Question 2: The Journal of the American Medical Association
reported in 2002 on a study of 1,100 airline passengers who flew
from San Francisco to Denver. 515 of these passengers traveled on
planes where air was re-circulated, the remaining 585 traveled on
planes that did not recirculate air. Of those that did travel on
planes where the air was recirculated, 110 reported post-flight
respiratory problems. Of those on planes that did not recirculate
the air, 108 reported post-flight respiratory problems....