Effect of altitude on urinary, plasma and nail fluoride levels in children and adults in Nepal.

•Several aspects of fluoride metabolism were examined in child-parent dyads living at a lower- and higher-altitudes in Nepal.•Fluoride concentration of finger- and toe-nail was not related to either fluoride intake or altitude.•In children, higher altitude leads to decreased urinary fluoride excretion when given the same fluoride dose.•In parents, altitude has no significant impact on the proportion of fluoride intake excreted in urine.•Higher altitude results in higher plasma fluoride concentration in parents when exposed to the same amount of fluoride.