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Indian Journal of Community Medicine

Pulmonary Function in Automobile Repair Workers

Author(s): O Chattopadhyay

Vol. 32, No. 1 (2007-01 - 2007-03)

Abstract

Background: Automobile repair shop is a place where workers are exposed to harmful chemicals and toxic substances.
Objective: To study the occurrence of obstructive and restrictive pulmonary impairment among automobile garage workers.
Methods: A cross sectional study involving 151 automobile garage workers from 14 randomly selected garages of urban Kolkata. The study variables were Forced Expiratory Volume in 1 second (FEV1), Forced Vital Capacity (FVC), Peak Expiratory Flow Rate (PE FR), age, smoking habit, duration of work, type of work, and respiratory symptoms. The study was analysed using Regression equations, and Chi-square test.
Results: All the workers were male. Obstructive impairment was seen in 25.83% of the workers whereas restrictive impairment was seen in 21.19% of the workers. Mixed obstructive and restrictive impairment was seen in 10.6% of the workers. The frequency of obstructive impairment was higher in older workers. In the age group of less than 20 years, 13.6% of the workers had obstructive impairment while 42.86% of workers above 40 years of age had obstructive impairment. Obstructive impairment was more frequently observed in battery repair workers (58.33%) and spray painters (37.5%) while 16.67% of the body repair workers and 30.19% of the engine mechanics had obstructive impairment. Obstructive impairment was more frequently observed in smokers (53.1 ) as compared to ex-smokers (33.3) and non-smokers (6.4%). Obstructive impairment was more frequently observed in workers who had been working for a longer duration.
Conclusion: Nearly 36.4% of the automobile garage workers had some form of pulmonary function impairment; obstructive and/or restrictive. The use of personal protective equipment, worker education, and discontinuation of the use of paints containing toxic pigments are recommended.

Keywords: Pulmonary Function, Automobile Workers

Automobile repair workers of the informal sector are exposed to dusts, chemicals and toxic substances which are harmful to health. It has been concluded in a study that the small autobody repair shop is an industry in which workers are exposed to hazardous amounts of airborne contaminants1. In another study, a high degree of prevalence of airway symptoms has been reported among autobody shop workers due in part to work related asthma2. The present study was carried out to ascertain the pulmonary function abnormalities in automobile repair workers in an urban area of Kolkata.

Material and Methods

In the Industrial Health Unit of the Urban Health Centre (UHC), Chetla, Kolkata (which is the urban field unit of the All India Institute of Hygiene and Public Health, Kolkata), there are field visit records pertaining to 26 automobile garages of the informal sector in the service area of UHC Chetla. Out of these garages 14 garages were randomly selected. Each of these garages was visited. In these 14 garages there were in all 156 workers but a total of 5 workers refused to get the pulmonary function test done. Therefore 151 workers were interviewed with regard to demographic data, smoking habit, duration of work, type of work and respiratory symptoms. The pulmonary function tests viz. Forced Expiratory Volume in 1 second (FEV1), Forced Vital Capacity (FVC) and Peak Expiratory Flow Rate (PEFR) were measured for each worker with the help of a portable spirometer (Clement Clarke Ventilometer VM1) using American Thoracic Society guidelines. Three readings were taken for each variable and the highest of the three readings was recorded for each of the parameters.

Pulmonary function data which were obtained earlier from 200 healthy male nonsmokers residing in the same geographical area (without occupational exposure to dusts, fumes, chemicals and toxic substances) were used to generate regression equations for LLN (5th percentile) values of pulmonary function parameters. Regression Function of Microsoft Excel was used to generate these regression equations (with age and the square of height as the X variables and the specific pulmonary function parameter as the Y variable). These regression equations are given in Table 1.

Restrictive impairment was diagnosed in a worker if the observed FVC was found to be less than the LLN (5th percentile) of FVC (which was calculated according to the regression equation using the worker’s age and height) associated with a normal FEV1/FVC ratio3. A spirometry record with FEV1/FVC ratio less than the LLN for that subject was categorized as having an obstructive pattern(3).

Table 1: Regression Equations for LLN (5th percentile) of Pulmonary Function Parameters used in this study (where a is the age expressed in years and h is the height expressed in metres).

Pulmonary function Parameter Regression equation Values of
q,r,s,t,x,y, for
age less
than 20 years
Values of
q,r,s,t,x,y, for
age of 20
years above
Peak expiratory flow rate (litres/minute) PEFR=aq+rh2 q=3.954 r=108.05 q= -2.28 r=160.2
Forced expiratory volume in 1 second (litres) FEV1=as+th2 s=0.0696 t= 0.346 s= -0.0084 t = 0.882
Forced vital capacity (litres) FVC =ax yh2 x = 0.036 y= 0.561 x= -0.013 y = 0.96

Note: As q,s and x are negative for age of 20 years and above, the pulmonary function parameters steadily decline as the age increases after the age of 20 years.

Table 2: Distribution of Pulmonary function Status of Automobile Repair Workers according to Age Group.

Age in
Year
Normal
Pulmonary
function
Obstructive
impairment
only
Restrictive
impairment
only
Both
obstructive
and
restrictive
impairment
Total
(1) (2) (3) (4) (5) (6)
< 20 48 8 9 1 66
20-29 22 6 3 2 33
30-39 13 5 1 5 24
> 40 13 4 3 8 28
Total 96 23 16 16 151

Obstructive impairment (Columns 3 and 5 together)
Restrictive impairment (Columns 4 and 5 together)
Obstructive impairment vs No obstructive impairment. p = 0.0005
Restrictive impairment vs No restrictive impairment. p = 0.04

The observations were tabulated and analysed. Chi-square test was applied for testing the significance of the difference in proportions. For this purpose, the Chitest function of Microsoft Excel was used and the p values were obtained directly.

Results

A total of 151 automobile workers were studied. All of them were male. Obstructive impairment was seen in 25.83% of the workers whereas restrictive impairment was seen in 21.19% of the workers. Mixed obstructive and restrictive impairment was seen in 10.6% of the workers. The pulmonary function abnormalities in workers and their relation to age, type of work, smoking habit and years of work are presented in Tables 2 to 3. It may be noted than in Tables 2 to 5, Columns 3 and 5 taken together constitute obstructive impairment while Columns 4 and 5 taken together constitute restrictive impairment.

Table 2 shows that obstructive impairment was more frequently observed in older workers. In the age group less than 20 years, 13.64% of the workers had obstructive impairment. Obstructive impairment was seen in 24.2% of the workers in the age group 20-29 years and in 41.67% of the workers in the age group 30-39 years. In the age group 40 years and above, 42.86% of the workers had obstructive impairment. The difference in the proportion of workers with obstructive impairment in different age groups is statistically significant (p< 0.01). Restrictive impairment was seen in 15.15% in the age group less than 20 years, 15.15% in the age group 20-29 years, 25% in 30-39 years while it was 39.29% in the age group of 40 years and above. Restrictive impairment was also more frequent in older age groups and the difference is significant (p=0.04).

Table 3: Distribution of Pulmonary Function Status of Automobile Repair Workers according to Years of Work.

Age in
Year
Normal
Pulmonary
function
Obstructive
impairment
only
Restrictive
impairment
only
Both
obstructive
and
restrictive
impairment
Total
(1) (2) (3) (4) (5) (6)
< 5 43 7 11 1 62
5-10 21 5 2 2 30
> 10 32 11 3 13 59
Total 96 23 16 16 151

Obstructive impairment vs No obstuctive impairment. p = 0.002 Restrictive impairment vs No restrictive impairment. p = 0.146 The obstructive impairment was more frequently observed in battery repair workers (58.33%) and spray painters (37.5%) while 16.67% of the body repair workers and 30.19% of the engine mechanics had obstructive impairment. The occurrence of restrictive impairment was also highest in battery repair workers (50%), while it was 17.95% in body repair workers, 20.75% in engine mechanics and 12.5% in spray painters.

Obstructive impairment was more frequently observed in smokers. In smokers, 53.06% of the workers had obstructive impairment.

Obstructive impairment was seen in 33.33% of the workers in ex-smokers and in 6.4% of the workers in non-smokers. The difference in the proportion of workers with obstructive impairment in different smoking habit categories is statistically significant (p <0.0001). Restrictive impairment was seen in 28.57% in smokers, 20.83% in ex-smokers and in 16.67% in non-smokers. Restrictive impairment was also more frequent in smokers but the difference is not significant. Table 3 shows that obstructive impairment was more frequently observed in workers who had been working for a longer duration. In the workers who had been working for more than 10 years, 40.68% had obstructive impairment. Obstructive impairment was seen in 12.9% of the workers who had been working for less than 5 years and in 23.33% of the workers who had been working for 5-10 years. The difference in the proportion of workers with obstructive impairment in different durations of work is statistically significant (p = 0.002). Restrictive impairment was seen in 19.35% in workers working for less than 5 years, 13.33% in workers working for 5-10 years and 27.12% in workers working for more than 10 years. Restrictive impairment was more frequent in workers working for more than 10 years but the difference is not significant.

Discussion

According to a recent publication of the American College of Occupational and Environmental Medicine (ACOEM), the use of a fixed cutoff of 80% of predicted as the Lower Limit of Normal (LLN) with regard to the pulmonary function parameters (FEV1, FVC, PEFR) is no longer recommended. Instead ACOEM recommends the use of 5th percentile values (the point below which 5% of normal subjects fall) as the LLN values4. In the present study, the 5th percentile values of non-smoking subjects residing in the same geographical area (without occupational exposure to dusts, fumes, chemicals and toxic substances) have been used as reference values and these have been expressed as regression equations with the age and the square of height as the X variables. LLN values of pulmonary function parameters used in this study thus conform to the latest ACOEM recommendations.

In the present study, obstructive impairment was seen in 25.83% of the automobile repair workers whereas restrictive impairment was seen in 21.19% of the workers. In the study on autobody repair workers by Parker et al, obstructive impairment was seen in 26.3% of the workers and restrictive impairment was seen in 7.9% of the workers5. In the study on autobody shop workers by Cullen et al, almost one fifth of all workers had obstructive impairment. A restrictive defect on spirometry can be frequently misleading. In fact, a reduction in vital capacity may as well be related to an obstructive defect and may be falsely used to diagnose restriction6. A true restrictive defect can be diagnosed only on demonstration of a reduced total lung capacity3.

In the present study, obstructive impairment was more frequent in the workers who smoked and the difference is statistically significant. Similar observation has been reported by Parker et al5 and Cullen et al2. In the present study, the finding of an increased frequency of restrictive impairment in smokers is not statistically significant. Parker et al did not find any increase in restrictive impairment with smoking5.

In the present study, a high frequency of obstructive impairment was observed in battery repair workers and spray painters. Parker et al found that FEV1 and FVC decrements were significantly associated with a nonfunctioning paint booth and the prevalence of obstructive impairment in nonsmoking workers was significantly associated with spray painting. There is a possible link between respiratory difficulties and exposure to isocyanate containing spray paint. Isocyanate concentrations ranged from below the limit of detection to 0.06 parts per million and exceeded ACGIH guidelines in seven of the 39 autobody shops5.

In the present study, obstructive impairment was more frequently observed in workers who had been working for a longer period of time. Parker et al found that FEV1 and FVC decrements were significantly associated with years worked in the autobody repair trades5.

Jayjock and Levin in a study of automobile repair shops have reported that although full time weighted average shift toxic limit values for solvents were rarely exceeded, the short term exposure limits were often greatly exceeded. Dusts from plastic grinding or from fibrous glass compounding reached concentrations as high as 39.8 milligrams per cubic metre in one sampling period and probably frequently exceeded the dust toxic limit value. The use of personal protective equipment, worker education, and identification of paints containing toxic pigments have been recommended1. In the present study, nearly 36.4 per cent of the automobile repair workers examined were found to have impairment of pulmonary function, obstructive and/or restrictive. The study highlights the hazardous nature of the work of the automobile repair workers.

Acknowledgement

The assistance provided by Mrs Anjali Patra, Health Assistant (Female), Urban Health Centre, Chetla, in conducting workplace visits is gratefully acknowledged.

References

  1. Jayjock MA, Levin L. Health hazards in a small automotive body repair shop. Annals of Occupational Hygiene, 1984, 28(l): 19-29.
  2. Cullen MR, Redlich CA, Beckett WS, Weltmann B, Sparer J, Jackson G, Ruff T, Rubinstein E, Holden W. Feasibility study of respiratory questionnaire and peak fl ow recordings in autobody shop workers exposed to isocyanate-containing spray paint: Observations and limitations. Occupational Medicine, 1996, 46(3): 197-204.
  3. Aggarwal AN, Gupta D, Behera D, Jindal, SK. Applicability of commonly used Caucasian prediction equations for spirometry interpretation in India. Indian J Med Res, 2005, 122(2): 93-186.
  4. Parker DL, VValler K, Himrich B, Martinez A, Martin F. A cross-sectional study of pulmonary function in autobody repair workers. American Journal of Public Health, 1991, 81(6): 768-771.
  5. Townsend MC, Lockey JE, Velez H. Spirometry in the occupational setting: ACOEM position statement. Journal of Occupational and Environmental Medicine, 2000, 42(3): 228-245.
  6. Jindal, SK. Spirometry: Pitfalls and Interpretation. Indian J Chest Dis Allied Sci, 2001; 43(4): 1993 -195.

All India Institute of Hygiene & Public Health,Urban Health Centre,
Chetla,19 B Chetla Hat Road,Kolkata – 700027
Received: 6.7.05

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