Environmental health: temperature inversion: 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: temperature inversion

Sample item

Every winter morning a valley city has a dense, persistent smog with high levels of particulates, even though emissions have not changed. What atmospheric phenomenon best explains this?

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

The answer and the reasoning

B. Temperature inversion trapping pollutants near the ground

In temperature inversion a layer of warm air sits above cooler surface air and acts as a lid, preventing vertical mixing so pollutants accumulate near the ground. It is common in winter and in valley cities. The London smog of 1952 is the classic example.

Option by option

  • A. The greenhouse effect

    The greenhouse effect warms the planet through heat-trapping gases and does not explain local smog episodes.

  • B. Temperature inversion trapping pollutants near the ground (correct)

    Correct. A warm layer over cool air traps pollutants close to the ground.

  • C. Depletion of the stratospheric ozone layer

    Ozone depletion increases ultraviolet radiation and does not trap smoke.

  • D. Acid rain

    Acid rain results from sulphur and nitrogen oxides dissolved in rain and does not trap particulates.

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 B, Temperature inversion trapping pollutants near the ground. In temperature inversion a layer of warm air sits above cooler surface air and acts as a lid, preventing vertical mixing so pollutants accumulate near the ground.

Why is "The greenhouse effect" not the answer?

The greenhouse effect warms the planet through heat-trapping gases and does not explain local smog episodes.

Why is "Depletion of the stratospheric ozone layer" not the answer?

Ozone depletion increases ultraviolet radiation and does not trap smoke.

Why is "Acid rain" not the answer?

Acid rain results from sulphur and nitrogen oxides dissolved in rain and does not trap particulates.

What concept does this question test?

It tests Environmental health: temperature inversion in PSM. It is common in winter and in valley cities. The London smog of 1952 is the classic example.

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: temperature inversion?

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.