<h3><a href="http://www.huffingtonpost.in/audiomatic/podcast-in-the-hunt-for-a_b_8817610.html?utm_hp_ref=india" data-beacon='{"p":{"lnid":"hdln"}}'>Podcast: In the Hunt for Air That We Can Breathe</a></h3>

Consider this - the WHO says that "no threshold [of small particulate concentration] has been identified below which no damage to health is observed" and so, they've instead stated a guideline that aims to achieve the lowest possible PM concentration - this is 10 micrograms per cubic metre for PM 2.5. Delhi's is 15 times that much!