Writing in the New England Journal of Medicine, Philip Landrigan and Charles Benbrook call for a reconsideration of the safety of plant biotechnology due to concern over the impact of herbicides on public health. The authors base their argument upon the International Agency for Research on Cancer (IARC) classification of glyphosate as a ‘probable’ carcinogen and of 2,4-D as a ‘possible’ carcinogen, along with the Environmental Protection Agency (EPA) decision to approve Enlist Duo, a herbicide comprising glyphosate and 2,4-D designed to be used with herbicide resistant, genetically engineered crops.
Dr. Dave Stone, Associate Professor, Department of Environmental and Molecular Toxicology, Oregon State University (webpage):
Expertise: Human health concerns related to chemical exposure and approaches to risk assessment. In particular pesticides, metals, biotoxins and polyaromatic hydrocarbons (PAHs) in drinking, source and wastewaters.
“While it is important to pursue advances in how we assess and manage risk, it is equally important to avoid representations that use inflammatory language, are devoid of context and cause undue alarm. Unfortunately, the latter is the case with the recent commentary by Landrigan and Benbrook who cite Agent Orange, Monarch butterflies, and endocrine disruption to support labeling of genetically modified foods and distort the risk posed by plant biotechnology.
“One of Landrigan and Benbrook’s central arguments is that the GMO landscape has changed as a result of the noted increase in herbicide applications to genetically modified (GM) crops. While this increase raises some key issues, such as weed resistance, the commentary suggests implications to consumers and public health that are unwarranted. Whether or not a pesticide is used in conventional or GM crops, the level of acceptable residue on a commodity, known as a tolerance, is set to protect us from harm. Year after year, residues in our food supply have been measured at trace levels that are far below what is required to result in clinically relevant effects.
“The herbicides used on GM crops undergo a battery of health and environmental studies, including tests for endocrine disruption, ecotoxicity, developmental toxicity and much more. In fact, 2,4-D and glyphosate have been subjected to decades of studies and post-market surveillance, far exceeding personal care products, “all-natural” ingredients and most other substances that we consume on a daily basis at much higher quantities.*”
Dr. Jeff Wolt, Professor of Agronomy & Toxicology, Biosafety Institute for Genetically Modified Agricultural Products, Iowa State University (webpage):
Expertise: Biotechnology safety analysis applied to risk management and science policy decision-making. Environmental and ecotoxicological risk assessment.
“In their piece, Landrigan and Benbrook present a laundry list of familiar misperceptions of modern crop production. Through the lens of their perspective, the public gains a distorted view of the safety of biotechnology crops and pesticides; and of the immense contributions of agriculture to public health in the United States by assuring a safe and abundant food supply. There is always the need for vigilance regarding the safety of the foods we eat, but there is insufficient substance to these authors’ complaints to support their arguments for GM food labeling and against recent regulatory approvals allowing for expanded herbicide uses.
“The authors’ statements regarding findings of the NAS 2000 and 2004 reports are misleading both in terms of what these reports state and the progress that is being made. The 2000 NAS report does recommend development of better assessment techniques for potential allergens. The 2004 NAS report significantly elaborates to describe the overall limitations of allergenicity assessment for foods in general, pointing out that the need to improve allergen assessment methods exists regardless of the source of newly introduced food. The 2004 report recommends to “Standardize methods for monitoring reports of allergenicity to new foods introduced into the marketplace and apply them to new GM foods.” (NAS 2004, p 12). Progress has occurred in this area, specifically with respect to GM foods, where a widely recognized weight of evidence framework for allergenicity risk assessment is in place (Goodman et al., 2008).
“More troubling is their mischaracterization of the 2000 and 2004 NAS reports with respect to postmarketing surveillance. The 2000 NAS report addresses postmarketing surveillance from the perspective of long-term ecological impacts, not food safety considerations, and the interveining 15 years since this report have provided strong evidence of the adequacy of regulatory processes for assessing safety of GM crops to the environment. As for the 2004 NAS report, the findings very clearly state “… there are many instances in which postmarket surveillance may not be warranted. For example, when compositional comparisons of a new GM crop or food (e.g., Roundup Ready soybeans) with its conventional counterpart indicate they are compositionally very similar; exposure to novel components remains very low.” (NAS 2004, p 12) This directly contradicts the point the authors make.
“IARC has classified a wide range of chemicals or activities as probably or possibly causing cancer. The hazard-based analysis employed by IARC limits the studies that are reviewed and disregards exposure. Therefore, the IARC findings of glyphosate as a probable carcinogen and 2,4-D as a possible carcinogen signal the need for vigilance concerning their use, but say nothing regarding risk to human health. EPA and other regulatory authorities conduct a more holistic appraisal of pesticides which considers a wider array of toxicity information as well as exposure characterization to arrive at an understanding of risk of the chemicals under actual use conditions. It is these regulatory risk assessments that support the safe use of glyphosate and 2,4-D in agriculture. EPA shows appropriate vigilance in assuring safety of our food supply through periodic reappraisal of pesticides and is currently undertaking just such an assessment for glyphosate.
“The highly regarded 2009 NAS report “Science and Decisions” recommends that toxicology testing and regulatory assessment be expanded to address additional noncancer endpoints for all chemicals. Landrigan and Benbrook make a similar call specifically for glyphosate and 2,4-D. Expanding the nature of toxicity testing to encompass additional endpoints, when supported by sound scientific rationale, is an admirable goal that will require scientific advances in areas of low-dose appraisal, mixture toxicity, and others. In the interim there is no science rationale to support the alarmist view of Landrigan and Benbrook that the lack of low-dose, mixture, epigenetic or other studies should preclude expanded use of glyphosate and 2,4-D.
“Finally, it is important to recognize the increased likelihood for exposure arising from the expanded use of these chemicals, since this is relevant to the overall appraisal of human and environmental risk. This constitutes a large part of EPA’s rationale in considering the new and expanded uses of these herbicides.”
Dr. Andrew Kniss, Associate Professor, Department of Plant Sciences, University of Wyoming (webpage):
Expertise: Sustainable weed management programs in agronomic crops. Recent research projects include the effect of long-term glyphosate use in glyphosate-resistant cropping systems.
“Dr. Landrigan & Dr. Benbrook state that 0.4 million kg of glyphosate was used in the US in 1974 (the first year it was commercially available), and use has increased 250-fold since then. This may sound concerning, but if you compare use of any popular product to the year it was first commercially available, the number will seem large. For example, iPhone sales have increased by a factor of 122 in just 7 years. In 1995, before the introduction of any glyphosate-resistant GMO crops, glyphosate use exceeded 12 million kg in the US (a 30-fold increase compared to 1974). Glyphosate use certainly increased dramatically in conjunction with adoption of Roundup Ready (glyphosate-resistant) crops. But even the increase between 1995 to 2014 is not purely due to GMO crops, as other uses of glyphosate have expanded during that time due to cost decreases that followed patent expiration. Based on USGS data from 2012, approximately 18% of glyphosate was applied to areas that were not planted to GMO crops. This may seem nit-picky, but I do think it is worth noting since the “250-fold increase” can sound a little inflammatory out of context.
“But for all the nit-picking, it is worth noting that the 80% of 250 million pounds of glyphosate applied to GMO crops in the US is certainly a major selection pressure for glyphosate-resistant weeds. Dr. Landrigan and Dr. Benbrook cite glyphosate-resistant weeds as a primary reason why “fields must now be treated with multiple herbicides,” but this point also deserves some context. In corn, for example, multiple herbicides have been a common practice since long before GMO crops were introduced. In the year 2000, before Roundup Ready GMO corn had gained widespread adoption in the US (and also before glyphosate-resistant weeds were growing in corn fields), corn growers were applying nearly three herbicide active ingredients per acre. The latest USDA data from 2014 show a similar number, less than 3.5 active ingredients applied per acre. This suggests that glyphosate-resistant weeds may certainly have increased the number of herbicides used per acre compared to 5 years ago, but the change has been relatively modest when compared to herbicide use before the adoption of GMO crops.
“Dr. Landrigan and Dr. Benbrook also make several misleading statements, including that the Enlist Duo registration decision by EPA “failed to consider ecologic impact, such as effects on the monarch butterfly and other pollinators.” The EPA provides all relevant regulatory decision information on its website, including the environmental risk assessment documents. Just one of the risk assessment documents for Enlist Duo contains over 100 pages of ‘ecologic impact’ data and interpretation, including environmental fate, degradation, aquatic and terrestrial organism toxicity and exposure estimates. The EPA also explicitly addresses how Enlist Duo will affect pollinators on an FAQ page dedicated to the Enlist Duo registration.
“Another misleading statement made by Dr. Landrigan and Dr. Benbrook is that the “risk assessment gave little consideration to potential health effects in infants and children, thus contravening federal pesticide law.” This claim was also addressed explicitly by EPA in the FAQ document. EPA concluded that after incorporating a 10X safety factor for children, and based on a “complete and very robust” data set, that the “risks were still acceptable for all age groups for all components of the assessment: dietary food and drinking water exposure, volatility, spray drift, residential, and aggregate assessment.”
Declared interests (see GENeS register of interests policy):
Dr Jeffrey Wolt: “I was formerly employed by Dow AgroSciences from 1988-2003. Currently I have no financial relationship, voluntary appointments or advisory capacity with the agricultural industry.”
Dr. Andrew Kniss: “Dow AgroSciences (maker of Enlist Duo), Monsanto (maker of glyphosate and Roundup Ready crops), and several other pesticide and seed companies have provided financial support for my applied research program at the University of Wyoming.”
No further interests declared
‘GMOs, Herbicides, and Public Health‘ by P. Landrigan & C Benbrook, published in the New England Journal of Medicine, on Wednesday August 19, 2015.
*An additional paragraph commenting on the IARC classification of glyphosate was removed at the request of the author following publication of the full IARC monograph.