A photochemical reaction that occurs only in the presence of light. Deadly Smog was produced in London 1952 and Pennsylvania 1948 caused by a thermal inversion which trapped the smog close to the ground. The smog was comprised of sulfuric acid containing water droplets, which were produced as a result of the catalysis of the reaction of the sulfur dioxide to sulfur trioxide in the presence of fine ash particles. The sulfur trioxide is absorbed into the water droplets, producing a deadly aerosol of sulfuric acid. London Smog requires sulfur dioxide, ash and water, the sum of which is far worse than any of the three.
Technical innovations are in discovery with the aims to reduce unwanted by-products of combustion.
Generating clean air. Difficult decisions must be made balancing the needs of health and economy. Clean air costs money. Additionally, because air pollution crosses international boarders, global decisions must be arranged - a political battle when considering the health and economic choices which must be made. In making decisions toxicity, exposure and risk have to be weighed in the balance.