Health impacts of garage workers: a preliminary study.

For this study two garages situated in the Bangkok, Thailand metropolitan area were considered. Garage I employs 45 workers, while Garage II employs 12 workers. Garage I performs engine repair and lubricating, spray painting, and general work (such as washing, welding, etc.) and covers 3,300 square feet of land area. Engine repair and lubricating are the main processes carried out in Garage II which covers 3,600 square feet land area. Garage II is surrounded by four other garages.

In both garages, workers are occupationally exposed to noise, welding fumes, vehicle exhaust gases and hydrocarbons, dust, paints, and solvents. Workers are not provided with appropriate protective equipment. The main objective of this study was to carry out environmental and biological monitoring of the occupational environment and workers and to establish recommendations to improve hazardous conditions affecting work performance of the garage workers.

Environmental (analysis of heavy metals in the air) and biological monitoring (analysis of heavy metals in blood and urine), background noise monitoring, audiometry of workers, and an occupational hygiene survey were also performed.

Experimental Investigation

Air Sampling

Two general sample types, area samples and personal samples, were collected according to the industrial hygiene evaluation of worker exposure to airborne contaminants. Area samples indicate the contaminant concentrations at a selected work site or specific location within a work site whereas personal samples collected contaminants in the "breathing zone" of a worker which indicate the actual amount of contaminant inhaled by an individual worker who is mobile throughout the work site.

A high volume dust sampler was used (Air Monitoring Station, Precision Scientific Company, Chicago, IL 60647, cat no. 6309 1) for area sampling. The casella type personal sampler with open head collector (total dust) and cyclone collector (respirable dust) were used to collect personal dust samples. The duration of dust sampling was eight hours.

The collected dust samples were digested and analyzed for five heavy metals (Cd, Cr, Mn, Ni, and Pb) using Atomic Absorption Spectrophotometer (Shimadzu, model AA-646) 646) (1).

Blood and Urine Analysis

The blood and urine samples of workers of both garages were analyzed for the above-mentioned heavy metals (1). The delta amino levulinic acid test was carried out to exhibit lead exposure (2).

Background Noise

Environmental monitoring for noise was carried out using a sound level meter (Bruel and Kjaer type).

Audiometry

An audiometric examination [Maico, model MA 40, portable audiometer calibrated to the ISO (International Organization for Standardization) recommendations R389 (1964) with dual air conduction earphones] was carried out for 21 workers of Garage I and eight workers of Garage II and compared with the controls. The controls were selected on the following basis: 1. persons who were not occupationally exposed to noise; 2. persons who had no family history of hearing loss before the age of 50; and 3. persons who had not had any type of head injury and who were free from all types of disease.

From the audiogram, the mean Hearing Threshold Levels (HTL) of both ears based on different age groups and different service groups were calculated and compared with that of controls. The classes of the hearing handicap were determined according to the ISO regulations (3). The otoscope examination was carried out to check the inner and outer part of the ear.

Occupational Hygiene Survey

An occupational hygiene survey was conducted in both garages to observe working conditions such as working hours, processes and materials handled, sanitary conditions, social and welfare facilities, health and medical facilities, and safety programs. The questionnaire was prepared according to the WHO Expert Committee Report, (1973), on "Environmental and Health Monitoring in Occupational Health" (4).

Results and Discussion

Air Sampling

The results of air sampling at both garages are given in Tables 1 and 2. Standards were taken from the publication, Notification of the Ministry of Interior-Subject: Safety of Work in Connection with Environment, 1989 (5).

Table 1. Results of High Volume Dust Sampling for Garages I and
II
Parameter        Garage I   Garage II   TLV
(mg/[m.sup.3])

Total Dust         0.45        0.28     15.00
Pb content         0.20        0.12      0.20
Cd content         0.02        0.02      0.20
Cr content         0.02        0.01      1.00
Ni content         0.03        0.06      1.00
Mn content         0.09        0.01      5.00

Table 2. Results of Personal Dust Sampling for Garages I and II
Parameter          Garage I         Garage II
(mg/[m.sup.3)
                Open   Cyclone   Open   Cyclone
                Head             Head

Dust            3.34     0.72    1.46     0.66
Pb content      0.06     0.02    0.06     0.02
Cd content      0.00     0.01    0.00     0.00
Cr content      0.01     0.00    0.00     0.01
Ni content      0.07     0.01    0.05     0.01
Mn content      0.01     0.01    0.01     0.02

In Garage I, average lead content in air was above the standard level. Since Garage II does not carry out spray painting and the work load is less compared to Garage I, dust content and heavy metals in air were lower than those of Garage I.

The concentrations of air contaminants at ground level or rather at lung level are essential in health-related studies. Therefore, personal dust sampling is very important since total dust causes problems in the nasal passage and upper trachea and since respirable dust is one of the major causes of lung disease. Among other things, development of lung disease depends on the amount and kind of dust inhaled, the size of the particles, and the duration of exposure. Clearly depicted in Table 1, the workers in Garage I were more exposed to heavy metals than Garage II workers.

Blood and Urine Analysis

Biological monitoring should be considered as an important adjunct of environmental monitoring, providing an essential link to health effects monitoring. Environmental monitoring may not always yield information of immediate relevance to the assessment of human exposure. A UNEP/WHO Expert Committee (1977) emphasized the need to integrate biological monitoring activities with ongoing environmental activities. Results of the biological monitoring are displayed in Tables 3 and 4.

[TABULAR DATA OMITTED]

[TABULAR DATA OMITTED]

Background Noise

The main sources of noise are electric cutters, electric grinders, and manual work. Figures I and 2 show the noise level variation at different times for Garage I and Garage II.

From these figures it can be observed that most of the time, the noise level has exceeded the 90 dB(A) which is the standard noise level for an eight hour per day work site (6).

In Garage I working hours are from 8:30 a.m. to 4:30 p.m. The workers actually start work at around 9:00 a.m. after taking their morning meals. Therefore, noise levels before work and during the lunch time were lower. In Garage II working hours are from 9:00 a.m. to 5:00 p.m. with a lunch hour between 1:00 p.m. and 2:00 p.m. Throughout the working hours, noise levels of Garage 11 were higher since other nearby garages were working during the non-working periods of this garage.

Audiometric Analysis

The classes of the hearing handicap of Garage I and Garage II workers are provided in Table 5. Table 6 shows the number of workers whose mean HTL exceeds the standards. Figures 3 and 4 show the variation of mean HTL with the service time of Garages I and II.

Table 5. The Classes of Hearing Handicap - Garages I and II

Class of Hearing      No. of Workers
Handicap

                   Garage I   Garage II

A                     11          0
B                     7           4
A/B                   4           0
B/C                   0           2
C                     0           1
C/D                   0           1

Class A - Mean HTL<25dB: no significant difficulty with faint
speech.
Class B - Mean HTL 25-40dB: difficulty only with faint speech.
Class C - Mean HTL 40-55dB: frequent difficulty with normal
speech.
Class D - Mean HTL 55-70dB: frequent difficulty with loud
speech.
According to standards of the Division of Occupational Health of
the Ministry of Health
(3), Mean HTL>/25dB (at 500-2000Hz)
Mean HTL>/35dB (at 3000-6000Hz) are said to be normal.

Table 6. Mean HTL - Garages I and II

No. of Workers           Mean HTL>/25dB        Mean HTL>/35dB
                          (500-2000Hz)          (3000-8000Hz)

                       Lt.   Rt.   Lt./Rt.   Lt.   Rt.   Lt./Rt.
Garage I, 22 workers    6     5       3       5     5       3
Garage II, 8 workers    6     8       6       4     4       3

Lt. = Left Ear; Rt. = Right Ear

From these figures, it can be concluded that the 11-20 year service group of both garages have lower mean HTL than that of the 1-10 year service group throughout most of the frequencies and that Garage II workers are more exposed to noise than Garage I workers. The workers with 20 years of service (age between 37-43 years) show a hearing capacity of a 60-year-old person with no history of exposure to noise (presbycusis curves) (7), especially in the region of 3000-8000 Hz frequency of audiogram.

Figures 5a-f (displayed on page 24) show the comparison of mean HTL with different age groups of Garage I and Garage II workers with the controls. Compared with the controls, the mean HTL of workers at different age groups of both garages are remarkably lower than that of the controls. The 3000-8000 Hz dip in audiogram which indicates the sign of noise-induced hearing loss was more prominent among Garage II workers.

The hearing capacity of Garage II workers was very low since the workers were exposed to noise during their resting periods due to the noise caused by other garages and also due to the location of the rest/meal rooms in the garage. Provisions should be made immediately to minimize the noise problem since the noise-induced hearing loss can be prevented but cannot be cured. The results of the otoscope examination are given in Table 7.

Table 7. Results of the Otoscope Examination - Garages I and II

                          Garage I         Garage II

Otoscope Examination      77% - abnormal   89% - abnormal
                          Lt./Rt. ear      Lt./Rt. ear
Perforation of Ear Drum   14%              20%
Ringing Ear               32%              0
Frequent Earache          27%              0
Frequent Headache         14%              10%

Occupational Hygiene Survey

The occupational hygiene survey carried out in Garage I and Garage II is summarized in Table 8.

[TABULAR DATA OMITTED]

Conclusions

In both garages heavy metals are found in the air. The lead content of air in Garage I has almost reached the threshold limit value (TLV) for lead. The accumulation of dust containing heavy metals can cause severe health problems. Workers of each garage occupationally exposed to lead should undergo medical treatment and should be given a leave of absence from work for an adequate period of time.

Most of the time in both garages, the background noise levels are higher than the threshold limit value for noise (90dB(A). Twelve workers of Garage I and eight workers of Garage II are occupationally exposed to noise and show signs of noise-induced hearing loss. It has been found that the workers suffer from ringing ear problems, frequent earaches, and ear perforations.

In both garages, the rest/meal rooms are located inside the garage. Therefore, workers are exposed to noise, dust, and fumes throughout the work day, including their rest periods. Workers of both garages suffered from red eye, eye pain, gritty feelings in the eye due to exposure to welding fumes, wheezing problems, and breathing difficulties.

Recommendations

Air Quality

1. Since the workers are already affected, workers should be provided with appropriate respirators and eye/face shields.

2. To minimize air pollution due to dust and fumes, the processes which liberate dust and fumes to the environment should be done in enclosed rooms under exhaust hoods.

Noise

1. Noisy processes should be carried out in an enclosed room, and the workers should be provided with ear plugs or ear muffs.

2. Background noise can be reduced a great extent if the walls are covered with noise absorbing materials. However, this requires a large investment and is not feasible for an existing garage since it requires additional construction work. Therefore, environmental authorities should implement regulations for noise control which should be considered before constructing a garage.

Occupational Hygiene Survey

1. Rest/meal rooms should be located away from the working place to prevent workers from exposure to dust, fumes, and noise during rest periods.

2. The environmental authorities should implement some regulations and control measures for noise and dust, which should be considered before constructing a new garage.

3. Since it is difficult to take control measures to minimize environmental factors for an existing garage, it is better to provide workers with protective equipment including appropriate respirators (for dust and fumes); ear plugs or ear muffs (for high noise); eye/face shields (for welding); and gloves (solvents).

4. First aid should be readily available since garage workers are prone to accidents during work.

5. Acetylene gas cylinders should be carefully inspected, maintained, and stored. Any flammable fuel or solvent should be kept as low as possible and containers should be covered.

6. Education programs on occupational safety and health should be conducted for the workers to make them aware of the present situation.

7. Periodic monitoring (every six months) of workers for hearing as well as heavy metals should be conducted.

8. Posters depicting dangers of exposure to noise and other pollutants should be shown in the garages.

9. Smoking within garage premises should be prohibited since flammable solvents are used in garages and severe damage can result to the garage building as well as to workers.

Further research on wastewater management and treatment; a medical diagnostic study on garage workers to paint dust, welding fumes, solvents and noise; a comprehensive study on background noise; and a study on economically feasible control measures for a garage, should be carried out to evaluate occupational problems which would help to control occupational risks leading to a healthier workforce.

References

[1.] Kritalugasane, S., S. Ratanamaneechat, P. Pringsulaka, K. Piriyajittra (1988), Siriraj Hosp Gaz, 40:623-630. [2.] Katsumaro Tomokini and Masana Ogata (1972), Clinical Chemistry, 18(12):1534-1536. [3.] "Preliminary Review on the Occupational Health Situation in Thailand," (1990), Division of Occupational Health, Bangkok. [4.] "Environmental and Health Monitoring in Occupational Health," (1973), WHO-Technical Report Series No. 535. [5.] "Laws and Standards on Pollution Control in Thailand," (1989), Environmental Quality Standards Division: Office of the Natinal Environmental Board, Thailand, 2nd ed. [6.] "Protection of Workers Against Noise and Vibration in the Working Environment," (1980), ILO. [7.] Bies, D.A., C.H. Hansen (1988), "Engineering Noise Control," Unwin Human Ltd., London, 1st ed. [8.] Morgan, W.K.C. (1989), Am Indus Hygiene Assoc J 50(2):59-69.