Teeth are likely to become pitted when fluoride concentrations in drinking water exceed which level?

Fluoride is commonly added to drinking water to help reduce the incidence of dental cavities. However, excessive exposure to fluoride can lead to dental fluorosis, characterized by changes in the appearance of teeth, including the formation of pits or discoloration. Research indicates that dental fluorosis typically begins to occur when fluoride concentrations in drinking water exceed 4 mg/l.

This threshold has been established based on studies correlating fluoride intake during the critical periods of tooth development with the risk of developing fluorosis. At this level, while some benefits for dental health are maintained, the risk of cosmetic changes to teeth increases, notably pitting and other surface irregularities, as fluoride becomes more prevalent in the enamel matrix.

Therefore, the answer indicating that teeth are likely to become pitted when fluoride concentrations in drinking water exceed 4 mg/l is supported by scientific findings regarding fluoride exposure and dental health.