The Association Between Arsenic Metabolism and Hypertension Among Population with Varying Arsenic Exposure Levels in China

High-level arsenic exposure is widely considered to be associated with hypertension. However, the relationship between arsenic metabolism and hypertension under high-level exposure remains controversial. In addition, the evidence at low-to-moderate levels remains unelucidated. This research aims to evaluate the relationship between arsenic metabolism and the risk of hypertension in a Chinese population under different levels of arsenic exposure. A cross-sectional survey of 1932 participants exposed to different arsenic concentrations through contaminated drinking water was conducted in epidemic areas in southwest and northwest China. Based on the World Health Organization’s drinking-water standards, the study population was stratified into two subgroups: high-exposure (water As concentration (wAs) ≥ 50 μg/L) and low-to-moderate (10 ≤ wAs < 50 μg/L) exposure. Arsenic metabolism capacity was evaluated by the relative fractions of inorganic arsenic (iAs), monomethylarsenate (MMA) and dimethylarsenate (DMA) in urine (denoted by iAs%, MMA%, DMA%, primary methylation index and the secondary methylation index). The relationship between arsenic metabolism and hypertension was evaluated by the leave-one-out approach, which modeled the dynamics of arsenic metabolism. There were significant differences and associations between individual factors and the distribution of urinary arsenic metabolites at different arsenic exposure levels. Increased MMA% was associated with higher risk of hypertension when either iAs% or DMA% decreased at different arsenic exposures. iAs% was associated with lower risk of hypertension only when MMA% decreased in both subgroups. In addition, higher DMA% was both associated with lower hypertension prevalence when either iAs% or MMA% decreased only at low-to-moderate arsenic exposure. In summary, arsenic metabolism, particularly higher MMA%, was associated with increased risk of hypertension in the Chinese arsenic-exposed population with both high and low-to-moderate levels, which provides additional evidence for the assessment of arsenic-induced hypertension incident.