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

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

Which of the statements given above are correct?

(a) 1, 3 and 4

(b) 1 and 4 only

(d) 1 and 2 only

Explanation

In the context of WHO Air Quality Guidelines, the correct statements are:

The 24-hour mean of PM2.5 should not exceed 15 µg/m³ and annual mean of PM2.5 should not exceed 5 µg/m³. (Correct)
- The WHO guidelines state that the 24-hour mean of PM2.5 should not exceed 15 µg/m³, and the annual mean should not exceed 5 µg/m³.
In a year, the highest levels of ozone pollution occur during the periods of inclement weather. (Incorrect)
- Ozone pollution is most likely to reach unhealthy levels on hot sunny days in urban environments, but it can still reach high levels during colder months.
PM10 can penetrate the lung barrier and enter the bloodstream. (Incorrect)
- Particles with a diameter of 10 microns or less (PM10) can penetrate and lodge deep inside the lungs. However, it is the smaller particles with a diameter of 2.5 microns or less (PM2.5) that can penetrate the lung barrier and enter the bloodstream.
Excessive ozone in the air can trigger asthma. (Correct)
- High levels of ground-level ozone can trigger a variety of health problems, including asthma.

Based on the analysis, the correct answer is (a) 1 and 4.

WHO Air Quality Guidelines are evidence-based recommendations of limit values for specific air pollutants developed to help countries achieve air quality that protects public health.
The guidelines cover common air pollutants such as particulate matter (PM2.5 and PM10), ozone (O3), nitrogen dioxide (NO2), and sulfur dioxide (SO2).
Exposure to air pollution is estimated to cause millions of deaths and loss of healthy years of life every year.
Air pollution is a risk factor for noncommunicable diseases such as ischemic heart disease, stroke, chronic obstructive pulmonary disease, asthma, and cancer.
Particulate matter can have various health effects depending on its size. PM2.5 is more likely to travel into and deposit on the surface of the deeper parts of the lung, while PM10 is more likely to deposit on the surfaces of the larger airways of the upper region of the lung.
Ground-level ozone is a harmful air pollutant and the main ingredient in smog. It is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight.