Working in the Heat: Health & Performance Risks Explained

Key Takeaways 

• Research summarized in the original GSSI article suggests over 2.4 billion workers worldwide are exposed to excessive heat each year 

• Heat exposure is associated with increased risk of heat illness, dehydration, accidents, and kidney injury 

• Severe heat illness can be a medical emergency; workplace protocols and medical guidance should be followed 

• Repeated heat stress may contribute to chronic kidney disease in workers 

• About 30% of workers experience productivity losses from heat exposure as observed in the research 

• Productivity decreases 2.6% for every 1°C increase above 24°C WBGT in the conditions studied 

• Global economic losses from occupational heat stress could reach $2.5 trillion by 2030 according to research assumptions

This article summarizes findings from published scientific research (as described in the original GSSI article linked). It is provided for general informational purposes and does not constitute medical or safety advice. 

Many workers perform physically demanding jobs every day. Construction workers, agricultural laborers, miners, and factory employees regularly lift, carry, and move while working long hours in challenging environments. 

Because of these physical demands, workers are sometimes described as “industrial athletes.” Like athletes, they rely on strength, endurance, and focus to perform their jobs. But unlike athletes, workers may perform these tasks in extreme heat while wearing protective equipment and without structured recovery or cooling strategies. 

Globally, the scale of the issue is enormous. Published estimates summarized in research studies suggest approximately 2.41 billion workers are exposed to excessive heat each year, and research associates occupational heat exposure with millions of workplace injuries and thousands of deaths annually. 

Even more striking is that the research indicates approximately 90% of occupational heat exposure may occur outside of heatwaves. Elevated heat strain can occur during everyday work conditions, not just during extreme weather. 

As global temperatures rise, researchers continue to examine how heat affects worker safety and performance is becoming increasingly important. 

Why Heat Can Be Harder on Workers Than Athletes 

​Much of what scientists know about heat physiology (particularly in the United States) comes from sports or military research. However, these findings do not always translate directly to occupational settings. 

Workers often experience several challenges that increase heat strain, including: 

• Long consecutive workdays with limited recovery 

• Protective clothing that traps heat 

• Limited access to cooling strategies or medical support 

• Financial pressure to continue working despite hot conditions 

Many working populations also have underlying health factors that can influence how the body responds to heat. 

Because of these differences, occupational heat stress requires its own research and prevention strategies. 

What Happens to the Body During Heat Stress 

During physical activity, the body naturally produces heat. Normally, the body maintains temperature through sweating and increased blood flow to the skin. 

Sweating cools the body as moisture evaporates from the skin, while increased blood flow helps release heat into the surrounding environment. 

However, when the heat produced by physical work exceeds the body’s ability to dissipate it, core temperature begins to rise. 

This can create significant physiological strain. Workers performing physical labor in hot environments often experience: 

• Increased skin temperature 

• Elevated heart rate 

• Heavy sweating 

• Growing fatigue 

If heat strain continues to increase, it can lead to serious heat-related symptoms that impact safety and performance, and risk can vary based on conditions such as workload, environment, clothing, and recovery opportunities. 

​Reported cases of severe heat-related incidents are relatively low, but researchers and public health sources note the true number is likely higher due to underreporting and misclassification. 

Hydration and Whole-Body Stress 

Sweating is essential for cooling, but it also leads to significant fluid loss. When sweating occurs without adequate fluid replacement, dehydration develops. 

Dehydration can increase heart rate, raises core temperature, and places additional strain on the body during physical work. 

One major concern identified in the research is the added stress placed on the body when elevated temperature and fluid loss occur together over time. 

Repeated exposure to heat and inadequate hydration may contribute to long-term strain on key organs and systems. 

In many high-heat industries such as agriculture, construction, and mining, these challenges are especially common due to long work hours and limited access to cooling and hydration strategies. 

A major challenge is that early signs of heat strain can be subtle, making it difficult to recognize when the body is under increasing stress. 

The Impact of Heat Stress on Work Performance 

Heat exposure affects more than safety. It also reduces the ability to work effectively. 

When the body experiences heat strain, fatigue increases, cognitive performance declines, and physical discomfort rises. These changes reduce both work capacity and work quality. 

Environmental factors can also increase risk. Sweat can impair vision, goggles may fog, and wet hands can reduce grip on tools. 

A meta-analysis of 11 studies involving 8,076 workers estimated that 30% of workers experience productivity losses due to occupational heat stress. 

Researchers also found that productivity was estimated to decrease by about 2.6% for every 1°C increase in wet bulb globe temperature above 24°C in the conditions studied. 

The Economic Cost of Heat Stress 

The impact of heat stress extends beyond individual workers to entire economies. 

Global productivity losses related to occupational heat exposure were estimated at $311 billion in 2010. By 2030, those losses are projected (in published economic analyses) to reach $2.4–2.5 trillion, representing more than 1% of global GDP. 

In the United States alone, heat exposure has been modeled to lead to $100 billion in annual economic losses, potentially doubling by 2030 and reaching $500 billion by 2050 depending on assumptions and mitigation effort strategies. 

Productivity losses occur through two main pathways: 

• Presenteeism, when workers remain on the job but cannot perform at full capacity due to fatigue, dehydration, or heat strain 

• Absenteeism, when workers miss work due to heat-related challenges or recovery needs 

Both outcomes affect worker safety, wages, and organizational performance. 

Why Early Awareness and Prevention Matter 

Understanding the safety and performance impacts of occupational heat stress is the first step toward protecting workers. 

Early awareness of heat strain and effective workplace heat management strategies can help reduce risk, support long-term well-being, and maintain productivity. 

Monitoring for signs of heat strain, providing rest breaks, and ensuring consistent access to fluids are commonly recommended components of heat safety programs. 

As global temperatures rise, implementing effective heat safety strategies will become increasingly important for protecting worker safety, performance, and productivity.