Stop treating fog mai as a joke – it is a Class 1 carcinogen

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A woman of Asian appearance was riding a bicycle, her brows slightly furrowed above her white mask. Behind her, the flowing traffic and the buildings along the road were blurred by the thick gray mist, making it impossible to tell which city this street scene belonged to. This is the cover of an English e-book titled \"Air Pollution and Cancer\", published on October 17, 2013, by the International Agency for Research on Cancer, which is part of the World Health Organization (WHO). Released around the same time as this e-book was the Report No. 109 of the IARC Monograph Programme, published on October 24, 2013. These publications announce an important conclusion reached by IARC after reviewing a large amount of scientific research: outdoor air pollution is a carcinogen that causes cancer in humans. The newly released Report No. 109 concludes that there is sufficient evidence to show that air pollution can cause lung cancer ； There is also evidence showing that air pollution can increase the risk of bladder cancer. In a press release, IARC further stated that air pollution is already the “most widespread environmental carcinogen.” Group 1 carcinogens refer to substances for which there is ample evidence of their carcinogenicity to humans. “The air we breathe every day is already contaminated with carcinogens. ” Dr. Kurt Straif, head of the IARC Monographs Department, said in a press release, “We now know that outdoor air pollution is not only a major threat to overall health but also an important environmental factor contributing to cancer deaths.” ” The conclusions of the report do not mention China directly, but IARC states that these conclusions apply to all regions of the world. After the announcement of the above conclusions, Caijing journalists contacted several Chinese scholars in environmental health. The scholars interviewed generally agreed with the IARC’s conclusions and emphasized its authority. Yang Gonghuan, former deputy director of the Chinese Center for Disease Control and Prevention, pointed out that IARC is one of the most authoritative institutions for cancer research worldwide, and its research findings are highly recognized globally. IARC’s classification of air pollution as a Group 1 carcinogen means that the risk of it causing cancer has risen to a very high level: \"If classified as a Group 1 carcinogen, it indicates that the evidence of its carcinogenicity is very strong, with evidence from human studies available.\" ” Wei Fusheng, an academician of the Chinese Academy of Engineering who has spent many years studying air quality, emphasized that the IARC report should be viewed in a balanced manner – air particles, as a type of composite pollutant, may indeed increase the risk of cancer, but the Chinese public need not panic needlessly. He said that while the IARC report indicates a certain link between particulate matter and cancer, it also states that this is an event with a low probability of occurrence. Pan Xiaochuan, a professor at the School of Public Health at Peking University, believes that in China, air pollution has sparked public concern in recent years, and research on its health impacts has become a hot topic in academic circles. The IARC report is highly timely; its clear classification of air pollution as a carcinogen is of great significance. The IARC report provides the latest evidence and references on the health impacts of air pollution, and it may even influence the development of certain international standards. “China **should pay attention to it. ” Pan Xiaochuan said. Why is air carcinogenic? According to the definition of the International Organization for Standardization (ISO), air pollution, also known as atmospheric pollution, refers to the phenomenon in which certain substances are released into the atmosphere due to human activities or natural processes; when these substances reach sufficient concentrations and remain there for enough time, they can harm human comfort, health, and well-being, as well as the environment. How does air pollution cause people to fall ill or even develop cancer? Wang Yuesi, a researcher at the Institute of Atmospheric Physics of the Chinese Academy of Sciences, said in an interview with Caixin reporters that the common indicators used globally to measure air pollution include PM2.5, PM10, nitrogen oxides, sulfur dioxide, carbon monoxide, ozone, and others. Apart from PM2.5 and PM10, the other indicators are relatively simple, measuring either a single pollutant or a small number of pollutants in the air. The particulate matter indicators PM2.5 and PM10 are mixtures, making them more suitable for measuring overall air pollution. PM2.5 with a particle size of less than 2.5 micrometers can pass through the respiratory tract and enter the body easily, as neither human nasal hair nor ordinary masks can block it. It is generally believed that PM2.5 is a substance that severely damages human health. A study conducted by Wang Yuexi in recent years showed that the mortality rate from respiratory diseases (including lung diseases) among residents of Beijing is positively correlated with PM2.5 concentrations, but not with PM10 particles with a diameter greater than 2.5 micrometers. Wang Yuexi categorizes the harm caused by PM2.5 to human health into physical, chemical, and biological aspects. In terms of physical properties, regardless of what the fine particles are or whether they are toxic or non-toxic, their entry into the human body is harmful to it. “Whether it’s particles, sand, coal, or dust, nothing should get stuck in the respiratory tract; if it enters the lungs, it can cause blockages. ” Biological characteristics refer to the fact that PM2.5, as a carrier, may carry viruses and bacteria, such as those causing influenza or even infectious diseases. SARS and H7N9 could potentially spread via mist. PM2.5 has the most complex chemical properties and causes the greatest harm to humans. “Put simply, of the gases inhaled by the human body, all except oxygen are of little use. All the chemicals inhaled can potentially cause harm to the human body. ” As the leader of an air pollutant tracing project at the Chinese Academy of Sciences, Wang Yuexi explained that there could be tens of thousands of different chemical substances in the air. In Beijing’s PM2.5, about 100 chemical substances can be identified through simple analysis, and up to 30,000 may be detected with more detailed analysis. Wang Yuessi classified PM2.5 into seven categories based on their chemical properties, such as sulfates and ammonium salts. He believes that among the chemical components in PM2.5, those most harmful to the human body are water-soluble and fat-soluble chemicals, as they can dissolve in the human body. Water-soluble substances are mainly inorganic salts, such as sulfates, nitrates, and ammonium salts; they are difficult to excrete once they enter the lungs. Sodium nitrite, a carcinogenic substance, belongs to this category. Fat solubility means the ability to dissolve in fats; it primarily refers to organic substances, such as polycyclic aromatic hydrocarbons, which have attracted global attention in recent years due to their carcinogenic properties. In addition, air pollution contains hormonal substances, most of which are estrogenoids, which may affect human fertility. Pan Xiaochuan pointed out from another perspective that the carcinogenic substances in air pollution are mainly classified into three categories: heavy metals, polycyclic aromatic hydrocarbons, and persistent organic pollutants. In China, various forms of pollution such as large-scale coal combustion, emissions from low-quality fuels, and poorly regulated industrial discharges have led to the repeated accumulation of these dangerous carcinogens in the atmosphere. Carcinogenic heavy metal elements include arsenic, which causes lung cancer, and hexavalent chromium, which causes nasopharyngeal cancer; other heavy metal elements whose carcinogenicity is not yet clear, such as mercury, have also been shown to be toxic to the human body. Wei Fusheng pointed out that in the 1990s, his research team conducted studies on thousands of children in four cities including Guangzhou, and the results showed that PM2.5 and PM10 levels in the air were positively correlated with the incidence of respiratory diseases among children, with an impact that was even greater than that of sulfur dioxide and nitrogen oxides. Asthma is significantly affected by the combined effects of particulate matter, sulfur dioxide, and nitrogen oxides.