Question:
Because high amounts of fluoride can be toxic, EPA places a cap, or maximum contaminant level, on fluoride concentrations in drinking water in order to prevent adverse health effects.

any comments?

Answer: Although the agency's current maximum contaminant level for fluoride in drinking water is 4 mg/L, a so-called secondary level of 2 mg/L was set by EPA to protect against cosmetic dental effects linked to excess fluoride consumption. According to the most recent data, about 1.4 million people have water with 2 mg/L of fluoride.

In 1993 the Research Council reviewed EPA's maximum contaminant level for fluoride and found it to be an appropriate interim standard until further research was completed. Now that several more studies have been done and because the Safe Drinking Water Act requires periodic reassessment of regulations, EPA asked for a new review.

Most exposure to fluoride in the United States results from consumption of water and water-based beverages, but dental products, food, and other sources contribute as well. Highly exposed subpopulations include individuals who have high concentrations of fluoride in their drinking water or who drink more water than the average person because of exercise, outdoor work, or a medical condition. Relative to their body weight, infants and young children are exposed to three to four times as much fluoride as adults. Children also may use more toothpaste than is advised or swallow it, and many receive fluoride treatments from their dentists. Fluoride accumulates in bone over time, so groups likely to have increased bone fluoride concentrations include the elderly and people with severe renal deficiency who have trouble excreting fluoride in their urine.