Soot, respiratory toxicity

With aerosols, the degree of penetration into the respiratory tract depends mainly on the size of the particles, with the smallest particles (<5 pm aerodynamic diameter) having the greatest probability of reaching the distal airways and alveoli. Such small particles are often produced by combustion processes or by condensation of vapours. The particles may be toxic by themselves (e.g. cadmium oxide, CdO), or they may carry irritants, such as sulphates or aldehydes adsorbed onto soot particles. 

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