A recent ADB conference in Indonesia said that air pollution had reached serious levels in several Asian cities, with the problem worsening due to increased urbanisation and motor vehicle use.

The Manila-based bank cited China, already the world's fourth-largest economy, where the number of cars and sport utility vehicles could rise by as much as 15 times over the next 30 years to more than 190 million vehicles. In India, the growth could be as much as 13-fold, it said.

Correspondingly, carbon dioxide emissions could be expected to rise by 3.4 times for China and 5.8 times for India over the same period, the ADB study said. To help address these problems, the Indonesia conference, attended by representatives of 20 Asian countries, issued a call for a review of air quality standards and air pollution indices all over the region to make them more effective.