The findings suggested that four SNPs (rs2049046, rs662, rs3811647, and rs1042838) functionally related to the Brain-Derived Neurotrophic Factor (BDNF), Paraoxonase 1 (PON1), Transferrin (TF) and Progesterone Receptor (PGR) genes appeared to modify the methylmercury-outcome associations with cognitive deficits in children with the minor alleles (mutations). The gene discussed is PON1; the disease is Cognitive impairment.