Q. 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 PM 2.5 should not exceed 5 µg/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?

  • 1, 3 and 4
  • 1 and 4 only
  • 2, 3 and 4
  • 1 and 2 only

Answer: (b) 1 and 4 only

Notes:

  • The WHO Air quality guidelines are a set of evidence-based recommendations of limit values for specific air pollutants developed to help countries achieve air quality that protects public health.
  • The first release of the guidelines was in 1987. 
  • The guidelines offer guidance about these air pollutants: particulate matter (PM), ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2) and carbon monoxide (CO).
  • The guidelines stipulate that PM2.5 should not exceed 5 μg/m3 annual mean, or 15 μg/m3 24-hour mean; and that PM10 should not exceed 15 μg/m3 annual mean or 45 μg/m3 24-hour mean.
  • PM10 (particles with a diameter of 10 micrometres or less): these particles are small enough to pass through the throat and nose and enter the lungs. Once inhaled, these particles can affect the heart and lungs and cause serious health effects.
  • PM2.5 (particles with a diameter of 2.5 micrometres or less): these particles are so small they can get deep into the lungs and into the bloodstream. 
  • Particles with a diameter of 10 microns or less, (≤ PM10) can penetrate and lodge deep inside the lungs.
  • The even more health-damaging particles are those with a diameter of 2.5 microns or less, (≤ PM2.5). PM2.5 can penetrate the lung barrier and enter the blood system.
  • As ozone concentrations increase above the guideline value, health effects at the population level become increasingly numerous and severe. Such effects can occur in places where concentrations are currently high due to human activities or are elevated during episodes of very hot weather.
  • Ozone triggers asthma because it is very irritating to the lungs and airways. It is well known that ozone concentration is directly related to asthma attacks.

Inclement Weather

  • Inclement Weather means the existence of rain or abnormal climatic conditions (whether they be those of hail, snow, cold, high wind, severe dust storm, extreme high temperature or the like or any combination thereof) by virtue of which it is either not reasonable or not safe for workmen exposed thereto to continue working whilst the same prevail.