Bergeson & Campbell, P.C. serves small, medium, and large pesticide product registrants and other stakeholders in the agricultural and biocidal sectors, in virtually every aspect of pesticide law, policy, science, and regulation.

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

The California Department of Pesticide Regulation (DPR) announced on February 26, 2015, a revision to the process for evaluation of the potential for a pesticide to move off-site into surface water when the pesticide is used in an urban area. The former evaluation method followed the U.S. Environmental Protection Agency (EPA) approach with California specific parameters. This revision will continue to use the EPA approach but allow incorporation of a module specific for California urban settings.

Potential adverse impacts on surface water from use of pesticides are assessed in California by DPR’s Environmental Monitoring Branch’s Surface Water Protection Program (SWPP) using EPA methodology. The SWPP uses the EPA evaluation method for proposed agricultural pesticide registrations based on PE5 (PRZM-EXAMS version 5) and Tier 2 modeling scenarios but there have been no consistent methods for assessing potential pesticide runoff on impervious surfaces in an urban setting. The new California urban module includes the following improvements that are designed to be further representative of urban conditions in California:

* Introduction of four types of surfaces by permeability and water sources;
* Consideration of pesticide transport induced by dry-weather runoff from impervious surfaces;
* Separation of impervious and pervious portions in the modeling scenarios;
* Use of prescheduled lawn irrigation;
* Characterization of residential and commercial/industrial areas to reflect California urban conditions; and
* Aggregations of water, sediment, and pesticide yields for the urban watershed.

The urban model is designed particularly for evaluating pesticides applied outdoors in areas with large amounts of impervious surfaces such as residential areas, commercial/industrial facilities, and highway and road rights-of-way applications. Pesticide products of interest would be those that have the potential for impact to surface waters through overspray to impervious surfaces in these areas


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.


By Susan Hunter Youngren, Ph.D.

On October 15, 2014, the Office of Pesticide Programs (OPP) announced a voluntary program to document the effectiveness of agricultural pesticide spray application technologies on reducing pesticide spray drift. Under the Drift Reduction Technology (DRT) Program, agricultural equipment manufacturers would conduct (or make arrangements for a testing facility to conduct) studies to determine the percent drift reduction according to a verification protocol. Once completed, the manufacturer would submit the study to the U.S. Environmental Protection Agency (EPA) for review and evaluation. As verified, these reductions could then be quantitatively credited in the environmental risk assessments used to develop the drift reduction measures appearing on the label of the pesticide product. EPA will then review the manufacturers’ studies and, based on these data, it will assign spraying devices a rating on a four-star scale:

* Four stars: Device can reduce spray drift by 90 percent or more.

* Three stars: Device can reduce spray drift by between 75 percent to 89 percent.

* Two stars: Device can reduce spray drift by between 50 percent to 74 percent.

* One star: Device can reduce spray drift by between 25 percent to 49 percent.

* No stars: Device can reduce spray drift by less than 25 percent.

EPA allows pesticide manufacturers to include labeling on their products that contain dual-use instructions, one for farmers using devices that have received stars through the DRT program and another for those using devices that do not have a DRT rating.


By:  Lisa M. Campbell and Susan Hunter Youngren, Ph. D.

Spray drift and volatilization issues increasingly are significant issues in pesticide product risk assessments. Earlier this year, the U.S. Environmental Protection Agency (EPA) issued drafts of key guidance documents, which focused on issues that were key in the chlorpyrifos petition response, and more recently, at least one registration review decision that reflects current and still evolving EPA policy on spray drift and volatilization issues.

How potential for spray drift and for volatilization are identified and then managed are likely to be key elements of ongoing and future risk assessments underlying forthcoming EPA registration and reregistration, with significant potential impact on these decisions. Registrants should monitor closely the policies, EPA decisions implementing them, and their potential impact on their products, particularly given the public interest in these issues.

The EPA documents issued in the past eight or so months are significant, particularly given the years of controversy and difficulty in past attempts to propose a clear and “simple” definition of “drift.” The perception by some advocacy groups is that EPA is not adequately addressing alleged harms posed by drift, and resulting appeals for court intervention will undoubtedly complicate the matrix of considerations influencing EPA’s policy. These reasons alone make monitoring the development of these policies critical for registrants.