Which statement about fluoride requirements for children is incorrect?

The statement regarding the fluoride requirements for a 6-year-old child is incorrect because, based on established guidelines, a child needs an adequate amount of fluoride to support dental health, yet the amount required is contingent on the levels of fluoride present in the drinking water.

For a 6-year-old, the recommended daily fluoride intake from all sources, including diet and water, generally should not exceed 1mg per day, especially when considering the amount already provided in the water supply. If a water supply contains a fluoride concentration of 0.5mg per liter, this would not meet the child's fluoride needs because they would only obtain a small fraction of the recommended daily intake from that source. Therefore, stating that a child requires an additional 1mg while already getting 0.5mg from the water supply is misleading, as they would effectively receive only 0.5mg from the water, implying a need for additional fluoride supplementation to reach the recommendation.

In contrast, the other statements reflect correct fluoride needs based on various drinking water concentrations, where the specified fluoride amounts align appropriately with dietary intake or existing water fluoride levels.