When a person steps out of his home, he may be surrounded by carcinogens. This is not alarming – on October 17, the International Agency for Research on Cancer (IARC), a division of the World Health Organization (WHO), announced that outdoor air pollution has been identified as a new carcinogen, with carcinogenic levels grouped with smoking, eating moldy food, exposure to ultraviolet radiation, and breathing formaldehyde.
”The air we breathe has been contaminated with a carcinogenic mixture that not only poses a threat to environmental health, but is also one of the leading causes of cancer deaths.” A director of the International Agency for Research on Cancer told the media this. The main responsibility of this authoritative body is to conduct and promote research on the causes of cancer and to investigate and study the epidemiology of cancer worldwide.
The impact of air pollution on health has long been a topic of concern for scientists around the world, but its carcinogenicity has not been clearly demonstrated in every experiment. For this reason, it has even caused some controversies.
But this time the IARC report declared a definitive result. “The conclusion that outdoor air pollution acts as a human carcinogen was made by a working team of 24 of the world’s leading scholars who reviewed over 1,000 scientific papers and then made it on that basis.” Dana Loomis, one of the study’s sponsors and a professor at Nebraska State University Medical Center, told China Youth Daily.
On Oct. 24, the top medical journal The Lancet published a detailed report specifically on the issue. It showed that the main subjects of the more than 1,000 papers were people living in Europe and the United States, where the amount of PM2.5 per cubic meter of air is around 20 to 30 micrograms.
Outdoor pollution air and aflatoxin, arsenic, asbestos, formaldehyde, etc. put on the same “hat”
”Every day, a person takes several thousand breaths and inhales about 10,000 liters of air. As a result, a person’s lungs can inhale significant doses of air pollutants, even if those components are in small amounts.” wrote project team member Jonathan Samet in a special report released by the International Agency for Research on Cancer titled “Air Pollution and Cancer.
This time, added to the list of Class I carcinogens is particulate matter, in addition to air pollution. In the words of Professor Zhang Jinliang of the Chinese Academy of Environmental Sciences, the tiny particles that have been plaguing scientists for so long have finally been “put into a hat.
”Air pollution here does not refer to a particular pollutant,” said Zhang Jinliang, “it is the air that everyone breathes. There are no exceptions.”
The “hat” called “a class of carcinogens” means that the polluted outdoor air is a mixture that is definitively carcinogenic to humans. “The so-called human carcinogen for sure, that is to say, epidemiological evidence as well as animal experiments are sufficient to prove that this substance has a carcinogenic effect on humans.” Zhang Jinliang told China Youth Daily.
Nowadays, with air pollution with this carcinogenic “hat”, there are aflatoxin, arsenic, asbestos, formaldehyde, tobacco and betel nut and other substances.
These substances are identified one by one by the International Agency for Research on Cancer. Since 1971, the agency has been organizing experts to “weave the hat” – to collect and review information on the carcinogenic risks of various substances to humans around the world, and to conduct epidemiological surveys and studies on cancer. The organization divided carcinogens into five categories: carcinogenic, likely to cause cancer, probably carcinogenic, unknown and probably not carcinogenic. The “probably carcinogenic” category includes many things that are used in everyday life: coffee, kimchi, etc.
”Our role as a scientific institution is to provide health information to the World Health Organization or governments so that they can take appropriate measures to address the situation at hand based on the results.” Dr. Loomis explained to reporters in an email.
In fact, the papers they have written on the subject are so authoritative that the media have called them “an encyclopedia of carcinogens. Over the years, the institute has declared more than 110 carcinogens.
Such an organization, of course, can not ignore the increasingly serious problem of outdoor air pollution. “Motor vehicle exhaust, industrial production, power generation, the burning of solid fuels in homes, and a variety of other sources have polluted the world’s air.”
But previously, even in the most recent and authoritative medical textbooks, air pollution was not listed as a cause of cancer, although diesel exhaust has long been listed as a carcinogen. “The process of ‘putting on the hat’ is more cautious,” said Zhang Jinliang, who, as director of the Environmental Pollution and Health Research Unit at the institute, was once invited by the WHO’s Indoor Air Pollution Expert Group to participate in the WHO’s international research project. She was under the impression that the International Agency for Research on Cancer had called for researchers interested in related fields in January of this year.
This task force eventually selected 24 experts to specifically assess the carcinogenicity of air pollution. They come from 11 different countries and “are all familiar with the field.
At the same time, the cancer research agency is also looking for academics around the world for “any research you think is relevant” that could be related to atmospheric science, epidemiology, toxicology, cancer biology and more. “If the expert’s field of study is the relationship between the outdoor atmosphere and cancer, then he should collect all the information related to atmospheric pollution and cancer worldwide.
After these papers were screened based on their quality, the more than 1,000 materials that were eventually presented to the work team were picked out.
”In fact, it was a very scientific and complex process.” Zhang Jinliang concluded.
”The scientific data took into account the following aspects: firstly, epidemiological studies of human exposure to contaminated air, secondly, those experiments on cancer in animals exposed to the air, and also studies on the mechanism between cancer and air pollution.” Dr. Loomis told the reporter this.
The much-divergent information from around the world points to a common result. Loomis was clearly confident in the conclusion: “Based on this extensive scientific information, our group concluded that there is ample evidence that polluted air is a carcinogen, both for humans and for animals. There is also strong evidence that exposure to polluted air triggers cellular damage and other changes that can lead to cancer.”
He also noted that it is not just lung cancer that is at increased risk with increased levels of outdoor air pollution, but even bladder cancer may be increased, a finding that applies to all regions of the world.
In the past, scientists simply identified one source of air pollution as a carcinogen, but this time they put the whole “outdoor air pollution” in the hat
This recent report from the International Agency for Research on Cancer (IARC) specifically mentions PM2.5 particles. This fine particulate matter, which has a wide range of sources and complex composition, is now used as an indicator pollutant in more and more countries.
And as scholars have moved from ignoring it to taking it seriously, its average global concentration has evolved from less than 10 micrograms per cubic meter to about 100 micrograms per cubic meter.
Compared with inhalable particulate matter (PM10) with a particle size of less than 10 microns, this fine particulate matter stays in the atmosphere for a long time, is transported over long distances, carries a lot of toxic and harmful substances and can enter the bronchi and alveoli, and is “easy to invite God and difficult to send God”.
Unlike the large particles PM10 only in the upper respiratory tract “small fight”, when the human body inhaled a large number of fine particles, the respiratory organs can not filter, fine particles will not be polite in the human body “camp” –They can enter the bronchial tubes and alveoli directly and take the pollutants (including heavy metals, PAHs, etc.) with them to participate in the blood circulation system and human metabolism, and even make a trip to the olfactory axons of the brain.
The “outdoor polluted air” mentioned in the report is such a complex mixture of fine particles and various pollutants.
A recent paper published in the journal Environmental and Health Perspectives shows that the number of fine particles between 0.25 and 0.5 microns in size is particularly significant in relation to the health of the population, especially the risk of cardiovascular disease.
In the past, scientists have simply identified one source of air pollution as a carcinogen, such as exhaust from diesel internal combustion engines. This time, however, they put the whole “outdoor air pollution” into the hat.
But for environmental science professor Jinliang Zhang, the dangers of air pollution go far beyond this one hat: their deposition in the body can bring a greater risk of asthma, cardiovascular disease, birth defects and premature death, and of course, lung and bladder cancer can be properly added to the list at the moment.
In 2012, a report by the American Psychological Association said that dirty air is not good for the brain – it impairs cognitive abilities in children, puts adults at risk of cognitive decline, and may even lead to depression.
Children born to mothers who experience air pollution during pregnancy are more likely to grow up to experience concentration problems or symptoms such as anxiety and depression.
The IARC report sends a strong signal to the international community to take action without further delay
”Domestic research is rather fragmented, and we are not in a position to do large, many-year follow-ups like in Europe and the United States, and the results of such cohort studies are often very credible.” Referring to the conclusions of IARC this time, Zhang Jinliang noted that their main materials came from European and American scientific institutions, “so the main arguments you see mentioned in the report are based on studies made in the environment of Europe and the United States, in the case of PM2.5 values between 20 and 30.”
One of the main pieces of evidence for the IARC’s classification of outdoor polluted air as a carcinogen this time is a paper published in the top medical journal The Lancet during July of this year. It combined data from 17 cohort studies conducted within nine European countries and concluded that people exposed to outdoor polluted air are at greater risk of developing cancer, even in environments where air pollution levels are below the EU standard (25 micrograms per cubic meter).
The studies tracked nearly 320,000 people living in Europe, and over an average follow-up of 12.8 years, 2,095 participants eventually developed lung cancer.
The researchers found that even if PM2.5 was maintained at very low levels, the risk of lung cancer increased by 18 percent for every 5 micrograms of fine particles per cubic meter of air. The nitrogen oxide content of the air, or nearby traffic conditions, and cancer did not appear to be significantly linked.
Previously, the European Union had adopted the Ambient Air Quality Directive, expecting member states to keep the annual average index of PM2.5 in urban areas within 20 by 2015, while researchers at the Danish Cancer Society Center, who led the study, told the media very succinctly about their new findings: “The less PM2.5 the better, the more the worse “.
The main evidence in terms of animal experiments came from São Paulo, Brazil. The researchers injected particulate pollutants under the skin of mice, and similar to the results of other studies, the particulate matter posed a greater risk: the incidence of tumors at the injection site also increased.
The IARC director hopes that the majority of the world’s population may wake up when the entire “outdoor air pollution” category is classified as a carcinogen: “This report should send a strong signal to the international community to take action without further delay. “
That said, the actual air pollution situation, however, varies greatly from place to place.
Dr. Loomis told reporters that there are many proven ways to reduce air pollution, but the situation is different from country to country: “Comparing East Asia and Europe, the level, source and composition of air pollution are different, so different countries need to deal with it in different ways.”
He also explained this difference to France-based Euronews: the greatest concentrations of pollution are in Africa, East Asia and South Asia. But the big difference is that in Africa, the polluted air comes with the wind, mostly from respirable particles carried out by sand; while in Asia, the polluted air comes mainly from the burning of coal, as a result of the constant development of industry.
So, it is also possible to understand this data given by the International Agency for Research on Cancer – in 2010, 3.2 million people died prematurely worldwide because of exposure to air pollution, and another 223,000 died of lung cancer because of air pollution – of which More than half of them lived in East Asia.