What is the correct increasing order of the prescribed limits for the following pollutants on a 24 hour basis in residential areas by the CPCB? Choose the correct answer from the options given below.

1.Suspended Particulate Matter (SPM)

2.Respirable Suspended Particulate Matter (RSPM)

3.Lead (Pb)

4.Ammonia (NH3)

A1, 2, 3, 4

B2, 1, 3, 4

C3, 4, 2, 1

D3, 2, 1, 4 ✓ Correct

Correct answer: (D) 3, 2, 1, 4

Explanation

The limits rise Lead, then RSPM, then SPM, then Ammonia, giving 3, 2, 1, 4.

Lead carries the strictest 24-hour residential limit, around one microgram per cubic metre.

Respirable particulate (RSPM/PM10) is capped near one hundred, higher than lead.

Total suspended particulate (SPM) is allowed a larger figure than RSPM.

Ammonia has the highest permitted value of the four, around four hundred.

Ranking the CPCB limits low to high yields Lead, RSPM, SPM, Ammonia.

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