Wet bulb globe temperature (WBGT)-to what extent is GT essential?

Background: Industrial and military safety personnel often require an easy, quick and accurate assessment of heat stress as a potential risk. The widely used WBGT index to evaluate heat stress is cumbersome and suited for a fixed site station rather than a mobile situation. Recently, a modified discomfort index (MDI) compiled from ambient temperature (Ta) and wet bulb temperature (Tw) was suggested to evaluate heat stress. Hypothesis: Validation of the simple and easy-to-operate MDI on an independent database can determine whether this index is able to serve as a reliable and valid alternative to WBGT. Methods: Four separate database sets obtained from the Marine Corps Training Site on Parris Island, SC, served to validate this index. Hourly weather measurements were collected daily during 4 yr, representing a wide range of environmental conditions. Results: The MDI validity was tested vs. the WBGT index. A highly significant correlation coefficient (r) greater than 0.95 (p < 0.001) was found in each of the four database sets. Conclusions: The simply constructed and user friendly MDI is easier to calculate and use than WBGT, and it has the potential to serve as an attractive alternative to the WBGT index n assessing heat stress.