PM2.5 particulate matter is 2.5 micrometers in diameter or smaller, and can only be seen through an electron microscope. PM2.5 is capable of entering the bloodstream via the lungs. These fine particles are produced from all types of combustion, including motor vehicles, coal-burning power plants, waste burning, residential wood burning, forest fires, agricultural burning, and some industrial processes.
Regarding noise pollution, Sound Quality National Standard 2012 is the only benchmark set by the Government of Nepal.
Moreover, Nepal does not have any specific regulation, robust implemented/enforced rules or long term concrete plans to control noise pollution in various urban cities. This is 2021 and it is sad to know that the reality on the ground is still a far cry from the national standards; except during the Covid-19 lockdown hours, of course.
L10 is the sound level in dB that is exceeded 10% of the time over measurement period.
L50 is the sound level in dB that is exceeded 50% of the time over measurement period.
L90 is the sound level in dB that is exceeded 90% of the time over measurement period.
Leq is the average equivalent continuous sound level over a particular time period (T)
Lmax is the maximum sound level measured during the measurement period with the sound
meter set on SLOW response.
Lmin is the minimum sound level measured during the measurement period with the sound meter set on SLOW response.
Noise pollution has been ignored in Nepal for a long time now and the situation is even worse in big cities like Kathmandu.
(Source: Noise Level Status in Siddharthanagar Municipality, Rupandehi, Nepal, Lakshmi Nath Bhattarai)