Microbiota Changes

also see digestive tract, soils

Weed Killer Use Destroys Soil Life and Ecosystems, Paper Finds   (Beyond Pesticides, November 11, 2022) 'A paper published in Trends in Ecology & Evolution in late October sounds an unnerving alarm about the globally ubiquitous use of herbicides and the ecological destruction being caused. It asserts that widespread environmental contamination with these herbicide compounds is influencing soil, plant, and animal microbiomes in ways that are not only not well understood, but also, can have significant impacts on the functioning of organisms and their ecosystems — with evolutionary implications. '   'The study authors also note that adjuvant, “inert” ingredients in herbicide formulations can sometimes be even more toxic to non-target organisms than the active ingredients themselves,' In the US, these are untested for that effect and also secret. They are also secret in Canada but I am unsure if they have been tested for effects on non-target organisms. Likely not.   'The study identifies classes or modes of action for a host of herbicide active ingredients, including whether they act directly or indirectly on microbiota, and their respective effects on soil, plant, or animal microbiomes. Among the modes (and sample compounds) that have direct impacts on microbes are:

• ACC (acetyl-CoA carboxylase) inhibitors (e.g., diclofop-methyl, haloxyfop)
• ALS (acetolactate synthase) inhibitors (sulfonylureas, triazolopyrimidines)
• EPSPS (5-enolpyruvylshikimate-3-phosphate synthase) inhibitors in the shikimate pathway (glyphosate)
• glutamine synthetase inhibitors (glufosinate)The mechanisms that exhibit indirect impacts, including on cellular metabolism and hormone synthesis, are auxin-like herbicides (2,4-D, dicamba); photosystem (related to photosynthesis) inhibitors (triazines, paraquat, diphenyl ether); and gibberellin (plant hormone that stimulates stem elongation, germination, and flowering) inhibitors (acetochlor, metolachlor, pendimethalin).
• The indirect impacts on microbiota include those that degrade bacterial diversity, erode microbial community structure, and disable nitrogen-fixing bacteria.'

Glyphosate study shows adverse health effects at "safe" dose  (GM Watch, 16 May 2018) 'The study was focused on the newborn, infancy and adolescence phases of life. The results reveal that glyphosate-based herbicide (GBH) was able to alter certain important biological parameters, mainly relating to sexual development, genotoxicity, and the intestinal microbiome....The effects occurred at a dose deemed safe by regulators to ingest on a daily basis over a long-term period. In human-equivalent terms the dosing period corresponded to the period from the embryo stage to 18 years of age.' The levels measured in urine suggest 'a bioaccumulation effect of glyphosate that was proportional to the length of treatment.'      more on glyphosate at fact sheets/ glyphosate

Study finds link between pesticide exposure and microbiome changes (UPI, By Brooks Hays. Nov. 11, 2016)  The oral microbiome of farmworkers are markedly different than other humans, and pesticide exposure explains why, new research shows. Adults with concentrations of organophosphate pesticide, Azinphos-methyl, in their blood had a significantly altered oral microbiome. "We found significantly reduced abundances of seven common taxa of oral bacteria, including Streptococcus, one of the most common normal microbiota in the mouth," researcher Ian B. Stanaway said in a news release. Researchers also found a correlation between pesticide exposure and shifts in the abundance and diversity of several other strains and species of bacteria, including microbes belonging to genera Streptococcus and Halomonas. Additionally, scientists measured shifts in bacterial diversity related to changing levels of exposure during the seasons. "The challenge becomes, what does this mean," said researcher Elaine M. Faustman. "We don’t know, but we depend on the micriobiome for many metabolic processes." link to study. SNAP Comment: This is the first study I know of that has looked at this issue. Although it specifically studies the organophosphate Azinphos-methyl, I would not be surprised that the link also exists with other pesticides. Time will tell. According to PMRA label search (15 Nov 2016), Azinphos-methyl is no longer sold in Canada. I did not check every historical label but the last sale I could find was in 2010. It could still be used by those with a stockpile.