We’ve included some of the questions we hear from our stakeholders and in the media regarding chlorpyrifos. Follow links to get more detail or visit our Resource Library to see the research and discussion informing the answers to the questions below.

Benefits and Use

Which crops are protected by chlorpyrifos?

Chlorpyrifos protects a wide variety of pests on a wide variety of crops. The six most critical crops protected, in terms of their agricultural and economic significance are soybeans, citrus, grapes, tree nuts, field corn, and alfalfa. Visit our Important Crops page to learn why each of these crops is significant and why chlorpyrifos is important to their protection from insect pests.

To learn about the regions of the U.S. for which these crops are important and to read growers’ and entomologists’ perspectives about the importance of chlorpyrifos to the survival of key regional crops, visit Where It’s Used.

Does chlorpyrifos harm beneficial insects?

Chlorpyrifos does less harm to beneficial insects than a number of other commonly-used pesticides. Chlorpyrifos is often used as a part of an Integrated Pest Management program for that very reason. Read more on the Target Pests page of our Benefits and Use section of the site.

Was chlorpyrifos banned from home use?

No. During 2000, Dow AgroSciences and all other chlorpyrifos registrants reached a voluntary agreement with the EPA for a phase out of residential uses of chlorpyrifos. Read more about chlorpyrifos’ removal from residential uses on the Responsible Use page of the Benefits and Use section of this site.

How is spray drift from chlorpyrifos managed?

Chlorpyrifos labels provide guidance on application practices and equipment intended to minimize offsite spray drift. This labeling was created in response to changes to regulatory policy and to improve scientific monitoring and assessments. For more discussion and related research links, visit the Managing Use page in our Wildlife & Environment section and the Responsible Use page of the Benefits and Use section.

For a discussion of the potential impacts of proposed new restrictions, please visit the Proposed Restrictions page in Wildlife & Environment.

Human Health

What does “allowable exposure” mean for pesticides?

EPA establishes both long-term and short-term exposure standards for humans based, in part, on laboratory animal testing and other scientific assessments. These standards are conservatively set well below the level at which any damage should occur through ingestion, inhalation, or absorption through the skin.

Visit the pages under our Human Exposure section of the site to learn more about the biological effects scientists use to base their assessments, what the exposure limits are for chlorpyrifos, and what new data are influencing how scientists look at human exposure to chlorpyrifos.

Are chlorpyrifos residues on fruits and vegetables harmful to consumers?

The trace residues likely to be found on fruits and vegetables with labeled use of chlorpyrifos have been – and continue to be – studied and monitored so that they fall well within EPA standards for acceptable exposure. Read more on the Consumers page in the Human Health section of this site.

Does chlorpyrifos cause birth defects, ADHD, or developmental disorders in children?

The weight of the evidence of years – in some cases, decades – of scientific study continues to demonstrate that there is no link between chlorpyrifos and any of these health concerns. Human Health questions are discussed in more detail in the Health Questions section of this site.

Was chlorpyrifos used in wartime nerve gas?

No. Chlorpyrifos has never been used as a wartime nerve gas. It is a distinct chemical with different properties from those with military purposes.

For a discussion of how chlorpyrifos works on target pests, visit the Biological Effects of the Human Health section of this site.

Wildlife & Environment

Does chlorpyrifos break down in the environment?

Chlorpyrifos is a degradable pesticide. It is broken down in various ways – from microbial activity or exposure to sunlight or other chemical processes. Get more detail about chlorpyrifos’ persistence and breakdown in the environment.

How is chlorpyrifos tested to help ensure limited impact to wildlife?

Chlorpyrifos undergoes several types of testing, including laboratory studies, predictive assessments, and field studies. Read more about testing approaches for pesticides and chlorpyrifos’ exposure and effects on wildlife.

What are the best ways to use chlorpyrifos to minimize effects on the environment and wildlife?

The foundation of “good agricultural practice” is simply to use only the amount of pesticide needed – and no more than that. Product labeling contains specific advice for application rate and frequency, as well as waiting periods between applications. Because labeling is complex – by crop, by pest, and by environmental conditions – it would be impossible to detail here. Always follow label directions when using any pesticide.

You can also visit our Managing Use page for a general discussion of the kinds of safeguards in place to protect the environment or our Responsible Use page for a similar discussion of how use is restricted and monitored for protecting people.

How does the Endangered Species Act affect chlorpyrifos registration review?

The Endangered Species Act (ESA) has had significant impact on regulatory process and could still have an impact on how and where chlorpyrifos is used for protecting crops. In fact, current debates regarding its alleged effect on Pacific salmon – as well as the definitions of “salmon habitat” – have resulted in proposed restrictions that could significantly impact the production of key crops, such as citrus and tree nuts, as well as the livelihoods of growers and agricultural products manufacturers.


Visit our Endangered Species section for detailed discussion of the debate and some of its possible outcomes.


Regulatory Process

What is EPA registration review?

Registration review is an ongoing, cyclical process for periodic review of every pesticide active ingredient registered in the United States with the Environmental Protection Agency. Although each pesticide is different, they all follow the same general process, from creating a docket through final registration decision.

Learn more about EPA Registration Review and the review process in our Regulatory section of the site.

How long does registration review take?

Registration review takes years to complete. It is a complex process, requiring scientific assessments, reports, and input from a variety of agencies, services, and other interested parties, such as agricultural associations, academics, and industry experts. Chlorpyrifos registration review began in 2009 and is currently on track to be completed sometime in 2015.

View EPA’s work plan for chlorpyrifos registration review in the Regulatory section of this site.

Is there an opportunity to provide input into chlorpyrifos’ registration review?

Yes. It’s called an “open comment period,” during which members of the public can post comments to the EPA docket for chlorpyrifos. There have already been open comment periods for chlorpyrifos, but there will be others in the schedule before the final registration review decision is reached.

See the chlorpyrifos schedule for registration review.

Learn more about how to participate in an open comment period for chlorpyrifos.