How Workers Can Stay Safe While Working in the Heat

Key Takeaways 

• Research shows occupational heat exposure can increase physiological strain, fatigue, heat illness risk, and reduce work capacity 

• Studies report that many workers begin their shifts already dehydrated and may not fully replace fluid losses during the workday 

• Research has associated dehydration with higher heart rates, increased core temperatures, and greater physiological strain during work 

• Studies found hydration interventions may help support hydration status and reduce markers associated with kidney stress 

• Research suggests maintaining hydration may also help support productivity during physically demanding work 

• Studies examining glucose-electrolyte beverages reported improved hydration outcomes compared with water alone under the conditions evaluated 

• Occupational heat prevention programs commonly include hydration access, rest opportunities, shade, and cooling strategies 

• Research suggests combining hydration and cooling approaches may help reduce heat strain during work in hot environments

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

Imagine performing physically demanding work for hours under the summer sun. 

As the day progresses, you may notice sweat accumulates, body temperature rises, and maintaining the same pace becomes increasingly difficult. What can start as normal fatigue may gradually place additional strain on the body's cardiovascular and thermoregulatory systems. 

According to occupational heat research, working in hot environments can affect more than comfort. Excessive heat exposure has been associated with fatigue, heat-related illness, kidney injury, and reductions in work capacity. 

Because heat exposure can affect both health and productivity, researchers have examined a variety of strategies designed to help workers manage physiological strain during hot working conditions. Among the most commonly studied approaches are hydration, electrolyte replacement, cooling interventions, rest opportunities, and shaded recovery areas. 

Why Working in the Heat Can Place Stress on the Body 

Physical work generates heat within the body. When environmental temperatures are also high, the body may need to work harder to maintain a safe internal temperature. 

Sweating serves as the body's primary cooling mechanism. As sweat evaporates from the skin, heat is removed from the body, helping regulate temperature during physical activity. 

However, this cooling process comes with a cost: fluid loss. 

When fluid losses accumulate and are not fully replaced, dehydration can occur. Research suggests dehydration may increase cardiovascular strain and make it more difficult for the body to regulate temperature during physical work. 

Over time, these physiological challenges may contribute to fatigue, reduced work performance, and increased heat-related health risks. 

Many Workers May Begin Their Day Dehydrated 

Research suggests that dehydration can be common across a variety of occupational settings. 

Studies have reported that between 15% and 100% of workers arrive at work already hypohydrated, and many do not fully replace fluid losses during their shifts. 

Researchers have identified several workplace factors that may make maintaining hydration more difficult, including: 

• Personal protective equipment that  limits opportunities to drink 

• Limited access to drinking water 

• Restricted restroom availability 

• Remote work locations where fluids must be transported and stored 

These factors can create challenges for workers attempting to maintain fluid balance throughout long shifts in hot environments. 

How Dehydration May Increase Heat Strain 

Research has consistently shown that dehydration has been associated with increases in physiological strain during physical work. 

As body water levels decline, blood volume decreases. The cardiovascular system must then work harder to maintain circulation and deliver oxygen throughout the body. 

Studies report that heart rate may increase by approximately 3-5 beats per minute for every 1% loss of body mass resulting from dehydration. 

Researchers have also observed increases in core temperature as dehydration progresses. According to the research, core temperature may rise by approximately 0.25°C for each additional 1% body mass loss. 

Together, these physiological changes may increase feelings of fatigue and contribute to the development of heat-related illness. 

Researchers have also examined the relationship between repeated dehydration and kidney health. Field studies involving agricultural workers have reported high rates of both hypohydration and acute kidney injury during periods of physically demanding work in hot conditions. 

How Hydration May Support Worker Health and Productivity 

Because dehydration is common in occupational settings, researchers have examined whether hydration interventions can reduce heat strain and support worker performance. 

Several studies suggest replacing fluids during work may improve hydration status and reduce markers associated with kidney stress. 

In one study, participants who replaced 100% of body mass lost through sweating experienced a 16% reduction in a biomarker associated with kidney injury compared with participants who did not replace fluids. 

Research has also examined the relationship between hydration and work output. 

In a study of forest workers performing manual harvesting tasks, workers who maintained hydration harvested 12% more trees than workers whose fluid intake was restricted. 

Similarly, observational research involving sugarcane workers found that individuals who consumed more than six liters of fluid per day demonstrated greater work output than workers who consumed less fluid. 

While workplace conditions vary, these findings suggest hydration status may influence both physiological responses and productivity during physically demanding work in the heat. 

The Role of Electrolytes During Long Work Shifts 

Sweat contains more than water. 

Electrolytes such as sodium and potassium are also lost during prolonged physical activity and play important roles in fluid balance and normal cellular function. 

Researchers have examined whether replacing electrolytes alongside fluids may influence hydration outcomes during physically demanding work in hot environments. 

In one intervention involving agricultural workers, participants consumed either water alone or water combined with a glucose-electrolyte beverage. 

Following the work shift, acute kidney injury occurred in 18% of the control group and 23% of the water-only group, while no cases were reported in the glucose-electrolyte group under the conditions studied. 

Other occupational studies examining electrolyte supplementation programs have reported maintained hydration status and preserved kidney function during periods of prolonged work in the heat. 

These findings suggest electrolyte replacement may play an important role alongside fluid replacement during extended periods of sweating. 

What Research Shows About Water, Rest, and Shade Programs 

Researchers have also examined broader occupational heat prevention programs. 

One widely recognized example is OSHA's Water. Rest. Shade. initiative. The program emphasizes access to fluids, opportunities for rest, and shaded recovery areas during hot working conditions. 

Studies evaluating workplace programs that incorporate these elements have reported improvements in hydration-related outcomes and reductions in markers associated with heat strain and kidney stress among agricultural workers. 

These findings have contributed to growing interest in multi-component approaches designed to address the various factors that influence heat exposure in occupational settings. 

How Cooling Strategies May Help Reduce Heat Strain 

In addition to hydration, researchers have examined a variety of cooling strategies designed to reduce physiological strain during work in hot environments. 

Air conditioning is often considered one of the most effective cooling methods, although it may not always be practical in outdoor workplaces, industrial facilities, or remote locations. 

As a result, many studies have evaluated alternative cooling approaches, including: 

• Shade structures 

• Electric fans 

• Cooling towels and garments 

• Cooling vests 

• Extremity cooling methods 

Research suggests these strategies may help reduce skin temperature, heart rate, and overall physiological strain during heat exposure. 

Researchers have also reported that cooling interventions may be most effective when they cover larger areas of the body, maintain lower temperatures, and remain in contact with the body for extended periods. 

Why Multiple Strategies May Be More Effective Than One 

Research examining occupational heat exposure often evaluates multiple interventions together rather than in isolation. 

Hydration, electrolyte replacement, rest opportunities, shaded recovery areas, and cooling methods each address different aspects of heat strain. As a result, many workplace heat management programs incorporate several approaches simultaneously. 

Studies suggest combining hydration and cooling interventions may produce greater reductions in physiological strain than either strategy alone. 

The effectiveness of any approach may vary depending on environmental conditions, workload, worker characteristics, and workplace practices. However, the occupational heat literature consistently highlights the importance of managing both fluid losses and heat exposure during physically demanding work. 

Understanding Heat Prevention Research 

Working in hot environments can place significant demands on the body. 

Research has associated occupational heat exposure with dehydration, increased cardiovascular strain, elevated body temperature, reduced work capacity, and increased risk of heat-related illness. 

Studies examining hydration, electrolyte replacement, cooling interventions, rest opportunities, and shaded recovery areas suggest these approaches may help reduce physiological strain during work in hot conditions. 

Fluids and electrolytes are commonly replaced through a variety of beverages and foods. Products such as Gatorade Thirst Quencher and Gatorade Zero are examples of beverages that can contribute fluids and electrolytes within broader hydration practices used during physically demanding activity. 

As temperatures continue to rise in many regions around the world, research examining strategies to manage occupational heat exposure may become increasingly important for understanding how heat affects worker health, safety, and productivity.