The World Health Organization (WHO) released a report on the assessment of red meat and processed meat products, in which processed meat products are rated as carcinogens in category 1, while red meat is a carcinogen in category 2A. The most notable news is that “ham and bacon is a carcinogen, along with arsenic”. Is this really true? Can we still eat ham and bacon happily? Can we still eat ham and bacon happily? What are carcinogens? How are they classified? The number of people suffering from cancer is increasing, and the fear of cancer and the talk about cancer have become indisputable facts. The 2014 World Cancer Report released by the International Agency for Research on Cancer shows that there were more than 14 million new cancer cases worldwide in 2012, and the agency has predicted that the number will reach 22 million cases/year in the next 20 years. The medical community has a unified understanding of cancer, and prevention is more important than cure. Therefore, it is natural that the World Health Organization’s statement that processed meat is a class 1 carcinogen makes everyone so nervous. What exactly is a carcinogen? Broadly speaking, carcinogens are factors that can induce cancer in people, including various carcinogenic substances in the chemical and biological fields, as well as improper lifestyles and work styles that can easily induce cancer. The widely accepted classification of carcinogens comes from the International Agency for Research on Cancer (IARC), which was established in 1965 and is affiliated with the World Health Organization. Classification of carcinogens Class I carcinogens: substances with clear carcinogenic effects. For example, tobacco, alcoholic beverages, betel nut, aflatoxin, asbestos, etc. Class IIA carcinogens: Substances with a high probability of causing cancer. The criterion is that there are clear carcinogenic effects in animal experiments, but research in humans is still relatively limited. For example, high-temperature fried foods, high-temperature oil smoke, lead-free compounds, reversed work and rest schedules, etc. Class II B carcinogens: substances with low carcinogenic potential. The criterion is that experiments on animals and humans have not yet found clear carcinogenic effects. For example, fern, DDT insecticide, nitrobenzene, gasoline, automobile exhaust, electromagnetic radiation from electronic devices such as cell phones, etc. Class III carcinogens: Carcinogens that cannot be classified yet. For example, caffeine, xylene, saccharin, Valium, etc. Class IV carcinogens: substances that may not be carcinogenic to humans. Substances that lack sufficient evidence to support their carcinogenicity. For example, caprolactam. Carcinogenicity ≠ toxicity The phrase “listed with arsenic” expressed in many media articles is actually a very misleading interpretation, and people will think it is as toxic as arsenic. But in fact, this refers to the International Agency for Research on Cancer (IARC) carcinogenicity classification, and carcinogenicity and toxicity are two different things. Arsenic is indeed a very strong carcinogen, but what is more worrying about arsenic is its acute toxicity, which can kill people in very small amounts. If you eat arsenic, you’ll be poisoned before you get cancer. Processed meats like ham and bacon, on the other hand, are not acutely toxic. Carcinogen class ≠ carcinogen intensity The highest class of carcinogens, where bacon and ham are located, means that there is very conclusive evidence that the substance increases a person’s risk of cancer, but there is no direct link to the ability to cause cancer – how much of it you eat each day will give you cancer. Many of the carcinogens in this category are already familiar, such as aflatoxins, benzo(a)pyrene, cigarettes, betel nut, and others such as arsenic, cadmium, benzene, methanol, radon, coal tar, X-rays, and dioxins. However, there are many more that people do not expect, such as alcohol and alcoholic beverages, Chinese salted fish, solar radiation, ultraviolet light, indoor coal burning, rubber industry, etc. In the case of alcohol and alcoholic beverages, there is plenty of evidence that it increases the risk of various diseases and cancers, but people still drink it happily.