What environmental factors contribute to heat stress?

• A. High ambient air temperature
• B. Low wind velocity
• C. High humidity
• D. All of the above

Answer: (D)

Heat stress occurs when the body's heat production plus the environmental heat load exceeds its ability to dissipate heat. High ambient air temperature raises the environmental heat load and narrows the gradient for heat to move from skin to air. Low wind velocity reduces convective cooling, letting warm air linger around the body. High humidity makes evaporative cooling less effective because sweat evaporates more slowly when the air is moist. Each factor separately hampers heat loss, and together they greatly increase heat strain, which is why the combination of high temperature, limited air movement, and high humidity best explains heat stress.