Nicotine & Tobacco Research

toxic substances, including carcinogens, organic compounds, solvents, and gases. It is the main etiologic agent in chronic obstructive pulmonary disease (Raherison & Girodet, 2009) and lung cancer (Yao & Rahman, 2009). Passive smoking (also known as secondhand smoking) is the inhalation of smoke that comes from the burning cigarette (sidestream smoke) combined with the smoke breathed out by the smoker (mainstream smoke). Sidestream smoke makes up the majority of secondhand smoke and is more toxic than mainstream smoke. The combination of mainstream and sidestream smoke makes up environmental tobacco smoke (ETS). In 2002, the International Agency for Research on Cancer (2004) classified ETS as a “known human carcinogen” (Group 1). Passive smoking carries almost the same health risks a