Discard the whole package if peanuts, corn, nuts, rice, or flour go moldy; do not pick out the moldy pieces and eat the rest, and spit out bitter-tasting nuts immediately

Discarding a package of peanuts or nuts, or a bag of rice or flour, costs a few to a few dozen yuan. Store grains and nuts somewhere dry, ventilated, and cool; buy small packages and avoid stockpiling. The hard part is accepting the waste, especially persuading older family members.

The International Agency for Research on Cancer classifies aflatoxins as Group 1 carcinogens, meaning they are known to cause cancer in humans; the cancer is liver cancer. They occur most commonly in peanuts and corn and are difficult to destroy through ordinary cooking such as stir-frying, boiling, or deep-frying. A Shanghai study followed 18244 middle-aged men from 1986, collecting one urine sample at enrollment. About 70000 person-years of follow-up identified 55 liver cancer cases. Fifty of these were compared with 267 people without cancer from the same cohort. Detectable urinary aflatoxin markers were associated with about 3.4 times the liver cancer risk (RR 3.4, 95% CI 1.1–10.0, the confidence interval). A positive hepatitis B surface antigen result was associated with about 7.3 times the risk (2.2–24.4). Having both was associated with about 59.4 times the risk (16.6–212.0) compared with having neither. An earlier analysis of the same cohort, adjusting for hepatitis B, smoking, drinking, and education, found about 3.8 times the risk with detectable toxin markers (1.2–12.2). Qidong, Jiangsu, formerly had high liver cancer incidence. From the 1980s, rice replaced corn as the local staple. Median blood toxin markers fell from 19.3 pg/mg in 1989 to undetectable levels in 2009, below 0.5. Among residents younger than 35, liver cancer mortality fell by more than half across birth cohorts from the 1960s to the 1980s. These cohorts were all born before universal newborn hepatitis B vaccination. The authors estimated that about 65% of the decline in liver cancer deaths could be attributed to reduced toxin exposure, with 83% of that benefit among people with hepatitis B. Global estimates suggest that, for the same toxin intake, carcinogenic potency is about 30 times greater in hepatitis B carriers than in people without the virus. Each year in China, some liver cancers are attributable to these toxins: about 5300–14400 cases among hepatitis B carriers and about 1990–4430 among people without the virus.

IARC (2012). Aflatoxins. In: Chemical Agents and Related Occupations. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol 100F, 225-248. https://publications.iarc.fr/123；Qian GS, Ross RK, Yu MC, 等 (1994). A follow-up study of urinary markers of aflatoxin exposure and liver cancer risk in Shanghai, People's Republic of China. Cancer Epidemiology, Biomarkers & Prevention, 3(1), 3-10. https://pubmed.ncbi.nlm.nih.gov/8118382/；Ross RK, Yuan JM, Yu MC, 等 (1992). Urinary aflatoxin biomarkers and risk of hepatocellular carcinoma. Lancet, 339(8799), 943-946. https://doi.org/10.1016/0140-6736(92)91528-G；Chen JG, Egner PA, Ng D, 等 (2013). Reduced aflatoxin exposure presages decline in liver cancer mortality in an endemic region of China. Cancer Prevention Research, 6(10), 1038-1045. https://doi.org/10.1158/1940-6207.CAPR-13-0168；Liu Y, Wu F (2010). Global burden of aflatoxin-induced hepatocellular carcinoma: a risk assessment. Environmental Health Perspectives, 118(6), 818-824. https://doi.org/10.1289/ehp.0901388；农业农村部油料产品质量安全风险评估实验室（武汉）(2020). 农产品及食品中黄曲霉毒素污染识别与预防. 农业农村部农产品质量安全监管司科普天地. https://jgs.moa.gov.cn/kptd/202011/t20201110_6356097.htm；广东省卫生健康委员会 (2015). 勿吃霉变食物 谨防黄曲霉素中毒. https://wsjkw.gd.gov.cn/gkmlpt/content/2/2129/post_2129622.html；USDA Food Safety and Inspection Service. Molds on Food: Are They Dangerous? https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/food-safety-basics/molds-food-are-they-dangerous

The benefit figures concern toxin exposure and liver cancer; no study directly measured how many liver cancers are prevented by discarding moldy food at home. The Shanghai study tested urine only once, at enrollment. Intake estimated from dietary questionnaires was not detectably associated with liver cancer, suggesting that questionnaires estimated exposure poorly and laboratory testing was needed. By 2009, toxin markers in Qidong residents were already undetectable. Most households today probably have far lower exposure than then; this is a judgment without nationwide figures. The benefit is therefore judged medium rather than mechanically rated large from the 3.4-fold figure. Why discard the whole package? Guangdong's health authority advises discarding a whole bag of nuts or peanuts if it smells off on opening, to prevent mold spores dispersing when shaken. Food that smells moldy should be discarded. US Department of Agriculture food safety guidance says to discard moldy peanut butter, legumes, and nuts, as well as cooked rice, pasta, and bread. Only firm, low-moisture vegetables such as cabbage and carrots can be eaten after cutting away at least 2.5 centimeters around the mold. China's Ministry of Agriculture and Rural Affairs warns that moldy peanuts may taste bitter and unusual; if accidentally put in the mouth, spit them out immediately and rinse. The combined risk is clearest in hepatitis B carriers; if never tested, see Section 1, Item 14 (get the five-marker hepatitis B panel). For oil purchases, see Item 40 in this section (do not buy unpackaged, small-workshop pressed peanut oil); this item concerns stored grains and nuts. Acute poisoning from soaked fungus and fermented cornmeal involves a different toxin; see Section 1, Item 48 (do not ferment cornmeal at home). Non-moldy nuts are still worth eating; see Item 22 in this section (eat a small handful of nuts daily). The main beneficiaries are you and family members sharing your meals.