The impact of heavy haze on health needs to be scientifically defined

Core Tip: In the smog, what people want to find out most is: How much harm does the invisible and intangible particles in the air have, how to affect their health, and how to avoid this harm?

The faint smog enveloped the city. Beijing PM2.5 concentration measurements are very high today, with many areas exceeding 700 μg/m3. And this severely polluted air quality situation is difficult to improve in the next three days.

In the smog, what people want to find out most is: How much harm does the invisible and intangible particles in the air have, how to affect their health, and how to avoid such harm?

These questions are not without answers, but after chasing the answers deeper, you will find that the existing answers are not clear enough.

Pan Xiaochuan, a professor at the School of Public Health, Peking University School of Medicine, studied PM2.5 for many years. In December last year, a report written by him pointed out that if the air quality in Beijing, Shanghai, Guangzhou and Xi'an in 2012 did not improve compared with 2010, the number of “excess deaths” caused by PM2.5 pollution will reach 8,572. The economic losses brought by it will reach 6.8 billion yuan.

This data was misunderstood by many people as "PM2.5 kills 8,000 people." This is not the case.

Pan Xiaochuan told the China Youth Daily that his research did not find more than 8,000 dead, but was measured by the general method of environmental epidemiology. "We used data on mortality and pollutants over the past few years. Other variables are excluded. This is still a conservative estimate."

Are there variables that are difficult to count, causing people to find the wrong "killer"? Pan Xiaochuan said that because the ozone and black carbon in the air is difficult to count, it is impossible to completely rule out the impact of variables on the results.

In fact, most epidemiological data are inferred in a similar way. The purpose of these data is to provide an overview and to provide direction for decision-making as much as possible, but it does not allow people to have a glimpse of the truth, and it is even more difficult to know how the smog between a window and their physical functions have occurred.

Toxicological studies of PM2.5 attempt to find evidence at the micro level. In 2004, Professor Zhu Xi of the School of Environmental Science and Engineering of Peking University conducted a study on the cytotoxicity of dust particles on human lung fibroblasts. At the same time, the effects of these particles on alveolar macrophages in rats were also studied.

The above experiment collected PM10 and PM2.5 located beside the urban main traffic line in Beijing. After treating the particulate matter, it was applied to the cells at different concentrations for 24 hours. It was concluded that "when the concentration of (infected) reached 20 micrograms per milliliter, the (cell) mitochondrial succinate dehydrogenase activity decreased by 51.91% and 44.00%."

However, the concentration set in the laboratory is in micrograms per milliliter, and the current concentration of PM2.5 in air is measured in micrograms per cubic meter, which is quite different. People care, how does the laboratory environment interface with the faint yellow air in reality?

Zhu Xi told this reporter that epidemiology is "knowing it" and toxicology is trying to "know why it is." The zoology experiment is mainly to find out the cause, and the dose setting is only for observing the acute effect, and it is difficult to seamlessly interface with the actual.

In other words, these studies are currently unable to answer the most direct question: "In today's air, one person has to take out the door and bear the risk."

There is no choice for these suspended solids.

Song Guangsheng, director of the National Indoor Environment and Indoor Environmental Product Quality Supervision and Inspection Center, is an expert in indoor environment. He told reporters that compared with outdoor pollution, indoor PM2.5 can not be ignored, cooking fumes and smoking smoke will Inhalation of particulate matter in the room.

However, he is now in a "difficult" situation. "We usually recommend indoor ventilation in the winter, once in the afternoon and afternoon, to reduce indoor biological and chemical pollution. But now the situation is not good outside the window ... that is still, do not open the window for the time being."

If you can't avoid going out, is it necessary to wear a mask? Pan Xiaochuan told reporters that although the harm of PM2.5 can not be ignored, it is no match with the harm of smoking. "If you calculate by the same method, the number of people who die excessively due to smoking is much more than that of PM2.5." Come, there is no need to wear a mask when going out, and it is not a problem for healthy people to be exposed for an hour or two outdoors.

Environmental protection volunteer Liu Changfeng did not wear a mask. He has long been paying attention to PM2.5 spontaneously. In order to understand the exact data, he even held tests on his own instruments and was dubbed by the media as "I test the air for my motherland." Speaking of PM2.5, he is much more familiar than the general public. These days, when many people are entangled in smog, he is relatively calm. "Not so exaggerated. If you wear a mask and squeeze the nasal cavity, it will cause excessive inhalation of fine particles, but it will be bad for your body."

However, he insisted that his children stay at home and bought an air purifier.

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