Permissible level of PM concentration
Q. According to WHO, what is the permissible level of PM concentration of micrograms per cubic metre?- Published on 21 Dec 15a. 20 micrograms per cubic metre
b. 25 micrograms per cubic metre
c. 50 micrograms per cubic metre
d. 100 micrograms per cubic metre
ANSWER: 25 micrograms per cubic metre
- The World Health Organization recommends 25 micrograms per cubic metre as the maximum safe level.
- Major components of PM: sulfate, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water.
- It consists of a complex mixture of solid and liquid particles of organic and inorganic substances suspended in the air.
- The most health-damaging particles are those with a diameter of 10 microns or less, (= PM10), which can penetrate and lodge deep inside the lungs.
- Chronic exposure to particles contributes to the risk of developing cardiovascular and respiratory diseases, as well as of lung cancer.
