However, total emissions were significantly less than those of North America and Europe during the same period. The severity of air pollution varies considerably across Asia. Smoke reached as far south as Darwin, Australia. Two of Asia's giant economies, China and India, rely heavily on coal. With increasing SO 2 emissions, acidification is an emerging issue.
Transportation contributes the largest share of air pollutants to the urban environment.
Lead pollution is a particular problem in megacities of Southeast Asia. The introduction of unleaded fuels is reducing average lead levels, although the rate of decline is slower in Asia than elsewhere. Tokyo Serious problem. WHO guidelines exceeded by more than 100 per cent Moderate to heavy pollution. WHO guidelines exceeded by up to 100 per cent Low pollution.