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 Click to share on Facebook (Opens in new window) Facebook Click to share on Reddit (Opens in new window) Reddit Click to share on X (Opens in new window) X Click to 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.