Practice question

Classical London smog is called reducing smog because it forms under cool, humid conditions from coal smoke, sulfur dioxide, and reducing particulate material. Fog droplets promote sulfur chemistry and trap soot near the ground during temperature inversions. Los Angeles or photochemical smog is instead strongly oxidising because sunlight generates ozone, peroxyacyl nitrates, and other photochemical oxidants. Atmospheric inversions can trap contaminants near the surface, while wind, turbulence, precipitation, and chemical transformation determine their eventual distribution and removal. At organismal level, respiratory surfaces are especially exposed because large volumes of air contact thin, moist epithelia designed for rapid gas exchange. Sound classification links the source, atmospheric fate, exposure route, and mechanism of toxicity rather than relying only on the pollutant's name. Effective management combines cleaner fuels, emission standards, monitoring, urban planning, and protection of populations with high exposure or physiological vulnerability. The distinction is ecologically important because emission control must target either the directly released precursor or the product formed after atmospheric transport and reaction.