ArticlePDF Available

Abstract and Figures

Background: Qatar is a major destination country for Nepali migrant workers (NMWs; main age range 25-35 years) in the construction trade. These 120,000+ NMWs are exposed to various occupational hazards, including excessive heat, and 3-4 workers die each week. Our study aimed to show whether heat exposure caused deaths. Methods: The worker population and mortality data of NMWs were retrieved from government institutions in Nepal. Heat exposure was assessed by monthly estimates of daily wet bulb globe temperature (WBGT), for in-shade conditions, from data collected at the Doha weather station from 2009 to 2017. Working in the sun during the middle of the day would add 2-3°C to the in-shade WBGT values. Daily deaths and their causes were obtained from the records of the Foreign Employment Promotion Board (FEPB) in Nepal, 2009-2017. Interviews with returning NMWs about their working conditions and the impacts of these conditions added information. The association between the heat variable and mortality was tested with standard statistical methods. Results: The average annual death rate for NMWs in Qatar was 150 deaths/100,000. According to interviews, the majority of NMWs were found working in high WBGT (>31°C) each working day during hot months. The major cause of these deaths was recorded as cardiovascular problems (cardiovascular disease; CVD). Unfortunately, the causes of death were poorly described, and many deaths were listed as "cardiac arrest." We included these deaths in the broader category of "cardiovascular causes." There was a strong correlation between average monthly afternoon heat levels (WBGT) and CVD mortality. It is likely that a large proportion of these CVD deaths during hot months were due to serious heat stroke. Global studies show that approximately 15% of deaths in the age group 25-35 years are due to CVD causes. However, in this NMW population, the figures were 22% during the cool season and 58% during the hot season. Conclusions: The increased CVD mortality during hot periods is most likely due to severe heat stress. As many as 200 of the 571 CVD deaths during 2009-2017 could have been prevented if effective heat protection had been implemented as a part of local occupational health and safety programs. There is an urgent need for protection against such heat effects among NMWs, and rising temperatures from ongoing climate change are further increasing the health risks. Cause of death records for workers dying in hot conditions should be more precise than "cardiac arrest."
Content may be subject to copyright.
Cardiovascular Biomarkers: Research Article
Cardiology
Heat Stress Impacts on Cardiac Mortality
in Nepali Migrant Workers in Qatar
Bandana Pradhan
a Tord Kjellstrom
b, c Dan Atar
d, e Puspa Sharma
f
Birendra Kayastha
g Gita Bhandari
a Pushkar K. Pradhan
f
a Institute of Medicine, Tribhuvan University, Kathmandu, Nepal; b National Centre for Epidemiology and Population
Health, Australian National University, Canberra, ACT, Australia; c Center for Technology Research and Innovation,
Limassol, Cyprus; d Department of Cardiology B, Division of Medicine, Oslo University Hospital, Oslo, Norway; e Institute
of Clinical Sciences, University of Oslo, Oslo, Norway; f Central Department of Geography, Tribhuvan University,
Kathmandu, Nepal; g Central Bureaus of Statistics, Government of Nepal, Kathmandu, Nepal
Received: April 11, 2019
Accepted: May 2, 2019
Published online: July 12, 2019
Dan Atar
Department of Cardiology B
Oslo University Hospital, Building 3-A
Kirkeveien 166, NO–0407 Oslo (Norway)
E-Mail dan.atar @ medisin.uio.no
© 2019 S. Karger AG, Basel
E-Mail karger@karger.com
www.karger.com/crd
DOI: 10.1159/000500853
Keywords
Nepali migrant workers · Heat exposure · Climate change ·
Cardiovascular health · Mortality · Qatar
Abstract
Background: Qatar is a major destination country for Nepali
migrant workers (NMWs; main age range 25–35 years) in the
construction trade. These 120,000+ NMWs are exposed to
various occupational hazards, including excessive heat, and
3–4 workers die each week. Our study aimed to show wheth-
er heat exposure caused deaths. Methods: The worker pop-
ulation and mortality data of NMWs were retrieved from
government institutions in Nepal. Heat exposure was as-
sessed by monthly estimates of daily wet bulb globe tem-
perature (WBGT), for in-shade conditions, from data collect-
ed at the Doha weather station from 2009 to 2017. Working
in the sun during the middle of the day would add 2–3 ° C to
the in-shade WBGT values. Daily deaths and their causes
were obtained from the records of the Foreign Employment
Promotion Board (FEPB) in Nepal, 2009–2017. Interviews
with returning NMWs about their working conditions and
the impacts of these conditions added information. The as-
sociation between the heat variable and mortality was test-
ed with standard statistical methods. Results: The average
annual death rate for NMWs in Qatar was 150 deaths/100,000.
According to interviews, the majority of NMWs were found
working in high WBGT (> 31 ° C) each working day during hot
months. The major cause of these deaths was recorded as
cardiovascular problems (cardiovascular disease; CVD). Un-
fortunately, the causes of death were poorly described, and
many deaths were listed as “cardiac arrest.” We included
these deaths in the broader category of “cardiovascular
causes.” There was a strong correlation between average
monthly afternoon heat levels (WBGT) and CVD mortality. It
is likely that a large proportion of these CVD deaths during
hot months were due to serious heat stroke. Global studies
show that approximately 15% of deaths in the age group
25–35 years are due to CVD causes. However, in this NMW
population, the figures were 22% during the cool season and
58% during the hot season. Conclusions: The increased CVD
mortality during hot periods is most likely due to severe heat
stress. As many as 200 of the 571 CVD deaths during 2009–
2017 could have been prevented if effective heat protection
had been implemented as a part of local occupational health
and safety programs. There is an urgent need for protection
against such heat effects among NMWs, and rising tempera-
tures from ongoing climate change are further increasing
the health risks. Cause of death records for workers dying in
hot conditions should be more precise than “cardiac arrest.”
© 2019 S. Karger AG, Basel
Downloaded by: D. Atar - 30355
172.16.6.162 - 7/15/2019 10:34:24 AM
Pradhan/Kjellstrom/Atar/Sharma/
Kayastha/Bhandari/Pradhan
Cardiology
2
DOI: 10.1159/000500853
Introduction
Nepal is one of the countries in South Asia that sends
large numbers of migrant workers to the Arab/Persian
Gulf states, including Qatar. Labor migration from Nepal
is approved by the Labor Act of 1985 [1], and there has
been a rapid rise in the number of Nepali migrant work-
ers (NMWs) in overseas countries beyond India [2]. Qa-
tar is one of the top 5 destinations with the highest num-
ber of NMWs. More than half a million NMWs have mi-
grated to Qatar for work [3]. Along with the demand for
low-skilled labor, Nepalis also seek work overseas as a re-
sult of poverty, unemployment, slow economic growth,
and political instability at home. The contribution of the
migrant workers’ remittances constitutes about 25% of
Nepal’s gross domestic product [3].
NMWs in some countries are vulnerable to various
work environment hazards, such as extreme hot weather,
poor sociocultural milieu, technology, and most signifi-
cantly the “Kafala” working system that treats migrant
workers as bonded laborers [4]. More than 1,300 Nepali
migrants working in Qatar have died in the period 2009–
2017 (1 death every second day) [5–8]. The annual mor-
tality rate for NMWs in Qatar is 150/100,000 NMWs [8].
Occupational heat stress (exposure) and heat stroke
(health effect) happens when a worker carries out unin-
terrupted strenuous physical activity in a hot environ-
ment [9]. ISO standards contain methods to ensure the
safety and health of workers, but preventive measures are
often not enforced [9].
Heat stroke and other health effects of heat exposure
are noncommunicable disorders. A nationally represen-
tative cross-sectional survey determined risk factors of
noncommunicable diseases (NCDs) in Nepal [10]. The
most common risk factors are low fruit and vegetable
consumption, alcohol consumption, smoking, low physi-
cal activity, overweight and obesity, raised blood pres-
sure, and raised total cholesterol [10]. Heat exposure was
not reported as a potential risk factor.
A study of NCDs in 31 hospitals across Nepal found
that 37% of patients were admitted with NCDs, of which
38% were cardiovascular disease (CVD) [11]. Another
hospital-based study showed that the relative incidence
of CVD was on average 31% [12] (5–40% in different
hospitals) based on data from cardiac clinics of recent
years (2008–2011) throughout Nepal [13]. Another hos-
pital-based study (all ages) showed that the main cause
of death was respiratory disease with 39%, followed by
infections with 21% and hepatobiliary disease with 16%
[14].
CVD is an increasing problem [15] in many coun-
tries and shows a seasonal pattern, with an increase in
CVD mortality during the winter months, particularly
linked to cold spells affecting elderly people [16, 17].
CVD mortality in countries “close to the equator” is
relatively stable through the year [17]. In countries lo-
cated further away from the equator, in both the North-
ern and Southern hemispheres, data show that the hot-
test month has on average a 12–15% higher CVD mor-
tality than the annual mean mortality [17]. There is an
increase in deaths during the summer months due to
heat exposure [18–21]. A study in Beijing showed that
a continuation of high heat exposure persisting over
several days increased the CVD mortality in all age
groups [19], with a particularly high increase among
people working in outdoor environments. Five consec-
utive days with a peak temperature over 32°C resulted
in a 20% excess of such deaths; for 11 consecutive days,
that figure increased beyond 150% [19]. Climate change
is likely to aggravate the existing situation, with increas-
ing cardiovascular mortality and morbidity among the
exposed vulnerable populations or significant disrup-
tion of work activities when it gets too hot to carry out
normal work [22, 23]. In addition, diurnal temperature
range may be an important meteorological indicator as-
sociated with global climate change that can be linked
with mortality and morbidity [24]. The risk for heat ill-
ness and acute workplace injury due to exertion was
higher with increasing ambient wet bulb globe temper-
ature (WBGT) [25]. Our particular interest is whether
occupational heat exposure causes cardiovascular mor-
tality among NMWs.
Materials and Methods
Mortality data and other information on the NMW deaths in
Qatar were gathered from the Nepalese government agencies re-
lated to foreign migrant workers, including the Department of
Foreign Employment (DoFE), Foreign Employment Promotion
Board (FEPB), the Ministry of Labor and Employment (MoLE),
and from academic works (journal articles, thesis), websites, and
media information [26, 27]. These sources provided information
to describe the trend of NMWs in Qatar and their death rate and
reported causes of death.
The database of the FEPB uses 7 groups for the classification of
the deceased NMWs, namely (a) cardiac arrest, (b) heart attack, (c)
suicide, (d) road traffic accident, (e) workplace accident, (f) mur-
der, and (g) natural cause/unidentified causes. For this study, data
for cardiac arrest and heart attack have been combined into 1
group as “cardiovascular deaths.” Future records on mortality
among NMWs should ideally consider the links of deaths with en-
vironmental conditions, such as heat.
Downloaded by: D. Atar - 30355
172.16.6.162 - 7/15/2019 10:34:24 AM
Heat Stress and Cardiac Mortality in
Nepali Migrant Workers
3
Cardiology
DOI: 10.1159/000500853
Daily climate data for Qatar airport (1983–2017) were down-
loaded from the Climate Data and Heat Exposure Software and
Database: Hothaps-Soft [28] (see website www.ClimateCHIP.org).
The data in Hothaps-Soft for individual weather stations originate
from the US NOAA GSOD database, but the user-friendly soft-
ware/database (Hothaps-Soft in ClimateCHIP.org) makes various
analyses and presentations much easier. Monthly Qatar grid cell
climate data originating from the Climate Research Unit, Univer-
sity of East Anglia, were also used for longer-term heat trend anal-
ysis. The monthly averages of specific variables, gathered from
both Hothaps-Soft (weather station data) and www.ClimateCHIP.
org (grid cell data), were very much in agreement.
The daily minimum (min), maximum (max), and mean tem-
peratures, as well as daily dew point estimates, were available for
more than 3 decades, and their trends were analyzed. The widely
used occupational heat stress index, WBGT [23], conceptually in-
tegrates temperature, humidity, wind speed, and heat radiation to
assess the degree of heat stress [28–31]. The NMWs are primarily
construction workers, so their daily tasks may involve work in the
sun, while many activities are carried out in shaded areas or under
roofs. Assuming that there is no heat radiation from the sun and
that the air movement over the exposed skin is 1 m/s (similar speed
as moving arms and legs in typical work situations), we can calcu-
late WBGT (in-shade) with the method by Kjellstrom et al. [29] (see
also website www.ClimateCHIP.org). Heat radiation from the sun
is primarily an issue during the middle hours of a day when the heat
from the sun adds approximately 2–3°C to the in-shade WBGT
[32].
Basic statistical methods were used to assess the relationship
between monthly and seasonal (3-monthly) WBGT levels and the
NMW mortality rates for different causes of death, i.e., Pearson
correlation, linear regression, and Student’s t test.
Results
Climate Conditions in Nepal and Qatar
The geographical features and climatic conditions
of Nepal are quite different from those in Qatar. Nepal
is 147,000 km2 in area and is a predominantly moun-
tainous country with 3 broad ecological regions: the
Plain (Tarai) region approximately 100 m above sea
level (masl), similar to the sub-tropical climate of the
neighboring Ganges river plain in India; the Hill re-
gion (Pahad) with altitudes between 1,000 and 2,000
masl and a temperate climate; and the Mountain re-
gion (Himal) with altitudes of inhabited areas from
3,000 to 6,000 masl and a more arctic climate. The
highest population density is in Tarai and Pahad, and
most NMWs are likely to come from these regions.
Summer temperatures can go up above 30°C, while
winter temperatures are much colder going down be-
low 10°C on cool days. Annual precipitation is ap-
proximately 1,000 mm in Tarai, mainly occurring dur-
ing the mid-year monsoon. Kathmandu in Pahad has
similar rainfall patterns, while areas closer to Himal
(e.g., Pokhara) have almost 4,000 mm of annual pre-
cipitation [33].
Qatar is a peninsula close to the Arab/Persian Gulf,
12,000 km2 in area. An annual average of daily maximum
temperatures above 33°C has been measured for every
year since 2000. Daily values reach 45–50°C during the
hot summer months from June through September. The
climate is a desert type, very hot and dry. Unlike in Nepal,
precipitation in Qatar occurs during the winter months
from October to February when average temperatures re-
main below 20°C. The annual average precipitation in
Qatar is about 85 mm [34]. The temperatures in both Ne-
pal and Qatar are increasing as a sign of ongoing climate
change [35, 36].
Trend of NMWs in Qatar
Since the 1990s, the numbers of NMWs in the Gulf Co-
operation Council (GCC) countries, such as Bahrain, Ku-
wait, Oman, Qatar, Saudi Arabia, and the United Arab
Emirates, have increased, but in recent years they stabi-
lized just below 300,000 [3]. The NMWs in GCC represent
approximately 56% of the total Nepali workers abroad.
Table 1 reveals that Qatar alone accounted for approxi-
mately 40% of the NMWs in the GCC during the last de-
cade [3]. Table 1 shows the figures we have used to calcu-
late annual mortality rates for different causes of death.
Figure 1 shows the rising number of NMWs working in
Qatar since 1994. The figures increased to over 100,000 in
2012, when Qatar won a bid in 2010 for the Soccer World
Cup 2022. The number of NMWs in Qatar reached 130,000
in 2015. This type of employment provides an important
source of income for their families in Nepal (Fig.1).
Table 1. Qatar’s share of NMWs with labor permit in GCC by year
YearaTotal GCC % Qatar %
2009 249,051 182,870 73.4 85,442 46.7
2010 219,965 169,510 77.1 76,175 44.9
2011 294,094 168,302 57.2 55,940 33.2
2012 354,716 240,822 67.9 102,966 42.8
2013 384,665 274,221 71.3 105,681 38.5
2014 453,543 284,392 62.7 103,486 36.4
2015 527,814 297,688 56.4 128,874 43.3
2016 512,887 292,446 57.0 124,368 42.5
2017 383,493 273,398 71.3 121,317 44.4
Total 3,380,228 2,183,649 64.6 904,249 41.4
a Year starts from July to June; source: DoFE, 2017 [3].
Downloaded by: D. Atar - 30355
172.16.6.162 - 7/15/2019 10:34:24 AM
Pradhan/Kjellstrom/Atar/Sharma/
Kayastha/Bhandari/Pradhan
Cardiology
4
DOI: 10.1159/000500853
Deaths of NMWs in Qatar
Table 2 shows that cardiovascular causes are the major
contributors to mortality in NMWs, accounting for 42%
of the total deaths. The records in the Nepal government
agencies include “cardiac arrest” as a cause of death, but
this is inevitably what happens when a person dies. No
autopsies or more detailed investigations were available
to clarify the underlying causes and to determine wheth-
er occupational heat exposure played a role, so the actual
causes of death are uncertain.
The second largest group of deaths is in the category
“natural/other causes” (Table 2). It is not clear what is
meant by “natural causes” of deaths of young fit men. It
should also be noted that suicides occur almost as often
as workplace accidents and road traffic accidents.
Figure 2 shows the monthly variation of the mortality
rates per 100,000 NMWs (expressed as annual rates) due
to cardiovascular causes and workplace accidents as well
as the monthly average of daily WBGTmax (°C; after-
noon values) plotted against the years 2009–2017. The
figure shows a distinct seasonal pattern of the heat index
level WBGT (°C) and mortality due to cardiac causes. The
seasonal variation was tested with the Pearson correlation
coefficient (r = 0.54 for cardiac mortality vs. WBGTmax)
and was statistically significant at a 99% confidence level
with p < 0.01. The deaths due to workplace accidents
show a weaker correlation with the trend of WBGT with
r = 0.19 (not statistically significant; p > 0.05).
The Pearson correlation coefficients for deaths due
to road traffic accident, suicide, murder, and natural
Table 2. Number of deaths of NMWs in Qatar according to registered cause
Year Cardiovascular Suicide WPA RTA Murder Natural/
other
Total
n%n%n%n%n%n%
2009 50 52 3 3 6 6 5 5 0 0 32 33 96
2010 60 52 10 9 13 11 7 6 18 16 8 7 116
2011 56 48 8 7 16 14 9 8 1 1 27 23 117
2012 62 44 11 8 25 18 20 14 2 1 22 15 142
2013 72 41 15 9 17 10 9 5 1 1 60 34 174
2014 73 41 13 7 19 11 18 10 1 1 52 30 176
2015 56 31 23 13 23 13 17 9 0 60 34 179
2016 65 36 18 10 34 19 24 13 0 0 41 23 182
2017 77 45 15 9 16 9 28 16 0 0 36 21 172
Total 571 42 116 9 169 12 137 10 23 2 338 25 1,354
Source: DoFE, 2017 [3]; FEPB, 2017 [8]. % is related to the annual total deaths. WPA, workplace accident; RTA, road traffic accident.
140
120
100
80
60
40
20
0
1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016
NMWs, ×1,000
NMWs
Fig. 1. Number of NMWs in Qatar by year.
Source: DoFE, 2017 [3].
Downloaded by: D. Atar - 30355
172.16.6.162 - 7/15/2019 10:34:24 AM
Heat Stress and Cardiac Mortality in
Nepali Migrant Workers
5
Cardiology
DOI: 10.1159/000500853
causes were r = –0.063, –0.144, –0.078, and –0.127, re-
spectively; they were not statistically significant. How-
ever, the Pearson correlation coefficient between
monthly WBGTmax (°C) and total deaths per 100,000
NMWs in Qatar was statistically significant with r =
0.24 and p < 0.05.
Figure 2 also shows that the seasonal pattern ap-
peared to change in 2015 and 2016 with lower than ex-
pected monthly mortality rates due to cardiac causes
during the hot months of the years. Apparently, the
pattern returned in 2017, but the lack of a de-
tailed individual cause of death analysis makes this un-
certain.
Analysis of Qatar Temperature and Heat Stress
Trends
Temperature Trends
The recent monthly means of daily maximum (Tmax)
and minimum temperature (Tmin) and their longer-
term decadal trends in Qatar (Table 3) show extreme heat
levels in the hottest months, and the trends are strongly
positive for most months. Annual averages of daily max-
imum and minimum temperature trends are estimated to
be 0.54°C/decade and 1.1°C/decade with standard errors
of 0.11 and 0.07°C, respectively. The difference in the
maximum and minimum trends could be due to the Ur-
ban Heat Island effect, which adds more to the nightly
minimum temperatures than to the midday maximum
temperatures.
These data are from Doha International Airport and
are used to represent the heat situation in the populated
areas of Qatar, which are close to the airport and at
thesame altitude. The weather station and grid cell val-
ues for Qatar are almost identical, so we assume these
data indicate the heat exposure situation in shade in
Qatar.
Heat Stress Index Levels (WBGT)
The calculated WBGT heat stress index levels in the
hotter months (Table 4), when the air humidity is very
low. These are very similar to the minimum tempera-
tures (Table 3), while in the more humid, cooler months
the WBGT levels are higher. The scale for interpretation
of WBGT is different from the temperature interpreta-
tion, so a 26°C level for WBGTmax is creating more heat
stress on a person than a Tmax at the same level. It should
also be remembered that the WBGT in the sun at midday
is likely to be 2–3°C higher than the full-shade values
[37].
According to National Institute for Occupational
Safety and Health (NIOSH; 2016), recommendations
for heat protection vary according to work intensity
(light, medium, heavy, and very heavy work), which in
turn determine what is a safe WBGT (°C) [38]. During
the hot months in Qatar, WBGTmax ranges from 29 to
34°C (Table 4). If recommendations were followed,
workers would only be able to perform light work dur-
ing the hottest hours, while for heavy work, they would
40
35
30
25
20
15
10
5
0
WBGT, °C
200
150
100
50
0
–50
Mortality per 100,000 NMWs
WBGTmax CVP W PA
2009 2010 2011 2012 2013 2014 2015 2016 2017
J A J O J A J O J A J O J A J O J A J O J A J O J A J O J A J O J A J O
Fig. 2. WBGTmax and deaths of NMWs in Qatar (2009–2017). CVP, cardiovascular problems; WPA, workplace accident.
Downloaded by: D. Atar - 30355
172.16.6.162 - 7/15/2019 10:34:24 AM
Pradhan/Kjellstrom/Atar/Sharma/
Kayastha/Bhandari/Pradhan
Cardiology
6
DOI: 10.1159/000500853
need to take 50–100% rest each hour as a precaution to
be safe from heat stress [38]. According to interviews
with returning NMWs, they were expected to work
continuously even in high WBGT > 30°C. If rest periods
are not allowed during such hot work, the health risk
due to heat stress increases and may ultimately result in
death [23].
Table 4 shows that the decadal trend of WBGT for
most of the hot months is slower than for Tmax (Table 3),
reflecting reduced humidity during certain months and
the scale factor (Tmax = 1.3 × WBGTmax). During the 6
hotter months (Table 4), WBGTmax (afternoon heat) is
higher than 26°C every day, and in the 3 hottest months,
WBGTmean (sunrise and sunset value) is also higher
Table 3. Temperatures (° C) in shade of Qatar (2015–2017) and decadal trends (1983–2017)
Month Tmax (95% CI)
2015–2017
Trend/decade
1983–2017
Tmin (95% CI)
2015–2017
Trend/decade
1983–2017
Monthly data for four 3-month periods, starting with the hottest period
June 42.1 (39–46) 0.49 (0.14)*31.3 (29–35) 1.16 (0.13)*
July 42.9 (38–47) 0.46 (0.13)*33.1 (31–35) 1.29 (0.10)*
August 42.2 (39–46) 0.46 (0.12)*32.7 (31–34) 1.09 (0.11)*
September 39.7 (37–44) 0.52 (0.11)*30.7 (28–33) 1.28 (0.10)*
October 36.3 (33–41) 0.46 (0.14)*27.2 (25–30) 1.16 (0.12)*
November 30.1 (26–34) 0.07 (0.15) 22.8 (20–26) 0.97 (0.14)*
December 25.1 (22–30) 0.31 (0.26) 17.3 (14–21) 0.61 (0.20)*
January 23.6 (19–28) 0.47 (0.25) 15.4 (12–18) 1.04 (0.21)*
February 24.2 (19–30) 0.59 (0.23)*15.8 (11–21) 0.88 (0.18)*
March 27.3 (24–31) 0.87 (0.30)*19.6 (17–23) 1.17 (0.16)*
April 34.1 (28–40) 0.71 (0.23)*24.0 (20–27) 1.14 (0.16)*
May 40.1 (36–44) 0.59 (0.18)*29.5 (27–33) 1.20 (0.15)*
Tmax and Tmin indicate averages of daily maximum (and minimum) temperatures each month; confidence
intervals (CI) for daily values and standard errors of trends in parentheses. *Statistically significant (p < 0.05)
difference from zero.
Table 4. Heat index levels, WBGT (° C) in shade of Qatar (2015–2017) and decadal trends (1983–2017)
Month WBGTmax
(95% CI)
2015–2017
Trend per
decade
1983–2017
Days above WBGTmax or WBGTmean
>26°C >29°C >32°C
max mean max mean max mean
Six hottest months
May 28.5 (26–31) 0.31 (0.14)*30 10 10 0 0 0
June 29.6 (26–32) 0.17 (0.14) 30 20 20 3 0 0
July 32.4 (29–35) 0.24 (0.14) 30 29 30 20 2 0
August 34.1 (33–36) 0.62 (0.16)*30 30 30 30 4 0
September 31.8 (30–34) 0.33 (0.16)*30 30 30 17 1 0
October 28.7 (27–32) 0.37 (0.12)*30 15 11 1 0 0
Average 30.9 0.34
WBGTmax and WBGTmean indicate monthly averages of daily maximum (and mean) heat levels. The
interpretation of the WBGT (° C) heat stress classification can be as follows: moderate = 28° C; *strong = 29° C+;
**very strong = 30° C+; ***extreme = 32° C+.
Downloaded by: D. Atar - 30355
172.16.6.162 - 7/15/2019 10:34:24 AM
Heat Stress and Cardiac Mortality in
Nepali Migrant Workers
7
Cardiology
DOI: 10.1159/000500853
than this level every day. In the hottest 3 months, WBGT-
max is above 29°C every day.
Analysis of NMWs’ Mortality from Cardiovascular
Causes in Qatar
Table 5 depicts the monthly mortality data for NMWs
in Qatar from 2009 to 2017 (expressed as annual mortality
rates in order to make all numbers comparable). The
monthly total mortality rates indicate higher levels during
the beginning of the hot season (April to July) than during
the rest of the year, but the difference is relatively small. The
mortality rate due to cardiovascular causes in hotter
months was almost double the level of the other months
(Table 5). The heat starts already before May (Table 3), and
the increase in the cardiovascular cause death rate in 2009–
2017 began in April and reached a peak in July (Table 5).
To better visualize the effect of heat, the year is divided
into four 3-month “seasons” (Table 3), and the average of
daily WBGTmax (°C), as well as the total and cardiovascu-
lar mortality for each season (calculated as the equivalent
annual rate per 100,000 NMWs in Qatar), is shown in Fig-
ure 3. The seasonal trends of WBGT are very regular with
levels around 20°C in the coolest season and above 30°C
in the hottest season. The total deaths and cardiovascular
deaths follow similar patterns with the highest rates in the
hottest season until 2014, after which the patterns change.
The average mortality rate of cardiovascular deaths for
NMWs in Qatar during the years 2009–2014 was higher
(73/100,000) than during the years 2015–2017 (53/100,000).
A similar, but smaller, trend was found for the “total” mor-
tality between the 2 groups of years (155 vs. 142/100,000).
There is reason to believe that from 2015/2016 onwards,
media attention to the workplace heat conditions played a
role for the application of preventive methods, which led
to the changed seasonal pattern of cardiac mortality shown
in Figure 3. We have, therefore, analyzed the relationship
between heat levels and cardiovascular cause mortality us-
ing the 2009–2014 dataset as the starting point.
Analysis of NMWs’ Mortality due to Cardiac Causes
and Heat Exposure
The relationship between monthly WBGTmax levels
and mortality rates from 2009 to 2014 was plotted (Fig.4),
and the coefficient of determination (r2) was 0.40, which
implies that 40% of the variation of specific monthly data
could be explained by the relationship between the heat lev-
els and cardiovascular mortality. The linear regression
function (y = 5.5x – 71) shown in Figure 4 with its 95% con-
fidence interval indicates a substantial difference of cardio-
vascular mortality as a function of in-shade heat levels. At
low heat exposure levels (WBGT = 20°C), the average mor-
tality rate is approximately 40/100,000 NMWs (95% CI 27–
53), while at high heat levels (WBGT = 30°C), the average
mortality rate is approximately 95/100,000 NMWs (95% CI
83–107). There is substantial scatter of individual monthly
data, but on average for each increase of WBGT by 1°C, the
mortality rate goes up by 5.5/100,000 NMWs (Fig.4).
As the time trend in Figure 3 was made clearer by us-
ing 3-monthly seasonal data rather than monthly data,
we also tested the correlation during the period 2009–
2014 for such 3-monthly time units. The coefficient of
determination (r2) was higher at 0.50, and the linear re-
gression function (y = 5.7x – 71) increased in a similar
manner to the monthly data. Thus, the increase in car-
diovascular cause mortality in the hotter seasons is well
established.
Additional analysis was carried out concerning the rel-
ative mortality ratios as the percentage of cardiovascular
causes within the total NMW mortality. Usingmonthly
data on WBGTmax and percentage of cardiovascular
cause deaths in 2009–2014, we found an r2 at 0.59 and a
linear regression function of y = 3.4x – 44. At a monthly
Table 5. NMW mortality data by month, 2009–2017
Cardiovascular
causes
Total deaths
nper
100,000
NMWsa
nper 100,000
NMWsa
Hottest months
May 57 76 123 163
June 71 94 137 182
July 81 107 130 173
August 52 69 98 130
September 51 68 88 117
October 54 72 112 149
Subtotal, mean 366 81 688 152
Cooler months
November 29 38 102 135
December 20 27 110 146
January 24 32 106 141
February 24 32 98 130
March 37 49 113 150
April 71 94 137 182
Subtotal, mean 205 45 666 147
Total, mean 571 63 1,354 150
aExpressed as the equivalent annual mortality rates.
Downloaded by: D. Atar - 30355
172.16.6.162 - 7/15/2019 10:34:24 AM
Pradhan/Kjellstrom/Atar/Sharma/
Kayastha/Bhandari/Pradhan
Cardiology
8
DOI: 10.1159/000500853
average of daily WBGTmax of 20°C, the rate of cardio-
vascular deaths was 22%, and at a WBGTmax of 30°C,
the rate of cardiovascular deaths was 58%. The increase
is highly statistically significant (p < 0.01).
In Figure 5, we compared the recorded 3-monthly mor-
tality rates as reported for the period 2009–2017 (CV: 09–
17) and the estimated 3-monthly rates based on the linear
regression formula above for WBGTmax versus cardio-
vascular mortality (CV-est). The changed pattern in 2015–
2016 is clear, and a key question is whether the change
represents the impact of preventive actions.
Discussion
The above findings indicate that cardiovascular causes
of death are a problem for the NMWs in Qatar, peaking
during the hot summer months. People working continu-
ously in an extremely hot environment are vulnerable to
fatal heat strokes [22, 23]. According to information ac-
quired from discussions with returned NMWs from Qa-
tar, most of them had worked more than 12 h per day in
heat levels of WBGT of 26–31°C without appropriate
breaks [3]. This heat exposure is likely to be a serious
250
200
150
100
50
0
NMW mortality rate, per 100,000
35
30
25
20
15
10
5
0
WBGT, °C
Season CV Season total WBGT
2009 2010 2011 2012 2013 2014 2015 2016 2017
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
Fig. 3. 3-month seasonal trends for WBGT and NMW mortality. Daily WBGTmax values are presented in °C.
Mortality rates per 100,000 NMW (annual equivalent) are indicated. Total, all deaths; CV, cardiovascular deaths;
DJF, Dec., Jan., Feb.; MAM, Mar., Apr., May; JJA, Jun., Jul., Aug.; SON, Sep., Oct., Nov.
200
160
120
80
40
0
0 5 10 15 20 25 30 35
40
Deaths per 100,000 NMWs
y = 5.5x – 71
Monthly WBGTmax, °C
Fig. 4. Deaths due to cardiovascular causes
among NMWs in Qatar, 2009–2014. Re-
gression function: y = 5.5x – 71, where x is
the explanatory variable (monthly WBGT
°C) and y is the dependent variable (death
per 100,000 NMWs).
Downloaded by: D. Atar - 30355
172.16.6.162 - 7/15/2019 10:34:24 AM
Heat Stress and Cardiac Mortality in
Nepali Migrant Workers
9
Cardiology
DOI: 10.1159/000500853
health risk according to the recommended occupational
health standards [22, 31, 38–41].
The ages of the NMWs in Qatar ranged from 18 to 45
years, with about three-quarters of them aged 25–35 years.
The age of the deceased persons was not recorded in the
Nepalese government dataset but was obtained from their
passport information. The majority of the deaths were in
the age group 25–35 years. On average, the annual total
death rate from 2009 to 2017 was 150/100,000 for the
NMWs in Qatar (1,354/904,249; Tables 1, 2). At a national
level, in Nepal in 2011 the estimated total mortality rate was
240/100,000 for men aged 25–35 years [42]. The difference
could be due to the inadequacy of the workers’ death re-
cords and could also indicate the “healthy worker effect”
proposed by McMichael [43] in 1976. The NMWs are a
selected group with healthy and strong bodies, and they
would not be expected to die while working in Qatar. While
some accidental injuries and a few cases of disease would
be expected, a high proportion of cardiovascular deaths
would be surprising in such a healthy group of people.
Cardiovascular causes of death in the whole group
amounted to 42% of all deaths, and this relative mortality
rate was 22 and 58% at a monthly WBGTmax of 20 and
30°C, respectively. Detailed age- and cause-specific mor-
tality rates for Nepal are not available, but comparing
them with the Global Burden of Disease estimates of
CVD rates at different ages [44], we find that in the age
group 25–35 years the relative mortality rate for CVD is
approximately 15%. The NMW finding at a low WBGT-
max in winter is close to this, while the summer mortal-
ity rate due to cardiovascular causes is several times high-
er. Another issue to consider is the winter/summer varia-
tion of CVD deaths in general and their relation to heat
exposures [20]. On average, the summer mortality in hot
parts of the world is approximately 10–20% higher than
the annual average. Our seasonal ratio is much higher,
which indicates the particular vulnerability of people do-
ing intensive physical work.
While the causes of death were rather vague and inad-
equate in many cases, e.g., “cardiac arrest,” we considered
that the most likely underlying cause was heat stroke.
Cardiac arrest is not a diagnosis usually used in clinical
trial adjudications. The term “sudden cardiac death”
(SCD) is more appropriately used when a person is col-
lapsing, i.e., acutely losing consciousness and/or dying
without any previous symptoms that could point to an
160
140
100
120
80
40
60
20
0
NMW mortality rate, per 100,000
35
30
25
20
15
10
5
0
WBGT, °C
CV:09–17 CV-est WBGT
2009 2010 2011 2012 2013 2014 2015 2016 2017
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
DJF
MAM
JJA
SON
Fig. 5. 3-month seasonal trends for WBGT and NMW cardiovas-
cular mortality, actual (CV: 09–17) and estimated (CV-est) from
the regression function in Figure 4. Daily WBGTmax values are
presented in °C. Mortality rates per 100,000 NMW (annual equiv-
alent) are indicated. CV, cardiovascular mortality; DJF, Dec., Jan.,
Feb.; MAM, Mar., Apr., May; JJA, Jun., Jul., Aug.; SON, Sep., Oct.,
Nov.
Downloaded by: D. Atar - 30355
172.16.6.162 - 7/15/2019 10:34:24 AM
Pradhan/Kjellstrom/Atar/Sharma/
Kayastha/Bhandari/Pradhan
Cardiology
10
DOI: 10.1159/000500853
organ-specific diagnosis. In this sense, SCD comprises a
wide spectrum of pathologies, e.g., fatal arrhythmia, fatal
acute myocardial infarction, fatal stroke, fatal ruptured
abdominal aortic aneurysm, acute fatal pulmonary em-
bolism, acute heart valve rupture, etc.
Since young and healthy men very rarely have the con-
ditions mentioned above, the assumption that their car-
diac arrest is triggered by a heat stroke is adequate. We
suggest that the ICD code T67 (Heat Stroke, in ICD 10)
should be used for this type of cases. We found a strong
correlation between monthly WBGTmax and the death
rate due to cardiovascular causes (Fig.3, 4). In the past,
heat stroke mortality has primarily been analyzed as a
problem for elderly people during heat waves, but there
are reports on the deaths of working people during heat
waves, and this is now given more attention to in occupa-
tional health assessments [32, 45, 46].
From May to October in Qatar, the average maximum
temperature goes above 36°C (Table 3), and the deaths
of NMWs due to cardiovascular causes are at a higher
level than during the cooler months (Table 5). Similar
results were found in studies in China [19, 21]. Of par-
ticular interest was the finding that during continued pe-
riods of heat during heat waves, working people had an
almost 150% increase in cardiovascular mortality [19].
Our findings are in line with this observation.
The earlier years of our study showed quite dramat-
ic seasonal variations in the cardiovascular cause mor-
tality. In 2015 and 2016, the pattern was different with
dips in such mortality during the hottest months
(Fig.5). There was major pressure from different orga-
nizations including media [5, 27, 47–49] in 2014 on the
Qatar government to undertake measures to improve
occupational safety, which could explain the change in
that time, but in 2017, the summer peak of cardiovas-
cular deaths returned (Fig.3, 5). Unless further preven-
tive actions are taken, the high death rate is likely to
continue into the future [49]. Employment opportuni-
ties for Nepalis are growing in Qatar, but the number
of deaths of NMWs has not decreased. The annual
number of deaths of the NMWs in Qatar accounted for
40% of the total NMW deaths in the GCC and 26% of
the total NMW deaths abroad [3]. From the data pre-
sented in Figure 5, we can estimate that close to 200
NMW deaths would have been prevented if the cardio-
vascular mortality had stayed at approximately
50/100,000 (as in 2015–2016) during the hot summer
months from 2009 to 2014.
Prevention of heat stress among these and other work-
ers in similar conditions is very important. Employers
should provide unlimited drinking water, awareness
training to workers about the prevention of heat stress or
minimizing its effects via acclimatization (short work ex-
posure early in the hot season, followed by gradual in-
creases in intensity and duration), “buddy systems” where
workers do not work alone, frequent work breaks during
soaring heat seasons, adjustment of tasks and procedures,
etc. [23]. Comprehensive advice is available from the
Heat-Shield project (see www.heat-shield.eu) [46].
An emerging issue of importance for occupational
health is the effect of climate change that will bring
more hot days and hotter hot days to workplaces
around the world. The heat trends since 1983 show sig-
nificant increases for almost every month (Tables 3, 4).
Outdoor work is obviously affected, but unless work is
carried out inside vehicles/equipment with air condi-
tioning, millions of indoor workplaces are also high
heat exposure areas. Many factories have large open
areas without walls or air conditioning. Ongoing and
future climate changes will lead to higher heat expo-
sures for billions of people in tropical countries, most
likely affecting poor people in laboring occupations,
adding to the health inequities caused by other health
hazards linked to climate change [50]. A key problem
caused by the heat exposure is the reduction of labor
productivity, recently reported as a major issue for the
local construction industry [51].
Limitations of our Study
The study centered on the reported deaths and their
causes as recorded in official government records; how-
ever, the process created uncertainties because of ob-
served discrepancies in the data. For example, the FEPB
maintains a database of deceased migrant workers whose
kin have sought compensation but does not include data
on undocumented deceased migrant workers. The clas-
sification of the causes of death is neither scientific nor
clear and does not distinguish between the mode of death
and cause of death. However, the deaths assigned to the
“cardiac arrest” or “heart attack” categories were most
likely sudden and unexpected, which fits with the likely
situation for workers dying from heat stroke.
Another uncertainty was the lack of more detailed data
on the type of work each worker was undertaking at the
time of their death, or what preventative approaches were
being implemented when they died. The data on heat levels
are likely to be accurate, at least as representative data for
the geographic area, but the actual heat levels at particular
work sites are likely to vary. Overall, we believe that these
limitations do not undermine the findings of this study.
Downloaded by: D. Atar - 30355
172.16.6.162 - 7/15/2019 10:34:24 AM
Heat Stress and Cardiac Mortality in
Nepali Migrant Workers
11
Cardiology
DOI: 10.1159/000500853
Conclusions
During recent years, approximately 120,000 NMWs
have been working in Qatar, mainly in the construction
industry. Each year, more than 170 workers die, and for
the period 2009–2017, the mean annual total mortality
rate has been 150/100,000. Most of the workers are in the
age range 25–35 years and are most likely very healthy as
they were accepted for this temporary work migration.
The total mortality rate is lower than the likely rate for
this age group at 240/100,000, which may be a reflection
of the “healthy worker effect” (a selection process) or in-
completeness of data collection. In global studies, ap-
proximately 15% of deaths in this age group are due to
cardiovascular causes, but in this NMW population, the
death rate was in the range from 22 to 58% during periods
with daily heat index (WBGT) levels reaching 20°C (cool
season) or 30°C (hot season), respectively. The increasing
cardiovascular mortality rate at higher monthly heat lev-
els was highly statistically significant. We conclude that
the increased cardiovascular mortality during hot periods
most likely is due to severe heat stress among these con-
struction workers. As many as 200 of the 571 cardiovas-
cular deaths during 2009–2017 could have been prevent-
ed if effective heat protection measures had been imple-
mented as a part of local occupational health and safety
programs. There is an urgent need for protection for
NMWs, and other groups, working in hot conditions. It
is important that more precise ICD codes for cause of
death are applied so that the serious effects of heat in
workplaces will not be overlooked by clinicians. Based on
the ongoing trends of monthly heat conditions in Qatar,
we also conclude that climate change is already contribut-
ing to these occupational health risks, and it will further
increase the risks in the future.
Acknowledgements
We gratefully acknowledge the important provision of data
from agencies in the Government of Nepal and the additional infor-
mation provided in interviews. We also acknowledge the contribu-
tions to the graphics presentations by Chris Freyberg, Bruno Lemke,
and Matthias Otto in the Climate Heat Impact Research Program
(CHIRP), Mapua, New Zealand. The work was self-funded.
Statement of Ethics
The yearly data (both spatial and temporal) of NMWs were ob-
tained from the Ministry of Labor and Employment, Government
of Nepal, upon submission of an official letter and proposal of the
study. The ministerial consent to use its data was provided. How-
ever, as per the rules and regulation of the Ministry, the confiden-
tiality of the names and addresses of the deceased persons was
maintained while using their particular data. Similarly, a license
agreement was obtained to use the Hothaps software for weather
station data and analysis. The findings of the study will be offi-
cially shared with the related organizations.
Disclosure Statement
None of the authors has any disclosures in relation to the pub-
lished work.
References
1 Seddon D, Gurung G, Adhikari J. Foreignla-
bour migration and the remittance economy
of Nepal. Himalaya. 1998; 18(2): 3–10.
2 International Labour Organization. Non-
standard employment around the world: Un-
derstanding challenges, shaping prospects.
Geneva: ILO; 2016.
3 Department of Foreign Employment. Labour
Migration for Employment: A Status Report
for Nepal. Kathmandu: Department of For-
eign Employment, Ministry of Labour and
Employment; 2017.
4 Bajracharya R, Sijapati B. The Kafala sys-
tem and its implications for Nepali domes-
ticworkers. Centre for the study of labourand
mobility. Policy Brief. 2012 March; 1.
5 Erfani A. Kicking away responsibility: FIFA’s
role in response to migrant worker abuses in
Qatar’s 2022 World Cup. Jeffrey S. Moorad
Sports LJ. 2015; 22: 623.
6 Department of Foreign Employment. User
Manual of Department of Foreign Employ-
ment (DoFE) Recruitment Agency (RA)
Module. Kathmandu: Department of Foreign
Employment (DoFE), Ministry of Labour and
Employment; 2012.
7 Engle MB. A CN Tower over Qatar: An Analy-
sis of the Use of Slave Labor in Preparation for
the 2022 FIFA Men’s World Cup and How the
European Court of Human Rights Can Stop It.
Hofstra Lab Emp LJ. 2014; 32(1): 177–215.
8 Foreign Employment Promotion Board. Re-
cords of deceased person in Qatar. In: Depart-
ment of Foreign Employment Nepal. Kath-
mandu: Foreign Employment Promotion
Board, Government of Nepal, Ministry of La-
bour and Employment; 2017.
9 Parsons K. Heat stress standard ISO 7243 and
its global application. Ind Health. 2006 Jul;
44(3): 368–79.
10 Aryal KK, Mehata S, Neupane S, Vaidya A,
Dhimal M, Dhakal P, et al. The burden and
determinants of non communicable diseases
risk factors in Nepal: findings from a nation-
wide STEPS survey. PLoS One. 2015 Aug;
10(8):e0134834.
11 Nepal Health Research Council. Prevalence of
Non-communicable Disease in Nepal: Hospi-
tal-based Study. Kathmandu: Nepal Health
Research Council; 2010.
12 Bhandari GP, Angdembe MR, Dhimal M, Ne-
upane S, Bhusal C. State of non-communica-
ble diseases in Nepal. BMC Public Health.
2014 Jan; 14: 23.
13 Shakya S, Sharma D, Bhatta YD. Current sce-
nario of heart diseases in Nepal: at a glance.
Nepalese Heart J. 2011; 8(1): 23–6.
14 Karki RK. Mortality patterns among hospital
deaths. Kathmandu Univ Med J (KUMJ).
2016 Jan-Mar; 14(53): 65–8.
Downloaded by: D. Atar - 30355
172.16.6.162 - 7/15/2019 10:34:24 AM
Pradhan/Kjellstrom/Atar/Sharma/
Kayastha/Bhandari/Pradhan
Cardiology
12
DOI: 10.1159/000500853
15 Lee ES, Vedanthan R, Jeemon P, Kamano JH,
Kudesia P, Rajan V, et al. Quality Improve-
ment for Cardiovascular Disease Care in
Low- and Middle-Income Countries: A Sys-
tematic Review. PLoS One. 2016 Jun;
11(6):e0157036.
16 Stewart S, Keates AK, Redfern A, McMurray
JJ. Seasonal variations in cardiovascular dis-
ease. Nat Rev Cardiol. 2017 Nov; 14(11): 654–
64.
17 Marti-Soler H, Gonseth S, Gubelmann C,
Stringhini S, Bovet P, Chen PC, et al. Season-
al variation of overall and cardiovascular
mortality: a study in 19 countries from differ-
ent geographic locations. PLoS One. 2014
Nov; 9(11):e113500.
18 Pell JP, Cobbe SM. Seasonal variations in cor-
onary heart disease. QJM. 1999 Dec; 92(12):
689–96.
19 Yin Q, Wang J. The association between con-
secutive days’ heat wave and cardiovascular
disease mortality in Beijing, China. BMC
Public Health. 2017 Feb; 17(1): 223.
20 Gasparrini A, Guo Y, Hashizume M, Lavigne
E, Zanobetti A, Schwartz J, et al. Mortality risk
attributable to high and low ambient temper-
ature: a multicountry observational study.
Lancet. 2015 Jul; 386(9991): 369–75.
21 Ban J, Xu D, He MZ, Sun Q, Chen C, Wang
W, et al. The effect of high temperature on
cause-specific mortality: A multi-county
analysis in China. Environ Int. 2017 Sep; 106:
19–26.
22 De Blois J, Kjellstrom T, Agewall S, Ezekowitz
JA, Armstrong PW, Atar D. The effects of cli-
mate change on cardiac health. Cardiology.
2015; 131(4): 209–17.
23 Parsons K. Human thermal environment.
The effects of hot, moderate and cold temper-
atures on human health, comfort and perfor-
mance. 3rd ed. New York: CRC Press; 2014.
24 Zhang Y, Yu C, Yang J, Zhang L, Cui F. Diur-
nal Temperature Range in Relation to Daily
Mortality and Years of Life Lost in Wuhan,
China. Int J Environ Res Public Health. 2017
Aug; 14(8): 891–3.
25 Garzon-Villalba XP, Mbah A, Wu Y, Hiles M,
Moore H, Schwartz SW, et al. Exertional heat
illness and acute injury related to ambient wet
bulb globe temperature. Am J Ind Med. 2016
Dec; 59(12): 1169–76.
26 BBC. Sajha Sawal Episode 281: Nepali Mi-
grant Workers in Qatar. 2013. Available from:
https://bbcmediaaction.imagencloud.com/
record/1523
27 BBC. Sajha Sawal Episode 285: Nepali Mi-
grant Workers in Qatar. 2014. Available from:
https://bbcmediaaction.imagencloud.com/
record/1519
28 Kjellstrom T. Climate Data and Heat Expo-
sure Software: Hothaps-Soft v 1.0.2.4. Heat,
work and health: implications of climate
change 2014. Available from: http://www.cli-
matechip.org/hothaps-software
29 Kjellstrom T, Freyberg C, Lemke B, Otto M,
Briggs D. Estimating population heat expo-
sure and impacts on working people in con-
junction with climate change. Int J Biometeo-
rol. 2018 Mar; 62(3): 291–306.
30 Bröde P, Jendritzky G, Fiala D, Havenith G.
The universal thermal climate index UTCI in
operational use. In: Proceedings of Confer-
ence: Adapting to Change: New Thinking on
Comfort, Cumberland Lodge, Windsor, UK,
9-11 April 2010. London: Network for Com-
fort and Energy Use in Buildings; 2010. Avail-
able from: http://www.utci.org/isb/docu-
ments/windsor_vers05.pdf
31 Błażejczyk K, Baranowski J, Błażejczyk A.
Heat stress and occupational health and safe-
ty – spatial and temporal differentiation. Mis-
cellanea Geographica. 2014 Mar; 18(1): 61–67.
32 Gubernot DM, Anderson GB, Hunting KL.
Characterizing occupational heat-related
mortality in the United States, 2000-2010: an
analysis using the Census of Fatal Occupa-
tional Injuries database. Am J Ind Med. 2015
Feb; 58(2): 203–11.
33 Department of Hydrology and Meteorology
(DHM). Observed Climate Trend Analysis in
the Districts and Physiographic Zones of Ne-
pal (1971-2014). Kathmandu: Ministry of
Population and Environment; 2017.
34 Farajalla N. Climate Change and the Environ-
ment in the Arab World Program. Beirut,
Lebanon: Issam Fares Institute for Public Pol-
icy and International Affairs, American Uni-
versity of Beirut; 2017. Available from: http://
www.usp.br/nereus/wp-content/uploads/
Impact-of-Climate-Change-on-the-Arab-
World.pdf
35 Ministry of Population and Environment,
Government of Nepal. Synthesis of the Stock-
taking Report for the National Adaptation
Plan (NAP) Formulation Process in Nepal.
Kathmandu: Ministry of Population and En-
vironment (MoPE); 2017.
36 Ministry of Population and Environment,
Government of Nepal. Vulnerability and Risk
Assessment Framework and Indicators for
National Adaptation Plan (NAP) Formula-
tion Process in Nepal. Kathmandu: Ministry
of Population and Environment (MoPE);
2017.
37 Kjellstrom T, Lemke B, Otto M. Mapping oc-
cupational heat exposure and effects in South-
East Asia: ongoing time trends 1980-2011 and
future estimates to 2050. Ind Health. 2013;
51(1): 56–67.
38 National Institute for Occupational Safety
and Health (NIOSH). Criteria for a recom-
mended standard: occupational exposure to
heat and hot environments. DHHS (NIOSH)
Publication Number 2016-106. Cincinnati,
OH: National Institute for Occupational Safe-
ty and Health, US Department of Health and
Human Services, Centers for Disease Control
and Prevention; 2016.
39 Kjellstrom T. Impact of climate conditions on
occupational health and related economic
losses: A new feature of global and urban
health in the context of climate change. Asia
Pac J Public Health. 2016 Mar; 28(2 suppl):
28S–37S.
40 Kjellstrom T, Crowe J. Climate change, work-
place heat exposure, and occupational health
and productivity in Central America. Int J Oc-
cup Environ Health. 2011 Jul-Sep; 17(3): 270–
81.
41 Pradhan B, Shrestha S, Shrestha R, Prad-
hanang S, Kayastha B, Pradhan P. Assessing
climate change and heat stress responses in
the Tarai region of Nepal. Ind Health. 2013;
51(1): 101–12.
42 Yoshi PL. Chapter 6: Mortality levels and pat-
terns in Nepal. In: Government of Nepal, edi-
tor. Population Monograph of Nepal. Kath-
mandu: Government of Nepal, Central Bu-
reau of Statistics; 2014. pp. 127–40.
43 McMichael AJ. Standardized mortality ratios
and the “healthy worker effect”: scratching
beneath the surface. J Occup Med. 1976 Mar;
18(3): 165–8.
44 Naghavi M, Abojabir AA, Abbafati C, et al.;
GBD 2016 Causes of Death Collaborators.
Global, regional, and national age-sex specific
mortality for 264 causes of death, 1980-2016:
a systematic analysis for the Global Burden of
Disease Study 2016. Lancet. 2017 Sep;
390(10100): 1151–210.
45 Luginbuhl RC, Jackson LL, Castillo DN, Lor-
inger KA. Heat-related deaths among crop
workers – United States, 1992-2006. JAMA.
2008; 300: 1017–18.
46 Nybo L, Kjellstrom T, Bogataj LK, Flouris AD.
Global heating: attention is not enough; we
need acute and appropriate actions [Editori-
al]. Temperature (Austin). 2017 Jun; 4(3):
199–201.
47 Doward J. Qatar World Cup: 400 Nepalese
die on nation's building sites since bid won.
The Guardian. 15 Feb 2014. Available from:
https://www.theguardian.com/foot-
ball/2014/feb/16/qatar-world-cup-
400-deaths-nepalese
48 HRW. World Report 2017: Human Rights
Watch. 2017 [cited 2017 Mar 2]. Available
from: https://www.hrw.org/world-re-
port/2017/country-chapters/qatar.
49 ITUC. The Case against Qatar: Host of the
FIFA 2022 World Cup ITUC Special Report.
Doha: International Trade Union Confedera-
tion; 2014.
50 Kjellstrom T, McMichael AJ. Climate change
threats to population health and well-being:
the imperative of protective solutions that
will last. Glob Health Action. 2013 Apr; 6:
20816.
51 Senouci A, Al-Abbasi M, Eldin NN. Impact of
weather conditions on construction labour
productivity in Qatar. Middle East J Manage-
ment. 2018; 5(1): 34–49.
Downloaded by: D. Atar - 30355
172.16.6.162 - 7/15/2019 10:34:24 AM
... However, such measures are costly and are not easily applied in many occupations where environmental conditions cannot be controlled (e.g., firefighting, construction, agriculture, and military work). A few reports of heat mortality in working populations show the risks occurring in agriculture in the USA (Centers for Disease Control and Prevention 2008) and in construction in Qatar (Pradhan et al. 2019). ...
... Another worker category with extreme heat exposure in heavy labor situations is migrant construction work in Qatar and other Middle East countries. During the hot summer months, hundreds of migrant workers from Nepal have died due to heart disease, and the most likely reason is that they continue heavy labor even during the hottest parts of the year (Pradhan et al. 2019). The work processes during each day may have been organized so that protective self-pacing was not possible. ...
... The institutionalization of racialized or ethnic hierarchies in labor, supposed heat tolerance and heat exposure in contemporary contexts, should be assumed to be limited to history. Recent examples are the fatal heat effects on migrant agricultural workers in the USA (Centers for Disease Control and Prevention 2008) and on migrant construction workers in Qatar (Pradhan et al. 2019). ...
Chapter
Workplace heat is an important occupational health hazard. It has attracted new attention in recent years due to ongoing climate change and projections of future increases of heat in most parts of the world. This chapter provides an overview of the physiological basis for this occupational health hazard and related serious health and social effects that may develop. While outdoor jobs in the sun create particular risks, many millions of workers in factories in tropical areas are also exposed to excessive heat because effective air-conditioning cooling systems are not installed. Excessive heat exposure in workplaces can cause heat exhaustion and heat stroke unless the worker is able to take action to reduce thermal strain, such as by reducing work intensity or taking frequent breaks. These protective actions reduce health risk and affect hourly productivity and the economic output from the work done. The social and economic factors that contribute to health risks include social norms and attitudes concerning basic low-skill work that is particularly risky in hot situations. Gender-based employment also has implications for occupational heat-health risk given sex-based differences in vulnerability to heat. For instance, some physically intensive jobs are traditionally very male-focused, and mass production garment works in hot factories of tropical areas are very female-focused. In some ways women are more sensitive to heat, and pregnancy is a period of particular heat exposure risks. The workforce in many countries is ageing, and older people are more vulnerable to heat than younger people. Another risk group is migrant workers who often are provided with little occupational health protection. The increased risk of health impacts also has important social and economic impacts, such as reduced daily income, when heat slows work output. At the community level, the increasing heat due to climate change can also undermine traditional customs and degrade social well-being. Our analysis indicates the need to develop policies that limit the ongoing heat increase due to climate change and to implement protection in situations of excessive heat.
... 8 Large-scale epidemiological studies have shown that most heatinduced deaths are due to cardiovascular reasons, [9][10][11] a case that is also true for workers who perform their job in hot environments. 12 One measure that can shed some light on this situation is heart rate variability (HRV), which is an established noninvasive indicator of parasympathetic and sympathetic cardiac autonomic modulation. [13][14][15] Assessing HRV in individuals performing physical work is important, especially for older workers who are among the most vulnerable population groups because of their impaired capacity to dissipate heat [16][17][18][19] and their attenuated HRV at rest and during exercise. ...
Article
Background The Threshold Limit Values (TLV) of the American Conference of Governmental and Industrial Hygienists indicate the levels of heat stress that all workers may be repeatedly exposed to without adverse health effects. In this study, we evaluated heart rate variability (HRV) during moderate‐to‐heavy work performed continuously or according to different TLV work‐rest (WR) allocations in healthy physically active older workers. Methods Nine healthy older (58 ± 5 years) males performed three different 120‐minute conditions in accordance with TLV guidelines for moderate‐to‐heavy intensity work (360 W fixed rate of heat production) in different wet‐bulb globe temperatures (WBGT): continuous cycling at 28°C WBGT (CON), as well as intermitted work performed at WR of 3:1 in 29°C WBGT (WR3:1), and at WR of 1:1 at 30°C (WR1:1). Rectal temperature and HRV (3‐lead electrocardiogram [ECG]) were assessed throughout. Results Coefficient of Variation, Poincaré SD2, and Shannon Entropy were decreased during the CON compared with the WR3:1 when core temperature exceeded 38°C and after 1 hour of continuous work (P < .05). Also, 4 of the 12 HRV indices studied were reduced at CON compared with WR1:1 after 2 hours of accumulated work time (P < .05). Participants worked longer before core temperature reached 38°C during the WR1:1 and the WR3:1, compared with CON (P < .05). Conclusions Incorporating breaks during moderate‐to‐heavy work in the heat for older adults can reduce autonomic stress and prolong the work performed at safe core temperature levels. The TLV WR1:1 provides increased cardiac protection for older workers, as compared with the CON and the WR3:1.
... For example, a study of Nepali migrant workers employed in construction in Qatar in 2009-17 documented deaths associated with Figure: Human (im) excessive heat exposure. 10 Most migrants worked in high temperatures (>31°C), with cardiovascular disease being the major cause of death. The study found that most deaths were probably due to serious heat stroke, with extreme heat due to climate change increasing health risks. ...
Article
Objectives: Assess the impact of summer heat exposure (June-September) on residential construction workers in Al-Ahsa, Saudi Arabia by evaluating (i) heart rate (HR) responses, hydration status, and physical workload among workers in indoor and outdoor construction settings, (ii) factors related to physiological responses to work in hot conditions, and (iii) how well wet-bulb globe temperature-based occupational exposure limits (WBGTOELs) predict measures of heat strain. Methods: Twenty-three construction workers (plasterers, tilers, and laborers) contributed 260 person-days of monitoring. Workload energy expenditure, HR, fluid intake, and pre- and postshift urine specific gravity (USG) were measured. Indoor and outdoor heat exposures (WBGT) were measured continuously and a WBGTOEL was calculated. The effects of heat exposure and workload on heart rate reserve (HRR), a measure of cardiovascular strain, were examined with linear mixed models. A metric called 'heat stress exceedance' (HSE) was constructed to summarize whether the environmental heat exposure (WBGT) exceeded the heat stress exposure limit (WBGTOEL). The sensitivity and specificity of the HSE as a predictor of cardiovascular strain (HRR ≥30%) were determined. Results: The WBGTOEL was exceeded frequently, on 63 person-days indoors (44%) and 91(78%) outdoors. High-risk HRR occurred on 26 and 36 person-days indoors and outdoors, respectively. The HSE metric showed higher sensitivity for HRR ≥30% outdoors (89%) than indoors (58%) and greater specificity indoors (59%) than outdoors (27%). Workload intensity was generally moderate, with light intensity work more common outdoors. The ability to self-pace work was associated with a lower frequency of HRR ≥30%. USG concentrations indicated that workers began and ended their shifts dehydrated (USG ≥1.020). Conclusions: Construction work where WBGTOEL is commonly exceeded poses health risks. The ability of workers to self-pace may help reduce risks.
Data
Full-text available
Volume 6 of an index of publications on thermology or temperature measurement
Article
The literature survey 2019 is based on 775 papers found in Scopus with the keywords "thermography" OR "infrared imaging" OR "thermology" OR "temperature measurement" OR "thermometry" AND "published in 2019" and restricted to "medicine". The final database was created from 643 articles after 211 badly matched hits were excluded and a total of 79 articles were added, namely publications, notes or abstracts discovered in the journal "Thermology international" or in the author's literature archive. The papers were analysed with respect to the origin of authors, the language and the publication source. Like in the surveys of previous years, a detailed description is provided of publications related to Raynaud's phenomenon, Complex Regional Pain Syndrome, Breast diseases, fever measurement and application in sports. Most of the publications on breast thermography continue to originate from Asia. These papers have their primary focus on image processing and artificial intelligence applications for the evaluation of breast thermograms
Article
Full-text available
Background: Monitoring levels and trends in premature mortality is crucial to understanding how societies can address prominent sources of early death. The Global Burden of Disease 2016 Study (GBD 2016) provides a comprehensive assessment of cause-specific mortality for 264 causes in 195 locations from 1980 to 2016. This assessment includes evaluation of the expected epidemiological transition with changes in development and where local patterns deviate from these trends. Methods: We estimated cause-specific deaths and years of life lost (YLLs) by age, sex, geography, and year. YLLs were calculated from the sum of each death multiplied by the standard life expectancy at each age. We used the GBD cause of death database composed of: vital registration (VR) data corrected for under-registration and garbage coding; national and subnational verbal autopsy (VA) studies corrected for garbage coding; and other sources including surveys and surveillance systems for specific causes such as maternal mortality. To facilitate assessment of quality, we reported on the fraction of deaths assigned to GBD Level 1 or Level 2 causes that cannot be underlying causes of death (major garbage codes) by location and year. Based on completeness, garbage coding, cause list detail, and time periods covered, we provided an overall data quality rating for each location with scores ranging from 0 stars (worst) to 5 stars (best). We used robust statistical methods including the Cause of Death Ensemble model (CODEm) to generate estimates for each location, year, age, and sex. We assessed observed and expected levels and trends of cause-specific deaths in relation to the Socio-demographic Index (SDI), a summary indicator derived from measures of average income per capita, educational attainment, and total fertility, with locations grouped into quintiles by SDI. Relative to GBD 2015, we expanded the GBD cause hierarchy by 18 causes of death for GBD 2016. Findings: The quality of available data varied by location. Data quality in 25 countries rated in the highest category (5 stars), while 48, 30, 21, and 44 countries were rated at each of the succeeding data quality levels. Vital registration or verbal autopsy data were not available in 27 countries, resulting in the assignment of a zero value for data quality. Deaths from non-communicable diseases (NCDs) represented 72·3% (95% uncertainty interval [UI] 71·2–73·2) of deaths in 2016 with 19·3% (18·5–20·4) of deaths in that year occurring from communicable, maternal, neonatal, and nutritional (CMNN) diseases and a further 8·43% (8·00–8·67) from injuries. Although age-standardised rates of death from NCDs decreased globally between 2006 and 2016, total numbers of these deaths increased; both numbers and age-standardised rates of death from CMNN causes decreased in the decade 2006–16—age-standardised rates of deaths from injuries decreased but total numbers varied little. In 2016, the three leading global causes of death in children under-5 were lower respiratory infections, neonatal preterm birth complications, and neonatal encephalopathy due to birth asphyxia and trauma, combined resulting in 1·80 million deaths (95% UI 1·59 million to 1·89 million). Between 1990 and 2016, a profound shift toward deaths at older ages occurred with a 178% (95% UI 176–181) increase in deaths in ages 90–94 years and a 210% (208–212) increase in deaths older than age 95 years. The ten leading causes by rates of age-standardised YLL significantly decreased from 2006 to 2016 (median annualised rate of change was a decrease of 2·89%); the median annualised rate of change for all other causes was lower (a decrease of 1·59%) during the same interval. Globally, the five leading causes of total YLLs in 2016 were cardiovascular diseases; diarrhoea, lower respiratory infections, and other common infectious diseases; neoplasms; neonatal disorders; and HIV/AIDS and tuberculosis. At a finer level of disaggregation within cause groupings, the ten leading causes of total YLLs in 2016 were ischaemic heart disease, cerebrovascular disease, lower respiratory infections, diarrhoeal diseases, road injuries, malaria, neonatal preterm birth complications, HIV/AIDS, chronic obstructive pulmonary disease, and neonatal encephalopathy due to birth asphyxia and trauma. Ischaemic heart disease was the leading cause of total YLLs in 113 countries for men and 97 countries for women. Comparisons of observed levels of YLLs by countries, relative to the level of YLLs expected on the basis of SDI alone, highlighted distinct regional patterns including the greater than expected level of YLLs from malaria and from HIV/AIDS across sub-Saharan Africa; diabetes mellitus, especially in Oceania; interpersonal violence, notably within Latin America and the Caribbean; and cardiomyopathy and myocarditis, particularly in eastern and central Europe. The level of YLLs from ischaemic heart disease was less than expected in 117 of 195 locations. Other leading causes of YLLs for which YLLs were notably lower than expected included neonatal preterm birth complications in many locations in both south Asia and southeast Asia, and cerebrovascular disease in western Europe. Interpretation: The past 37 years have featured declining rates of communicable, maternal, neonatal, and nutritional diseases across all quintiles of SDI, with faster than expected gains for many locations relative to their SDI. A global shift towards deaths at older ages suggests success in reducing many causes of early death. YLLs have increased globally for causes such as diabetes mellitus or some neoplasms, and in some locations for causes such as drug use disorders, and conflict and terrorism. Increasing levels of YLLs might reflect outcomes from conditions that required high levels of care but for which effective treatments remain elusive, potentially increasing costs to health systems.
Article
Full-text available
Diurnal temperature range (DTR) is an important meteorological indicator associated with global climate change, and has been linked with mortality and morbidity in previous studies. To date, however, little evidence has been available regarding the association of DTR with years of life lost (YLL). This study aimed to evaluate the DTR-related burden on both YLL and mortality. We collected individual records of all registered deaths and daily meteorological data in Wuhan, central China, between 2009 and 2012. For the whole population, every 1 • C increase in DTR at a lag of 0–1 days was associated with an increase of 0.65% (95% CI: 0.08–1.23) and 1.42 years (−0.88–3.72) for mortality and YLL due to non-accidental deaths, respectively. Relatively stronger DTR-mortality/YLL associations were found for cardiovascular deaths. Subgroup analyses (stratified by gender, age, and education level) showed that females, the elderly (75+ years old), and those with higher education attainment (7+ years) suffered more significantly from both increased YLL and mortality due to large DTR. Our study added additional evidence that short-term exposure to large DTR was associated with increased burden of premature death using both mortality incidence and YLL.
Article
Increased environmental heat levels as a result of climate change present a major challenge to the health, wellbeing and sustainability of human communities in already hot parts of this planet. This challenge has many facets from direct clinical health effects of daily heat exposure to indirect effects related to poor air quality, poor access to safe drinking water, poor access to nutritious and safe food and inadequate protection from disease vectors and environmental toxic chemicals. The increasing environmental heat is a threat to environmental sustainability. In addition, social conditions can be undermined by the negative effects of increased heat on daily work and life activities and on local cultural practices. The methodology we describe can be used to produce quantitative estimates of the impacts of climate change on work activities in countries and local communities. We show in maps the increasing heat exposures in the shade expressed as the occupational heat stress index Wet Bulb Globe Temperature. Some tropical and sub-tropical areas already experience serious heat stress, and the continuing heating will substantially reduce work capacity and labour productivity in widening parts of the world. Southern parts of Europe and the USA will also be affected. Even the lowest target for climate change (average global temperature change = 1.5 °C at representative concentration pathway (RCP2.6) will increase the loss of daylight work hour output due to heat in many tropical areas from less than 2% now up to more than 6% at the end of the century. A global temperature change of 2.7 °C (at RCP6.0) will double this annual heat impact on work in such areas. Calculations of this type of heat impact at country level show that in the USA, the loss of work capacity in moderate level work in the shade will increase from 0.17% now to more than 1.3% at the end of the century based on the 2.7 °C temperature change. The impact is naturally mainly occurring in the southern hotter areas. In China, the heat impact will increase from 0.3 to 2%, and in India, from 2 to 8%. Especially affected countries, such as Cambodia, may have losses going beyond 10%, while countries with most of the population at high cooler altitude, such as Ethiopia, may experience much lower losses.
Article
Although existing studies have linked high temperature to mortality in a small number of regions, less evidence is available on the variation in the associations between high temperature exposure and cause-specific mortality of multiple regions in China. Our study focused on the use of time series analysis to quantify the association between high temperature and different cause-specific mortalities for susceptible populations for 43 counties in China. Two-stage analyses adopting a distributed lag non-linear model (DLNM) and a meta-analysis allowed us to obtain county-specific estimates and national-scale pooled estimates of the nonlinear temperature-mortality relationship. We also considered different populations stratified by age and sex, causes of death, absolute and relative temperature patterns, and potential confounding from air pollutants. All of the observed cause-specific mortalities are significantly associated with higher temperature. The estimated effects of high temperature on mortality varied by spatial distribution and temperature patterns. Compared with the 90th percentile temperature, the overall relative risk (RR) at the 99th percentile temperature for non-accidental mortality is 1.105 (95%CI: 1.089, 1.122), for circulatory disease is 1.107 (95%CI: 1.081, 1.133), for respiratory disease is 1.095 (95%CI: 1.050, 1.142), for coronary heart disease is 1.073 (95%CI: 1.047, 1.099), for acute myocardial infarction is 1.072 (95%CI: 1.042, 1.104), and for stroke is 1.095 (95%CI: 1.052, 1.138). Based on our findings, we believe that heat-related health effect in China is a significant issue that requires more attention and allocation of existing resources.
Article
Cardiovascular disease (CVD) follows a seasonal pattern in many populations. Broadly defined winter peaks and clusters of all subtypes of CVD after 'cold snaps' are consistently described, with corollary peaks linked to heat waves. Individuals living in milder climates might be more vulnerable to seasonality. Although seasonal variation in CVD is largely driven by predictable changes in weather conditions, a complex interaction between ambient environmental conditions and the individual is evident. Behavioural and physiological responses to seasonal change modulate susceptibility to cardiovascular seasonality. The heterogeneity in environmental conditions and population dynamics across the globe means that a definitive study of this complex phenomenon is unlikely. However, given the size of the problem and a range of possible targets to reduce seasonal provocation of CVD in vulnerable individuals, scope exists for both greater recognition of the problem and application of multifaceted interventions to attenuate its effects. In this Review, we identify the physiological and environmental factors that contribute to seasonality in nearly all forms of CVD, highlight findings from large-scale population studies of this phenomenon across the globe, and describe the potential strategies that might attenuate peaks in cardiovascular events during cold and hot periods of the year.
Article
Full-text available
Background Although many studies have examined the effects of heat waves on the excess mortality risk (ER) posed by cardiovascular disease (CVD), scant attention has been paid to the effects of various combinations of differing heat wave temperatures and durations. We investigated such effects in Beijing, a city of over 20 million residents. MethodsA generalized additive model (GAM) was used to analyze the ER of consecutive days’ exposure to extreme high temperatures. ResultsA key finding was that when extremely high temperatures occur continuously, at varying temperature thresholds and durations, the adverse effects on CVD mortality vary significantly. The longer the heat wave lasts, the greater the mortality risk is. When the daily maximum temperature exceeded 35 °C from the fourth day onward, the ER attributed to consecutive days’ high temperature exposure saw an increase to about 10% (p < 0.05), and at the fifth day, the ER even reached 51%. For the thresholds of 32 °C, 33 °C, and 34 °C, from the fifth day onward, the ER also rose sharply (16, 29, and 31%, respectively; p < 0.05). In addition, extreme high temperatures appeared to contribute to a higher proportion of CVD deaths among elderly persons, females and outdoor workers. When the daily maximum temperature was higher than 33 °C from the tenth consecutive day onward, the ER of CVD death among these groups was 94, 104 and 149%, respectively (p < 0.05), which is considerably higher than the ER for the overall population (87%; p < 0.05). Conclusions The results of this study may assist governments in setting standards for heat waves, creating more accurate heat alerts, and taking measures to prevent or reduce temperature-related deaths, especially against the backdrop of global warming.
Article
Background: The Deepwater Horizon disaster cleanup effort provided an opportunity to examine the effects of ambient thermal conditions on exertional heat illness (EHI) and acute injury (AI). Methods: The outcomes were daily person-based frequencies of EHI and AI. Exposures were maximum estimated WBGT (WBGTmax) and severity. Previous day's cumulative effect was assessed by introducing previous day's WBGTmax into the model. Results: EHI and AI were higher in workers exposed above a WBGTmax of 20°C (RR 1.40 and RR 1.06/°C, respectively). Exposures above 28°C-WBGTmax on the day of the EHI and/or the day before were associated with higher risk of EHI due to an interaction between previous day's environmental conditions and the current day (RRs from 1.0-10.4). Conclusions: The risk for EHI and AI were higher with increasing WBGTmax. There was evidence of a cumulative effect from the prior day's WBGTmax for EHI. Am. J. Ind. Med. © 2016 Wiley Periodicals, Inc.