Delhi's air pollution is equivalent to four Bhopal's gas tragedies every year. While 2,500 people died in the Bhopal incident in 1984, nearly 10,000 people succumb to the fatal effect of air pollution in Delhi every year. These were some of the facts that have prompted the holding of a three-day seminar on health and environment. Speaking at a curtain raiser to the National Conference on Health and Environment beginning in New Delhi from 7th June, Mr Anil Agarwal director of the Centre for Science and Environment said that in most of the 23 Indian cities with a million-plus people, air pollution levels exceed World Health Organisation recommended standards.