LIBRARY OF BOOTT TURNER REVIEW OF LITERATURE ON EFFECTS OF BREATHING DUSTS, WITH SPECIAL REFERENCE TO SILICOSIS1 BY D. HARRINGTON 2 and SARA J. DAVENPORT INTRODUCTION Dust diseases are much before the public at present, but little reliable information on the subject is readily available to the layman; even those rated as experts usually have a more or less_theoretical conception of these diseases, their causes, remedies, and prevention. Until recently little attention has been given to prevention, and the usual attitude of the engineer, upon whom the main reliance for prevention ultimately must devolve, has been to let "sleeping dogs lie" or, more definitely, to "let well enough alone." However, the "laissez faire" attitude no longer is tenable; in the past few years numerous conditions have caused those engaged in industry, including mining, to study the subject with a view to ascertaining the facts upon which to formulate remedial measures, primarily preventive. This bulletin is an attempt to assemble information in convenient form on effects of breathing dusts, largely in the mining and allied. industries. The literature on this subject is so extensive that no attempt has been made to include all published material or all types of dust diseases but only to assemble some of the more outstanding data on several aspects of the subject, especially with reference to silicosis. DEFINITION AND CLASSIFICATION OF DUSTS According to Webster's Unabridged Dictionary dust may be defined as fine, dry particles of earth or other matter so comminuted that they may be raised and wafted by the wind; that which is crumbled to minute portions; fine powder. In 1876 Richardson (1) * included in the term "dusts" all those fine, solid particles thrown off from various substances in the processes of manufacture or treatment of articles in common use in daily life. Drinker (2) in 1930 defined dusts as solid particles ranging in size from less than 1 micron to about 150 microns; this definition is probably as applicable as can be had insofar as concerns respiration. 1 Work on manuscript completed November 12, 1936. Numbers in parentheses refer to bibliography at end of bulletin. 5 1 Physiologically, there are almost as many different classifications of dust as there are authors on the subject. Richardson (1) suggested the following: (a) Cutting dusts, formed of minute, hard, crystallized particles with sharp, cutting, and pointed edges and composed of iron or steel, stone, sand or glass, dried silicates in earthenware, lime, and pearl; (b) irritant dusts, derived from woods, ivory, textile fabrics, fluffs of wool, silk, cotton, flax, hemp, hair, and clay; (c) inorganic poisonous dusts charged with arsenical salts, derived from poisonous chemical compounds used for coloring artistic products or for preserving organic substances, such as furs; (d) soluble saline dusts, organic poisonous dusts thrown off during the making of tobacco into cigars and snuff and carrying with them particles of the dried tobacco plant; (e) obstructive and irritating dusts composed of carbon, fine particles of coal dust, scrapings of carbon or soot, dust of rouge, and flour. Baskerville (3) in 1912 classified dusts as: (a) Insoluble inorganic dusts, including metals (antimony, arsenic, type metal, brass, bronze, copper, aluminum, iron, steel, lead, manganese, vanadium and ferrovanadium, silver, tin, zinc, and solder) in a state of fine division (dusts, atomized metals, and metallic powders); flue dusts; various ore dusts (iron ore); silica; sand, emery, flint, and glass powders; carbon graphite, diamond, coal, and soot; brick dust, marble, granite, cement, and terra cotta; lime, gypsum, plaster, and meerschaum; phosphates; and guano. (b) Soluble inorganic dusts, including substances likely to be swallowed and absorbed, such as metal particles, including lead, brass, copper, zinc, arsenic, mercury, and silver, as well as soluble inorganic salts. (c) Organic dusts, comprising such widely varying materials as sawdust, fur, skins, feathers, broomstraw, grains, flours, jute, flax, hemp, cotton, wool, carpet dust, street sweepings, tobacco-box dust, hides and leather, felts, rags, paper, and horsehair. In 1918 Hoffman (4) considered the following classification to be in strict accord with the facts as they were known and understood at that time: (a) Inorganic dusts, including metallic dust, mineral dust, and dusts of the mineral industries; (b) organic and miscellaneous dusts, including vegetable-fiber dust, animal and mixed-fiber dust, organic dust, and mixed organic and inorganic (public) dusts. Thompson (5) classified dusts as (a) insoluble inorganic dusts (irritating the respiratory passages), as flint, silica, sand, carbon (coal, soot), brick dust, marble, granite, terra cotta, cement, asphalt, enamel, glass, quartz, lime (gypsum, plaster), meerschaum, phosphate (fertilizers), guano, emery, diamond dust, metal filings (lead, brass, iron, steel, etc.), pumice, and ashes; (b) soluble inorganic dusts (liable to be swallowed and absorbed), as soluble arsenic, mercury. lead and silver compounds, metal filings of lead, brass, and zinc: (c) organic dusts and fibers arising from handling or manufacture of wood, bone, and shell, fur, skins, hides and leather, feathers, brooms and straw, flour and grain, jute, flax (linen), hemp, cotton, wool (worsted, etc.), tobacco, felt, carpets, rags and paper, horsehair, and street sweepings. De Balsac and Agasse-Lafont (6) suggested the following classification: (a) Active dusts, which are immediately disseminated and radiate beyond their point of application; toxic dusts (lead, arsenic, and mercury); caustic dusts, chromates, etc.; infectious dusts. (b) Inert dusts, soft, flexible felting dusts (wool, cotton, and leathers); hard, troublesome, wounding dusts (ligneous, metallic, stone, and coal dusts). Schürmann (7) differentiated dust, according to origin, into animal, plant, and mineral dusts and dust from the artifacts. Animal dust is evolved with the working of ivory, horn, whalebone, bones, mother-of-pearl, hides, leather, bristles, sheep's wool, hair (horse, rabbit, and cow), and feathers; plant dust has its origin in industries working with grain, medical powders, spices, cotton, hemp, jute, flax, tobacco, wood, thick-shelled nuts, bark of plants (tanning industry), rags, shoddy, and paper; mineral dust is formed in working hard coal, marble, and other limestones and in connection with clay and porcelain industries, also pumice, sandstone, granite, and slates; dust from artifacts is encountered in the glass, glazing, enameling, tile, cement, Thomas slag, celluloid, iron, steel, bronze, galalith, and lead-alloy industries and in the chemical (especially dye) industry. He defined mixed dust as a mixture of polishing materials and the fragments of the object being polished. Drinker (2) says that all these classifications have little practical importance, since in daily practice in industry the harmful effect is exercised more frequently by dusts mostly of mixed origin. Most important, moreover, is the physical and chemical constitution of the dusts and consequently their action on the system. An effort has been made to group under the heading "Inert" a certain number of dusts; but the number is becoming more and more reduced since certain dusts, such as talc and asbestos, until recently considered as inert nevertheless have caused serious organic lesions among certain classes of workers. The majority of experts admit that the so-called inert dusts are not really inert when considered from the pathogenic point of view. Although at the outset these dusts are not harmful and even when present in the workroom in large quantities some of them cause only transitory discomfort (sneezing, watering of the eyes, and cough), it is certain that as the organic reactions diminish and the system seems to have recovered from the effects they nevertheless finally attack it in a subtle manner, sometimes even seriously. The mucous membrane of the nose, the conjunctiva, first the upper and later the lower respiratory passages, the teeth, the skin, and often the digestive tract are subjected to the harmful action of these dusts. EXPOSURE TO DUST Prehistoric man, who originated the trade of making stone implements probably started the first industrial hazard, the extent and severity of which the medical profession, as well as the industries concerned, has begun to realize only recently. In fact, dust as a factor in the causation of disease had not received much attention before 1900. At the site of one of the Swiss lake dwellings where flint implements were found, although the flint must have come from a distance (probably from the South of France), the chippings of material were in such profusion as to imply that the implements were manufactured on the spot. In other words, a prehistoric flintknapping factory was probably located there (8). Some of the |