Tri-county Occupational Health Consultants
AN UNKNOWN DANGER
Cholinesterase is a necessary enzyme in the blood, but each year many
people are reportedly exposed to toxic chemicals which inhibit this vital
enzyme. The function of the blood enzyme cholinesterase is to convert
acetylcholine back to choline and acetic acid. Acetylcholine is the
substance which is released from our nerves to activate muscles.
When cholinesterase is blocked, acetylcholine level continues to increase,
causing a build-up in the muscles. This overabundance of acetylcholine,
in turn, causes the muscle coordination to become jerky and irregular to
the point of muscle fibrillation. Simply put, cholinesterase is necessary
to ensure proper muscle function.
Cholinesterase inhibition should be suspected if there has
been a possible exposure to any carbamates or organophosphates - chemicals
most commonly found in herbicides and pesticides. Although the potential
for toxic cholinesterase inhibition may affect anyone from the avid homeowner
who desires an impeccable lawn or the weekend gardener, the highest incidence
is in the herbicide / pesticide industry.
There are over 100 herbicides/pesticides presently known to
contain carbamates and/or organophosphates which may inhibit cholinesterase.
The chemical names of some of the more common herbicides/pesticides used
today are Ronnel, Malathion, Diazinon, Dursban and Parathion. If
the names sound somewhat familiar, it is probably because they are found
as main ingredients in many over-the-counter preparations used by the general
public across the country to kill unwanted weeds in the driveway, on the
patio, and in the lawn.
The verification of suspected cholinesterase inhibition is
accomplished by measuring the plasma and red blood cell levels of the enzyme.
If either or both of the tests indicate a decreased level of cholinesterase,
inhibition has been validated. The lower the cholinesterase level,
the larger the intensity of the inhibition and the greater the degree of
The treatment is simply to remove the person from further exposure.
Bi-weekly blood tests should be done to monitor the gradual increase to
normal levels which takes 4-6 weeks. On rare occasions, usually after
severe inhalation, return to normal levels is slower than expected.
Chest x-rays or pulmonary function testing may be ordered to rule out pulmonary
Awareness of the possible health hazard is the first step in
a preventive program. If the potential for exposure is higher and more
constant as in most of the herbicide/pesticide industry, blood tests for
cholinesterase inhibition should be routinely performed to denote pre-symptom
early stages and to prevent cumulative effects of repetitive low-level
exposures. The typical company runs blood tests on all employees
in the early spring before any contact is made with the chemicals in question.
This baseline is important because some people have genetically low cholinesterase
levels which might prove deceptive when comparing future test levels usually
taken in mid-season and post-season. Some companies test for cholinesterase
levels every three to four weeks due to the amount of chemical contact
of their employees. Other companies, whose use of these chemicals
is not seasonal but rather year round, provide ongoing cholinesterase testing
for all their employees. Each program must be individual to that
company's needs and chemical usage.
The cost of cholinesterase testing varies greatly with the
laboratory chosen. Due to the expense of the materials required to
perform the specialty test, most local labs either do not have the necessary
materials or find the specialty of the test worth a higher charge.
For most needs, a specialty lab serves the company much better. The
blood samples can be drawn locally, prepared and sent to the specialty
lab for testing. The turn-around is usually one to two days with
the employer receiving a computer print-out of all the blood samples tested
and the cholinesterase levels of each. Because of the volume of tests
processed, specialty labs prepared to test for cholinesterase usually charge
between 60% to 65% less than the local lab which may receive few requests
for the tests.
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