In a water distribution system with different sources, water blending occurs, causing specific variations of the
arsenic level. This study was undertaken to investigate the concentration and
cancer risk of
arsenic in blended water in Xi'an city. A total of 672 tap water samples were collected from eight sampling points in the blending zones for
arsenic determination. The risk was evaluated through oral ingestion and dermal absorption, separately for males and females, as well as with respect to seasons and blending zones. Although the
arsenic concentrations always fulfilled the requirements of the World Health Organization (WHO) (≤10 μg L-1), the total
cancer risk value was higher than the general guidance risk value of 1.00 × 10-6. In the blending zone of the Qujiang and No.3 WTPs (Z2), the total
cancer risk value was over 1.00 × 10-5, indicating that public health would be affected to some extent. More than 99% of the total
cancer risk was from oral ingestion, and dermal absorption had a little contribution. With higher exposure duration and lower
body weight, women had a higher
cancer risk. In addition, due to several influential factors, the total
cancer risk in the four blending zones reached the maximum in different seasons. The sensitivity analysis by the tornado chart proved that
body weight,
arsenic concentration and ingestion rate significantly contributed to
cancer risk. This study suggests the regular monitoring of water blending zones for improving risk management.