Revised Human Health Risk Assessment on Chlorpyrifos

EPA released an assessment of people's risks from the pesticide chlorpyrifos in December 2014. The assessment updated the June 2011 preliminary human health risk assessment based on new information including public comments. EPA factored in exposure from multiple sources and considered all populations in this revised assessment. Read more about chlorpyrifos.

To view EPA's revised risk assessment and related chlorpyrifos documents go to docket EPA-HQ-OPP-2008-0850 at www.regulations.gov. The public comment period opened on January 14, 2015, for 105 days. [Note: if the docket link does not take you to the chlorpyrifos documents, copy the docket information and enter it in the search box at regulations.gov. This issue occurs with some older browsers.]

Learn more about the revised risk assessment on chlorpyrifos:

  1. What does EPA's December 2014 human health risk assessment show?
  2. What are EPA's next steps?
  3. What is the registration status of chlorpyrifos?
  4. How did EPA assess risks?
  5. Did EPA take into account the 10X safety factor specified under the Food Quality Protection Act to protect children?
  6. Who is at risk for chlorpyrifos exposure?
  7. What would the signs or symptoms be for chlorpyrifos exposure?
  8. Can chlorpyrifos affect wildlife?
  9. What actions has EPA taken on chlorpyrifos?

1. What does EPA’s December 2014 human health risk assessment show?

This assessment shows some risks to workers who mix, load and apply chlorpyrifos pesticide products.  EPA also determined that there are potential risks for people whose drinking water comes from small water systems in heavily farmed areas where chlorpyrifos may be widely used. Based on this assessment, there were no additional risks from chlorpyrifos in food or exposure to bystanders and workers from airborne chlorpyrifos.

2. What are EPA's next steps?

EPA is developing appropriate measures to ensure that workers that use or work around areas treated with chlorpyrifos are protected and that drinking water in vulnerable watersheds is protected.

Based on the 2014 risk assessment, while dietary exposure to chlorpyrifos from food and residential exposure appears safe, when those exposures are combined with estimated exposure from drinking water in those watersheds, EPA could not conclude that the risk from aggregate exposure to chlorpyrifos meets the Federal Food, Drug, and Cosmetic Act (FFDCA) safety standard. As such, EPA issued a proposal on October 30, 2015, to revoke all chlorpyrifos tolerances.

Learn about the proposal and read the Federal Register Notice

As part of the ongoing registration review for chlorpyrifos, EPA is also assessing the ecological risks from chlorpyrifos in conjunction with the agency’s Endangered Species Protection Program; the results of the preliminary ecological risk assessment are expected later in 2015.

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3. What is the registration status of chlorpyrifos?

Chlorpyrifos remains registered as it is undergoes registration review. Registration review ensures pesticides will not cause unreasonable adverse effects when used according to label directions and precautions and that there is a reasonable certainty of no harm from dietary and residential exposure. This revised human health risk assessment contributes to understanding how chlorpyrifos may affect humans, an important part of the registration review process.

4. How did EPA assess risks? 

EPA assessed exposure from multiple sources including those from food, drinking water, pesticide inhalation and absorption of the pesticide through the skin for all populations, including infants, children and women of childbearing age. The assessment updates the June 2011 preliminary human health risk assessment based on new information received, including public comments and a new human response model.

This is one of the first risk assessments to employ a physiologically-based pharmacokinetic and pharmacodynamic (PBPK/PD) model. This is a mathematical model that enhances our ability to assess risk by allowing us to consider variations in a chemical’s effects on a person based on such variables as age and genetics and allows us to predict how the same dose may affect various members of a large population differently. EPA has held several meetings of the FIFRA Scientific Advisory Panel to get independent advice on the relevance and usefulness that a PBPK/PD model can provide in assessing a chemical’s risks and one specifically on PBPK/PD and chlorpyrifos.

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5. Did EPA take into account the 10x safety factor specified under the Food Quality Protection Act to protect children? 

Yes, EPA did retain the 10x factor for this risk assessment because of uncertainties regarding potential neurodevelopmental effects on children from prenatal exposure to chlorpyrifos.  EPA is continuing to evaluate whether its current regulatory approach sufficiently addresses the potential for adverse impacts on infants and children.

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6. Who is at risk for chlorpyrifos exposure?

We are concerned that safe levels of chlorpyrifos in the diet may be exceeded for people whose drinking water is derived from certain vulnerable watersheds in parts of the United States. This primarily includes those populations consuming drinking water from small water systems in heavily farmed areas where chlorpyrifos may be used widely. We are also concerned about workers who mix, load and apply chlorpyrifos to agricultural and other non-residential sites and workers re-entering treated areas after application.

EPA issued a proposal on October 30, 2015, to revoke all chlorpyrifos tolerances. Learn about the proposal and read the Federal Register notice.

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7. What would the signs or symptoms be for chlorpyrifos exposure?

At high enough doses, chlorpyrifos can cause cholinesterase inhibition in humans; that is, it can impact the nervous system causing nausea, dizziness, confusion, and at very high exposures (e.g., accidents or major spills), respiratory paralysis and death. Anyone who exhibits these symptoms should seek immediate help from a local hospital, physician, or nearest poison control center.

8. Can chlorpyrifos affect wildlife?

Yes, and EPA has taken actions to help protect wildlife from chlorpyrifos exposure.

For example, many of the reported incidents of wildlife mortality associated with chlorpyrifos use were related to residential lawn and termite uses and use on golf courses. The residential uses have been eliminated, termiticide uses have been restricted, and the application rate on golf courses has been reduced. Additionally, no-spray buffers around surface water bodies, as well as rate reductions for agricultural uses further reduced the environmental burden of chlorpyrifos.

The agency is currently assessing the ecological risks for chlorpyrifos in conjunction with the agency’s Endangered Species Protection Program.

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9. What actions has EPA taken on chlorpyrifos?

The EPA has taken a number of actions that have limited the use of chlorpyrifos since 2000. These actions include:

  • In June 2000, the Agency eliminated all homeowner uses, except ant and roach baits in child resistant packaging and fire ant mound treatments. In addition, termiticide uses were phased out.
  • In 2000, EPA required that all use of chlorpyrifos products in the United States be discontinued on tomatoes. The use on apple trees was restricted to pre-bloom and dormant applications. The grape tolerance was lowered to reflect the labeled dormant application.
  • In 2002, EPA restricted the use of chlorpyrifos on citrus and tree nuts as well other crops.
  • In 2012, EPA further limited the use of chlorpyrifos by significantly lowering pesticide application rates and creating “no-spray” buffer zones around public spaces, including recreational areas and homes.
  • EPA issued a proposal on October, 30, 2015, to revoke all chlorpyrifos tolerances. Learn about the proposal and read the Federal Register notice.

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