County-Level Ecological Association Between Glyphosate Exposure and Chronic Disease Mortality in Midwestern US Agricultural Communities

Background: Glyphosate is widely used in the United States (US) agriculture, particularly in regions with intensive crop production. Concerns have been raised regarding potential long-term health effects associated with environmental exposure. Chronic diseases remain a leading cause of mortality in the US, particularly in agricultural and rural communities. Objective: To examine the ecological association between county-level glyphosate use and chronic disease mortality in Midwestern US agricultural communities. Methods: This ecological panel study used county-level mortality data from the Centers for Disease Control and Prevention (CDC) Wide-ranging Online Data for Epidemiologic Research (WONDER) Multiple Cause of Death files and pesticide use estimates from the United States Geological Survey Pesticide National Synthesis Project. The study included counties across 12 Midwestern states from 1999 to 2020. Age-adjusted mortality rates for cancer, heart disease, diabetes, Alzheimer's disease, kidney disease, and chronic respiratory disease were analyzed. The primary exposure was log-transformed glyphosate use scaled per 1,000 kg and lagged by three years. County and year fixed effects regression models were applied. Results: Higher three-year lagged glyphosate use was significantly associated with increased heart disease mortality at the county level (β = 5.04; p < 0.001), indicating that increases in glyphosate exposure were associated with modest increases in county-level heart disease mortality rates. No significant associations were observed for the other chronic disease outcomes. Conclusion: This study highlights a population-level association between glyphosate use and heart disease mortality in Midwestern counties. Continued monitoring and research using individual-level data are warranted.