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The health of the workers in a
rapidly developing country:
effects of occupational exposure
to noise and heat
J. Gomes*, O. Lloyd† and N. Norman†
*Department
of Community Health & Epidemiology and Centre for Agricultural Medicine,
University of Saskatchewan, Saskatoon, Canada; and †Department of Community Medicine,
Faculty of Medicine & Health Sciences, UAE University, United Arab Emirates
Occupational hygiene and safety have not been high on the agenda of industrial
management in developing countries for a variety of reasons. This cross-sectional
study was undertaken to assess the exposure to noise and heat, and to study the
level of occupational hygiene practiced, at a foundry in a rapidly developing country
(Dubai, United Arab Emirates). Audiometry, muscle cramps and visual acuity were
measured in workers at a foundry and compared with the results from workers at a
soft-drink bottling plant. Thermal stress, relative humidity, ventilation, illumination and
noise levels were measured at different work units at the foundry and at the soft-drink
bottling factory. Thermal stress index was high while relative humidity and ventilation
were low at the foundry compared with the bottling plant. Noise levels were also high
at the foundry, exceeding 90 dB at almost all work units except the fabrication
workshop. Mild or moderate visual defects were observed among 31% of foundry
workers, compared with 19% of the bottling plant workers. Muscle cramps were
reported by 30% of all workers at the foundry, compared with 5% at the bottling
plant. Visual disability was the highest among furnace operators and fabricators.
Mean hearing disability was 8.69 ± 1.08% among foundry workers, compared with
4.56 ± 0.82% among bottling plant workers. The high thermal stress, noise levels
and exposure to non-ionizing radiations at the foundry might have contributed to the
higher frequency of muscle cramps and the greater hearing and visual disabilities,
respectively, among these workers. Non-use of personal protective equipment and
poor occupational hygiene and safety measures were also seen to affect eye and ear
health adversely among the workers at the foundry.
Key words: Foundry; hearing disability; muscle cramps; noise; thermal stress;
ventilation; visual disability.
Received 28 June 2001; revised 4 February 2002; accepted 11 March 2002
Introduction
In many rapidly developing countries, where labour is
cheap, proper occupational hygiene and pollution control
methods are often neglected at worksites. Protective
equipment for factory workers is considered a luxury, and
is hence not provided. The workers, being economic
Correspondence to: J. Gomes, Department of Community Health &
Epidemiology and Centre for Agricultural Medicine, University of
Saskatchewan, 103 Hospital Drive, Saskatoon, Saskatchewan
S7N 0W8, Canada. e-mail: [email protected]
migrants, accept adverse conditions as part of the job,
and do not demand hygiene measures and personal protective equipment. As a result, workers in these countries
tend to be exposed to excessive amounts of both physical
and chemical pollutants. Foundry workers, in particular,
are routinely exposed to dust, gases, fumes and heat,
amongst other pollutants [1]. The level of exposure to
these pollutants depends on many factors, chief amongst
them in this context being the level of occupational
hygiene and pollution control methods employed in the
factory. Reductions in the exposure levels could be
Occup. Med. Vol. 52 No. 3, pp. 121–128, 2002
Copyright © Society of Occupational Medicine. Printed in Great Britain. All rights reserved. 0962-7480/02
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Occup. Med. Vol. 52, 2002
brought about, primarily, by implementing appropriate
measures to control chemical and physical pollutants in
the work environment, and secondarily, by providing
personal protective equipment to the exposed workers.
We have previously reported that the level of occupational hygiene is low and that pollution control methods
are poorly implemented at the foundry under study (in
Dubai, United Arab Emirates) [1]. We found impaired
pulmonary function among workers exposed to dusts,
fumes and gases, with the risks exacerbated through the
failure to use personal protective equipment [1]. Safety
and occupational hygiene practices in newly industrializing countries such as the Arabian Gulf States are largely
ignored, resulting in increased exposures to unsuspecting
and needy economic migrants working in these countries.
Pulmonary function impairment has been described as
one of the major adverse health effects in steel factory
workers [2, 3]. Noise-induced hearing loss has also
been reported in steel workers [4] and metal fabrication
workers [5]. Other investigators have reported on the
mortality from injuries among steel workers [6], and on
the cancer incidence and mortality in them [7–9]. Most of
these studies have been in rapidly developing countries,
where occupational hygiene and the use of personal
protective equipment have not been given the attention
they deserve. Moreover, the use of personal protection is
often ignored in tropical countries because of the hot and
humid climatic conditions, which make the use of these
devices impractical. However, the broader spectrum of
chronic health problems resulting from exposure to heat,
dust, gases and fumes at iron and steel factories in developing countries has not been systematically described.
The semi-skilled and unskilled workers from the lesserdeveloped countries who work in these rapidly developing
countries are contract workers, and are usually untrained
in the job they are employed to do. Being mostly economically underprivileged and anxious to retain their
jobs, the workers accept adverse working conditions
and do not demand health and safety measures. Therefore, this study was designed to assess the practice of
occupational hygiene and safety at the worksite, and to
investigate adverse health effects among foundry workers
in a rapidly developing country in a desert environment.
The problems of noise, heat, ventilation and hygiene at
various worksites were assessed. The practice of occupational hygiene, the implementation of control measures
and the use of personal protection were also evaluated,
together with their associations with the degree of health
impairment. Thermal stress, muscle cramps, and visual
and hearing disabilities were also examined.
Methods
Those workers involved in the production process
(exposed) at the foundry were invited to participate in the
study; all agreed to participate, and so all were included.
As an unexposed group, all workers working at a softdrink bottling plant were also invited to participate in the
study, and all were included since none refused to
participate. Only those workers on annual or other leave
during the period of the study did not participate. The
management of the factories provided a list of workers,
their job titles and their ages, along with the layout of
different work units within the factory. Having made
prior arrangements with the management of the factory,
an appointment was made with the production supervisors to conduct the study on specified days during the
study period.
The exposed workers worked in shifts round the clock,
while the unexposed workers worked only on the general
shift. The supervisors requested those workers who had
been off duty for at least the past 8 h to report to the site
laboratory before beginning their shift, to participate in
the study. At the site laboratory, the procedures to be
applied were explained to the workers, and their willingness to participate in the study was confirmed by their
signing the consent form. The Ethical Committee of the
Medical Faculty had earlier given ethical clearance for the
procedures to be applied in the study, including the use of
a questionnaire.
A specifically designed questionnaire was used to
collect information on socio-demographic characteristics,
general health profile, current medication, use of personal protective equipment at work, water consumption
through the day and intake of salt tablets. The questionnaire was used for both the exposed and the unexposed
workers, even though there were differences in the working conditions and the need to use personal protective
equipment while at work. Since all the workers were
of Asian origin and some were unable to converse in
English, the questionnaires were applied to all the participants through an interviewer, in their local language
(Urdu). Prior to using the questionnaire in their local
language, the questionnaire was back-translated twice
into Urdu and pilot tested. The comparability of demographic characteristics between the foundry and bottling
plant workers has been described elsewhere [1].
Height and weight were measured at the site laboratory
for all workers participating in the study. The body mass
index (BMI) was calculated as the ratio of weight (in
kilograms) to height (in metres) squared. The mean ages
and BMIs of the workers at the foundry and those at the
bottling plant were similar [1].
Visual acuity was measured, using Snellen’s chart, for
all the exposed and unexposed workers participating in
the study. A score of 6/6 on Snellen’s chart was considered
as normal vision, 6/9 as mild defect and 6/12 or greater
as moderate-to-severe defect. Visual acuity was measured
in each eye separately, and an average of the left and
the right eye was used to represent a value for both
J. Gomes et al.: Worker health in a rapidly developing country
eyes. Audiometric tests were conducted using a clinical/
diagnostic audiometer, Midimate 622 (GN Otometrics
A/S, Taastrup, Denmark), for all the exposed and unexposed workers participating in the study. The mean
values of the left and the right ear audiometric profiles of
the group of workers, identified by job title and performing similar tasks, were compared with the mean values
for other groups. Sound pressure levels and octave band
frequency analyses in the foundry and the bottling plant
affecting the workers as they performed the various
tasks at the different worksites were correlated with the
workers’ audiometric profiles.
Measurements for noise levels, dry and wet bulb
temperatures, air speed, illumination and humidity were
taken during the normal operation and on a normal
working day at the foundry and the bottling plant. These
measurements were taken at all sites usually manned by
workers, both at the foundry and at the bottling plant. The
wet bulb globe temperature (WBGT) index was recorded
as a measure of thermal index as reported by a Thermal
Stress Monitor (Questemp, Audiometrics, Inc., LA,
USA). Relative humidity was measured using a whirling
hygrometer (Cassella Ltd, London, UK). Air speed was
measured using an air vane (Wheaton Inc., NJ, USA)
and illumination was measured using a lux meter
(Wheaton Inc., NJ, USA). Noise frequency measurements were made using a Precision Sound Level Meter
Type 2232 (Bruel & Kjaer, Huddinge, Sweden). All the
measurements at both sites were taken at the end of the
summer season (September/October), when the ambient
environmental temperatures were between 35 and 45°C.
Hearing disability was assessed for the workers at
the iron foundry and those at the bottling plant according to the method described by the American Medical
Association/American Academy of Otolaryngology Formula (AMA/AAO) for the determination of hearing
disability [10–12]. Hearing disability was also calculated
for comparison according to the British Association of
Otolaryngologists (BAOL)/British Society of Audiologists
(BSA) method [13].
The workers at the foundry (the exposed group)
123
were assigned to different work units within the foundry.
These tasks within the assigned work units were rotated
approximately every 2 years within the unit. At the
soft-drink bottling plant, the workers (the unexposed
group) attended to the automatic bottling tasks at the
factory or were dispatched to supply the finished products
to the retailers. Since these tasks were switched between
workers on a daily basis, no categorization of tasks was
carried out for them.
Means and SDs were used to characterize the different
parameters for thermal stress, ventilation and illumination, and geometric means and SEs were used for octave
band frequency analyses and sound pressure levels;
frequencies and percentages were used to describe water
consumption, muscle cramps and use of protective equipment while at work. The χ2 test was used to compare
frequencies for visual acuity, water consumption and
muscle cramps. An independent sample t-test was used
to compare thermal stress, ventilation, illumination and
noise levels at the foundry and the bottling plant. Visual
and hearing disabilities were estimated using the factorial
multivariate regression analysis general linear model
from Statistical Package for Social Sciences (SPSS) [14].
General linear model analysis was used to estimate the
visual and hearing disability values for the exposed and
unexposed workers, with age and BMI as covariates in the
model.
Results
The Thermal Stress Monitor only displayed the dry bulb
(DB) and wet bulb (WB) temperatures, and the WBGT
index for indoors (WBGTin index) (Table 1). The DB
temperature ranged between 32.6 and 36.5°C, the
WB between 25.7 and 27.3°C. The WBGTin index was
calculated by the equation
WBGTin = 0.71Twb + 0.3Tg
where Tg is globe temperature and Twb is wet bulb
temperature. The mean ambient WBGTin at all work
Table 1. Thermal stress, relative humidity, air speed and illumination at different work units in the iron foundry (values are mean ± SD)
Work unit
DB (°C)
Furnace
Continuous casting
Rolling mill
Mechanical workshop
Fabrication workshop
36.50
35.81
36.22
32.64
36.05
± 1.80
± 2.20
± 2.15
± 2.98
± 2.88
Foundry mean
Bottling plant mean
35.64 ± 2.08*
31.59 ± 1.93*
WB (°C)
WBGT
26.22 ± 1.37
25.77 ± 1.37
27.28 ± 0.58
25.95 ± 0.81
27.10 ± 0.90
32.00
32.50
31.89
29.39
31.54
± 3.58
± 3.94
± 0.72
± 1.02
± 1.39
26.42 ± 1.70*
25.22 ± 1.81*
32.47 ± 2.09*
25.74 ± 2.25*
RH (%)
Air speed (m/s)
Illumination (lx)
43.38 ± 4.29
42.92 ± 2.66
51.20 ± 10.03
58.00 ± 8.48
50.17 ± 9.51
0.80 ± 0.53
0.10 ± 0.16
0.73 ± 0.57
1.19 ± 0.83
0.67 ± 0.34
221.00 ± 211.00
58.46 ± 43.17
113.00 ± 41.34
93.20 ± 48.71
96.00 ± 45.79
48.03 ± 5.78*
63.45 ± 5.25*
0.62 ± 0.42*
0.91 ± 0.30*
114.90 ± 84.41
105.61 ± 33.50
DB, dry bulb temperature; WB, wet bulb temperature; WBGT, wet bulb globe temperature index; RH, relative humidity.
*P < 0.0001 (independent sample t-test).
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Occup. Med. Vol. 52, 2002
both eyes were seen in 22% of furnace workers and 29%
of fabrication workshop workers (Table 3). A significantly
(P < 0.01) higher percentage (15%) of foundry workers
had mild visual defects and 16% had moderate-to-severe
visual defects in both eyes, compared with 11 and 9%,
respectively, among the bottling plant workers.
Having acclimatized to the working conditions of the
foundry, the consumption of water among foundry
workers averaged 3–4 l during a working shift. No intake
of salt tablets was reported by any of the furnace or
bottling plant workers. Muscle cramps were reported by
~30% of the steel foundry workers, compared with 5% of
the bottling plant workers (Table 4). Among the foundry
workers, muscle cramps were reported by most of the
furnace (43%) and the continuous casting unit (31%)
workers. The majority (63%) of the workers at the iron
foundry consumed ≤3 l of water, with fewer (37%) workers consuming >3 l of water per day on a normal working
day (Table 4). Among the foundry workers, 35% of those
units at the foundry was >27.5°C [the threshold limit
value (TLV) for 75% work and 25% rest] [15]. The
mean WBGTin index for the foundry was significantly
(P < 0.0001) higher than the mean WBGTin index for the
bottling plant. Relative humidity ranged between 43 and
58%, and the air speed between 0.1 and 1.19 m/s, in the
different areas of the foundry. The mean relative humidity
and the air speed in the iron foundry were significantly
(P < 0.0001) lower than the corresponding mean values
at the bottling plant. Natural or electric illumination
was generally lower at the iron foundry compared with
the bottling plant. Furnace flames or molten metal contributed to a higher radiance at certain locations within
the foundry. The sound pressure levels were >85 dB (the
TLV for 8 h exposure) [15] in all the units of the foundry,
being highest (100 dB) in the casting area (Table 2). The
mean (92.7 ± 0.9) sound pressure level at the foundry
was significantly (P < 0.01) higher than that (77.6 ± 0.6)
at the bottling plant. Moderate-to-severe eye defects in
Table 2. Octave band frequency analyses and sound pressure levels at different worksites within the foundry and at the bottling plant
(geometric means ± SE of the means are reported for the octave bands and dB)
Work unit
Furnace unit
31.5 Hz (dB)
63 Hz (dB)
125 Hz (dB)
250 Hz (dB)
500 Hz (dB)
1000 Hz (dB)
2000 Hz (dB)
4000 Hz (dB)
8000 Hz (dB)
16 000 Hz (dB)
SPL (dB)
54.7
64.3
77.0
87.8
94.6
90.1
83.9
82.3
72.4
63.4
96.9
± 1.2
± 0.9
± 0.9
± 0.9
± 1.2
± 1.2
± 1.2
± 1.3
± 1.4
± 1.1
± 1.0
Continuous
casting unit
Rolling mill unit
57.3 ± 1.8
65.7 ± 1.8
76.9 ± 2.0
86.0 ± 2.2
94.6 ± 2.7
92.5 ± 2.5
87.6 ± 2.2
85.1 ± 2.2
77.3 ± 1.2
66.7 ± 1.7
100.4 ± 3.0
48.4 ± 1.9
58.8 ± 1.5
70.4 ± 1.4
81.4 ± 1.3
89.5 ± 1.9
85.7 ± 0.9
83.9 ± 0.8
82.3 ± 0.7
78.1 ± 1.8
64.4 ± 1.9
93.2 ± 0.9
Mechanical
workshop
Fabrication
workshop
Foundry mean
Bottling plant
mean
44.9
56.3
68.2
79.1
86.9
81.4
80.2
78.1
71.7
59.4
89.8
48.7 ± 0.9
58.7 ± 1.1
68.9 ± 1.1
76.1 ± 1.5
83.6 ± 1.4
80.9 ± 1.3
75.9 ± 1.1
72.2 ± 1.6
65.1 ± 1.6
53.0 ± 2.4
86.1 ± 1.3
50.9 ± 0.7
60.9 ± 0.6*
72.5 ± 0.7*
81.9 ± 0.8**
89.8 ± 0.9**
86.0 ± 0.8**
81.5 ± 0.7**
79.0 ± 0.9**
71.4 ± 0.9**
60.0 ± 0.9**
92.7 ± 0.9**
50.2 ± 0.2
58.9 ± 0.3
70.6 ± 0.2
71.3 ± 0.2
70.4 ± 0.4
67.9 ± 0.3
64.9 ± 0.3
61.1 ± 0.4
57.8 ± 0.4
53.3 ± 0.3
77.6 ± 0.6
± 0.2
± 1.1
± 0.7
± 1.3
± 0.9
± 0.8
± 1.9
± 2.4
± 2.7
± 3.3
± 1.9
ANOVA (analysis of variance, means procedure): *P < 0.001; **P < 0.0001.
Table 3. Snellen’s vision test for workers in the different units of the iron foundry and the bottling plant [values are n (%)]
Normal vision
Mild defect
Right eye Both eyes
Left eye
Moderate-to-severe
Job categories
Left eye
Right eye Both eyes
Left eye
Furnace operators (n = 27)
Casting workers (n = 10)
Rolling mill operators (n = 10)
Machinists (n = 9)
Fabricators (n = 14)
General workers (n = 11)
13 (48)
7 (70)
7 (70)
6 (67)
7 (50)
9 (82)
13 (48)
8 (80)
7 (70)
4 (44)
5 (36)
9 (82)
15 (56)
9 (90)
7 (70)
7 (78)
8 (57)
10 (91)
6 (22)
2 (20)
1 (10)
2 (22)
3 (21)
2 (18)
7 (26)
1 (10)
2 (20)
4 (44)
5 (36)
2 (18)
6 (22)
0
2 (20)
1 (11)
2 (14)
1 (9)
8 (30)
1 (10)
2 (20)
1 (11)
4 (29)
0
7 (26)
1 (10)
1 (10)
1 (11)
4 (29)
0
6 (22)
1 (10)
1 (10)
1 (11)
4 (29)
0
Foundry mean (n = 81)
Bottling plant mean (n = 113)
49 (61)*
81 (72)
46 (57)*
76 (67)
56 (69)*
91 (81)
16 (20)
25 (22)
21 (26)
26 (23)
12 (15)
12 (11)
16 (20)*
7 (6)
14 (17)*
11 (10)
13 (16)*
10 (9)
Normal vision, 6/6 on Snellen’s chart; mild defect, 6/9 on Snellen’s chart; moderate-to-severe defect, 6/>12 on Snellen’s chart.
*P < 0.01 (χ2 test).
Right eye Both eyes
J. Gomes et al.: Worker health in a rapidly developing country
125
Table 4. Water intake and frequency of muscle cramps among iron foundry workers at different work units [values are n (%)]
Water consumption
Muscle cramps
≤3 l
>3 l
≤3 l
>3 l
All workers
Furnace operators (n = 27)
Casting workers (n = 10)
Rolling mill operators (n = 10)
Machinists (n = 9)
Fabricators (n = 14)
General workers (n = 11)
17 (81)
5 (39)
5 (50)
6 (60)
10 (83)
8 (53)
4 (19)
8 (62)
5 (50)
4 (40)
2 (17)
7 (47)
8 (47)
1 (20)
1 (20)
2 (33)
3 (33)
3 (38)
1 (25)
3 (38)
1 (20)
–
–
1 (14)
9 (43)
4 (31)
2 (20)
2 (20)
3 (25)
4 (27)
Foundry mean (n = 81)
Bottling plant mean (n = 113)
51 (63)*
86 (76)*
30 (37)*
27 (24)*
18 (35)**
4 (5)**
Job categories
6 (20)**
2 (7)**
24 (30)**
6 (5)**
*P < 0.05 (χ2 test).
**P < 0.001 (χ2 test).
Table 5. Use of protective equipment by the workers at the iron foundry [values are n (%)]
Protective equipment
Overalls
Shoes
Helmet
Ear muffs/plugs
Goggles
Face mask
Gloves
F (n = 27)
CC (n = 10)
RM (n = 10)
MW (n = 9)
FW (n = 14)
Gen (n = 11)
All workers (n = 81)
0 (0)
21 (100)
19 (91)
0 (0)
21 (100)
19 (95)
20 (95)
0 (0)
12 (92)
10 (77)
0 (0)
11 (85)
9 (69)
12 (92)
0 (0)
10 (100)
5 (50)
0 (0)
8 (80)
4 (40)
8 (80)
0 (0)
9 (90)
6 (60)
0 (0)
8 (80)
6 (60)
9 (90)
0 (0)
12 (100)
7 (58)
0 (0)
12 (100)
7 (58)
11 (92)
0 (0)
13 (87)
6 (40)
0 (0)
10 (67)
7 (47)
13 (87)
0 (0)
77 (95)
53 (65)
0 (0)
70 (86)
52 (42)
73 (90)
F, furnace operators; CC, casting workers; RM, rolling mill operators; MW, machinists; FW, fabricators; Gen, general workers.
consuming ≤3 l of water reported experiencing muscle
cramps, compared with 5% of the bottling plant workers;
this difference was statistically significant (Table 4). The
figures of 20 and 7%, respectively, for cramp sufferers
among those consuming >3 l of water in the two occupational groups also differed highly significantly. Overall,
the frequencies of muscle cramps reported by the foundry
workers (30%) and the bottling plant workers (5%)
differed significantly (Table 4).
The use of overalls, shoes, helmet, earmuffs or plugs,
safety glasses, face mask and gloves as measures of personal protection was variable (Table 5). Overalls and
earmuffs or plugs were never used by any of the workers
at the iron foundry, though required. Shoes (95%), gloves
(90%) and safety glasses (86%) were used by most of
the workers, whereas helmets (65%) and face masks
(64%) were used less frequently (Table 5).
The estimated visual impairment using factorial
general linear model multivariate analysis for the exposed
workers was significantly higher compared with that for
the unexposed workers (Table 6). When visual disability
was estimated with age and BMI as covariates, furnace
and fabrication workers at the foundry were observed to
have a significantly higher visual disability compared with
the other workers (Table 6). Regression analyses identified jobs at the furnace and fabrication workshops as
significant predictors of visual disability in both eyes. The
mean estimated hearing disability (estimated by both the
AMA and the BAOL methods) for the foundry workers
(8.59 ± 1.08%) was significantly (P = 0.005) higher
compared with that for the workers at the bottling plant
(4.63 ± 0.91%) (Table 7). Rolling mill workers and those
from the fabrication and mechanical workshops were
observed to have a significantly higher estimated hearing
disability compared with other workers at the foundry.
Regression analyses also identified the jobs of fabricator
(P = 0.02) and rolling mill operator (P = 0.05) as significant predictors of hearing disability among foundry
workers, while working as a machinist (P = 0.07) was not.
Discussion and conclusions
Occupational exposures to heat and noise are unavoidable in the metal production and casting industries, but
these exposures could be minimized through efficient
control measures at the worksite and/or the proper use of
appropriate personal protective equipment. However, in
rapidly developing countries, personal protective equipment and exposure control measures are rarely used at
many worksites, and are given little importance and preference by many employers. This neglect may be due to
the fact that the workers in rapidly developing countries
126
Occup. Med. Vol. 52, 2002
Table 6. Estimated visual disability using factorial general linear model multivariate analysis for the exposed (different job categories) and
unexposed workers
Job categories
Furnace operators (n = 27)
Casting (n = 10)
Rolling mill operators (n = 10)
Machinists (n = 9)
Fabricators (n = 14)
General workers (n = 11)
Foundry mean (n = 81)
Bottling plant mean (n = 113)
a
Eye
Visual disability (mean ± SE)
95% CIa for mean
Estimated with covariates at
Left
Right
Both
Left
Right
Both
Left
Right
Both
Left
Right
Both
Left
Right
Both
Left
Right
Both
9.57 ± 0.94
9.29 ± 0.96
9.43 ± 0.91
7.85 ± 1.01
8.08 ± 1.03
7.96 ± 1.00
8.40 ± 1.19
8.70 ± 1.80
8.55 ± 1.43
8.10 ± 1.86
9.00 ± 1.92
8.55 ± 1.86
10.00 ± 1.32
12.10 ± 1.66
11.00 ± 1.46
6.60 ± 0.34
6.60 ± 0.33
6.60 ± 0.29
7.6, 11.6
7.3, 11.3
7.5, 11.3
5.7, 10.4
5.6, 10.1
5.7, 10.2
5.5, 11.3
5.6, 10.1
5.2, 11.9
3.7, 12.5
4.4, 13.5
4.2, 12.9
7.0, 12.9
8.3, 15.7
7.7, 14.3
5.9, 7.3
5.9, 7.3
5.9, 7.3
Age = 42.4; BMI = 25.1
Left
Right
Both
Left
Right
Both
8.52 ± 0.45*
8.85 ± 0.52
8.69 ± 0.47
7.35 ± 0.28
7.96 ± 0.38
7.66 ± 0.32
7.6,
7.8,
7.7,
6.8,
7.2,
7.0,
9.4
9.8
9.6
7.9
8.7
8.3
Age = 38.7; BMI = 26.4
Age = 40.2; BMI = 24.7
Age = 40.2; BMI = 24.9
Age = 43.1; BMI = 25.9
Age = 38.0; BMI = 25.8
Age = 40.9; BMI = 25.4
Age = 40.7; BMI = 25.6
CI, confidence interval.
*Estimated marginal means significantly different at P = 0.05 and 95% CI.
Table 7. Estimated hearing disability using factorial general linear model multivariate analysis for the exposed (different job categories) and
unexposed workers
Hearing disabilitya
(mean ± SE)
Furnace operators (n = 27)
Casting workers (n = 10)
Rolling mill operators (n = 10)
Machinists (n = 9)
Fabricators (n = 14)
General workers (n = 11)
Foundry mean (n = 81)
Bottling plant mean (n = 113)
Job categories
95% CI for mean
Hearing disabilityb
(mean ± SE)
95% CI for mean
Estimated with
covariates at
7.37 ± 1.88
8.38 ± 3.09
10.93 ± 3.07
10.65 ± 3.24
11.28 ± 2.61
4.56 ± 2.95
3.66
2.29
4.86
4.26
6.14
–1.20
11.07
14.47
16.99
17.04
16.42
10.37
9.84 ± 1.98
10.99 ± 3.26
14.34 ± 3.25
14.08 ± 3.15
13.83 ± 2.75
9.54 ± 3.11
5.93
4.57
7.94
7.33
8.39
3.40
8.59 ± 1.08
4.62 ± 0.91
6.46
2.83
10.71*
6.42
11.66 ± 1.13
7.13 ± 0.96
9.42
5.24
a
Hearing impairment (handicap) was calculated according to the method described in the AMA/AAO formula for the determination of hearing handicap [10].
b
Hearing impairment (handicap) was calculated according to the method described in the BAOL/BSA formula for the determination of hearing handicap [10].
*ANOVA, P < 0.0001.
are economic migrants from other developing countries,
who accept occupational exposures as part of the job. The
hot and humid climatic conditions further dissuade the
workers from using personal protective equipment, even
when provided. As in other studies, in the UAE, overalls,
earmuffs, face masks and helmets were either not used
or were used by only a few workers [16]. Unlike their
counterparts in developed countries, these industries in
these rapidly developing countries do not implement any
control measures to minimize exposures at workplaces.
Non-use of personal protection may have contributed to
the increased exposure to non-ionizing radiation and
noise, and thereby increased visual and hearing disability
among those most exposed.
The results of the thermal survey (WBGTin index)
indicated a high prevalence of thermal stress throughout
J. Gomes et al.: Worker health in a rapidly developing country
the foundry. The low ambient air speed values at the
foundry indicated the absence of any artificial ventilation.
Muscle cramps usually occur among those who work in
hot environments, and are even higher among those who
drink large amounts of water without salt tablets [17]. In
this study, we found that muscle cramps were experienced
by a higher percentage of foundry workers, who had a
higher heat load than the unexposed group; by contrast,
the percentage of those consuming >3 l of water who were
observed to experience muscle cramps was less than that
of those consuming ≤3 l of water. In our study, the
foundry workers experienced indoor working conditions
with much lower heat than the workers in the study
by Awahl et al. [17], who worked outdoors with a higher
heat load and consumed more water; this dissimilarity
could explain the differences in muscle cramps and water
consumption in these two sets of workers. Cool water
fountains and rest areas were not available to the workers
on-site.
The non-use of goggles or other eye protection devices
may have affected the vision of the workers. Only 69% of
the workers at the foundry were observed to have normal
vision in both eyes, compared with 81% of the workers
at the bottling plant, although the mean ages for the
two groups were similar. The 31% of workers at the
foundry with eye defects consisted of 15% with a mild
defect and 16% with a moderate-to-severe defect.
Exposure to IR radiation from the furnace and the molten
metal is capable of causing injuries to the cornea, iris,
retina and lens of the eye [18]. Ocular damage can result
from incident energy on the cornea at a density of
4–8 Ws/cm2, which is typical of the energy emitted by
furnace flames and molten metal [18, 19]. Unprotected
exposure to radiation from the furnace and molten metal
could be well over the maximum permissible dose
(0.4–0.8 Ws/cm2) from incandescent sources [18]. The
estimated visual disability was higher for workers from the
foundry compared with the bottling plant workers. The
workers at the fabrication workshop and furnace area
were estimated to have an even greater visual disability. A
dose–response effect seemed to be apparent among workers at the foundry, with higher percentages of workers
from fabrication workshops and furnace areas being diagnosed with moderate-to-severe defect. Although goggles
were provided, fabrication workshop workers seldom
used them during welding, and furnace workers were
observed using goggles only infrequently during potting,
testing and casting the molten metal. Thermal screens
were not seen at many of the likely locations in the
foundry, and thermal overalls were not made available to
the workers on-site.
Although the overall mean noise level at the foundry
was >85 dB in almost all working areas, none of the
workers used earmuffs or plugs, or even a helmet with ear
protection. The average length of the workday during the
127
general work shift was 10–12 h, depending on the production targets. In addition, some of the workers worked
overtime. The workers therefore exceeded the TLV [15],
and this may have reflected on the hearing disability observed among these workers. The higher estimated mean
hearing disability value for the workers at the foundry
(8.69 ± 1.08%) compared with that for the workers at the
bottling plant (4.56 ± 0.82%) indicated greater exposure
to occupational noise among the former group. Noise
exposure at the furnace and the casting areas was intermittent, as higher levels of noise were emitted only during
the charging, potting and casting processes. In contrast,
noise emissions from the rolling mill and the mechanical
and fabrication workshops were continuous. The noise
exposure of these workers may have been greater because
the sound pressure levels for these areas in the foundry for
frequencies between 250 and 8000 Hz were almost all
>70 dB, and these workers were also exposed continuously during each shift. The hearing disability observed
among workers from the rolling mill and from the fabrication and mechanical workshops was greater than that
among the workers from other areas, these workers being
also exposed to higher noise levels. The greater hearing
disability among workers exposed to higher ambient noise
levels indicates a dose–response relationship between
exposure to noise and hearing disability. Similar hearing
disability has been reported in other industries in other
rapidly developing countries [20].
Noise came from various sources at different locations
throughout the foundry, and noise levels exceeded the
TLV for noise exposure at all the worksites there. The
foundry did not implement noise control measures, nor
did it provide noise-free rest areas within the foundry.
Even if the workers were provided with some protective
equipment, the high ambient heat would have dissuaded
them from using it.
In conclusion, the workers at the foundry were exposed
to higher heat, noise, and UV and IR radiation than were
experienced by the comparison workers at the bottling
plant. The foundry workers did not use the much-needed
personal protection. Vision and hearing problems were
more frequent among these foundry workers than those
at the bottling plant, where heat, UV and IR radiation,
and noise exposures were absent. Muscle cramps were
also observed in a higher percentage of the workers at the
foundry, who were exposed to thermal stress during the
workshift. Workers at the foundry also worked long hours
(the average shift length being 12 h).
While we recommend that these workers use proper
personal protective equipment whilst working on the
shop floor, we also suggest that proper equipment appropriate for use in tropical countries be made available
to these workers. To protect the workers from excessive
exposures to heat, UV and IR radiation, and noise,
governmental monitoring agencies need to require that
128
Occup. Med. Vol. 52, 2002
industries implement occupational hygiene and provide
personal protective equipment to the exposed workers.
Hearing conservation programmes should be introduced,
efforts should be made to control noise levels and ear
plugs/muffs should be provided to all the exposed
workers. Since the majority of the workers are unskilled,
governmental agencies should focus on education and
training in safe and appropriate working conditions.
Programmes aimed at rewarding those workers who use
personal protective equipment, when available, should
be introduced. Appropriate control measures, such as
insulated heat screens, need to be installed to minimize
exposure to heat. Noise-insulated and cooled rest areas
should also be provided to the workers for use during
breaks while on duty. The average length of a normal day
workshift should be limited to 8 h and salt tablets should
be provided to all the workers in the foundry. Workers
exposed to heat, UV and IR radiation, and noise should
be regularly monitored for adverse health effects.
Acknowledgements
The authors wish to thank the management and the workers
at the iron foundry where the study was carried out and the
Municipality of Dubai for their cooperation and assistance
in facilitating this study. The authors also acknowledge the
technical assistance of Mr Jamal Cherkonath in collecting the
data. This study was supported in part by the Department of
Community Medicine, Faculty of Medicine, UAE University.
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