Ian Byrell Stanaway

Project title: Longitudinal Analysis of Genetic and Environmental Data from an Agricultural Cohort Living in Yakima Valley Reveals an Agricultural Exposome

Degree: PhD | Program: Environmental Toxicology (Tox) | Project type: Thesis/Dissertation
Completed in: 2016 | Faculty advisor: Elaine M. Faustman


In an agricultural community cohort, we investigated agricultural pesticide exposure associated changes in the oral buccal microbiota. We found a seasonally persistent association between blood detection of the insecticide Azinphos-methyl and the taxonomic composition of the buccal swab oral microbiome. Blood and buccal samples were collected concurrently from individual subjects across two seasons, spring-summer 2005 and winter 2006. Mass spectrometry quantified blood concentrations of the organophosphate insecticide Azinphos-methyl. Buccal microbiome samples were 16S rRNA gene DNA sequenced and assigned to the bacterial taxonomy. Non-parametric analysis of the transformed microbiome data for individuals with and without Azinphos-methyl blood detection showed significant perturbations in seven common bacterial genera (>0.5% of sample mean read depth), including significant reductions in the common oral bacteria, Streptococcus. Diversity in composition between individuals’ microbiomes was also investigated using principal components analysis to reveal two primary clusters of microbiome types. The spring-summer ‘exposed’ cluster with significantly less bacterial diversity was enriched for farmworkers and contained 27 of the 30 adult individuals who also had Azinphos-methyl agricultural pesticide exposure detected in the blood. The children of each adult nearly always clustered with their respective household adult. Additionally, we investigated the additive effects of genetic minor allele variants in the Azinphos-methyl pesticide target blood cholinesterase enzymes. There is a significant additive relationship in the regression framework with environmental and genetic associations to these blood cholinesterase enzymes activities.