PM stands for a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. Particle pollution includes PM₁₀ - inhalable particles, with diameters that are generally 10 micrometers and smaller and PM_2.5 - fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller.

These particles come in many sizes and shapes and can be made up of hundreds of different chemicals. Some are emitted directly from a source, such as construction sites, unpaved roads, fields, smokestacks or fires. Most particles form in the atmosphere as a result of complex reactions of chemicals such as sulfur dioxide and nitrogen oxides, which are pollutants emitted from power plants, industries and automobiles.

In Bangladesh, fossil fuel combustion produces large quantities of CO₂. Sources also include biomass burning, brick making, and traffic. Low efficiency combustion of fossil fuels emits black carbon particles and precursor gases that lead to the formation of tropospheric ozone. Black carbon (BC) is a major air pollutant and can act in two ways. First as a direct absorber of visible light and that provides direct warming in the lower atmosphere. The impact of BC concentration on global climate change has not been adequately considered to date, but recent studies have shown it could be the second largest contributor to global warming. Black carbon and tropospheric ozone, an element of smog, are not normally concerted to be greenhouse gases, but they warm the air by directly absorbing solar radiation. Together, the PM contributes towards forming the brown cloud that may have huge impacts on agriculture, health, climate, and the water budget of the country. In Bangladesh, the Atomic Energy Centre, Dhaka (AECD) of Bangladesh Atomic Energy Commission (BAEC) has been monitoring PM_2.5 and PM_2.5󈝶 . The study found high fine PM concentrations in Dhaka and are likely to have substantial public health impacts.

Air pollution has become one of the serious environmental concerns in urban areas, especially in view of the adverse health effects that have been associated with ambient fine particles. Up to 10% of respiratory infections and disease in Bangladesh may be attributable to urban air pollution. While the problem is most severe in Dhaka, both because the air quality is poor and large number of people are exposed. The air pollution is also becoming a growing concern in other major cities of Bangladesh. Like other developing Southeast Asian countries, emissions from various kinds of diesel vehicle and badly maintained automobiles contribute most to air pollution problems. A high concentration of air pollutants such as black carbon in Dhaka City air has been reported. Vehicular emissions, as well as burning of biomass for cooking and coal in the brick kilns around the city, are the main contributor to these emissions. Several Government policy interventions such as banning of two-stroke baby taxi, promotion of compressed natural gas (CNG) as alternative fuel for vehicles, improved inspection and maintenance of vehicles, especially diesel vehicles, etc. have been implemented to reduce the PM pollution in Dhaka city.