Previous studies have suggested associations of adult exposures to secondhand smoke (SHS) with respiratory symptoms, but no study has focused on blue-collar industrial environments. We assessed the association between SHS and respiratory symptoms in 1,562 non-current smoking U.S.
Please note studies suggest, this is an important statement. Epidemiology studies on SHS do not prove causation. It is just a hypothesis. Results under 2.0 are statistically insignificant.