Chapter XVII: Dust as a Cause of Occupation Disease

_General View of the Subject._

Were it not for dust, fume, or gas, there would be little or no disease due to occupation except such as might be caused by infection, the breathing of air poisoned by the emanations of fellow-workmen and exposure to cold after working in overheated rooms. Dust plays such a prominent part in the causation of occupation disease that I have thought it advisable to discuss the subject in a general way _apart from_ the various industries detailed by separate writers. The harmful effects of dusty trades have long been known. As far back as the end of the seventeenth century, Ramazini, who was the Professor of Medicine in Modena, and subsequently at Padua, had drawn attention to this subject. He showed in his treatise, the _Diseases of Artificers_, how ill-health was caused by the inhalation of subtle particles that were offensive to human nature, and its aggravation by the unnatural postures of the body assumed in certain occupations. He also pleaded for the introduction of such contrivances as would lead to the safety of the workmen and the necessity for their being medically inspected. In these senses, therefore, he was the pioneer of the State Medicine of our time.

Apart from anything inherently poisonous in the dust that is given off in a particular trade, dust itself, mechanically speaking, is prejudicial to health. A considerable length of our respiratory passages is lined with a layer of ciliated epithelial cells, _i.e._, cells from the free end of which project numerous hair-like processes that execute a rhythmic bending movement, like a field of wheat when a current of wind passes over it, and whose function it is, owing to the cilia actively bending in an outward direction, to prevent dust getting into the lungs, and to favour its expulsion should it have gained access to the smaller bronchial tubes. Nature, anticipating that dust would be drawn into the lungs in inspiration, has therefore provided this means for making its access as difficult as possible, and of effecting its removal when the breathing of the dust is intermittent. When animals are exposed for a period to a sooty atmosphere and are subsequently killed, their lungs are found to be perfectly black, but if other animals, after similar exposure, are allowed freedom in the open air, the lungs after death exhibit few dark patches. One of the effects of recurrent inflammation of the bronchial tubes is to bring about detachment and removal of this ciliated epithelium, and with its disappearance an important safeguard to the lungs is lost.

Dust affects the body by being deposited upon the skin, hair, eyelids, and the oro-nasal passages. Through the mouth and nose it is aspirated into the lungs during respiration, or it reaches the alimentary canal through the saliva or with the food.

When the skin becomes affected through an individual working at a dusty trade, the lesions thus caused are called _dermatoconioses_, similar affections of the lungs constitute _pneumoconioses_, while those of the gastro-intestinal tract are known as _enteroconioses_. Although the intestine, as in plumbism, is one of the most important and frequent channels by which industrial poisoning occurs, yet, pathologically speaking, the lesions of this canal are the least definite.

So far as _dermatoconioses_ or inflammatory affections of the skin are concerned, it is mostly in industries in which dry dust is given off that these are met with, as, for example, in dry bronzing, but certain fumes also cause them, as is seen in the smelting of antimony. No portion of the skin is free from the possible contamination by dust, but it is upon the hair, beard, eyelids, under the nails, upon the lips, and inside the nostrils, upon any uncovered part of the body when the individual is at work, or where the clothing loosely meets the skin, also in such flexures of the body as the armpits and the groins, and where the garters fix the stockings, that the effects of dust are mostly observed upon the skin. When the factory is warm, or the work heavy, and the individual perspires freely, the dust mingling with the products given off by the humid skin either falls off in muddy drops of sweat, or it cakes and forms crusts. As a consequence, there is a variety of lesions, _e.g._, simple irritation or itchiness, known as pruritus; inflammation or erythema proceeding to eczema; or, as in the case of antimony smelters, vesicles that become pustular, and in arsenic grinders, ulceration. Since dust that of itself is harmless can induce disorders by mechanically blocking the pores of the skin and the excretory ducts of glands, so, too, can harmful dusts act, but they produce in addition certain irritating and poisonous effects proper to the peculiar character of the dust. Some dusts are crystalline or sharp-pointed, and penetrate readily and deeply, while others have a distinct caustic action, and erode or eat away the tissues, as is the case with the bichromate compounds. Some forms of dust again are composed of soft particles that of themselves inflict little local damage, and only become harmful like flour in forming plugs; while attached to some forms of animal products, such as horsehair used in brushmaking, are micro-organisms that become a source of danger. It is unnecessary to mention the various skin affections or _dermatoconioses_ produced by dust. They are all more or less the result of inflammation. In many of the erythematous forms of skin eruption the redness of the skin may simply be the result of the mechanical action of the dust, or the dust may be absorbed. One consequence of local irritation may be the formation of vesicles. Sometimes the itchiness becomes so great that scratching is resorted to and there follows eczema. Where the vesicles become pustular, this is generally due to the action of metallic poisons of an acrid character, or to poisons of an animal nature, as in anthrax. Ulceration of the skin, on the other hand, is the result of such caustic action as that induced by arsenic and the chrome compounds. The accompanying Photographs show various forms of dermatitis that occur in flax spinners, also of diseases of the finger nails in hide dressers. They are introduced here not as illustrating the harmful effects of dust, for they occur in the wet processes of an industry, but as indicating what is meant by the term _dermatoconioses_.

FIG. 33.--Medium degree of Dermatitis in Flax
spinner (moist method); woman aged 33. Eighteen years’
service in Factory. (Dr Glibert).

SKIN DISEASES OF FLAX SPINNERS.

FIG. 34.--Severe form of Dermatitis in Flax spinner
(moist method); woman aged 19. Eight years’ service in Factory.
The small punched-out looking sore on thumb resembles what is
known to medical men as “Specific” ulceration, but it is in no
ways connected with it. (Dr Glibert).

FIG. 35.--Severe form of Dermatitis in Flax spinner
(moist method); woman aged 19. Eight years’ service in Factory.
Observe special round callosity on ulnar side of hand, an
affection first pointed out by Dr Van Eecloo of Lille. (Dr
Glibert).

SKIN DISEASES OF FLAX SPINNERS.]

_Skin Diseases of Flax Workers._

It is through the kindness of Dr Glibert, Medical Inspector, Labour Office, Belgium, that I am able to show in the accompanying Photographs these particular lesions of the skin. The four Photographs in which the palmar surface of the hand is shown, are taken from flax workers. They indicate varying degrees of erosion, due to the frequent contact of the hands of the female worker with the irritating materials contained in the liquid used for spinning. At the commencement of the malady, as is well shown in the Photographs, the lesion is limited to an exfoliation of the epidermis, and this is not accompanied either by pain, pruritus, or functional trouble of any kind. Later on the dermis itself, or true skin, becomes involved at certain places, usually very few, and at these spots there exists considerable irritation, also a sensation of painful pricking, especially pronounced after working, and when the wounds are brought into contact with the air. As a rule, the malady does not proceed beyond this stage, but in some rather rare cases, met with mostly during severe weather, the ulceration tends to pass into the deeper tissues of the skin, and to assume an appearance which, to an unskilled observer, recalls the lesions met with in syphilis. There is nothing, however, in the flax workers’ dermatitis to confirm this suspicion. It is necessary to remark that there is never produced erythema, the formation of vesicles or a vesico-pustular eruption, and still less the glossy and bright appearance of the skin of the hand observed in eczema of a lichenoid character. Dr Glibert has frequently met with this form of eczema, to which Dr Leloir and his pupil Lefèbvre have drawn attention, but the ulcerative type of dermatitis indicated in the accompanying Photographs is absolutely distinct from these, and must not be confounded with them. It is only right to mention that although dermatitis has been observed in Belgian flax spinners, Belfast operatives similarly employed do not, according to Dr Purdon, suffer.

_Diseases of Nails in Furriers._

The two Photographs showing the back of the hands of workmen who scrape rabbit and hares’ skins used in the manufacture of artificial furs exhibit an affection of the nails, to which Dr Glibert of the Belgian Labour Office drew attention in the Annual Report of the Inspection of Labour, 1896. The work of separating the layer of aponeurosis, which occurs on the under surface of the hide, causes in the dresser a special disease of the nails of the fingers. The groove under the nail becomes deeper, the nail is subsequently detached from the finger and falls off, either by some peculiar pathological process unaccompanied by ulceration, or by one of an inflammatory nature akin to what occurs in whitlow. The malady may attack all the fingers of the two hands, but it seizes by preference the thumb, the middle and ring fingers of the right hand. It is a common affection in fur-pullers in Belgium. Dr Glibert is the only writer I know who has described it. Of 22 workmen whom he examined, it was present in 18. He regards the lesion as distinctly microbic.

FIG. 37.--Severe type of disease of Finger Nails
in a Hide dresser. Man, aged 49. Twenty years’ service. (Dr
Glibert).

DISEASE OF FINGER NAILS IN FURRIERS.]

_Lung Diseases due to Dust._

In pneumoconiosis the lung is altered in structure as the result of irritation caused by inhaled dust. A healthy lung is composed of loose spongy tissue, through which run in all directions the bronchial tubes and their fine ramifications (see Fig. 38). The essential part of the lung is made up of alveoli or air-cells, like the meshes of a net. Just as an ordinary net is made of strands of cord, so are the walls of the pulmonary alveoli formed of delicate lines of connective and elastic tissue, in which run capillary blood-vessels. The partitions thus formed are coated on both sides by a layer of flattened epithelial cells. It is this loose and almost uncovered condition of the pulmonary capillaries that allows of the rapid interchange of gases between the blood circulating in the alveolar walls and the air in the lung during respiration. Nature has placed certain obstacles in the way of particles of dust gaining easy access to the lungs, to wit, the narrow openings of the nostrils, the mucus secreted by the lining membrane of the nose, and of the trachea and bronchi; the narrow chink between the larynx and trachea known as the vocal chords, the ciliated epithelium already described, and a mechanical difficulty generally; so that while even with forced inspiration it is not easy for dust to be carried into the lungs, yet the fact remains that where an individual is working in the dusty atmosphere of a factory for several hours a day, week after week, particles of dust ultimately find their way into the finer bronchi, and subsequently into the pulmonary tissue itself. It is the repeated working in a dusty atmosphere that causes the trouble. A good deal depends, too, upon the character of the dust. Certain fine dusts, such, for example, as flour, may for a time be arrested in the mucus secreted by the respiratory passages, and be expectorated; while others, such as white lead, become dissolved in the alkaline mucus, are absorbed into the system, and thus induce constitutional poisoning. Fine fluffy material, like that given off from cotton and flax, can reach the lung, while sharp-pointed particles of metallic dust wound the epithelial lining of the smaller bronchi and penetrate into their walls, or they destroy the protecting layer of epithelium, and reach the alveoli either directly or indirectly through the lymphatics. These particles set up irritation in the lung, followed by a very marked increase of its fibro-connective tissue, which encroaches upon the spongy structure of the lung and destroys its aerating function. In the coal-miner’s lung, for example, there can be observed small masses of cells deeply laden with carbon particles surrounded by a hardened zone of altered lung, numerous black streaks underneath the pleura or covering of the lungs, ink-like dots in the walls of the small bronchi, and enlargement with pigmentation of the bronchial glands. The special pathological changes in the lungs in the various pneumoconioses are peribronchitis, and a great increase of the fibro-connective tissue, whereby the lung becomes converted into a hard and almost solid organ, incapable of carrying on the work of respiration. Hence are explained the difficulty and shortness of breath in people thus affected with what is called fibrosis of the lung. On examining microscopically a portion of lung that has undergone this change, there can be seen imbedded in the thickened fibrous tissue, particles of grit which exactly correspond in shape and size with those found on examining the dust removed from the mine in which the person works, or from the factory, in the case of steel-grinders’ lung. The identity of the particles of grit in the lung and those in the dust of the factory can be additionally confirmed by chemical examination. Such, in a few words, is the effect upon the lung caused by inhalation of the dust generated in a dusty occupation. The newly formed fibro-connective tissue is of low vitality, and is badly supplied with blood-vessels, and yet it goes on increasing and encroaching more and more upon the lung tissue, which it replaces. Although it seldom tends to break down, the consolidated tissue notwithstanding shrinks, the chest becomes smaller, cough more harassing, and emaciation progressive. The affected workman is regarded as the victim of consumption, but the disease is not necessarily _tuberculous_. Under these circumstances, where a lung has become altered in structure and its vital resistance diminished, it becomes an easy matter for true tuberculosis, as the result of its specific bacillus, to be grafted on to a pneumoconiosis, or dust lung disease. In people who have worked in a thick atmosphere there is therefore found a form of consumption due to the inhalation of dust, and another the result of the tubercle bacillus, but in old-standing cases the two are generally found combined. The tendency of modern pathology is to look upon all pulmonary phthisis or consumption as tuberculous, but the fact remains that phthisis can be caused by dust. Pneumoconiosis differs from the tuberculous type of lung disease in being more amenable to treatment in the early stage, also in the fact that while both lungs are affected, it is the bases rather than the apices that suffer. If the workman, for example, leaves his dusty employment, especially in the early stages of his illness, the malady may be arrested. Usually the march of the disease in this form is slower than the tubercular. It is an old idea, yet one that many seek to palm off as modern, that pulmonary consumption is an infective disease. In factories where many persons are at work, there are almost sure to be some who are tuberculous, and who cough and expectorate upon the floor. The expectoration dries, is trodden under foot, and, mingling with the dust, it rises into the atmosphere and is inhaled. Infection from consumptive fellow-workers must therefore play a part in the propagation of industrial phthisis, but the bulk of such cases do not assume the character of the occupation form of fibrotic phthisis to which we have just alluded, and which is known to occur frequently in men employed in dusty trades conducted in the open air, _e.g._, in masons and French millstone builders, in whom infection is less likely to prevail, and where the breathing of close and impure air can play no part.

There are four recognised types of pneumoconioses or industrial lung disease: (1) _Chalicosis_ or _silicosis_, due to stone dust and siliceous material, as in masons’ phthisis; (2) _siderosis_, due to metallic dust; (3) _anthracosis_ or coal-miners’ phthisis; and (4) _byssinosis_, caused by inhalation of cotton particles.

_Gastro-intestinal Lesions._

The _enteroconioses_ or gastro-intestinal lesions induced by dust are less well-defined pathological entities than the affections of the skin and lungs, and yet they play an important part in poisoning by such metallic dusts as lead, arsenic, and mercury. Apart from such symptoms as vomiting, diarrhœa, and colic; which these cause, there are the well-marked physical signs of poisoning present in the gums, as, for example, the “blue line” in plumbism, and the loose teeth and ulcerated gums in mercurial poisoning.

* * * * *

The attention of the reader is directed to the accompanying series of Microphotographs as illustrations of some of the forms of dust seen through the microscope, to which workpeople in various trades are exposed. Apart from the poisonous character of any particular kind of dust, _e.g._, that of lead and arsenic, the presence of chemical irritants inherent in the dust itself as in bichromate compounds, and the clinging of micro-organisms to such animal products as horsehair and wool, there is an opinion entertained by pathologists that the actual form of the particle of dust and its hardness are responsible for much of the damage inflicted upon the lungs of workmen engaged in dusty trades. Mineral and metallic particles of dust are hard and often sharp-pointed. Theoretically, therefore, it is expected of them that when they reach the lining membrane of the respiratory passages they will inflict greater damage than particles of dust that are softer and rounder. How far pathological experience supports this expectation I am not prepared to say. The dust that is given off in various occupations may be mineral, metallic, vegetable, or animal. I have reproduced some Microphotographs taken from Dr Migerka’s monograph, _Staubarten in Wort und Bild_, Vienna, 1895, and have added a few taken by Dr R. A. Bolam and myself, of dust from various industries, supplied by H.M. Inspectors of Factories. Some of these Microphotographs may be briefly described:--

Fig. 42, _cement_ dust. Under the microscope are seen a few sharp-edged little plates and amorphous masses like small clumps. The particles are not of themselves so dangerous as might at first sight appear. Although cement workers suffer from pulmonary disease, they do not do so to the great extent that might be expected. Probably the harmful effects are largely due to the hygroscopic character of the particles and their alkaline reaction. Hirt gives the following percentage statistics of diseases for comparison:--

-----------------+-----------+-----------+------------+-----------+
| Phthisis. | Bronchial | Emphysema. | Pneumonia.|
| | Catarrh. | | |
-----------------+-----------+-----------+------------+-----------+
Porcelain Makers | 16 | 15 | 4 | 5 |
Masons | 12.9 | 10.4 | 6.5 | 4.4 |
Cement Makers | 8 to 10 | 15 to 17 | ... | 4 |
-----------------+-----------+-----------+------------+-----------+

Comparing Figs. 43 and 44, _sandstone_ and _granite_, it will be observed that the granite dust is lightish-grey in colour, with black specks, and contains numerous flat, transparent splinters of quartz. Sandstone dust, on the other hand, is a finer powder, it is yellowish, and equal in colour throughout; it is rather an amorphous powder; in some samples a few sharp-edged plates of quartz can be seen. From microscopical appearances it might be assumed that granite dust would be very much more hurtful to the workmen than sandstone, and yet, according to Arlidge, _Diseases of Occupations_, p. 303, who made special inquiries into this subject, the workmen employed around Aberdeen in the cutting, dressing, and polishing of granite, are seldom the victims of pulmonary disease attributable to their occupation. This circumstance may be due to the igneous character of the rock, and the small quantity of dust that is thrown off, especially in the act of chiselling. Besides, as the particles of dust are of considerable size, they would, if inhaled, be caught in the upper part of the respiratory passages, and therefore not have the opportunity of inflicting damage upon the lung. The fact remains that while Aberdeen granite workers suffer from chronic bronchitis, they are remarkably free from the pulmonary fibrosis to which stone masons and French millstone builders are liable.

FIG. 42.--Cement.

FIG. 43.--Sandstone.

FIG. 44.--Granite.

FIG. 45.--Lead Dust from Printing Shop, and
Type casting.

Microphotographs of Dusts developed in Dusty Trades. The
first twenty are reproductions after Migerka: the last six
after Bolam and Oliver.]

In Fig. 45, _lead_ dust, as obtained from a printer’s shop, the particles are seen to vary in size and form. The particles are for the most part round, and not unusually sharp. This dust is not harmful on account of its form so much as dangerous through being absorbed into the blood. The dust that is given off in _file-making_ contains particles of iron as well as lead and charcoal (see p. 342), and this is productive of a large amount of pulmonary disease in men and women engaged in this trade. But with file-cutters as with printers and typographers generally, the unhealthy and close workrooms in which they follow their avocation are to some extent also responsible for the lung diseases. As bearing upon this subject, the annual reports of Benefit Societies are not without interest. The reports of the Benefit Societies of the printers and type-casters of Vienna, from 1889–1892, give the following percentage of illnesses:--

--------------------------------+----------+-----------+----------+
| Typists. | Printers. | Casters. |
| | | |
--------------------------------+----------+-----------+----------+
Tuberculosis | 2.8 | 1.7 | 1.6 |
Diseases of Respiratory Organs | 11.4 | 7.5 | 10.8 |
Disorders, etc., of Digestive „ | 7.5 | 5.1 | 7.1 |
--------------------------------+----------+-----------+----------+