1. The World Health Organization says outdoor air - for instance - in Beijing - New Delhi and Karachi is severaltimes more polluted that the outdoor air in Berlin - London and Paris. 2. But the typical indoor air in a developing country house with an open fire is many times more pollutedthan Beijing - New Delhi or Karachi.(c)Another 1.4 billion are still cooking with traditional - polluting stoves - and even improved stoves cause more pollution than found in most cities. 4. That is why indoor air pollution kills 4. 3 million people each year - making it one of the world's leading causes of death. 5. Yet indoor air pollution is rarely among the big issuesthe world discusses.