25
Jan
Common Antimicrobial Pesticides Linked to Altered Gut Microbe Function
(Beyond Pesticides, January 25, 2022) Research at the University of North Carolina at Chapel Hill identifies how triclosan (TCS), an antimicrobial agent used in many household products, impacts the microbial communities in the gut, causing inflammation. According to the study published in Nature Communications, triclosan worsens the effects of ulcerative colitis, an inflammatory bowel disease (IBD), through the retention of harmful bacteria. Ample evidence demonstrates environmental contaminants, including pesticides like triclosan, negatively affect microbes in the human mouth and gut. Although studies show how triclosan exposure affects human health, more research is now questioning how exposure to these toxic chemical influences gut health. Therefore, studies like these highlight the importance of evaluating how chemical contaminant deregulates normal bodily function through microbiome changes. Furthermore, the study has significant implications for considerations that should be, but are not currently, a part of pesticide review and registration by the U.S. Environmental Protection Agency (EPA). The researchers note, “Together, our results define a mechanism by which intestinal microbes contribute to the metabolic activation and gut toxicity of TCS, and highlight the importance of considering the contributions of the gut microbiota in evaluating the toxic potential of environmental chemicals.”
Instances of intestinal bowel disease (IBD)—involving the chronic inflammation of intestinal tissues—incidences and prevalence are readily increasing. As many as 3 million U.S. adults suffer from some form of IBD, with the year 1999 representing a 50 percent increase in disease cases. Disease symptoms include stomach pain, diarrhea, rectal bleeding, and an increased risk of developing colorectal cancer. IBD has no cure, and current treatments can have severe side effects. Although the study notes environmental chemical exposure has links to IBD prevalence, the researchers aim to uncover the mechanisms driving gut microbe disruption.
University researchers sought to identify the molecular mechanisms involved in triclosan’s toxic effects on the gut. The scientists employed in vitro (artificial environmental), ex vivo (outside the organism), and in vivo (inside the organism) analyses on microbial communities in the gut of mice. Specifically, researchers investigated specific bacterial enzymes involved in triggering triclosan toxicity through metabolization. The study results find that microbial β-glucuronidase (GUS) enzymes are responsible for metabolically activating triclosan within the colon, driving gut toxicity. Conversely, inhibition of this bacterial enzyme decreases the gut inflammatory effects of triclosan, thus showcasing the impact specific microbes play in chemical toxicity.
Gut microbiota plays a crucial role in lifelong digestion, immune, and central nervous system regulation, as well as other bodily functions. Through the gut biome, pesticide exposure can enhance or exacerbate the adverse effects of additional environmental toxicants on the body. Since the gut microbiome shapes metabolism, it can mediate some toxic effects of environmental chemicals. However, with prolonged exposure to various environmental contaminants, critical chemical-induced changes may occur in the gut microbes, influencing adverse health outcomes. Over 300 chemical contaminants and their byproducts are common in human blood and urine samples. Most chemical contamination affecting the gut comes from a diet reliant on conventional, pesticide-laden, highly processed foods. In a 2020 study, researchers associated developmental defects, diabetes, cardiovascular disease, liver disease, obesity, thyroid disorders, and improper immune operation with changes to the gut after exposure to environmental contaminants. Despite the growing body of work linking gut bacteria to overall health, pesticide regulators generally overlook the concept. Therefore, regulators must consider the emerging science on the dangers of pesticides beyond the mortality of humans, animals, and plants to include overall health and fitness.
A bioinformatics tool developed by researchers from the University of Turku in Finland indicates that “54% of species in the core human gut microbiome are sensitive to glyphosate.” (See Daily News.) Published in the Journal of Hazardous Materials, the researchers’ paper states, “The widespread use of glyphosate may have a strong effect on gut microbiomes as well as on human health.” Bats foraging in chemical-intensive banana plantations have much less gut diversity than bats foraging in organic banana fields and natural forestland, finds research published this month in the journal Frontiers in Ecology and Evolution. (See Daily News.)
Triclosan is an antimicrobial agent in products regulated by EPA and FDA. However, cumulative exposure to triclosan registered by both agencies poses unacceptable risks to human health and the environment. Many studies identify the various health and environmental effects of triclosan as the chemical absorbs through organs, from the skin to the gastrointestinal tract, and are environmentally persistent. Several independent, peer-reviewed research studies have identified triclosan as an endocrine-disrupting chemical. On top of its endocrine-disrupting effects, recent work shows that triclosan is a possible human carcinogen. Similar to this study, a 2016 peer-reviewed study published in the Annual Review of Pharmacology and Toxicology found that triclosan promotes cancer cell development in mice through pathways shared with humans. Furthermore, like many antimicrobial and antibacterial products, triclosan use increases the persistence of antibiotic-resistant bacteria, a severe public health concern for disease risk. Despite these findings, EPA’s evaluation of triclosan fails to address one of the most concerning aspects of its chemical activity concerning human and environmental health.
While people who use triclosan products daily have higher concentrations in their bodies, consumers who do not use triclosan can still encounter the chemical through food, water, and dust. Although FDA banned triclosan from soap products in 2016, other personal care products still contain the chemical. These products include toothpaste, mouthwash, hand sanitizers, cosmetics, and antibacterial/antimicrobial clothing. However, EPA and FDA evaluate different use of triclosan, with EPA responsible for assessing the chemical in various consumer products, marketed as “microban.” Therefore, individuals may encounter multiple sources of triclosan, especially on consumer products, such as toothbrush bristles, that tend to accumulate the chemical.
To improve and sustain gut microbiome health, the use of toxic pesticides are problematic. Although EPA denied a petition by Beyond Pesticides and Food and Water Watch to remove remaining triclosan uses in 2015, this study adds to growing evidence demonstrating the danger of this chemical. The data suggests that adequate public health protection requires EPA and FDA to work together to eliminate health risks from ongoing exposure to triclosan. Beyond Pesticides holds that safer alternatives are available, and organic practices can protect public health and the environment. In addition to positive impacts on the human microbiome, organically grown food (i.e., milk, meat, strawberries, tomatoes, and a range of other foods) contain a much more diverse bacterial community than their conventional counterparts. Moreover, emphasis on converting to regenerative-organic systems and using least-toxic pest control to mitigate harmful exposure to pesticides, restore soil health, and reduce carbon emissions, should be the main focus. Learn more about soil and gut microbiota and its importance via Beyond Pesticide’s journal Pesticides and You. Additionally, learn more about the effects of pesticides on human health by visiting Beyond Pesticides’ Pesticide-Induced Diseases Database, which supports the clear need for strategic action to shift from pesticide dependency. For a complete history of the regulation of triclosan, see Beyond Pesticides’ triclosan timeline and webpage on triclosan.
All unattributed positions and opinions in this piece are those of Beyond Pesticides
Source: Nature Communications, Science Daily
