For example, a case–control study conducted in China reported positive correlations between PAH levels in maternal serum and methylation levels of tight junction pathway genes CTNNA1 and MYH2 in neural tissue from NTD cases [11], while LINE-1 and MGMT genes were found to be hypomethylated in 82 PAH-exposed coke-oven workers compared to 62 unexposed controls, and gene-specific methylation of LINE-1 and MGMT was inversely correlated with levels of urinary PAH metabolites [31]. Here, MGMT is linked to neural tube defect.