Health and Environment International Trust
Mapua, New Zealandemail: kjellstromt@yahoo.com
HEIT

Guidance document for ClimateCHIP.org website and the
Workplace Heat Effects Assessment Tool (WorkHeat)

PREPARED for HEIT, Mapua, New Zealandhttps://ClimateCHIP.org/health-and-environment-international-trust
by Prof. Tord Kjellstrom

October 2023

1

Table of contents
Section
1
2

Heading
Short introduction
Heat effects on working
people and productivity

3

Short overview ofwebsite, ClimateCHIP

4

Location of interest,
Current heat data

5

Current heat risks forhealth and productivity

6

Future heat data

7

Future heat risks

8

Workplace Heat Effects
Assessment Tool
Current heat impact
prevention approaches

910Importance of climatechange mitigation

11

Conclusion, decisions tomakeReferences and further
reading
Appendix User survey form

Content
Why does heat matter for investment plans?
Heat and workplace considerations in acompany perspective; examples fromdifferent sectors
How to best use the various options
available; how to download data of interestand use in analysis and reports
Local TODAY data in grid cell and fromweather stations; role of Urban Heat Island in
modifying data; factors within the workplacethat modifies data within different sectors
Heat risks at the current heat levels;
information materials for employees andmanagement; reference to key publications
with more information
TOMORROW data for grid cell; different
trends depending on climate change
mitigation actions at country level
Heat risks at future heat levels; Impact of
future trends in workforce distribution andtechnologies applied
Rapid testing of key effects of workplace heaton health and productivity
Description of different approaches at sector
level; scheduling intensive work away fromhot periods; local cooling approaches andPersonal Protective Equipment;
Checklist of actions to consider.
Highlighting the overall problem ofgreenhouse gas emissions and methods toreduce the emissions; benefits forenterprises in slower and lower climatechangeSummary of heat risks for this enterprise inthis location, and a listing of recommended
preventive actions; Checklist for Due
Diligence on the heat issue

12

Possibility to provide feedback comments2

1. Short introduction
Workplace heat is a well-known occupational health hazard affecting working people
in many ways (Parsons, 2014; Kjellstrom et al., 2016). The health risks areassociated with the need for the human body to maintain a core body temperature(CBT) close to 37C. If the CBT increases above 39C serious heat stroke may occur
and some people will die. Working people are at particular risk as physical work
contributes to the body heat (See Section 2 for more details on health effects).
Climate change, also called global heating, creates increasing challenges to protect
working people from heat (Kjellstrom et al., 2009). The ClimateCHIP.org website andthe Workplace Heat Effects Assessment Tool (WorkHeat) aim to provide importantdata and advice for those planning or managing the reduction and prevention ofhealth risks in potentially hot locations. The website is a unique resource for local
climate data anywhere in the world as it includes data on heat stress indices that canbe interpreted for prevention of effects of heat on health and productivity. The userfriendly analysis, advice and interpretation guidelines makes it possible for amanager, planner or investor to find ways to protect workers from heat effects and to
reduce the risk of heat induced productivity and economic losses.
The areas of the world of particular concern are indicated in the global heat map(Figure 1). In the yellow, red or brown areas, more than 100 days each year are hot
enough to create serious heat problems for working people. However, even in thegreen areas a limited number of “heat wave” days can also cause heat challenges.
ClimateCHIP provides access to heat data for any part of the world from 1981 to
2099. WBGT (Wet Bulb Globe Temperature, described in Section 2) is a special heatindex designed for use in workplace monitoring (as recommended by NIOSH, 2016).
Figure 1. Number of hot days per year with WBGTmax > 26C, 1995

This map is based on heat estimates from 68,000 grid cells (0.5 x 0.5 land degrees)that cover the whole world’s landmass.
2. Heat effects on working people and productivity
Workplace heat has been known to be an important occupational health hazard
for more than a century. The basis for the threats to health stem from the basic
human physiology concerning heat exposure. Humans need to maintain a core body3

temperature (CBT) close to 37C. If the CBT goes just 2 -4 degrees C higher, serious
heat stroke or even death may occur (Parsons, 2014). Serious health effects canalso occur if the body cools by a few degrees below 37C.
In recent years increased scientific attention to the problems of workplace heat
has led to a better understanding of the variety of health effects that may occur andto adverse effects on productivity effects. Table 1 lists specific health effects reported
in documents from WHO and IPCC. (Detailed listings of references are not shown inthis short guidance document).
The main problem for working people is effects on the heart. I For example,
hundreds of migrant workers died during the first years of the major construction
work for the 2022 football World Cup in Qatar (see:https://karger.com/crd/article/143/1-2/37/97107/Heat-Stress-Impacts-on-CardiacMortality-in-Nepali).
Another major health threat occurs in work situations where workers sweat
profusely, and become dehydrated causes serious chronic kidney disease (see:https://laislanetwork.org/).
Table 1. Climate change related health impacts of heat according to IPCC,
WHO and other sources (modified from Kjellstrom et al, 2016)
Hazardexposure
Intense heat

Health impact
Heat stroke
death

Confidence of this
impactVery highHeat stroke
Very highmorbidity
HeatHigh
exhaustion,Work capacity
loss
ForcedUnder-nutrition;Highmigration
infections;mental stress;
injuries
Health concerns not detailed in the IPCC or WHO reports
Intense heat Chronic kidney disease linked to dehydration
Increased incidence of violent crimes
Increased incidence of suicides
Teratogenic effects of high body temperature inpregnant women; damage to development offeatus brain
Interactions with prescription drugs
Deteriorated clinical status in chronic
Non-Communicable Diseases
Increased damage due to head trauma

Specific effects atorgan level
Heart strain; Central
Nervous System (CNS)
malfunction; dehydration
Heart strain; CNS
malfunction; dehydration
Heart strain; mental
fatigue

Sources

IPCC andWHO reports(before 2016)

Work capacity loss,
heart disease, fatigue

References in Kjellstrom et al., 20164

In order to maintain the CBT at a healthy level the human body reacts to the airtemperature outside the body (or water temperature when immersed in water) byadjusting blood flow to the skin and different organs. When the air in the workplace ishigher than the body temperature (or skin temperature at 33C), heat will betransferred to the body in accordance with the basic laws of physics, which include:
Conduction and Convection – direct transfer between body surface andsurrounding material touching the skin (convection = due to moving air or water).
Radiation – heat rays from the body or on the body (outdoors usually from sun)
Evaporation – When sweat evaporates, heat is released from the body surface
The net effect of these transfers results in storage or loss of heat in the body anda change in core body temperature. The focus here is on the ways a body interacts
with hot air around it, the most common work situation.
An important factor is the generation of heat inside the body when muscles areused. This is the greatest contributor to heat stress in many situations. Only 20% of
the energy created inside the body, from food digestion and other metabolicmechanisms, actually creates work by the muscles with as much as 80% of thisenergy released inside the body as heat. This is why someone carrying out intensive
work or sports activity still feels hot even in cooler air than 33C. The interpretation of
the health risk of external heat data needs to include an estimate of the work
intensity of the job (the Metabolic Rate, MR). Light work has an MR at about 200W.
Moderate intensity work MR is about 300W, and heavy labour MR is about 400W.
The most effective way to transfer heat from the body to surrounding air is by theevaporation of sweat from the skin. The air humidity is a very important factor
contributing to heat stress when working. If air relative humidity (RH) is 100% (mistconditions), then no sweat will evaporate and cooling will not take place. Conversely,
in a very dry situation with RH at 20%, sweat will rapidly evaporate and reduce
stored heat.
Heat stress indicesHeat indices combine both temperature and humidity so they are the best
variables for assessing heat risk in workplaces. Occupational health and productivity
assessments most often use the index WBGT (Wet Bulb Globe Temperature)developed in the 1950s by the US army to protect soldiers in training from severe
heat stress effects (Parsons, 2014). Heat protection standards and guidelines with
WBGT as a base are available for use in assessments of current and future heatchallenges (e.g. NIOSH, 2016). Other heat stress indices are sometimes used inreports (e.g. the Universal Thermal Climate Index UTCI, the US Heat Index, or the
Canadian Humidex), but WBGT includes all aspects of heat and is most widely usedin workplaces.
The future heat estimates shown on ClimateCHIP.org website, and those used in
the Workplace Heat Effects Assessment Tool (WorkHeat), are based oninternationally acknowledged ISIMIP3b data from the Potsdam Institute, Germany.
Data for two of the “pathways” for future global green-house gas emissions, SSP126
and SSP370 are used in ClimateCHIP. These Shared Socioeconomic Pathways(SSPs) include assumptions about climate change mitigation (prevention) policies,5with SSP1 the most protective and SSP3 fitting with current green-house gas
emission policies and trends. SSP1 is linked to Representative Concentration
Pathway RCP2.6 with radiative forcing from green-house gases at 2.6 W/m2, and
SSP3 to an RCP at 7.0 W/m2, which will lead to continuing increase of the global
mean temperature beyond 1.5C.
Different climate models are available for each SSP pathway. For WorkHeat we
use the midpoint of two models that span the range of different model results. Thesemodels are GFDL from the USA and UKesm from the United Kingdom. The range
between results is usually rather narrow, so the midpoint of these two models is a
simpler way of showing likely future heat levels. (The abbreviations in the preceding
two paragraphs are included when relevant in the following text: SSP126, SSP370,
GFDL and UKesm).
It also is important to note that the time duration of a given heat level, (hourly, 24hour daily mean, weekly, monthly or annual), is an important feature of any heatestimate. Adverse effects on health and productivity occur quickly making hourly
data the most valuable for assessing impacts. Occupational health standards andguidelines apply to hourly values. When heat levels vary widely within an hour, andextremely hot short periods occur, it is these short periods (seconds or minutes) thatare likely to be the most dangerous in certain occupations, (e.g. fire fighters).

6

3. Short overview of website, ClimateCHIP
This website was created by the HEIT team (Health and Environment
International Trust) in New Zealand (https://ClimateCHIP.org/health-andenvironment-international-trust ). It was initiated over 10 years ago and has been
updated with the latest internationally approved climate modelling data in 2023. The
website has a “Your Area” page where data for geographic spatial grid cells arepresented. The features of the website are listed in Box 1, and on the website itself
there are brief descriptions of the data and what can be produced as outputs.
➔ Please, spend a few minutes to familiarize yourself with the material on
the website.
Box 1. Features of the “Your Area” pages of the Website ClimateCHIP.org
Map features
Climate data are shown for map areas and locations using Google Earth maps
The map and climate data graphics for one initial variable is shown on the screen
On the map one can choose “Map” or “Satellite” to either see map features or satellite
photo details of the location. The latter can be used to judge urbanisation in this locationand to find the exact place of a planned activity.
Location specifications
Spatial rectangular grid cell data; 0.5 x 0.5 degrees (appr.56 x 56 km at the Equator, 30 x
56 km at 40 degrees North, e.g. New York, or South, e.g. Wellington)
A total of approximately 68,000 grid cells over land, where the land proportion of the gridcell area is more than 10%. Most grid cells are 100% over land.
Weather station data from approximately 5,000 stations where more than 90% of the daily
data from 1980 are available
Time periods; Two time periods for data:“Today” = 1981 to 2021, monthly data for each year
“Tomorrow” = 1980s to 2090s, monthly mean data for each decade
Climate variables available
Monthly means of daily data on maximum, mean and minimum Temperature
Mean daily Relative Humidity (RH), RH at maximum Temperature and Dew-pointtemperature which indicates the “absolute humidity”
Monthly means of three daily heat levels (max, mean and min) of three heat indices(WBGT, UTCI and HI), values in the shade (and in sun for WBGTmax)
Time trend graphics“Today” graphics next to the map show annual or monthly estimates of mean grid cellvalues for selected climate variables, each year from 1981 to 2021
The map shows weather station locations and a click brings up similar data reported fromthe chosen weather station“Tomorrow” graphics next to the same map show decadal estimates of mean annual ormonthly grid cell values; same variables as for Today.
The graphics and underlying data can be downloaded into Excel for further use by any
website user
“WorkHeat” graphics show monthly number of days hot enough to require heat prevention
actions (unsafe work days) and the likely productivity loss if work is carried out in heat.
Other information
The Workplace Heat Effects Assessment Tool is available in “Assessment Options”
Heat data analysis tools and quality testing reports
Guidance for occupational epidemiology studies of heat effects on working people
HEIT reports and individual country data7

4. Location of interest and current heat data
➔ Go to the location of interest on the website map (see Box 2).
Box 2. Steps in finding local climate information at location of interest
1. Choose location using name of area, town or another feature
2. Type this into the “Search” field inside “Your Area, Today”
3. The area of interest should now appear; Zoom in or out until you see that location ofinterest. You can also get to the location by moving cursor over map, or moving the map.
The + and – in the corner can be used to expand or reduce the map scale.
4. You can now choose to see values and time trends 1981-2021 for any of the climate
variables listed under “Parameter”
5. The values can be presented on Celsius or Fahrenheit scale, see “Temperature Unit”
6. Values can be shown for any calendar month, annual average or monthly distribution; see“Chart Type”
7. The “Monthly Distribution” is the best to start with, as it shows which month is the hottest
and the heat levels reached. These values are the means for the period 1981-2021•

Note that the scale of the output graphics varies so that lowest and highest numbers fit in.
Therefore, the visual slopes of fitted time trends are not directly comparable for different
parameters and locations.

If you have already used the Workplace Heat Effects Assessment Tool on
ClimateCHIP, a map and graph has been preselected to show the current and future
WBGT values for the chosen location. This is in the Tomorrow section of the website
data.
Figure 2 shows an example of Your Area Today for the grid cell containing most of
the city of Hyderabad, India. The grid cell includes data from the central and westernparts of Hyderabad and the weather station at the airport.
➔ Example: Find the Hyderabad grid cell in India and its airport weather
station Begumpet
The figure 2 graphic shows Tmax, RHmean, and WBGTmax, averages for 19812021. The hottest month is May with an average Tmax at 40C, while the coolest
months are December and January with Tmax close to 30C. Tmax occurs in theearly afternoon, the 24-hour mean temperature is 33C in May and night-time Tmin is
26C, (shown by clicking on these parameters). March to May is a dry pre-monsoon
period with RHmean at 40%, while the peak monsoon period (July, August) has
RHmean in the range 72-75%.
Figure 2 also shows that WBGTmax occurs in the same month as Tmax (May) andhas reached 30C, exceeding the safety guidelines available (see below). From
March to September the monthly WBGTmax values are on average above 26C, avalue that requires workers to be protected from heat.
The hatched curves on the graphic shows the values for the grid cell and thecontinuous lines are data from the weather station. The mean values for the grid celland the weather station are very similar for each month, which indicates that in thislocation the grid cell values represent locally measured heat values, i.e. good data8

quality. By clicking on each month, the time trends are different with the highest in
November for the weather station: Tmax increasing 0.59C per decade and WBGT
increasing 0.43C per decade. In May, the hottest month, the values increase more
slowly, 0.29C and 0.30C per decade, respectively.
The key issue for worker safety and productivity is the WBGT level. The afternoon
value (WBGTmax) in the shade for the grid cell area reaches appr. 22C in January,
24C in February and 26C in March. In the sun during the afternoons these
WBGTmax values are approximately 2C higher. This means that actions for heatprotection are required for most of the year in Hyderabad. In case another heatstress index is preferred for the analysis, UTCI and HI estimates can also be foundamong the parameters on the website.
Figure 2. Monthly data for Hyderabad, India, in “Your Area Today”

The main way to assess heat risks for workers, carrying out work of varying
physical intensity, is to assess the WBGT values during different hours of a day. In
calculations of these impacts a simple short-cut to hourly data is to assume that theheat level during the four hottest hours (usually between 12 noon and 4 pm) is at thelevel of WBGTmax, and the heat level at the coolest four daylight hours (at dawn and9dusk) is at the WBGTmean for the day. Another four hours is likely to be close to the
midpoint of WBGTmax and WBGTmean. This is called the 4+4+4 method (Kjellstrom
et al., 2018).
➔ Example: Find the Managua grid cell in Nicaragua and the airport
weather station
The grid cell data in Today for Managua (Figure 3) show two peaks for the hottest
months of WBGTmax, April and August. Most months are similarly hot, except
November-December which have 2-3C lower values. The graphic also shows the
WBGTmax for people working in direct sunlight without effective shading or cooling.
Sun adds appr. 2-3C to these high heat values during the afternoon.
These are monthly mean values, so individual hot days will reach higher values.
In tropical regions like Managua, the daily variation is small with the hottest days just
1-2C higher than the monthly mean. The heat risk for working in the shade on typical
April days is based on estimates for WBGTmax at 28C and WBGTmean at 25C(Figure 3). The heat risk for working in the sun assumes a WBGTmax of 30.5C and
WBGTmean at 25C. (The risk calculation method is shown in Section 5 below).
If a WBGT above 26C is used as a simple threshold for heat levels that require
attention, it is clear that the climate in the grid cell at Managua will create heatproblems during almost the whole year. Clicking on data for April, the time trends
1981-2021 show increasing trends and WBGTmax has increased by 0.14C per
decade in this period. Clicking on Tomorrow then shows that the future trends are
expected to go up faster and WBGTmax in the shade may reach 29-30C by the endof the century. The recorded data from the weather station at Managua airport isvery close to the grid cell estimates (see on ClimateCHIP.org). Exact agreement isunlikely because the grid cell data is an average for an area, while the weather
station data measures at one point inside the grid cell.
Another feature that influences the heat risk in workplaces is the contribution of
the Urban Heat Island (UHI) effect to local heat (https://www.epa.gov/greeninfrastructure/reduce-urban-heat-island-effect). The additional heat exposure fromthe sun heats dark colour surfaces on the ground. This can add as much as 4-6C toTmax or 3-4C to WBGTmax (air temperatures). Precise estimates cannot easily bemade from grid cell-based data as this extra heat is so dependent on the local
features of roads, buildings, parks, etc. However, the maps in ClimateCHIP.org can
give an indication of potential UHI in the location of interest (Figure 4) using thesatellite picture features.
In the satellite picture version of the map (Figure 4) of the Managua area the rural
agricultural areas are green and the urban areas are grey. Zooming in closer with the“+ sign” eventually shows every street and building in this location. The likely current
and future heat levels can then be adjusted to the potential UHI in the exact locationof a workplace. If UHI is likely in a specific location inside this grid cell it means thatin April the WBGTmax, in the shade, should not be set at 28C (Figure 3 and 4), but
at 31.5C, 3.5C higher. In the sun the WBGTmax is another 2C higher (Figure 4).
WBGTmean will need additions in a similar way.

10

These values are all monthly mean data so the hottest days will of course be at
higher values. Daily data from weather stations are available and can be analysedwith the HothapsSoft database and software. As a rule of thumb for hot months intropical places, the three hottest days in a hot month are 1C higher than the monthly
mean. In temperate areas the three hottest days are 2C higher than the mean.
Figure 3. WBGT data for Managua, Nicaragua

11Figure 4. Managua grid cell area showing “Satellite” picture.

➔ Results of your view of data on the website:
a. Overall understanding of the heat situation within the grid cell of interestb. Knowledge of monthly heat distribution during a year in the period 2081-2021
c. Understanding of the additional heat from working in the sun or from UHI
d. Selection of WBGTmax and WBGTmean values to use in assessment of risks
for health and productivity impacts of heat
➔ You may wish to record WBGT values for different analysis:
Value selection

WBGTmax WBGTmean WBGTmax WBGTmean
Monthly values, degr.C
Hottest days, degr.C

Grid cell values, hottest
month
Grid cell values, coolest
monthWith additions of UHI
impactWeather station values……
12Additional analysis with weather station data is possible with the use of the
HothapsSoft database and software when a weather station is placed in the vicinityof the location of interest. This software has daily data on all routinely recorded
meteorological variables at more than 18,000 weather stations around the world.
Many stations have gaps in the data but more than 5,000 stations include data for atleast 90% of the days since 1980. (ClimateCHIP provides links to the software anddatabase).
Figure 5 shows an example of an output graphic from HothapsSoft. The
presentation of actual daily measurements makes it possible to estimate heat stresslevels on the hottest days. The data for each day in the period 1980-2022 can be
downloaded into Excel and used for epidemiological and other impact studies.
Figure 5. HothapsSoft output for the main weather station in Singapore.
Monthly WBGTmax data showing range of 50% of daily data (boxes), 80% of daily
data (whiskers) and the values outside the whisker range (decadal data; whichmeans appr. 300 days in each calendar month).

5. Current heat risks for health and productivity
The WBGT heat index combines temperature, humidity, air movement and heatradiation into one number that reflects the health and productivity risks for workers ina specific locality. A number of studies have reported on the risks for various effects,
summarized in Figure 6 (Kjellstrom et al., 2018). We used the cumulative normal
distribution function as a default for fitting curves to data based on the assumptionthat the curves should represent biological variation in heat sensitivity. We are
currently reviewing this assumption. The red curve is the international standard (ISO,2017), identical to the NIOSH (2016) guidelines in the USA. It shows therecommended reduction of hourly work time, for a person working at a moderateintensity of 300W metabolic rate, as the heat level rises. This is a method that can beused to prevent health effects from heat exposure at work. According to this13

guideline an hourly WBGT of 25C does not require a reduction of work time for workof moderate intensity.
Figure 7 shows further safety recommendations. There are three fitted curves forthe guideline values at 200W, 300W and 400W metabolic rates. By using the 10%
work time reduction points as limits for “safe work in heat”, we find that the limits are
26C at 400W, 28C at 300W and 30C at 200W. Therefore, we use WBGT at 26C as alimit for “unsafe work days in heat” in the website calculations for WorkHeat (seeSection 8 for an example).
The blue solid curves in Figure 6 and 7 show the fitted relationship to the
combination of the two detailed studies available (Wyndham, 1969, and Sahu et al.,2013). This shows the actual reduction of work output (productivity) for workers in
actual workplaces in underground gold mines and harvesting of rice fields, and it
indicates that these workers can sustain work output beyond the safety
recommendations for heat. Fifty % loss of work output occurs at WBGT = 34C inthese jobs (at appr. 300W intensity) while the safety recommendation for 50% rest is
at 30C. This difference highlights the “safety factor” included in the ISO and NIOSH
guidelines, aimed at protecting the workers most sensitive to heat while the solid
blue curve shows the output from the workers who could best cope with the heat atwork. The period of rest time required in the guidelines are shown in section 8.
Figure 6. Level of heat impact on working people, expressed as a percentage
of productivity loss (international standard = ISO; Wyndham and Sahu =available epidemiological data)

14

Figure 7. Recommended reduction of work time per hour, in percentage, hourrequired to protect against heat (ISO = international standard at three work
intensities; S-W = combined epidemiology data)

We can use this type of information to estimate how the health risks andproductivity loss are likely to increase at different hours of the day due to heat
exposure in workplaces. In the section of the website named “Workplace Heat
Effects Assessment Tool” (WorkHeat), you will find estimates of the number of days
per year or month that are “unsafe for work”, i.e. where WBGTmax is higher than thelimits for 200W at 30C, 300W at 28C and 400W at 26C). The outputs also include
estimates of the percentage lost productivity per year or month at the estimated heatlevels in the selected location.
Based on the heat data shown in the sections TODAY or TOMORROW on thewebsite, one can also calculate productivity loss for additional time periods. The
following three tables show the likely productivity loss during days with different
combinations of daily WBGTmax and WBGTmean. Table 2 shows the expected loss
for workers in intensive physical work at 400W (e.g. much of agriculture andconstruction). Table 3 shows loss in moderate physical work at 300W (e.g.
manufacturing), and Table 4 shows loss in light work at 200W (e.g. service and officework).
We can use the climate data on the website ClimateCHIP.org (expressed as
WBGTmax and WBGTmean) when planning a new workplace in a specific location.
The following tables show how an assessment of the future heat impacts on
productivity in any location can be made.
Productivity loss is just one way of quantifying effects. Health risks will occur if
workers are not protected by frequent rest breaks, access to clean drinking water, orby cooling systems that reduce the actual heat exposure. The climate data on thewebsite presents outdoor conditions in the sun or shade. The heat levels for“indoors” also applies to workshops and factories that don’t have surrounding walls
or air-cooling system because it is likely that the heat exposure will be at the samelevel as outdoors in the shade, or even higher if local heat sources exist, such as
dark metal (corrugated iron) roofs or heat emitting machinery.
15

Table 2. Estimated work output loss per day with different WBGTmax and
WBGTmean combinations for work at 400W (intensive physical work). X =mean cannot be higher than max.
Work-loss @400W
WBGTmax
WBGTmean
25
18
1.2%
19
1.2%
20
1.2%
21
1.6%
22
1.7%
23
2.3%
24
2.8%
25
3.6%
26
X
27
X
28
X
29
X
30
X
31
X
32
X
33
X

26
2.0%
2.0%
2.4%
2.5%
2.7%
3.3%
3.9%
4.8%
6.0%
X
X
X
X
X
X
X

27
3.2%
3.5%
3.7%
3.8%
4.1%
4.7%
5.4%
6.4%
7.7%
9.5%
X
X
X
X
X
X

28
5.1%
5.2%
5.4%
5.6%
5.9%
6.7%
7.4%
8.5%
9.9%
11.7%
14.2%
X
X
X
X
X

29
7.3%
7.4%
7.7%
8.0%
8.3%
9.1%
10.0%
11.1%
12.6%
14.6%
17.1%
20.2%
X
X
X
X

30
9.9%
10.2%
10.4%
10.8%
11.2%
12.1%
13.1%
14.3%
15.9%
18.1%
20.7%
23.9%
27.7%
X
X
X

31
13.0%
13.3%
13.6%
14.1%
14.6%
15.6%
16.7%
18.0%
19.8%
22.0%
24.7%
28.1%
31.9%
36.2%
X
X

32
16.4%
16.8%
17.2%
17.7%
18.3%
19.4%
20.6%
22.1%
23.9%
26.3%
29.1%
32.5%
36.5%
40.9%
45.6%
X

33
19.9%
20.4%
20.9%
21.5%
22.3%
23.5%
24.7%
26.3%
28.3%
30.7%
33.7%
37.2%
41.2%
45.6%
50.3%
55.1%

34
23.5%
24.0%
24.6%
25.3%
26.2%
27.5%
28.9%
30.6%
32.7%
35.2%
38.3%
41.8%
45.9%
50.3%
55.0%
59.8%

35
26.8%
27.4%
28.2%
29.0%
30.0%
31.4%
32.9%
34.7%
36.9%
39.5%
42.6%
46.2%
50.3%
54.7%
59.4%
64.1%

36
29.9%
30.6%
31.5%
32.4%
33.5%
35.1%
36.7%
38.6%
40.8%
43.5%
46.6%
50.3%
54.3%
58.8%
63.4%
68.0%

Table 3. Estimated work output loss per day with different WBGTmax and
WBGTmean combinations for work at 300W (moderate physical work). X =mean cannot be higher than max.
Work-loss @300W
WBGTmax
WBGTmean
25
18
0.5%
19
0.5%
20
0.5%
21
0.5%
22
0.5%
23
0.5%
24
0.9%
25
1.6%
26
X
27
X
28
X
29
X
30
X
31
X
32
X
33
X

26
1.0%
1.0%
1.0%
1.0%
1.0%
1.3%
1.5%
2.2%
2.9%
X
X
X
X
X
X
X

27
1.7%
1.7%
1.7%
1.7%
2.0%
2.2%
2.4%
3.2%
3.9%
5.0%
X
X
X
X
X
X

28
2.7%
2.7%
2.7%
3.1%
3.3%
3.5%
3.7%
4.5%
5.4%
6.6%
8.2%
X
X
X
X
X

29
4.3%
4.3%
4.6%
4.8%
5.0%
5.2%
5.5%
6.4%
7.4%
8.7%
10.4%
12.8%
X
X
X
X

30
6.3%
6.7%
6.8%
7.0%
7.2%
7.5%
7.9%
8.9%
10.0%
11.4%
13.3%
15.7%
18.8%
X
X
X

31
9.2%
9.3%
9.5%
9.8%
10.1%
10.5%
10.9%
12.1%
13.2%
14.7%
16.7%
19.3%
22.5%
26.4%
X
X

32
12.3%
12.5%
12.7%
13.0%
13.4%
13.9%
14.5%
15.7%
17.0%
18.6%
20.8%
23.5%
26.8%
30.8%
35.3%
X

33
15.7%
16.0%
16.3%
16.7%
17.2%
17.8%
18.4%
19.8%
21.2%
23.0%
25.2%
28.1%
31.5%
35.6%
40.1%
45.0%

34
19.3%
19.6%
20.0%
20.5%
21.1%
21.8%
22.6%
24.1%
25.6%
27.5%
29.9%
32.9%
36.4%
40.5%
45.1%
50.1%

35
22.9%
23.3%
23.8%
24.4%
25.1%
25.9%
26.8%
28.4%
30.1%
32.1%
34.6%
37.6%
41.3%
45.4%
50.1%
55.0%

36
26.2%
26.7%
27.3%
28.0%
28.8%
29.8%
30.9%
32.6%
34.3%
36.5%
39.1%
42.2%
45.9%
50.1%
54.7%
59.6%

16

Table 4. Estimated work output loss per day with different WBGTmax and
WBGTmean combinations for work at 200W (light physical work). X = meancannot be higher than max.
Work-loss @200W
WBGTmax
WBGTmean
25
18
0.0%
19
0.0%
20
0.0%
21
0.0%
22
0.0%
23
0.0%
24
0.0%
25
0.0%
26
X
27
X
28
X
29
X
30
X
31
X
32
X
33
X

26
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
X
X
X
X
X
X
X

27
0.5%
0.5%
0.5%
0.5%
0.5%
0.5%
0.5%
0.5%
0.9%
1.5%
X
X
X
X
X
X

28
0.9%
0.9%
0.9%
0.9%
0.9%
0.9%
0.9%
1.3%
1.5%
2.1%
2.8%
X
X
X
X
X

29
1.6%
1.6%
1.6%
1.6%
1.6%
1.6%
2.0%
2.1%
2.3%
3.1%
3.8%
4.9%
X
X
X
X

30
2.7%
2.7%
2.7%
2.7%
2.7%
3.1%
3.2%
3.4%
3.6%
4.4%
5.3%
6.4%
8.1%
X
X
X

31
4.2%
4.2%
4.2%
4.2%
4.6%
4.7%
4.9%
5.1%
5.4%
6.3%
7.2%
8.5%
10.2%
12.5%
X
X

32
6.2%
6.2%
6.2%
6.5%
6.7%
6.9%
7.1%
7.4%
7.8%
8.8%
9.8%
11.2%
13.0%
15.5%
18.5%
X

33
8.7%
8.7%
9.1%
9.2%
9.4%
9.6%
9.9%
10.3%
10.8%
11.9%
13.0%
14.5%
16.5%
19.0%
22.2%
26.1%

34
11.6%
12.0%
12.1%
12.3%
12.6%
12.9%
13.3%
13.7%
14.3%
15.5%
16.8%
18.4%
20.5%
23.2%
26.5%
30.4%

35
15.2%
15.4%
15.6%
15.8%
16.1%
16.5%
17.0%
17.6%
18.2%
19.6%
20.9%
22.7%
24.9%
27.7%
31.2%
35.2%

36
18.7%
18.9%
19.2%
19.5%
19.9%
20.3%
20.9%
21.6%
22.4%
23.9%
25.4%
27.2%
29.6%
32.5%
36.0%
40.1%

These tables can be used to analyse current heat impacts on working people
as well as typical impacts in the past. Weather forecasts include data that canbe converted to WBGT with an Excel formula on the website(www.ClimateCHIP.org).
6. Future heat data
Another feature of heat risk assessment based on the ClimateCHIP.org website,is the ability to estimate future trends of heat levels based on ISIMIP3b, theinternationally approved climate modelling data. Figure 8 shows the “Tomorrow” data
for WBGTmax in shade the “Tomorrow” data for WBGTmax in shade for Tamale,
Ghana. Clicking on “linear trend” in this grid cell also shows four 30-year averages
for the two GHG pathways, SSP126 and SSP370. The historic trend from 1981 to
2021 is also shown with a black striped line.
The historic trend and the future SSP126 trend are very similar in this grid cell but
this is not always the case. Climate modelling is not perfect, and the data aredesigned for estimations of global rather than local change. However, the data in
ClimateCHIP.org gives an indication of what may happen locally. Other factors, likeurbanization and related UHI, may become important factors that influence local heatlevels.
Figure 8 shows the differences in estimated future heat levels based on two models(UKesm and GFDL) and two pathways (SSP126 and SSP370). There isapproximately 1.5C difference at the end of the century (5% of the approximate
midpoint value at 30C) between the two models and between the two pathways. The
pathways are determined by current and future climate policies in countries aroundthe world, while the two models reflect the range of values produced by the use ofdifferent modelling based on the same pathways, i.e. the “error range” for theestimates can be the range between the models (approximately 2.5%).

17

Figure 8. Future trends of WBGTmax in shade in the gridcell for Tamale, Ghana (March data).

7. Future heat risks
When planning investments in workplaces in locations with hot periods, current heatproblems are only part of what considerations are needed. Many workplaces areintended to operate in a particular location for a number of years into the future.
Figure 8 shows that at this location in Ghana (in March), between 2025 and 2055 the
WBGTmax may increase by as much as 1.5C in the high results model (UKesm)
based on pathway SSP370. By 2085 there is another 1.5C increase. The website
ClimateCHIP.org provides data for each location that can be used to estimate future
heat impacts (see Tables 2 - 4).
In certain locations the current heat levels do not reach the risk levels described in
Section 5, but after some years the heat risk will become substantive. Future risk
analysis can provide information on the need for heat protection that may be easierand less costly to provide than after the workplace is established.
8. The Workplace Heat Effects Assessment Tool (HEAT)
This new feature of the website estimates the likely effects of heat exposure in local
workplaces in each grid cell. Two basic heat effects are included. The number of“Unsafe work days” per month or year in three time periods, is based on thenumber of days when WBGTmax (afternoon levels) exceed the safety limits
18

mentioned earlier (30C for 200W, 28C for 300W and 26C for 400W). Figure 9 shows
Dallas, USA, as an example. The orange curve shows the estimates for 2025 withevery day in July and August above the safety limit for 400W metabolic rate. The
number of unsafe days in other months will increase in the future. At the right of thegraphic is a box with guidance information for first time users of the site.
The WorkHeat tool also includes the parameter “Productivity loss”, an estimate of
the percent of monthly or yearly work output, lost due to heat-induced slow-down of
workers during daylight hours (Figure 10). In Dallas the current productivity loss inJuly is 18%. This is likely to increase to 36% by the end of this century (Figure 10).
This part of the website also includes a link to this Guidelines document and two listsof Safety Recommendations for actions at personal level or workplace level.
Figure 9. Unsafe work days per month in Dallas, USA.

Figure 10. Productivity loss per month in Dallas, USA.

19

9. Current heat impact prevention approaches
a. Reduction of heat levels at the workplace during the design phaseb. Provision of cooling systems at the workplacec. Provision of basic occupational health services and access to drinking water
d. Appropriate managerial decisions to protect workers such as monitoring heatlevels, and providing rest breaks
e. Clothing and personal protection equipment (PPE)f. Reduce heat with climate change mitigation
The first step in prevention of heat hazards at a workplace is relevant informationand guidance materials. One source is the Global Heat Health Information Network(GHHIN), a joint project between WMO and WHO (https://ghhin.org/). A detailed
description is also available in the NIOSH (2016) report. Advisory material from avariety of agencies can be found by searching for “heat protection in workplaces” inGoogle. The main issues are described below.
a. Workplace location and design
If a planned workplace involves building premises, heat problems can be reduced byplacing any structure in a position to avoid direct sunlight during the day. Trees thatshade parts of a building can significantly reduce indoor heat (and outdoors in theshade); these may be existing or new trees. A detailed analysis by the AsianDevelopment Bank has provided guidance in this context (ADB, 2022).
Any building should be suitably insulated in walls and ceilings. Roofs can be painted
white or designed as a green plant roof with plants which vastly reduce heatabsorption. (Dark coloured corrugated metal roofs on an uninsulated building are theworst from a heat protection viewpoint.) Roofs can be used to provide solar
electricity that can be used for production processes. Modern technologies can also
convert incoming solar energy on a roof directly to cooling of air in a building(https://en.wikipedia.org/wiki/Solar_air_conditioning).
b. Providing cooling systems and monitoring heat levels
The website data will give estimates of likely heat exposures in any grid cell location
around the world. However, the actual heat conditions vary inside each grid cell someasurements of heat levels at a worksite is an important source of information.
Low-cost data loggers (e.g. Hobo or Lascar) that can measure temperature andhumidity can be used for continuous monitoring of heat levels in any workplace.
Air conditioning systems can provide effective cooling for interior spaces but coolinglarge volumes of air in bigger buildings is difficult and expensive. In some workplaces
cool wind blowing on workers can be a solution. In outdoor jobs with a worker in a
tractor cab or other confined space, air conditioning can be applied inside that space.
An important consideration with air conditioning is the energy required to run thesystem and how this energy use adds to the GHG emissions from the enterprise.
Systems that use energy from solar radiation directly to cool the air provided in the
air conditioning, should be considered at the planning stage(https://cielowigle.com/blog/solar-powered-air-conditioner/). In some situations, withlimited heat exposure, the installation of fans to create air movement over work20

areas can be an effective solution. However, when the heat goes above therecommended levels referred to in Section 5, further prevention is needed.
c. Basic Occupational Health services and drinking water accessIn order to ensure that any remaining heat problems are fully dealt with, it is essential
to provide basic occupational health management in every workplace. Such a
service is not only an essential part of heat protection but also helps to protect
workers from a broader range of other health hazards. A primary need for workers isclean drinking water to replace liquid loss due to sweating. Individual needs vary, so
unlimited supply of clean drinking water at the actual worksite is essential. In very hotjobs a worker can sweat as much as 10-15 L in a day. During intensive sweating
body salts are also lost and need to be replaced by mineral drinks.
Depending on the size of the workforce, the services of a health and safety expert, anurse, a medical doctor or other staff with health training should be made available.
Their role is to supervise the monitoring and interpretation of heat exposure levels, toprovide advice on the cooling and protection actions needed, and to manage any
clinical health problems that occur. Features of good occupational health services
are described in documents from the ILO:
( https://www.ilo.org/global/standards/subjects-covered-by-international-labourstandards/occupational-safety-and-health/lang-en/index.htm#:~:text=The%20convention%20provides%20for%20the,and%20to%20i
mprove%20working%20conditions.).
d. Managerial protection decisions by providing rest breaks
An important way to protect workers from heat is to schedule breaks as stated in theinternational standard (ISO, 2017) and the USA national guideline (NIOSH, 2016) as
discussed earlier. The need for breaks or cooling depends on the work intensity ineach operation, so the application of such measures needs to be analysed for the
specific job tasks to be carried out in this location. Figure 11 shows the percentageof work time at different work intensity (metabolic heat) that is recommended at
different hourly WBGT levels. Light work (e.g. office) has a metabolic heat level
between 150 and 250 W; moderate work in a factory 250-350 W; heavy work 400W
and higher.
Scheduling intensive work to cooler parts of the day (or night) or cooler parts of theyear is another way to manage heat exposure and related productivity loss. The
tables above in Section 5 are a guide to how work slows down when it is excessively
hot. If workers are working under stress because of heat, Negative effects on healthand productivity will emerge.

21Figure 11. Recommended heat stress exposure limits and need for rest
periods for heat acclimatized workers (NIOSH, 2016). X-axis = work intensity
expressed as total Metabolic Rate in Watts. Y-axis = hourly WBGT level. Fourdifferent curves for safety limits shown based on fraction of the work hour that theworker takes rest (hourly work = 60 minutes, 45, 30, or 15 minutes.)e. Clothing and personal protection equipment (PPE)In certain work situations, the cooling of a building or other protections are still not
sufficient so PPEs can be used for protection. For example, there are special
garments that have cold water flowing through them and others are made of special
materials that melt at workplace temperatures (Ren et al., 2022). This provides
cooling underneath the garments. Protective helmets with face screens can have a
fan inside to provide extra air flow; such a device provides some comfort but does
not cool the air.
Local cool air supply equipment that targets individual work stations is also a type of
PPE. Another feature of personal protection is the type of clothing worn by workers.
In hot environments loose light clothing is best from a heat protection viewpoint, butsome jobs may involve chemical or other hazards that require protective clothing,which in turn can add significant heat risk as the evaporation of sweat in hot
conditions is reduced. The guidelines from ISO and NIOSH include methods toadjust the heat levels at which protection action is needed. Figure 11 shows theguidance for rest breaks for workers wearing light clothing. If workers use doublelayer cloth clothing this adds 3C to the WBGT values in Figure 11. If workers use
limited use vapour barrier overalls, 11C should be added (meaning that a WBGT
level as low as 19C creates heat risks even for light work).
22

One example of such heat problems with protective clothing was the heat stress that
occurred inside plastic clothing worn by health staff during the Ebola epidemic inWest Africa in 2016 (Kuklane et al., 2015). The protection from the highly infectious
Ebola virus was vital for the nurses and doctors attending to their patients so theyneeded to use totally sealed clothing with filtered air supply via pumps. Even in
relatively moderate heat conditions, staff were sweating so heavily that they could
only work for 30 minutes before having to rest and change their clothing. Taking theprotective clothing off added to the risk of infection for staff. The hot working
environment in this country at the time was a major underlying problem.
f. Reducing increase of local heat levels via climate change mitigation
It should be emphasized that the heat conditions in the future will deteriorate asclimate change brings about global heating; already hot locations will become evenhotter. Limiting the degree to which such heating will occur is an essential step toprotect workers health in the future and reduce the economic consequences of
productivity loss.
10. Importance of climate change mitigation
New enterprises may be actively producing economic output, enhancing social wellbeing and producing commercially valuable products and employment for decades tocome. It is therefore vitally important to consider the potential future heat conditions
at a location of interest at the planning stage.
Analysis of future heat challenges is a part of the WorkHeat tool and it is possible toestimate the difference in future heat levels that mitigation can achieve (see Section
8). SSP370 data is based on current green-house gas (GHG) emission trends andshows what is likely to happen if further mitigation is not implemented. SSP126 is themost ambitious GHG emission pathway which shows the reduced heat levels withadvanced mitigation of climate change. The difference can be large and can save
investors substantial resources in reducing future cooling costs or productivity loss.
Mitigation primarily involves reducing energy use from fossil fuels. This can beachieved by:-

Low carbon footprint of the building materials used for the workplace
Use of local renewable energy for electricity supply for production
Use of renewable energy for transport of raw materials, workers and products
Recycling and reuse of raw materials or product parts for new products

Investors and enterprise managers can also contribute effectively to mitigation efforts
beyond their own production activities, by promoting technologies with low carbon
footprint, cooperating with other enterprises to reduce their carbon footprint, andsupporting government policies and regulations that aim to strengthening mitigation.
11. Conclusions
Workplace heat is an important occupational health hazard that not only threatens
workers health but also reduces labour productivity. I It is essential to makeassessments of the potential heat risks in locations of interest when planning forinvestment. This Workplace Heat Exposure Assessment Tool provides a method23and data to carry out such an assessment and can also be used to assess the heatsituation in existing workplaces.
For investments in new workplaces, the decisions to make include:-

The choice of location
What job types will be involved and what is their required work intensity?
How many workers will there be in each job type?
What are the current heat challenges for workers in this location?
How can the current heat challenges be overcome with investments?
What are the costs for protecting this workforce from the heat challenges?
What are the future heat challenges in this location?
What are the additional costs for future heat protection?
How can this workplace be designed and operated with a minimum carbon
footprint?

12. References and further reading
ADB (2022) Beating the heat: Investing in pro-poor solutions for urban resilience.
(Kjellstrom co-author) Manila, Asian Development Bank.
ISO. Hot environments - Estimation of the heat stress on working man, based on the
WBGT-index (wet bulb globe temperature). ISO Standard 7243. Update. Geneva:
International Standards Organization; 2017.
Kjellstrom T, Holmer I, Lemke B. (2009) Workplace heat stress, health andproductivity – an increasing challenge for low and middle-income countries during
climate change. Global Health Action 2009 (on website:www.globalhealthaction.net). DOI 10.3402/gha.v2i0.2047.
Kjellstrom T, Briggs D, Freyberg C, Lemke B, Otto M, Hyatt O (2016) Heat, humanperformance and occupational health -- a review and assessment of global climatechange impacts. Annual Review of Public Health 37, 97-112.
Kjellstrom T, Freyberg, C, Lemke B, Otto M, Briggs D (2018) Estimating population
heat exposure and impacts on working people in conjunction with climate change. Int
J Biometeorology 62: 291-306. (https://doi.org/10.1007/s00484-017-1407-0)
Kuklane K, Lundgren K, Gao C, et al. (2015) Ebola: Improving the Design ofProtective Clothing for Emergency Workers Allows Them to Better Cope with HeatStress and Help to Contain the Epidemic. Ann Occup Hygiene, 59, 258-261.
NIOSH (2016). NIOSH criteria for a recommended standard: occupational exposure
to heat and hot environments. By Jacklitsch B, Williams WJ, Musolin K, Coca A, Kim
J-H, Turner N. Cincinnati, OH: U.S. Department of Health and Human Services,Centers for Disease Control and Prevention, National Institute for Occupational
Safety and Health, DHHS (NIOSH) Publication 2016-106.
Parsons K. (2014) Human thermal environment. The effects of hot, moderate andcold temperatures on human health, comfort and performance. 3rd edition. New
York: CRC Press.
24

Sahu S, Sett M, Kjellstrom T. Heat Exposure, Cardiovascular Stress and Work
Productivity in Rice Harvesters in India: Implications for a Climate Change Future.
Ind Health, 2013, 51, 424-431.
Ren S, Han M, Fang J (2022) Personal cooling garments: a review. Polymers 14(24), 5522; https://doi.org/10.3390/polym14245522.
Wyndham CH (1969). Adaptation to heat and cold. Env Res 2, 442-469.

25

Appendix. Survey of user experiences of this WorkHeat tool.
Users are asked to go through the process of choosing a location for a newenterprise and assessing the current and future workplace heat exposure risks.
After spending an hour reading the WorkHeat tool, consulting the ClimateCHIP.org
website and preparing short notes on the heat risks, they will complete the following
questionnaire.
WorkHeat tool test questionnaire
What type of industry is your intended investment?
____________________________
Where in the world was this to be located?
______________________________________
On a scale of 1 to 5 please respond to the following questions.
Answers should fit with:
1= not at all

2=a little bit

3=yes, in parts

4=yes, to a greater degree

5=yes, absolutely

Question
A. Did you learn useful information about heat stress challenges inworkplaces from reading this tool?
B. Was the ClimateCHIP.org data useful to assess the heatsituation your investment may face?
C. Did the step-by-step process in the tool help you find theinformation of importance on the website?
D. After completing the tool process do you feel more confident
about actions needed to be taken to achieve heat protection?
E. Would you recommend this tool to others seeking climate
relevant information for future investment decisions?
F. Are there any changes in the tool you would suggest for its
improvement?
Please write a list of suggested changes below.

AnswerMany thanks for your help.

26