UPDATE: On August 18, 2021, EPA announced that it would be publishing a final rule in the Federal Register revoking all safety tolerances for chlorpyrifos. This regulation will take legal effect 60 days after publication in the Federal Register, and the tolerances are expected to expire 6 months after publication.

In a ruling issued on April 29, 2021, the Ninth Circuit Court of Appeals ordered the Environmental Protection Agency (“EPA”) to revoke all tolerances for chlorpyrifos, or modify the tolerances to conform with federal law. Use of the insecticide chlorpyrifos has become controversial due to evidence of its neurotoxic effects, particularly to teens and children. The proceedings leading up to the court’s decision in League of United Latin am. Citizens v. Regan, No. 19-71979 (9th Cir. 2021) initially began in 2007 when two environmental organizations filed a petition asking EPA to prohibit all foods that contain chlorpyrifos residue. EPA denied the 2007 petition in 2017, and in 2019 denied all objections to that decision. The plaintiffs in this lawsuit challenged EPA’s denial of the 2007 petition, claiming that the denial violated EPA’s duty under the Federal Food, Drug and Cosmetic Act (“FFDCA”). The Ninth Circuit agreed with the plaintiffs, finding that EPA had acted contrary to the requirements of the FFDCA.


The FFDCA was first passed by Congress in 1938, granting the Food and Drug Administration (“FDA”) authority to oversee the safety of food, drugs, medical devices, and cosmetics manufactured and sold within the United States. Although FDA is responsible for administering the bulk of the FFDCA, section 346a of the Act authorizes EPA to set tolerances for pesticide residues on foods. In other words, the FFDCA requires EPA to set limits on the amount of a particular pesticide that can legally be in or on raw agricultural commodities or processed foods.

In setting pesticide tolerances, the FFDCA states that EPA “may establish or leave in effect a tolerance for a pesticide chemical residue in or on a food on if [EPA] determines that the tolerance is safe.” 21 U.S.C. § 346a(b)(2)(A)(i). The Act goes on to state that with respect to pesticide tolerances, the term “safe” means that EPA “has determined that there is a reasonable certainty that no harm will result from aggregate exposure to the pesticide chemical residue.” 21 U.S.C. § 346a(b)(2)(A)(ii). Additionally, the FFDCA requires EPA to “ensure that there is a reasonable certainty that no harm will result to infants and children from aggregate exposure to the pesticide chemical residue” when it is establishing pesticide tolerances. 21 U.S.C. § 346a(b)(2)(C)(ii).

EPA may decide to issue regulations establishing, modifying, or revoking a pesticide residue tolerance based either on the agency’s own initiative, or in response to a petition filed by an independent party. 21 U.S.C. § 346a(c)(1). Any party may file a petition with EPA to establish, modify, or revoke a pesticide residue tolerance. However, if the petition is asking EPA to modify or revoke the tolerance, then it must include data supporting the request. 40 C.F.R. § 180.32(b). Within 30 of receiving the petition, EPA is required to publish in the Federal Register to undergo 60 days of public notice and comment. 40 C.F.R. §§ 180.7(f), 180.29(b). It is then up to EPA to either issue a regulation in response to the petition, or an order denying the petition. 21 U.S.C. § 346a(d)(4)(A). If EPA chooses to deny a petition, the petitioners may file objections to that decision. If the petitioners do so, EPA is required to respond to the objections “as soon as practicable.” 21 U.S.C. § 346a(g)(2)(C).

Lawsuit Background

The proceeding at the heart of this case began with the filing of the 2007 petition which asked EPA to revoke all tolerances for chlorpyrifos. Chlorpyrifos is an organophosphate pesticide that was initially registered for use as a pesticide in the United States in 1965. It is used on various different crops, and is often used to control soil-borne insect pests. However, there have long been concerns that chlorpyrifos may have neurotoxic effects that are especially harmful to infants and children. The 2007 petition was filed partly due to those concerns, and asserted that newly available scientific evidence showed that current chlorpyrifos tolerances were not safe, particularly for infants and children.

During the following years, EPA conducted its own research on the safety of chlorpyrifos, concluding that “maternal chlorpyrifos exposure would likely be associated with adverse neurodevelopmental outcomes in humans.” However, by 2012, EPA had still not responded to the 2007 petition, which prompted the petitioners to file a lawsuit with the Ninth Circuit asking the court to order EPA to respond. The court agreed with the petitioners and ordered EPA to issue a final agency action on the 2007 petition by February, 2014. While EPA failed to issue a final action at that time, it did publish a document in December 2014 expressing greater certainty that chlorpyrifos was causing neurotoxic harm.

In August 2015, the Ninth Circuit again set a deadline for EPA to issue a final response to the 2007 petition. This time, the court ordered EPA to respond by October 31, 2015. While EPA failed to meet this deadline, it did publish a Notice of Proposed Rulemaking to revoke all chlorpyrifos tolerances in the Federal Register in November 2015. Because the proposed rulemaking was not a final agency action, the Ninth Circuit ordered EPA to issue a final response to the 2007 petition by December 30, 2016. That deadline was later extended to March 31, 2017.

Finally, in April 2017, EPA ruled on the 2007 petition. In a final order published in the Federal Register on April 5, 2017, EPA denied the 2007 petition, concluding that “despite several years of study, the science addressing neurodevelopmental effects remains unresolved.” Therefore, the chlorpyrifos tolerances would not be revoked or modified. The petitioners filed objections to 2017 order soon after, and once again filed with the Ninth Circuit asking EPA to respond to those objections after the agency did not respond for over a year. Ultimately, that lawsuit resulted in an order from the court that EPA rule on the objections to the 2017 order within 90 days. In July 2019, EPA issued a final order denying the petitioners’ objections, finally completing the administrative process for the 2007 petition. The decision issued by the Ninth Circuit in League of United Latin am. Citizens v. Regan addresses the petitioners request for review of the 2017 and 2019 orders denying the 2007 petition and the objections to it.

Ninth Circuit Decision

To begin its analysis, the Ninth Circuit first considered whether EPA had lawfully denied the 2007 petition according to the FFDCA. Ultimately, the court concluded that the 2007 petition had been wrongfully denied.

First, the court noted that the FFDCA requires EPA to “establish or leave in effect” a pesticide tolerance “only if [EPA] determines that the tolerance is safe.” 21 U.S.C. § 346a(b)(2)(A)(i). According to the court, the language of the FFDCA shows that “Congress made the explicit decision to prioritize safety over all else.” If EPA becomes aware that there are “genuine questions” as to the safety of a pesticide tolerance, then EPA has a duty under the FFDCA to determine whether the tolerance is still safe. If EPA finds that an existing tolerance is unsafe, then the tolerance may no longer remain in effect.

Here, the 2007 petition contained sufficient evidence to establish that a review of the chlorpyrifos tolerances was necessary, and EPA’s own subsequent research concluded that the existing chlorpyrifos tolerances were harmful. Because EPA discovered that the existing chlorpyrifos tolerances were unsafe, and because the FFDCA states that a pesticide tolerance may remain in effect “only if” EPA determines that it is safe, the court concluded that EPA wrongly denied the 2007 petition asking that the chlorpyrifos tolerances be modified or vacated.

After concluding that EPA had unlawfully denied the 2007 petition, the Ninth Circuit next considered what the appropriate remedy should be. At the outset, the court concluded that it had to at least set aside the 2017 order denying the 2007 petition. The plaintiffs argued that the court should also order EPA to revoke the current chlorpyrifos tolerances by a specific date. Once again, the court turned to the text of the FFDCA which states that EPA “shall modify or review a tolerance if [EPA] determines that it is not safe.” 21 U.S.C. § 346a(b)(2)(A)(i). According to the court, that language “makes it clear that once the EPA has determined that a tolerance is not safe, it has no discretion to temporize pending additional research; it must modify or revoke the tolerance.” Because EPA has determined that the existing chlorpyrifos tolerance is not safe, it must modify or revoke the tolerance. Therefore, the court has ordered EPA to issue a final regulation within 60 days that will either revoke all chlorpyrifos tolerances or modify the tolerances so that they will be safe for humans, including infants and children.


Once the Ninth Circuit issues its mandate, a separate document that the court issues once the decision becomes final, EPA will have 60 days to determine whether it will revoke or modify the chlorpyrifos tolerances. Whatever EPA decides to do, the amount of chlorpyrifos that is allowed to legally be in or on raw agricultural products or processed foods is likely to change. Additionally, EPA has been ordered to review all Federal Insecticide, Fungicide, and Rodenticide Act regulations related to chlorpyrifos in order to ensure that they remain in-line with chlorpyrifos tolerances once EPA completes the court’s order. Whether this could lead to a change in the federally registered chlorpyrifos label is currently unclear. For members of the agricultural industry who use chlorpyrifos, a change to the tolerances could affect future use. Until EPA issues the action ordered by the court, it is unclear how much current chlorpyrifos use may be affected.


To read the Ninth Circuit’s decision in League of United Latin am. Citizens v. Regan, click here.

To read the 2007 petition, click here.

To read the 2017 order, click here.

To read the 2019 order, click here.

To read the text of the FFDCA, click here.

For additional National Agricultural Law Center resources on pesticides, click here.