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The impact of smog on health, don't use the data of the 1950s!

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(This article first appeared in Tencent News "Real" section) Currently on the domestic website, the problem of smog hazards can be described as cumbersome. For example, after entering "haze hazard" in Bing search, there are 280,000 related web pages. It is a pity that, whether it is a variety of encyclopedias or news reports of mainstream websites, when it comes to the hazards of smog, it is often used in qualitative language such as “a variety of diseases that can cause respiratory and cardiovascular systems”. Many articles The example of the London smog incident in the 1950s is still far behind the current state of public health research. This article briefly introduces some important research results in the field of air pollution and disease in recent years, and hopes to make a small contribution to the public's accurate understanding of the haze hazard.

I. Haze and respiratory diseases

The effect of smog on the respiratory system is that everyone has a personal experience, so the longest research history and the largest related research. As early as 1982, the American Oncology Association began a long-term follow-up of nearly 190,000 non-smoker Americans. The 26-year follow-up report published in 2008 showed a 15% increase in lung cancer mortality for every 10 μg/m3 increase in PM2.5 concentration. -27% [1]. A study conducted by Japan in the last century involving 63,000 people for 10 years (1974-1983) showed that lung cancer was increased by 10 units of PM2.5, sulfur dioxide (SO2) and nitrogen dioxide (NO2). Risks ranged from 17% to 24%, and the risk of pneumonia increased significantly [2]. A survey conducted in 29 cities in Europe in 2006 showed that for every 10 μg/m3 increase in PM10, deaths from respiratory diseases increased by 0.58% [3]. A 2009 study in the United States showed that even if PM2.5 only increased by 10μg/m3 for only two days, the prevalence of respiratory diseases would increase by 2.07% [4]. A study published in the authoritative medical journal Lancet Oncology, 2013, involving 9 European countries with a mean follow-up of 12.8 years for 310,000 people, shows that for every 5 μg/m3 increase in PM2.5, the risk of lung cancer increases. 18%, for every 10μg/m3 increase in PM10, the risk of lung cancer increased by 22%. The study also showed that the risk of lung cancer increased by 9% in residents living 100 meters near busy roads [5]. A few days ago, a respiratory department director of the Union Hospital said in an interview that "the impact of smog on chronic respiratory diseases is very clear." In fact, from the above research results, the effect of smog on the respiratory system is far more than Chronic diseases, but all kinds of significant harm from acute pneumonia, asthma to long-term tumors.

Second, smog and cardiovascular diseases

As another system highly associated with the respiratory system, the relationship between smog and cardiovascular disease is equally impressive. The first is the effect on blood pressure: At the beginning of this century, Korean researchers found that a short-term increase in total PM concentration of 10 μg/m3 resulted in an increase in blood pressure of 1-4 mmHg, and different types of air pollutants had different effects on blood pressure [6]. A study conducted in Mexico during the same period showed that pulmonary pressure in children born and living in areas with severe air pollution was significantly higher than that of peers living in air-tolerant areas, and high pulmonary artery pressure was a source of pulmonary heart disease. The main performance [7]. A Canadian study showed that an increase in PM2.5 concentration of 10 μg/m3 resulted in a 31% increase in the prevalence of congestive heart disease in women, a 22% increase in the prevalence of coronary heart disease, and a 21% increase in the risk of stroke. The impact is more pronounced [8]. Italian scientists analyzed 160,000 elderly patients hospitalized in 2001-2005 and air pollution during hospitalization. It was found that for every 10 μg/m3 increase in PM10, 1.4% of hospitalizations due to heart failure increased, and the number of hospitalized patients with coronary heart disease increased. 1.1%, a 1.0% increase in arrhythmia hospitalization [9]. A survey of 65,893 postmenopausal American women published in the 2007 authoritative medical journal New England Journal of Medicine found that long-term exposure to PM2.5 was significantly associated with risk of death from cardiovascular disease [10] (Figure 1 ).

Figure 1: PM2.5 concentration and risk of death from cardiovascular disease, A is the overall effect, B is the effect relationship between urban areas, and C is the effect relationship in urban areas (quoted from Kristin A. Miller et al. "Long- Term Exposure to Air Pollution and Incidence of Cardiovascular Events in Women").

An article published in the famous Journal of the American Medical Association (JAMA) in 2012 analyzed all studies involving air pollution and myocardial infarction at the time, and found that air pollution such as NO2, SO2 and PM2.5 in addition to ozone Substances, even short-term exposure (within 7 days), can increase the risk of coronary heart disease and myocardial infarction by 0.6%-4.5%. In 2013, the European Journal of Internal Medicine summarized a series of epidemiological studies in the field of cardiovascular diseases and found that both long-term and short-term exposure to PM2.5 can cause myocardial infarction, stroke, heart failure, and heart rhythm. A series of cardiovascular events such as dysfunction and venous thrombosis have increased [11].

Third, the impact of smog on cognitive function

If the effects of haze on the respiratory and cardiovascular systems are obvious, and the results of the study are only somehow confirmed by the numbers, then when the literature is consulted, it is found that "the haze damages cognitive function." "I have already had a lot of literature reports to shock me." A large number of studies have shown that exposure to air pollution in early childhood may have an impact on neurodevelopmental level, intelligence, language ability, memory, and attention. The most representative of these was a survey of nearly 10,000 children in six European countries from 1997 to 2008. It was found that exposure to air pollution during pregnancy significantly reduced children's neurobehavioral development, with NO2 exposure being the most important. The neurobehavioral development score decreased by 0.68 points for every 10 μg/m3 increase in NO2 during pregnancy [12]. A study of 2,715 7-10 year-old Spanish children showed that children who were frequently exposed to high levels of vehicle exhaust lag significantly behind working children in normal air conditions (Figure 2). ].

Figure 2. Relationship between air pollution and working memory. The upper solid line is the average score for children living in low-pollution areas, and the lower dotted line is the average score for children living in highly polluted areas. The horizontal axis is the number of investigations (cited by Jordi Sunyer et al. "Air pollution during pregnancy and childhood cognitive and psychomotor development: six European birth cohorts").

A 2010 survey of 15,973 elderly people in 866 counties in China found that air pollution index (API) was significantly associated with cognitive impairment in the elderly [14]. A study of nearly 20,000 older American women in 1995-2001 also found that older people living in more polluted areas experienced more cognitive decline during the same period of time than those living in normal air areas [ 15].

Fourth, the impact of smog on overall mortality and longevity

Regardless of which system of disease the smog causes, it will ultimately have an impact on population mortality and life expectancy. Fudan University conducted a study on 130,000 patients who died of coronary heart disease in nine major cities in China from 1996 to 2008 and air quality in the same period. It was found that when NO2, SO2 and PM2.5 increased by 10μg/m3 in 2 days, coronary heart disease The death toll will increase by 0.36%-1.30% [16]. A study published by the Chinese Academy of Sciences in 2014 on 85 cities and regions in China showed that for every 10 μg/m3 increase in SO2 concentration, a change in life expectancy of 0.28 years would occur [17]. Since the 1980s, the overall air quality in the United States has been getting better. The researchers analyzed the air quality changes and life expectancy of 545 counties from 2000 to 2007 and found that every 10μg/m3 of PM2.5 decreased. The life expectancy will increase by 0.35 years [18]. In addition to the above results, there are many studies that believe that air pollution is related to gastrointestinal system diseases and blood system diseases. For example, Denmark has analyzed the air pollution of 1967 leukemia patients and found that long-term nitrogen oxides (NOx) exposure is associated with an increased risk of acute myeloid leukemia [19]. However, due to the relatively small amount of evidence in these areas and the lack of large-scale research on the 10,000-level level, it is not specifically described here. Although the adverse effects of haze on health are so clear, there are still two points that need to be brought to the attention of readers to avoid misunderstanding: First, most of the studies cited in this paper are in the concentration of PM10 and PM2.5 not exceeding 100 μg/ Under the conditions of m3, therefore, the conclusions of these studies can be used in China if the concentration of pollutants in the current state is “explosive” and lasts for several weeks. How to extend is unknown, for example, we cannot Increasing 10μg/m3, life expectancy is reduced by 0.28 years"" simple calculation" "SO2 concentration per 100g/m3 increase


Life expectancy will be reduced by 2.8 years" (actual results may be more, perhaps less). Second, the role of confounding factors should be considered in the interpretation of the study, such as living near busy roads will lead to increased air pollution, but At the same time, it is also likely that the economic level of this group of people may be different from those living in clean areas (rich people often live in areas with better environment and lower commuting requirements), and the economic level is also an important factor affecting the quality of education for the next generation.

As medical workers, we need to understand the exact impact of long-term severe haze on health, but as an ordinary Chinese, we are not willing to see future research data from China.

references:

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