Inorganic arsenic (iAs) and fluoride (F−) are naturally occurring drinking water contaminants. However, co-exposure to these contaminants and its effects on human health are understudied. The goal of this study was examined exposures to iAs and F− in Chihuahua, Mexico, where exposure to iAs in drinking water has been associated with adverse health effects. All 1119 eligible Chihuahua residents (>18 years) provided a sample of drinking water and spot urine samples. iAs and F− concentrations in water samples ranged from 0.1 to 419.8 µg As/L and from 0.05 to 11.8 mg F−/L. Urinary arsenic (U-tAs) and urinary F− (U-F−) levels ranged from 0.5 to 467.9 ng As/mL and from 0.1 to 14.4 µg F−/mL. A strong positive correlation was found between iAs and F− concentrations in drinking water (rs = 0.741). Similarly, U-tAs levels correlated positively with U-F− concentrations (rs = 0.633). These results show that Chihuahua residents exposed to high iAs concentrations in drinking water are also exposed to high levels of F−, raising questions about possible contribution of F− exposure to the adverse effects that have so far been attributed only to iAs exposure. Thus, investigation of possible interactions between iAs and F− exposures and its related health risks deserves immediate attention
