Chlorpyrifos

CAS# 2921-88-2

September 1997

Chlorpyrifos
C₉H₁₁Cl₃NO₃PS
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Agency for Toxic Substances and Disease Registry

This fact sheet answers the most frequently asked health questions (FAQs) about chlorpyrifos. For more information, call the ATSDR Information Center at 1-800-447-1544. This fact sheet is one in a series of summaries about hazardous substances and their health effects. It's important you understand this information because this substance may harm you. The effects of exposure to any hazardous substance depend on the dose, the duration, how you are exposed, personal traits and habits, and whether other chemicals are present.

HIGHLIGHTS: Chlorpyrifos is an insecticide which is widely used in homes and on farms. Breathing high levels of chlorpyrifos results primarily on nervous system effects, such as headaches, blurred vision, and salivation. Chlorpyrifos been found in at least 7 of the 1,430 National Priorities List sites identified by the Environmental Protection Agency (EPA).

What is chlorpyrifos?

Chlorpyrifos is an insecticide that is a white crystal-like solid with a strong odor. It does not mix well with water, so it is usually mixed with oily liquids before it is applied to crops or animals. It may also be applied to crops in a capsule form.

Chlorpyrifos is widely used in homes and on farms. In the home, it is used to control cockroaches, fleas, and termites; it is also used in some pet flea and tick collars. On the farm, it is used to control ticks on cattle and as a spray to control crop pests.

What happens to chlorpyrifos when it enters the environment?

Chlorpyrifos enters the environment through direct application to crops, lawns, and pets.
It may enter the environment in the home and workplace.
It may also enter the environment through volatilization, spills, and the disposal of chlorpyrifos waste.
Chlorpyrifos sticks tightly to soil particles.
It does not mix well with water, so it rarely enters local water systems.
Once in the environment, it is broken down by sunlight, bacteria, or other chemical processes.

How might I be exposed to chlorpyrifos?

Using it to control household pests such as fleas or cockroaches
Breathing air outside of homes where chlorpyrifos was applied to the ground around the foundation to control termites
Breathing air in a field where chlorpyrifos was sprayed on to crops
Touching soil in a field where it was sprayed
Breathing air near a waste disposal site which contains chlorpyrifos

How can chlorpyrifos affect my health?

Animal testing is sometimes necessary to find out how toxic substances might harm people or to treat those who have been exposed. Laws today protect the welfare of research animals and scientists must follow strict guidelines.

Breathing high levels of chlorpyrifos results primarily on nervous system effects, such as headaches, blurred vision, and salivation. It has also resulted in unstable blood pressure, diarrhea, nausea, and muscle cramps.

Ingesting very high concentrations of chlorpyrifos can cause paralysis, seizures, loss of consciousness, and death, while high concentrations can cause dizziness, runny nose, confusion, salivation, and rapid heart rate. It can also cause muscle weakness after the original symptoms have disappeared.

It is not known whether chlorpyrifos can affect reproduction or cause birth defects in people.

One animal study reported a decrease in the movement of sperm following exposure to chlorpyrifos, but it is not known if people would experience similar effects.

How likely is chlorpyrifos to cause cancer?

It is not known whether chlorpyrifos causes cancer in people. Animal studies have not shown that chlorpyrifos causes cancer. The EPA has determined that chlorpyrifos is a possible human carcinogen.

Is there a medical test to show whether I've been exposed to chlorpyrifos?

There is a general test that can be used to determine if you have been exposed to a group of insecticides, including chlorpyrifos. This test measures the activity of an enzyme called acetylcholinesterase in the blood.

There is also a test which measures a metabolite, or breakdown product, of chlorpyrifos in the urine. This test is accurate for several days after the exposure to chlorpyrifos occurred.

Has the federal government made recommendations to protect human health?

The EPA requires that spills or accidental releases into the environment of 1 pound or more of chlorpyrifos be reported to the EPA.

The EPA also recommends that children not drink water with chlorpyrifos levels greater than 0.03 milligrams per liter of water (0.03 mg/L) for 1–10 days exposure.

The Food and Drug Administration (FDA) has set tolerances for chlorpyrifos for agricultural products ranging from 0.05 to 15 parts chlorpyrifos per million parts of food (0.05–15 ppm).

Glossary

Carcinogen:: A substance with the ability to cause cancer
CAS:: Chemical Abstracts Service
Ingest:: To eat or drink something
Insecticide:: A substance that kills insects
Milligram (mg):: One thousandth of a gram
Pesticide:: A substance that kills pests
PPM:: Parts per million
Volatilization:: To easily change into a vapor or a gas in the environment

Reference

Agency for Toxic Substances and Disease Registry. 1996. Toxicological profile for chlorpyrifos (update). Atlanta, GA; U.S. Department of Health and Human Services, Public Health Service.

Where can I get more information?

ATSDR can tell you where to find occupational and environmental health clinics. Their specialists can recognize, evaluate, and treat illnesses resulting from exposure to hazardous substances. You can also contact your community or state health or environmental quality department if you have any more questions or concerns.

For more information, contact:

Agency for Toxic Substances and Disease Registry
Division of Toxicology
1600 Clifton Road NE, Mailstop E-29
Atlanta, GA 30333
Phone: 1-800-447-1544
Fax: 404-639-6359

U.S. Department of Health and Human Services
Public Health Service
Agency for Toxic Substances and Disease Registry

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