WHO region/country Democratic Republic of Congo North America and Latin America Eastern Mediterranean Africa Ethiopia The Gambia Kenya Mozambique Nigeria South Africa Tanzania Zimbabwe Others Canada United States Argentina Brazil Mexico Others Egypt Iran Pakistan Sudan Others Southeast Asia India Indonesia Thailand Others Western Pacific Australia China Malaysia Philippines Korea Others Europe Eastern Europe Southern Europe Western Europe 820 CDC, Centers for Disease Control and Prevention. Liu and Wu small nations. For these, we assumed a range for aflatoxin exposure that incorporated the ranges of the nations within the region for which we found aflatoxin data. These data provide the necessary infor- mation to calculate the total estimated cases of aflatoxin-induced HCC cases annually, worldwide. Table 4 lists populations for each relevant nation and world region. Accounting for chronic HBV infection prevalence as shown in Table 1, and the risk estimates for HBV-positive versus HBV-negative indi- viduals in Table 3, the numbers of cases of aflatoxin-induced HCC can be estimated in each world region. These are then summed to produce a global estimate of the number of annual aflatoxin-induced HCC cases. Our estimate is that anywhere from 25,200 to 155,000 annual HCC cases worldwide may be attributable to aflatoxin exposure. Figure 1 illustrates the distribution of HCC cases attributable to aflatoxin globally. The categories denote WHO world regions. Sub-Saharan Africa is the most important region for HCC cases attributable to aflatoxin; Southeast Asia and China (in the Western Pacific region) are also key regions where aflatoxin-related HCC is an important risk. Relatively fewer cases occur in the Americas, Eastern Mediterranean, and Europe. Although Australia and New Zealand are grouped with the Western Pacific region, these nations also have low aflatoxin-induced HCC incidence. It is notable that in Mexico, where HBV preva- lence is relatively low but aflatoxin contamina- tion in food is relatively high, aflatoxin appears to be a significant risk factor for HCC among those without HBV (an estimated 152–924 HCC cases per year per 100,000 people). Discussion Aflatoxin contamination in food is a serious global health problem, particularly in devel- oping countries. Although it has been known Table 1. Estimates of HBV prevalence in select countries based on HBsAg seroprevalence. References Batina et al. 2007; Mbendi et al. 2001 Abebe et al. 2003; Shimelis et al. 2008 Kirk et al. 2004; Vall et al. 1990 Kiire 1996; Tuei 1994 Cunha et al. 2007 Fasola et al. 2008 Custer et al. 2004; Kiire 1996 Hasegawa et al. 2006; Matee et al. 2006; Miller et al. 1998 Kiire 1996; Tswana et al. 1996 Kiire 1996; Matee et al. 2006; Tayou et al. 2009 Minuk and Uhanova 2001; Zhang et al. 2001 CDC 2009; Cohen et al. 2008; WHO 2005 Paraná and Almeida 2005; Torres 1996 Paraná and Almeida 2005; Torres 1996 Roman et al. 2009 Paraná and Almeida 2005; Torres 1996 Ismail et al. 2009; Lehman and Wilson 2009; Youssef et al. 2009 Kafi-Abad et al. 2009a, 2009b Butt and Amin 2008; Khattak et al. 2002 Elsheikh et al. 2007 Abou et al. 2009; Batayneh and Bdour 2002; Ameen et al. 2005; WHO 2005 Behal et al. 2008; Tandon et al. 1996 Hong et al. 2001; Merican et al. 2000; van Hattum et al. 2003 Tanprasert and Somjitta 1993 Alam et al. 2007; Ali et al. 2009; Jafri et al. 2006; WHO 2005 WHO 2007 Merican et al. 2000; WHO 2007 Merican et al. 2000; WHO 2007 Domingo 1997; Lansang 1996; WHO 2007 Song et al. 2009; WHO 2007 Gust 1996; Merican et al. 2000; Nakata et al. 1994 Magdzik 2000; Resuli et al. 2009 Da Villa 1998; Gogos et al. 2003; WHO 2005 Hahné et al. 2004; WHO 2005; Jilg et al. 2001 Chronic HBV prevalence (%) 6–10 6–7 15–20 11–15 4.5–10.6 13.2 3.3–10.4 5–9 10–15 9–20 1–2 0.3–2 0.8–1.1 2.1–3.4 < 0.3 0.5–3 2.2–10.1 0.41–0.56 3.3 6–26 0.65–10 2.4– 4.7 2.5–5 4.6–8 2–7 < 1 8–10 5 5–16 4–5 1–10 2–7 2–7 0.5–1 for several decades that aflatoxin causes liver cancer in humans, the exact burden of afla- toxin-related HCC worldwide was unknown. This study represents a first step in attempt- ing to estimate that burden. We find that at its lower estimate, aflatoxin plays a role in about 4.6% of total annual HCC cases; at its upper estimate, aflatoxin may play a role roughly 28.2% of all HCC cases worldwide. This large range stems from the considerable uncertainty and variability in data on cancer potency factors, HBV prevalence, aflatoxin exposure, and other risk factors in different world regions. The most heavily afflicted parts of the world are sub-Saharan Africa, Southeast Asia, and China. As indicated in Table 3, populations in developing countries in tropical and subtropi- cal areas are nearly ubiquitously exposed to moderate to high levels of aflatoxin. Aflatoxin is a controllable risk factor in food, yet the parts of the world in which the risk is par- ticularly high have limited resources to imple- ment most aflatoxin control strategies. Much Table 2. Maize and peanut consumption in select countries. Maizea Peanutb WHO region/country (g/person/day) (g/person/day) Africa Democratic Republic 57 52 North America and Latin America Eastern Mediterranean of Congo Ethiopia The Gambia Kenya Mozambique Nigeria South Africa Tanzania Zimbabwe Canada United States Argentina Brazil Mexico Egypt Iran Pakistan Sudan Southeast Asia India Indonesia Thailand Western Pacific Australia China Malaysia Philippines Republic of Korea Europe Eastern Europe Southern Europe Western Europe 83 57 248 248 57 248 248 248 86 86 86 63 300 136 32 35 57 35 35 35 86 35 35 59 59 32 148 33 13 52 11 11 52 11 11 11 17 17 17 2 5 5 2 18 52 18 18 18 17 18 18 2 2 2–10 7 10 Data are adapted from GEMS/Food Consumption Cluster Diets database (WHO 2006). aIncluding maize, flour and germ.bIncluding groundnuts in shell and shelled. ovlume 118 | number 6 | June 2010 • Environmental Health Perspectives