Worker Health Study Summaries

Research on long-term exposure

Termite Applicators (Chloropyrifos Exposure)

2001

Study Background

In 1998, NIOSH conducted a variety of tests on the nervous system from 2 groups of persons. One group consisted of termiticide applicators who applied chlorpyrifos-containing insecticides to kill termites. The other group did not work with chlorpyrifos and was used as a comparison group.

Why did we do the study?

NIOSH did the study because some earlier studies suggested that working with chlorpyrifos is one of the leading causes of acute insecticide poisoning incidents

Chlorpyrifos may cause chronic neurologic effects

How did we do the study?

In 1998, NIOSH conducted a variety of tests on the nervous system from 2 groups of persons. One group consisted of termiticide applicators who applied chlorpyrifos-containing insecticides to kill termites. The other group did not work with chlorpyrifos and was used as a comparison group. We checked the neurologic function in each person by

• conducting clinical exams of the nervous system performed by two neurologists. The exam consisted of observation of eye movement, tremor, coordination, muscle tone, strength, sensation, and reflexes.
• conducting over 40 sub-clinical tests of nerve conduction velocity, arm/hand tremor, sensitivity to vision, smell, motor skills, or skills of memory and attention span
• looking at the level of TCP, a breakdown product of chlorpyrifos, in the urine
• performing a genetic test to see if some people are more susceptible to neurologic effects of chlorpyrifos

What did we find?

NIOSH found the following results when comparing termiticide applicators who applied chlorpyrifos to those persons in a comparison group who were not termiticide applicators:

The applicators did not differ significantly from the comparison group for any test in the clinical exam.

The applicators did not differ significantly from the comparison group for most of the 40 subclinical tests. The applicators performed significantly worse, however, on the pegboard turning (hand flexibility) and postural sway (body movement with eyes closed) tests.

The applicators reported significantly more symptoms than the comparison group. These symptoms included memory problems, emotional states, fatigue, and loss of muscular strength.

The eight applicators reporting having been poisoned by chlorpyrifos scored significantly lower on many of the clinical and sub-clinical tests than the comparison group.

We did not find any effect of being in one genetic group or another.

Summary Findings

Applicators had no clinical effects on the medical exam compared to non-applicators.

Applicators had few differences on sub-clinical tests compared to non-applicators.

Applicators had more self reported symptoms compared to non-applicators.

Applicators who reported past poisoning scored lower on many tests. Applicators should take every effort not to accidentally be exposed to a large amount of chlorpyrifos.

More Information

If you have any questions regarding the study, feel free to write to either:

North Carolina Department of Health and Human Services
Raleigh, NC 27626

National Institute for Occupational Safety and Health
4676 Columbia Parkway
Cincinnati, OH 45226

To receive the study report, NIOSH documents, or more information about occupational safety and health topics, contact NIOSH at

NIOSH Publications
4676 Columbia Parkway
Cincinnati, Oh 45226-1998
Phone: 800-356-4674
Fax: 513-533-8573
E-mail: pubstaft@cdc.gov
Web site: www.cdc.gov/niosh

Additional Resources

Steenland K, Dick R, Howell R, et al. (2000) Neurologic Function Among Termiticide Applicators Exposed to Chloropyrifos. Environmental Health Perspective 108:293-300 (Study Report).