Diseases Caused by Air Pollution

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Air pollution is the fifth leading cause of death in the world, and the fourth leading cause of death in China. This pointed out that diseases caused by air pollution is becoming the “invisible killer” of human health. The diseases associated with air pollution are environmental lung diseases. And recently we are seeing that miscarriage in early pregnancy is also happening due to air pollution.

Air Pollution

Burning fossil fuels (coal, petroleum, diesel, and natural gas) causes air pollution, which is mainly caused by the release of toxic chemicals or harmful particles such as coal ash and smoke into the air during combustion. And air pollution can cause serious health problems. According to World Health Organization statistics, 3 million people die each year from the diseases caused by air pollution.

There are two main types of air pollutants.
i) Toxic gases (carbon monoxide, nitrogen oxides and sulfur oxides)
ii) Suspended particulate matter (fine soot, smoke, metals, chemicals, dust, water, and tire rubber)

Smaller particles are more harmful because they enter deep into the human lungs. Exposure to particulate matter can cause asthma and bronchitis, and increase the incidence of colds, flu and other respiratory infections. Carbon monoxide is a colorless, non-irritating gas. After inhalation, it will cause the person’s trachea to tighten, increase the burden on the lungs, and cause headache, dyspnea, chest pain, nausea and fatigue. When severe hypoxia occurs in the body tissues, it leads to suffocation and death.

Diseases Caused by Air Pollution

Smoke and contaminated air can immediately cause tears in the eyes, dry throat, coughing, or difficulty breathing. Severe air pollution can also cause lung damage. Pollution can also aggravate heart or lung disease, making the heart and lungs need to work harder to supply oxygen to various parts of the body, and it can also cause breathing difficulties, fatigue, and chest pain. Prolonged exposure to polluted air can cause:
i) Accelerated lung aging.
ii) Exacerbation of chronic lung diseases such as asthma, chronic bronchitis, emphysema and lung cancer.
iii) Life is shortened, and most people die of a heart attack or stroke.

Air pollution is dangerous for people with heart and lung diseases, pregnant women, children under 14 years of age with developing lungs, and people who exercise or work hard outdoors.

The main causes of air pollution in the developed world are:
i) Nitrogen dioxide (due to burning fossil fuels such as coal, oil and natural gas)
ii) Ozone (due to sunlight reacting with nitrogen dioxide and hydrocarbons)
iii) Solid or liquid suspended particles

The combustion of biofuels (such as wood, animal manure, and straw) in developing countries is an important source of indoor particulate matter. Second-hand smoke is also an important source of indoor pollution.

Severe air pollution can cause asthma or chronic obstructive pulmonary disease (exacerbation) in patients. Air pollution related lung diseases also increase the risk of heart and vascular disease. People living in congested areas are at particular risk. Most air pollutants cause airway muscles to contract, which narrows the airways (highly reactive airways). In the general population, especially for children, long-term exposure to contaminated air may increase the risk of respiratory infections, worsen symptoms of respiratory diseases such as coughing and difficulty breathing, and reduce lung function.

Ozone is an important component of smoke and a strong lung irritant. Ozone levels are higher in summer than in other seasons, and higher during the day later in the morning and earlier in the afternoon than at other times. Short-term exposure can cause dyspnea, chest pain, and airway hyperresponsiveness. Children who are outdoors when ozone levels are high are more likely to develop asthma. Prolonged exposure to ozone can cause slight and permanent declines in lung function.

Acid particles produced by burning high-sulfur fossil fuels tend to deposit in the upper airways. These particles, called sulfur oxides, can cause inflammation and contraction of the airways, causing symptoms such as dyspnea, and increase the incidence of chronic bronchitis.

Air pollution particles from fossil fuel combustion (especially diesel) are complex mixtures. These particles can cause airway inflammation or affect other parts of the body, such as the heart. Some research data suggest that air pollution particles increase all-cause mortality, especially heart and lung disease.

Pollutant levels in the air vary according to location and environmental conditions. For example, ozone is easily trapped in the air on warm and humid days, especially in the afternoon or early morning. When many office workers drive to and from work, the level of carbon dioxide in the air is usually high. The air quality index is used to indicate the degree of air pollution at a given point in time. People (especially those with heart or lung disease) can use air quality index to guide them to choose outdoor activities on days with high pollution levels.

Nanoparticles: A New Cause of Environmental Lung Disease?

The different effects of particles on the lungs depend on what they are made of. Particles of the same substance may also have different effects on the lungs depending on their size and shape. For example, the risk of inhaling asbestos varies with the size and length of the asbestos fibers.

For various uses such as carbon, the nanotechnology industry produces extremely small particles. When these particles are smaller than 100 nanometers, they are called nanoparticles. For comparison, the diameter of a person’s hair is about 100,000 nanometers, so 1,000 nanometer particles are equivalent to the thickness of a hair.

Animal and laboratory tests have shown that high concentrations of nanoparticles can be dangerous. Some workers accidentally exposed to high levels of nanoparticles have developed pleural effusion or small airway damage to the lungs. But physicians don’t know the exact impact of the number and type of nanoparticles exposed on nanoindustrial workers. Research on assessing risks and ensuring workers’ protection is ongoing.

Diagnosis of environmental lung disease

Doctor evaluation
Doctors make a diagnosis based on the patient’s symptoms, the results of a lung function test, and the patient’s exposure to high concentrations of known pollutants at work and at home. Doctors ask patients with lung diseases (such as asthma and chronic obstructive pulmonary disease) if their symptoms worsen when exposed to contaminated air.

Testing often does not help distinguish pollution-related diseases from other lung diseases. If many workers in the same occupation with similar exposures have the same lung disease (including after sudden, high-volume exposures), the diagnosis may become clearer.

Prevention of Environmental Lung Disease

Workers exposed to polluted air should follow the recommendations issued by major government agencies to minimize exposure to airborne gases, dust and smoke. Children, the elderly, and people with asthma, chronic obstructive pulmonary disease, and other lung diseases should avoid participating in outdoor sports when the air is high in pollutants.

Treatment of Environmental Lung Disease

Symptomatic treatment
Treat to relieve symptoms. For example, medications used to treat asthma, such as bronchodilators that open the airways, can relieve some symptoms. If the symptoms are more severe, the patient may need oxygen therapy or mechanical ventilation.

Air Pollution or Increased Risk of Miscarriage in Early Pregnancy

Poor air quality is one of the main causes of illness. Numerous studies have shown that mothers’ exposure to polluted air increases the risk of childbirth and may affect the health of the mother during pregnancy and even throughout her life. However, little is known about the relationship between abortion in early pregnancy and air pollution.

Beijing Normal University professor Zhang Liqiang and collaborators analyzed the clinical records of more than 250,000 pregnant women in Beijing over the past 10 years and found that exposure to air pollution is associated with an increased risk of miscarriage during pregnancy. Related results were published in the journal Nature-Sustainability on October 14. The significance of this study is to remind pregnant women to take some protective measures consciously. On the other hand, we hope that people will take more active measures to improve air quality and better protect their health.

To understand the impact of air pollution on pregnant women’s miscarriages in Beijing, researchers analyzed the clinical records of 255,668 pregnant women in the city from 2009 to 2017, including their education level, occupation, residence and work place, and based on their residence and work Measurement data from air monitoring stations (34 in total) near the site calculated air pollutant exposure levels for each pregnant woman. Pollutants involved in the study include PM2.5 particulate matter, sulfur dioxide, ozone and carbon monoxide.

Researchers divided pregnant women into groups according to age of conception, occupation, and ambient air temperature. Of the participating pregnant women, 17,497 (6.8%) experienced missed abortion. “We found that the risk of miscarriage is related to the age of the pregnant woman and the external high and low temperature,” said Hou Min, a doctoral student in the Department of Geography at Beijing Normal University. The study found that older women, women farmers, and blue-collar workers over 39 years of age had higher rates of miscarriage. In all groups, exposure of pregnant women to various air pollutants is associated with the risk of miscarriage.

The researchers also found that for all four pollutants, the increased risk of miscarriage was associated with an increase in the concentration of the pollutants, as well as the length of time pregnant women were exposed to the polluted environment. “Our research found a quantitative relationship between them.” Zhang Liqiang said. This increase in risk is not linear, but a non-linear growth relationship with increasing pollutant concentrations.

Toxic substances attack the fetus

Regarding the impact of four types of air pollutants on missed abortion, Hou Yi said that the impact of PM2.5 is particularly severe.

“Toxic substances may attack developing fetuses by inducing immune changes through the placenta,” the authors point out in the article.

Carbon monoxide may interfere with the placenta’s metabolic and transport functions. After crossing the placental barrier, the concentration in the fetus will be even higher than that of the mother. In addition, environmental carbon monoxide is associated with carboxylated hemoglobin (COHb) and nucleated red blood cells. Too much COHb in the mother’s body can make the fetus hypoxic, leading to fetal death.

Zhang Liqiang introduced that the PM2.5 concentration in this statistics ranges from more than 30 micrograms per cubic meter to more than 200 micrograms. However, due to the strong collinear relationship between PM2.5 and carbon monoxide, the authors did not distinguish the respective effects of these two pollutants.

Studies have shown that long-term exposure of pregnant women to air pollution may mean higher chances of miscarriage, stillbirth and birth defects. The author also explores several possible causal mechanisms to explain this association. If the mother is exposed to the PM2.5 environment for a long time, the pollutants will cross the mother-fetal blood barrier and affect the growth and development of the fetus. Contaminants that enter the fetal blood may interact with its tissue components, resulting in pathological effects, causing irreversible damage to fetal dividing cells, and causing hypoxic damage or immune damage during the critical period of fetal development. In addition, related studies have also observed epigenetic changes in the placenta caused by air pollution during 3 months of pregnancy. This suggests that mother’s exposure to air pollution may impair placental function.

But Zhang Liqiang particularly emphasized that this study only proved a correlation between air pollution and missed abortion, not a causal relationship. “Although we can adjust many known risk factors related to missed abortion, we cannot rule out residual confounding factors because we cannot control other factors such as traffic noise,” the author wrote in the article. In addition, researchers said that due to the lack of relevant data, there is less research on the impact of indoor air pollution on missed abortion, but indoor pollution is highly related to environmental pollution.

To control air pollution and to prevent diseases caused by air pollution, at first we have to know the cause, effects and prevention of air pollution.


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