Particle emissions from combustion sources, including fossil fuels, biofuels, and biomass, are broadly referred to as particulate matter (PM).
They are usually classified into two types based on their sizes (diameter): PM2.5 and PM10. PM2.5 has diameter less than 2.5 micrometer, while PM10 has diameter less than 10 micrometer and includes PM2.5.
Black carbon, as well as secondary sulfate and nitrate particles formed from SOx or NOx precursors, is the major constituent of PM2.5.
It represents the solid fraction of PM2.5 that strongly absorbs light energy and converts it to heat, with a resultant effect of causing temperature change, melting of snow and ice (when deposited on snow or ice), and change in precipitation patterns.
Furthermore, because of its small size, PM2.5, which includes black carbon, easily penetrates human cells and blood and therefore has high negative impact on human health.