The prevalence rate and the positive rate of children’ respiratory system symptoms and diseases in different city.
This chapter elaborates the source and ingredients of atmospheric pollutants, the microecology of respiratory tract in animals and humans and the effect of atmospheric pollution on it and thus clarifies the relationship between air pollution and microecology of the respiratory tract based on the experiments.
- atmospheric pollution
- respiratory tract
This chapter includes five aspects such as atmospheric pollution, the hazards of atmospheric pollution to the body, microecology of respiratory tract, atmospheric pollution and microecology of respiratory tract in humans and atmospheric pollution and microecology of respiratory tract in rats; this chapter describes the source of atmospheric pollution, the classification of atmospheric pollutants (particulates, sulfur oxides, nitrogen oxides, pollution by polycyclic aromatic hydrocarbons (PAHs)), acute and chronic influence of atmospheric pollution to the body, the composition and physiological function of microecology of respiratory tract and focuses on the effect of air pollution on the microecology of respiratory tract. The results of oropharyngeal flora detection in children and rats have shown that atmospheric pollution can cause increase in the detection rates and flora density of both normal flora and pathogenic bacteriatherefore resulting in microecology imbalance. Exposure to air pollutants for different length of time can lead to corresponding acute or chronic injury of the respiratory system. Compared with total suspended particles (TSP) and PM10, PM2.5 can stay for long time in atmosphere and has long conveying distance, so that it has more influence on the quality of atmospheric environment and human health.
2. Atmospheric pollution
2.1. Source of atmospheric pollution
The most principal hazardous substances in atmospheric pollution include sulfur oxides, nitrogen oxides, dust, hydrocarbons and carbon oxides. Sulfur oxides mainly come from the combustion of fossil fuels, such as petroleum, coal and natural gas. Nitrogen oxides mainly come from vehicle exhaust, including multiple substances, such as NO and NO2. Dust is the particulate whose diameter is generally 0.002–500 μm and mainly comes from the fuel combustion, solid crushing, sand storm and secondary hazardous substances, such as ozone and sulfuric acid mist, belonging to photochemical smog. The poisonous gases in industry, such as toluene and gasoline as well as heavily metals entering atmosphere such as mercury, chromium and zinc, would cause atmospheric pollution [1, 2].
Atmospheric pollution is caused by one or multiple kinds of pollutants in gaseousness, gas dispersoid, or particulate that exist in the atmosphere and it can cause harmful or abnormal effects to mankind and other organisms. The principal hazardous substances in atmospheric pollution include sulfur oxides, nitrogen oxides, dust, hydrocarbons and carbon oxides, etc. and atmospheric pollution has become a worldwide problem because of its wide source and large scope of influence.
The sources of atmospheric pollution mainly include fuel combustion, industrial production and transportation. The pollutants discharged by fuel combustion approximately account for 70% of total pollutants in atmosphere of China, 20% by industrial production and 10% by transportation. Among them, over 95% of pollutants discharged by fuel combustion come from coal burning; therefore, the main source of atmospheric pollution in China is the flue dust discharged from direct coal burning.
2.2. Classification of atmospheric pollution
According to their attributes, atmospheric pollution can be divided into three categories, i.e., chemical pollution, biological pollution and physical pollution. Among them, chemical pollution is the most diversified and it is the key point of atmospheric pollutants because of its wide scope of pollution. Chemical pollutants are discharged into atmosphere mainly in the form of waste gas. According to their physical states in atmosphere, they can be divided into gaseous and particulate states. Common gaseous atmospheric pollutants include SO2, O3, CO and NO2. The particulates closely related to hygiene include total suspended particles (TSP) and inhalable particulate (IP). TSP is the generic term of various particulates dispersed in the atmosphere in the state of gas dispersoid. The particle size of TSP is 0.1–100 μm and the toxic substances contained in them, such as As, Cd, Pb, Ni and polycyclic aromatic hydrocarbon, can change the activity and metabolic status of cell enzyme. IP or PM (10) means the particulates whose aerodynamic equivalent diameter (AD) are less than 10 μm and it is then generally divided into coarse particulates (2.5 μm < AD < 10 μm), fine particulates or PM2.5(AD ≤ 2.5 μm) and ultra-fine particulates (UFPs) (AD ≤ 0.1 μm) by the particle size (Figure 1). Coarse particulate is mainly produced by mechanical actions, but the latter two kinds of particulates mainly come from fuel combustion, including direct discharge after combustion and generation from gaseous pollutants through chemical transformation [1–4].
Atmospheric pollutants can be classified by different division methods, such as source, chemical component, particle size and indoor or outdoor environment. The pollutants directly discharged into the atmosphere are called primary pollutants and the pollutants produced after chemical reactions with other environmental substances are secondary pollutants. There are obvious correlations between them, but that is not always unchanged, since the lowered level of primary pollutants as precursor would not always automatically make the level of secondary pollutant correspondingly lower. For example, ozone (O3) is mainly generated by nitrogen oxides (NO
In the generally acknowledged atmospheric pollutants, the epidemiological links between particulates and population health effect endpoint is the closest. The quantitative hazard assessment of particulates on health has become one of the hot spots that received attention from international organizations in recent years, such as WHO and EU. It is stipulated by America that the mean daily value and mean annual value of IP (PM10) shall respectively be 0.15 and 0.05 mg/m3. It is stipulated in GB3095–1996 promulgated by China in 1996 that the secondary standard for the mean daily value of PM10 shall be 0.15 mg/m3 and the mean annual value shall be 0.10 mg/m3. In 1997, Environmental Protection Agency of the United States (US EPA) was the first to promulgate the PM2.5 standard and its mean daily value was strictly stipulated to be 0.065 mg/m3 and its mean annual value to be 0.015 mg/m3 [1–4].
The toxicity of particulates, both PM10 and PM2.5 can increase the risk of lung cancer. It is shown by the American research that sulfate, nitrates, hydrogen ion, carbon element, secondary organic compounds and transition metals are all concentrated on the fine particulates, but Ca, Al, Mg and Fe elements are mainly concentrated on coarse particulates and they have different impacts on the human body. The hazard of PM2.5 on the human body is greater than PM10, which has become a new target of policy for environmental air control. With the development of transportation and the increase of motor vehicles as well as the increasing disruption of environment, the pollution of PM2.5 gets more and more serious. It is found by researches that the ratio of atmospheric PM2.5 in TSP is increased year by year and 96% of the particulates that deposit in the lower respiratory tract are PM2.5. The PM2.5 in the urban atmosphere mainly comes from the exhaust of traffic waste gas (18–54%) and the secondary pollution of gas dispersoid (30–41%) [1–4].
2.2.2. Sulfur oxides
Researches on the relations between SO2 and the incidence risk of lung cancer. It is shown by epidemiological researches that SO2 is closely related to the incidence of lung cancer. It is shown by the analysis of the mortality rate of lung cancer in Qingdao by Hu Yan . that SO2 in the atmosphere of downtown Qingdao has certain correlations with the increase in the mortality rate of lung cancer. Chen Shijie et al.  utilized grey relativity model to calculate the mortality rate data for lung cancer of mass and the mean annual concentration data of SO2. It is shown by the results that the grey relativity between the mortality rate of lung cancer and the SO2 8 years ago is the greatest, thus the latent period of SO2 to cause lung cancer is 7 years. It is shown by the cohort research of 16,209 individuals in Norway that long-term exposure to SO2 is related to the risk of lung cancer. Through the data collected by American Cancer Society for 16 years and the data of risk factor for the cause of death of 500, 000 Americans, Turner et al. . found that SO2 in air is related to the total morbidity rate and mortality rate of lung cancer. Through the cohort research of 57,613 workers exposed to SO2 in pulp and papermaking industry in 12 countries, Moon et al.  found that the relative risk of lung cancer of the workers in the nonexposed group compared with those in the exposed group is 1.49 and its 95%
2.2.3. Nitrogen oxides (NO
Researches on the population epidemiology of nitrogen oxides: Through spatial geographical distribution map and Spearman rank correlation analysis to the death data of lung cancer in Jiangsu Province and to the air data of corresponding period, Lu et al.  found the positive correlation between the concentration of NO
2.2.4. Pollution of polycyclic aromatic hydrocarbon
3. The hazard of atmospheric pollution to the body
With the increase of population density and the development of modern industry in the city, the influence of atmospheric pollution on mankind gets more and more serious. It is shown by many epidemiological evidence that the diseases of respiratory system are related to the low quality of air. At present, about 600 million tons of atmospheric pollutants are discharged annually into air worldwide, which is the direct cause for the increased number of hospitalized patients and outpatient patients, the decreased attendance rate of students and the increased morbidity rate of allergy. Life and environment shall be a unity and the life existence of living bodies that must adapt to the internal and external environment, since the maladjustment between them would merely cause diseases or death. Life and environment must be a unity of opposites and they are inseparable. All organisms have the limit of adapting to the environment and anyone beyond the limit would lose life. Mankind is incessantly adapted to the environment and ceaselessly transforms the environment. Through the long-term repeated actions of low concentration of toxic and harmful pollutants in the environment on the body, chronic hazards would be incurred, which is caused by the sedimentation of poison itself in the human body or gradual accumulation of the tiny injuries to the body. At present, the world is confronted with three major environmental problems, i.e., destruction of ozone layer, acid precipitation and greenhouse effects, which are all related to the atmospheric pollution. The reason for the destruction of ozone layer is the impact of certain compounds, mainly including Freon. Under the photochemical action of ultraviolet ray, the harmful compounds in atmosphere might produce the active compounds to destruct the ozone layer, such as NO, NO2, HO2, Cl− and ClO−. The hole would be formed at the ozone layer after destruction and the function of ozone layer to block and absorb ultraviolet ray would be weakened. Excessive contacts of population with ultraviolet ray might cause corresponding diseases [11–14].
The combustion of large quantities of fuels would produce large quantities of CO, CO2, SO2, and NO
Human and environment are closely related and the atmospheric pollution incurred by the progress of industrial civilization has substantial impacts on mankind. It is shown by researches of environmental epidemiology that from slight symptom of respiratory system to the increase in outpatient number of cardiopulmonary diseases and mortality rate, all are closely related to atmospheric pollution. As estimated by World Health Organization (WHO), annual death of 800 thousand people and 4.6 million disability adjusted life expectancy (DALY) worldwide are related to urban atmospheric pollution. In 1775, British doctor Pott posed the hypothesis of flue gas pollution to be carcinogenic and in the mid-twentieth century, the occurrence of London smog incidents made people extensively pay attention to the health hazard of atmospheric pollution. However, its influence on health has not yet been fully recognized by mankind. The health hazard caused by atmospheric pollution has become a problem worldwide and it has caught the attention of multitudinous domestic and foreign scholars. Since the health effect is complicated, it is usually the results of multiple factors through comprehensive actions. Thus, it is very difficult to draw the explicit conclusion of a certain factor that causes a certain result. The influence of atmospheric pollution on health is mainly divided into acute influence and chronic influence [12–15].
3.1. Acute influence
The acute influence of atmospheric pollution on humans includes direct actions and indirect actions. For example, acute intoxication of certain poison belongs to direct actions; indirect actions can aggravate the deterioration of respiratory system or heart diseases, etc. and thus accelerate death of patients. There are a few domestic reports on the acute influence of atmospheric pollution on human body and it is pointed by some scholars that when the mean daily concentration of each index of atmospheric pollutants does not exceed the health standard but instantaneous discharge surpasses the maximum allowable concentration for single exposure, the importance of its influence on health might exceed the average day concentration. Therefore, the acute hazard of atmospheric pollution could be more concealed and its severity might be easily neglected by people [16–18].
3.2. Chronic influence
The chronic influence of atmospheric pollution on human body is a kind of composite action, which is manifested in multiple aspects. The early hazard of low concentration atmospheric pollution to human body is usually not fully manifested in the form of disease. Instead, it is mostly manifested as the preliminary effect of diseases. It is shown in the immunologic dysfunction of body and the change in blood and circulation system, which might induce and promote the incidence of allergic diseases, respiration system diseases and other diseases in human body. At the time of performing the epidemiological research, in order to reduce the influence of smoking and occupational factors, etc., children are preferably selected as the investigation objectives [13, 19–21].
From the metabolic process of body, it can be seen that human body and environment are closely related. Human body performs substance exchange with the surrounding environment through metabolism and dynamic equilibrium is normally kept between the substances in environment and human body. In case of abnormal changes in environment, normal physiological functions of human body would be affected with varying degrees and human body is capable to adjust own physiological functions, so as to adapt to the incessantly changing environment. That normal physiological adjustment function of adapting to the environmental changes is formed by mankind in the long-term development process. If the abnormal changes in environment are within a certain limit, human body can adapt to them. If the abnormal changes of environment surpass the limit of normal physiological adjustment of human body, an anomaly might incur in certain functions and structures of the human body and even in pathological changes. That kind of environmental factor that might incur pathological changes in human body is called environmental pathogenic factor. The diseases of mankind are mostly caused by biological, physical and chemical pathogenic factors. The substances that cause environment pollution include chemical factors, biological factors and physical factors, etc. and they might become pathogenic factors when they reach a certain extent [19–21].
The contents of pollutants in environment are usually very few under many circumstances, after mankind lives in that kind of low concentration polluted environment for several months, several years and even tens of years, chronic hazards to the body might be gradually incurred to cause diseases. Disease is a process of pathological changes in the function, metabolism and morphology of body under the actions of pathogenic factors. Human body has certain compensatory ability against the functional hazard caused by disease factors. Some changes are compensatory and some changes are traumatic in the developing process of diseases and both changes coexist. When the compensatory action is stronger, body can still keep relative stability and the clinical symptoms of diseases would temporarily not emerge. When the pathogenic factors stop acting, body shall develop to restore health. But the compensatory ability is restricted. If the pathogenic factors continue to act, the compensatory functions would gradually be obstructed and the body will manifest unique clinical symptoms and signs of various diseases. The reacting process of human body to environmental pathogenic factors is shown in Figure 3.
The incidence and development of disease is generally divided into the latent period (without clinical manifestation), prodromal period (with slight general discomfort), obvious clinical symptom period (when typical symptoms of the certain disease emerge) and prognostic period (restoring health or deterioration to death). Under the circumstance of acute intoxication, the first two periods of disease might be very short and obvious clinical symptoms and signs might appear very soon. Under long-term micro action of pathogenic factors (such as certain chemical substances), the first two periods of disease can be considerably long. Patients might have no obvious clinical symptoms and signs and instead, they might look healthy. But under continued actions of pathogenic factors, obvious clinical symptoms and signs might emerge. In addition, its resistance to other pathogenic factors (such as bacteria and virus) would decrease and therefore, that kind of person is in the latent period or compensatory state. The stage during which injuries have already occurred by a certain hazard but the clinical symptoms have temporarily not emerged, shall be deemed as the early period of disease (clinical prophase or subclinical state) [19–21].
It is shown by researches that 80–90% of mankind cancer is related to environmental factors, among which 90% are caused by chemical factors and 5% are caused by radioactive factor. But the chemical substances and radioactive substances within the contact scope of mankind mainly come from environmental pollution.
4. Microecology of respiratory tract
The respiratory system of mankind is composed of the following organs: Nose, pharynx, throat, trachea, bronchus and lung. Nose, pharynx and throat are the upper respiratory tract and trachea and bronchus are the lower respiratory tract. Lung is the place where gas exchange is performed. Other organs are the passages of gas and are generically called respiratory tract. Like the permanent planting of flora in other systems or parts of the body, that in the respiratory tract observes a certain regular pattern. For the microorganisms that exist at each part of human respiratory tract, their category and quantity are relatively stable under normal circumstances. Bacteria that are often separable from healthy human body mainly include alpha streptococcus, Neisseria Trevisan, Hemophilia, oral myxococcus, staphylococcus, corynebacteria and a certain anaerobe. Relatively single population of alpha streptococcus mainly lives on the surface of epithelial cells at oral pharynx and oropharynx mucosa. Saliva contains such immunological materials as immune globulin and lysozyme. As a result, as the long-term permanently planted bacteria at oral pharynx, alpha streptococcus has stronger immunity than the crossing bacteria. Alpha streptococcus normally accounts for over 90% of bacteria at oral pharynx [22–24].
The microenvironment of each part of respiratory tract is very complicated. Besides the ecological space of body and the process of its gas exchange with outside environment, which constitute important components of the microscopic environment of respiratory tract, microbiocoenosis (including bacteria, virus, mycoplasma and actinomycete, etc.) inevitably intervenes soon after the birth of individuals, since the passage is open to the exterior. They shall parasitize in different ecological niches of respiratory tract and they shall not be pathogenic under health. Some can be combined with the receptors on the cell surface, so as to obstruct the invasion of the pathogenic microorganisms that enter later, playing the role of a barrier. The microbiocoenosis at ecological niches of human body, such as the upper respiratory tract and trachea, has relationship of mutual synergia and normal commensal flora can help host to resist the invasion of pathogenic microbes. That protective mechanism includes: (i) aiming at the competition of the same nutrient, disturbing the nutrition of attacking pathogenic bacteria; (ii) aiming at the affinity of the same category of cells, i.e., the commensal bacterium that has relatively big binding force to the receptors on the cells of the host, disturbing the attachment effect of attacking pathogenic bacteria; (iii) through irritating the host to produce immune factor, aiming at the attacking bacteria with “cross” antigen, exerting adverse influences to make the pathogenic bacteria not be permanently planted without difficulty; (iv) through producing bacteriocin or antibiotic, specifically or not disturbing the colonization action of identical or relevant sensitive microorganisms [22–24].
Oral pharynx is the passage to link oral cavity and nasopharynx with the lower respiratory tract and esophagus. Since it is connected with the external environment, it is a physiological part where many bacteria infringe the lower respiratory tract and lung to cause infection. About the general regular patterns for the cognition to microecology of human body, the core population combination that parasitizes at the oral pharynx of a healthy body shall fluctuate within harmonious physiological scope and they shall compose an important microbial barrier for oral pharynx, so as to resist the change in the external environment. The pathogenic bacteria would firstly be permanently planted at the mucosa part represented by oral pharynx, such as mouth and nasopharynx. Then it would reach the lower respiratory tract and lung and would further cause corresponding pathological reaction of the body. Oral pharynx has a high content of organic matter and rich nutrition and is exposed in very complicated microbial environment. Thus it has many opportunities to contact various bacteria. But the categories of bacteria that live at oral pharynx is actually very limited and the total biomass of bacteria is only moderate.
5. Research examples: atmospheric pollution and microecology of respiratory tract in human
In order to explore the early harmful effects of the atmospheric pollution on human health and screen sensible markers, children of school-age who are the susceptible population to the atmospheric pollution are selected in our studies. And the researches were performed in different polluted zones with the different extent of the atmospheric pollution of three cities in the northeast of China, including Benxi, Shenyang and Dalian. Measurement and multiple-analysis were performed to analyze the relationship between the atmospheric pollution and the microecology of the upper respiratory tract.
5.1. The influence of atmospheric pollution on the symptoms and diseases of children’s respiratory system
Since the circumstances of air pollution in the three cities are difficult, contrast analysis was performed on the health status of the respiratory system of children in the three cities and the children in the contrast regions, so as to have an in-depth understanding of the influence that atmospheric pollution might produce to the body. By comparison of the three cities, children from Benxi and Shenyang are high in the positive rate of the general inflammatory symptoms and diseases of the respiratory system (such as cough, expectoration, sustained cough, sustained cough with expectoration, pneumonia, etc.), but the rate is relatively low in Dalian due to the more serious atmospheric pollution in Benxi and Shenyang (Table 1). Significant differences are found in the disease and incidence circumstance of the respiratory system among children in three cities (
|Benxi region||Shenyang region||Dalian region||Control|
|Cough||58.6 (3169)||59.5 (3500)||43.6 (1719)||44.1 (947)|
|Persistent cough||4.0 (216)||4.2 (246)||2.2 (87)||1.9 (40)|
|Expectoration||36.0 (1947)||37.4 (2198)||28.1 (1108)||26.8 (575)|
|Persistent cough and expectoration||2.4 (127)||2.6 (151)||1.1 (43)||1.2 (25)|
|Wheezing||7.3 (396)||1.4 (82)||0||1.4 (29)|
|Respite||4.5 (241)||2.2 (132)||2.5 (100)||1.4 (29)|
|Bronchitis||10.2 (550)||17.3 (1019)||22. 5 (887)||9.9 (211)|
|Asthmatic bronchitis inflammation||1.7 (94)||3.3 (195)||5.3 (210)||2.0 (43)|
|Pneumonia||9.1 (494)||22.1 (1297)||17.5 (692)||11.6 (246)|
|Eczema||8.9 (479)||12.1 (710)||7.2 (282)||7.5 (159)|
|Asthma||2.2 (121)||6.1 (359)||10.3 (407)||5.0 (106)|
|Urticaria||5.8 (314)||7.8 (457)||5.0 (196)||5.5 (116)|
|Allergic rhinitis||2.0 (106)||3.7 (217)||2.6 (103)||2.2 (46)|
Through the investigations to the symptoms and diseases of the respiratory system of 18,000 children in different polluted zones of different cities, it is shown by the analysis of the investigation that the extent of atmospheric pollution is positively related to various symptoms and diseases of respiratory system. In the analysis to each kind of symptoms and diseases, it is all selected into the equation under the condition of
5.2. The influence of atmospheric pollution on flora of the respiratory tract
According to the atmospheric monitoring data and urban function zoning of Shenyang, heavily polluted regions and light polluted regions are selected (Table 2). By means of the cluster sampling, samples of 40 and 50 children (half boys and half girls) aged 6–8 from different regions were selected respectively in 2000, while samples of 40 and 40 children were selected respectively in 2002. They were required not to use antibiotic drugs in the past 3 months. The qualitative location and quantitative analysis was performed to the flora status at the upper respiratory tract of children in the heavily polluted regions and contrast regions, so as to explore the influence of atmospheric pollution on microecology of the respiratory tract.
|TSP ± SD||SO2 ± SD||NO|
|Heavily polluted region||0.432 ± 0.097||0.169 ± 0.075||0.089 ± 0.021|
|Light polluted region||0.190 ± 0.041||0.012 ± 0.041||0.019 ± 0.0581|
Normal flora at oral pharynx is the natural barrier for the body. If such barrier is destructed by harmful factors, the flora would be imbalanced in quantity and category. As a result, the ability of the defense barrier would decline, exogenous pathogenic bacteria would intrude, or endogenous conditions would cause massive multiplication of pathogenic bacteria to incur infection. It is shown by our research that the density of the aerobic and anaerobic bacteria at oral pharynx of children in the seriously polluted air regions is higher than that of the light polluted regions and the abnormal flora also emerged, showing status of the excessive growth of flora at pharynx of children in the heavily polluted regions (Table 3). It is also shown that the detection rate of the conditional pathogenic bacteria of children in the heavily polluted regions was higher than that of the contrast regions. Permanent colonization of the pathogenic bacteria also emerged at oral pharynx of children in the heavily polluted regions, such as beta streptococcus, Klebsiella pneumonia, Serratia liquefaciens and Pseudomonas maltophilia (Table 4). The mutual antagonism and mutual restriction objectively exist in the microbes and this antagonism mainly comes from the microbial community. If the community is destructed, it would be favorable for the translocation of alien microbes and the multiplication of the pathogenic bacteria. It is shown by the research studies that the atmospheric pollution can cause the changes in the microbial community at oral pharynx of the body. Therefore, the atmospheric pollutants as exogenous factors have caused the destruction to the microecology balance of the upper respiratory tract. It is shown by the research that the incidence rate of the chronic inflammation at the upper respiratory tract and the incidence rate of chronic bronchitis of pupils in the heavily polluted regions are both higher than that of the light polluted regions (Tables 5 and 6), which can be attributed to the microecology imbalance at pharynx of the upper respiratory tract caused by the atmospheric pollution.
|Aerobic||Anaerobic||Total number||Amount(lgX ± SD)|
|Detectable number||Amount||Detectable number||Amount|
|763||2.883 ± 0.245*||837||2.923 ± 0.255*||1600||3.147 ± 0.260*|
|546||2.737 ± 0.926**||321||2.507 ± 0.050**||867||2.899 ± 0.194**|
|Bacterial species||Heavily polluted region (||Control (|
|Detection number||Detection rate (%)||Detection number||Detection rate (%)|
|Group D streptococci||6||15.0||5||10.0|
|Propionic acid bacteria||2||5.0||2||4.0|
|Cough||Persistent cough||Expectoration||Cough and expectoration||Persistent cough and expectoration||Wheezing||Respite|
|Sixth grade||61.7(586)3||5.9(56)3||38.7(367) 3||34.5(327)3||3.9(37)2||1.3(12)||2.1(20)|
|Bronchitis||Asthmatic bronchitis||Pneumonia||Asthma||Eczema||Urticaria||Allergic rhinitis|
It is shown by the dynamic analysis for 2 years that the detectable rate of alpha streptococcus at oral pharynx of children in the heavily polluted regions is lower than that of the contrast regions and the difference is significant (Table 4). Alpha streptococcus is the normal flora at the pharynx mucosa and it can be antagonistic against the abnormally permanent planting of the certain pathogenic bacteria, playing the role of a barrier. The reduction in the alpha streptococcus of children in the heavily polluted regions would certainly decrease the protective effects of the pharynx barrier and would increase the susceptibility to infection. It is considered by some scholars that alpha streptococcus can be taken as the probiotics for the upper respiratory tract. It can play a role in preventing and treating the infection of the upper respiratory tract by means of biological oxygen capture, flora adjustment and biological antagonism, which is consistent with our research results. It is also shown by this research that atmospheric pollution can cause the reduction of alpha streptococcus and further cause the increase of other abnormal flora. As a result, the infection of the respiratory tract might be increased. Therefore, we consider that alpha streptococcus can be used as one of the probiotics for the upper respiratory tract and it needs to be further developed as a microbial preparation, so as to prevent and treat infection of the upper respiratory tract and maintain the microecology balance.
6. Atmospheric pollution and microecology of respiratory tract in rats
To explore the regulation mechanisms of air pollution-related molecules and demonstrate the effects of air pollutants on the microecology of the respiratory tract, Wistar rats were used to expose to simulated real atmospheric pollution. It is beneficial to provide theoretical basis for the influence of air pollutants to the health of human body and the prevention and control of atmospheric pollution .
6.1. The influence of total suspended particulate (TSP) to the respiratory tract flora of rats
The relationships between normal microbiota and the host include ecosystems, biomes, species and individuals. Normal microbiota are divided into origin flora and foreign flora. The origin flora has more obvious physiological function if they come in contact with the host tissue cells closely, therefore providing more protection to the host and vice versa. Microecological balance is the ecological balance at the cellular level and molecular level, including microorganisms and host aspects. Normal microbiota of local ecological balance have obvious biological antagonist action to the pathogenic bacteria. Microecological imbalance will occur when this balance is damaged or influenced by external environmental factors.
From the ecological perspective, the normal flora of pharynx is the natural protective barrier. If the bacterial flora imbalance in quantity and types occur when the barrier suffers from the damage of harmful factors, the defensive barrier will break; therefore, the invading exogenous pathogen or some kind of endogenous bacteria will multiply and cause infection.
6.1.1. The influence of TSP to the bacterial species of respiratory tract of rats
TSP was collected continuously at a flow rate of 1000 l/min from areas of coal burning, traffic congestion in Shenyang city (China) during heating season and made into suspension by ultrasonic oscillation. The aerobic and anaerobic bacteria on the oropharynx of Wistar rats were analyzed before or after exposure to TSP. The results are shown in Table 7.
|Bacterial species||No TSP exposure(||TSP exposure(|
|Rats number||Detection rate||Rats number||Detection rate|
|Group A ||31||39.7||33||49.3|
|Group||Aerobic bacteria||Anaerobic bacteria||Average bacterial density|
|No TSP exposure||78||2.4111 ± 0.5868||2.5983 ± 0.4850||2.5047 ± 0.5447|
|TSP exposure||67||2.3353 ± 0.6566||2.4039 ± 0.61787||2.3696 ± 0.6361|
Normal flora plays an important role for maintaining ecological balance and stable internal environment. So many microaerobic, aerobic and anaerobic bacteria colonize in the upper respiratory tract of healthy people including 21 genera and 200 species of bacteria. The normal flora of respiratory tract are affected by the normal flora on the oropharynx because of the anatomic relationship. Compared with the control group, the detection rates of aerobic and anaerobic bacteria had no significant difference after low, medium and high concentration of TSP exposure because of the acute toxicity experiment with short time but large dose of TSP exposure. The changes of microbiocenosis in respiratory tract affected by air pollution are gradual, there will be more apparent changes after long-time exposure to pollutants eventually.
6.1.2. The influence of TSP to the density of bacteria in the respiratory tract of rats
The first step of bacterial colonization is adhesion. Similar to other biological cells, the bacterial proteins can be ionized into positively-charged amino (−NH+) and negatively charged carboxyl (−COO−) in solution and the degree of ionization is related to the pH of the environment. Negatively charged bacteria mainly exist in the alkaline solution and vice versa. The isoelectric point of gram-positive bacteria is pH 2–3 and the isoelectric point of gram-negative bacteria is pH 4–5; therefore, all the bacteria are negatively charged in neutral or weak alkaline medium with pH 7.2–7.6 and the gram-positive bacteria contain much more negative charges than gram-negative bacteria. For charge dependence, the bacterial adhesion increases with the pH of the environment. Moreover, the damage of host immune defense (such as malnutrition, basic disease, etc.) also can provide conditions for bacterial adhesion. However, there is mutual constraint relationship among bacterial flora such as space competition and nutrient competition.
The density of bacteria on the oropharynx of rats before or after TSP exposure was determined and the results are shown in Tables 8 and 9 and Figure 4. There was no significant difference in the bacterial density of aerobe flora, however, the density of anaerobic bacteria flora was markedly reduced (
|Group||Aerobic bacteria||Anaerobic bacteria||Average bacterial density|
|Control||18||2.2531 ± 0.7952||2.2922 ± 0.6948||2.2531 ± 0.7837|
|Low concentration||16||2.4139 ± 0.4964||2.4936 ± 0.4958||2.4537 ± 0.4706|
|Middle concentration||18||2.3190 ± 0.7240||2.5295 ± 0.7411||2.4243 ± 0.7299|
|High concentration||15||2.3698 ± 0.5890||2.2915 ± 0.5143||2.3306 ± 0.5448|
6.1.3. The influence of TSP concentration to the flora of respiratory tract of rats
Normal flora is influenced by various aspects especially the physiological functions and the pathological features of the host, so that, different groups of rats are used to explore the relationship between the density of aerobic and anaerobic bacterial flora and the concentration exposed to TSP and the results are shown in Table 10 and Figure 5.
Compared with control group, there was no significant difference in the bacterial quantity (Table 16), however, the quantity of aerobic bacteria fluctuated up and down with different dose of TSP exposure, the quantity of anaerobic bacteria was increased related to the dose of TSP exposure, but decreased in high concentration group (
|Aerobic bacterial species||No TSP exposure||TSP exposure|
|8||1.1899 ± 0.8867||0.8677 ± 0.8393|
|Diphtheroid bacillus||2||2.6276 ± 0.2129||1.8891 ± 0.5826|
|Group A ||15||2.2335 ± 0.3932||2.3379 ± 0.4941|
|2||2.2516 ± 0.6799||1.6901 ± 0.3012|
|2||2.8037 ± 0.2129||1.6901 ± 0.5502|
|9||1.9036 ± 0.7001||2.0308 ± 0.2370|
|Bacterial species||No PM10 exposure||PM10 exposure %||χ2|
|Group A ||18||38.3||15||31.9||0.187||0.666|
|Group||Aerobic bacteria (||Anaerobic bacteria (||Total bacteria (|
|No TSP exposure||331.2 ± 3.5||177.3 ± 2.1||601.9 ± 1.9|
|TSP exposure||452.3 ± 2.9||251.8 ± 2.214||796.5 ± 1.8|
|Group||Aerobic bacteria||Anaerobic bacteria||Total bacteria|
|Control||12||241.3 ± 8.1||177.0 ± 2.9||630.2 ± 2.6|
|1st day||12||854.9 ± 1.3*||288.9 ± 1.9||1011.8 ± 1.5|
|7th day||11||164.6 ± 4.0||334.0 ± 2.3||627.3 ± 1.8|
|30th day||12||581.7 ± 1.815||222.1 ± 1.9||865.2 ± 1.5|
|Bacterial species||No PM2.5 exposure||PM2.5 exposure|
|Number of rats||Detection rate||Number of rats||Detection rate|
The colonization of bacteria is influenced by the host factors and the normal microbiota. Tension of the mucous membrane of the host, cilia movement and various discharge are important factors affecting bacteria to colonize. Normal microbiota members mainly come from anaerobic bacteria, especially the obligate anaerobe. Normal flora is an important factor in protecting human health. The results confirmed that air pollution can cause changes in the microecological condition of respiratory tract. Anaerobic bacteria on the oropharynx are the important biological barrier to resist external environmental change. Therefore, when the concentration of air pollutants is not very high, the quantity of anaerobic bacteria increases to maintain the ecological balance and prevent invading bacteria from colonizing. However, when the concentration of air pollutants is very high, the quantity of anaerobic bacteria decreases to result to the microecological imbalance in respiratory tract. Thus, it is easy for pathogenic bacteria and intestinal bacteria to colonize.
6.1.4. The changes of flora in the upper respiratory tract of rats before or after TSP exposure
Compared with no TSP exposure, there was no significant difference in the bacterial density of aerobe flora after TSP exposure (Table 11). In the aerobic bacteria, the detection rate of group A Streptococcus increased after TSP exposure (
6.2. The influence of PM10 to the respiratory tract flora of rats
Particulate matter less than 10 μm in diameter (PM10) was collected using low flow of PM10 air sampling instrument and glass fiber filter film with 55 mm diameter from areas of coal burning in winter heating season, traffic and life pollution area in Shenyang city (China). Wistar rats were used as a model to analyze the changes of flora on the oropharynx before or after exposure to PM10. The results are shown in Tables 13–15.
6.2.1. The influence of PM10 to the detection rate of respiratory tract flora of rats
Compared with no PM10 exposure, the detection rate of
6.2.2. The influence of PM10 to the density of respiratory tract flora of rats
After PM10 exposure, the total bacterial content and the density of anaerobic flora on the oropharynx of rats were significantly higher than that before PM10 exposure (
6.2.3. The changes of flora density in the upper respiratory tract of rats before or after PM10 exposure
Compared with no PM10 exposure, the density of peptostreptococcus and
6.2.4. The changes of flora density in the upper respiratory tract of rats at different time after PM10 exposure
The density of aerobic flora on the oropharynx of rats on the first day after PM10 exposure was significantly higher than that in control group (
The results of present study showed that if the microecological balance was affected by some abnormal interference and destruction, there would be quantitative, qualitative or positioning changes in microbial population; therefore, the function of microbial biological barrier was weakened, so that some physiologic microbes became pathological bacteria. The results of this study showed that the detection rates of
The results of Wistar rat animal model of air pollution showed that after PM10 exposure, the density of anaerobic flora was significantly higher than that before PM10 exposure in the same rats (
The results of Figure 8 showed that the density of aerobic flora on the oropharynx of rats on the first day after PM10 exposure was significantly higher than that in control group, while it decreased on 7th day but increased obviously on 30th day after PM10 exposure (
Infection is a process in which microbe, host and environment interact with each other. Under the conditions of microecological balance, normal flora is harmless and beneficial to the host, however, the quantitative, qualitative, or positioning changes of normal flora will lead to infection under the condition of microecological imbalance. The results of our present experiments indicated that the density change of bacterial flora could act as a sensitive indicator of air pollution effecting on human body. Air pollution could cause microecological imbalance in the respiratory tract of human body, furthermore, lead to the infection of respiratory tract and other respiratory diseases.
6.3. The influence of PM2.5 to the respiratory tract flora of rats
Particulate matter less than 2.5 μm in diameter (PM2.5) was collected using portable air sampling instrument and glass fiber filter film with 47 mm diameter from areas of coal burning in winter heating season and the traffic downtown area in Shenyang city (China). Wistar rats were used as model to analyze the changes of the respiratory tract flora on the oropharynx before or after exposure to PM2.5. The results are shown in Figures 8 and 9.
6.3.1. The influence of PM2.5 to the detection rate of respiratory tract flora on the oropharynx of rats
Compared with no PM2.5 exposure, the detection rates of Cellulomonas/Mycobacterium,
6.3.2. The influence of PM2.5 to the density of respiratory tract flora on the oropharynx of rats
Compared with the results before PM2.5 exposure, the density of aerobic and anaerobic bacteria as well as the total population of bacteria significantly increased (P < 0.01) (Table 17). In the aerobic bacteria, the density of
6.3.3. The changes of flora density on the oropharynx of rats at different time after PM2.5 exposure
Compared with the results before PM2.5 exposure, the density of aerobic bacteria and the total population of bacteria increased significantly on 1st day (
On the basis of TSP and PM10, the impact of PM2.5 on respiratory tract micro ecology of rats was mainly focused on. In the research, the density of bacteria and the change of bacterial population were analyzed and the results showed that the detection rate of bacteria and bacterial amount especially aerobic bacteria increased significantly after PM2.5 exposure. The density of aerobic bacteria on the oropharynx of rats fluctuated over time on compensated and decompensated states, which increased significantly on 1st day but reduced significantly on 7th day while it increased obviously on 30th day after PM2.5 exposure. The total bacterial amount also showed the same trend, the density of most aerobic and anaerobic bacteria was higher than that before PM2.5 exposure and some genera were detected after PM2.5 exposure. All the results showed that PM2.5 could change the microecology on the oropharynx of rats to microecological imbalance. Compared to previous experimental results of PM10, the pathogenic bacteria of group B
Air pollution caused destruction of microecological balance in upper respiratory tract. The amounts of oropharyngeal aerobic and anaerobic bacteria were higher in children from heavily polluted area than those lightly polluted area. The detection rate of conditional pathogenic bacteria in children from heavily polluted area is higher than that in the control area. After 2 years of dynamic analysis, the detection rate of alpha streptococcus in children from heavily polluted area was lower than that in the control area and the difference was significant. Reduction of alpha streptococcus is bound to decrease the protective effect of the pharynx barrier, but increase susceptibility to infection.
Animal model of atmospheric pollutants was used to analyze the flora on the oropharynx of Wistar rats. The results showed that
After air pollutants exposure, the density of aerobic bacteria on the oropharynx of rats showed no significant change, however, the quantity of anaerobic bacteria decreased significantly and had significant decrease in trend over time. The average density of bacteria reduced with significant difference over time. The density of bacteroides and eubacterium of anaerobic bacteria were significantly reduced on the oropharynx of rats after air pollutants exposure compared with the results before air pollutants exposure. These results showed that air pollutants led to a decrease in respiratory total biomass and anaerobic bacteria and therefore declined the resistance of anaerobic bacteria, causing dysbacteriosis and colonization of pathogenic bacteria, which strongly proved that the anaerobic bacteria in normal flora played an important role in terms of colonization resistance.
The quantity of aerobic and anaerobic bacteria on the oropharynx of rats had no significant change with air pollutants but fluctuated with the concentration of air pollutants. The quantity of anaerobic bacteria on the oropharynx of rats had a downward trend in a high dose group (Figure 8). The density of Neisseria in aerobic bacteria increased significantly in high concentration group, however, the density of Veillonella in anaerobic bacteria reduced significantly. These results showed that the pathogenic and potential pathogenic bacteria were easier to colonize with the increasing concentration of air pollutants, but the quantity of total bacteria had no obvious change, which confirmed that the bacteria on the oropharynx of rats fluctuated within a certain range under certain conditions.
Air pollution could cause ecological imbalance and damage to the micro communities on the respiratory tract which led to the content of normal flora especially anaerobic bacteria decrease; therefore, the pathogenic bacteria colonized easily and caused respiratory diseases.
Gautam S, Yadav A, Tsai CJ, Kumar PA. A review on recent progress in observations, sources, classification and regulations of PM2.5 in Asian environments. Environ Sci Pollut Res Int. 2016; 23(21):21165–21175.
Liu Z, Wang Y, Hu B, Ji D, Zhang J, Wu F, Wan X, Wang Y. Source appointment of fine particle number and volume concentration during severe haze pollution in Beijing in January 2013. Environ Sci Pollut Res Int. 2016; 23(7):6845–6860.
Park SU, Lee IH, Joo SJ. Spatial and temporal distributions of aerosol concentrations and depositions in Asia during the year 2010. Sci Total Environ. 2016; 542 (Pt A):210–222.
Paraskevopoulou D, Liakakou E, Gerasopoulos E, Mihalopoulos N. Sources of atmospheric aerosol from long-term measurements (5 years) of chemical composition in Athens, Greece. Sci Total Environ. 2015; 527–528:165–178.
Hu Y. Evaluation on effects of Qingdao air pollution on economic loss of human health. Chin J Public Health. 2003; 19(8):940–941.
Chen S, Li X, Zhou L. Quantitative study by grey system on the latent period of lung cancer induced by air pollutants. Chin J Epidemiol. 2003; 24(3):233–235.
Turner MC, Krewski D, Chen Y, Pope CA 3rd, Gapstur SM, Thun MJ. Radon and nonrespiratory mortality in the American Cancer Society cohort. Am J Epidemiol. 2012; 176(9):808–814.
Moon EK, Son M, Jin YW, Park S, Lee WJ. Variations of lung cancer risk from asbestos exposure: impact on estimation of population attributable fraction. Ind Health. 2013; 1(1):128–33.
Lu Y, Hu X, Zhao J, Wang P, Qin Y, Wu M. The geographic information system of air pollution and the mortality of lung cancer in Jiangsu Province. China Cancer. 2003; 12(7):374–377.
Nyberg F, Gustavsson P, Järup L, Bellander T, Berglind N, Jakobsson R, Pershagen. Urban air pollution and lung cancer in Stockholm. Epidemiology. 2000;11(5):487–495.
Ma M, Li S, Jin H, Zhang Y, Xu J, Chen D, Kuimin C, Yuan Z, Xiao C. Characteristics and oxidative stress on rats and traffic policemen of ambient fine particulate matter from Shenyang. Sci Total Environ. 2015; 526:110–115.
Bandowe BA, Meusel H, Huang RJ, Ho K, Cao J, Hoffmann T, Wilcke W. PM2.5-bound oxygenated PAHs, nitro-PAHs and parent-PAHs from the atmosphere of a Chinese megacity: seasonal variation, sources and cancer risk assessment. Sci Total Environ. 2014; 473–474:77–87.
West JJ, Cohen A, Dentener F, Brunekreef B, Zhu T, Armstrong B, Bell ML, Brauer M, Carmichael G, Costa DL, Dockery DW, Kleeman M, Krzyzanowski M, Künzli N, Liousse C, Lung SC, Martin RV, Pöschl U, Pope CA 3rd, Roberts JM, Russell AG, Wiedinmyer C. What we breathe impacts our health: improving understanding of the link between air pollution and health. Environ Sci Technol. 2016; 50(10):4895–4904.
ZEpton MJ, Dawson RD, Brooks WM, Kingham S, Aberkane T, Cavanagh JA, Frampton CM, Hewitt T, Cook JM, McLeod S, McCartin F, Trought K, Brown L. The effect of ambient air pollution on respiratory health of school children: a panel study. Environ Health. 2008; 7:16.
Nidhi, Jayaraman G. Air quality and respiratory health in Delhi. Environ Monit Assess. 2007; 135:313–325.
Maitre A, Bonneterre V, Huillard L, Sabatier P, de Gaudemaris. Impact of urban atmospheric pollution on coronary disease. Eur Heart J. 2006; 27:2275–84.
Basagaña X, Jacquemin B, Karanasiou A, Ostro B, Querol X, Agis D, Alessandrini E, Alguacil J, Artiñano B, Catrambone M, de la Rosa JD, Díaz J, Faustini A, Ferrari S, Forastiere F, Katsouyanni K, Linares C, Perrino C, Ranzi A, Ricciardelli I, Samoli E, Zauli-Sajani S, Sunyer J, Stafoggia M; MED-PARTICLES Study group. Short-term effects of particulate matter constituents on daily hospitalizations and mortality in five South-European cities: results from the MED-PARTICLES project. Environ Int. 2015; 75: 151–158.
Zhang JJ, Cui MM, Fan D, Zhang DS, Lian HX, Yin ZY, Li J. Relationship between haze and acute cardiovascular, cerebrovascular, and respiratory diseases in Beijing. Environ Sci Pollut Res Int. 2015; 22(5):3920–3925.
Curtis L, Rea W, Smith-Willis P, Fenyves E, Pan Y. Adverse health effects of outdoor air pollutants. Environ Int. 2006; 32:815–830.
Villeneuve PJ, Weichenthal SA, Crouse D, Miller AB, To T, Martin RV, van Donkelaar A, Wall C, Burnett RT. Long-term exposure to fine particulate matter air pollution and mortality among Canadian women. Epidemiology. 2015; 26(4):536–45.
Ballester F, Tenias JM, Perez-Hoyos S. Air pollution and emergency hospital admissions for cardiovascular diseases in Valencia, Spain. J Epidemiol Community Health. 2001; 55:57–65.
De Steenhuijsen Piters WA, Sanders EA, Bogaert D. The role of the local microbial ecosystem in respiratory health and disease. Philos Trans R Soc Lond B Biol Sci. 2015; 370(1675):1–13.
Martin C, Burgel PR, Lepage P, Andréjak C, de Blic J, Bourdin A, Brouard J, Chanez P, Dalphin JC, Deslée G, Deschildre A, Gosset P, Touqui L, Dusser D. Host-microbe interactions in distal airways: relevance to chronic airway diseases. Eur Respir Rev. 2015; 24(135):78–91.
Brugman S, Perdijk O, van Neerven RJ, Savelkoul HF. Arch Immunol Ther Exp (Warsz). 2015; 63(4):251–268.
Xiao C, Li S, Zhou W, Shang D, Zhao S, Zhu X, Chen K, Wang R. The effect of air pollutants on the microecology of the respiratory tract of rats. Environ Toxicol Pharmacol. 2013; 36:588–594.