Long-term exposure to inorganic
arsenic from artesian drinking well water is associated with
carotid atherosclerosis in the Blackfoot Disease (BFD)-hyperendemic area in Taiwan. The current study examined the
arsenic methylation capacity and its risk on
carotid atherosclerosis. A total of 304 adults (158 men and 146 women) residing in the BFD-hyperendemic area were included. The extent of
carotid atherosclerosis was assessed by duplex ultrasonography. Chronic
arsenic exposure was estimated by an index of cumulative
arsenic exposure (CAE) and the duration of artesian well water consumption. Urinary levels of inorganic
arsenite [As(III)],
arsenate [As(V)],
monomethylarsonic acid [MMA(V)] and
dimethylarsinic acid [DMA(V)] were determined by high performance liquid chromatography linked on-line to a hydride generator and atomic absorption spectrometry (HPLC-HG-AAS). The percentage of
arsenic species, primary methylation index [PMI=MMA(V)/(As(III)+As(V)] and secondary methylation index [SMI=DMA(V)/MMA(V)] were calculated and employed as indicators of
arsenic methylation capacity. Results showed that women and younger subjects had a more efficient
arsenic methylation capacity than did men and the elderly.
Carotid atherosclerosis cases had a significantly greater percentage of MMA(V) [%MMA(V)] and a lower percentage of DMA [%DMA (V)] compared to controls. Subjects in the highest two tertiles of PMI with a median of CAE >0 mg/L-year had an odds ratio (OR) and a 95% confidence interval (CI) of
carotid atherosclerosis of 2.61 and 0.98-6.90 compared to those in the highest two tertiles of PMI with a CAE=0 mg/L-year. We conclude that individuals with greater exposure to
arsenic and lower capacity to methylate inorganic
arsenic may be at a higher risk to
carotid atherosclerosis.