Background Particulate matter (PM) < 2.5 mu m (PM2.5) or fine PM is a serious public health concern. It affects DNA methylation and heightens carcinogenesis. Deleted in lung and esophageal cancer 1 (DLEC1) is a tumor suppressor gene. However, aberrant methylation of the gene is associated with several cancers. We evaluated the association between PM2.5 and DLEC1 promoter methylation in Taiwanese adults based on regular outdoor exercise. Methods We obtained DNA methylation and exercise data of 496 participants (aged between 30 and 70 years) from the Taiwan Biobank (TWB) database. We also extracted PM2.5 data from the Air Quality Monitoring Database (AQMD) and estimated participants' exposure using residential addresses. Results DLEC1 methylation and PM2.5 were positively associated: beta coefficient (beta) = 0.114 x 10(-3); p value = 0.046. The test for interaction between exercise and PM2.5 on DLEC1 methylation was significant (p value = 0.036). After stratification by exercise habits, PM2.5 and DLEC1 methylation remained significantly associated only among those who exercised regularly (beta = 0.237 x 10(-3); p value = 0.007). PM2.5 quartile-stratified analyses revealed an inverse association between regular exercise and DLEC1 methylation at PM2.5 < 27.37 mu g/m(3) (beta = - 5.280 x 10(-3); p value = 0.009). After combining exercise habits and PM2.5 quartiles, one stratum (i.e., regular exercise and PM2.5 < 27.37 mu g/m(3)) was inversely associated with DLEC1 methylation (beta = -5.160 x 10(-3), p value = 0.007). Conclusions We found significant positive associations between PM2.5 and DLEC1 promoter methylation. Regular exercise at PM2.5 < 27.37 mu g/m(3) seemingly regulated DLEC1 promoter methylation.
