American Journal of Industrial Medicine 2 1 5 6 1 4 6 7 (1992)

Parenchymal and Pleural Fibrosis in Construction Workers Panu Oksa, MD, Heikki Koskinen, MD,Jouko-Pekka Rinne, MD, Anders Zitting, MD, Pekka Roto, MD,MIH, and Matti S. Huuskonen, MD, MSC

Exposure to mineral dust was studied among construction workers (N = 437) with the aid of a questionnaire and a chest X-ray examination of the lungs. The results of the questionnaire showed that 8 1% of the construction workers had been exposed to asbestos. Exposure had occurred in all of the occupational groups studied. Pleural plaques and/or lung fibrosis (ILO 2 1/1) were found in 26% of the examined workers; the prevalence varied from 18 to 40% among the various occupational groups. Comparison with a representative sample of the Finnish male population from another investigation indicates that the frequency of lung fibrosis (ILO 2 1/1) is at least two times higher among the examined construction workers than among the general population. It seems likely that exposure to asbestos dust can be considered an etiological factor for an appreciable number of the X-ray findings. Key words: asbestos, chest radiograph, occupational screening, silica exposure, construction work

hazards

INTRODUCTION Asbestos has been used in Finnish building construction ever since the 1920s. The peak of asbestos use occurred in the 1960s and 1970s, when annual consumption reached more than 10,OOO tons (total use in the 1900s > 300,000 metric tons) [Huuskonen et al., 19871. The construction industry is estimated to account for as much as 80% of the asbestos used in our country. According to the Finnish Employment Pension Fund, over 200,000 workers (the total active work force in Finland currently being about 2.3 million) were employed in the construction industry at the end of the 1960s. The prevalence of pneumoconiosis in the construction industry has been studied in such specific occupational groups as insulators, plumbers, pipefitters, sheet metal workers, and female construction workers [Baker et al., 1985; Fischbein et al., 1979; Kivekas, 1989; Michaels et al., 1987; Soda and Yamazaki, 1981; Sprince et al., 19851 and among workers with known asbestos exposure [Hedenstierna et al., 19811. Existing prevalence data are thus limited to workers with established mineral dust exposure. However, many other occupational groups in construction work may be Institute of Occupational Health, Helsinki, Finland. Address reprint requests to Dr. Panu Oksa, Tampere Regional Institute of Occupational Health, P.O. Box 486, SF-33101 Tampere, Finland. Accepted for publication September 25, 1991.

0 1992 Wiley-Liss, Inc.

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exposed to asbestos and quartz dusts. The rapid turnover of the work force, changing workplaces, the number of work tasks, and the continually changing work conditions make the evaluations of dust exposure in construction work difficult [Grandjean, 19831. In the construction industry, direct asbestos exposure occurs among workers who handle asbestos (such as pipe insulators and persons working with asbestoscontaining board). The asbestos fiber concentration in the breathing zone of these workers can be as high as tens of fibers per cubic centimeter [Health and Safety Executive, 1984; Huuskonen and Tossavainen, 1978; Paik et al., 19831. In addition, many construction workers have been exposed indirectly to asbestos dust, even though they are not aware of such exposure themselves. Many groups of workers in the construction industry are also exposed to quartz dust. In practice quartz dust is always created during the use of materials containing stone. Typical of these work tasks are stone dressing, drilling, and cement sanding. In Finland respirable quartz dust exposure has varied between 0.1 and 16 mg/m3 (short-time exposure) [Ahonen et al., 19771. In the 1970s and 1980s, between 10 and 20 cases of asbestos-related diseases (mainly asbestosis) among construction workers were reported to the Finnish Occupational Disease Register annually. Concurrently, 3 to 10 cases of silicosis were reported to the same register. However, in the last few years the number of registered asbestos-related diseases has considerably increased. In 1988, 66 cases of asbestosrelated diseases among construction workers were reported to the Register (26 cases of asbestosis, 30 of non-malignant pleural disease, 7 of mesothelioma, and 3 of lung cancer). The present study was initiated in 1987 to obtain information on asbestos exposure among construction workers. We used a questionnaire survey on work tasks involving asbestos and quartz dust exposure and a chest X-ray examination to detect possible asbestos-related radiographic findings. We assumed that the radiographic findings would be useful for revealing asbestos exposure unidentified by the questionnaire and would thus aid the estimation of indirect asbestos exposure. SUBJECTS AND METHODS

Members of three sections of the local union of construction workers in the area surrounding the city of Tampere, Finland, were selected for screening. One section was made up of pipefitters, one included pipe insulators, and one comprised carpenters, laborers, concrete workers, concrete reinforcement workers, cement workers, bitumen insulators who insulate roofs with asbestos containing bitumen, concrete production workers, and machine operators. Painters, bricklayers, and roofplaters were not included in these sections. Only those persons who had been union members already in 1967 were accepted. All eligible persons (N = 993), either working or retired, were included. The 993 subjects were sent a questionnaire on such topics as their job, work tasks, and asbestos exposure. They were also offered a health examination; 437 (44%) filled out the questionnaire, participated in the clinical examination, and were included in the analysis. Half of the 437 studied subjects were retired and half were actively working. Ninety-three percent were men. The subjects’ mean age was 59 years (range 35-85

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years). Most had begun working in the construction industry in the 1950s or 1960s (range 1918-1 967). The health examination was carried out in the mobile clinic of the Institute of Occupational Health. The subjects were interviewed with respect to exposures, lung and chest diseases and injuries, and smoking habits. A postero-anterior full-size chest X-ray was taken. Asbestos exposure was calculated in whole workdays from responses to the questions about direct and indirect exposure on the questionnaire. These responses were given additional attention at the interview during the health examination. The subjects were asked to recall their work in the mentioned work tasks with asbestos or quartz exposure and to estimate how long these work tasks lasted in hourdday, daydweek, weekdyear, and so forth. This interview between the nurse and the worker took about 30 minutes. Direct exposure was considered to occur in: asbestos spraying; mixing and spreading of asbestos-containing substances; the use of asbestos-containing paint, glue, and putty; repair work involving the demolition and cleaning of asbestos-containing structures; and the handling of asbestos-containing material, for example in the installation and working of asbestos cloth, asbestos board, and asbestos cement board. Work on renovation sites where someone else did asbestos removal work, and work in areas in which asbestos was handled by other persons were considered indirect asbestos exposure. Workers were classified as exposed to quartz if their tasks involved exposure to stone dusts, namely, clearing, dressing, drilling; machine sanding, cement mixing, work on roofs, smoothing or leveling of floors, walls, and roofs, and demolition of brick structures. Radiographic changes indicating fibrosis were classified into four groups as no (i.e., normal) (ILO 0/- -O/O), some (ILO O/l-l/O), moderate (ILO l/l-1/2), or abundant (ILO 2 2/1) changes [International Labour Office, 19801. Plaques were categorized into the following groups without a more precise quantification or determination of location: none, uncertain (meaning suspicion of plaque and unilateral plaques), or definite. Pleural plaques were classified as definite when there was bilateral circumscribed pleural thickening with or without calcification, or typical bilateral pleural calcification without adhesions. Thickening of the visceral pleura and pleural adhesions were classed as none, some, or definite. The classification of the chest X-rays was performed by one radiologist (A.Z.), who had also classified the chest x-rays in another Finnish study that gave an idea of the prevalence of lung and pleural fibrosis in the Finnish population [Zitting et al., 19901.

RESULTS

Eighty-one percent of the construction workers we examined reported exposure to asbestos dust on the questionnaire. The average duration of exposure (calculated as whole workdays) was 3.7 years. Exposure to silica dust was reported by 89% of the subjects, the average duration being 4.9 years (Table I). Exposure to asbestos and to silica was found in every occupational group (Table I). Pipe and bitumen insulators, pipefitters, and carpenters were especially prominent in the asbestos-exposed group. The occupational groups showing the most exposure to silica dust were female and male laborers, carpenters, cement workers, and the group “others” (renovators, rug installers, etc.). The difference in quartz exposure

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TABLE I. Mean Duration of Exposure to Mineral Dusts as Reported by Questionnaire in 437 Finnish Construction Workers, 1987-1988 Exposure (years) Occupational group Pipe insulators (N = 5) Bitumen insulators (N = 15) Pipefitters (N = 80) Carpenters (N = 146) Female laborers (N = 27) Male laborers (N = 42) Cement workers (N = 30) Concrete reinforcement workers (N = 25) Others (N = 67) Total (N = 437)

Percentage of exposed

Asbestos

Quartz

Asbestos

Quartz

43.9 9.0 5.0 3.2 3.0 2.5 1.7 0.4 2.1

0.4 3.8 1.7 3.6 13.1 8.7 4.7 1.5 7.2

100 33 95 94 85 74 83 36 63

40 73 79 93 93 98 97 76 90

3.7

4.9

81

89

reported by the female and male laborers was associated with type of job; for instance, female laborers more often spent long periods cleaning, which is dusty work. Radiographic findings indicating lung fibrosis ILO 2 1/1 were apparent for 70 subjects (16%), in 9 (2%) of whom lung fibrosis was interpreted as ILO 2 2/1. The prevalence of lung fibrosis of these levels ranged from 6 to 40% in the various occupational groups (Table 11). The shape of the small lung opacities was almost always irregular (99%); in only two persons was it partly or completely nodular

(0.8%). Bilateral definite pleural plaques were found in 6 1 workers (1 4%) and unilateral or suspected plaques were detected in 112 workers (26%). Depending on the occupational group, 18 to 40% of the examined subjects had lung fibrosis of the categories mentioned and/or definite pleural plaques. The highest prevalence was found for pipe insulators (40%) and carpenters (32%) (Table 11). Definite “diffuse” pleural thickening and pleural adhesions indicating changes of the visceral pleura were found in 38 persons (9%). The occurrence of radiographic changes was associated with asbestos exposure, whereas only a slight trend was found for quartz exposure (Table 111). Table IV shows the radiographic findings in relation to employment in the construction industry. There was a trend towards a higher prevalence of findings with a longer length of employment. The trend was more obvious when both parenchymal and pleural findings were taken into consideration. Table V shows the prevalence of small irregular opacities in relation to smoking habits. The prevalence of pleural plaques was not related to smoking habits.

DISCUSSION We found radiographic changes indicating lung or pleural fibrosis in one-fourth of the construction workers we examined in our survey. The prevalence of X-ray findings was rather high in all of the occupational groups. Small irregular opacities, predominantly in the low and central parts of the lung were seen. This observation indicates interstitial lung fibrosis typical of asbestos-related disease. On the other hand, nodular shadows typical of silicosis were found in only 0.8% of the examined

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TABLE 11. Occurrence of Small Opacities and Pleural Plaques in 437 Finnish Construction Workers, 1987-1988 Workers with pleural plaques

Workers with small opacities Occupational group pipe insulators (N = 5) Bitumen insulators (N = 15) Pipefitters (N = 80) Carpenters (N = 144) Female laborers (N = 27) Male laborers (N = 42) Cement workers (N = 30) Reinforcement workers (N = 25) Others (N = 67)

Total (N = 437)

ILO

ILO

01- -010

0/1-1/0

I(20%)

ILO 111-1/2

2 (40%) 2 (40%)

[LO

> 211 -

7 (47%) 7 (47%) I(6%) 41 (51%) 31 (39%) 7(9%) 1(1%) 61 (42%) 58 (40%) 25 (17%) 2 (1%) 14 (52%) 9 (33%) 4(15%) 13 (31%) 19 (45%) 7 (17%) 3 (7%) 9 (30%) 15 (50%) 5 (17%) 1(3%)

None 5 (100%)

Uncertain

Definite"

0 (0%)

0 (0%)

10 (67%) 45 (56%)

2 (13%) 23 (29%) 87 (60%) 30 (21%) 19 (70%) 5 (19%) 25 (60%) 14 (33%) 20 (67%) 6 (20%)

Workers with lung fibrosis 2 ILOl/l and/or definite pleural plaques

2 (40%)

3 (20%) 12 (15%) 29 (20%) 3 (11%) 3 (7%) 4 (13%)

47 (32%) 5 (19%) 11 (26%) 9 (30%)

16 (64%) 7 (28%) 2(8%) 12 (48%) 9 (36%) 4 (16%) 30 (45%) 27 (40%) 8 (12%) 2 (3%) 41 (61%) 23 (34%) 3 (4%) 192 (44%) 175 (40%) 61 (14%) 9 (2%) 264 (60%) 112 (26%) 61 (14%)

6 (24%) 12 (18%) 113 (26%)

3 (20%) 18 (23%)

"See definition in text.

TABLE 111. Chest X-Ray Findings in Relation to Mineral Dust Exposure in 437 Finnish Construction Workers, 1987-1988 ~

Exposure (months) Finding Small opacities ILO 0/- -O/O, no pleural plaques Small opacities ILO 0/1-1/0 and/or uncertain pleural or unilateral plaques Small opacities ILO 2 1/1 and/or definite pleural plaques

N

Asbestos Quartz

135

32

55

189

45

59

113

5ga

62

ap = 0.02 (versus no finding).

subjects, even though many (89%) of the subjects reported exposure to silica dust. In addition, 40% of the workers showed pleural plaques (definite bilateral, unilateral, or suspected). It seems, therefore, likely that exposure to asbestos dust was an etiological factor for an appreciable number of the chest X-ray findings. The occurrence of radiographic changes ILO 2 1/1 in the examined construction workers was 16%, and when adjusted for age in respect to the general Finnish male population, 8.8%. This adjusted rate is two times higher than that of another study in which, among an unselected, representative sample of the 3,280 Finnish males, the occurrence of small opacities ILO 2 111 (age adjusted for the general Finnish male population) was 4.4% (Zitting et al., 1988; Aromaa et al., 1989). As in earlier studies [Hedenstierna et al., 1981; Michaels et al., 1987; Sprince et al., 19851, we found a rather high prevalence of non-malignant pleural changes and small opacities in X-rays of workers in occupational groups which typically experience asbestos exposure. Our study included almost all of the trades in the construction industry, and we found that all of the groups studied showed a similar prevalence of X-ray changes. This observation seems to indicate that all construction workers

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TABLE IV. Occurrence of Radiographic Abnormalities in Relation to Length of Employment in 436 Finnish Construction Workers, 1987-1988

Length of employment (Yeas)