Abstract Introduction All manner of domestic and industrial activities lead Air pollution is not new, because there have been prob-to the injection of potentially toxic contaminants in to lems of one form or another since fire was first used andthe air. Most have little or no discernible impact on metals were first smelted, but the unbridled expansion ofthe environment, because the resulting concentrations industry in many parts of the world over the past centuryin the atmosphere fall well below the threshold for has resulted in changes in the chemical composition ofeffects. Others attain levels that are known to exceed the atmosphere on a scale unprecedented in human his-the recognized thresholds for damage to both fauna tory. In the first half of the 20th century, concerns overand flora. In this review the focus is on two of the gaseous air pollution focused on the impacts of sulphurdioxide (SO2most ubiquitous air pollutants—sulphur dioxide (SO ). However, the introduction of increasingly2)stringent legislation to control SO2and ozone (O emissions in the latter3). In many industrialized regions, ground-level concentrations of these gases are known to be half of the century has led to a dramatic decline inregional SO2high enough to depress crop yields and cause subtle concentrations in many areas. In contrast,shifts in the composition of natural (and semi-natural) the rapid industrialization of many Eastern European,plant communities. Consequently, these pollutants Asian and South American countries has resulted in agrowing concerns over the impacts of SO2constitute a novel evolutionary challenge for natural on flora andfauna in regions where SO2and managed ecosystems. Herein, evidence is pre- has not been a traditionalsented that some species are capable of responding problem. Combined with rapid expansions in population,to this challenge by evolving the ability to grow and the net result has been a steady rise in the total amountreproduce in areas subjected to potentially phytotoxic of pollutants injected into the earth’s atmospherepollutant concentrations. The prospects for breeding (Posthumus, 1998). In addition, there has been a funda-plants with enhanced resistance to the most common mental shift in the nature of the air pollution problemsair pollutants are discussed and the tangible prospects in industrialized regions; rising emissions of oxides ofof incorporating modern molecular approaches into nitrogen and volatile hydrocarbons resulting in growingexisting strategies for the identification, isolation and concerns over the impacts of photochemical oxidants (inparticular, ozone [O3manipulation of air pollution resistance in new stock ]). The past century has witnessed aare highlighted. steady rise in the tropospheric concentration of ozone inthe northern hemisphere (Volz and Kley, 1988; Marenco