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One of the tragedies of new pesticide technologies is that the corporate imperative to maximize sales leads to a faster turning of the pesticide treadmill. The dependency on more and often more toxic pesticides — rather than any improvement in pest management — is not an irrational farmer decision. U.S. government subsidy, credit and crop insurance policies based on farmer histories of high crop yields puts farmers between the hard choice of greater chemical dependency to boost yields or to get off the treadmill with little, if any, government assistance.

A second tragedy is that government support for pesticide innovation is far greater than government support to protect farmworker health from new pesticide technology risks. IATP’s investigation of the latest phase of pesticide innovation found no corresponding technology innovation for protecting farmworkers from harm due to inhaling the new generation of pesticides.

IATP began to report on the application of nanotechnology and nanomaterials (atomic to molecular size materials) to pesticides in 2019 in a virtual presentation to a seminar co-organized by the Brazilian Ministry of Labor and the Brazilian Research Network on Nanotechnology Society and Environment (Renanosoma). The theme of the seminar was protecting workers manufacturing or using nanomaterials. Our presentation focused on risks to farmworker health from inhaling nano-scale pesticide particles, the existing state of U.S. pesticide regulation and employer obligations to provide farmworkers with adequate Personal Protection Equipment (PPE) to prevent those risks from becoming harms.

We continued in 2020-2021 to investigate nano-pesticide product development and what should be done to protect farmworkers if the U.S. Environmental Protection Agency (EPA) authorizes nano-pesticides for commercial use. On May 5, IATP published “Nanotechnology-enabled genetically engineered RNA interference pesticides: Socio-economic context, modes of action and risks,” a video lecture, slide deck and article. Despite the title, this is work by a non-scientist for a non-scientific public.

Why have pesticide product developers begun to use nano-scale materials in pesticides? There are, of course, the usual profit motives tied to the patents that confer commercial monopolies on patent holders. But two words summarize the research and investment target in the next big pesticide thing: weed resistance.

The extent of accelerating weed resistance to pesticides applied to major grain and oilseed monocropping was summarized for the non-agricultural public in a 2018 New York Times article, “The Attack of the Superweeds.” Author H. Claire Brown wrote, “Glyphosate’s use remains ubiquitous among growers, however. Even though it doesn’t work on all weeds anymore, the alternative — adopting a more integrated approach to weed control — would mean totally rethinking their operations.” In 2017, the EPA issued “Slowing and Combating Pest Resistance to Pesticides.” One of three reasons for issuing the voluntary guidance was that “no new herbicide mechanism of action has been developed in [the] last 30 years.” If EPA authorizes for commercial use the next big thing in pesticides — nanotechnology enabled pesticides — growers might not have to rethink how they control weeds, much less rethink their operations.

A May 9 EPA article reported that its nanotechnology research team had reviewed 36,000 patents (!) and 500 peer reviewed articles, concluding that there are numerous benefits from nanotechnology enabled pesticides. The research review, published in Nature Nanotechnology (paywalled), states in the abstract, “Nanomaterials with the ability to encapsulate and deliver pesticidal active ingredients (AIs) in a responsive (for example, controlled, targeted and synchronized) manner offer new opportunities to increase pesticidal efficacy and efficiency when compared with conventional pesticides.” The EPA authors conclude with a policy statement: “These benefits, if harnessed appropriately, can promote higher crop yields and thus contribute towards sustainable agriculture and global food security.” What the EPA research team does not state is whether their literature review concerned the nanomaterial coating of existing conventional AIs or the nano-encapsulation of “any new mechanism of action.”

The gene editing or genetic engineering of RNA molecules to interfere with or silence the expression of proteins vital to pest survival in the RNA sequences of targeted weeds or insects is a “new mechanism of action” or Mode of Action (MoA). Friends of the Earth (FOE) illustrated this MoA in their report, “Gene Silencing Pesticides: Risks and Concerns,” to explain the gene editing process and the risks of off-target plant mutations that can occur when pesticides drift beyond their intended target to adjacent plants and insects with similar RNA sequences to that of the targeted pest. In the calculus of EPA risk management, it is likely that any potential GE risks, e.g., of greater potential for plant toxicity or nutritional deficiency, are outweighed by the potential to “promote higher crop yields and thus contribute towards sustainable agriculture and global food security.”

However, we found it disturbing that the authors of an article on the biosafety of RNA interference (RNAi) pesticides minimized the risk to the human immune system of inhaling nanoscale RNAi pesticide particles. The authors suggested that it was “highly questionable” that such chronic inhalation would cause immunity suppression and recommended that “appropriate PPE” would prevent any harm to human health. However, there is no “appropriate PPE” to protect farm workers from inhaling nanoscale pesticide particles, a large fraction of which cannot be expelled from the lower part of the lungs, and which bio-accumulate first in the lung tissue and then elsewhere in the body. While there is no in vivo experimental data on the impact of nano-pesticides on lung tissue, we cited research that used in vitro (petri dish) experiments and computer modeling to predict chronic lung inflammation from inhaling nanomaterial particles. Accordingly, IATP has written to the National Institute for Occupational Health and Safety (NIOSH) to urge them to develop PPE to protect farmworkers spraying nano-pesticides.

One of the co-authors of the biosafety article is the co-inventor of the GreenLight Biosciences Inc. (GLB) nano-RNAi pesticide designed to kill Colorado potato beetles without harming non-target insects. In June 2021, GLB applied to the EPA for a permit to spray its RNAi pesticide on 200 acres of test fields in 11 states from April 2022 to April 2023.  The permit has yet to be granted. But if it is granted, the EPA is satisfied with the testing results and procedures, and determines GLB has complied with other permit requirements, EPA could register the GLB pesticide for commercial use in 2024.

Nanotechnology enabled RNAi pesticides may present a difficult regulatory problem for EPA, which does not risk assess pesticide products, but only their Active Ingredients (AI). However, RNAi is a particularly fragile AI that cannot survive ultra-violet light unless it is nanomaterial coated. Furthermore, nanomaterials, usually a composition of nano-clays and nano-bio polymers, enable the RNAi to penetrate the cellular tissue of plants and animals (and humans), both targeted and untargeted with an efficiency and efficacy that is impossible for macro-scale coatings. In other words, the nano-coatings make the RNAi active and so should be risk assessed and regulated as an indispensable component of the RNAi delivery system. EPA does not risk assess adjuvants and surfactant chemicals in pesticides and may consider the nano-coatings to be a separate adjuvant. The May 9 EPA article states, “If a product is determined to contain a nanomaterial, then it will be subject to additional assessment or data needs from the manufacturer.”

Our assumption is that EPA will authorize for commercialize use nano-pesticides, if only conditionally, while waiting for more manufacturer data. Conditional registration has been characterized as a vast loophole in EPA’s risk assessment and regulatory process, since once a pesticide is commercialized, it is nigh to impossible to revoke the registration due to the manufacturer’s failure to provide EPA with the additional risk assessment or data.

If our assumption is correct, then NIOSH must begin now to prototype the commercial manufacture of effective PPE to prevent farmworker harm from inhaling nano-pesticides. EPA must work with agribusiness employers to ensure that EPA’s Agricultural Worker Safety Standard is implemented to include provision of and training in the use of nano-capable PPE for farmworkers. Otherwise, the “higher crop yields” that EPA believes will result from the use of nano-pesticides will come at the cost of farmworker health and safety.

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