How heat illnesses occurs
Heat illness is caused by extremely high body temperature resulting in damage tointernal organs. If you feel unwell after spending time in the heat, consider the possibilityof heat illness, regardless of the symptoms.

Hot environment
Strenuous exercise/activity

Normalsituation

Body temperature rise

Radiate heat

Radiate heat

Body temperature self-regulation
Sweating
Sweat evaporation(heat of evaporation)

dangerous
situation

Increasing bloodflow under skin

Heat dissipationfrom the skin surface
to the environment

Heat production＞diffusion
Blood flow decreases↓Heat accumulates↓
Body temperature rises

Heat Illness■What causes heat illness?

The human body regulates heat production and diﬀusion to keep the body temperature
within normal range. It cools itself by expanding peripheral vessels and increasing
subcutaneous blood ﬂow, dissipating heat into the air, as well as sweating and its
evaporation. If the balance between heat production and diﬀusion is lost, bodytemperature rises rapidly.

Under hot conditions, heavy sweating depletes the body of water and salt, causing

dehydration. Decrease in body ﬂuid and salt may result in heat cramps or fainting causedby the lack of blood to the muscles and the brain.

Heat illness is a result of these processes. Severe heat illness can be fatal but can be
avoided with appropriate prevention and treatment.

Symptoms of heat illness
When body temperature rises in hot environments, subcutaneous blood vessels expand
to increase blood ﬂow and diﬀuse heat from the skin to the surrounding air.

■Mild heat illness (Grade1)

Dehydration and diversion of blood ﬂow

Numbnessfrom the brain and other major organsDizzinesscauses fainting. Drinking water with nosaline or electrolyte results in reduced

blood salinity, which may cause painful

Light-headedness

Level 1
Mild heat illness

Muscle cramp
Nauseaheat cramps.

Headache■Moderate heat illness (Grade 2)

NauseaThe blood ﬂow decreases from heavy

sweating, diversion of blood to the skin,and additional provision of blood to themuscles during exercise or activity. This

Heat exhaustion

Level 2Moderate heat illness

Unconsciousness

causes lower blood pressure, which

Convulsions

leads to further decrease in blood ﬂow.

Hot dry skinThis may result in fainting, headache,vomiting, abdominal pain, diarrhea,
hypouresis, and other systemic

symptoms. The increase in bodyFatigueConfusion
Incoherency

Level 3Extreme heat illness

Inability to walk straightInability to run

temperature is less than that of severe

heat illness, and remains < 40°
C. The patient may experience slight confusion, but loss ofconsciousness does not occur.

■Severe heat illness (Grade 3)

If dehydration continues, the body temperature increases up to >40°
C, causing damage
to the brain and other major organs, and may lead to unconsciousness. This is heatstroke. The level of consciousness is important in the diagnosis; other symptoms such as
slow response, inability to state oneʼ s name/location or the date, and general
incoherency all indicate heat stroke as well.

Risk factors of heat illness■ People vulnerable to heat

The following are examples of people who are at high risk of heat illness.

・Elderly people
・Children・People with dehydration (diarrheaor infections)・People with heart disease, diabetes,People vulnerable to heat illness
ObesepeoplePeople
with chronic
illness

psychoneurotic disorders, skindiseases, etc.

Elderly people andchildren

・People taking medication for heartdisease, high blood pressure andothers

・People who have hangovers

・People from cool regions who are

Alcohol use
Without enoughsleep
Having a cold/
diarrhea

People unacclimatedto heatunaccustomed to heat・People in wheelchairs (they are closer to the hot ground)■ Environmental risk factors

In hot, humid environments with weak wind and radiant heat sources, heat discharge

from the body decreases, and sweat evaporation decreases, thereby increasing the risk ofheat illness. Construction sites, playgrounds, gymnasiums, bathrooms, poorly ventilatedbuildings, and top-ﬂoor apartments are high-risk places for heat illness.

Pay attention to the risk ofheat illness in these conditions
High temperature

High humidity

Weak wind

Sudden hot conditions
Heat wave

First aid for heat illness
If you feel unwell after spending time in the heat, consider the possibility of heat illness,regardless of what kind of symptoms you have. Move to a cool place, and drink plenty ofﬂuids (electrolyte-replenishing sports drink, oral rehydration solution, or saline solution ifpossible).

If you suspect someone has heat illness, move the person to a cool place, loosen his/herclothes, and cool the body as soon as possible. Sprinkle water or put wet towels on theperson and cool with a fan. Make the person drink some ﬂuids. However, if the person is
unconscious or unable to drink, take him/her to a hospital immediately.

First aid for Heat illness.
Checkpoint1

If someone around you has heatstroke...
Stay calm, assess the situation and respond asappropriate. First response is critical.

Are there any symptomsof heat illnesses?

Dizziness, fainting, muscular pain, rigidity, heavy sweating,headache, discomfort, vomiting, exhaustion, sinking feeling,
impaired consciousness, cramps, disturbance of motility, highbody temperature,

YES
Checkpoint2 Is the person
responding?

NO

While waiting for the ambulance,
make him/her rest at a cool place,release clothes and cool the body.

YESTake him/her to cool/shaded/
air conditioned apace, release
clothes, cool body and takerests

Checkpoint3 Can he/she drink

by himself/herself?

NOYES

Checkpoint4

Symptoms areimproved?

YES
Stay calm and take plenty of rest.
Go home after the symptoms
have improved.

Take him/her tocool/shaded/air
conditioned
apace, release
clothes, cool bodyand take rests
Place ice packs/gels around theneck, armpits, and base of the legs,
where large veins are running close
to the skin surface.

Drink ﬂuids and replace the salt
lost in your sweat.
Heavy sweating
removes salt andminerals from thebody. Fluids such assports drinks andoral rehydration
solutions are useful.

Call an ambulance (call 119)

NOTo
medicalcentersThose who knows about the situation should
accompany the person when he/she is taken tothe hospital.

Prevent heat illness
These are ways to reduce the risk of heat illness:□ 1）Avoid heat stress
Shield yourself from the sun with clothes, a hat, an umbrella, and any otheraccessories. Walk in the shade wherever possible.
□ 2）Try to keep the air ﬂow around you
Use a handheld fan.
□ 3）Let sweat evaporate
Wear breathable clothes.
□ 4）Try to adjust your schedule
Schedule outdoor activities for cooler hours of the day.
□ 5）Be careful of acute heat exposure
Special care is needed in the early summer and right after the rainy season. Takefrequent breaks for the ﬁrst three days after being exposed to hot climates.
□ 6）Find cool places to take a break
Look for air-conditioned facilities, shops, and other places.
□ 7）Use rest areas eﬀectively
Use shade and fans in air-conditioned places.
□ 8）Prevent dehydration
Drink plenty of ﬂuids. Take saline to replace salt lost in sweat. Drink a
glucose-electrolyte solution with 0.1‒0.2% sodium concentration. Dark-coloredurine is a sign of dehydration.
□ 9）Avoid overexertion
Consider skipping outdoor activities in hot environments. Do not
try to keep up with others in hot environments.
□ 10）Stay healthy
Eat three meals a day. Take at least 6 h of sleep at night.
Insomnia, hangovers, fevers, and diarrhea can weaken resilience
to heat stress. Some medication may also increase the risk ofheat illness, so seek your physician about the side eﬀects.
□11）Acclimatize to heat
Take short exercises over a couple of days to acclimatize yourself to hot conditions.
□ 12）Keep an eye on those who have a higher risk of heat illness
Pay special attention to new staﬀ and visitors, especially those from cool, dry
regions. Pay special attention to elderly people, children, obese people withsedentary lifestyle, and others at risk.

Checklist before work/activity
Pre-work/activity risk checklist ‒ red ﬂags
The following are risk factors of heat illness. Check before your work/activity and takepreventive measures.

□ Tasks involving overexertion□ Incomplete acclimatization(exposure to heat for less than three days)□ History of heat illness□ Obesity□ Using medication for chronic conditions,

Using medication

hypertension, and similar conditions□ Lack of sleep□ Excessive alcohol intake□ Hangover□ No breakfast□ having cold, diarrhea,
or other conditions□ Dehydration

Dehydration

Lack of sleep

Checklist for elderly people
Checklist for elderly people□ Hydrate frequently even if you are not thirsty.
□ Check indoor temperatures even if it doesn't feel hot.
□ Exercise for acclimatization.

OFFChecklist for caregivers□ General wellbeing : liveliness. appetite, anddyness of the mouth/armpits□ Metrics : weight, blood pressure, heartbeat, andbody temperature□ Enviroment : daily schedule, inddor temperature/humidity, ventilation, and shade■ Elderly people are insensitive to heat

Studies have shown that summer temperatures in residences of people aged ≥ 70 years are 2°C
higher than in others, with levels often exceeding 31‒32°C and almost a 5% higher humidity. Thismay be because they dislike artiﬁcial cooling or want to save electricity. Skin sensor functionality
decrease with aging, and delays the regulation of body temperature.

■ Elderly people are more vulnerable to heat

In elderly people, temperature regulation based on subcutaneous blood ﬂow and sweating is lesseﬃcient than that in younger people. As a result, elderly people may not be able to eﬀectively
diﬀuse heat, and their core body temperature may easily rise.

Checklist for children
Ways to prevent heat illness in children□ 1. Keep an eye on their facial color and sweating
Facial redness and/or heavy sweating are signs of increased core body temperature.
Move the child to a cooler place and allow to rest.
□ 2. Make sure they drink ﬂuids often
Make sure they drink ﬂuids as soon as they feel thirsty.
□ 3. Make sure to let them acclimatize to heat
Let them take outdoor activities and promote heat acclimatization.
□ 4. Choose appropriate clothingChildren lack the necessary knowledge to choose clothing appropriate for theenvironment. Parents and other adults should ensure appropriate clothing to enhanceheat diﬀusion.

■ Children easily get heatChildren in hot environments have a much higher subcutaneous blood ﬂow to diﬀuse
the heat than that in adults, since their sweating capacity is not fully developed.
Therefore, childrenʼs body temperature can rise and fall easily.

■When children are in hot environments

When the environment is cooler than the skin temperature, subcutaneous blood ﬂow

increases to cool the body. However, in hotter conditions (where sweat evaporation is
the only eﬀective method), not only are children unable to diﬀuse heat, they actuallyabsorb it from their surrounding environment. This results in a rapid rise in bodytemperature, leading to heat illness.
Children have limited
sweating capacity.

Body surface area / Body weightChildren > adults

Rise of core temperature
Air < Skin …… Children = Adults
Air > Skin …… Children > Adults

Subcutaneous
blood ﬂow

Sweat glandsChecklist for sports
Risk factors of heat illness during sports are related to the environment, oneʼs condition,and exercise intensity. Attention should be paid to the points outlined below:□ Environmental conditions

Check the weather, and avoid exercising in hot daytime conditions whenever possible.

Wet-bulb globe temperature (WBGT) ‒ an index representing temperature, humidity,
radiation heat, and wind ‒ is used for the evaluation of environmental conditions.

□ Adjust exercise intensity and take breaks according to environmentalconditions
・When the WBGT is > 25°
C, take a break at least every 30 min.

・When the WBGT is > 28°
C, avoid strenuous exercise, such as long-distance running, andtake frequent breaks.

・When the WBGT > 31°
C, outdoor exercise should be avoided.
・Make sure to rest if you feel unwell.

□ Take water and salt frequently

・Make sure to drink plenty of ﬂuids.

・Salt is lost from the body through sweat. Sports drinks and saline solution of 0.1‒0.2%
concentration are adequate for ﬂuid replacement.

・Post-exercise weight loss should be maintained within 2% with ﬂuid replacement.

□ Acclimatize to heat・People who are not acclimatized to heat are at risk of heat illness. If the weather suddenly
turns hot, engage in only short periods of light exercise until you acclimatize.

□ Take care of people at high risk

・Elderly people, infants, and obese people are at higher risk of heat illness;

・People with diarrhea, fever, fatigue, or inadequate sleep are also vulnerable to heat illness
and should avoid strenuous exercise in hot environments.

□ Wear appropriate clothing・Wear light clothes made of hygroscopic and breathable materials, and a hat to block direct
sunlight.

Tips to prevent heat illnesses
during summer events
Reducing the risk of heat illness during outdoor events are important. Organizers should
conduct the following measures:□ Prevent waiting lines under hot conditions
・Guide people to the shade.

・Use numbered tickets with clearly displayed return times so that people do not haveto spend long periods waiting in line.

・Allow seat reservations to prevent the need for waiting in line.
□ Avoid congestion at event openings

・Provide enough wide-entrance gates.

・Plan the event program to prevent congestion at entrance gates.
□ Avoid congestion at event closures
・Provide enough exit gates.

・Set a one-way system from exit gates to transportation facilities.
・Do not rush people.

□ Ease access to necessary facilities

・Clearly show where to access drinking water, vending machines, concession stands,etc.

・Clearly show where medical aid stations are.
□ Prepare adequate resting places and beverages
・Prepare resting places for attendees.

・Monitor the location waiting lines and provide water facilities/vending machines.
・Ensure that vending machines are appropriately maintained.

Provide break areas

Provide timely guidance to attendees
via announcements and noticesProvide plentyof exit gatesEﬀective placement ofwater points and vending
machines

Event facilities

Establish rest spaces
for use during the event

Entry and exit gate

Nearest station

Congestion

aisle

Waiting in the hot sun

Do not rush people

Heat relief at event sites

Poorly ventilated area

Ensure waiting lines
are in the shade

High-risk area

Risk assessment using WBGTPrecautions in line with WBGT risk ranks
WBGT

Activity guide in daily
life

Guide to how much exercise canbe safely performed

Risk of occurrence ishigh in elderly peopleeven at rest.
Avoid staying
outdoors as much as
possible, and move toa cool place.

Danger (exercise should beavoided). The environmental
temperature is higher than the skintemperature, so the body heatcannot escape. Except in special
cases, all exercises should beavoided.

May occurduring any
daily
activities

Avoid staying underthe sun.
Keep an eye on therise of indoor
temperature.

Severe warning (heavy exercise
should be avoided)
Activities that require heavy
exercise should be avoided. When
exercising, frequent breaks andplenty of ﬂuids should be provided.
People who are at high risk should
avoid exercise.

May occurduringmoderate
activities

Take breaks regularly
during exercise orstrenuous activity

Warning (rests should be providedoften)
Frequent breaks and plenty ofﬂuids should be provided. Breaks
should be provided every 30 min
for activities requiring heavy
exercise.

May occurduringheavy
activities

Risk of occurrence is
low in general.
Caution is advised
during heavy exercise
or strenuous work.

Caution is advised since there is stilla risk of heat illness. Drinkingplenty of water during exercise isadvised.

Risk of Heatillness≥ 31 ℃

28 - 31 ℃

25 - 28 ℃

21 - 25 ℃