The monthly average fluoride concentration must fall between what ranges in mg/L?

The correct answer reflects the recommended range for fluoride concentration in drinking water as established by health and regulatory agencies. The range of 0.9 to 1.5 mg/L is significant because this level balances the benefits of fluoride in promoting dental health, particularly in reducing tooth decay, while minimizing the risk of dental fluorosis, which can occur with excessive fluoride exposure.

Fluoride is added to municipal water supplies to enhance dental health, but it is essential to maintain the concentration within a controlled range. Concentrations below 0.9 mg/L may not provide sufficient protection against cavities, while levels above 1.5 mg/L can pose health risks and the possibility of excessive fluoride leading to dental fluorosis. Hence, maintaining fluoride concentration within the specified range ensures that community health is prioritized while also adhering to public health guidelines.

This range reflects current public health standards, making it the appropriate answer for water operation certification.