Bentazone in water and human urine in Wuhan, central China: exposure assessment

Bentazone is a widely used post-emergence herbicide, while no data was available on its concentrations in tap water from China and in urine among the general population. It was determined in the source (Wuhan section of the Yangtze River watershed), treated, and tap water (n = 20, 20, and 170, respectively) in different seasons (2019) in Wuhan, central China. Also, urine samples (n = 38) collected from healthy adults in Wuhan (September 2020) were analyzed to characterize its urinary concentration. Bentazone was detected in all the source and treated water samples. Its concentrations in the source water in July were higher than those in February (median: 17.9 ng/L vs. 2.86 ng/L) (p < 0.05). It cannot be removed efficiently (27.8-27.9%) by conventional drinking water treatment using NaClO, but it can be efficiently removed by using chlorine dioxide or ozone combined with activated carbon. Bentazone was frequently detected (detection frequency: 96.3%) in 160 tap water samples (underwent conventional treatment) (median: 1.95 ng/L, range: <0.02-47.0 ng/L), while it was not detectable in tap water samples that underwent ozone combined with activated carbon. Seasonal variations were found, with the lowest median concentration (ng/L) in April (0.46) and the highest in July (17.6). In addition, bentazone was frequently (92.1%) detected in human urine samples (median: 0.02 ng/mL; range: < 0.01-0.11 ng/mL). The estimated daily intake of bentazone based on its median concentration in tap water (0.04 ng/kg-body weight [bw]/day) accounted for approximately 8% of that based on the median urinary concentration (0.48 ng/kg-bw/day). This is the first time to characterize its occurrence in drinking water from China and its occurrence in the urine of the general population.