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Introduction: Increasing heat waves-particularly in urban areas where construction is most prevalent, highlight a need for heat exposure assessment of construction workers. This study aims to characterize the effects of heat on construction workers from a site in Gandhinagar. Materials and Methods: This study involved a mixed methods approach consisting of a cross sectional survey with anthropometric measurements (n = 219) and four focus groups with construction workers, as well as environmental measurements of heat stress exposure at a construction site. Survey data was collected in two seasons i.e., summer and winter months, and heat illness and symptoms were compared between the two time periods. Thematic coding of focus group data was used to identify vulnerability factors and coping mechanisms of the workers. Heat stress, recorded using a wet bulb globe temperature monitor, was compared to international safety standards. Results: The survey findings suggest that heat-related symptoms increased in summer; 59% of all reports in summer were positive for symptoms (from Mild to Severe) as compared to 41% in winter. Focus groups revealed four dominant themes: (1) Non-occupational stressors compound work stressors; (2) workers were particularly attuned to the impact of heat on their health; (3) workers were aware of heat-related preventive measures; and (4) few resources were currently available to protect workers from heat stress. Working conditions often exceed international heat stress safety thresholds. Female workers and new employees might be at increased risk of illness or injury. Conclusion: This study suggests significant health impacts on construction workers from heat stress exposure in the workplace, showed that heat stress levels were higher than those prescribed by international standards and highlights the need for revision of work practices, increased protective measures, and possible development of indigenous work safety standards for heat exposure.
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© 2015 Indian Journal of Occupational and Environmental Medicine | Published by Wolters Kluwer - Medknow 151
Perceived heat stress and health effects on
construction workers
Priya Dutta,
Ajit Rajiva,
Dileep Andhare,
Gulrez Shah Azhar,
Abhiyant Tiwari,
Perry Shefeld1,
Ahmedabad Heat and
Climate Study Group
Environment and
Occupational health
Department, Indian
Institute of Public
Health Gandhinagar,
Ahmedabad, Gujarat,
India, 1Department
of Pediatrics and
Preventive Medicine,
Icahn School of
Medicine at Mount
Sinai, New York, USA
For correspondence:
Dr. Priya Dutta,
Indian Institute
of Public Health
Gandhinagar, Inside
Sardar Patel Institute
Campus, Thaltej,
Ahmedabad - 380 054,
Gujarat, India.
E-mail: priyadutta@
iiphg.org
INTRODUCTION
In India, the construction industry
engages approximately 4 million
workers and contributed 8% of Indian
GDP during the financial year of
2012‑13.The sector showed a growth
rate of 5.9% during 2012‑13 against
growth of 5.6% in the previous year.[1]
As per the latest estimates, there are
around 500,000 construction workers
in Gujarat; 50,000 of which are based
in Ahmedabad city.[2]
Construction workers are a group
that are particularly vulnerable
to health risks because they have
few legal protections, a poor safety
net, increased exposures to some
environmental factors, and are
economically disadvantaged. The work
involved in the construction industry
is mostly temporary; most workers
receive daily wages in cash and
have neither contractual obligations
nor benefits. Construction work
involves manual lifting and carrying
and may lead to musculoskeletal
injuries. Working at heights, with
heavy overhead loads, operating
heavy machinery and power tools or
working under temperature extremes
contribute to risk of accidents and
injuries. India has the world’s highest
accident rate among construction
workers, i.e., 165 out of every 1000
workers.[3,4] Merlino
et al
.[5] concluded
Abstract
Introduction: Increasing heat waves‑particularly in urban
areas where construction is most prevalent, highlight a
need for heat exposure assessment of construction
workers. This study aims to characterize the effects of
heat on construction workers from a site in Gandhinagar.
Materials and Methods: This study involved a mixed
methods approach consisting of a cross sectional survey
with anthropometric measurements (n = 219) and four
focus groups with construction workers, as well as
environmental measurements of heat stress exposure
at a construction site. Survey data was collected in two
seasons i.e., summer and winter months, and heat
illness and symptoms were compared between the
two time periods. Thematic coding of focus group data
was used to identify vulnerability factors and coping
mechanisms of the workers. Heat stress, recorded using
a wet bulb globe temperature monitor, was compared
to international safety standards. Results: The survey
ndings suggest that heat‑related symptoms increased
in summer; 59% of all reports in summer were positive
for symptoms (from Mild to Severe) as compared to
41% in winter. Focus groups revealed four dominant
themes: (1) Non‑occupational stressors compound work
stressors; (2) workers were particularly attuned to the
impact of heat on their health; (3) workers were aware of
heat‑related preventive measures; and (4) few resources
were currently available to protect workers from heat
stress. Working conditions often exceed international
heat stress safety thresholds. Female workers and
new employees might be at increased risk of illness
or injury. Conclusion: This study suggests signicant
health impacts on construction workers from heat stress
exposure in the workplace, showed that heat stress
levels were higher than those prescribed by international
standards and highlights the need for revision of work
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DOI:
10.4103/0019-5278.174002
Quick Response Code:
Cite this article as: Dutta P, Rajiva A, Andhare D, Azhar GS, Tiwari A,
Shefeld P, Ahmedabad Heat and Climate Study Group. Perceived
heat stress and health effects on construction workers. Indian J Occup
Environ Med 2015;19:151‑8.
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practices, increased protective
measures, and possible
development of indigenous
work safety standards for heat
exposure.
Key words: Construction worker,
heat stress, wet bulb globe
temperature
Original Article
Dutta, et al.: Perceived heat stress
152 Indian Journal of Occupational and Environmental Medicine - December 2015 - Volume 19 - Issue 3
that musculoskeletal symptoms are a significant problem
among young construction workers even at the beginning
of their careers. Furthermore, the majority of workers are
migrants from other state, and as a result families are typically
highly mobile without developed local support networks. The
effects extend beyond the workers themselves as both parents
may be engaged in construction, and older girls are often
forced to drop out of school to care for their younger siblings.
Certain subgroups of construction workers, such as females,
are perhaps at even greater risk of injury or illness. In the
construction industry, the number of females are comparatively
few relative to males but their number is increasing in urban
projects.[6] Most of the women construction workers are
unskilled and illiterate, and thus paid lower wages. Their
work mainly involves helping male workers, carrying head
loads like cement bags, bricks and other materials. Studies
have revealed job stress, sexual harassment and gender based
discrimination among female construction workers which
affects their psychological and physical health.[4,7]
In addition to occupational health hazards and socioeconomic
stresses, hot environments also pose health risks. Urban heat
island effect and changing climate contribute to increasing
heat exposure for city‑dwellers and outdoor workers in
particular.[8,9] The Government of India and state governments
have framed acts and regulations for improving working
conditions for construction workers.[10] However, due to the
rapid growth of infrastructure, neglect of safety and health
aspects of construction work continues.[11]
In India, there is little research documenting the aspects
of thermal load and health outcomes among construction
workers. A study in Ahmedabad on other occupations
showed that workers’ perceptions of heat load and reports
of heat related disorders were significant and correlate with
the physical findings at the workplace.[12] The same study
concluded that occupational groups exposed to direct solar
radiation have increased risk of heat injury. In addition,
extreme temperatures in Ahmedabad have been documented
to have health effects on the general population. Slum dwellers
and infant health and overall population mortality have all been
shown to be impacted by heat in Ahmedabad – particularly
in relation to the 2010 heat wave in Ahmedabad.[13‑15] The
aim of the present study is to characterise the effects of
heat on construction workers from a site in Gandhinagar,
Gujarat – adjacent the city of Ahmedabad.
MATERIALS AND METHODS
This study consisted of a cross sectional survey, focus groups
discussions (FGDs), and environmental measurements of heat
stress exposure in workplace settings. The study population
included construction workers in the city of Gandhinagar,
Gujarat, India located in the western part of India which is
an extremely hot region. Data was collected in two seasons
i.e., summer and winter months. Summer surveys were
carried out in May of 2013 and 2014 (43 + 66) and winter
surveys in January of 2014 (110) for a total of 219 participants.
FGDs occurred in May of 2013 and 2014. The survey and FGDs
were conducted between 9AM and 6PM (working hours).
Unskilled workers, both males and females, over 18 years of
age who consented to participate in the study were included.
Management staff and those engaged in office work were
excluded from the study since they spent most of their time
indoors or spent minimal time performing strenuous activity.
Ethical clearance for this study was obtained from the
Institutional Ethics Committee (IEC) of the Indian Institute
of Public Health Gandhinagar.
Survey questionnaire
The survey consisted of an interviewer administered
structured questionnaire, adapted from the HOTHAPS
study[16] and piloted locally before being administered. All
subjects were engaged in construction work at the site. All
subjects were asked questions covering age, body habitus,
socio‑demographic information, nature of work performed,
lifestyle choices, history of illness, individual preventive
measures and heat related symptoms experienced during
work. The participants were also questioned whether they
had any of the specific symptoms from a predetermined list,
classifying the severity from 1 (None) to 5 (Severe). All data was
analyzed using SPSS version 20.0 and Microsoft Excel 2013.
While the location of the study remained the same in both
summer and winter months, repeating the survey with the
same workers was not feasible due to the high turnover rate
of labourers in the construction industry.
Focus group discussions
Data was collected through four FGDs with 11 participants
each. The purpose of this qualitative component of the study
was to understand the perception of construction workers
regarding their work in a hot environment and to understand
their knowledge of available health protective resources. The
FGDs were carried out at the workplace during the afternoon
hottest portion of the day to best capture participants’
perception of heat stress. All FGDs were conducted in the local
language (Gujarati) and Hindi with the help of a facilitator and
a field note taker. FGDs were thematically coded into concepts
and categories using grounded theory approach.
Temperature measurements
The workplace heat exposure parameters include
Ambient Dry Bulb Temperature, Wet Bulb Temperature,
and Globe Temperature measured by a Wet Bulb Globe
Temperature (WBGT) Monitor (QUESTemp 34, Heat
Stress Monitor, United States) and temperature/humidity
Dutta, et al.: Perceived heat stress
153
Indian Journal of Occupational and Environmental Medicine - December 2015 - Volume 19 - Issue 3
data‑loggers (Lascar EL‑USB‑2‑LCD, United States) collected
from 10AM to 4PM. Environmental thermal characteristics
were expressed in terms of the WBGT index.[17] The
measurements were automatically recorded at one minute
intervals and the instruments were kept in an open space.
RESULTS
Survey questionnaire
The self‑reported characteristics of male and female
construction workers are in Table 1. On average, the
workers have similar stature and most labourers were
between 18 and 35 years. The average job experience of
male and female workers during summer was 36.0 ± 70.5
and 42.0 ± 27.3 months and in winter was 36.0 ± 72.4 and
13.5 ± 15.6 months respectively. Most of the labourers work
for 8‑10 hours/day. The educational status of workers was
found to be low i.e. only 10.75% of the workers had reached
12th standard and above. Nearly 58% of the workers didn’t
have any cooling measures like fans/air coolers available at
home even during summer. Of the 84% of the workers who
were migrants, 41% reported going back to their village to
assist with agricultural tasks during harvest and cultivation
seasons. Secondary occupations like farming, grocery shop
keeping, and electronic repair were reported by 55.0% of
summer workers and 41.8% winter workers. Workers were
provided personal protective equipment like hats and shoes
though none of the workers wore masks or gloves at work.
Higher percentage of female workers were illiterate (67 vs 24%)
compared to males, and fewer females reported access to
household cooling measures such as fans (12 vs 41%).
Table 2 describes the differences in task assigned to labourers
over the total sampling time. Labourers (unspecified), masons,
carpenters, shutter joiners (form workers), plasterers, iron
cutters, cement mixer, pipeline setters, iron benders were
considered heavy work under ACGIH classification i.e., between
200‑260 W/m2. Moderate work, consisting of work between
130‑200 W/m2, on site was performed by electricians, fitters,
insulation layers, painters and work managers. Only the cook
fell into the light work category of 65‑130 W/m.[2,18] In this study
that occurred at a single construction site, finishing jobs like
electrical fitting and iron welding are concentrated towards the
end of the construction process and study period (summer 2014).
Overall reports of all heat related symptoms increased
among workers surveyed in summer as hypothesized; 59% of
labourers reported heat‑related symptoms (Mild to Severe) as
compared to 41% in winter with OR = 1.43 [1.54‑1.32]. These
results were calculated using the Wald method with continuity
correction factor and were highly significant due to the large
number of people sampled (
P
< 0.0000).
Table 3 shows frequency of worker‑reported symptoms
and injuries. Over 40% of workers reported at least
one symptom in either season. Heavy sweating (67.9%),
intense thirst (72.5%) and dry mouth (45.9%), the latter
two being consistent with dehydration, and neurological
symptoms like headache (34.9%), loss of coordination (15.6%),
dizziness (31.1%), blurred vision (25.7%) and fainting (18.3%)
were more prevalent during the summer months compared to
the winter. Nearly one fourth of the workers both in summer
and winter reported spasms, 16.5% in summer and 10.9% in
winter felt abdominal cramps and, 45% in summer and 37.3%
in summer reported fatigue.
Overall, 12.8% of workers reported on‑site injuries during
their work. These injuries ranked from minor cuts to a
fracture, with a slightly ‑ though not significantly ‑ higher
prevalence in winter (14.7 vs 9.2%) compared to summer. All
injuries reported in summer were among workers with less
than 36 months of experience. More experienced workers did
not report injuries. The study also revealed that none of the
workers were offered paid sick leave. Most of the workers
Table 1: Labourer profile
Category Sub-category Total (N=219) Summer month (N=109) Winter month (N=110)
Male
(N=186)
Female
(N=33)
Male
(N=93)
Female
(N=16)
Male
(N=93)
Female
(N=17)
Population age Mean age (years) 24.0±8.1 20.5±5.8 23.0±8.2 20.5±5.4 25.0±8.1 20.5±6.4
Anthropometric measurements Mean height (m) 1.6±0.1 1.5±0.1 1.6±0.1 1.5±0.1 1.6±0.1 1.5±0.1
Mean weight (kg) 52.0±7.4 43.0±4.8 50.0±8.3 41.5±3.7 53.0±6.4 45.0±5.4
Mean BMI (kg/m2) 19.7±2.5 19.0±2.3 19.3±2.6 18.5±2.0 20.2±2.3 20.5±2.2
Occupation related Mean job experience (months) 36.0±71.3 36.0±26.3 36.0±70.5 42.0±27.3 36.0±72.4 13.5±15.6
Migrants (%) 84.4 81.8 77.4 68.8 91.4 94.1
Multiple occupations (%) 45.2 66.7 53.8 62.5 36.6 70.6
Literacy rate (%) Illiterate 23.7 66.7 16.1 75.0 29.0 58.8
Some school 66.7 33.3 69.9 25.0 63.4 41.2
12th pass and above 10.8 0.0 14.0 0.0 7.5 0.0
Lifestyle/habits (%) Alcohol 0.5 0.0 1.1 0.0 3.2 0.0
Chewing tobacco 48.9 3.0 55.9 0.0 44.1 5.9
Smoking 6.5 0.0 6.5 0.0 10.8 0.0
Household cooling available (%) Fan 40.9 12.1 43.0 25.0 34.4 0.0
Air cooler 1.6 0.0 2.2 0.0 1.1 0.00
Dutta, et al.: Perceived heat stress
154 Indian Journal of Occupational and Environmental Medicine - December 2015 - Volume 19 - Issue 3
reported that they did not seek treatment for minor injuries
or health problems.
As stated, in addition to evaluating the prevalence of
heat‑related symptoms, this study elicited reports of severity.
Figure 1 shows the difference in average reports n summer
and winter for the workers graded by severity which indicate
a clear shift in severity and frequency towards more severe
and more frequent outcomes. The majority of symptoms
are greater in summer.
Focus group discussions
The FGDs explored socioeconomic status, health protective
resources, workers’ perception of exposure to hot
environments, heat related disorders, and health measures
adopted to cope with hot environment. FGDs occurred while
workers took their one hour rest at lunch time (1PM to 2PM),
generally in shade or under a tree as the rest area provided to
the workers was insufficient and without any cooling facilities.
The atmosphere during FGDs was cordial and workers seemed
willing to discuss this topic.
Four key categories were identified through the thematic
coding: (1) Non‑occupational stressors compound work
stressors; (2) Impact of heat on health; (3) Awareness of
heat‑related preventive measures; (4) Resources available.
Non‑occupational stressors compound work
stressors
Most workers and families are from rural areas of distant
states like Bihar, Jharkhand, West Bengal, and Madhya
Pradesh. Frequently cited drivers for migration included
unemployment, less fertile land, family liabilities, and better
life for their children. Both newly arrived workers and other
workers noted the lack of availability of basic amenities,
including housing, access to drinking water, affordable
food, and proper sanitation. Workers described their job as
strenuous and physically demanding. They spent most of the
time outdoors exposed to direct solar radiation. The workers
did not report injuries to supervisors as they perceived
these injuries as part of their job or they feared negative
consequences from the employer. Around a quarter of workers
interviewed felt musculoskeletal pain. This finding is separate
from reported symptoms of heat stress discussed earlier.
Table 2: A breakup of individual duties for each sampling time.
All numbers are percentages within each season and are
arranged in descending order of average assignment
Summer
2013
Winter
2014
Summer
2014
Average
Labour (H) 37 34 38 36
Mason (H) 10 20 5 11
Management (M) 16 5 11 9
Carpentry (H) 16 8 3 8
Shutter joiners (H) 0 15 2 8
Plastering (H) 9 0 14 6
Electrician (M) 2 3 12 5
Other 0 1 5 2
Fitter (M) 0 3 2 2
Iron cutting (H) 5 2 0 2
Cement mixing (H) 5 1 0 1
Centering (H) 0 1 3 1
Iron welding (M) 0 1 3 1
Insulation (M) 0 3 0 1
Painting (M) 0 1 3 1
Pipeline (H) 0 2 2 1
Bending Iron (H) 0 1 0 0
Cook (L) 0 1 0 0
H: Heavy work, M: Moderate work, L: Light work
Table 3: Worker reports of heat illnesses
Summer month
(N=109)
Winter month
(N=110)
n%n%
Neurological symptoms
Headache 38 34.9 32 29.4
Loss of co-ordination 17 15.6 3 2.8
Dizziness 34 31.2 22 20.2
Tingling in hands/feet 21 19.3 25 22.9
Blurred vision 28 25.7 20 18.4
Fainting 20 18.4 16 14.7
Electrolyte imbalances
Abdominal cramps 18 16.5 12 11.0
Spasms 28 25.7 27 24.8
Systemic symptoms
Fatigue 49 45.0 41 37.6
Nausea 22 20.2 21 19.3
Loss of appetite 34 31.2 27 24.8
Early heat stress symptoms
Heavy sweating 74 67.9 30 27.5
Intense thirst 79 72.5 44 40.8
Anxiety 13 11.9 8 7.3
Dark coloured urine output 37 33.9 18 16.5
Rashes 15 13.8 5 4.6
Itching skin 17 15.6 10 9.2
Dry mouth 50 45.9 12 11.0
Elevated temperature 24 22.0 6 5.5
Hot red or flushed dry skin 3 2.8 1 0.9
Occupational injuries
Total reported occupational injuries 10 9.2 16 14.7
Falls/fractures 2 1.8 2 1.8
Cuts/scrapes/minor injuries 5 4.6 8 7.3
Non-descript injuries 3 2.8 0 0.0
Figure 1: An illustration of the average change in reporting, for various
categories of severity, from winter to summer for multiple heat related
symptoms. They have been further categorized by their statistical
signicance. Odds ratios between summer and winter are highlighted
in the brackets. All results marked signicant have P < 0.05
Dutta, et al.: Perceived heat stress
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Indian Journal of Occupational and Environmental Medicine - December 2015 - Volume 19 - Issue 3
“We work because it is the only available source of
income.” ‑ Participant
Impact of heat on health
Some workers perceived a trend of increasing numbers of
hot days in summer over the past few years and an increased
feeling of tiredness and exhaustion.
“During summer month lunch break should be of
3 hour” ‑ Participant
“This summer many workers suffer from fainting, dizziness
and nausea during work” ‑ Participant
Workers also affirmed that leave from work meant lost wages
for ill workers, posing additional risk to their families. The
health effects mentioned during FGDs included headache,
heavy sweating, intense thirst, dizziness, weakness/fatigue,
impaired judgment, nausea, loss of appetite, dark urine,
blurred vision, spasm in leg/arm, fainting/unconsciousness,
pink/red bumps and itching/prickly sensation. Some workers
complained of lightheaded‑ness in the evening and irritation
and exhaustion. Workers reported the impacts of sun exposure
on their eyes. They said that working in the sun caused eye
strain that sometimes resulted in irritation.
“My eyes become blurred and painful”‑ Participant
Awareness of heat related preventive measures
Workers reported adopting various strategies to prevent
illness from heat such as drinking a large amount of water,
sprinkling their face with water, resting in the shade. When
asked what they did when they felt it too hot to work, most
of the workers mentioned water as an important factor
for coping in extremely hot climate. Some workers had
noted a lack of safe drinking water available on site and
stated that they supplied their own water from home to
drink at work.
“Drinking water provided to us is not fit for
drinking” ‑ Participant
Resources available
The only personal protective equipment available to the
workers were hard hats and safety shoes. These contributed
to the workers feeling hot and sweaty. None of the workers
were provided gloves and sun‑glasses. Workers felt that
the use of sun‑glasses would protect their eyesight. Female
workers complained that the toilet facility provided to them
is unsanitary and unhygienic.
“Restroom has no fan and [is] insufficient for all
workers” ‑ Participant
Environmental measurements
The thermal environmental measurements were recorded
continuously over the hottest parts of the work day. The results
are tabulated below in Table 4 and illustrated in Figure 2. In
a comparison of summer and winter measurements, globe
temperature shows the highest mean difference throughout
the day; nearly constantly displaced with summer values
about 1.5 times higher on average than winter values. All
mean values of parameters are higher in summer while
standard deviations increased during winter. Skews also
tend to be more positive during summer while negative
skews (between 0 and ‑1) are seen during winter. Winter
data also shows a clear pattern of increase and decrease
during the measurement period which is absent in summer.
Our study observed that during summer the mean WBGT
were above maximum ACGIH recommendation for WBGT i.e
32.2°C (25%:75% work rest ratio/hour) for light work.[18] Even
in winter the mean WBGT was 27.41°C i.e., 50%:50% Work rest
ratio/hour according to established ACGIH threshold limit. All
workers were observed to do continuous work during each
season that fits the ACGIH classification of 75‑100% work
rest allocation.[18] The corresponding threshold limit for this
regime is 25.0°C which is exceeded by 7°C in summer and
by 2°C in winter.
DISCUSSION
The objective of this study was to explore the effects of heat
stress on construction workers in order to begin to identify
possible intervention points at both worker and policy levels.
The general findings of the survey, FGD and environmental
measurements were:
• Workers reported a high burden of symptoms possibly
related to heat that increased in both frequency and
severity during hotter work months. Further supporting the
concept of heat as the driver, specific symptoms associated
with electrolyte imbalance and improper hydration also
increased during summer
• Workersaredissatisfiedwiththelevelofcooling,drinking
water, and sanitation facilities available but are compelled
Table 4: Summary statistics of thermal environmental variables.
Maximum ACGIH recommendation for WBGT is 32.2°C, based on
a 25%: 75% work rest ration per hour for light work
Parameter Mean SD Skew
Summer
Globe temp 50.87 3.03 −0.64
Dry bulb temperature 37.72 2.81 0.37
Wet bulb temperature 25.91 0.81 0.16
WBGT 32.08 1.10 −0.30
Winter
Globe temp 32.92 3.47 −0.70
Dry bulb temperature 28.33 4.27 −0.70
Wet bulb temperature 25.84 3.33 −0.79
WBGT 27.41 3.47 0.70
SD: Standard deviation, WBGT: Wet bulb globe temperature
Dutta, et al.: Perceived heat stress
156 Indian Journal of Occupational and Environmental Medicine - December 2015 - Volume 19 - Issue 3
to tolerate working conditions and work for the given wages
given their economic vulnerability
• Thethermalenvironmentrecordedinsummerisbeyond
international guidelines for the level of work conducted
by each worker. Winter temperatures, though lower are
still above those recommended for labourers engaged in
continuous work with little rest
• Specific subgroups of workers such as migratory
workers (due to lack of acclimatization and poor support
network) and women (due to discrimination in the work
place and inadequate sanitation facilities for women)
have additional vulnerability factors that could put them
at increased risk of heat‑related illness.
The mean recorded WBGT in summer was 32.4 ± 1.1°C which
is 3.4°C higher than suggested permissible exposure limits
for acclimatized men in the tropics.[18,19] Wider temperature
variation during the workday is seen in winter whereas
summer shows a mostly stable ascending trend. While mean
wet bulb temperature remains constant in both seasons,
the variance and skew alter significantly. This indicates that
winter days offer a greater respite from humid heat in the
early hours when compared to the summer even though at
peak temperatures, they may even exceed those of summer.
However which proportion of the differences are attributable
to which temperature variable will require a more detailed
study. In summer, all workers work at conditions above
the recommended values adjusted for work intensity and
work/rest ratios. Even in winter, those performing heavy labour
are working at conditions above those prescribed by the ACGIH.
Broadly, from environmental heat metrics and labourer
reported symptoms, the study shows a heat‑stress related
health effects throughout the year and increased in the
summer. We surmise that the high exposure coupled with
strenuous physical load are the major contributing factors.
The majority of symptoms with significantly higher odds in
the summer were all classic symptoms of severe dehydration
and heat exhaustion bordering on heat stroke. Excessive
sweating, which showed the most significant increase, would
have compounded the effects of those disorders. Also of note is
that this study may be conservative in its findings as responses
related to heat disorders among construction workers may
be higher than those figures observed in the study due to
a healthy worker bias (i.e., those most affected by the heat
were absent or had stopped doing this type of work). Another
possible explanation may be attributed to the fear of being
reprimanded by the management for discussing issues that
may portray them negatively. Our findings showed that break
rooms provided to the workers were inadequate for their needs
and ineffective in reducing the thermal load of participants. The
focus group discussion findings also supported that heat illness
and discomfort were attributed to their level of heat exposure.
The best way to prevent heat stress, ideally, is to avoid heavy
manual work in a hot environment. Other methods may include
Figure 2: Average dry bulb, wet bulb, globe temperature and WBGT readings at all recorded times for both summer (red) and winter (blue)
Dutta, et al.: Perceived heat stress
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Indian Journal of Occupational and Environmental Medicine - December 2015 - Volume 19 - Issue 3
the use of mechanical means or the work to be completed
it in cooler parts of the day. Inaba and Mirbod[20] observed
that an onsite air conditioned break room and ice should
be available during the working hours in the summer to aid
recovery in exposed workers. To address these concerns,
supervisors/contractors should suggest job rotation, the
provision of cold water onsite, an earlier start to the day or
extended work in the evening with frequent breaks and training
on heat preventive measures to the workers. Engineering
controls like erected shelters, fans, water fountains and proper
restrooms can reduce heat stress among workers. Pascoe
et al
.[21] recommended that overall, to keep cool in the heat a
worker should wear: (1) Thin clothing that allows evaporation;
(2) clothing that blocks radiant heat; (3) loose clothing that
allows air to circulate next to the skin; (4) materials that keep
excess moisture from lying on the skin surface.
The study recorded an array of heat illness indicators among
construction workers. There is lack of Indian heat exposure
guidelines for determining ceiling limits of environmental
exposure for tropical heat exposure of the population. Our
study supports the establishment of separate tropical or
India specific heat exposure guidelines and interventions
that could simultaneously be worker protective but realistic
in this climate. WBGT may not be the best indicator for
Indian conditions as all measurements in summer, and
winter, were well above the recommended exposure limits
as defined by the ACGIH guidelines. However, work was
possible on these days and most workers are acclimatized
to these otherwise extreme conditions. WBGT is highly
dependent on wet bulb temperature as a component of
its calculation. Mean wet bulb temperature does not vary
between summer and winter and the majority of change
between the heat stress indices (i.e., globe temperature
and dry bulb temperature) only accounts for 30% of the total
calculation of WBGT.
Limitations and strengths
While the location of this cross sectional study was the same in
summer and winter months, the specific workers and worker
tasks differed between the survey times. However, regardless
of possible differences between the summer and winter survey
participants and their activities, heat‑related symptoms and
environmental measurements of heat stress were high in both
seasons supporting our overall finding that heat stress is an
important risk factor for worker health.
A key strength of this study is that the research team is
part of a larger on‑going effort of the Ahmedabad Heat and
Climate Study group with local public health, municipal, and
international academic partners. This group is supporting
efforts by the city to create a larger heat action plan[22] and thus
findings from studies like these have an immediate conduit
for translation into public health protective interventions.
Implications and next steps
A key objective of this study was to identify possible
intervention points at both worker and policy levels. As
workers who participated in our study already seem attuned
to heat risks, emphasis needs to be on creating a culture of
health at the work sites through empowering the workers,
incentivizing the employers, and enforcing existing safety
regulations. Interventions as seemingly unrelated as
supporting migratory workers’ rights or providing appropriate
toileting facilities for women might indirectly help lower
heat‑related illness. Heat stress could potentially be impeding
productivity and contributing to worksite accidents,[23] and
given that India already has the highest accident rate for
construction workers, both private and public sectors have a
vested interest in intervening around the issue of heat stress
and construction sites.
Further studies on construction work may be advantageous
in estimating the exact nature of thermal load experienced by
workers and its discernible effects. Such work may go a long
way in understanding India’s burden of heat stress illness,
both occupational and otherwise.
CONCLUSION
The study highlights that the construction workers have
a high burden of heat related discomfort and illness,
particularly during summer months. Rapid growth, increasing
urbanization, and frequent high heat episodes in Gujarat
and Western India make the construction sector extremely
vulnerable. This population should be a key focus of heat
illness prevention activities, and continued cooperative efforts
between the public and private sectors to protect the health
of these essential workers should be encouraged.
Acknowledgements
We would like to acknowledge that this paper was developed
in conjunction with the on‑going research collaboration
formalized under a memorandum of understanding among
the Ahmedabad Municipal Corporation, the Gujarat
Government, the Public Health Foundation of India, Indian
Institute of Public Health, and the Natural Resources
Defense Council (NRDC).Additional support came from
the Indo‑US Science and Technology Forum (IUSSTF),
Climate and Development Knowledge Network (CDKN),
and the Ahmedabad Heat and Climate Study Group,
which consists of (in alphabetical order): Dr. Gulrez Shah
Azhar (IIPH‑G), Bhaskar Deol (NRDC), Dr. Priya Dutta
(IIPH‑G), Dr. Ajit Rajiva (IIPH‑G), Dr. Abhiyant Tiwari (IIPH‑G),
Dr. Dileep Andhare (IIPH‑G), Dr. Jeremy Hess (Emory
University), Anjali Jaiswal (NRDC), Dr. Kim Knowlton (NRDC
and Mailman SPH, Columbia University), Dr. Dileep Mavalankar
(IIPH‑G) and Dr. Perry Sheffield (Icahn SOM at Mount Sinai).
Dutta, et al.: Perceived heat stress
158 Indian Journal of Occupational and Environmental Medicine - December 2015 - Volume 19 - Issue 3
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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