How do these symptoms develop?
When metabolism generates heat
faster than needed, adjustments begin in
the circulatory system. The heart pumps
faster and blood vessels dilate (expand)
to bring more blood to surface layers of
skin, fromwhich the heat it carries is conducted,
convected, and radiated to the
cooler environment. This shift in flow
slows the delivery of nutrients and oxygen
to muscles, brain, and other organs,
reducing strength, alertness, and stamina.
If a body cannot cool fast enough this
way alone, or when the air is warmer
than the skin, it resorts to sweating,
which dissipates heatmore quickly but at
further cost to circulation.
Sweat glands draw water from the
bloodstream. The longer that sweating
goes on, the less blood volume remains
to serve cooling and other body functions,
and the greater the risk of experiencing
symptoms of heat illness.A150-
lb. person performing moderately
active work in warm weather, for
example, would lose about ¾ quart of
water, or 1% of body weight, per hour.
At that rate, without replacing any of
the lost fluid, one would feel a notable
loss of energy and endurance after
three hours, have serious fatigue and
nausea after six hours, and lose consciousness
after eight hours.
Keys to prevention
Research in sports, exercise, military,
and industrial settings has yielded
applicable lessons about heat stress.
Not surprisingly, the preventive measure
that these studies most strongly
recommend is to steadily replenish the
fluid that the body loses as sweat.
Because thirst signals a water deficit
only after it begins to affect performance,
starting to drink before or early in awork
day is safer thanwaiting to feel the need.
Small amounts frequently are better than
a large amount at once. The amount of
water needed to replace loss through
sweating is a function of work-strenuosness
and pace, weather, and personal
At most vineyards, water in an
Igloo® or similar container is available
to employees throughout the day.
Observations from two field studies
and talks with numerous managers,
however, are that production workers
tend to visit the Igloo® infrequently,when
quite thirsty and that they drink large
quantities on each visit. This pattern
results in a low volume and poor rate of
fluid replenishment during the day.
When workers do not drink as
much or often as they need, it is typically
because they perceive high
“costs” to obtain the water that is provided
relative to its value to them.
Impediments to Igloo® access can
include physical effort, supervisory
or co-worker disdain, foregone earnings
opportunity when on piece-rate
pay, and fear of ingesting microbes
from the water or container. For both
workers and managers, putting too
low a priority on fluid replacement
may stem from limited knowledge of
how the body generates and copes
with internal heat.
Without understanding the reasons
behind advice to drink water frequently,
workers are not as equipped
ormotivated as they should be for their
part in combating heat stress, and
supervisors are less apt to assist them
with logistical support, information,
and personal example.
California regulation basics
California became the first state in
the U.S. with a workplace safety rule
on occupational heat illness in 2005.An
emergency standard adopted in 2005
was replaced by a permanent regulation
in 2006. Cal/OSHA published its
interpretation and enforcement guidelines
on several points in March 2009.
The Heat Illness Prevention (HIP)
Standard (CA Code of Regulations, Title
8, Chapter 4, Subchapter 7, Group 2,
Article 10) now applies to all outdoor
workplaces in California, all the time. In
brief, it requires employers of peoplewho
work outside to provide four things:
- One quart of drinking water per
person-hour for the entire work shift;
- Ashaded rest area and the opportunity
to use it five minutes or more;
- Training on nine specific topics for
all employees, and on an additional
two for supervisors; and
- Written documentation of procedures
to be followed in complying
with the regulation.
Definitions in the regulation text
and interpretations in a Q&A document
from Cal/OSHA elaborate on
these requirements and instruct
enforcement personnel. Regarding
water, unless a plumbed or other continuous
supply is readily available to
workers, the whole amount is to be
provided in portable containers either
at the beginning of the shift or in stages
through a reliable system of replenishment
that allows all employees to
drink at least one quart per hour.
Employers are considered out of
compliance if at any time no drinking
water is available, or if the replenishment
practice is to wait until either the
container is empty or employees
request more water. Cal/OSHA sees a
replenishment system as unreliable if
employees feel pressured to reduce
their water consumption in order to
conserve for later in the day.
Shade, according to the regulation, is
blockage of direct sunlight. It can be provided
by buildings, canopies, awnings,
“popup” or other temporary structures,
and even trees. A shaded area that is too
hot to allowthe body to cool is not acceptable.
Access to shade is to be permitted at
all times to any employee “suffering from
heat illness or believing a preventive
recovery period is needed” (even prior to
Cal/OSHA has adopted temperaturetriggers
in 2009 for portable shade structures
to be in place before any worker
requests. Inspectors expect to find shade
existing and available at the start of a shift
if theNationalWeather Service forecasts a
daily high above 85º F or immediately if
the temperature reaches 90º F.
While it does not specify training
methods, Cal/OSHA says that evaluation
of compliance will also depend on
manner of presentation, and that
enforcement personnel will quiz
employees in assessing whether an
employer has made a good faith effort
to convey essential content.
Topics required in training for all
- Environmental and personal risk
factors for heat illness;
- Importance of frequent water consumption,
especially when weather is
hot and sweating is more than usual;