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By James V. Aidala

In early July 1996, I was returning on a flight from Amman, Jordan, wondering what kind of negotiation we in the Clinton Administration faced in completing the legislative text of what became the Food Quality Protection Act (FQPA). (I had been asked to go to Jordan to visit the Jordanian pesticide regulatory program by a friend who was a senior official at the State Department. The result of my visit may have played a very, very small role in the Middle East peace process -- but that is another story for another time).

Some weeks earlier, I had been approached by Congressional staff members whom I knew from my previous job at the Congressional Research Service (CRS) as the subject area expert on the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and pesticide regulation. I joined the Clinton Administration as a political deputy in the U.S. Environmental Protection Agency’s (EPA) Office of Prevention, Pesticides, and Toxic Substances (OPPTS, now renamed as the Office of Chemical Safety and Pollution Prevention (OCSPP)). Dr. Lynn Goldman was the Assistant Administrator who had recruited me to join the efforts to reform, that is, modernize, the Delaney Clause of the Federal Food, Drug, and Cosmetic Act (FFDCA). Over the years since it was enacted in 1958, risk assessment methods and our understanding of possible cancer risks had changed greatly.

Setting the Context

In 1989, the National Academy of Sciences issued a report on “The Delaney Paradox,” examining how the Delaney Clause ironically prevented safer new pesticides from entering the market. After an important court decision (Les v. Riley), EPA was told that even if it was undesirable public policy, the law can only be changed by Congress. As EPA went along with its work, many feared that numerous pesticides might be forced off the market even if, using modern evaluation policies, they presented little risk or were in fact safer than the alternatives.

During this time, advocacy groups were concerned that the then-current law was not protective enough of the possible risks to children’s diets. A simple way to say this is, for purposes of risk assessment: “Children are not little adults,” and supporters emphasized that dietary risk assessments by EPA should pay special attention to possible children’s risk given differences in metabolism, growth stages, and other important physiological characteristics.

This led to another National Academy of Sciences report in 1994 on “Pesticides in the Diets of Infants and Children,” which recommended that pesticide regulation include particular attention and possibly greater regulation of estimated dietary risks from pesticides. Given that the new Assistant Administrator of OPPTS was Dr. Lynn Goldman, a pediatrician, this concern was a priority for the Clinton Administration.

“The Gingrich Revolution”

A less noticed irony, but also important to the history of FQPA, is the change in party control of the House of Representatives, led by Representative Newt Gingrich (R-GA) and the “Contract with America” during the 1994 elections. Unexpectedly, the Republicans had the majority in the House for the first time in 40 years, and they elected Representative Gingrich Speaker of the House.

Much longer stories have been and will be written, but shortly after taking power in the House in January 1995, the Republicans were viewed as letting lobbyists run amok -- even suggesting amendments to environmental laws while lobbyists were sitting on the dais of Committee meetings. By the end of 1995 and going into an election year in 1996, “word was” the leadership, at least on the House Energy and Commerce Committee -- chaired by Representative Thomas Bliley (R-VA) -- was looking for a “green vote” to offset the image of an anti-environment House majority. Led by staff from the office of Chair Bliley and Representative John Dingell (D-MI), who was the senior Democrat on the Committee, a draft of a compromise bill was floated and made its way to my office at EPA.

Meantime, during the previous Congress (103rd Congress, 1993 - 1994), a team of EPA staff, led by Jim Jones (a later even more famous name in EPA pesticide regulation) of the Assistant Administrator’s office, along with staff from the Office of Pesticide Programs (OPP) and the Office of General Counsel (OGC), and staff from the U.S. Department of Agriculture (USDA) and the U.S. Food and Drug Administration (FDA) (it takes a village), had developed a Clinton Administration bill that did not gather much support during 1994. The legislation did have the core concepts of “fixing Delaney” and including the “reasonable certainty of no harm” standard, and it incorporated strong protections about possible risks from residues in the diets of infants and children.

In the new Congress (the 104th), there was some action during 1995 in the House Agriculture Committee on FIFRA issues related to antimicrobial products, minor uses of pesticides, and ways to prod the registration process to become more predictable and timely (this was before the Pesticide Registration Improvement Act (PRIA)). The FIFRA amendments were not viewed as controversial and were successfully discussed between both sides of the aisle (the Agriculture Committees were much more bipartisan in those days). By itself, that package was not likely to make it through the legislative gauntlet, given the shift in political power on the Hill.

Also in 1995, Carol Browner (the EPA Administrator) cautioned us that successful bipartisan legislation was unlikely, so not much effort should be invested, given other priorities.

The key event came in the late spring of 1996, when we first saw a draft of the legislation floated by the staff of Representatives Bliley and Dingell. It was far from perfect, but it included the core elements of what the Administration had proposed in the previous Congress. Since that earlier bill had been drafted with the coordination of EPA, FDA, and USDA, if it had the essential ingredients, we thought it might be a viable vehicle for further discussion. We also sought comment from some of the influential environmental groups that had been disappointed in the Administration’s legislation in the previous Congress. Suffice it to say, inclusion of the core elements of a tough standard (reasonable certainty of no harm) and special protections regarding children’s diets made the proposals a “possible” vehicle for further discussion.

We also started to have discussions with the staff of Representative Waxman (D-CA) in the House and Senator Kennedy (D-MA). Representative Waxman was the ranking Democrat on the Energy and Commerce Subcommittee, and Senator Kennedy was the ranking Democrat on the Labor Committee, which had jurisdiction over the FFDCA.

Back to July 1996

To shorten the story, we had intense, long meetings with the various interested parties -- pesticide registrants; environmental groups; trade associations; agency staff at EPA, FDA, and USDA; Congressional staff from the authorizing Committees; and Administration leaders within the agencies and the White House. In an amazingly short time, we came to agreement over the text, which is now FQPA. Representatives Waxman and Roberts (R-KS -- Chair of the House Agriculture Committee) held a press event about the historic compromise -- even more historic since the two Representatives rarely agreed on significant legislation. Their joint endorsement and statement of support signaled to members of both parties on both sides of Capitol Hill that this was an unusual, and important, compromise. The Congressional staff then recognized the next hurdle: the August recess was approaching fast, and if not enacted into law by then, the delay could be fatal, or at least make matters more complicated, as the multitude of interest groups would likely pick apart and want further changes to the agreement that had been reached. So the rush was on to get the “green vote” to the floor of the House and Senate.

Some last-moment hiccups took a little more time. Senator Lugar (R-IN), the Senate Agriculture Committee Chair, wanted a hearing to at least review the legislation. This was not a huge hurdle, but finding time on the floor was a race against the clock before the August recess. The House was the first to vote on July 23, 1996. The bill was approved with a surprising unanimous roll call vote in the majority Republican House (the vote was 417-0 with 16 not voting). Unanimous bipartisan support! -- imagine that in today’s world.

Then, with a sprinkling of clarifying (that is, reassuring) pieces of correspondence, the Senate agreed to the House legislation under unanimous consent. (In fact, for any trivia nuts out there, if you watch the C-SPAN video of how long the Senate deliberation lasted at the end of the day on July 24, 1996 -- the request for unanimous consent and agreement clocks in under 30 seconds.)

So with unanimous support in both the House and the Senate, FQPA was approved.

One Last Step

One very important last step was needed before FQPA became law -- the President needed to sign the legislation. That happened at the White House when H.R. 1627 was signed by President Clinton on August 3, 1996.



By James V. Aidala, Lisa R. Burchi, and Barbara A. Christianson

On August 18, 2021, the U.S. Environmental Protection Agency (EPA) announced that it will stop the use of the pesticide chlorpyrifos on all food. In the pre-publication of the Federal Register notice released on August 19, 2021, EPA revoked all “tolerances” for chlorpyrifos, which establish an amount of a pesticide that is allowed on food. In addition, EPA states that it will issue a Notice of Intent to Cancel under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) to cancel registered food uses of chlorpyrifos associated with the revoked tolerances. EPA has stated the cancellation order will follow in approximately six months after the tolerance revocations.

EPA’s announcement responds to the Ninth Circuit’s order, issued on April 29, 2021, that vacated EPA orders issued in 2017 and 2019 denying a 2007 petition filed by Pesticide Action Network North America and Natural Resources Defense Council. That petition requested that EPA revoke all chlorpyrifos tolerances, or the maximum allowed residue levels in food, because those tolerances were not safe, in part due to the potential for neurodevelopmental effects in children. The 2017 and 2019 orders denying the 2007 petition were challenged in the Ninth Circuit by a coalition of farmworker, health, environmental, and other groups.

In its order, the Ninth Circuit found that “...EPA had abdicated its statutory duty under the Federal Food, Drug and Cosmetic Act (FFDCA) ...” to “conclude, to the statutorily required standard of reasonable certainty, that the present tolerances caused no harm.” After vacating the 2017 and 2019 orders, the court remanded the matter to EPA with instructions to: “(1) grant the 2007 Petition; (2) issue a final regulation within 60 days following issuance of the mandate that either (a) revokes all chlorpyrifos tolerances or (b) modifies chlorpyrifos tolerances and simultaneously certifies that, with the tolerances so modified, the EPA ‘has determined that there is a reasonable certainty that no harm will result from aggregate exposure to the pesticide chemical residue, including all anticipated dietary exposures and all other exposures for which there is reliable information,’ including for ‘infants and children’; and (3) modify or cancel related FIFRA registrations for food use in a timely fashion consistent with the requirements of 21 U.S.C. § 346a(a)(1).”

In its announcement, EPA states that it has determined that the current aggregate exposures from the use of chlorpyrifos do not meet the legally required safety standard that there is a reasonable certainty that no harm will result from such exposures. Chlorpyrifos is an organophosphate insecticide used for a large variety of agricultural uses and has been continually reviewed with regard to potential adverse effects, including possible neurological effects in children, which has been the subject of considerable controversy for many years. EPA’s announcement notes that a number of other countries, including the European Union and Canada, and some states, including California, Hawaii, New York, Maryland, and Oregon, have taken similar action to restrict the use of this pesticide on food.

EPA states its action also will be incorporated into the ongoing registration review for chlorpyrifos. EPA is continuing to review the comments submitted on the chlorpyrifos proposed interim decision, draft revised human health risk assessment, and draft ecological risk assessment. These documents are available in the chlorpyrifos registration review docket EPA-HQ-OPP-2008-0850 at and a discussion of these issues is available on our blog here.

After considering public comments, EPA will proceed with its registration review of the remaining non-food uses of chlorpyrifos by issuing the interim decision, which may consider additional measures to reduce human health and ecological risks.


Separate from any issues of science, evidence, or interpretation, the FFDCA’s channels of trade provision is designed to address what happens if EPA cancels a pesticide product for not meeting Food Quality Protection Act (FQPA) standards and then revokes the tolerance. EPA’s initial description of its decision was unclear on this important point regarding the status of food already in the channels of trade that may contain chlorpyrifos residues.

EPA statements at an August 18, 2021, phone briefing with agricultural stakeholders appeared to present a position that the tolerance revocations would be in effect immediately upon publication in the Federal Register. This implied that there may be an immediate revocation of the tolerances before any parallel action to cancel the associated pesticide registrations. The pre-publication version of the notice clarified that the revocation of chlorpyrifos tolerances would not become effective until six months after the publication of the notice in the Federal Register.  As of August 24, 2021, the notice has not been published in the Federal Register.

This revocation delay of six months aligns with the statement also made by EPA to cancel the registration of chlorpyrifos food use products six months after the revocation notice. EPA may face questions from some of the groups that have been advocating for this type of EPA action concerning why, if these tolerances need to be revoked, the use of the pesticide will continue in effect for the remainder of this growing season. Ed Messina, Office Director of the Office of Pesticide Programs, made a glancing reference to this at the phone conference when he stated EPA and the U.S. Food and Drug Administration (FDA) are “having discussions.” 

According to EPA, use of chlorpyrifos has been in decline due to restrictions at the state level and reduced production. EPA also notes that some alternatives have been registered in recent years for most crops, other chemistries and insect growth regulators are available for certain target pests, and that EPA is committed to reviewing replacements for and alternatives to chlorpyrifos. Some growers, however, are using registered chlorpyrifos products on food crops and hoped to be able to continue certain uses. 

EPA states in the pre-publication notice that some uses in certain areas appear to be able to meet the FQPA standard as evaluated in its 2016 and 2020 risk assessment documents, even if including the full 10x FQPA “extra” safety factor (these assessments are the reference documents EPA cites in its revocation notice). EPA further states that the Ninth Circuit’s order did not provide EPA with time to consider further changes to the use patterns or label restrictions to align with such changes hinted at in the revocation notice, and so EPA is issuing the revocation decision now. This begs the question of whether EPA might consider some continued uses in the future, although even considering any “new” tolerance would be very controversial.

In addition, none of the current actions affect (for now) the tolerances for stored grains using the sister chemical (chlorpyrifos-methyl) with a similar toxicological profile. There also are non-food use applications of chlorpyrifos, for example, mosquito control application of chlorpyrifos sprayed over a large area, that are not affected by the tolerance revocation.

This mix of messages may not be easy to explain to users and the consuming public. 

Issues regarding the timing of the revocations and continued uses are also likely to present challenges for FDA. For example, there are various blended commodities (e.g., animal feed grain, possibly co-mingling harvests from different times) where FDA may be unable to determine what part of any enforcement sample came from a particular date of use.

The orderly transition for treated commodities was designed to avoid public and grower confusion that characterized the episodes of StarLink corn chaos in 2000 or the Cheerios contamination incident in 1994 involving a reported over 100 million boxes of cereal that were eventually destroyed. EPA cites international trade obligations as another reason for the coordinated actions effective in six months to notify foreign trading partners with a “reasonable interval” for adjusting to a changed regulatory situation.

Additional information on chlorpyrifos is available on our blog.


By Lisa M. Campbell, Lisa R. Burchi, and James V. Aidala

On December 7, 2020, the U.S. Environmental Protection Agency (EPA) issued for comment the Proposed Interim Decision (PID) for chlorpyrifos.  85 Fed. Reg. 78849.  EPA announced it is proposing new risk mitigation measures to address potential human and environmental risks identified in EPA’s September 2020 draft risk assessments.  The PID proposes the following measures:

  • Label amendments limiting application to address potential drinking water risks of concern.
  • Additional personal protection equipment and application restrictions to address potential occupational handler risks of concern.
  • Spray drift mitigation, in combination with the use limitations and application restrictions identified to address drinking water and occupational risks, to reduce exposure to non-target organisms.

EPA states that the PID presents proposed mitigation with the 10-fold (10x) Food Quality Protection Act (FQPA) safety factor, reflecting the uncertainties around doses that may cause pre- and post-natal neurodevelopmental effects.  Under FQPA, EPA evaluates new and existing pesticides to ensure they can be used with a reasonable certainty of no harm to infants, children, and adults.  EPA is required to consider the special susceptibility of children to pesticides by using an additional 10x safety factor unless adequate data are available to support a different factor.  EPA additionally included a FQPA factor of 1x to reflect the range of potential risk estimates of chlorpyrifos, as illustrated in the September 2020 draft risk assessments.

Comments on both the September 2020 draft risk assessments and the PID are due on or before February 5, 2021.  EPA states that by holding the comment period for both actions at the same time, the public has access to more information and can provide more informed, robust comments.  Comments can be submitted at EPA-HQ-OPP-2008-0850.

EPA announced that it will also consider the input and recommendations from the September 2020 Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Scientific Advisory Panel (SAP) meeting once it releases its report in December 2020.  Depending on the SAP’s conclusions, EPA may further revise the human health risk assessment. 


The inclusion of both 1x and 10x calculations for the appropriate FQPA safety factor is unusual.  EPA states the final decision on the appropriate FQPA safety factor is partly dependent on any recommendations expected from the SAP meeting, which reviewed the “use of new approach methodologies (NAMs) to derive extrapolation factors and evaluate developmental neurotoxicity for human health risk assessment.”  This is part of a larger and longer evaluation of whether test methods that avoid using test animals can reliably substitute for current test guideline requirements, that is, whether it is appropriate to rely on in vitro test protocols to substitute for current in vivo testing protocols.

EPA’s articulation at this point in time of mitigation needed if the FQPA 10x safety factor is retained may indicate a prediction about the SAP’s likely recommendations.  It will be important to monitor developments on this issue closely.


By Lisa M. Campbell, Timothy D. Backstrom, and James V. Aidala

On August 2, 2019, the U.S. Environmental Protection Agency (EPA) Office of Pesticide Programs (OPP) announced that it has decided to reduce the Food Quality Protection Act (FQPA) safety factor for infants and children for pyrethroids from its current value of 3X to a new value of 1X.  This decision is based on a July 1, 2019, OPP report entitled “USEPA Office of Pesticide Programs’ Re-evaluation of the FQPA Safety Factor for Pyrethroids: Updated Literature and CAPHRA Program Data Review.”  Risk assessments incorporating the new lower FQPA safety factor for pyrethroids will be utilized in developing proposed registration review decisions for these compounds, and EPA has stated it will be taking public comment on the OPP report reducing the FQPA safety factor for pyrethroids after EPA publishes a notice of availability for the proposed registration review decisions.

Pyrethroids are a group of insecticides that includes natural pyrethrins (found in chrysanthemums) and more than 30 synthetic compounds with similar structure and activity. EPA has determined that it is appropriate to establish one FQPA safety factor for all pyrethroid active ingredients because these compounds all have the same mode of action and similar patterns of toxicity.  Pyrethroid insecticides are widely used in and around residential structures, on pets, in treated clothing, for mosquito control, and in various agricultural applications.  EPA indicates that although pyrethroids have relatively low mammalian toxicity, EPA believes that the principal concern for human risk assessment is a potential to cause acute neurotoxic effects.

The FQPA safety factor is intended to account for “potential pre- and post-natal toxicity and completeness of data with respect to exposure and toxicity to infants and children.”  The FQPA safety factor is set by statute at a default value of 10X, but EPA may select a lower value for this safety factor if EPA determines based on “reliable data” that such a lower value will be safe for infants and children.  This determination necessarily depends on EPA’s assessment of the quality of the data that address the susceptibility to adverse effects of the pesticide of infants and children.  Based on current EPA guidance, OPP evaluates the need for the default FQPA safety factor of 10X in two components: a safety factor of about 3X assigned to pharmacodynamic (PD) differences and a safety factor of about 3X assigned to pharmacokinetic (PK) differences.  PD differences refer to the sequence of events at the molecular or cellular level leading to a toxic response to a substance, while PK differences refer to absorption, distribution, metabolism, and excretion of the substance.

EPA previously evaluated the adequacy of the database concerning risks to infants and children posed by pyrethroid active ingredients in 2011.  At that time, EPA decided that there were sufficient data concerning the mechanism for potential neurotoxic effects of pyrethroids to allow EPA to reduce the factor for PD differences to 1X, but EPA retained the 3X factor for PK differences because EPA believed that the available pharmacokinetic data for pyrethroids was not sufficient for EPA to conclude that infants and children would not confront a greater risk of neurotoxic outcomes.  After EPA made the 2011 determinations, the Council for the Advancement of Pyrethroid Human Risk Assessment (CAPHRA) conducted a variety of additional research to address whether children are more sensitive to the neurotoxic effects of pyrethroid exposure, and this research assessed both PD and PK differences.  CAPHRA submitted a peer-reviewed physiologically based pharmacokinetic (PbPk) model for pyrethroids to EPA in 2018.  After reviewing the new CAPHRA data and the current public literature for pyrethroids, EPA has now concluded that the factor for PD differences should be maintained at 1X, but the factor for PK differences should be reduced from 3X to 1X.  Collectively, these determinations mean that EPA has concluded that there are reliable data to support a determination that infants and children are not more susceptible to the neurotoxic effects of pyrethroids than adults, so there is no need to retain either the default FQPA safety factor of 10X or the previous FQPA safety factor used for pyrethroids of 3X.


The adoption by EPA of a new FQPA safety factor of 1X for all pyrethroid active ingredients will likely facilitate retention of existing use patterns and use directions for a large number of pyrethroid insecticides that are commonly used in and around human residences and workplaces.

From a larger perspective, the process by which EPA evaluated and selected a proposed FQPA safety factor for pyrethroids may be seen as typical for most pesticides or classes of pesticides.  The selection of a FQPA safety factor for a particular pesticide usually is based on review of available animal data, including PD and PK data, to determine whether there is any basis for concluding that infants and children may be more susceptible to adverse effects of that pesticide than adults.  Where EPA decides that the animal data addressing this question are insufficient, affected registrants and other proponents of registration can consult with EPA concerning studies that will address the uncertainties.  Depending on the outcome of such studies, EPA may be able to conclude that there is a scientific basis for a partial or complete reduction of the default FQPA safety factor.

Compared to this typical evaluation process, the recent decision by EPA to retain the default FQPA safety factor for all organophosphate (OP) active ingredients, which was based on EPA’s interpretation of neurodevelopmental effects reported at low exposure levels (below the threshold for acetylcholinesterase inhibition) in epidemiology studies for chlorpyrifos, may be seen as an aberration.  EPA’s decision to rely on epidemiology studies that may be susceptible to methodological biases, and the decision to utilize epidemiology studies for chlorpyrifos to set the FQPA safety factors for all OP pesticides, have both been controversial.

EPA’s recent decision to retain the current tolerances and registrations for chlorpyrifos was based in significant part on EPA’s interpretation of a PbPk model for chlorpyrifos previously submitted by DowAgro (now Corteva), which mitigated to some degree EPA’s retention of the default FQPA safety factor for chlorpyrifos.  Corteva may submit further data addressing PD and PK differences for chlorpyrifos, and EPA has also stated that it intends to review some new animal studies for chlopyrifos, which purport to show neurodevelopmental effects at low exposure levels.  Perhaps these data will allow EPA to establish a point of departure (POD) for chlorpyrifos risk assessment without any need for a further excursion into the unfamiliar risk assessment territory represented by EPA’s use of epidemiology data for chlorpyrifos.


By James V. Aidala and Margaret R. Graham

On September 28, 2018, the U.S. Environmental Protection Agency (EPA) announced it was accepting public nominations of scientific experts to be considered for ad hoc participation on the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Scientific Advisory Panel (SAP) through membership on the Food Quality Protection Act (FQPA) Science Review Board (SRB).  83 Fed. Reg. 49091.  EPA states that “all nominees will be considered for ad hoc participation providing independent scientific advice to the EPA on health and safety issues related to pesticides”  and requests that any individuals nominated have expertise in one or more of the following areas:  biochemistry; chemistry; epidemiology; human health risk assessment; pathology; physiologically based pharmacokinetic (PBPK) modeling; aquatic modeling; pharmacology; ecological risk assessment; environmental exposure and fate; environmental toxicology; occupational, consumer, and general exposure assessment; toxicology; dose response modeling; environmental engineering; statistics; water quality monitoring; hydrologist; Geographic Information Systems (GIS) specialist; computational toxicology; entomology; veterinary entomology; medical entomology, insect ecology, allergenicity, research veterinarian; inhalation toxicology; volatile organics; endocrinology, alternative testing methods, high throughput testing approaches, adverse outcome pathways, cross species extrapolation, and systematic review.  The Designated Federal Officer’s to whom nominations should be provided is listed in the Federal Register notice.  Nominations are due by November 13, 2018


FPQA added this SRB to the previous authorization for the SAP to recognize the expanding universe of scientific questions which often underlie issues surrounding pesticide registration.  The FQPA amendment simply adds that “60 scientists who shall be available to the SAP” without specifying any particular disciplines or skills which might be useful to assist with the deliberations and review by the SAP.  This was intended to continually allow EPA to adapt to changing or evolving scientific questions without constantly tinkering with the membership of the SAP itself.  At the same time, it allows these ad hoc members to be recognized for their contributions and to be compensated in the same manner as SAP members.  


By Lisa M. Campbell, Timothy D. Backstrom, and James V. Aidala

A noteworthy development in the U.S. Environmental Protection Agency’s (EPA) ongoing and controversial consideration of the potential use of epidemiological data in its pesticide risk assessments occurred on May 25, 2017, when EPA placed in the public dockets for certain organophosphate (OP) pesticides an “update” of the September 15, 2015, Literature Review and Food Quality Protection Act (FQPA) determination, along with a response to comments on the original document.  These documents were signed by EPA scientists on December 29, 2016, prior to the new Administration, but were placed in the docket only last month, under the new Administration.  The documents attempt to rebut the various criticisms of EPA’s assessment of the epidemiology studies for chlorpyrifos and the original FQPA safety factor determination for OP pesticides, and they reaffirm the policy embodied in the original Literature Review.  Because these new documents were signed in the last days of the Obama Administration, they may be viewed by some industry stakeholders as an effort by some at EPA to “lock in” the prior policy concerning OP pesticides.

The public release of the “updated” Literature Review and response to comments must be considered in the context of the ongoing chlorpyrifos battles that have received significant public attention.  During the five months between the date that these “update” documents were signed and the date that EPA placed them in the public docket, EPA Administrator Pruitt issued a decision on March 29, 2017, to deny the petition filed by the Pesticide Action Network North America (PANNA) and the National Resources Defense Council (NRDC) requesting that EPA revoke all tolerances and cancel all registrations for chlorpyrifos products.  See EPA Denies Petition to Ban Chlorpyrifos.  In his denial decision, Administrator Pruitt concluded it would be appropriate for EPA to defer determining whether chlorpyrifos is likely to cause neurodevelopmental effects at exposure levels below the levels that cause acetylcholinesterase (AChE) inhibition until the completion of the registration review process for chlorpyrifos.  Administrator Pruitt based his decision on the premise that “the science addressing neurodevelopmental effects remains unresolved” and that “significant uncertainty … exists regarding the potential for chlorpyrifos to cause adverse neurodevelopmental effects.”

Some industry stakeholders may argue that the decision by the EPA scientists who prepared the “updated” Literature Review which concluded that EPA should retain the 10X FQPA uncertainty factor for OP pesticides can be reconciled with Administrator Pruitt’s subsequent denial decision, because the “updated” FQPA safety factor determination does not preclude further scientific discussion concerning the potential for neurodevelopmental effects from OP pesticide exposures.  On the other hand, other industry stakeholders may be concerned about the immediate adverse impact of this “updated” FQPA determination on the risk assessments prepared by EPA for OP pesticides and the measures that will be demanded by EPA to mitigate purported risks.

On April 5, 2017, PANNA and NRDC responded to Administrator Pruitt’s March 29, 2017, decision to deny their petition to revoke the tolerances and cancel the registrations for chlorpyrifos by submitting to the Ninth Circuit Court of Appeals a Motion for Further Mandamus Relief.  That motion was substantially based on the premise that EPA does not “suggest that it has reconsidered its finding that chlorpyrifos is unsafe.”  The briefing on the new mandamus motion was completed on May 5, 2017, several weeks before EPA disclosed the documents concerning the “updated” FQPA determination.  Nevertheless, petitioners could try to argue that these documents constitute further evidence supporting their key premise that EPA has not actually revisited its prior determination that chlorpyrifos exposures are unsafe.

The legal and policy issues posed by EPA’s evaluation of the epidemiological data for chlorpyrifos and by EPA’s determination that these data create sufficient uncertainty to warrant retention of the FQPA 10X safety factor for all OP pesticides will be a continued source of controversy, and will be watched with interest by all stakeholders.

More information and updates on chlorpyrifos, the epidemiological data, and their surrounding legal issues is available on our blog item under keyword chlorpyrifos.


By Lisa M. Campbell, James V. Aidala, and Susan Hunter Youngren, Ph.D.

The U.S. Environmental Protection Agency’s (EPA) January 5, 2015, release for public comment of the revised human health risk assessment of chlorpyrifos (!documentDetail;D=EPA-HQ-OPP-2008-0850-0195) reflects another step taken to implement its new spray drift and volatilization policies. These policies were long in the making and the subject of significant discussion and controversy over the years. EPA, with this assessment, has also taken a very public step to implement its controversial policy, announced in December 2009, to apply, effectively, Food Quality Protection Act (FQPA) risk assessment techniques to pesticide uses not subject to FQPA, as part of its commitment to environmental justice.

The spray drift and volatilization policies were discussed in an October 2014 webinar and discussed in our September 17, 2014, memorandum. EPA’s Revised Risk Assessment Methods for Workers, Children of Workers in Agricultural Fields, and Pesticides with No Food Uses, issued in 2009, is discussed in our December 8, 2009, memorandum.

Spray Drift and Volatilization

EPA had been assessing spray drift and volatilization for chlorpyrifos for a number of years, and many of the EPA-derived spray drift and volatilization tools are based on chlorpyrifos data. The January 5 assessment updates the assessment conducted in 2011. This document assesses both potential risks to workers (mixing/loading/applying and re-entry) as well as potential risks to residents (bystanders and food/water consumption). The bystander assessment uses the new tools that EPA released in Spring 2014 to assess potential risks from volatilization and spray drift (as discussed in the B&C webinar). The buffer zones EPA had previously estimated to mitigate spray drift are reduced in the new assessment. The risks noted in the assessment were for workers and specific water areas.

FQPA Risk Assessment Methods Use for Non-FQPA Assessment

In addition to implementing its spray drift and volatilization policies, EPA also assessed exposure in a manner that appears intended to implement the 2009 policy that was the subject of much concern when released for public comment. In that policy, EPA stated its intent to apply risk assessment techniques developed in implementing FQPA’s “extra safety factor” to any pesticide product’s risk assessment, regardless of whether it falls under FQPA, “so long as application of the risk assessment technique is consistent with good scientific practice and is not otherwise prohibited by law.” EPA stated then that this would include “using an additional safety/uncertainty factor to protect children,” as well a number of other factors. EPA announced this policy originally as part of its commitment to considerations of environmental justice.

The chlorpyrifos assessment is based on a physiologically-based, pharmacokinetic-pharmacodynamic (PBPK-PD) model to estimate the toxicologic Points of Departure (POD), thus deriving different toxicological values of concern based on the age, sex, and duration of exposure. The PBPK-PD model is also used to estimate intra-species uncertainty factors (UF), as there is no need for inter-species factors because the model estimates human red blood cell (RBC) acetylcholinesterase/cholinesterase (AChE/ChE) inhibition. Based on the PBPK-PD model, a 10X intra-species factor was used for females of childbearing years whereas it was 4X for all other groups assessed.

The worker of concern in the assessment is defined to be a female of childbearing years due to concern of not only RBC AChE/ChE inhibition, but also the potential for neurodevelopmental effects as seen in epidemiological studies. The epidemiological studies are controversial because there have been many questions about actual exposure to chlorpyrifos, particularly as two studies measured a biomarker that can be seen from exposure to other organophosphates (OP). The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Science Advisory Panel (SAP) reviewed EPA’s assessments of these studies in 2008 and 2012. The SAP concluded that “chlorpyrifos likely played a role” in the observed neurodevelopmental outcomes. EPA determined that based on the weight of evidence (WOE) from animal studies and epidemiological studies, reduction of the 10x “FQPA Safety Factor (SF)” was not appropriate. The residential dietary assessments were compared to a Margin of Exposure (MOE) of 100 (10X FQPA SF x 10X intra-species factor) for women and an MOE of 40 (10X FQPA SF x 4X intra-species factor) for all other ages. The occupational assessments were compared to an MOE of 100 for women and 40 for all other age groups (with no explanation of the reasoning behind those values).

This is noteworthy and should be examined closely because EPA has effectively used an additional “FQPA factor” as a safety factor for occupational assessments. EPA stated in its press release announcing the assessment that potential restrictions may be necessary to protect workers and water.

Next Steps

There is a 60-day comment period for this document, which are due on or before March 16, 2015. Among the issues commenters are likely to address include:

     Use of the PBPK-PD model to estimate PODs;

     Use of the PBPK-PD model to estimate intra-species uncertainty factors;

     Use of the epidemiological data; and

     Use of a 10X SF for occupational exposure.

The full impact of this assessment is not yet clear, but it raises many issues of interest to registrants.