High concentration of fluoride is poisonous and harmful to bones and teeth at levels over

Options

A. 1 ppm
B. 3 ppm
C. 5 ppm
D. 10 ppm

Answer

**Step-by-Step Solution:**

1. **Understanding Fluoride Concentration**: Fluoride is an essential element that can help prevent tooth decay when present in optimal concentrations. However, excessive fluoride can lead to health issues.

2. **Safe Levels of Fluoride**: The safe concentration of fluoride in drinking water is typically around 1 ppm (parts per million). This level is beneficial for dental health as it helps in the formation of strong enamel.

3. **Effects of Deficiency**: A deficiency in fluoride can lead to tooth decay, as fluoride plays a crucial role in the mineralization of teeth.

4. **Conversion of Hydroxyapatite to Fluorapatite**: When fluoride is present in the right concentration, it can convert hydroxyapatite (the natural mineral form of calcium apatite found in teeth) into fluorapatite, which is harder and more resistant to decay.

5. **Threshold for Harm**: The concentration of fluoride becomes harmful when it exceeds 2 ppm. At this level, dental issues such as mottling (discoloration) of teeth can occur.

6. **Severe Toxicity Levels**: When fluoride concentration exceeds 10 ppm, it is considered highly toxic and can lead to serious health problems, including damage to bones and teeth.

7. **Conclusion**: Therefore, the level at which fluoride becomes poisonous and harmful to bones and teeth is over 10 ppm.

**Final Answer**: High concentration of fluoride is poisonous and harmful to bones and teeth at levels over **10 ppm**.

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