alarming facts about the link between rise in ground level ozone due to increased air pollution and increasing death rates in us cities have come to light. A study conducted by the Yale School of Forestry and Environmental Studies, New Haven, says even a 35 per cent reduction in the pollution caused by cars, power plants and industrial units for one day could save thousands across the country.

Ground-level ozone is considered dangerous, unlike stratospheric ozone, because the latter protects the Earth from harmful sunrays. While links between hospital admissions, especially pertaining to respiratory problems, and short-term ozone increase have been indicated earlier, a direct link between pollution and mortality rates has never been established. The study analysed 95 urban areas, housing about 40 per cent of the country's population. It compared ozone pollution with death rates between 1987 and 2000. "By linking day-to-day variations in ambient ozone levels and daily number of deaths and pooling the results across the 95 urban areas, this study provides strong evidence of short-term effects of ozone on mortality,' said Francesca Dominici, an author of the study. "This is one of the largest ozone pollution studies ever conducted,' said Michelle Bell, the study's lead author.

The study was published in the Journal of American Medical Association (