Introduction Passive smoking has been linked to an increased morbid-mortality risk, mainly by cardiovascular and respiratory diseases. This is first Brazilian nationwide study that describes indoor passive smoking, at home and at work, among participants (15+ years) of the “Special Research on Smoking,” a sub-sample of the PNAD2008, a representative national home survey.

Methods Non-smokers who reported exposure to indoor household smoking were classified as daily or occasional passive smokers, based on the frequency of exposure. People with indoor occupations, who were non-smoker and reported exposure to smoking during their work journey were classified as worksite passive smokers. Associations with socio-demographic factors were verified by logistic regression analysis.

Results Among 25.005 participants, prevalence of daily and occasional household exposure was 12.5% and 21%, respectively. Compared to non-exposed, daily household exposure decreased with increasing age, schooling and income. Occasional household exposure is not influenced by age, but decreases with increasing schooling and income. Compared to the Southeast Region, the most developed region in Brazil, daily exposure was lower in the North and Central West and higher in the Northeast. Among 10.933 participants with indoor occupations, 55% of men and 45% of women reported worksite exposure to passive smoking and 67% of them also reported household exposure. Prevalence of worksite exposure is higher in men, older adults (55+ years) and among participants with lower schooling and income and lower among South Region residents.

Conclusion Exposure to secondhand tobacco smoke, at home and at work, is very high and socially unequal in Brazil.