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 The "heat index" is a measure of how hot it really feels when
humidity is taken into account. U.S. occupational safety standards
warn that workers are at risk of heat stress when the heat index
reaches 91 degrees Fahrenheit (32.8 degrees Celsius) or higher.
But an analysis of 25 incidents of outdoor worker illnesses and
deaths shows that the risk can rise at a heat index of just 85
degrees F (29.4 C), researchers say. Six deaths happened at heat
indexes below 90 degrees F, they note.
"Heat-related illnesses can and do occur on days that aren't
particularly hot. An average summer day, with a temperature in the
80s, can fatally injure workers if proper precautions are not
taken," said lead author Dr. Aaron Tustin of the U.S. Department of
Labor's Occupational Safety and Health Administration (OSHA) in
Washington, D.C.
"When working in warm or hot weather, take precautions to avoid heat
stroke," Tustin told Reuters Health by email. "Don't wait until the
temperature is above 90."
Ideally, employers would monitor all the factors included in OSHA
guidelines, such as the so-called wet bulb globe temperature, which
is a precise measure of environmental heat, as well as how strenuous
the work is, work clothing and equipment, the effects of direct
sunlight and other conditions at the work site.
But, the study team notes in CDC's Morbidity and Mortality Weekly
Report, "Employers often obtain heat index information from publicly
broadcasted weather reports or forecasts that do not necessarily
reflect conditions at their work sites."
Tustin and colleagues from the CDC and OSHA reviewed 25 incidents of
outdoor occupational heat-related illnesses, including 14 deaths,
that were investigated by OSHA between 2011 and 2016.
The researchers found that heat stress exceeded exposure limits in
all 14 deaths and in 8 of the 11 non-fatal illnesses. But in six
cases of death, temperature alone was not the only factor that came
into play and the actual heat index during those incidents was below
90 degrees F.
When data about all the conditions at the work site is unavailable,
the researchers recommend using a heat index of 85 degrees F as a
threshold for potentially hazardous worker heat stress.
"Heat stress is a common and under-appreciated workplace hazard,"
said Thomas Bernard of the University of South Florida College of
Public Health in Tampa, who wasn't involved in the study.
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"Outdoor workers in agriculture and construction are especially
vulnerable," Bernard said in a phone interview. "In the summer, any
location in the U.S. could be open to serious illnesses or
fatalities."
Heat stroke, which happens when the body overheats to an internal
temperature of 103 degrees Fahrenheit or higher, is the most serious
heat-related illness, according to the Centers for Disease Control
and Prevention (CDC). Brain, nerve and organ damage can happen if
the person does not receive fast medical attention and treatment to
cool the body down.
"We're all exposed to heat stress but have a low sense of risk about
what it can do because it's in our common experience," Bernard said.
"But the data points to the fact that there's not a large margin
between what we can tolerate and what causes serious problems."
To prevent heat stress that leads to heat-related illness, the CDC
generally recommends certain minimums for hydration, rest breaks and
acclimatization.
A comprehensive heat-related illness prevention program should
include an acclimatization schedule for newly hired workers and
unacclimated long-term workers, as well as training for workers and
supervisors about symptom recognition and first aid such as
aggressive cooling of heat stroke victims before medical
professionals arrive. Employers should also consider engineering and
administrative controls to reduce heat stress.
"Heat stress is preventable, and we need to be prepared with ways to
protect folks who are working outside in the heat," said Dr. June
Spector of the University of Washington in Seattle, who wasn't
involved in the study.
"We've had quite a bit of hot weather recently across the country,
so this issue is on people's minds," Spector said in a phone
interview. "We need to continue to increase awareness."
"Accidents are happening, workers are getting injured, and harm is
being done to the environment," Bernard said. "When the heat index
goes above 80/85 degrees, all of these risks begin to increase."
SOURCE: https://bit.ly/2meBVHs MMWR, online July 6, 2018.
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