Why WHO and WMO Issued This Report

In August 2025, the World Health Organization (WHO) and the World Meteorological Organization (WMO) released a joint report and technical guidance on protecting workers from increasing heat stress.

The reason behind this report is simple and urgent: global temperatures are rising, extreme heat events are becoming more frequent, and workers are paying the price first.

Across construction sites, farms, factories, logistics hubs, and outdoor service jobs, heat is no longer just uncomfortable.
It is becoming a direct cause of injuries, medical emergencies, lost productivity, and long-term health damage.

This report was not written for academics.
It was written because existing systems are failing to protect people who must work in hot environments.

What “Heat Stress” Actually Means

When the report uses the term heat stress, it is not talking about feeling hot or sweating more than usual.

Heat stress describes a physical condition in which the human body can no longer control its internal temperature.

This typically happens when several factors occur at the same time:

• The surrounding temperature is high
• Humidity is high
• The worker is physically active
• Protective clothing limits airflow
• Rest and hydration are insufficient

Once the heat entering the body becomes greater than the heat the body can release, the body begins to fail step by step.

What Happens Inside the Body During Heat Stress

Heat stress is predictable.
It follows a clear physical sequence.

First, the body’s core temperature begins to rise.
The heart must work harder to pump blood to the skin in an attempt to release heat.

Second, sweating increases sharply.
Large amounts of water and electrolytes are lost.
If these are not replaced fast enough, dehydration begins.

Third, blood volume drops.
Less oxygen reaches the brain and vital organs.
At this stage, concentration declines and reaction time slows.

This is why heat stress dramatically increases workplace accidents.

If exposure continues, the body loses its ability to cool itself.
When core body temperature exceeds approximately 40°C (104°F), heatstroke occurs.

Heatstroke is a medical emergency.
Without rapid cooling and treatment, it can lead to organ failure or death.

This process does not depend on nationality, experience, or “heat tolerance”.
Human physiology has fixed limits.

Why Workers Are at Much Higher Risk Than the General Public

WHO and WMO focus heavily on workers for one key reason: work produces internal heat.

Heat exposure comes from two directions at the same time.

External heat comes from the environment: sunlight, hot air, machinery, concrete, asphalt, and metal surfaces.

Internal heat is generated by the muscles during physical work.

A person resting in hot weather may feel uncomfortable.
A person performing physical labor under the same conditions may collapse.

This is why heat stress disproportionately affects industries such as:

• Construction
• Agriculture
• Manufacturing
• Mining
• Logistics and transportation
• Outdoor maintenance and services

Why Heat-Related Illness Is Often Underestimated

One critical point emphasized by WHO and WMO is that heat-related illness is widely underreported.

In real workplaces, heatstroke may be recorded as a cardiac event, fatigue, or collapse without linking it to heat exposure.

Chronic heat exposure can slowly damage the kidneys and cardiovascular system without immediate symptoms.

As a result, low official numbers often create a false sense of safety.
Low reporting does not mean low risk.

Heat Stress Is Already Reducing Work Capacity

WHO analysis shows that for every 1°C increase above a comfortable working temperature, labor productivity drops by approximately 2–3%.

In practical terms, this means:

• Slower work speed
• More mistakes
• Higher accident rates
• Longer recovery time
• Higher employee turnover

Heat stress is not only a health problem.
It is a direct operational and economic problem.

Why “Hot Countries” Are Not Proof of Safety

Many people assume that populations in hot regions are naturally more resistant to heat.
WHO and WMO clearly reject this idea.

What actually reduces risk in hot regions is not biology, but systems:

• Adjusted working hours
• Mandatory rest and hydration rules
• Heat-specific safety regulations
• Cultural avoidance of peak heat hours

When these systems fail or are removed, heat-related illness rises immediately.
Adaptation is system-based, not genetic.

The Core Message for Employers and Workers

The WHO & WMO report delivers one clear conclusion:

Heat stress is predictable, preventable, and manageable — but only if it is treated as a real occupational hazard.

Ignoring heat stress leads to medical emergencies, productivity loss, legal liability, and long-term damage to the workforce.

As global temperatures continue to rise, managing heat stress will become a basic requirement of safe and sustainable work.