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Digestive tract

Human Microbiome

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See also pesticides in food , glyphosate, antimicrobials

Environmental Pesticide Exposure Alters Gut Microbes, Increasing Urgency for Organic Transition    UK study. (Beyond Pesticides, May 12, 2022) A report published in Environmental Health finds that exposure to environmentally relevant concentrations of pesticides can alter gut microbial communities, as demonstrated through fecal samples. Over 300 environmental contaminants and their byproducts, including pesticides, are chemicals commonly present in human blood and urine samples.     The report finds all urine samples contain pyrethroid or organophosphate insecticide residues, with 53 percent of urine samples containing glyphosate. Individuals who consume more  fruits and vegetables grown with chemical-intensive practices have higher concentrations of organophosphate residues. Although urinary metabolite (pesticide breakdown product) excretion lacks a correlation with gut microbial changes, there are 34 associations between the concentration of pesticide residues and metabolite residues in fecal matter and gut health.   SNAP comment: There are more than 80,000 chemicals on the market. Only a few have been tested for presence in humans.

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. SNAP Comments: Astounding that no one cosnidered that an antimicrobial pesticide added to commonly used consumer products would have an effect on gut or other bacteria. One has to wonder...' "Health Canada has approved 64 marketed drug products with a DIN that contain triclosan. These are not all hand sanitizers ― some are soaps, hand washes and toothpastes," a Health Canada spokesperson said in an email'. (What happened to triclosan? A lingering legacy of the hyper-hygiene era. Kelly Crowe,CBC, 20 April, 2019)

Glyphosate-induced gut microbiota dysbiosis facilitates male reproductive toxicity in rats (Sci Total Environ. 2022 Jan 20;805: Epub 2021 Sep 16,2021).   'Data showed that GLY(phosate)-exposed rats exhibited male reproductive dysfunction, evidenced by impaired testis architectural structure, reduced sperm motility, together with increased sperm malformation ratio....these findings uncover an underlying mechanistic scenario that gut microbiota dysbiosis-driven local IL-17A production is one reason responsible for male reproductive toxicity induced by GLY, which provides new insights into the male reproductive toxicity of GLY in mammals. '

Research Shows Adverse Impacts of Glyphosate on the Human Gut Microbiome   (Beyond Pesticides, April 30, 2021) 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.”  ...The researchers’ bioinformatic method categorizes EPSPS enzymes into four classes, each of which has a different sensitivity to glyphosate, with one of the four classes being particularly vulnerable.  In addition, the co-authors suggest that glyphosate may impact other metabolic pathways (beyond the Shikimate), positing that the mitochondria electron transport chain appears sensitive to the compound.

Pesticide Exposure Alters Bacterial Diversity in the Mouth (Beyond Pesticides, December 6, 2016) A new study released by researchers at the University of Washington, Seattle finds that exposure to organophosphate insecticides is associated with changes in oral bacterial diversity, particularly for exposed farmworkers. The study provides insight into the far-reaching changes pesticide exposure can cause to the human body, which are not captured by current risk assessment models used by the U.S. Environmental Protection Agency (EPA). Although past research has investigated the impact of pesticide exposure on the gut microbiome, this is one of the first studies to look at oral bacterial diversity...Scientists focused on exposure to the organophosphate insecticide Azinphos-methyl (AZM), which at the time of the study (2005-2006) had not begun its cancellation proceedings...Of the farmworkers that have detectable levels of AZM in their blood stream, scientists found “significantly reduced abundances of seven common taxa of oral bacteria, including Streptococcus, one of the most common normal microbiota in the mouth,” ... Researchers found that while reductions in bacterial diversity start in the heavy pesticide use season of spring/summer, they remain low into the winter. SNAP Comment: The last allowed retail sale of Azinphos-methyl in Canada is dated on the label as 2011-12-31. Chlorpyrifos has also been found to cause dysbiosis in several areas of the digestive tract. There are still 29 Chlorpyrifos products registered in Canada. It is disappointing that studies take so long to be published. It is likely that other pesticides have the same effects. 

Parkinson's linked to gut bacteria  (Robert Ferris, CNBC, 1 December 2016) The scientists published their findings Thursday in the journal Cell. 'The germ-free mice were still overproducing alpha-synuclein, but their brain cells were not accumulating the protein. The germ-free mice showed fewer symptoms and performed better on a series of motor skills tests meant to model the kinds of tests given to human patients.' More experiments determined that what gut flora produces affects the development of Parkinson's. SNAP Comments: Several pesticides and other toxins have been linked to Parkinson's in the past. Now we also know from research that some pesticides, including glyphosate, affect the health of gut bacteria, usually suppressing good flora and promoting bad. The effects of a pesticide on gut flora are not required tests for pesticide registration. Of course use of antibiotics and what one eats is also important, but remember that people eating conventional food ingest several pesticides on a daily basis. Evidence is accumulating that gut flora is extremely important to the maintenance of health and the development of many diseases. I sincerely hope that more pesticide and toxins regularly found in our environment start being tested for their effect on gut flora. That research would provide a mechanism of action.


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also see glyphosatesoils, bee die-offSulfoxaflor and flupyradifuronefungicides, mixture effects, fungicides

Study Elevates the Connection Between Pesticides, the Gut-Brain Axis, and Disease(Beyond Pesticides, June 27, 2023)  A new review article by Irish and Dutch researchers in the ISME Journal adds to the emerging scientific literature examining how pesticides affect the relationship between the human gut and the human brain (the “gut-brain axis”). Often called the “second brain” because it houses nerve cells and produces neurotransmitters, the gut-brain axis may be the most important locus where microbes and pesticides meet.    Pesticides may exert influence over any or all of 'gut-brain processses". They may also affect the immune system, and some, such as glyphosate, can cross the blood-brain barrier. Pesticides can affect the production of many chemicals by gut bacteria, including serotonin and gamma-aminobutyric acid (GABA), both important neurotransmitters. They are also notorious for disrupting the endocrine system, including reproductive hormones; 

Common Fungicide Adds to Growing List of Pesticides Linked to Gastrointestinal and Microbiome Damage   (Beyond Pesticides, January 26, 2023) A study published in Food Safety and Toxicology finds that the widely used fungicide azoxystrobin (AZO), used in food production and turf management, can disrupt the function of the intestinal (colonic) barrier responsible for the absorption of nutrients and defense against harmful substances.  The results reveal AZO exposure altered the metabolic profile of microbes in the gut, inducing gut dysbiosis, leading to structural damage of the colon and colonic inflammatory response. Although the L-AZO (low dose) treatment group experiences no changes in body weight compared to the control group, the H-AZO (high dose) treatment group has significantly reduced body weight and weight gain. SNAP comment: Azoxystrobin does not seem to be currently registered by the PMRA in Canada.

Pesticide Mixtures Reduce Life Span of Honey Bees, Damage Gut Microbiome    (Beyond Pesticides, November 1, 2022) Study done with field relevant concentrations. 'Honey bees exposed to a combination of multiple pesticides suffer a reduced lifespan and experience adverse changes to their gut microbiome, increasing susceptibility to pathogens and disease. This finding comes from a study published recently in Science of the Total Environment, which examines the interactions between the insecticides flupyradifurone and sulfoxaflor and the fungicide azoxystrobin on honey bee health.   As the present study reveals, pesticide risk assessments do not inadequately capture the range of harm that can result when pesticides are combined, necessitating a shift toward safer, alternative, and regenerative organic farming systems that do not use these dangerous chemicals.For the initial experiment on individual bees, those exposed to flupyradifurone fared the worst, experiencing significantly reduced survival (50% reduction). The addition of azoxystrobin did not significantly add to this effect. However, with sulfoxaflor, it did. Bees subjected tsulfoxaflor and azoxystrobin in combination experienced significantly reduced survival when compared to a sole sulfoxaflor exposure.'     All experimental groups 'show significantly increased abundance of Serratia spp. This rod-shaped bacteria can serious harm honey bee fitness. “These bacteria are pathogenic and harmful to bees’ health,” said Dr. Al Naggar. “They can make it harder for the insects to fight off infection, leading to premature death.”  

Review Provides New Insight into How Pesticide Exposure Disrupts Bee Gut Microbiome    (Beyond Pesticides, February 16, 2022) 'Pesticide exposure disturbs the gut microbiome of social bees, leading to a range of alterations that could affect fitness in the wild, finds a major literature review recently published by researchers at the University of Ottawa, Canada.   Studies showed that pesticide use can disturb and shift the abundance of certain microbes in the bee gut microbiome, but rarely are these microbes completely eliminated. In general, researchers found declines in Bifidobacteriales and Lactobacillus bacteria to be the most common shifts observed.   Pesticides induced disturbances primarily in one of two ways – either directly harming microbes, and indirectly harming the host (bee) health and subsequently shifting the microbiome.Researchers cite glyphosate as an example of a pesticide that directly harms the growth of certain gut microbes.   The literature review also found that, regarding the impacts of exposure, the duration of pesticide exposure was more important than the amount of pesticide to which a bee was exposed. '

Glyphosate Kills Microorganisms Beneficial to Plants, Animals, and Humans   (Beyond Pesticides, October 28, 2021) A study published in Frontiers in Environmental Science finds the popular herbicide glyphosate negatively affects microbial communities, indirectly influencing plant, animal, and human health. Exposure to sublethal concentrations of glyphosate shifts microbial community composition, destroying beneficial microorganisms while preserving pathogenic organisms. 

Conventional Agriculture Decreases Diversity of Gut Bacteria in Foraging Bats (Beyond Pesticides, September 29, 2021) 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..  Gut diversity in organic bats was found to be similar to the diversity analyzed in forest bats. The study indicates that it is likely that organic practices are maintaining a “high diversity of commensal microbiota,” while on the other hand, “less diverse gut microbiota in bats foraging in conventional monocultures may suggest that these habitats potentially have negative physiological consequences for the animals (e.g., gut inflammation and metabolic disease), and may act as ecological trap.” 

Implications for Human Health: Pesticides and Other Environmental Contaminants Alter Gut Microbiome   (Beyond Pesticides, June 30, 2020) 'A review of scientific literature on the toxic effect of environmental contaminants—including pesticides—published in the journal Toxicological Science, “The Impact of Environmental Chemicals on the Gut Microbiome,” associates these chemicals to changes in the gut microbiome and other adverse health implications.    Multi-species evaluations find that various pesticides (i.e., insecticides, herbicides, and fungicides) alter the gut microbiome, lipid metabolism, and cause intestinal inflammation and oxidative stress. Specifically, the review mentions that exposure to pesticides glyphosate and chlorpyrifos, as well as other registered pesticides, increases anxiety and depression symptoms in mice, pathogenic bacteria in cattle, and inflammation and oxidative stress in the gut.'

Glyphosate and Roundup disrupt gut microbiome, contradicting regulator’s assumptions, study says (GM Watch,:December 11 2019) with link to original paper.  'The study in rats by an international team of scientists... has found that Roundup herbicide and its active ingredient glyphosate cause a dramatic increase in the levels of two substances, shikimic acid and 3-dehydroshikimic acid, in the gut, which are a direct indication that the EPSPS enzyme of the shikimic acid pathway has been severely inhibited.  In addition, the researchers found that both Roundup and glyphosate affected the microbiome at all dose levels tested, causing shifts in bacterial populations.  For the study, female rats (12 per group) were fed a daily dose of either glyphosate or a Roundup formulation approved in Europe, called MON 52276. Glyphosate and Roundup were administered via drinking water to give a glyphosate daily intake of 0.5 mg, 50 mg and 175 mg/kg body weight per day (mg/kg bw/day), which respigestive tract.microbiomeectively represent the EU acceptable daily intake (ADI), the EU no-observed adverse effect level (NOAEL), and the US NOAEL  The study found certain adverse effects at all doses tested, disproving regulators’ assumptions that these levels have no adverse effect.  Dr Antoniou said that the study has broken new ground in identifying the first ever biomarker of glyphosate exposure, which could be relevant to humans.  The study also revealed that Roundup, and to a lesser extent glyphosatedamaged the liver and kidneys of the rats, even over the relatively short study period of 90 days.' However, these changes were not reflected in blood chemistry.   ''Thus far, regulators have not incorporated these methods into the risk assessment process.'   SNAP COMMENT: Note the large difference between the EU and US no-observed adverse effect level (NOAEL). It illustrates the role of interpretation and lack of rigorous science when the US (and likely Canada) can have a 3 1/2 times higher NOAEL the the EU, presumably from the same background studies. And now, this study provides evidence that serious effects occur at those levels anyways,further illustrating.the severe limitations of basing approval of pesticides on regulatory studies only.

Toxic Herbicide Atrazine Causes Wasp Gut Microbiome to Develop Pesticide Resistance Across Generations  (Beyond Pesticides, February 11, 2020)   This study not only represents one of the first evolutionary studies on symbiont-mediated pesticide resistance, it also provides fodder for future research regarding the implications of exposure to xenobiotics (i.e., chemical substances like toxic pesticides foreign to an organism or ecosystem) for other gut bacteria hosts – such as honey bees and humans. Early generations of wasps in the study received a field-realistic dose of atrazine (300 ppb) or a subtoxic dose (30 ppb); exposed individuals showed a gut flora composition significantly different from the control group. The shift in microbiome composition persists across subsequent generations.   After the 8th generation of sublethal dosing, there was a significant increase in tolerance to atrazine. LC50 increased in later generations of the atrazine-exposed population, indicating pesticide resistance. The paper reads, “Our study is one of the few cases to experimentally evolve cooperation between a host animal and rare members of the microbiome to derive new fitness traits within the population.”   Even when wasps are switched to an atrazine-free diet for six generations, the bacterial composition was similar to that of the exposed parents. Overall, researchers observed an increase in microbiota diversity and bacterial load.'

also see pesticide fact sheets/malathionatrazine, glyphosate,  Endocrine Disruption/disease, nervous system effects/Parkinson Disease, herbicides

Pesticide Exposure and the Link to Irritable Bowel Syndrome (IBS)    Spanish study. (Beyond Pesticides, March 2, 2023) Populations experiencing higher levels of environmental pollutant exposure, specifically pesticides, also experience a higher rate of irritable bowel syndrome (IBS), according to a study published in Environmental Toxicology and Pharmacology. In the two areas, insecticides, including organophosphates chlorpyrifos, N-methyl carbamates, macrocyclic lactones, neonicotinoids, and pyrethroids, are commonly used. Fungicides (i.e., di thiocarbamates, conazoles, dicarboximide), anilino-pyrimidines, and copper salts, and herbicides, including bipyridyl (paraquat, diquat), organophosphonates (glyphosate), chlorotriazine, and phenylurea, are commonly used in these areas.   The study highlights the increased risk of IBS in pesticide-heavy areas, particularly among women.

Common Herbicide Contributes to Development of Inflammatory Bowel Disease    (Beyond Pesticides, October 25, 2022) Inflammatory bowel disease (IBD) may be exacerbated by exposure to the herbicide propyzamide, used in both agriculture and on ornamental lawns and landscapes, according to research published in the journal Nature this month.  Recent data show that the number of people living with Crohn’s disease and ulcerative colitis, common types of IBD, have risen annually by 3.4% and 2.8% respectively, between just the years 2001 to 2018.   (S)cientists cross-referenced data from the U.S. Environmental Protection Agency’s ToxCast database to screen hundreds of different chemicals that had an affect on intestinal inflammation. Ultimately, 20 candidate chemicals were found, and scientists decided to focus on propyzamide due to its broad use patterns in food and in residential areas.   Using a mouse model, scientists found that propyzamide worsened an inflammatory process that had already been triggered by another exposure, but did not initiate the inflammation.    SNAP Comment: As of 4 Nov 2022, there are only 3 propyzamide herbicides registered with the PMRA. Historically there were 5. There are sstill 18 registered formulations in the US. There is only one commercial one, wht a registration expiring in 2026. It is used for control of weeds in alfalfa, trefoil, ornamentals, strawberries, apples, pears, lowbush blueberries, lettuce and established pastures.

Neurotoxic Pesticides Disrupt Gut Function Linked to Parkinson’s Disease Development  (Beyond Pesticides, May 26, 2022) 'A study published in The International Journal of Biochemistry & Cell Biology finds environmental exposure to neurotoxic pesticides increases Parkinson’s Disease (PD) risk through gastrointestinal (GI) disruption.  ...this study suggests environmental pesticide exposure disrupts GI cells responsible for supporting the autonomic nervous system. Enteric glial cells (EGCs) are GI cells that play a critical role in the functional changes that accompany GI dysfunction, as this dysfunction is one of the earliest symptoms indicating the onset of PD.  While only 10 to 15 percent of PD incidents are genetic, PD is quickly becoming the fastest-growing brain disease due to nongenetic factors...The pesticides implicated in the study include rotenone and tebufenpyrad. Both pesticides induce cell death via mitochondrial dysfunction among neurotransmitters that release, activate, or involve dopamine, also known as dopaminergic cell damage. ' SNAP Comment: There are currently 4 rotenone and 0 tebufenpyrad pesticides registeredby the PMRA.

Pilot Study Links Celiac Disease to Long-Lived Endocrine Disrupting Chemicals, like DDT, in the Environment   (Beyond Pesticides, May 13, 2020)  'Considering previous studies on the deleterious impact of POPs on the immune system, scientists analyzed blood samples from 30 children and young adults (3-21) who had been recently diagnosed with celiac disease. They compared results to 60 other young people of similar demographics. The research focused on three chemicals: PBDE, DDE, and PFAS.   Researchers found a statistically significant association between DDE and celiac disease after adjusting for confounding factors. Children and young adults with higher blood levels of DDE were two times as likely to be newly diagnosed with celiac. The study found sex-specific PFAS associations among females, and some specific associations among males.'

New survey in humans shows link between advanced liver disease and glyphosate (GM Watch, 23 April 2019)  'The new study advances previous research led by Dr Michael Antoniou at King's College London. Dr Antoniou's team found that rats fed the glyphosate-based herbicide Roundup at very low levels within regulatory safety limits developed NAFLD and NASH over a long-term period of two years...Prof Mills' study does not prove that glyphosate actually causes liver disease. It is an "after the fact" study in humans with liver disease, in which exposure to glyphosate herbicide was not controlled but glyphosate excretion was measured after the subjects became ill. However, it does show a correlation between high glyphosate levels in human urine and NASH.'

Rats fed GM stacked-trait maize developed leaky stomachs  (GM Watch, 09 July 2018)  The study lasted twice as long as industry studies ( 6 months) and the control rats were fed a non-gmo diet. 'Drs Zdziarski and Carman said, "Joining together all the adverse findings into a single severity score, we found that the rats on the GM diet had a score that was 33% higher than rats on the non-GM diet. The changes we saw are closest to those seen with chemical gastropathy (also called reactive gastritis), caused by chemical irritants, such as aspirin, damaging the lining of the stomach."'    also filed under gmos /safety

Glyphosate Implicated in Fatty Liver Disease (Beyond Pesticides, January 11, 2017) Ultra-low doses of glyphosate formulations fed to rats is linked to an increased likelihood of developing non-alcoholic fatty liver disease (NAFLD), according to a recently published study in the journal Nature.

Kidney, Liver Damage Linked to Chronic, Low-Dose Glyphosate Exposure (Beyond Pesticides, September 1, 2015) 'Levels of exposure tested in the recent study are far below what EPA sets as the maximum contaminate level (MCL) in drinking water throughout the U.S. While rats in the study were chronically exposed to .1 parts per billion Roundup concentrations, EPA allows 700 parts per billion. The agency notes that “some people who drink water containing glyphosate in excess of the MCL over many years could experience problems with their kidneys or reproductive disorders.” ' More on glyphosate.

Glyphosate, pathways to modern diseases II: Celiac sprue and gluten intolerance
www.motherearthnews.comReview article. Interdiscip Toxicol. 2013; Vol. 6(4): 159–184.
doi: 10.2478/intox-2013-0026

Amidst Criticism, New Study Reveals GE Crops Inflame Digestive Tract (Beyond Pesticides, June 14, 2013) 

Pesticide exposure damages nervous system, brain and digestive tract