In warm temperatures, physical activity can raise the body’s temperature and put an individual at risk of severe harm.
Those who perform manual labor in hot outdoor conditions, such as agricultural and construction workers, are particularly at risk because they are subjected both to high levels of ambient heat and rising metabolic heat, which results from physical exertion.
The following are environmental risk factors for heat illness:
■ Air temperature above 90ºF
■ Relative humidity above 40 percent
■ Radiant heat from the sun and other sources
■ Conductive heat sources such as dark-colored work surfaces
■ Lack of air movement
■ Physical effort needed for the work
■ Use of non-breathable protective clothing and other personal protective equipment