Personal Rootzone: Heat stress

This month’s “Personal Rootzone”
is from Susan Haddock, UF/IFAS Extension, Commercial Horticulture and
Integrated Pest Management, Hillsborough County (FL):

Heat stress can be a major concern
for outdoor workers, especially during the summer months. Heat stress can
result in heat stroke, heat exhaustion, heat cramps, or heat rashes. Heat rash
and cramps are the mildest forms of heat stress. Heat exhaustion can occur when
workers are exposed to high temperatures, especially when combined with high
humidity and strenuous activity. Without treatment, heat exhaustion can lead to
life-threatening heat stroke. Workers can also be at greater risk of injuries
due to sweaty palms, fogged-up safety glasses, and dizziness. Learn how to
identify the symptoms and protect yourself and workers from heat stress.

Heat stress is the buildup in the
body of heat generated by the muscles during work, and from heat coming from
the hot work environment. When the body is overheated less blood flows to the
brain, muscles, and other organs. Because there is no pain, workers may not
realize when they become weak and tired, and that they are less alert and less
able to use good judgment. An increase in body temperature of 2 degrees F can
affect mental performance and an increase in 5 degrees F can cause serious
illness or death.

Signs and symptoms

  • Cool moist skin with goose bumps in the heat
  • Sweating
  • Headache
  • Fatigue
  • Dry mouth, dry membranes
  • No tears
  • No spit present
  • Muscle cramps
  • Weak rapid pulse (slow if person has fainted)
  • Nausea
  • Dilated pupils
  • Central nervous system depression
  • Loss of coordination
  • Confusion


How do managers prevent worker
heat stress concerns?

  • Assign a supervisor for heat stress management.
  • Train workers and supervisors in the prevention, recognition, and
    treatment of heat stress, and conduct safety meetings during heat spells.
  • Acclimate workers when they begin to work under hot conditions by
    assigning lighter workdays, longer rest periods, and watching workers’ response
    for 5-7 days.
  • Account for the conditions of work by checking weather conditions, how
    heavy the work is, and if the worker has to wear additional protective wear and
  • Account for the conditions of the workers by knowing if the worker has
    been sick, is rested, taking medications, or has consumed alcohol.
  • Manage work activities by setting up work breaks, rotating strenuous
    tasks, scheduling heavy work for cooler hours, and postponing non-essential
    tasks during heat spells.
  • Establish a drinking water program.
  • Provide additional measures such as special cooling and breathable
    clothing, prove shade, use air-conditioned mobile equipment, and modify
    pesticide usage to reduce the need for personal protective equipment (PPE).
  • Recognize that pesticide poisoning has similar, but some different,
    signs and symptoms such as moist membranes, salivation, tears, spit, slow
    pulse, nausea and diarrhea, possible small pupils, and coma. There can also be
    combined effects of heat stress and pesticide poisoning.
  • Take action and provide first aid if workers show signs and symptoms of
    heat stress.

General recommendations for
workers are to drink at least one cup of water every 30 minutes and greater
amounts as heat conditions become more extreme and workload level is more
strenuous, even if they are not thirsty. Drinking two or three cups of water
before work provides a head start, and they should continue drinking water into
the evening to replace all water lost through sweating. During extreme heat or
when wearing confining PPE, workers should be advised to drink a pint or more
of water before beginning work. Managers should be aware of workers who have
fluid retention or other medical problems that may affect the worker’s intake
of fluids. Also, managers should be aware of workers who, due to economic
pressure or toilet availability, tend to limit the amount of water they drink
or needed breaks.

Setting rest periods

Work and rest periods need to
consider workload levels, air temperature, humidity, sunlight conditions, and
worker clothing and PPE. Workers will recover better from heat with shorter,
more frequent breaks than longer, less frequent breaks. For heavier work in
higher temperatures and higher humidity, longer more frequent breaks are
needed. If possible, breaks should be taken in a shaded or air conditioned
area. In general, if performing heavy work at 95 degrees F with 30% humidity,
each hour of work should include a 15-minute break. Break times need to
increase and work times need to decrease significantly as temperature and
humidity increase. When air temperatures reach 105 degrees F, each hour of work
should include a 45-minute break.

For more information on heat stress, and setting work/rest periods and minimum water to drink refer to www.osha.gov/SLTC/heatstress/industry_resources.html