Which one of the following is not correct with regard to the...

Particulate matter is divided into its sizes. Settleable $(\mathrm{PM}>10 \mu \mathrm{m})$ and suspended (PM < $10 \mu \mathrm{m})$. Particles less than $2.5 \mu \mathrm{m}$ diameter are most harmful. They pass deep into lungs, causing respiratory problem, cause inflammation and damage to the lungs. It cannot directly enter into our circulatory system, but through respiratory system. Related Theory Air Quality is measured using a metric called Air Quality Index (AQI). AQI will display the changes in air pollution in the atmosphere. Clean air is extremely important to maintain good health and the environment. Our atmosphere is predominantly made up of two important gases that are vital for life on earth, these are Oxygen and Nitrogen. Central Pollution Control Board (CPCB) has developed this Air Quality Index in consultation with IIT-Kanpur and air quality-professionals and experts. The most common measurement used to measure air quality is PM 2.5 and PM 10. It measures the particles in micrograms per cubic metre.