Working in Heat

"Heat stress can affect many outdoor and indoor workers. To prevent heat-related illnesses (HRI) and injuries, employers should develop and use a comprehensive heat-related illness prevention program at the workplace.

In occupational settings, heat stress is the combination of the heat your body produces (metabolic heat), environmental factors (for example, temperature and humidity), and clothing and personal protective equipment (PPE). While many workers need to wear PPE for protection from workplace chemical, physical, and biological hazards, PPE can increase the risk for HRIs. PPE can often alter the rate and amount of heat exchange between the skin and air. For example, impermeable materials used for protection against chemical hazards can be very hot to wear, as they trap heat close to the skin and prevent sweat evaporation.

Below are some elements for addressing heat stress that need to be included in workplace HRI prevention programs.

Control of Heat Stress

Employers should reduce workplace heat stress by implementing engineering and work practice controls.

Engineering controls might include those that:

• Increase air velocity (if air temperature is below 95°F).
• Use reflective or heat-absorbing shielding or barriers.
• Reduce steam leaks, wet floors, or humidity.

Work practice controls include the following:

• Implement a buddy system and routinely check workers to ensure they make use of available water and shade, and they do not have symptoms of an HRI.
• Monitor the weather.
• Limit time in heat and/or increase rest time in a cool environment.
• Increase the number of workers per task.
• Require workers to conduct self-monitoring.
• Implement a heat alert program when a heat wave is likely..."
  Heat stress 

Heat stress in U.S. may double by century's end

"Periods of extremely high heat are projected to double across the lower 48 states by 2100 if the world continues to emit high levels of greenhouse gases, according to a new study in Earth's Future, an American Geophysical Union journal.

The heat stress will be felt most strongly in areas with growing populations. The Pacific Northwest, central California and the Great Lakes region could experience as much as a threefold increase compared to the past 40 years. Heat stress occurs when both the temperature and relative humidity get high enough that the human body can't rid itself of the excess heat, leading to strokes, heat cramps and other health problems.

"Without doing any mitigation strategies, the impact of heat stress is likely to increase," said Ashok Mishra, a civil engineer at Clemson University and an author of the U.S. National Science Foundation-funded study.

Human-driven climate change is leading to an average increase in temperatures across the world. However, people don't necessarily notice a slow, even warming as much as an extreme event.

Mishra and co-authors wanted to see how heat stress would increase at the same time as a general increase in temperature and relative humidity. They assumed that while humans may experience higher temperatures on average in many areas, people will acclimatize to the new normal, but extremely high heat index peaks, above even the yearly median values, will continue to have negative impacts on human health.

While previous research has usually examined how extreme heat events may increase in severity, frequency and duration, most studies have looked at one of these in isolation. Mishra and his colleagues calculated how all these might increase together in the future under a high emissions scenario..."
Heat stress