Beyoond which minimum concentration of F water becomes useless for drinking purpose

Options

A. 10 ppm
B. 5 ppm
C. 2 ppm
D. 20 ppm

Answer

To determine the minimum concentration of fluoride ions (F-) in water beyond which it becomes unsuitable for drinking purposes, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Fluoride Ion Importance**:
- Fluoride ions are essential in small amounts for dental health. They help in the formation of hydroxyapatite, which strengthens tooth enamel.

2. **Optimal Concentration**:
- The optimal concentration of fluoride ions in drinking water is around 1 ppm (parts per million). This concentration helps in preventing tooth decay.

3. **Threshold for Safety**:
- While 1 ppm is beneficial, concentrations above this can lead to dental issues. Specifically, concentrations above 2 ppm can cause dental fluorosis, which is characterized by mottling or discoloration of teeth.

4. **Harmful Effects of High Concentration**:
- If the fluoride concentration exceeds 10 ppm, it can lead to more severe health issues, including skeletal fluorosis, which affects bones and joints.

5. **Conclusion**:
- Therefore, the minimum concentration of fluoride ions in water beyond which it becomes unsuitable for drinking purposes is 2 ppm.

### Final Answer:
The minimum concentration of fluoride ions in water beyond which it becomes useless for drinking purposes is **2 ppm**.

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