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In 2004, the Washington State Department of Labor and Industries adopted a cholinesterase medical monitoring program. It requires that agricultural employers implement a monitoring program for their employees who, as part of their job, handle category I or II organophosphates and carbamates, with the words “Danger” or “Warning” on the label. (For details on the regulation, go to and search for “cholinesterase.”)

Handlers may decline testing only after they discuss the risks and benefits with a physician or licensed health care provider.

Since everyone has a different cholinesterase level in their blood, each participating handler must submit a baseline blood test followed by a periodic test after 30 hours of using the covered products. If the cholinesterase is depressed more than 20 percent from the baseline value, the employer must conduct a workplace evaluation.

In most cases, L & I will also conduct a workplace evaluation. If a red blood cell cholinesterase depression exceeds 30 percent or the plasma cholinesterase depression exceeds 40 percent, then the employee must be removed from handling the covered pesticides until the cholinesterase level returns to 80 percent of the baseline.

The figure below shows results of the first three years of testing. In each year, most of the handlers with follow-up tests and cholinesterase depressions worked in tree-fruit production. In 2006, 32 employers had at least one handler with a cholinesterase depression.

A significant cholinesterase depression can potentially cause pinpoint pupils, nausea, dizziness, headache, stomach pain, anxiety, muscle twitch or weakness, shortness of breath, diarrhea, convulsions, and/or coma. What constitutes a significant cholinesterase depression is unknown.

However, during the three years of the program, no participating handler, despite extensive scrutiny, has reported any symptoms of ill health. Medical providers also reported finding no health effects to handlers.

Cholinesterase depression

While L & I assumes that all handler cholinesterase depressions are linked to pesticides, a cholinesterase depression can be related to:

• laboratory handling;

• collection and/or storage of the blood sample;

• human variability;

• diet (potatoes and tomatoes are cholinesterase inhibitors);

• lifestyle factors;

• prescription medications;

• over-the-counter medications such as Tylenol;

• illegal drug use (cocaine, etc.);

• health status;

• alcohol use;

• tobacco (nicotine);

• infections; and

• other unknown factors.

Three of the work-removal depressions in 2006 continued after the workers stopped handling organophosphates, and so might not be pesticide-related.

During L & I consultations, the pesticide most often associated with depressions was chlorpyrifos (Lorsban), with azinphos-methyl (Guthion) a distant second. In 2006, 56 of the depressions were to plasma cholinesterase, which is particularly sensitive to chlorpyrifos. Two were depressions of red blood cell cholinesterase, which is sensitive to azinphos-methyl. Chlorpyrifos is not easily absorbed through the skin, but if personal protective equipment is not used correctly or decontamination is not done properly, it can be absorbed by inhalation, or by coming into contact with the mouth or eyes.

In 2005, 30 of the handlers with cholinesterase depressions used half-faced and 28 used full-faced respirators. In 2006, those with depressions included one handler (non-tree fruit) using an enclosed cab during application and a face shield during mixing and loading, and two using pressurized helmets. The rest used half-faced respirators.

Correctable actions

Most handlers used the same materials and application methods, and similar personal protection equipment, yet in 2005 and 2006 about 90 percent experienced no depressions, supporting the fact that current Worker Protection Standards and personal protection equipment work if used correctly. Every L & I consultation identified at least one of the following actions that may have contributed to a depression:

• Lack of proper decontamination of personal protection equipment before and after lunch, bathroom, or water breaks, etc.

• Overuse of spray cartridges and/or filters, or use of improper filter.

• Soap not used to decontaminate personal protection equipment.

• Respirator stored improperly. Clean respirator stored in the same zip-lock bag as a dirty cartridge or filter.

• Poor personal hygiene: failure to wash hands, neck, and face properly or at all.

• Use of cell phone during spray applications.

• Cotton absorbent baseball cap worn under hooded personal protection equipment and worn home uncleaned.

• Cotton hooded sweatshirt worn under personal protection equipment and worn home uncleaned.

• Leather boots that are not chemical-resistant worn, and worn home uncleaned.

• Part of spray suit worn while eating lunch.

• Cotton glove liners used and not washed after application.

• Washed contaminated tractor without using personal protection equipment.

• Had a runny nose so wore respirator around neck during application.

• Improper respirator fit. Constant adjustment created open sore on nose.

• Used face shield rather than respirator and splashed pesticide in eye.

• Submerged gloved hand to break up water-soluble packet, and spray entered glove.

• Medication used.

• Family history of liver disease and alcohol use.


The L & I consultation reports show the need for employers and/or supervisors to increase their observations of handler practices, especially during mixing/
loading, and decontamination to ensure handlers are following Washington Industrial Health and Safety Act (WISHA) and the federal Occupational Safety and Health Administration (OSHA) worker protection requirements and pesticide label instructions.

Over the first three years of the program, the number of employees needing to be tested has dropped. The number of employees found to have depressions also declined. Tree-fruit growers have taken a variety of steps to reduce potential exposure, including:

• Having additional organophosphate application duties.

• Adding more handlers to application crew.

• Scheduling applications to reduce individual handler hours.

• Reducing the number of organophosphate applications.

• Switching to other types of pesticides, and holding organophosphates in reserve.

• Using additional integrated pest management techniques.

• Converting to organic production system and organic pesticides.

• Improving supervision and training of applicators.


The program also showed the need to improve the coordination between Washington State Department of Agriculture, L & I, and agricultural industry groups to use the consultation results to enhance the educational efforts of Washington State University, state agencies, and employers.

No handler that has attended the WSU/WSDA Hands On Training and/or the Train the Trainer educational programs experienced a cholinesterase depression in 2006. For more information on those programs, contact: Flor Servin, WSDA pesticide safety educator, at 509-662-0590, or by e-mail at fservin@