A GUIDE TO THE CONTROL OF PHOTOCHEMICAL POLLUTION

This paper reviews the present state of knowledge regarding the nature and effects of photochemical pollution and draws some conclusions concerning the setting of goals for oxidant concentrations and the most effective strategies for oxidant control. The nature of photochemical pollution is explored with some emphasis on the limitations of ozone as an indicator of pollution. The conclusion reached parallels that of the United States National Academy of Science to the effect that ozone is an acceptable indicator given current knowledge, but that its use should be reviewed periodically in light of any emerging information on the synergistic effects of ozone and nitrogen oxides. The role of the major chemical variables is discussed in some detail. The setting of overall goals for oxidant levels is discussed and standards used throughout the world are critically examined. It is concluded that there is insufficient information on the health effects of smog mixtures to permit the setting of a final oxidant goal for Australia. Options available for the control of oxidant formation are discussed. It is demonstrated that strategies based on the combined control of hydrocarbons and nitrogen oxide emissions can be as effective in reducing oxidant levels as strategies involving reduction of hydrocarbons only, and would require less stringent control standards to achieve this result. This analysis, together with the likely role of nitrogen oxides during extended irradiations, makes it prudent to effect some controls on both hydrocarbon and nitrogen oxides emissions, and to review the situation as more evidence becomes available from chemical studies. (TRRL)