Millions of pounds of pesticides are used each year in the US: on farms, in buildings and homes, on lawns, in pet flea and tick products - basically everywhere. And so the pesticides eventually wind up in us - from the foods we eat, the water we drink, the air we breathe (when pesticides drift during applications or when used indoors), and the treated lawns and ground we walk on.
We are continuously exposed to low levels of multiple pesticides, but it is unknown what this does to us. Recently, a study examined the effect of multiple pesticide exposures on gut health and found that they killed off many beneficial (good) bacteria and had harmful alterations on gut bacteria metabolism. Uh-oh.
Bottom line: Many studies show that we can quickly (within 2 weeks) reduce the amount of pesticides (pesticide residues) in our bodies by eating as many organic foods as possible. Also, use nontoxic IPM (Integrated Pest Management) in the home, and reduce pesticide use in and out of the home (on lawns and gardens).
From Beyond Pesticides: Study Maps the Gut Microbiome and Adverse Impacts of Pesticide Residues
Researchers developed a novel tool* in a recent study published in Nature Communications this year that successfully creates a map of the “pesticide-gut microbiota-metabolite network,” identifying “significant alterations in gut bacteria metabolism.”
While the study authors acknowledge that this is not a complete map, since they selected specific pesticides and bacterial partners, the research adds to the body of peer-reviewed scientific literature that underscores the relationship between pesticide residues and human gut health. Organic farmers, as well as any land steward invested in agroecological practices and soil health, understand that microbial life (both in the body and in the soil) is dangerously undermined by the status quo of chemical-intensive land management.
Background and Methodology
The researchers leverage mass spectrometry to test metabolite (metabolomics) and lipid (lipidomics) relationships with pesticide residues, as well as an in vivo mouse model.
All major phylogenetic (“evolutionary relationships among biological entities”) groups are represented in the bacterial strains studied: 7 Bacteroidetes, 7 Firmicutes, 2 Actinobacteria, and 1 Proteobacteria. There were 18 pesticide compounds (active ingredients and metabolites) tested in relation to the above bacterial strains, including organochlorines (endosulfan, methoxychlor, and DDT metabolites 4,4’-DDT, 4,4’-DDE, 4,4’-DDD); organophosphates (chlorpyrifos, chlorpyrifos metabolite TCP [3,5,6-Trichloro-2-pyridinol], dichlorvos, malathion, fenitrothion, parathion, diazinon); pyrethroids (permethrin and cypermethrin); carbamates (carbaryl), glyphosate, and malathion dicarboxylic acid (metabolite of malathion).
Results: Key findings identified by the researchers who conducted this study include:
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- 306 pesticide-bacteria pairs showing significant potential metabolic shifts in the gut microbiome.
- 40 metabolic pathways are disrupted; more specifically, pathways involving nucleotide synthesis, amino acid metabolism, and tryptophan, propanoate, and bile acid pathways. This is critical to understanding of public health, as nucleotides are considered one of the building blocks of RNA and DNA (National Human Genome Research Institute), amino acids are important energy sources for the human body (Nature), tryptophan and propanoate serve essential functions for metabolic regulation (Endocrinology) and bile acid is critical for disposal of toxic metabolites and absorption of lipid-soluble vitamins and essential dietary fats. (ScienceDirect).
This in vivo mouse study also validated these metabolic changes based on the bacterial-pesticide relationship. For example, mice in this study that were recolonized with B. ovatus and exposed to 4,4′-DDE exhibited:
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- Systemic metabolic changes identified in the brain, liver, intestine, and lung, among other organs.
- Altered levels of lipids, purines (building block of DNA and RNA), N-acylethanolamine (NAEs), short-chain fatty acids (SCFAs), and bile acids (BAs).
- Suppression of TLR4/NF-κB inflammatory signaling, indicating microbial modulation of host immunity.
- Measurable pesticide residues in tissues, including the brain and gut.
Previous Research
There has been mounting scientific evidence in recent years that identifies various exposure pathways of concern that may be contributing to poorer health outcomes for the gut microbiome, as documented in previous Daily News reports, and the Pesticide-Induced Disease Database.
University of Illinois researchers in 2020 published a literature review in Toxicological Sciences looking at how various environmental contaminants adversely affect and reinforce chemical disruption of the gut microbiome. The review details manufacturing compounds in commonly-purchased consumer products, like bisphenols (BPA) and phthalates in plastic packaging and vinyl flooring. The review also examines the science behind the exposure to numerous persistent organic pollutants (POPs) like pesticides, polychlorinated biphenyl (PCBs), perfluorochemicals (PFCs) in non-stick cookware, polybrominated diphenyl ethers (flame retardants), and dioxins (byproducts of pesticide manufacturing and burning organic material like fossil fuels). The research highlighted in this review looks at the adverse impacts of these chemicals in rodents (e.g., rats, mice), aquatic organisms (e.g., fish, amphibians), birds (e.g., chickens), larger mammals (e.g., dogs, cows, human adults, and infants), insects (e.g., honey bees), and other organisms. (See Daily News here.)
In 2022, a robust report published in Environmental Health and developed in partnership with researchers at King’s College London, the Center for Microbiome Analyses and Therapeutics (Netherlands), the Metabolomic Medicine Clinic (Greece), and the University Hospital of Limoges (France) identified over 300 environmental contaminants in collected fecal and urine samples. The report examined dietary exposure to 186 common pesticide residues in the fecal excrement to determine impacts on the microbiome among 65 twins in the United Kingdom and investigated if associations between gut health and various variables can also impact concentrations of pesticide residues in excrement to indicate gut health alterations.
In terms of pesticide residues, the report finds that all urine samples contain pyrethroid or organophosphate insecticide residues, with 53 percent of urine samples containing glyphosate. Additionally, participants 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. (See Daily News here.)
Specific pesticides and classes of pesticide active ingredients, such as glyphosate, neonicotinoids, azoxystrobin, among others, have been linked to adverse human gut health impacts. Researchers based at the University of Turku (Finland) developed a bioinformatics tool in 2021 to determine that “54% of species in the core human gut microbiome are sensitive to glyphosate.” (See Daily News here.)