Exposure definition determines observed associations between municipal solid waste landfill proximity and chronic disease prevalence in the southeastern United States

Systematic reviews have concluded that evidence for chronic health effects among adults living near municipal solid waste landfills is inadequate, and that reported respiratory associations have not been replicated. Cross-sectional ecological analysis of 15,605 census tracts across ten southeastern states. Exposure was the proportion of tract area within dissolved buffer radii of 0.8, 1.6, 4.8, and 8.0 km around 622 landfills, with alternative definitions using a 10% areal threshold and centroid distance bands. Outcomes were CDC PLACES prevalence estimates for asthma, hypertension, cancer, poor mental health, and diabetes. Linear models with robust standard errors were fitted under three covariate specifications and a spatial error specification. Estimates are percentage point differences per 10% point increase in tract area within the buffer. Asthma prevalence was not associated with proximity at any distance under any specification (partially adjusted, 0.8 km: 0.009, 95% CI − 0.073 to 0.092). Asthma estimates reversed direction across covariate specifications, from 0.049 (0.002 to 0.097) unadjusted at 1.6 km to − 0.009 (− 0.013 to − 0.006) fully adjusted at 8.0 km. Inverse associations for hypertension, poor mental health, and diabetes at longer distances did not persist under spatial error models. Exposure correlated weakly with the CDC Environmental Justice Index environmental burden ranking (Spearman rho 0.115), and 34.5% of exposed tracts fell in its two lowest burden quintiles. Landfill proximity was not associated with chronic disease prevalence in this region. Estimates depended on covariate specification and exposure definition. Municipal solid waste landfills are absent from the Environmental Justice Index.