Feature Health & Medicine Bad Breath Studies are homing in on which particles polluting the air are most sickening — and why By Janet Raloff July 3, 2009 at 2:15 pm - More than 2 years ago Share this:Share Share via email (Opens in new window) Email Share on Facebook (Opens in new window) Facebook Share on Reddit (Opens in new window) Reddit Share on X (Opens in new window) X Print (Opens in new window) Print Tasteless. Invisible to the eye. Air contaminants less than a tenth the size of a pollen grain are nevertheless dangerous.Even on a clear, sunny day, many tens of thousands — and potentially millions — of tiny particles cloud every breath you take.