DNA methylation of CpG sites overlapping with Alu and LINE1 repetitive elements was associated with diesel exhaust. A) Distributions of unadjusted p-values from LME modeling applied to CpG sites overlapping with Alu and LINE1 elements. The uniform distribution expected by chance is indicated with horizontal dashed lines. Positive skewing of DE p-value distributions indicated association with differential methylation, whereas lack of skewing of FA p-value distributions indicated absence of association. B) Distributions of ∆β obtained from subtracting pre-FA beta values from post-FA beta values, and from subtracting pre-DE beta values from post- DE beta values for LINE1 and Alu probes that were significantly altered in response to DE exposure. ∆β from DE samples were much larger in magnitude than that from FA samples.