This study evaluates the effect of water source change on heavy metal concentrations in water, paddy soil, and
rice, as well as the health risks to residents of three riverine communities in South China. The results show
that after substituting the sources of drinking water, heavy metal levels (except for Pb at Tangjun) in drinking
water were below WHO guideline values and the potential risk from drinking water may be negligible. The
As (46.2–66.8%), Pb (65.7–82.6%), Cd (50.8–55.0%), and Hg (28.3–32.6%) concentrations in paddy soils in
Sanhe and Lasha significantly (p b 0.05) decreased with a change of irrigation water sources compared
to Tangjun, without change of irrigation water source. Similarly, the Cd (39.1–81.3%) and Hg (60.0–75.0%)
concentrations in rice grown at Sanhe and Lasha significantly (p b 0.05) decreased compared to those at Tangjun.
Consequently, replacing irrigation water source significantly (p b 0.05) reduced the hazard quotient (HQ)
and cancer risk for the corresponding single metal via soil ingestion and rice consumption. Despite that total
non-carcinogenic and carcinogenic risks at Sanhe and Lasha were significantly decreased, they still exceeded
the maximum acceptable limits recommended by US EPA, in