People who smoke tobacco are at an increased risk of developing non-infectious diseases of the gas exchange system and the cardiovascular system. In 2004, a study was carried out on the most popular brands of filter cigarettes from each of the six World Health Organization (WHO) regions. In this study, the smoke passing through the filter was analysed for the tar, nicotine and carbon monoxide (CO) content for each brand of cigarette. For each WHO region, the mean content of tar, nicotine and carbon monoxide of the different brands of cigarette was calculated. The results are shown in Fig. 2.1. Key to WHO regions AFRO = African Region AMRO = Region of the Americas EMRO = Eastern Mediterranean Region EURO = European Region SEARO = South-East Asia Region WRPO = Western Pacific Region [Figure 2.1]