## **Core Concept**
The question revolves around the relationship between community water fluoridation levels and plasma fluoride levels in healthy individuals. Fluoride levels in drinking water are measured in parts per million (ppm), and there is a known correlation between water fluoride levels and plasma fluoride concentrations.

## **Why the Correct Answer is Right**
In a community with a water fluoride level of 1 ppm, the expected plasma fluoride level in a healthy, fasting individual is approximately 0.2 μmol/L (or 4 ppb). This relationship is based on the concept that the body maintains a relatively constant level of fluoride in the plasma, which is influenced by the amount of fluoride ingested from water and other sources. A fluoride level of 1 ppm in drinking water is considered optimal for dental health and corresponds to a plasma fluoride concentration of about 0.2 μmol/L.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option suggests a plasma fluoride level that is too low for a community with 1 ppm fluoride in the water. Without a specific value, we can't directly assess, but we know 0.2 μmol/L is the expected value.
- **Option B:** Similarly, this option is incorrect because it does not align with the expected plasma fluoride level for a 1 ppm community water fluoridation level.
- **Option D:** This option suggests a much higher plasma fluoride level than expected for a community with 1 ppm fluoride in the water, indicating it is not the correct answer.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that optimal community water fluoridation levels are generally considered to be around 0.7 to 1.2 ppm, with 1 ppm being a commonly targeted level. This level helps in preventing dental caries while minimizing the risk of dental fluorosis.

## **Correct Answer:** .