Document B5VNZ6vO5zoG8waa543kD5Mrj

FILE NAME: Asbestos Cement Pipe and Sheet (ACPS) DATE: 1971 DOC#: ACPS012 DOCUMENT DESCRIPTION: Journal Article - Exposure of Insulation Workers to Asbestos Dust Work-Environment-Health, Voi. 8, n:o 1, 1971 Exposure of insulation workers to asbestos dust by K a j Ahlman and Eero Siltanen* INTRODUCTION Asbestosis was first described as an occupa tional disease among insulating workers by Ellman (5) in 1934. Since this initial report some hundred other cases of dagger's pneumo coniosis have been described, and this kind of occupation has been recognized as highly hazardous in industrialized countries all over the world. It has also been shown that there is a highly increased risk of lung cancer occurring in persons exposed to dusts con taining asbestos in insulation work (7, 9). The first known case of pulmonary ashes* tosis among insulation workers in Finland was * discovered as early as 1938 (1). The register of occupational diseases at the Institute of Occupational Health in Helsinki now includes a total of 56 cases of insulation workers with pneumoconiosis. In order to obtain more information about the prevalence of asbestosis among insulators, the Institute of Occupational Health carried out a field investigation in 1962--1963 which included all actively working laggers~in the three largest Finnish cities. This investigation was continued after an interval of a few years. The total number of workers examined during the period 1962 through 1968 was 452, nearly three-fourths of all insulators still working in this country. In spite of these examinations, no reliable, current data regarding the true incidence of lagger's pneumoconiosis are available, and even less is known concerning the morbidity of former years. Work produc ing the hazardous dust has been performed in this country for several decades. According to the newly revised law relating to the safety of working environments, however, all workers * Institute of Occupational Health, Helsinki, Finland. must nowadays submit to a periodical exami nation at least once every 3 years. It is obvious that sufficient attention has not yet been paid to the improvement of working conditions. Data on the situation in the varying kinds of insulating work are very scanty since neither systematic checks are made of dust concentrations nor is regular control of the use of personal protective masks performed. To obtain more knowledge on the environ mental conditions of insulating work, the Insti tute of Occupational Health, in connection with an intensified investigation of asbestos hazards in general, recently started a program of measuring dust levels that includes insulat ing work places. INSULATION WORKERS SUFFERING FROM ASBESTOSIS The number of cases of asbestosis diagnosed among insulators before and including 1968 have been given in table 1. They have been arranged according to the year of diagnosis. Table 1. The number of diagnosed cases of asbestosis among insulators in the years 1938--1968. 1938 -- 1946 -- 1952 1953 -- 1957 1958 1959 1 case 2 cases 1 case 1 2 cases 5 3 1960 1961 1962 1963 1964 1965 1966 1967 1968 Total 5 cases 2 5 3 3 * 3 5 4 11 56 cases The duration o f exposure to dust (working time as an insulator) was known in 46 cases 1 i and ranged from 10 to 40 years at the time of diagnosis. The distribution has been shown in table 2 according to the length of exposure, using 5-year groups. Table 2. Distribution of insulation workers with ashestosis according to the length of exposure. Exposure time in years Number of affected persons 10 11--15 16--20 21--25 26--30 >30 Unknown 0 4 9 9 13 12 9 Total 56 The main criterion for accepting a case as asbestosis was the presence of typical radio logical manifestations in the lungs, such as interstitial or focal fibrosis, especially in the middle or lower areas. This was not regarded as sufficient for diagnosis, however, unless it was clearly proved that the patient had a sufficiently long duration of exposure. Pleural' calcifications or thickenings as the only noticeable radiological findings, without a typical occupational history, were not enough to classify the case as anything but suspected asbestosis. The frequency of pleural calcifications or radiologically visible pleural thickenings has been shown in table 3. Some cases have been Table 3.^The frequency of radiologically visible pleural thickenings or calcifications in all cases diagnosed in 1960-1968. Unilateral 9 Bilateral 18 None 14 Total 41 asbestos. Nowadays, in addition to the old compound, mineral wool and glass wool, neither of which contains asbestos, are used for the same purpose. The work of a lagger is very dusty, particularly the repair and demoli tion work that is done in cramped and poorly ventilated places. Protective masks were earlier rarely used, and their use is still often impossible because of cramped working spaces. Many different brands of asbestos materials are manufactured for the thermal insulation of pipes. The lining insulation materials used in pipe insulation work mainly consist of either diatomite and clay or vermiculite diato mite and clay, with only some per cent being amosite asbestos. Bentonite and woodmeal are used as the filler. Surface insulation material contains 20 to 35 % asbestos (antophyllite or chrysotile and a slight amount of amosite) and Portland cement or clay. The asbestos insulation material most commonly used in Finland consists of 70 to 80 % diatomite, 10 to 15 % clay, 5 to 7 % asbestos (chrysotile and amosite), and some per cent vermiculite, woodmeal and gypsum. In the shipbuilding industry sprayed asbes tos insulation is used for ceilings and bulk heads. Even if the material is moistened it causes a lot of dust. Only some years ago the shipyards in Finland started to use non combustible wallboard made of asbestos and calcium silicate. The insides of cabins and corridors, as well as walls and ceilings are lined with the board, a protective measure against fire that is demanded by insurance companies. The board is cut into the required sizes by circular or band saws, which produce plenty of dust. These calcium silicate-asbestos boards contain about 30 % asbestos. excluded because of the uneven technical stan dard of earlier radiographs, and the group presented in the table consists only of the 41 cases diagnosed from 1960 through 1968. TYPE OF INSULATION WORK' AND MATERIALS USED WHICH CONTAIN ASBESTOS The most common type of insulation work in Finland is the thermal insulation of pipes that is done manually, whereas asbestos spraying is rarely used in the building industry. Previously, insulating material was an asbestos compound consisting of clay, diatomite, and ASBESTOS DUST MEASUREMENTS AND STANDARDS In recent years regular dust measurements have been made in the Finnish asbestos in dustry, but very rarely at places where in sulation work is being done or where other asbestos products are being used. ' Methods Particle counting or gravimetric methods have been used for the dust measurements. The samples for counting asbestos dust particles were earlier taken with a midget impinger only (ethyl alcohol being the samp ling medium). They were examined using a 2 * light field microscope with a magnification of 300 x. This year dust samples have also been collected on membrane filters and counted by phase contrast at a magnification of 500 x. All particle concentrations shown on this paper are still counted by the impinger lightfield count technique. The following four ways of counting asbestos dust are used: 1) Counting all particles (fibers and grains smaller than 5 microns ( < 5 pm) 2) Counting all grains larger than 5 microns 3) Counting only fibers as large as 5 to 10 microns 4) Counting fibers longer than 10 microns All particles whose length is at least three times the width are considered fibers. For measuring the total mass concentration of the dust, long-period samples on membrane filters have been taken either from stationary points (Millipore Filter, Type AAWP 037) or from the breathing zone of the workers. Permissible dust concentrations According to American findings concerning asbestos dust particle concentration, a thres hold limit of 175 particles per cubic centi meter ( = 5 mppcf) has been recommended as a ceiling value below which all concentra tions should fluctuate (2), and a threshold limit of 70 particles per cubic centimeter ( = 2 mppcf) has been recommended as a timeweighted average concentration as counted by the impinger light-field count technique (3). The same values have also been recom mended in Finland. In the U.S.A. there has also been a tendency to recommend a thres hold limit of 12 fibers per milliliter for fibers longer than 5 microns, as determined, by the membrane filter method, at least at a phase contrast magnification of 430 x (2). Assuming there to be a 1 % risk of contract ing asbestosis during a 50-year working exposure, the Committee on Hygiene Stan dards of the British Occupational Hygiene Society has recommended the following criteria for limiting exposure to chrysotile asbestos (4): Dust category Negligible Low Medium High Chrysotile concentration* Fibers/ml** <0.5 0 .5 - 2 2-10 >10 * Average during a 3-month period * * Greater than 5/tm in length From these criteria a limit of 100 fibers per milliliter-years was proposed, hence a limit of 2 fibers per milliliter averaged over a 50year period. The same values should also be recommended for all other forms of asbestos, with the exception of crocidolite (8). We have not yet established any recom mendations for asbestos dust mass concentra tions in Finland, but, according to simulta neous, comparable dust measurements- in the plants manufacturing asbestos products, the mass concentration of asbestos dust equivalent to 70 particles per cubic centimeter would be of the order of from 0.7 to 1.0 mg/m3, and the corresponding equivalent to 175 particles per cubic centimeter would be from about 1.75 to 2.5 mg/m3. In the Soviet Union the threshold limit value for dust containing more than 10 % asbestos is 2 mg/m3, and the same value is used in Czechoslovakia. Recently it has been reported (4) that in the Federal Republic of Germany the following values are used as a temporary measure for the assessment of asbestos dust mass concen trations: -- 2 mg/m3, if the asbestos content of processed raw material is below 10 % -- 1.5 mg/m3, if the asbestos content is between 10 and 50 % -- 1.0 mg/m3, if the asbestos content is higher than 50 % RESULTS OF DUST MEASUREMENTS The dust concentrations measured in the air of the breathing zone of workers during the manufacturing o f insulation materials has been given in table 4. The table shows that the measured dust concentrations exceed the recommendations many times, and, therefore, the use of protective masks has been recom mended for the workers until it is possible to employ a more effective method of dust control. Even if only 5.2 % to 8.9 % of all the dust particles in the air are asbestos fibers, the concentration is still very high. Dust concentrations measured during the insulation of ordinary pipe with asbestos insulation material in the building industry have been shown in table 5. The measured concentrations in this work were approxi mately equal to those in the manufacturing of insulation material and are thus very high. The insulation workers, with the exception of one, did not use protective masks because they thought it impossible in the cramped working 3 4 * Table 4. Asbestos duet concentrations measured during the manufacturing of insulation material. Survey No. Operation Particles per cubic centimeter Particles < 5 pm Crains > 5 pm Fibers > 5 pm Fibers >10 pm 1 Loading of elevator (with bags) 439 67 18 10 -- -- 652 63 40 16 Pilling of drum mixer 751 61 44 24 Bagging machines 1,270 175 122 19 2 Loading of elevator 250 36 24 6 Bagging machine 856 128 76 16 3 Loading of elevator 478 146 6 5 Bagging machine 616 139 77 29 Total 534 771 880 1,586 316 1,076 635 861 Table 5. Asbestos dust coiicentrations In insulatiou work in tbe building industry'. Operation Measured dust concentrations Particles per cubic centimeter _ Particles < 5 pm Grains > 5 pm Fibers > 5 pm Fibers > 1 0 fim Total Mixing of the insulation material 660 195 Insulation of pipe, breathing zone 1,380 280 Insulation of pipe, general air 1,090 265 Insulation of pipe, breathing zone 840 160 Insulation of pipe, general air 710 134 53 3 60 26 92 14 61 . 11 34 12 911 1,746 1,461 1,072 990 Mass con centration mg/m* 20.0 -- 20.0 -- f Table 6. Asbestos dust concentrations measured during the sawing of asbestos-calcium silicate boards in a shipyard (Navilite boards). Place of measurement Measured dust concentrations Particles per cubic centimeter Particles < 5 pm Grains > 5 pm Fibers > 5 pm Fibers > 1 0 pin Total Mass con centrations mg/m* Board feeder's breathing zone 1,317 141 86 45 1,589 17.1 Receiver of sawn boards, breathing zone 2,740 308 148 190 3,386 -- -- 2,950 131 220 100 3,401 20.3 -- -- 1,995 197 163 154 2,509 -- General air, 10 m from saw 1,046 82 51 20 1,199 -- spaces. Thus they were obviously exposed to very dangerous asbestos concentrations. Personal, long-period, gravimetric dust samples were also taken from the breathing zone of one worker. Membrane filter monitors were connected to a personal sampler pump worn by a worker who had the filter monitor attached to his collar. The measured mass concentrations were very high. In the shipbuilding industry asbestos dust measurements have been made only once. The results of these measurements have been given in table 6. Also in this work dust samples were taken with portable personal sampler pumps, the membrane filter being attached near the breathing zone. All measured dust concentrations were very high and in dicated an obvious risk of asbestosis. Due to the dust measurements the shipyard has undertaken more effective dust protection 4 measures. A remeasurement of dust levels will determine to what degree these preventive measures have succeeded. CONCLUSIONS The numerous incidents in recent years of verified asbestosis among insulation workers in the construction and shipbuilding industries indicate that previously there was little know ledge about the health risks connected with this work or that such knowledge was simply ignored. The dust measurements of the last few years also clearly indicate that obviously a large number of workers are still exposed to dangerous asbestos dust concentrations. Thus it is extremely important to examine, on a larger scale than previously, the working conditions of workers using asbestos materials in the building industry and in shipyards and to improve the medical and technical protec tion of such workers against the risk of asbes tosis occurring. REFERENCES 1. Ahlman, K. Asbestosis among insulation workers in Finland. International congress on occupational health proceedings, Vienna, (p. 19--24) 1966. 2. American conference o f governmental industrial hygienists (St. Louis, Mo.). Threshold limit values of airborne contaminants for 1968. (May 13) 1968. 3. American conference o f governmental industrial hygienists (St. Louis, Mo.). Supplemental docu mentation of threshold limit values, asbestos -- all forms. Transactions of the thirtieth annual meeting of the American conference of govern mental industrial hygienists (p. 188--191) 1968. 4. Committee on hygiene standards of the British occupational hygiene society. Hygiene standards for chrysotile asbestos dust. Ann. occup. hvg. 11:47--69, 1968. ' 5. Ellman, P. Pneumoconiosis: Part III. Pulmonary asbestosis. Brit. j. radiol. 7:281, 1934. 6. Hasenclever, D. and SchiiU, A. Measurement of dust containing asbestos for assessing asbestos hazards. International conference of pneumoconiosis, Johan nesburg, April 23--May 2, (p. 301--303) 1969. 7. Hinson, K. F. W. Cancer of lungs and other diseases after exposure to asbestos dust. Brit. j. dis. chest 59:121, 1965. - 8. Holmes, S. Personal communication, 1969. 9. Selikoff, /. J., Churg, J. and Hammond, E. C. Asbes tos exposure and neoplasia. J.a.m.a. 188:22, 1964. J