Risk assessment by seasonal variation of well water fluoride in Japan

This study clarified the existence of seasonal variations of Fluoride concentrations in multiple wells with different depths, and determined the appropriate time to assess chronic Fluoride toxicity considering these variations. There was up to 3.6 times more seasonal variation in F concentration at the same point. The mean F ion concentration was the lowest at 0.0766 ± 0.0197 mg/L in March, and highest at 0.2412 ± 0.0345 mg/L in December. The hazard quotients (HQ) were all < 1 at all points, and the risk of chronic Fluoride toxicity in children was low. It is necessary to carry out multiple measurements, including in periods with low rainfall, due to seasonal variations.