County-level spatial and age-specific associations between glyphosate application and non-Hodgkin lymphoma incidence in Nebraska

Glyphosate is widely used in agricultural regions of the United States, including Nebraska. Although previous epidemiological studies have examined potential associations between glyphosate exposure and non-Hodgkin lymphoma (NHL), county-level geographic and age-specific patterns in Nebraska remain insufficiently characterized. This ecological study examined county-level glyphosate application and NHL incidence across 93 Nebraska counties using United States Geological Survey application estimates and Nebraska State Cancer Registry data. Descriptive NHL trends were evaluated for 1987–2014, while exposure–outcome analyses were restricted to 1992–2014. Geographic distributions were examined using choropleth and descriptive bivariate maps. Pearson and Spearman correlations and county-level regression analyses were used to evaluate overall and age-specific associations, including exploratory rural–urban comparisons. Glyphosate application increased substantially during the study period, and geographic variation in both glyphosate application and NHL incidence was observed across Nebraska. Weak positive correlations were identified among rural counties for individuals aged 50–59 years (Pearson's r = 0.244, p = 0.0273) and 60–69 years ( r = 0.256, p = 0.0203) in unadjusted analyses. There was no statistically significant association between mean annual glyphosate application and overall age-adjusted NHL incidence ( p = 0.613). Additional sensitivity analyses indicated that selected age-specific associations were sensitive to analytical specifications and were not consistently supported across exposure lag periods. These findings are exploratory and do not establish individual-level exposure–disease relationships or causality. Further investigations should incorporate individual exposure assessment, occupational histories, agricultural co-exposures, and appropriate latency periods.