Arsenic methylation, GSTO1 polymorphisms, and metabolic syndrome in an arseniasis endemic area of southwestern Taiwan

► MetS in relation to arsenic methylation was examined in a cohort with previous high exposure. ► Subjects with MetS experienced higher inorganic arsenic ingestion. ► Decreasing MMA ratio was associated with an increased risk for MetS. ► The increased risk for MetS was further modified by the GSTO1 A140D genotype.