To further understand how the rs699780 (NOTCH2) modified the concentration-response relationship between arsenic exposure and T2DM, we examined the nonlinear arsenic effects using polynomial regression with 3 degrees of freedom and stratified data into the two allele groups (TT vs. CT/CC) for rs699780 (NOTCH2), where C alleles were characterized as the minor allele and T alleles were characterized as the major allele in this population. This evidence concerns the gene NOTCH2 and type 2 diabetes mellitus.