Environmental health: chlorination: practice question

A PSM question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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PSM · Environmental health: chlorination

Sample item

What is the main purpose of residual chlorine in a public water supply?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Provide continuing protection against microbial contamination in distribution

Residual chlorine provides ongoing disinfectant activity as water travels through the distribution system, helping protect against recontamination. Dose must be balanced with water quality and safety standards.

Option by option

  • A. Increase water hardness

    Hardness is caused mainly by calcium and magnesium salts.

  • B. Remove all dissolved salts

    Chlorination does not remove all dissolved salts.

  • C. Provide continuing protection against microbial contamination in distribution (correct)

    Correct. Residual disinfectant protects water beyond the treatment point.

  • D. Measure sewage flow

    Sewage flow needs separate environmental measurement.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this PSM question

What is the answer to this PSM question?

The best answer is C, Provide continuing protection against microbial contamination in distribution. Residual chlorine provides ongoing disinfectant activity as water travels through the distribution system, helping protect against recontamination.

Why is "Increase water hardness" not the answer?

Hardness is caused mainly by calcium and magnesium salts.

Why is "Remove all dissolved salts" not the answer?

Chlorination does not remove all dissolved salts.

Why is "Measure sewage flow" not the answer?

Sewage flow needs separate environmental measurement.

What concept does this question test?

It tests Environmental health: chlorination in PSM. Dose must be balanced with water quality and safety standards.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Environmental health: chlorination?

Practise biostatistics with small calculations until sensitivity, predictive values and risk measures are automatic. Then use the flashcards and the other PSM questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.