During what period do about 50-70% of outdoor fatalities occur while working in warm or hot environments?

The correct answer highlights that a significant number of outdoor fatalities in warm or hot environments predominantly occur during the first few days of exposure. This is primarily due to the body's physiological acclimatization process. When individuals are initially exposed to heat, they may not be adequately adapted to handle the stress caused by high temperatures. This inadequate acclimatization can lead to severe heat-related illnesses, such as heat exhaustion or heat stroke, which are life-threatening conditions.

As workers spend more time in hot conditions, their bodies gradually become more efficient at dissipating heat through mechanisms such as increased sweat production and improved blood flow to the skin. Consequently, the risk of fatal heat-related incidents tends to decrease as individuals adapt to the heat over a more extended period. In contrast, the other options refer to longer exposure durations, which typically correspond to reduced risk as acclimatization occurs.