15
May
Pesticide Use Again Linked to Inflammatory Bowel Disease, This Time Among Applicators and Their Spouses
(Beyond Pesticides, May 15, 2024) A study published recently in the journal Environmental Research finds a significant correlation between exposure to certain pesticides and an elevated risk of inflammatory bowel disease (IBD), a chronic autoimmune condition of the gastrointestinal tract. The study, adding to the body of science on this subject, evaluates self-reported data from licensed pesticide applicators and their spouses exposed to pesticides for over 20 years. In addition, while some of the chemicals found to be most closely associated with incidents of IBD have been banned from use, they are “forever†chemicals that persist in the environment for generations. These findings demonstrate once again the failings of the current regulatory process to identify hazards before they are put into the environment.
The study found evidence that exposure to several organochlorine insecticides (dieldrin, DDT, and toxaphene), as well as organophosphate insecticides (parathion, terbufos, and phorate) and herbicides (2,4,5-T, 2,4,5-TP, and metolachlor), is associated with elevated IBD risk. IBD is a generic term for diseases that result in chronic inflammation of the gastrointestinal tract, such as Crohn’s disease and ulcerative colitis. It is estimated that 6.8 million patients globally suffered from IBD in 2017.
IBD may result from an imbalance in gut microbiota, known as dysbiosis, which can increase the gut’s susceptibility to infection and trigger an autoimmune response. The Environmental Research study cites increasing evidence linking specific pesticides, including chlorpyrifos, glyphosate, organochlorines, organophosphates, carbamates, and other classes of pesticides to dysbiosis and related gastrointestinal issues.
Of particular concern is that at least two of the chemicals most closely associated with IBD, dieldrin, and DDT, are part of the “dirty dozen†forever chemicals identified by the United Nations as Persistent Organic Pollutants (POPs). POPs are the subject of a 2001 international treaty, The Stockholm Convention on Persistent Organic Pollutants, that aims to eliminate or restrict the production and use of POPs, chemical substances that persist in the environment, bioaccumulate through the food web and particularly in fatty tissues, and pose risks to human health and the environment. Pesticides represent a significant portion of compounds designated as POPs. (See previous Beyond Pesticides reporting).
In addition to general exposure information for all pesticides, additional information was collected for each of the 50 specific pesticides, including duration and frequency of use. This data was used to determine an intensity score that accounted for the duration and frequency of lifetime pesticide use, as well as variations in exposure due to workplace practices (e.g., use of personal protective equipment). The intensity score was multiplied by the lifetime days of use to generate the cumulative intensity-weighted lifetime days (IWLD). This methodology enabled researchers to compare the impacts of repeated exposure to pesticides or combinations of pesticides. While the data for the IWLD analysis was limited, the researchers observed positive correlations between IBD and IWLD.
For the study, data was compiled from a series of questionnaires completed by over 52,000 licensed private pesticide applicators (principally farmers) and over 32,000 spouses of applicators in North Carolina and Iowa between 1999-2003 and 2019-2021. The questionnaire collected information about the duration and frequency of use of any agricultural pesticides, with follow-up questions about 50 specific chemicals.
Cases of IBD are identified for participants who either were diagnosed by a doctor or who self-reported the condition following the date of enrollment in the study. Personal information for each respondent was also collected, including sex, age, and educational level. Participants were primarily white and 20% had a college degree. Those who were found to be more likely to suffer from IBD are older, female, ever-smokers, and received more than a high school education.
Blind Spot of EPA Regulations: Pesticides Synergist Effects
One aspect of pesticide exposure the study did not evaluate is the correlation of IBD and exposure to specific combinations of pesticides, a glaring and continuing blind spot that U.S. Environmental Protection Agency (EPA) risk analyses do not address: synergistic effects of pesticides.
As Beyond Pesticides reported in April this year, a 2024 Chemosphere study identified synergistic effects in specific chemical combinations, challenging the traditional assumption that such interactions are merely additive. The study indicates that environmental mixtures of chemicals could lead to more dangerous compounds. Researchers “used the exposure data from a complex operating site with legacy pesticide pollution to evaluate if …the component-based risk assessment approaches that rely on additivity can predict the actual risk of pesticides in a mixture, and the legacy organochlorine pesticides banned many years ago interact with registered and supposedly safe herbicides in a mixture.†Specifically, it was found that most binary mixtures of organochlorine pesticides exhibit synergistic effects at higher concentrations, except for the combination of lindane and dieldrin, which remained additive at all concentrations.
These findings, along with similar research stretching back decades, underscore the critical and continued weakness in EPA pesticide regulation of pesticide chemical mixtures which renders the agency ineffective at developing pesticide safety regulations. Beyond Pesticides has long argued that the most effective answer to this regulatory failure is to abandon use (and the subsidizing of conventional agriculture’s use of) synthetic pesticides and fertilizers in favor of effective and viable organic and organic regenerative agricultural methods that do not require or allow use of petrochemical pesticides and fertilizers.
While the participants in the study were all male caucasian licensed pesticide applicators, the exposure pattern suggests that farmworkers face similar, if not worse, exposure patterns.  In February, Beyond Pesticides highlighted the latest in a series of reports on the state of farmworker protection published by Vermont Law School’s Center for Agriculture and Food Systems (CAFS), which found that farmworkers “face a level of occupational risk unrivaled by most workers.†Farmworkers and their families suffer a disproportionate burden of the hazards. For more information, see Beyond Pesticides’ webpage on Disproportionate Risk and Agricultural Justice.
Farmworkers’ toxic chemical exposure does not fall under the jurisdiction of the U.S. Department of Labor’s Occupational Safety and Health Administration (OSHA) like almost every other worker in the U.S. Instead, it is directed by the Worker Protection Standards (WPS) administered by EPA under the Federal Insecticide, Fungicide, and Rodenticide Act. The CAFS report outlined how state and federal enforcement of pesticide safety regulations are weak and unreliable… [and] the cooperative agreement[s] between federal and state agencies makes it nearly impossible to ensure implementation of the WPS.†The report goes on to note “Encouraging growers to transition to organic agriculture is a worthwhile strategy for mitigating the harm from the most toxic pesticides.â€
The results of the Environmental Research study confirm a 2020 review of scientific literature by researchers at the University of Illinois on the toxic effect of environmental contaminants including pesticides published in the journal Toxicological Science in 2020 (previous reporting here). This review found that environmental contaminants are associated with changes in the gut microbiome and other adverse health implications.
Gut microbiota play a crucial role in lifelong digestion, immune, and central nervous system regulation. Through the gut biome, pesticide exposure can enhance or exacerbate the adverse effects of additional environmental toxicants on the body. With prolonged exposure to various environmental contaminants, critical chemical-induced changes may occur in the gut microbes, influencing adverse health outcomes. Karen Chiu, PhD, a graduate research fellow at the University of Illinois, states, “All of these data together suggest that exposure to many of these environmental chemicals, during various stages of life, can alter the gut microbiome in ways that influence health.â€Â
Over 300 environmental contaminants and their byproducts, including pesticides, bisphenols, phthalates, persistent organic pollutants (POPs), and heavy metals, are all chemicals commonly present in human blood and urine samples. These toxicants can alter hormone metabolism, which adversely affects health outcomes. Adverse health effects of environmental contaminants include reproductive and developmental defects, diabetes, cardiovascular disease, liver disease, obesity, thyroid disorders, and improper immune operation. Although studies show how chemical exposures affect human health, more research questions how these chemicals influence gut microbiota.
There is extensive research surrounding gut dysbiosis associated with exposure to heavy metals like mercury, cadmium, lead, and arsenic in aquatic organisms, rodents, birds, and larger mammals. Dioxins also increase the formation of antibiotic-resistant genes and disrupt the gut microbiome, as well as lipid and glucose metabolism. According to multiple studies, exposure to the weed killer glyphosate (patented as an antibiotic) changes the bacterial composition of the gut microbiome in cattle, rodents, and honey bees. Chlorpyrifos pesticides alter gut microbe populations in developing and adult male rodents and fish. New findings suggest exposure to the pesticide atrazine, diazinon, glyphosate-based herbicides, and trichlorfon cause sex-specific shifts in gut microbiota.
Dr. Chui concludes, “The pathologies associated with altered microbiomes after exposure to environmental chemicals include immune dysfunction, altered carbohydrate and lipid metabolism, and neurological and behavioral impairments. We are also seeing that these effects highly depend on an individual’s sex and age.â€
To improve and sustain gut microbiome health, the use of toxic pesticides must stop. Instead, adopting regenerative-organic systems and eliminating petrochemical, synthetic pesticides and fertilizers will mitigate harmful exposure to pesticides, restore soil health, protect water quality and environmental biodiversity, while reducing carbon emissions. Public policy must advance this shift, rather than continue to allow unnecessary reliance on synthetic pesticides. Learn more about soil microbiota and its importance here in Beyond Pesticides’ journal Pesticides and You. Additionally, learn more about the effects of pesticides on human health by visiting Beyond Pesticides’ Pesticide-Induced Diseases Database. This database supports the clear need for strategic action to shift away from pesticide dependency.Â
Together, these studies highlight the importance of evaluating how environmental contaminants like pesticides impact body regulation by gut microbiota and have significant implications for considerations that should be, but are not currently, a part of pesticide review and registration by EPA.
The ongoing expansion and embrace of organic farming and land management indicates a positive shift away from reliance on harmful chemicals and petrochemical-based pesticides. To help support the move away from these toxic petrochemical pesticides, see Tools for Change to find resources and methods for mobilizing your community against the use of toxic pesticides. See Eating With A Conscience to understand the risks of pesticide exposure through commonly eaten fruits and vegetables, while considering the health benefits of eating organic (plus how to eat organic on a budget). For current research on the negative health effects of herbicides, pesticides, and fungicides, check out the Gateway on Pesticide Hazards and Safe Pest Management and the Pesticide-Induced Disease Database.
For more about disproportionate harm to farmworkers from pesticide use in conventional agriculture and why organic certification should recognize Agricultural Justice issues, see Beyond Pesticides’ Keeping Organic Strong and Agricultural Justice webpages.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Sources:
Pesticide use and inflammatory bowel disease in licensed pesticide applicators and spouses in the Agricultural Health Study, Environmental Research, May 15, 2024
The Impact of Environmental Chemicals on the Gut Microbiome, Toxicological Sciences, August 2020
Herbicides and pesticides synergistically interact at low concentrations in complex mixtures, Chemosphere, April 2024
Pesticide Production Leaves a Legacy of Poisoning and Contamination – Beyond Pesticides Daily News Blog, June 30, 2014
What’s the point of farming if you’re going to make all the farmers disabled? You save money by avoiding organic methods and then you spend ten times more for healthcare costs.
May 16th, 2024 at 12:16 am