Chlorpyrifos is an organophosphate insecticide, acaricide and miticide used primarily to control foliage and soil-borne insect pests.
On Feb. 25, 2022, EPA released a response denying the objections, requests for hearing, and stay requests filed on the final rule revoking all “tolerances” for chlorpyrifos, which establish an amount of a pesticide that is allowed on food. Read EPA's response. In addition, the Agency issued letters to the registrants of chlorpyrifos for products with registered food uses confirming that tolerances will expire as of Feb. 28, 2022, and requesting registrants act to cancel these uses. For registrations not voluntarily cancelled, EPA intends to issue a Notice of Intent to Cancel under the Federal Insecticide, Fungicide and Rodenticide Act to cancel registered food uses of chlorpyrifos associated with the revoked tolerances. Read EPA's statement.
- Basic information
- Using chlorpyrifos products safely
- EPA actions and regulatory history
- EPA action on the Federal Food, Drug, and Cosmetic Act (FFDCA) petition and litigation
- Registration review schedule
- EPA action under the Endangered Species Act (ESA)
- Additional information
Chlorpyrifos has been used as a pesticide since 1965 in both agricultural and non-agricultural areas. On Feb. 28, 2022, all chlorpyrifos tolerances will expire pursuant to the final rule. Therefore, chlorpyrifos application to food commodities results in food being considered adulterated; distribution of adulterated food in interstate commerce is unlawful under the FFDCA. Non-agricultural, non-food uses are unaffected by the final tolerance rule, but will be considered as EPA completes its registration review of this chemical.
Non-food products are sold as liquids, granules, water-dispersible granules, wettable powders, and water-soluble packets, and may be applied by ground equipment.
In accordance with the Federal Insecticide, Fungicide, Rodenticide Act (FIFRA), EPA only registers a pesticide when it determines that it will not cause unreasonable adverse effects on humans or the environment, while considering the economic, social, and environmental costs and benefits of the use of the pesticide. EPA reviews and approves label directions to ensure that pesticides can be used without posing unreasonable adverse effects to the environment, including ensuring that the use will not result in dietary risk inconsistent with the FFDCA safety standard.
The key to ensuring that the pesticide will not cause unreasonable adverse effects is for all users to read and closely follow the label directions.
The current chlorpyrifos labels require workers handling and applying chlorpyrifos to wear additional personal protective equipment (chemical resistant gloves, coveralls, respirators).
Since its first registration in 1965, chlorpyrifos has been reviewed several times by EPA for tolerance reassessment, reregistration, and most recently, as part of its ongoing registration review. The following timeline summarizes the work EPA has done to ensure that, as science and technology evolve, registered chlorpyrifos products remain safe for use.
2000 – Voluntary Agreement to Eliminate, Phase Out and Modify Certain Uses
In 1996, the Food Quality Protection Act (FQPA) set a more stringent safety standard to be especially protective of children. After finalizing the chlorpyrifos risk assessments for reregistration, EPA identified the need to modify certain chlorpyrifos uses to meet the revised standard of safety, and to address health and environmental risks from chlorpyrifos exposure. In 2000, the registrants of chlorpyrifos voluntarily entered into an agreement with EPA to eliminate, phase out, and modify certain uses. Some examples of the voluntary cancellations and modifications in the agreement include:
- Eliminating most homeowner uses, except ant and roach baits in child resistant packaging and fire ant mound treatments, and phasing out all termiticide uses.
- Discontinuing all uses of chlorpyrifos products in the United States on tomatoes, restricting use on apples to pre-bloom and dormant application, and lowering the grape tolerance (maximum residue level) to reflect the labeled dormant application.
2002 – Label Changes to Ensure Environmental and Worker Safety
In 2002, EPA made a number of changes to the required safety measures that improved safety for the environment and for those applying this pesticide including:
- Use of buffer zones to protect water quality, fish and wildlife;
- Reductions in application rates per season on a variety of crops including citrus and corn; and
- Increase in amount of personal protective equipment to mitigate risk to agricultural workers.
Read the 2006 Registration Eligibility Decision (RED) for chlorpyrifos, which finalized the 2002 Interim RED, and includes an overview of the chlorpyrifos human health risk assessment for reregistration.
2011 – Preliminary Human Health Risk Assessment
In 2011, as part of the registration review process, EPA completed a comprehensive preliminary human health risk assessment for all chlorpyrifos uses. This assessment included the results of extensive new research and the findings of a number of new studies that had become available since the Agency’s last human health risk assessment for chlorpyrifos, completed in June 2000.
2012 – Spray Drift Mitigation and Changes to Application Rates
In 2012, EPA significantly lowered the aerial pesticide application rates and created “no-spray” buffer zones for ground, airblast and aerial application methods around public spaces, including recreational areas, schools, homes and other sensitive areas to be protective of children and other bystanders.
2014 – Revised Human Health Risk Assessment
In 2014, as part of the registration review process, EPA completed a revised human health risk assessment for all chlorpyrifos uses. The assessment updated the June 2011 preliminary human health risk assessment based on new information received, including public comments. EPA factored in exposures from multiple sources including from the exposures from food and water, from inhaling the pesticide and through the skin. EPA considered all populations including infants, children, and women of child-bearing age. EPA incorporated information from a 2012 assessment of spray drift exposure and as well as new restrictions put into place to limit spray drift.
2016 – Revised Human Health Risk Assessment
After receiving public comments on the 2014 risk assessment and feedback from the FIFRA Scientific Advisory Panel (SAP), EPA revised its human health risk assessment for chlorpyrifos in 2016, which was published subsequent to the issuance of the proposed rule, and retained the 10X FQPA Safety Factor.
2020 – Draft Ecological Risk Assessment and Revised Human Health Risk Assessment
In Sept. 2020, EPA issued the following assessments: Chlorpyrifos: Draft Ecological Risk Assessment for Registration Review, the Chlorpyrifos: Third Revised Human Health Risk Assessment for Registration Review, and the Updated Chlorpyrifos Refined Drinking Water Assessment for Registration Review.
The draft ecological risk assessment describes the ecological risks posed by the current uses of chlorpyrifos in the context of FIFRA, by providing a range of screening risk quotients. In the 2020 Third Revised Human Health Risk Assessment, EPA utilizes the same endpoint and points of departure as those used in the 2014 human health risk assessment. This was done because the Agency concluded that the science addressing neurodevelopmental effects remained unresolved and further evaluation of the science during the remaining time for completion of registration review was warranted.
While in the 2020 revised human health risk assessment the Agency determined that risks from exposures to chlorpyrifos residues in food were not of concern, drinking water exposures significantly add to those risks. When considering the drinking water contribution from all currently registered uses, the Agency’s levels of concern are exceeded when combined with food and residential exposures.
Due to the large number of files in support of the Updated Chlorpyrifos Refined Drinking Water Assessment for Registration Review, instructions to access to those attachments are provided below. Download and Unzip Instructions:
- Hover over the file name, right-click the file link.
- Save file to a local directory following displayed instructions.
- To unzip all the contents of the zipped folder, right-click the zip file, select Extract All, and then follow the instructions.
- When accessing additional zip files within the subfolders, step 3 will need to be repeated.
- Attachment 1 - Master Use Summary (PDF)(14 pp, 640 K)
- Attachment 2 - Usage Files (ZIP)(1 pg, 2.5 MB)
- Attachment 3 - (Modeling Input and Output Files) PCA Analysis (XLSX)(1 pg, 12.9 MB)
- Attachment 3 - (Modeling Input and Output Files) PCA-PCT Aggregate Analysis, Upper Bound HUC04 (ZIP)(1 pg, 198.9 MB)
- Attachment 3 - (Modeling Input and Output Files) PCA-PCT Aggregate Analysis, Upper Bound HUC07a (ZIP)(1 pg, 198.9 MB)
- Attachment 3 - (Modeling Input and Output Files) PCA-PCT Aggregate Analysis, Upper Bound HUC07b (1 of 2) (ZIP)(1 pg, 615 MB)
- Attachment 3 - Modeling Input and Output Files) PCA-PCT Aggregate Analysis, Upper Bound HUC07b (2 of 2) (ZIP)(1 pg, 541.8 MB)
- Attachment 3 - (Modeling Input and Output Files) PCA-PCT Aggregate Analysis, Upper Bound HUC09 (ZIP)(1 pg, 138.6 MB)
- Attachment 3 - (Modeling Input and Output Files) Chlorpyrifos SIAB Use and Usage Matrix (XLSX)(1 pg, 143 K)
- Attachment 3 - (Modeling Input and Output Files) PWC Average Use Rates (1 of 2) (ZIP)(1 pg, 121.2 MB)
- Attachment 3 - (Modeling Input and Output Files) PWC Average Use Rates (2 of 2) (ZIP)(1 pg, 110.7 MB)
- Attachment 3 - (Modeling Input and Output Files) PWC Average Upper Bound Rates (1 of 2) (ZIP)(1 pg, 125.9 MB)
- Attachment 3 - (Modeling Input and Output Files) PWC Average Upper Bound Rates (2 of 2) (ZIP)(1 pg, 106.8 MB)
- Attachment 4 - Monitoring Data Files (ZIP)(1 pg, 736.4 MB)
2020 – Proposed Interim Decision
In Dec. 2020, EPA released the Proposed Interim Decision for the Registration Review of Chlorpyrifos for a 60-day public comment period. EPA also invited comments on the benefits assessments, the Sept. 2020 revised human health risk assessment, draft ecological risk assessment, and revised drinking water assessment. By holding the comment period at the same time, the public had access to more information and could provide more informed, robust comments. On Feb. 5, 2021, EPA extended the public comment period for an additional 30 days until Mar. 7, 2021. EPA is currently reviewing public input and will respond to comments prior to issuing an interim decision.
2007 FFDCA Petition
In Sept. 2007, environmental advocacy organizations submitted a petition to EPA under FFDCA, requesting that EPA revoke all chlorpyrifos tolerances and cancel all chlorpyrifos registrations.
2015 Proposed rule to revoke tolerances
In 2015, EPA proposed to revoke chlorpyrifos tolerances. (80 FR 69080 (Nov. 6, 2015)). Based on data available at the time, the Agency concluded that it was unable to make a safety finding as required under FFDCA due to exposure to drinking water in certain watersheds. EPA acknowledged that it was continuing to work on additional hazard analysis and refinements to its drinking water assessment. Then in 2016, EPA revised its human health risk assessment and drinking water exposure assessment. The Agency sought additional comment on those documents, which provided further support for the tolerance revocation proposal (81 FR 81049 (Nov. 17, 2016)).
2017-2019 – Denial of Petition to Revoke Tolerances
In Mar. 2017, EPA denied a petition that asked us to revoke all pesticide tolerances for chlorpyrifos and cancel all chlorpyrifos registrations. The Agency concluded that despite several years of study, the science addressing neurodevelopmental effects remains unresolved and further evaluation of the science during the remaining time for completion of registration review is warranted. As a part of the ongoing registration review, the Agency stated that it would continue to review the science addressing neurodevelopmental effects of chlorpyrifos.
Several parties filed objections to EPA’s denial of the petition. The Agency responded, by issuing an order denying those objections. EPA concluded that the data provided with the 2007 petition was not sufficiently valid, complete, and reliable to support the request for revocation.
Ninth Circuit litigation
Environmental advocacy groups and several States challenged EPA’s denial orders in the U.S. Court of Appeals for the Ninth Circuit. In Apr. 2021, the Ninth Circuit issued its decision, finding that EPA’s denial was arbitrary and capricious based on the record before the Court and directing EPA to grant the petition, issue a final rule revoking the tolerances or modifying the tolerances if EPA could determine the tolerances were safe, and to modify or cancel food-use registrations for chlorpyrifos under FIFRA.
2021 – Final Tolerance Rule
In Aug. 2021, EPA released the Final Tolerance Rule for Chlorpyrifos, which revokes all tolerances for chlorpyrifos. With this action, EPA complied with the Ninth Circuit’s order directing EPA to issue a final rule in response to the 2007 petition. The final rule for chlorpyrifos is located in docket EPA-HQ-OPP-2021-0523 at www.regulations.gov.
On Feb. 25, 2022, EPA released its response denying the objections and requests for hearing on those objections to the final rule as well as requests to stay the final rule. EPA also issued letters to the registrants of chlorpyrifos products with registered food uses. EPA plans to proceed with canceling the registered food uses associated with the revoked tolerances. If requests for voluntary cancellation are not submitted, EPA intends to initiate the cancellation process with a Notice of Intent to Cancel. The response to the objections for chlorpyrifos is located in docket EPA-HQ-OPP-2021-0523 at www.regulations.gov.
EPA has issued letters to the registrants of chlorpyrifos for products with registered food uses confirming that tolerances will expire as of Feb. 28, 2022, and requesting registrants to take action to cancel these uses. The non-agricultural, non-food uses will remain registered as chlorpyrifos undergoes registration review, a program that re-evaluates all pesticides on a 15-year cycle. 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. All documents related to the registration review can be located in the registration review docket EPA-HQ-OPP-2008-0850 at www.regulations.gov.
EPA will continue to evaluate the non-agricultural, non-food uses as part of the ongoing registration review for chlorpyrifos. Anticipated milestones in the completion of the chlorpyrifos registration review include:
- Posting a draft of the National Marine Fisheries Service (NMFS) revised biological opinion for public comment upon receipt from NMFS to address ESA concerns;
- Responding to comments document addressing comments on the proposed interim decision, the risk assessments, and benefits assessments;
- Developing of an interim decision, including required mitigation from the final rule and recommendations from the Sept. 2020 FIFRA SAP; and
- Evaluating possible endocrine effects associated with the use of chlorpyrifos in the Endocrine Disruptor Screening Program (EDSP).
On Jan. 18, 2017, as part of the registration review process and to meet its obligation under Section 7 of the ESA, EPA issued nationwide biological evaluations (BEs) on chlorpyrifos, diazinon, and malathion to assess risks to threatened and endangered (listed) species from registered uses of these organophosphate pesticides. EPA also initiated formal consultation with the U.S. Fish and Wildlife Service (FWS) and NMFS (the Services) based on the BE conclusions that these pesticides may affect certain listed species and/or their designated critical habitats.
EPA continues to be in consultation with the Services on chlorpyrifos.