(Beyond Pesticides, October 9, 2025) The 42nd National Forum Series, The Pesticide Threat to Environmental Health: Advancing Holistic Solutions Aligned with Nature—scheduled to begin on October 29, 2025, 1:00-3:30pm (Eastern time, US), will focus on aligning land management with nature in response to current chemical-intensive practices that pose a threat to health (see Pesticide-Induced Diseases Database), biodiversity, and climate. The virtual Forum is free to all participants. ➡️ Register here. The Call to the Forum, states: We are all affected by how land is managed, food is grown, and nature is protected. Different experiences and perspectives may bring us to care about health and the environment and the devastating adverse effects of pesticides and toxic substances. However, ensuring a livable future requires us to cultivate a collective concern about daily decisions on the management of our personal and community spaces, the practices used to grow the food we buy, and the care that we as a society give to complex and fragile interrelationships that sustain the natural world on which we depend.   The Pesticide Threat to Environmental Health: Advancing Holistic Solutions Aligned with Nature challenges participants—as concerned families, community residents, purchasers of products, advocates for policy, decision makers, and workers—to think […]

(Beyond Pesticides, October 8, 2025) A study, Pesticides detected in two urban areas have implications for local butterfly conservation, published in partnership with researchers at Xerces Society for Invertebrate Conservation, University of Binghamton (New York), and University of Nevada, reports widespread pesticide residues in the host plants of butterflies located in green spaces in the cities of Sacramento, California, and Albuquerque, New Mexico. Just 22 of the hundreds of collected samples had no detectable residues, with all other samples containing some combination of 47 compounds of the 94 tested pesticides in the plant tissue. Of the 47 compounds, 4 are neonicotinoid insecticides linked to adverse effects for bee and pollinator populations based on previous peer-reviewed research. The fungicide azoxystrobin and the insecticide chlorantraniliprole were detected at lethal/sublethal concentrations, according to the report authors. “Residential landscapes have high conservation potential for butterflies and other invertebrates,” says Aaron Anderson, co-lead author of the report and pesticide program specialist at Xerces Society for Invertebrate Conservation. He continues: “But, these findings show how pervasive pesticide contamination can be in towns and cities, and underscore that protecting wildlife in these areas includes addressing pesticides.” The report’s results underscore the pervasiveness of pesticide drift and dispel the myth […]

(Beyond Pesticides, October 2, 2025) This year marks an advancement of various state-level neonicotinoid laws and regulations, including in Maine, Vermont, and Connecticut—emphasizing surging public support for pesticide reforms. The Maine legislature passed, and Governor Janet Mills (D-ME) signed into law on July 22, 2025, LD 1323, which commissions the Board of Pesticide Control to study the impacts of neonicotinoids and neonicotinoid-treated seeds, which advocates hope will help advance future legislation to prohibit the use, distribution, and sale of neonicotinoid insecticide products. Meanwhile, after years of grassroots advocacy, the Connecticut legislature advanced, and Governor Ned Lamont (D-CT) signed SB 9 into law, which will partially restrict the nonagricultural use of neonicotinoids on turfgrass, starting in 2027. There was a more comprehensive effort that failed to move forward (HB 6916), which would have gone further by restricting or prohibiting the use of neonicotinoids on trees, shrubs, and treated seeds (see here for Beyond Pesticides comments). Maine and Connecticut join eleven other states (California, Nevada, New Jersey, Massachusetts, Maryland, Minnesota, New York, and Vermont) in taking steps to restrict or prohibit the use of neonicotinoids. (See Daily News here.) Whether it is a campaign to ban glyphosate, paraquat, chlorpyrifos, atrazine, or any […]

(Beyond Pesticides, September 24, 2025) A novel study of chronic toxicity of the neonicotinoid insecticide thiamethoxam to honey bees (Apis mellifera), published in Insects, finds sublethal effects that threaten the survival of bee larvae and the health of bee colonies. “We evaluated the effects of thiamethoxam on the entire larval development cycle of reproductive bees and conducted a comparative analysis, demonstrating that thiamethoxam significantly alters ecdysone [a hormone that controls molting in insects] and juvenile hormone titers [hormones for insect growth] in both queen and drone larvae, impairing metamorphosis and reproductive development,” the authors state. Risk assessments and scientific literature focus primarily on honey bee workers, rarely including how pesticides can impact queen and drone bees that are necessary for stable colonies. In focusing on this data gap, the researchers reveal that the survival rate of bee larvae decreases gradually with increasing doses of thiamethoxam, adding to the wide body of science on pesticide-related threats to honey bee health. (See Beyond Pesticides’ What the Science Shows on Biodiversity page for more information, as well as Daily News coverage on risk assessments here, here, and here.) Honey bees provide crucial ecosystem services as pollinating insects and play a vital role in […]

(Beyond Pesticides, September 11, 2025) A study published in Agriculture, Ecosystems & Environment finds organic rice paddies in the Mediterranean region have greater ecosystem biodiversity, including increased presence of aquatic microorganisms and insects, than their chemical-intensive counterparts. While not a “cradle-to-grave” or holistic analysis of organic vs. chemical-intensive agriculture (see a similar example in previous Daily News here), the authors note that there is an increase in greenhouse gas emissions (GHGe) associated with compost use, which replaces synthetic fertilizers. Typically, compost builds biological life in the soil and contributes to a drawing down (or sequestering) of atmospheric carbon. As EPA notes, “[C]omposting lowers greenhouse gases by improving carbon sequestration in the soil and by preventing methane emissions through aerobic decomposition, as methane-producing microbes are not active in the presence of oxygen.” The transition to organically produced rice in the U.S. has come with challenges. One includes thorny debates over the inclusion of copper sulfate on the National List of Allowed and Prohibited Substances, which establishes materials permitted for use in certified organic production under the Organic Foods Production Act (OFPA). Under the law, USDA restricts copper sulfate in organic farming as follows: “For use as tadpole shrimp control in aquatic […]

(Beyond Pesticides, September 10, 2025) After being criticized by the chemical industry and allied agribusiness and service industry groups on the Make America Healthy Again (MAHA) report in May, the strategy document, released yesterday, has tamped down efforts to reform government programs that regulate pesticides. There are no specific recommendations on improving the regulation of pesticides. Rather, the strategy appears to embrace business-as-usual and could even ramp up government efforts to tout the need for pesticides and claims that current regulatory reviews are effective and comprehensive. In a section of the strategy entitled “Increasing Public Awareness and Knowledge,” the document says: “EPA, partnering with food and agricultural stakeholders, will work to ensure that the public has awareness and confidence in EPA’s pesticide robust review procedures and how that relates to the limiting of risk for users and the general public and informs continual improvement.” This is at odds with the earlier MAHA assessment report which identified pesticides as substances of concern that, citing deficiencies in chemical reviews, “may be neglecting potential synergistic effects and cumulative burdens, thereby missing opportunities to translate cumulative risk assessment into the clinical environment in meaningful ways.” While the earlier report, Make Our Children Healthy Again: Assessment, […]

(Beyond Pesticides, September 9, 2025) SprayDays California, the pesticide notification and mapping tool run by the California Department of Pesticide Regulation (DPR), was updated in late August after public backlash (including from farmworkers), which identified inadequate notice of pesticide use to those who work in or live in proximity to agricultural fields. According to a DPR press release from August 28, these changes include attempts to bring down barriers for users so that, in the words of DPR Director Karen Morrison, the department can “provide Californians with access to information and services.” While public health advocates view notification as a step that may allow people to leave a treatment area or take shelter to reduce exposure, groups continue to express concerns about a focus on notification to the exclusion of addressing the root causes of exposure—chemical-intensive agriculture, despite the viability of organic compatible practices and products. The groups criticize the continuous registration of pesticide active ingredients and product formulations without considering widely available practices and nonchemical and nature-based alternatives to pest management. These include regenerative organic principles and practices that draw inspiration from Indigenous land management and agroecological systems that have thrived in coexistence with nature. Recent Updates There are […]

(Beyond Pesticides, September 8, 2025) Beyond Pesticides today called on Congress to require the U.S. Environmental Protection Agency (EPA) to incorporate real world science into its evaluation of pesticide safety calculations by recognizing that daily exposure involves multiple chemicals and synergistic interactions— a magnified effect greater than the individual chemical effects added together. The organization cites numerous scientific studies that call public attention to this issue; that a realistic assessment of the human and environmental harm potentially caused by pesticides cannot be evaluated based on single-chemical, single-species tests. Given the numerous complexities associated with this type of assessment, the group points to organic land management in agriculture and residential areas as a more cost-effective approach, sending this message to Congress: EPA must consider the effects of pesticides in the context in which they are used and with reference to the organic alternative. A recent study, covered by Beyond Pesticides in its Daily News, found that the presence of Varroa mites in combination with the neonicotinoid insecticide imidacloprid increases the risk of bee mortality and disrupts the larval gut microbiome. The study found synergy (a greater combined effect) between Varroa destructor, a parasitic mite that attacks and feeds on honey bees, and imidacloprid. The findings were published last […]

(Beyond Pesticides, September 4, 2025) A review of agricultural neonicotinoid insecticide regulations, published in Pest Management Science, evaluates the varied approaches being taken for bans and exemption-based restrictions in the European Union (EU), Canada, and the United States (U.S.). Despite an ever-growing and overwhelming body of science linking neonicotinoids (neonics) to adverse effects on pollinators and other nontarget species, the regulations fall short in protecting the environment and wildlife. The review, with the history and current status of neonics, lends further support for a full transition to organic agriculture and land management that removes neonicotinoid exposure routes and subsequent health threats. With the application of this widely used class of neurotoxic system insecticides increasing, so too has the concern over the long-term chronic effects on pollinators and other species from exposure. This concern, backed by scientific literature, has “led to increased governmental regulations since the mid-2010s, particularly in agricultural settings,” state the authors from Iowa State University and Washington State University. They continue, “These regulations have varied in terms of approach, geography, and timeline, starting with a ban implemented by the European Union (EU) and evolving into exemption-based regulations across two Canadian provinces and five U.S. states as of this […]

(Beyond Pesticides, September 3, 2025) A study in Environmental Entomology shows that habitat and open space near agricultural fields become a killing field of pesticides, threatening biodiversity due to contamination from toxic drift. The study detected 42 pesticides, including several neonicotinoids, which are among the most lethal threats to pollinators. The research reveals the complexity of pesticide flow through the environment and the inadequacy of current methods of protecting nontarget organisms, including honey bees, bumblebees, and hundreds of other species of native bees worldwide. Their catastrophic declines is tied to pesticides in large part and highlights the inadequacy of current pesticide reduction strategies, such as integrated pest management (IPM) and now other loosely defined concepts like “regenerative,” in an attempt to protect the environment and nontarget organisms in chemical-dependent land management and agriculture. (See What the Science Shows on Biodiversity.) The researchers on the study, from the U.S. Department of Agriculture, Cornell University and Michigan State University, put silicone bands on fence posts in open areas adjacent to highbush blueberry fields on 15 farms in western Michigan. Silicone takes up chemicals in the atmosphere which can then be extracted and analyzed. The fence posts were placed at seven intervals ranging […]

(Beyond Pesticides, September 2, 2025) It did not go without notice to U.S. grassroots environmental and public health advocates that earlier this month, over two million people in France signed a “first of its kind” petition that ultimately prevented the overturning of the country’s ban on bee-killing neonicotinoid insecticides. The action was widely covered in France, including in Le Monde. This uprising, organized by 23-year-old French master’s student Eleonore Pattery, emphasizes the importance of individuals in communities mobilizing people to protect the planet from pesticides that are having a devastating adverse effect on health and the environment. The grassroots push in France taps into a deep public concern about health and the environment that is emblematic of the level of public engagement needed to thwart the high level of chemical industry, agribusiness, and allied corporate influence that undermines basic protections. Industry interests have long been embedded in federal environmental and public health laws. For example, federal and state pesticide laws (the Federal Insecticide, Fungicide, and Rodenticide Act and similar state laws) allow widespread exposure to toxic chemicals despite the availability of nontoxic alternatives that are both efficacious and cost-effective. Without public engagement, as seen in France, significant improvements in law are constantly […]

(Beyond Pesticides, August 21, 2025) The presence of Varroa mites in combination with the neonicotinoid insecticide imidacloprid increases the risk of bee mortality and disrupts the larval gut microbiome, according to a study of the synergy (a greater combined effect) between Varroa destructor, a parasitic mite that attacks and feeds on honey bees, and imidacloprid. The study in Pesticide Biochemistry and Physiology adds to the growing body of science on the severely declining bee population by investigating the toxic effects of both the parasites and pesticide stressors in honey bees (Apis mellifera). “Given that V. destructor may increase bees’ sensitivity to imidacloprid by compromising their physiological health and immunity, this study systematically assesses the effects of V. destructor infestation and imidacloprid exposure on honey bee survival, detoxification enzyme activity, and gut microbiota,” the authors explain. The intestinal tract and gut microbiome are crucial for digestion, metabolism, nutrient absorption, immune regulation, and pathogen defense. Within honey bees, the gut microbiome is “highly susceptible to external environmental stressors, such as pesticide exposure and parasitic infections [and] these disturbances can lead to microbial imbalances, ultimately affecting bee health.” (See studies here and here.) Previous research earlier this year, captured in Daily News Variability […]

(Beyond Pesticides, August 20, 2025) As a part of a nationwide push to stop the use of petrochemical pesticides and fertilizers, Beyond Pesticides, in partnership with the City of Excelsior, Minnesota, and Osborne Organics, announced the transition of city park land sites to organic land management. Under its program, Parks for a Sustainable Future, Beyond Pesticides underwrites the development of organic transition plans and staff training on holistic practices. The goal of the program is to advance practical, resilient, cost-effective management techniques that confront urgent threats to public health, biodiversity, and climate that are exacerbated by toxic pesticide and fertilizer use. See the link to our press release here.  Excelsior City Councilmember Jennifer Caron said, “Excelsior has embarked on an exciting first step in organically managing our public parks and minimizing runoff into the lake.” Ms. Caron added: “By participating in the Parks for a Sustainable Future grant program with Beyond Pesticides, the city is learning how to eliminate herbicides, insecticides, and other pesticides on sites in the Commons, including the Ballfield and Great Lawn. The result will be a healthier Commons, particularly in areas heavily used by people, pets, and pollinators alike.”   Kevin Quinn, parks and natural resources manager for Excelsior, said: “Working with […]

(Beyond Pesticides, August 18, 2025)  With pesticide manufacturers pushing to stop cancer victims (and others suffering adverse effects) from suing them under longstanding ”failure to warn law,“ U.S. Senator Cory Booker (D-NJ) is proposing to uphold this unequivocal right to protection. Senator Booker has introduced the Pesticide Injury Accountability Act (S. 2324) to protect the rights of farmers and consumers to hold pesticide manufacturers responsible for the harm caused by their toxic products. This effort comes in the wake of congressional and state legislative attacks on “failure-to-warn” liability claims that are taking place in response to extraordinary jury verdicts against Bayer/Monsanto for harm caused by glyphosate weed killer products like Roundup.ᵀᴹ 📣 Beyond Pesticides, with allied organizations across the U.S., is asking the public to “Tell your U.S. Senator to co-sponsor S. 2324, the Pesticide Injury Accountability Act.” This bill will amend the Federal Insecticide, Fungicide, and Rodenticide Act of 1972 (FIFRA) to create a federal right of action for anyone who is harmed by a toxic pesticide.  Despite growing peer-reviewed scientific evidence linking widely used pesticides to a host of health harms, including cancers, birth defects, endocrine disruption, Parkinson’s disease, and infertility, the chemical industry and its allies in elective office are pushing to deny victims access to […]

(Beyond Pesticides, August 15, 2025) In analyzing the data present in an article in Data in Brief, concerning levels of pesticide biomarkers are present in the urine of adolescents and young adults that are linked to numerous health implications. The biomonitoring data, collected at two time points from participants in a longitudinal cohort study in the agricultural county of Pedro Moncayo, Ecuador, encompasses a total of 23 compounds used as herbicides, insecticides, and fungicides and their associated metabolites (breakdown products), which include organophosphates, pyrethroids, and neonicotinoids. The results highlight the disproportionate risks to a Latin American population that occur as a result of living in areas with heavy chemical-intensive agriculture. “This article presents urinary pesticide metabolite concentrations for 665 participants in the ‘Study of Secondary Exposure to Pesticides among Children, Adolescents, and Adults’ (ESPINA), which were collected during two follow-up assessments,” the authors describe. The first sampling period from July to October 2016, referred to as Follow-up Year [FUY]-8b, includes 529 of the participants, while the second sampling period from July to September 2022 (FUY-14a) includes 505 of the participants. All participants are within the agricultural community of Pedro Moncayo. As the authors note, “The ESPINA study aimed to include […]

(Beyond Pesticides, August 7, 2025) The novel study published in Arthritis & Rheumatology is the largest investigation of rheumatoid arthritis (RA) in women to date, finding evidence of heightened risks when exposed to insecticides through data collected from over 400 eligible women in the Agricultural Health Study (AHS). AHS participants include a cohort of thousands of licensed pesticide applicators and their spouses from Iowa and North Carolina, with this particular study as the first to consider the link between pesticide exposure and RA as it affects women’s health.   “Growing evidence suggests farming and agricultural pesticide use may be associated with rheumatoid arthritis (RA), but few studies have examined specific pesticides and RA among farm women, who may personally use pesticides or be indirectly exposed,” the study authors explain. The findings reveal that organochlorine insecticides that continue to persist in the environment, as well as organophosphate and synthetic pyrethroid pesticides used in public health or residential settings, correlate with RA diagnoses in women.  As shared in previous Daily News, for the most part organochlorine pesticides, including dichlorodiphenyltrichloroethane (DDT), are no longer used worldwide, but the legacy of their poisoning and contamination persists. These compounds are primarily made up of chlorine atoms, […]

(Beyond Pesticides, August 4, 2025) Comments on EPA proposal to bring back controversial use of herbicide dicamba due by Saturday, September 6, 2025, at 11:59 PM ET. With more than 90 percent of soybeans (also corn and the most common species of cotton) planted in varieties genetically engineered to be herbicide-tolerant, the agrichemical industry and industrial agribusiness are lining up to bring back agricultural spraying of the controversial weed killer dicamba—linked to crop damage associated with the chemical’s drifting off the target farms. The courts in 2020 and 2024 vacated EPA’s registration authorizing “over-the-top” (OTT) spraying of dicamba, leading to these uses being stopped in the 2025 growing season. (See Daily News.)              Genetically engineered crops, widely adopted in 1996 with Monsanto’s glyphosate-tolerant (Roundup Ready) soybean seeds and plants, have been plagued by weed resistance to the weed killers, movement of genetic material, chemical drift, and health and environmental hazards associated with pesticide exposure. Despite the problems and escalating herbicide use in chemical-dependent no-till (no tillage) agriculture, regulators at the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Agriculture (USDA) have facilitated the astronomical growth of a genetically engineered food system. The industry makes the environmental argument that less […]

(Beyond Pesticides, July 31, 2025) A study published in Environmental Advances finds that hundreds of honeybee hives across central and northern Italy are contaminated with various pesticides and their metabolites, including glyphosate and fosetyl.  “There was no significant difference in glyphosate presence between dead/dying and live bees, suggesting chronic exposure rather than acute toxicity. However, higher pesticide concentrations in dead/dying bees indicate potential sublethal effects contributing to colony distress,” according to the authors. This peer-reviewed study builds on the mounting evidence outlined in the literature connecting pesticide residues to nontarget harm to pollinators and other insects and animals that are critical to biodiversity. Background and Methodology “The primary objectives of this study were to develop and validate a reliable, sensitive method for analyzing polar pesticides [highly soluble in water] in honeybees and to investigate polar pesticides residue levels in honeybees across northern and central Italy,” say the researchers of this study, who conduct research at the Experimental Zooprophylactic Institute of Lombardy and Emilia Romagna “Bruno Ubertini”, Experimental Zooprophylactic Institute of Umbria and Marche “Togo Rosati”, and Experimental Zooprophylactic Institute of Lazio and Tuscany “M. Aleandri.” 314 honeybee samples were gathered voluntarily from local beekeepers in six regions of northern and […]

(Beyond Pesticides, July 23, 2025) The pesticide manufacturer Syngenta has settled several lawsuits in federal courts in Pennsylvania and Illinois in recent months and is seeking a global settlement with over 6,000 litigants in order to avoid nationwide trials linking their weed killer paraquat to Parkinson’s Disease, according to reporting by The New Lede and The Guardian, respectively. Internal Syngenta documents released by these news outlets in a report dubbed The Paraquat Papers indicate that the company was aware of scientific evidence linking paraquat to Parkinson’s and attempted to quash research efforts to disclose the evidence.   These lawsuits were filed on behalf of former farmers and agricultural workers who went on to be diagnosed with neurological disorders, including Parkinson’s Disease, after using paraquat-based herbicide products for long periods of time. This litigation comes at a time when pesticide manufacturers across the board are facing increased scrutiny and subsequent financial repercussions. Simultaneously, their allies in Congress are revamping their efforts to shield chemical manufacturers from “failure to warn” lawsuits and establish federal preemption of local state governments’ ability to regulate pesticides more stringently than the U.S. Environmental Protection Agency. Many of the paraquat lawsuits in federal courts, known as multidistrict […]

(Beyond Pesticides, July 21, 2025) Beyond Pesticides is asking every member of the U.S. Representatives to voice their opposition in advance of a vote as early as Tuesday, July 22 on a provision before the House Appropriations Committee—in the Interior-Environment Appropriations Bill—that shields pesticide companies from lawsuits by those harmed from pesticide product use and limits states’ authority to regulate pesticides. This is a fight to protect farmers’ and consumers’ right to sue pesticide manufacturers for misbranding products and their failure to warn product users. The language before the Committee is in Section 453 of the bill passed last week by the subcommittee on a straight party-line vote, with Republicans supporting the bill language. Beyond Pesticides is also asking Congress members to remove section 507, which prohibits EPA action on PFAS (per- and polyfluoroalkyl substances), including fluorinated pesticides.  Update from July 21, 2025, at 4 PM: ⏰ Representative Chellie Pingree (D-ME-1) moved forward with amendments to strike sections 453 and 507 of the FY26 Interior-Environment Appropriations Bill, which is a provision that provides immunity for pesticide manufacturers from farmer and consumer lawsuits seeking compensation from product harm. Update from July 23, 2025, at 10 AM: The FY26 Interior-Environment Appropriations Bill passed out of […]

(Beyond Pesticides, July 18, 2025) A study in Royal Society Open Science shows intraspecific differences (between individuals of a species) in wild bumblebees (Bombus vosnesenskii) exposed to an herbicide (glyphosate), a fungicide (tebuconazole), and an insecticide (imidacloprid), with gut microbiome health as a factor. “Wild pollinator declines are increasingly linked to pesticide exposure, yet it is unclear how intraspecific differences contribute to observed variation in sensitivity, and the role gut microbes play in the sensitivity of wild bees is largely unexplored,” the authors explain. “Here, we investigate site-level differences in survival and microbiome structure of a wild bumble bee exposed to multiple pesticides, both individually and in combination.” In collecting 175 individuals of this wild, foraging species from an alpine meadow, a valley lake shoreline, and a suburban park and exposing them to a diet with individual pesticides and mixtures, the researchers assess the varying lethal and sublethal effects that can occur with pesticide exposure. Between the three sites, the survival differences “emphasize the importance of considering population of origin when studying pesticide toxicity of wild bees” and highlight how pesticide sensitivity not only varies between species but within individuals of the same species with site-specific impacts. (See previous Daily […]

(Beyond Pesticides, July 17, 2025) The widespread use of pesticides year-after-year, decade-after-decade, has been found to lead to unintended consequences not only for public health but also for broader ecosystem stability and biodiversity. These impacts include potential nontarget harm through adverse developmental and reproductive effects on the vinegar fly, Drosophila melanogaster, the subject of a peer-reviewed study in Royal Society Open Science. The authors, who studied the organochlorine fungicide chlorothalonil, conclude, “Chlorothalonil exposure decreases larval survival, extends developmental duration and reduces fecundity.” “Even at the lowest tested concentration, chlorothalonil exposure resulted in reduced body weight, ovariole count and egg production compared with non-exposed individuals,” the researchers find. This study builds upon years of scientific research findings and critiques of existing federal pesticide law, as well as the U.S. Environmental Protection Agency’s (EPA) failure to fully assess the adverse impacts on biodiversity and ecosystem stability during the pesticide registration review process. Methodology and Background The goal of this study is to evaluate the health impacts on a nontarget insect species (Drosophila melanogaster) from chronic exposure to chlorothalonil. This specific fungicide was chosen for various reasons, including its wide use across cereals, vegetables, and fruits; evidence linked to adverse health effects on […]

(Beyond Pesticides, July 16, 2025) A study following a mass mortality event of approximately 200 monarch butterflies (Danaus plexippus plexippus) in Pacific Grove, California, highlights the role of pesticides, synthetic pyrethroids in particular, in causing lethal and sublethal effects to nontarget organisms. The research, published in Environmental Toxicology and Chemistry, detects residues of 15 pesticides and associated metabolites in the bodies of 10 deceased butterflies collected from the January 2024 event that occurred near an overwintering site frequented by monarchs. “On average, each monarch butterfly contained 7 pesticides,” the authors report. They continue, “Notably, three pyrethroid insecticides—bifenthrin, cypermethrin, and permethrin—were consistently detected at or near each chemical’s lethal dose (LD50).” LC50, or Lethal Concentration 50, values represent the concentrations of chemicals lethal to 50% of a test population. To assess pesticide residues within ten of the deceased butterflies, the researchers use liquid and gas chromatography with tandem mass spectrometry (LC-MS/MS and GC-MS/MS) and find “a total of 15 pesticides and associated metabolites in the butterflies, including 8 insecticides (plus 1 associated metabolite), 2 herbicides (plus 2 associated metabolites), and 2 fungicides.” The study “present[s] evidence that the mortality incident at the Pacific Grove Monarch overwintering site was likely caused by […]