Benbrook et al., 2023
Benbrook C, Mesnage R, Sawyer W. “Genotoxicity Assays Published since 2016 Shed New Light on the Oncogenic Potential of Glyphosate-Based Herbicides.” Agrochemicals. 2023; 2(1):47-68. https://doi.org/10.3390/agrochemicals2010005
Controversy over the oncogenicity of glyphosate-based herbicides (GBHs) persists seven years after a 2015 IARC Monograph classified glyphosate/GBHs as “probably carcinogenic” to humans. Most regulatory authorities have concluded that technical glyphosate poses little or no oncogenic risk via dietary exposure. The US EPA classified glyphosate as “not likely” to pose cancer risk in 1991, a decision reaffirmed in reports issued in 2017 and 2020. A Federal Circuit Court of Appeals in the US vacated EPA’s assessment of glyphosate human-health risks in 2022 and required EPA to revisit old and take into account new data in its forthcoming, possibly final glyphosate/GBH reregistration decision. Divergent assessments of GBH genotoxicity are the primary reason for differing conclusions regarding GBH oncogenic potential. We assessed whether assays published since completion of the EPA and IARC reviews shed new light on glyphosate/GBH genotoxicity. We found 94 such assays, 33 testing technical glyphosate (73% positive) and 61 on GBHs (95% positive). Seven of 7 in vivo human studies report positive results. In light of genotoxicity results published since 2015, the conclusion that GBHs pose no risk of cancer via a genotoxic mechanism is untenable. FULL TEXT
Benbrook, Charles; “Tracking pesticide residues and risk levels in individual samples—insights and applications;” Environmental Sciences Europe, 2022, 34(1); DOI: 10.1186/s12302-022-00636-w.
BACKGROUND: A method is now available to quantify the number of pesticide residues and relative pesticide dietary risks in individual servings of food. The Dietary Risk Index (DRI) system 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.
RESULTS: The DRI system generates individual sample tables reporting the number of residues detected and individual pesticide and aggregate-pesticide DRI values in specific, individual samples of food. It is the first such system to do so worldwide. Output tables produce accurate estimates of real-world dietary risks based on current toxicology data and exposure benchmarks set by regulators. System outputs allow assessment of the distribution of pesticide dietary risks across foods and pesticides and demonstrate that 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.
CONCLUSIONS: The DRI system provides the food industry, regulators and analysts with a simple, accessible online tool to assess pesticide dietary-risk levels by food, by pesticide, as a function of country of origin, and on food grown on conventional versus organic farms. DRI system output tables show that the number of residues in a sample of food is a consistently poor indicator of dietary risk levels. By identifying the relatively small number of high-risk samples, efforts to mitigate pesticide dietary risks can be targeted where the most worrisome risks are.
Freisthler et al., 2022
Freisthler, Marlaina S., Robbins, C. Rebecca, Benbrook, Charles M., Young, Heather A., Haas, David M., Winchester, Paul D., & Perry, Melissa J.; “Association between increasing agricultural use of 2,4-D and population biomarkers of exposure: findings from the National Health and Nutrition Examination Survey, 2001–2014;” Environmental Health, 2022, 21(1); DOI: 10.1186/s12940-021-00815-x.
BACKGROUND: 2,4-Dichlorophenoxyacetic acid (2,4-D) is one of the most extensively used herbicides in the United States. In 2012, 2,4-D was the most widely used herbicide in non-agricultural settings and the fifth most heavily applied pesticide in the US agricultural sector. The objective of this study was to examine trends in 2,4-D urinary biomarker concentrations to determine whether increases in 2,4-D application in agriculture are associated with increases in biomonitoring levels of urine 2,4-D.
METHODS: Data from the National Health and Nutrition Examination Survey (NHANES) with available urine 2,4-D biomarker measurements from survey cycles between 2001 and 2014 were utilized. Urine 2,4-D values were dichotomized using the highest limit of detection (LOD) across all cycles (0.40 mug/L or 0.4 ppb). Agricultural use of 2,4-D was estimated by compiling publicly available federal and private pesticide application data. Logistic regression models adjusted for confounders were fitted to evaluate the association between agricultural use of 2,4-D and urine 2,4-D level above the dichotomization threshold.
RESULTS: Of the 14,395 participants included in the study, 4681 (32.5%) had urine 2,4-D levels above the dichotomization threshold. The frequency of participants with high 2,4-D levels increased significantly (p < .0001), from a low of 17.1% in 2001-2002 to a high of 39.6% in 2011-2012. The adjusted odds of high urinary 2,4-D concentrations associated with 2,4-D agricultural use (per ten million pounds applied) was 2.268 (95% CI: 1.709, 3.009). Children ages 6-11 years (n = 2288) had 2.1 times higher odds of having high 2,4-D urinary concentrations compared to participants aged 20-59 years. Women of childbearing age (age 20-44 years) (n = 2172) had 1.85 times higher odds than men of the same age.
CONCLUSIONS: Agricultural use of 2,4-D has increased substantially from a low point in 2002 and it is predicted to increase further in the coming decade. Because increasing use is likely to increase population level exposures, the associations seen here between 2,4-D crop application and biomonitoring levels require focused biomonitoring and epidemiological evaluation to determine the extent to which rising use and exposures cause adverse health outcomes among vulnerable populations (particularly children and women of childbearing age) and highly exposed individuals (farmers, other herbicide applicators, and their families).
Benbrook and Benbrook, 2021
Benbrook, Charles, & Benbrook, Rachel (2021). “A minimum data set for tracking changes in pesticide use.” In R. Mesnage & J. Zaller (Eds.), Herbicides: Elsevier and RTI Press.
A frequently asked but deceptively simple question often arises about pesticide use on a given farm or crop: Is pesticide use going up, down, or staying about the same? Where substantial changes in pesticide use are occurring, it is also important to understand the factors driving change. These might include more or fewer hectares planted, a change in the crop mix, a higher or lower percentage of hectares treated, or higher or lower rates of application and/or number of applications. Or, it might arise from a shift to other pesticides applied at a higher or lower rate and/or lessened or greater reliance on nonpesticidal strategies and integrated pest management (IPM). Questions about whether pesticide use is changing and why arise for a variety of reasons. Rising use typically increases farmer costs and cuts into profit margins. It generally raises the risk of adverse environmental and/or public health outcomes. It can accelerate the emergence and spread of organisms resistant to applied pesticides. If the need to spray more continues year after year for long enough, farming systems become unsustainable. Lessened reliance on and use of pesticides, on the other hand, are typically brought about and can only be sustained by incrementally more effective prevention-based biointensive IPM systems (bioIPM).1–3 Fewer pesticide applications and fewer pounds/kilograms of active ingredient applied reduce the impacts on nontarget organisms and provide space for beneficial organisms and biodiversity to flourish. Such systems reduce the odds of significant crop loss in years when conditions undermine the efficacy of control measures, leading to spikes in pest populations and the risk of economically meaningful loss of crop yield and/or quality. FULL TEXT
Benbrook et al., 2021a
Benbrook, Charles, Perry, Melissa J., Belpoggi, Fiorella, Landrigan, Philip J., Perro, Michelle, Mandrioli, Daniele, Antoniou, Michael N., Winchester, Paul, & Mesnage, Robin; “Commentary: Novel strategies and new tools to curtail the health effects of pesticides;” Environmental Health, 2021, 20(1); DOI: 10.1186/s12940-021-00773-4.
BACKGROUND: Flaws in the science supporting pesticide risk assessment and regulation stand in the way of progress in mitigating the human health impacts of pesticides. Critical problems include the scope of regulatory testing protocols, the near-total focus on pure active ingredients rather than formulated products, lack of publicly accessible information on co-formulants, excessive reliance on industry-supported studies coupled with reticence to incorporate published results in the risk assessment process, and failure to take advantage of new scientific opportunities and advances, e.g. biomonitoring and “omics” technologies.
RECOMMENDED ACTIONS: Problems in pesticide risk assessment are identified and linked to study design, data, and methodological shortcomings. Steps and strategies are presented that have potential to deepen scientific knowledge of pesticide toxicity, exposures, and risks.
We propose four solutions:
(1) End near-sole reliance in regulatory decision-making on industry-supported studies by supporting and relying more heavily on independent science, especially for core toxicology studies. The cost of conducting core toxicology studies at labs not affiliated with or funded directly by pesticide registrants should be covered via fees paid by manufacturers to public agencies.
(2) Regulators should place more weight on mechanistic data and low-dose studies within the range of contemporary exposures.
(3) Regulators, public health agencies, and funders should increase the share of exposure-assessment resources that produce direct measures of concentrations in bodily fluids and tissues. Human biomonitoring is vital in order to quickly identify rising exposures among vulnerable populations including applicators, pregnant women, and children.
(4) Scientific tools across disciplines can accelerate progress in risk assessments if integrated more effectively. New genetic and metabolomic markers of adverse health impacts and heritable epigenetic impacts are emerging and should be included more routinely in risk assessment to effectively prevent disease.
CONCLUSIONS: Preventing adverse public health outcomes triggered or made worse by exposure to pesticides will require changes in policy and risk assessment procedures, more science free of industry influence, and innovative strategies that blend traditional methods with new tools and mechanistic insights.
Benbrook et al., 2021
Benbrook, Charles, Kegley, Susan, & Baker, Brian; “Organic Farming Lessens Reliance on Pesticides and Promotes Public Health by Lowering Dietary Risks;” Agronomy, 2021, 11(7); DOI: 10.3390/agronomy11071266.
Organic agriculture is a production system that relies on prevention, ecological processes, biodiversity, mechanical processes, and natural cycles to control pests and maintain productivity. Pesticide use is generally limited or absent in organic agroecosystems, in contrast with non-organic (conventional) production systems that primarily rely on pesticides for crop protection. Significant differences in pesticide use between the two production systems markedly alter the relative dietary exposure and risk levels and the environmental impacts of pesticides. Data are presented on pesticide use on organic and non-organic farms for all crops and selected horticultural crops. The relative dietary risks that are posed by organic and non-organic food, with a focus on fresh produce, are also presented and compared. The results support the notion that organic farms apply pesticides far less intensively than conventional farms, in part because, over time on well-managed organic farms, pest pressure falls when compared to the levels on nearby conventional farms growing the same crops. Biopesticides are the predominant pesticides used in organic production, which work by a non-toxic mode of action, and pose minimal risks to human health and the environment. Consequently, eating organic food, especially fruits and vegetables, can largely eliminate the risks posed by pesticide dietary exposure. We recommend ways to lower the pesticide risks by increased adoption of organic farming practices and highlight options along organic food supply chains to further reduce pesticide use, exposures, and adverse worker and environmental impacts. FULL TEXT
Benbrook and Davis, 2020
Benbrook, Charles M., & Davis, Donald R.; “The dietary risk index system: a tool to track pesticide dietary risks;” Environmental Health, 2020, 19(1); DOI: 10.1186/s12940-020-00657-z.
BACKGROUND: For years the United States Department of Agriculture’s Pesticide Data Program and the United Kingdom’s Food Standards Agency have published annual or quarterly data on pesticide residues in foods. Both programs report residues in conventionally grown, organic, and imported foods. The US program has tested about 288,000 food samples since 1992, primarily fruits and vegetables consumed by children. Since 1999 the UK has tested about 72,000 samples of a wider range of foods. These data are vital inputs in tracking trends in pesticide dietary risks.
METHODS: The Dietary Risk Index (DRI) system facilitates detailed analyses of US and UK pesticide residue data, trends, and chronic risk distributions. The DRI value for a pesticide is the dietary intake of that pesticide from a single serving of food divided by the pesticide’s acceptable daily intake as set by the US Environmental Protection Agency. It can be calculated based on average annual residue concentrations, and on residue levels in individual samples of food. DRI values can be aggregated over multiple pesticides in single foods, and over individual pesticides in multiple foods.
RESULTS: The DRI system provides insights into the levels, trends, and distribution of pesticide dietary risk across most widely consumed foods. By drawing on both US Pesticide Data Program and UK-Food Standards Agency residue data, the DRI is capable of assessing pesticide risks in a significant portion of the global food supply. Substantial reductions in pesticide dietary risks occurred in the early 2000s, primarily from replacement of organophosphate insecticides with seemingly lower-risk neonicotinoids. However, there remain several areas of concern and opportunities to reduce risks. Both herbicide and fungicide dietary risks are rising. Organically grown produce poses risks far lower than corresponding, conventionally grown produce. Risk differences are inconsistent between domestic and imported foods.
CONCLUSTIONS: The surest ways to markedly reduce pesticide dietary risks are to shift relatively high-risk fruits and vegetables to organic production. For other foods, reducing reliance on pesticides overall, and especially high-risk pesticides, will incrementally lower risks. The DRI system can help focus such efforts and track progress in reducing pesticide dietary risk. FULL TEXT
Benbrook, Charles; “Shining a Light on Glyphosate-Based Herbicide Hazard, Exposures and Risk: Role of Non-Hodgkin Lymphoma Litigation in the USA;” European Journal of Risk Regulation, 2020, 11(3), 498-519; DOI: 10.1017/err.2020.16.
Roundup, and other glyphosate-based herbicides, are the most heavily used pesticides in the history of the USA and globally. In March 2015, the International Agency for Research on Cancer (IARC) classified glyphosate as a “probable human carcinogen”. A portion of the 695,000 Americans then living in 2015 with non-Hodgkin lymphoma (NHL) became aware of IARC’s decision. Several thousand Roundup–NHL lawsuits had been filed by the end of 2017, rising to 18,400 by July 2019 and 42,000 by November 2019. Three cases have gone to trial, each won by the plaintiffs. The author has served as an expert witness for the plaintiffs in this litigation and has been compensated for his time spent. The impact of the litigation on the independent assessment of the science useful in determining whether glyphosate and glyphosate-based herbicide exposures are linked to NHL is reviewed, as is why the US Environmental Protection Agency (EPA) and IARC reached such different judgements regarding glyphosate human cancer hazard and risk. Two important “lessons learned” regarding the EPA versus IARC assessment of glyphosate cancer hazard and risk are highlighted. The first arises from differences in the magnitude of applicator risks from mostly dermal exposures to formulated glyphosate-based herbicides compared to just dietary exposures to technical glyphosate. The second relates to missed opportunities to markedly lower applicator exposures and risks with little or no impact on sales via reformulation, added warnings and worker safety provisions, company-driven stewardship programmes and greater determination by the EPA in the 1980s to compel Monsanto to add common-sense worker protection provisions onto Roundup labels (eg “wear gloves when applying this product”). Policy reforms designed to alleviate systemic problems with how pesticide hazards, exposures and risks are analysed, regulated and mitigated are described. FULL TEXT
Mesnage et al., 2019
Mesnage, R., Benbrook, C., & Antoniou, M. N.; “Insight into the confusion over surfactant co-formulants in glyphosate-based herbicides;” Food and Chemical Toxicology, 2019, 128, 137-145; DOI: 10.1016/j.fct.2019.03.053.
Glyphosate is the active ingredient in glyphosate-based herbicides (GBHs). Other chemicals in GBHs are presumed as inert by regulatory authorities and are largely ignored in pesticide safety evaluations. We identified the surfactants in a cross-section of GBH formulations and compared their acute toxic effects. The first generation of polyethoxylated amine (POEA) surfactants (POE-tallowamine) in Roundup are markedly more toxic than glyphosate and heightened concerns of risks to human health, especially among heavily-exposed applicators. Beginning in the mid-1990s, first-generation POEAs were progressively replaced by other POEA surfactants, ethoxylated etheramines, which exhibited lower non-target toxic effects. Lingering concern over surfactant toxicity was mitigated at least in part within the European Union by the introduction of propoxylated quaternary ammonium surfactants. This class of POEA surfactants are approximately 100 times less toxic to aquatic ecosystems and human cells than previous GBH-POEA surfactants. As GBH composition is legally classified as confidential commercial information, confusion concerning the identity and concentrations of co-formulants is common and descriptions of test substances in published studies are often erroneous or incomplete. In order to resolve this confusion, laws requiring disclosure of the chemical composition of pesticide products could be enacted. Research to understand health implications from ingesting these substances is required. FULL TEXT
Henner and Backhaus, 2019
Hollert, Henner, & Backhaus, Thomas, “Some food for thought: a short comment on Charles Benbrook´s paper ‘How did the US EPA and IARC reach diametrically opposed conclusions on the genotoxicity of glyphosate-based herbicides?’ and its implications,” Environmental Sciences Europe, 2019, 31(1). DOI: 10.1186/s12302-019-0187-z.
Not available. FULL TEXT