27, 29, 30, 31 There is also considerable overlap in the radiologic and histopathologic findings of these entities.24, 26 SHS is composed of side stream smoke (about 80%) and exhaled mainstream smoke with similar carcinogenic, toxic and irritant chemicals as are found in mainstream smoke. Our findings of the relation between SHS exposure and GGO could be caused by the same kind of pathological changes that are noted in active smokers. GGO might represent a mild form of RB, RB-ILD or DIP, and the linear/irregular opacities could indicate mild fibrosis due to long-lasting exposure. We excluded current smokers from our study population and controlled for ex-smoking in the multivariate analyses to ensure that active smoking could not explain our findings related to SHS exposure.