The spreading of pollutants from a point of release in air, soil and water. The dispersion of air pollutants is heavily influenced by how and where the pollutant is emitted, e.g., by continuous low-level versus accidental releases, multiple stacks versus a few, or the height of the stacks. The nature of the local terrain meteorology and the chemistry of the released material strongly influence the pattern of regional and, finally, global dispersion and transport.