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A newly published peer-reviewed paper reports on HHRA-funded research about rising exposure to 2,4-D herbicide.

Archived HHRA News Posts
  • Spraying Pesticides HHRA Answers DPR’s Call for Comments on Its “Roadmap” for Transforming Pest Management

    In a January 26, 2023 press release, the California Department of Pesticide Regulation (DPR) released a provocative report entitled “Sustainable Pest Management: A Roadmap for California.” The Roadmap report sets “ambitious goals and actions to accelerate California’s systemwide transition to sustainable pest management and eliminate prioritized high-risk pesticides by 2050.” Also by 2050, the Roadmap report envisions that “Sustainable pest management has been adopted as the de facto pest management system in California.” The report captures the ideas and input of a diverse stakeholder group that met over two years to help DPR, Cal-EPA, and the California Department of Food and Agriculture develop a comprehensive plan sufficient to transform agriculture in the State from often heavily-pesticide dependent management systems to systems grounded in pest-prevention, biological control, and reduced-risk biopesticides. The Roadmap identifies and addresses most of the factors shaping pest management systems in the State and calls for dozens of new research, education, training, and regulatory initiatives. In order to guide the implementation process, DPR requested comments from the public that were due March 13, 2023. In crafting HHRA’s comments, Chuck Benbrook and Mark Lipson drew on their decades of experience tracking and advising DPR on pesticide use and regulatory issues.

  • HHRA Paper Analyzes Pesticide Dietary Risk in Individual Samples of Foods

    One of the main sources of pesticide exposure is through  the diet. It is critically important to understand pesticide residues in foods and how dietary risks have changed over time. Over the last 20 years HHRA’s Executive Director Charles Benbrook has developed an analytical database that quantifies the relative risk posed by residues in the diet. Known as the Dietary Risk Index (DRI), this  system was created to help researchers compare risk levels across foods and pesticides, track changes in dietary risk over time, and assess the impact of where food is grown on residues and risk levels, as well as how production systems influence residues and risks (conventional versus organic). The DRI combines the results of United States and United Kingdom pesticide residue testing programs with data on food serving sizes and each pesticide’s chronic Reference Dose or Acceptable Daily Intake. Chronic DRI values are a ratio: the amount of residue in a serving of food relative to the maximum amount allowed by regulators. DRI values are a ratio: the amount of residue in a serving of food relative to the maximum amount allowed by regulators. Data generated by the DRI helps guide HHRA’s policy and public health by highlighting which food-pesticide combinations account for the most worrisome risks in the food supply. The DRI system initially reported aggregate values for a given food/pesticide combination. These values are derived from multiple individual samples of a food collected by regulatory agencies.  For these DRI values, each individual number represents many servings of a given food. In 2022, HHRA added additional functionality the the DRI to report dietary risk in individual samples of a given food. The paper “Tracking pesticide residues and risk levels in individual samples—insights and applications,” which was published in the peer-reviewed journal Environmental Sciences Europe in July 2022, describes the methodology and data sources used to calculate these individual sample DRI values, and highlights some of the results and what they can tell us about residue levels in the global food supply. This is the first analytical system worldwide to provide this level of insight into residues in food. As the paper reports, “dietary risk levels are highly skewed. A large number of samples pose moderate, low, or very-low risks, and relatively few samples pose high or very-high risks.” Thus, regulators and researchers can use the DRI to pinpoint where pesticide dietary risks needs to be mitigated. Like all of HHRA’s peer-reviewed publications, this paper is open access and available free of charge. Click here to view the full text. Access DRI data here.

Extracting New Insights from Old Data on a Pressing Concern — The Rapid Rise in Reliance on 2,4-D Herbicide in the Heartland

Feb 10th, 2022
A newly published peer-reviewed paper reports on HHRA-funded research about rising exposure to 2,4-D herbicide.

 By: Marlaina Freisthler*

Leveraging existing research is central to HHRA’s strategy to accelerate progress in answering contemporary questions about the health impacts of pesticide exposures. One of HHRA’s goals is to draw on existing datasets to glean new insights into pesticide exposure levels, trends, and health impacts. We use pesticide levels in human urine, known as biomarkers, as our primary method of estimating exposure.

As a doctoral student in Environmental Health at George Washington University, I have had the opportunity to work with a team of distinguished researchers to publish a paper in Environmental Health reporting new insights from one such effort to use existing datasets to answer new questions. We report clear associations between trends in the use of the herbicide 2,4-D since 2001 and the frequency of exposures to 2,4-D over time and across the U.S. population. I receive generous doctoral funding sponsored by HHRA to support my research on herbicide exposures and their health impacts, including the costs to publish my research.

In our research leading to this new publication, our team studied the percent of the population with detectable levels of 2,4-D in their urine across 6 cycles of the National Health and Nutrition Examination Survey. NHANES is a large and valuable public dataset providing information about the health and environmental exposures experienced by a representative sample of Americans.  We were able to evaluate data on 14,395 people with available 2,4-D exposure biomarker levels who participated in NHANES between 2001 and 2014.

Our core question was simple and important: Do trends in 2,4-D herbicide use impact trends in 2,4-D exposure levels?

To conduct our analysis, we extracted data on 2,4-D herbicide use from HHRA’s Pesticide Use Data System (PUDS).  All data in PUDS come from annual pesticide use surveys conducted by the U.S. Department of Agriculture.

By combining 2,4-D exposure data from NHANES with 2,4-D use data from PUDS, we found:

  • Around 33% of the people in NHANES had detectable levels of 2,4-D in their urine.
  • The frequency of human exposures to 2,4-D rose from around 17% in 2001-2002 to almost 40% at the peak in 2011-2012.
  • Increasing agricultural use of 2,4-D was clearly associated with increasing odds of detecting of 2,4-D in people’s urine.
  • The odds for increasing exposure detections were more than twice as high for children aged 6-11 compared to adults;
  • The odds for increasing exposure detections were also twice as high for women of childbearing age as for men in the same age group.
The findings that 2,4-D levels were higher in women of childbearing age and young children is particularly concerning as these populations are more vulnerable to pesticide exposure.

We are particularly concerned by the last two findings noted above. Some physical and neurological processes that are still developing in fetuses, infants, and young children are far more susceptible to harmful impacts from chemical exposures. This means that women of childbearing age and young children are vulnerable segments of the U.S. population when exposed to chemicals like 2,4-D. This is especially important because NHANES includes only a small number of pregnant women and has not been used to sample children under age 6 for 2,4-D biomarkers, though infants and toddlers often demonstrate even higher levels of exposure to some chemicals than older children. We want to know why women and children are having these more extreme increases in detections of exposure to 2,4-D, in the hope that answers will lead to actionable steps to reduce exposures to these most vulnerable segments of the population.

Answering our core question is particularly important now, as use of 2,4-D and other herbicides rises sharply across the country, and especially in the Midwest.  This is why our scientists are measuring 2,4-D exposure as part of HHRA’s flagship project, The Heartland Study.

Projections indicate that around two-thirds of the soybean seed sold to farmers in the next few years will be genetically engineered to tolerate both 2,4-D and glyphosate (i.e., Roundup). We expect that reliance on these types of “next-generation” seeds engineered to have multiple herbicide tolerances will continue the sharp increases in use of 2,4-D and other herbicides. In fact, HHRA projects that by 2030, 2,4-D use in the Heartland will exceed glyphosate use, as shown in the dynamic data visualization below.

Our study results indicate that with these increasing uses of 2,4-D, there could very likely be increased population exposures, which our research team is continuing to study. Other ongoing HHRA-funded research projects are exploring the changes in other herbicide exposure levels over time in Midwestern women and the impacts of herbicide exposures on birth outcomes and children’s development.

Below you will find the George Washington University press release announcing publication of our study, a link to access the paper, and the dynamic graphic showing expected increases in 2,4-D use through 2030.

*Marlaina  Freisthler is a PhD student and researcher at the George Washington University. Her graduate fellowship is supported by HHRA.



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