scope and cover greater portions of the farmworker population. Likewise, insufficient
funding prevents the development of new data collection systems that use more active
surveillance techniques to document problems that are rarely seen at clinical
facilities.^37
Monitoring Pesticide Exposure
Workers who apply and mix pesticides are at special risk of systemic pesticide ill-
ness. Both acute and chronic exposure can occur from spillage or by environmental
contamination of clothing. One serious health problem develops when cholinesterase
levels in the body drop to low levels after pesticide exposure. The resulting nervous
system malfunction produces pesticide-poisoning symptoms such as fatigue, light-
headedness, nausea, vomiting, headaches, and seizures. If levels decrease too much,
subsequent exposure to organophosphate or carbamate insecticides can result in
death.
Cholinesterase is an enzyme essential for normal functioning of the nervous sys-
tem. It inactivates the chemical messenger acetylcholine, which is normally active at
the junctions between nerves and muscles, between many nerves and glands, and at
the synapses or connections between certain nerves in the central nervous system.
Biological monitoring is the means by which absorption of a pesticide is proven.
This is in contrast to environmental or atmospheric monitoring, which reveals the
level of external contamination. In general, biological monitoring uses measurement
of pesticide levels in blood, urine, saliva, breath, or hair as an indication of the
amount of pesticide or other chemical that has been absorbed by all the routes of ex-
posure, such as inhalation, ingestion, or through the skin. Nevertheless, it should be
stressed that to evaluate workplace conditions on a continuous basis, emphasis should
be placed on environmental monitoring complemented by biological monitoring.
The latter has been found to be valuable in assessing the effectiveness of protective
clothing and respirators as well as a measure of worker compliance with safety
procedures.^38
A basic monitoring system would periodically test cholinesterase levels in the blood
of those at risk for cumulative exposure and insecticide poisoning. Blood samples can
be drawn at a clinic and sent to a laboratory for evaluation or the entire procedure
can be performed at the work site using field test kits. Workers shown to have dan-
gerously low levels are then identified and reassigned to prevent further exposures
until their depressed cholinesterase levels rise closer to normal levels.^39
The Washington State Experience
Medical Monitoring: Documenting Toxic Exposures and Their Consequences.
After nearly twenty years of struggle and a state supreme court victory, farmworkers
in Washington state who regularly handle organophosphate (OP) and carbamate
(CB) pesticides finally received medical monitoring in 2004. Blood tests were taken
before the spray season to establish each worker’s normal levels of cholinesterase,
Pesticides in Agriculture | 43