New Delhi: Some of the world's largest and most densely populated cities have air that is so polluted that people suffer from lung diseases at rates that are significantly above global averages.
Birth defects in these cities are also at extraordinarily high levels, as are heart disease and cancer rates.
Many of these cities are among the fastest-growing in the world. And in some, residents burn wood and coal for warmth, releasing additional deadly pollution into the atmosphere.
Here are the ten most polluted cities in the world: