Which statement best describes WBGT and its contributing measurements?

• A. It uses the dry-bulb temperature, globe temperature, and humidity.
• B. It relies on ambient light levels.
• C. It is calculated from dry-bulb temperature and humidity alone.
• D. It uses dry-bulb temperature, wet-bulb, and globe temperatures.

Answer: (D)

WBGT is a heat-stress index that combines three environmental measurements to capture how hot it actually feels: air temperature, humidity/evaporative cooling, and radiant heat.

The dry-bulb temperature measures the ambient air temperature. The wet-bulb temperature accounts for humidity and how much cooling evaporation can provide. The globe temperature measures radiant heat from the sun and surroundings on a black globe. Together, these three measurements reflect the overall heat load on the body, including convection, evaporation, and radiation, which is why WBGT uses all three.

The other options miss one or more essential components: ambient light levels don’t directly quantify radiant heat exposure; relying on temperature and humidity alone ignores radiant heat; and humidity alone doesn’t capture evaporative cooling or radiant heat.