Black smoke is a type of pollution produced by burning coal and oil, especially in diesel engines.
Black smoke is composed of carbon micro-particles of a diameter of less than 2.5 micrometers. These particles are so fine that they are not induced to settle through gravity and therefore remain suspended in the air for a long time. They also deeply penetrate the lungs, reaching the pulmonary alveoli.
In addition, these particles are often associated with other pollutants, such as polycyclic aromatic hydrocarbons (PAHs) or sulphur dioxide (SO2). These particles are condensation nuclei that adsorb different pollutants and facilitate their absorption by the respiratory tract.
Black smoke is therefore very toxic to human health and can have carcinogenic or mutagenic effects. Current regulations are increasingly addressing this type of smoke and other particles, through the implementation of measurement and emission reduction systems and exposure limit thresholds.
Black smoke coming out of incinerator smokestacks. © Anne Burgess, Geograph CC by-sa 2.0