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Howard
J. Doss
Michigan State University
Farmers
and anyone working with organophosphate and carbamate pesticides
should get a baseline cholinesterase blood test now so their
physician can determine if a summertime illness is the result
of exposure to these pesticides.
It is
important that the test be taken before handling organophosphate
and carbamate pesticides to ensure that cholinesterase levels
will not be affected by a recent exposure to these chemicals.
Cholinesterase is an enzyme that is needed for the proper function
of the human body:s nervous system. Like humans, vertebrates
and insects (pests that are controlled with organophosphates
and carbamates) also have this same type of enzyme. Pesticides
in the organophosphate and carbamate chemical class contain
a cholinesterase inhibitor, which makes them effective in controlling
insects and other vertebrates (pests). Unfortunately, when people
breathe in these pesticides or it gets on their skin, they are
subjected to the same negative effect.
BODY?
The nervous system of the human body, as well as other vertebrates
and insects, uses electrical switching centers to make the system
work. These nerve endings are constantly sending signals carried
in a chemical called acetylcholine. When the signal completes
its function, cholinesterase in the body breaks down the acetylcholine,
terminating that function of the electrical signal so that part
of the body is ready for the next electrical command. If the
body:s cholinesterase level is decreased because of exposure
to organophosphates or carbamates, the cholinesterase fails
to function properly, causing the body:s nervous system to become
"jammed up" with unnecessary commands. The result of this jamming
is that the nervous system is constantly stimulated with commands
instructing it to perform certain functions, but not necessarily
in the proper sequence or at the right time.
The
health effects of this jamming from cholinesterase inhibition
can include headaches, dizziness, nausea, restlessness, anxiety,
mental confusion, shortness of breath, diarrhea, convulsions,
coma, and death.
For
the typical Michigan farmer, all pesticide application equipment
has been stored for several months, an indication that the farmer
has not been exposed to any pesticides since it was last used.
This break from handling pesticides has given the body time
to remake any cholinesterase destroyed by previous exposures
to organophosphates or carbamates.
During this absence from pesticides, the body:s cholinesterase
levels have returned to normal, so a physician can determine
a baseline through a blood test. This summer, if you develop
symptoms indicating that you have an illness that could be
the result of exposure to an organophosphate or carbamate
pesticide, your physician can compare your current cholinesterase
levels with baseline levels taken before the spraying season
began. This comparison provides the physician with information
that can confirm or refute pesticide exposure as the cause
of the illness.
According
to Kenneth Rosenman, MD, a Board Certified Internal and Occupational/Environmental
Medicine specialist for Michigan State University, a baseline
reading before and periodic testing of cholinesterase throughout
the spray season is also useful to determine if work practices
and protective equipment are adequate.
Rosenman
points out that a 20 percent decrease of cholinesterase from
baseline levels is an indication that a farmer needs to review
his or her work practices to minimize any potential health
effects. Symptoms typically don:t occur until more than a
50 percent decrease from baseline, with severe poisoning occurring
at a 90 percent decrease. At a 50 percent decrease from the
baseline the applicator should be removed from jobs involving
these pesticides until cholinesterase levels recover.
- Illustrations
courtesy of Fundamentals of Machine Operation, Agricultural
Safety, 1987, Deere and Company, Moline, Illinois.
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Disclaimer
and Reproduction Information: Information in NASD does not represent
NIOSH policy. Information included in NASD appears by permission
of the author and/or copyright holder. More
NASD Review: 04/2002
This
document is part of the Safety News Series, Agricultural Engineering
Department, Michigan State University Extension, East Lansing,
Michigan, 48824-1323. Publication date: March 1994.
Howard
J. Doss, Safety Leader, Agricultural Engineering Department,
Michigan State University, East Lansing, MI 48824-1323. Reviewed
by the MSU Extension Pesticide Education Coordinator. This
information is for educational purposes only. Reference to
commercial products or trade names does not imply endorsement
by the MSU Extension or bias against those not mentioned.
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