THE ASSOCIATION BETWEEN HOUSEHOLD PROXIMITY TO GLYPHOSATE-SPRAYED CROPS AND THE GUT MICROBIOME COMPOSITION OF FARMING FAMILIES

Abstract

Background: Glyphosate-based herbicides are the most extensively used weed control agents globally, with growing concerns regarding their environmental and health effects. Although considered safe for humans, glyphosate can influence microorganisms that share the shikimate pathway, including gut bacteria. Chronic exposure through environmental routes may alter the human gut microbiome, an essential regulator of immunity and metabolism.

Objective: To investigate whether environmental exposure to glyphosate, determined by household proximity to sprayed agricultural fields, correlates with specific alterations in gut microbiome composition among farming families in South Punjab.

Methods: This cross-sectional analytical study was carried out over a four-month period with a cohort of 60 adults. Participants were divided into two groups: an exposed group comprising 30 individuals residing within 500 meters of agricultural fields where glyphosate was applied, and a control group of 30 individuals living more than two kilometers from such areas. Concentrations of glyphosate and its metabolite, aminomethylphosphonic acid (AMPA), were measured in serum samples via high-performance liquid chromatography. To assess gut microbial profiles, fecal samples were subjected to 16S rRNA gene sequencing utilizing the Illumina MiSeq platform, enabling evaluation of microbial diversity and taxonomic structure. Statistical analysis was performed with SPSS software (version 26.0); independent samples t-tests and Pearson correlation coefficients were used for data conforming to a normal distribution.

Results: The exposed group exhibited significantly higher serum glyphosate (2.87 ± 0.64 µg/L) and AMPA (0.79 ± 0.25 µg/L) levels compared to controls (0.93 ± 0.41 µg/L and 0.28 ± 0.11 µg/L, respectively; p < 0.001). Alpha diversity indices were lower among exposed participants (Shannon: 3.42 ± 0.51; Simpson: 0.81 ± 0.07) than controls (Shannon: 3.96 ± 0.48; Simpson: 0.88 ± 0.05). Firmicutes abundance was reduced, while Bacteroidetes and Proteobacteria were elevated. A significant negative correlation was found between glyphosate levels and microbial diversity (r = –0.58, p < 0.01).

Conclusion: Environmental glyphosate exposure was associated with decreased gut microbial diversity and compositional imbalance among farming families. These findings highlight potential health implications of chronic low-level herbicide exposure and underscore the need for sustainable agricultural practices and further human-based microbiome research.