised broncho-pneumonia, and in part by thickening and induration of the alveolar walls. When the fibrous tissue is fully formed the cells containing the mineral particles break up and degenerate, and the particles again lie free amongst the fibrous tissue. By the spread and coalescence of the fibroid areas, the lung tissue in the most advanced areas completely disappears. A secondary tubercular infection has now taken place, and miliary tubercles appear in scanty numbers in the fibroid areas.

_Chemical Analysis._--Portions of the lung were handed to Mr H. A. Schölberg, M.B., who furnishes the following analyses.

The material supplied was dried at 100°C. on a water bath for three hours. The dry lung tissue thus obtained was used for analysis.

(1) _Analysis for total Ash._
Grammes of dry lung taken 2.2675
Loss of weight on combustion in muffle furnace 1.1900
Residue of ash 1.0775
∴ Percentage of ash in dried lung = 47.519

(2) _Estimation of Silica._
Grammes of dried lung taken 0.1505
Silica in the same 0.0100
∴ Percentage of silica in dried lung = 6.644

HAMILTON P. SMITH.