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With reference to the fluoride ion concentration in drinking water, consider the following statements:
1. Soluble fluoride ions in drinking water make the enamel on teeth much harder.
2. The optimum level of fluoride in drinking water is up to 1 ppm.
3. Methemoglobinemia disease is caused by the excess of fluoride ions in drinking water.
Which of the statements given above are correct?
  • a)
    1 and 2 only
  • b)
    1 and 3 only
  • c)
    2 and 3 only
  • d)
    1, 2 and 3
Correct answer is option 'A'. Can you explain this answer?
Most Upvoted Answer
With reference to the fluoride ion concentration in drinking water, co...
  • The International Standards for drinking water are given below and they must be followed.
  • Fluoride: For drinking purposes, water should be tested for fluoride ion concentration. Its deficiency in drinking water is harmful to man and causes diseases such as tooth decay etc.
  • Soluble fluoride is often added to drinking water to bring its concentration up to 1 ppm or 1 mg dm–3. Hence statement 2 is correct.
  • The F– ions make the enamel on teeth much harder by converting hydroxyapatite, [3(Ca3(PO4)2.Ca(OH)2], the enamel on the surface of the teeth, into much harder fluorapatite, [3(Ca3(PO4)2.CaF2]. Hence statement 1 is correct.
  • However, F– ion concentration above 2 ppm causes brown mottling of teeth. At the same time, excess fluoride (over 10 ppm) causes harmful effects to bones and teeth, as reported from some parts of Rajasthan.
  • Nitrate: The maximum limit of nitrate in drinking water is 50 ppm. Excess nitrate in drinking water can cause diseases such as methemoglobinemia (‘blue baby’ syndrome). Hence statement 3 is not correct.
  • Lead: Drinking water gets contaminated with lead when lead pipes are used for the transportation of water. The prescribed upper limit concentration of lead in drinking water is about 50 ppb. Lead can damage kidney, liver, reproductive system etc.
  • Sulphate: Excessive sulphate (>500 ppm) in drinking water causes the laxative effect, otherwise at moderate levels it is harmless.
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Community Answer
With reference to the fluoride ion concentration in drinking water, co...
1. Soluble fluoride ions in drinking water make the enamel on teeth much harder.
- This statement is correct. Fluoride ions, when present in drinking water, can be absorbed by the enamel on teeth and make it more resistant to acid attacks, thus strengthening the teeth and preventing tooth decay.

2. The optimum level of fluoride in drinking water is up to 1 ppm.
- This statement is correct. The recommended level of fluoride in drinking water is up to 1 ppm (parts per million). This concentration is considered optimal for dental health and helps in preventing tooth decay without causing any adverse effects.

3. Methemoglobinemia disease is caused by the excess of fluoride ions in drinking water.
- This statement is incorrect. Methemoglobinemia, also known as "blue baby syndrome," is a condition where the blood is unable to carry sufficient oxygen due to the presence of excessive levels of methemoglobin. Methemoglobinemia is not caused by the excess of fluoride ions in drinking water. It is primarily caused by the presence of certain chemicals, such as nitrates, in drinking water.

Based on the explanation above, the correct answer is option 'A' - 1 and 2 only.
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With reference to the fluoride ion concentration in drinking water, consider thefollowing statements:1. Soluble fluoride ions in drinking water make the enamel on teeth much harder.2. The optimum level of fluoride in drinking water is up to 1 ppm.3. Methemoglobinemia disease is caused by the excess of fluoride ions in drinking water.Which of the statements given above are correct?a)1 and 2 onlyb)1 and 3 onlyc)2 and 3 onlyd)1, 2 and 3Correct answer is option 'A'. Can you explain this answer?
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With reference to the fluoride ion concentration in drinking water, consider thefollowing statements:1. Soluble fluoride ions in drinking water make the enamel on teeth much harder.2. The optimum level of fluoride in drinking water is up to 1 ppm.3. Methemoglobinemia disease is caused by the excess of fluoride ions in drinking water.Which of the statements given above are correct?a)1 and 2 onlyb)1 and 3 onlyc)2 and 3 onlyd)1, 2 and 3Correct answer is option 'A'. Can you explain this answer? for UPSC 2025 is part of UPSC preparation. The Question and answers have been prepared according to the UPSC exam syllabus. Information about With reference to the fluoride ion concentration in drinking water, consider thefollowing statements:1. Soluble fluoride ions in drinking water make the enamel on teeth much harder.2. The optimum level of fluoride in drinking water is up to 1 ppm.3. Methemoglobinemia disease is caused by the excess of fluoride ions in drinking water.Which of the statements given above are correct?a)1 and 2 onlyb)1 and 3 onlyc)2 and 3 onlyd)1, 2 and 3Correct answer is option 'A'. Can you explain this answer? covers all topics & solutions for UPSC 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for With reference to the fluoride ion concentration in drinking water, consider thefollowing statements:1. Soluble fluoride ions in drinking water make the enamel on teeth much harder.2. The optimum level of fluoride in drinking water is up to 1 ppm.3. Methemoglobinemia disease is caused by the excess of fluoride ions in drinking water.Which of the statements given above are correct?a)1 and 2 onlyb)1 and 3 onlyc)2 and 3 onlyd)1, 2 and 3Correct answer is option 'A'. Can you explain this answer?.
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