incidence data of 355 populations from the literature, covering most countries in the world (Table S2). Central and Southeast China were examined in detail. Figure 3 illustrates the world distribution of esophageal cancer incidence and the details in East Asia. The extremely high incidences only appear in East Asia and some populations in Central Asia where the frequency of ALDH2*504Lys carriers is also high. However, comparison of Figure 2 and Figure 3 shows that the distributions are far from identical. However, the high cancer incidence areas mostly fall into the high frequency area of the derived allele carriers. The acetaldehyde accumulation resulting from ALDH2*504Lys in those who drink alcohol is certainly not the only risk factor for esophageal cancer. As noted above, ALDH2 also has other metabolic functions that could be independently influencing the distribution of ALDH2 variants (Li et al., 2006; Larson et al., 2007). Some environmental factors such as soil and vegetation characteristics and life styles may also be associated with the esophageal cancer risk (Wu et al., 2007; Fan et al., 2008; Moradi, 2008).
