Background:
Despite public health intervention, exposure to secondhand smoke, specifically in the home, remains high. Secondhand smoke has been linked to several health outcomes however there is limited information on how secondhand smoke impacts on severity of smoking.

Methods:
We report interim results of a cross-sectional study among young men (10-34 years) attending five Voluntary Medical Male Circumcision (VMMC) clinics in South Africa. Data were collected on participant and parental smoking status; exposure to secondhand smoking and alcohol consumption. A qualitative urine test for cotinine and a breathalyser test for Carbon monoxide measured in parts per million (COppm) were administered. COppm scores were classified into two categories: moderate/mild and severe. Secondhand smoking was defined as exposure to indoor and family members smoking. Logistic regression was used to determine risk factors associated with severe smoking.

Results:
Of the 2465 participants, median age 20 (IQR: 13-27) years, 32.5% (785/2418) tested positive for urine cotinine of which 98.6% (774/785) had a COppm result. COppm result showed 53.2% (412/774) were severe smokers, 46.8% (362/774) were moderate/mild smokers. A total of 46.3% (189/408) of severe smokers reported often having someone smoking in their home of whom 27.8% (72/259) reported that their mother and 59.9% (100/167) report that their father smokes. Overall, 80.3% (330/411) of severe smokers self-reported drinking alcohol. Multivariate analysis adjusting for age and alcohol use showed that severe smoking was associated with often exposure to indoor smoking at home (OR: 1.612 95%CI: 1.195-2.173) and to family members that smoke (OR: 3.495 95%CI: 1.413-8.646).

Conclusions:
Family members who smoke and alcohol use put young men at risk of severe smoking. Rules and social norms must encourage smokers to smoke outside of their houses. Policy interventions should focus on highlighting the risks and reducing the prevalence of secondhand smoking.