Document ndk22pwk0Yq5Vm0d3wzZk4kR

FILE NAME: National Safety Council (NSC) DATE: 1932 Feb DOC#: NSC212 DOCUMENT DESCRIPTION: NSC - National Safety News - Are All Dusts Hazardous? All Dusts Hazardous? By C. O. SAPPINGTON, M. D.( Dr. P. H* DUST has always been consid ered an important industrial hazard, but within recent Dusts classed as "harmful" are years European experts have believedthose which are known to it to be an outstanding industrial cause fibrosis of the lungs or problem. Although we have not made as much progress in these matters in systemic poisoning* Nonthis country, most authorities agree poisonous organic dusts are called asbestosis caused by the breath ing of finely divided abestos dust which is chemically caleium-magne sium metasilicate. Also within very recent years, due to research of Dr. Leroy Gardner of Saranac Lake, it has been shown that carborundum or silicon carbide is also capable of that our problems are really becoming apparent. This brief survey of the various not considered causes of struc tural damage producing a fibrous reaction when breathed in finely divided particles): finally, under the heading of inor phases of dust as an industrial prob lem will be confined to five different headings: (1) kinds of dusts; (2) what happens to dust when it is breathed; (3) silicosis; (4) methods of protection; and (5) legislation. Kinds of Dusts It is important for us to remember that there are harmless as well as harmful dusts. An explanation of the word " harmful" is in order; when we say that a dust is harmful, we mean that it produces a fibrosis in the lungs. By fibrosis of the lungs, we mean that an irritation is set up by the quality o f the dust breathed in, this irritation producing fibrous tis sue, or scars, which take the place of the normal lung structure. Of course there are chemical dusts of various kinds, which if breathed into the lungs will produce systemic poisoning. There is no more rapid way to contract lead, mercury or arsenic poisoning, than by breathing in finely divided particles of these metals, because the poisonous mate rial is immediately taken into the cir culation through the very thin and microscopic partitions in the air sacs of the lungs. In addition to poisonous chemical dusts there are the so-called non-poisonous organic or vegetable dhsts, such as cotton, jute, hemp, also sugar and flour, and others which could be included under this category. Such dusts as these may cause functional known that these dusts can be irri tant to the skin and produce charac teristic irritant eruptions in certain instances. Of the inorganic or mineral dusts we have three types, the non-silicacontaining dusts, such as coal and lime; (of course there is a certain amount of silica in anthracite coal, biit in most bituminous coals there is relatively a very small amount of free silica) ; the combined silicates, as the name signifies, are those com pounds in which silica is in combina tion with other substances, typical examples of these being clay, talc, feldspar, and mica (up to about five years ago, most authorities agreed that no combined silicates produced fibrosis in the lungs ; within recent years, however, there have been re ports in the literature of cases of so-. ganic or mineral dusts is the classi fication known as harmful or free1 silica, the best known types of this class being silicon dioxide or sand, granite, quartz, and the different va rieties of sandstone. We can, therefore, make the follow ing outline of the various kinds of dusts: I. Poisonous (chemically) Lead, mercury, arsenic, and others. II. Non-poisonous A. Organic--cotton, jute, hemp, sugar, flour, and others. 15. Inorganic--(mineral) 1. Non-silica dusts, such as coal and lime. 2. Combined silicates. The orthosilicates such as clay, the metasilicates such as talc, and the trisilicates such as feldspar. 3. Harmful silica, existing in the forms of pure silicon dioxide or sand, granite, quartz, and the various kinds of sandstone. There is still some difference of opinion as to whether the various combined silicates and harmful silica itself can be considered non-poison ous. When this outline was made some years ago, it was thought that silica exerted its harmful influence purely by mechanical irritation. With recent years there has been some scientific evidence pointing to the fact that silica may exert its harmful in fluence because of its chemical attrib utes. disturbances in the lungs, but as far as we know, do not produce structural or organic changes. I t is also well Director, Division of Industrial Health. National Safety Council. (An address before the Engineering Division of the Chicago Safety Council.) W hat Happens to Inspired Dust Schematic diagram o f `lung cell bow ing engulfing cells migrating to blood and lymph vessels. "A ", blood ves sels; "B", lymph vessels. "D D D ," dust particles free in air space. Here we are concerned only with particles which have a diameter of less than ten micromillimeters. Sincela micromillimeter is equivalent lb L/3A NATIONAL SAFETY NE 19 1/25000 of an inch, it will be seen that the particles which can cause trouble in the lungs are microscopic in size and cannot be counted except by microscopic methods. It is now well for us to consider somewhat in detail the microscopic structure of the lungs showing just what, happens to respired dust par ticles. The sketch above shows a typieal air sac which has been magnified ap proximately 1000 diameters. We are looking at a cross-section of the air sac showing the air space, and the walls of the air sac, within which are the lymph vessels and the blood ves sels, " L .V ." and " B.V." in the dia gram. Note that there are some round cells which have gathered up particles of dust within them and also that there are free particles of dust in the air space. These, round cells are called phagocytes, meaning that they are de vouring cells. They actually sur round foreign material and engulf various kinds of foreign particles which may enter the air sac. These cells then migrate through the wall of the air sac and through the wall of the blood vessels and the lymph ves sels and are carried by the blood and lymph streams to various portions of the body. Causes of Fibrous Reaction We are particularly interested in what happens to the cells which en ter the lymph stream, especially in the case of the lungs, because at various points along the course of these lymph vessels, there arc interposed sets of lymph glands, which strain out the phagocytes and the foreign material. In doing this, they become enlarged, and in a great many instances these cells disintegrate leaving free silica in the glands, whicli then undergo fibro sis. This is what makes them visible in X-ray pictures, because of the in creased density resulting from the formation of fibrous tissue. A number of theories have been held as to the actual cause of the fi brous reaction in the lungs. An Italian named Mavrogordato first held that it was the quality of inspired dust and not its quantity which was the chief cause of a fibrous reaction.. A little later an Englishmen named Collis proved by microscopic anatom ical studies, that the devouring cells actually plugged up the lymphatic vessels and the glands at the roots of the lungs. So great is the stoppage FEBRUARY, 1932 of these vessels that they back clear up into the lung tissue proper, and there disintegrate leaving the free silica which because of its peculiar characteristics, is not absorbed like other dusts are. Being a constant source of irritation, a serum is poured out, which finally changes to fibrous tissue. This is a characteristic reaction which takes place in any part of the body where a foreign material is not absorbable and produces an outpour ing of serum which is eventually changed to fibrous strands. More recently, an Irishman by the name of Hefferman advanced the idea that the chief reason why silica pro duced a fibrous reaction was because it was a colloid in structure; you will remember from your chemistry that a colloid is a material which will not pass easily through an animal mem brane or cell wall and is distinguished from the crystalloids which nre solu ble in body fluids and thus pass easily through membranes or cell walls and may thus be finally excreted by the fluids of the body. Pneumonoconiosis is the scientific name applied to all types of dusted lungs, and it literally means a " dust ed '' lung. There are specific kinds of pneumonoconiosis, silicosis being a particular kind caused only by the breathing of free silica to the amount that fibrosis is produced. Abestosis is another form of pneumonoconiosis; anthracosis is a very common type, it being due to the inhalation of coal or carbon particles--most city dwellers have this type of pneumonoconiosis, which is not considered strictly speak ing a real pathological change. Silicosis It is well to repeat that silicosis is caused by the breathing of harmful amounts of free silica, which eventu ally produces a fibrous change in the lungs, replacing the normal lung structures. There are four important points in the production of silicosis: 1. Particle size. 2. Number of particles per cubic foot of air. 1 3. Mineral composition of the dust. 4. Length of exposure. We have already commented on the particle size, stating that it is only particles of less than ten micromilimeters in diameter that can 'cause trouble, because only these can get in to the lungs. The number of particles per cubic foot and the mineral composition of inspired dust can be considered to gether. These two factors have a dis tinct relationship to each other and this relationship is indirect, meaning that a safe concentration of dust will reach a higher number of particles per cubic foot when the silica content of the dust is low; contrariwise when the silica content of the dust is high, a safe concentration of particles will be correspondingly lower. Let us il lustrate this general statement: if the silica content of any given dust is 35 per cent, the standard of safety can be placed at approximately fifteen million particles per cubic foot of air in the breathing zone of the workman; if we reverse this situation and con sider a dust which has a silica content of 70 per cent, then the margin of safety will be approximately seven and one-lmlf million particles per cubic foot of air. When you reach 90 to 100 per cent of free silica, as in sandblasting, the standard is placed at approximately six million particles per cubic foot of air. Length of Exposure Our ideas concerning the length of exposure in the development of sili cosis, have undergone a change with in recent years. It was formerly thought that ten years was about the average exposure in the cases of sili cosis which had developed. It is now known that a great number of cases of silicosis have developed in much less than ten years of exposure. For instance, in some of the Canadian sili cosis laws, before a man can get com pensation, it is required that he show a minimum of three years' exposure in stone-cutting occupations, and a minimum of five years' exposure in other occupations. This would tend to show that the average time neces sary to the development of cases of silicosis is very much less than ten years. There are cases on record of where employees have developed sili cosis within a period of two years, within a period of one and a half years, and in certain rare circum stances, even under an exposure of one year. It must be remarked that not all persons are alike in the rapidity with which they develop silicosis under similar conditions of exposure. How ever, there is no immunity, natural or acquired, by which any individual may feel that he is entirely safe from 20 the contracting' <j to conditions Which dace this disease; rr . y/- Neither is there art^kttdbdr'^ by which a person ma2f .be fried silicosis after he b&s developed iti of the important points about Sfi} is its progressivenessj after; g; ___ ,, __ employee hs-'bep, ,, . mIoU vV eC dU fUrUoJm1 further .L U 141C 1. 'eC xA pp UoBsuU rl te? .. ^- '^inS V *,/ v The O ntario -fee thben as is called a " progressive'"/ype of htt /% . - eohideriig inethods of prbtec- pathology./ ' r .h--ob i-t,%-r,wise to m-enti,on that.th N_a- /. j X i tibnhl palely Council in conjunction ani example. Tco carr tle ^arious prro--ce-d-u--r-e-sSnielicceosssiasryC,o. m- :4 mission composed Of/thrCe expert phy- / Stages o f Silicosis 1 . 4 with Uv S. Public Health Service sjciaUs has be^UAppbhitedj it is th e^ , Completed a fibld study ie- duty of this commission tp make em- ' Three stages ar recognized th the health hards of; sand- jftoyment examirihtiohs bn all persons _ so-called ante-primary, the primary. blasting processes in industry. Briefly, ; entering'in d u strie'where there is a and. the secondary, These names were surveys "hav been 'm ade of various silicosis hazard, to make periodic ex-, given to the various stages through\ types of sandblasting equipment, pro- aminations /on- all persobs so em the ' British experience in Sbuth ; fectife apparatus, and other relative, ployed, and to fhte pebshswbo have Africa, which hafe finally come to be factors- Dust counts have beeh made, contracted silicosis^ . a model for all other countries. showing/thp eXhct number of particles The Ontario law provides that there In the ante-primary stage there," >e ubic foot of uir under' various inust be from three fo five, years' ex may be no other symptoms than those conditions. ^ Petrographic analyses posure, three years ~in stone-cutting of a common cold. The physical signs have beA TMade showing the exact trades and five years in other indus may be quite indefinite and not char- percentage of free silica under certain tries. In the, ante-primary , stage, acteristic. Usually, however, there .is- conditions, nq medical histories, to can be suggested for the safe conduct t i r / l l l t l' In the primary stage there is mOre o lsarib S ttag p m , Mob w ffl., " V f" TM k S F J 1" diminution of chest expansion, more form a .definite step Wtowa^rd the pro P" red- In the pwAttfy stage w here, shortness of breath on exertion, and tection oi workmen in these occupa physical signs are mOre constant and the chest findings are indicative o f. tions. 1/ ^ > radiographic changes are also more definite lung disease; The X-ray pic* characteristic, there is an impairment So iar, the best inethod of protec ture quite frequently shows an en tion as far as respiratory apparatus of which is usually not serious and per largement of the glands at the root each exposed employee is concerned, manent; for this stage a lump sum of the lungs, with an increased ( amount of fibrosis, an extension ,of the is the positive pressure hose mask, together with this, it is often neces of $1000 is awarded. In the second ary and final stage of silicosis where lineal markings out beyond what is sary to use properly equipped and the findings fire rarely unmistakable, called the " periphery," and a beaded maintained systems, of exhaust ven the impairment is considered serious appearance of these bronchial mark* tilation.-. - " ' ings caused by the laying down of and permanent.and the employee is awarded two-thirds of his wages for fibrous tissue, and collections of de In addition to these methods, spe- the rest of his life. vouring cells. :. X.) \ cial housing in the form of cabinets y Although the laws in Saskatchewan In the secondary sta^e, which is the ahd barrels and' Sandblast rooms halve also been fouhd valuable. I t is very and Quebec are not exactly the same, final stage of silicosis/there is consid important, however, that such enclos they are very similar and in these erable disability due/ to the increased ures should not only' completely house other instances a ra administered in a diminution of ln n i expansion and all apparatus, but 'should be built in similar way. - ! shortness of breath bn exertion; There/ such a tyay that the dust concentra- There are six States in the United may be cough and some sputum. The ,tion will be kept down to a point -States, which have complete occupa X-ray findings are quite definite now ,/ which' is compatible with healthful tional disease coverage, California, and are characteristic, showing aii in- 7 working conditions, Connecticut, Maryland, Massachu filtration over the entire f ^ l e p o r - ; . u tbe expericnce 0f most compa setts, North Dakota, and Wisconsin. nion of both sides of the lungs With ^ i?ipoS8ible to adequately Hawaii is also .included. what is known as a coarse mottled or proteet,snchr workmen without peri- It is interesting that Illinois enu snowstorm appearance. j ^odicrm edical supervision. This takes merates the dangerous' processes for We have to keep ill min'd alWayS ' the form of periodic examinations, to- which compensation will be paid, if that any case of silicosis may be com* gether with X-ray pictures, on em , the claim is justified ; these include plicated by tuberculosis, in fact in a ployees who are already Working, and processes involving lead, arsenic, certain number of instances, the t o a very /painstaking employment, brass, and zinc. NATIONAL SAFBtY NEWS >