Question
GSMediumPrelims 2022Environment & Ecology

In the context of WHO Air Quality Guidelines, consider the following statements:

  1. The 24-hour mean of PM2.5 should not exceed 15 ug/m³ and annual mean of PM2.5 should not exceed 5 ug/m³.
  2. In a year, the highest levels of ozone pollution occur during the periods of inclement weather.
  3. PM10 can penetrate the lung barrier and enter the bloodstream.
  4. Excessive ozone in the air can trigger asthma.

Which of the statements given above are correct?

Explanation

Statement 1 is correct. The WHO recommends that the 24-hour mean of PM2.5 should not exceed 15 ug/m³ and the annual mean should not exceed 5 ug/m³. These are the current most stringent guidelines set by WHO to protect public health.

Statement 2 is incorrect. Ozone pollution typically peaks during sunny and stagnant weather conditions, not during inclement weather like rain or storms.

Statement 3 is incorrect. While PM10 (≤ PM10) particles can enter the deep lungs and cause respiratory issues, it's the much finer PM2.5 (≤ PM2.5) particles and ultrafine particles that effectively penetrate the lung barrier (alveoli) to enter the bloodstream, affecting the heart, brain, and other organs. PM10 typically deposits in larger airways, whereas PM2.5's tiny size allows it to cross into the circulatory system, making it more dangerous. 

Statement 4 is correct. Excessive ozone exposure can trigger asthma attacks and worsen respiratory problems. Ozone irritates the respiratory tract, making it harder to breathe.

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