The sources of Black Carbon (BC) in Kathmandu Valley are diesel and gasoline vehicles in the transport sector. Biomass, kerosene, animal residues and LPG are responsible for BC emission in residential sector. In commercial sector use of diesel generators for electricity production are responsible for BC emission. Use of coal and wood in the brick manufacturing process is main source of BC emission in industrial sector. Burning of death people especially in Pashupati area is also the source of BC in Kathmandu Valley.

Atmospheric Brown Cloud emission inventory excel work book developed by UNEP in 2013 is used to obtain the BC emission from various sources of Kathmandu Valley. Emission inventory is conducted by using secondary as well as primary data. The overall BC emission increased to 3800 tonne in 2014 from 2709 tonne in 2010. The share of transport, residential, commercial and industrial sector is 3339, 112, 244 and 103 tonne for year 2014. The major BC emission source is found to be transport sector with 87% of total BC emission in 2014. Diesel is found to be the major source of BC emission with emission of 3475 tonne in 2014.

BC contributes to the adverse impacts on human health. Short-term and long-term exposures to BC are associated with a broad range of human health impacts, including respiratory and cardiovascular effects as well as premature death.

Impact of BC on human health is studied on the basis of number of Chronic Obstructive Pulmonary Disease (COPD) patients admitted and deaths due to COPD for last five years from 2010 to 2014 in Bir Hospital, Tribhuwan University Teaching Hospital and Patan Hospital. It is found that correlation between percentage of COPD patient and BC emission is high with R² value of 0.824 from 2010 to 2014. So it can be said that increasing BC emission has direct impact on COPD patients from this research work.