There was a significant association between T1D/IS and several POPs including p, p’-DDE, trans-nonachlor and PCB-153. PCB-153 and p, p’-DDE reduce insulin production and secretion in β-cells. Interestingly, PCB-153 but not p, p’-DDE, reduced the expression level of Slc2a2 and Gck. PCB-153 and p, p’-DDE alter mRNA expression of genes involved in glucose-stimulated insulin secretion. The gene discussed is GCK; the disease is type 1 diabetes mellitus.