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The negative impact of poor air quality on humans and plants

Abstract Air pollution is a major concern of new civilized world, which has a serious toxicological impact on human health and the environment.

  • They are deep lung irritants that can induce pulmonary edema if been inhaled at high levels;
  • Therefore, moving capital city will not solve the problem of air pollution and only reduces the problem in the short term.

It has a number of different emission sources, but motor vehicles and industrial processes contribute the major part of air pollution. According to the World Health Organization, six major air pollutants include particle pollution, ground-level ozone, carbon monoxide, sulfur oxides, nitrogen oxides, and lead.

Long and short term exposure to air suspended toxicants has a different toxicological impact on human including respiratory and cardiovascular diseases, neuropsychiatric complications, the eyes irritation, skin diseases, and long-term chronic diseases such as cancer.

Several reports have revealed the direct association between exposure to the poor air quality and increasing rate of morbidity and mortality mostly due to cardiovascular and respiratory diseases.

Air pollution is considered as the major environmental risk factor in the incidence and progression of some diseases such as asthma, lung cancer, ventricular hypertrophy, Alzheimer's and Parkinson's diseases, psychological complications, autism, retinopathy, fetal growth, and low birth weight. In this review article, we aimed to discuss toxicology of major air pollutants, sources of emission, and their impact on human health.

We have also proposed practical measures to reduce air pollution in Iran. The sources of pollution vary from small unit of cigarettes and natural sources such as volcanic activities to large volume of emission from motor engines of automobiles and industrial activities.

  1. Pollution or the introduction of different forms of waste materials in our environment has negative effects to the ecosystem we rely on. Breathing polluted air puts you at a higher risk for asthma and other respiratory diseases.
  2. Standardization of vehicle's fuel as much as possible and also finding a new source of energy for motor engines has attracted great attention.
  3. Such sources of emissions liberate gases and substances that are toxic for human beings, the most harmful of which are. In this review, we have tried to summarize the toxicology of air pollutants and related diseases with a possible mechanism of action and appropriate management of the patients.
  4. Regulatory programs should apply high taxes per unit of emission not only as a penalty for air polluters but also should give rise to the cost of pollution for them in order to ensure the efficient reduction of pollutants.
  5. We are already seeing its effects in the form of global warming, contaminated seafood, increased cases of lung diseases and more.

Ahvaz is the most air polluted city in the world with microdust blowing in from neighboring countries, and particulate levels three times that of Beijing, and nearly 13 times that of London.

The present article is neither a systematic review nor a descriptive, educational study. It is a problem-based descriptive review in which the authors try to explain a problem which is the major health and ecological problem in developing countries like Iran.

In this review, we have tried to summarize the toxicology of air pollutants and related diseases with a possible mechanism of action and appropriate management of the patients. Therefore, it shall be useful for the environmental and health professionals particularly policy makers, emergency physicians, and other clinicians who may be involved in air pollution and related diseases.

In this paper, we also discuss sources of air pollution and proposed some feasible solutions which may be beneficial for the environmental legislators and decision makers.

It is made up of many kinds of pollutants including materials in solid, liquid, and gas phases. The Pollutant Standard Index PSI is a numerical value and indicator of pollutants that is normally used to facilitate risk assessment. It is a numeric value between zero to 500. According to Johnson et al. It provides a number from healthy standard level of zero to a very hazardous level of above 300 to indicate the level of health risk associated with air quality.

Based on PSI, air quality is classified into six major indices, which is marked by color codes and each color corresponds to a different level of health concerns.

Principally, green is defined as a color indicator for healthy air quality; while yellow, orange, red, purple, and maroon colors indicate as moderate, unhealthy for sensitive groups, unhealthy, very unhealthy, and hazardous air quality, respectively.

These ranges and codes may differ in the different methods the negative impact of poor air quality on humans and plants classifications in different countries. Different geographical conditions, global climate changes, and the environmental variations affect the human health and the environment including the animal life.

Environmental damages Ecologically, air pollution can cause serious environmental damages to the groundwater, soil, and air.

Studies on the relationship between air pollution and reducing species diversity clearly show the detrimental effects of environmental contaminants on the extinction of animals and plants species. According to the World Health Organization WHOparticle pollution, ground-level O3, CO, sulfur oxides, nitrogen oxides, and lead Pb are the six major air pollutants which harm human health and also the ecosystem.

There are many pollutants of suspended materials such as dust, fumes, smokes, mists, gaseous pollutants, hydrocarbons, volatile organic compounds VOCspolycyclic aromatic hydrocarbons PAHsand halogen derivatives in the air which at the high concentrations cause vulnerability to many diseases including different types of cancers.

Particle pollutants Particle pollutants are major parts of air pollutants. In a simple definition, they are a mixture of particles found in the air.

Particle pollution which is more known as PM is linked with most of pulmonary and cardiac-associated morbidity and mortality. The size of particle pollutants is directly associated with the onset and progression of the lungs and heart diseases.

  • It is mostly emitted from fossil fuel consumption, natural volcanic activities, and industrial processes;
  • However, the molecular and cell toxicity may also induce a variety of cancers in the long term.

Particles of smaller size reach the lower respiratory tract and thus have greater potential for causing the lungs and heart diseases. Depending on the level of exposure, particulate pollutants may cause mild to severe illnesses. Wheezing, cough, dry mouth, and limitation in activities due to breathing problems are the most prevalent clinical symptoms of respiratory disease resulted from air pollution.

The increase of cardiopulmonary and lung cancer mortality are the main reasons for the reduction in life expectancy. Reduced lung functions in children and adults leading to asthmatic bronchitis and chronic obstructive pulmonary disease COPD are also serious diseases which induce lower quality of life and reduced life expectancy.

  • Depending on the level of exposure, particulate pollutants may cause mild to severe illnesses;
  • Coughing and wheezing are common symptoms observed on city folks;
  • Air pollution can have a serious heath impact on humans.

Strong evidence on the effect of long-term exposure to PM on cardiovascular and cardiopulmonary mortality come from cohort studies. It is found both at the ground level and in the upper regions of the atmosphere which is called troposphere. GLO is believed to have a plausible association with increased risk of respiratory diseases, particularly asthma. There is a high level of polyunsaturated fatty acids in the surface fluid lining of the respiratory tract and cell membranes that underlie the lining fluid.

The double bonds available in these fatty acids are unstable. O3 attacks unpaired electron to form ozonides and progress through an unstable zwitterion or trioxolane depending on the presence of water. These ultimately recombine or decompose to lipohydroperoxides, aldehydes, and hydrogen peroxide. These pathways are thought to initiate propagation of lipid radicals and auto-oxidation of cell membranes and macromolecules. It also increases the risk of DNA damage in epidermal keratinocytes, which leads to impaired cellular function.

The affinity of CO to hemoglobin as an oxygen carrier in the body is about 250 times greater than that of oxygen. Depending on CO concentration and length of exposure, mild to severe poisoning may occur. Symptoms of CO poisoning may include headache, dizziness, weakness, nausea, vomiting, and finally loss of consciousness.

The symptoms are very similar to those of other illnesses, such as food poisoning or viral infections. Hypoxia, apoptosis, and ischemia are known mechanisms of underlying CO toxicity. Thus, the reduction in ambient CO can reduce the risk of myocardial infarction in predisposed persons. Sulfur dioxide SO2 is a colorless, highly reactive gas, which is considered as an important air pollutant. It is mostly emitted from fossil fuel consumption, natural volcanic activities, and industrial processes.

SO2 is very harmful for plant life, animal, and human health.

The effects of air pollution on human health

People with lung disease, children, older people, and those who are more exposed to SO2 are at higher risk of the skin and lung diseases. The major health concerns associated with exposure to high concentrations of SO2 include respiratory irritation and dysfunction, and also aggravation of existing cardiovascular disease. SO2 is predominantly absorbed in the upper airways.

As a sensory irritant, it can cause bronchospasm and mucus secretion in humans. The penetration of SO2 into the lungs is greater during mouth breathing compared to nose breathing.

An increase in the airflow in deep, rapid breathing enhances penetration of the gas into the deeper lung. Therefore, people who exercise in the polluted air would inhale more SO2 and are likely to suffer from greater irritation.

When SO2 deposits along the airway, it dissolves into surface lining fluid as sulfite or bisulfite and is easily distributed throughout the body.

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It seems that the sulfite interacts with sensory receptors in the airways to cause local and centrally mediated bronchoconstriction. Due to its solubility in water, SO2 is responsible for acid rain formation and acidification of soils.

SO2 reduces the amount of oxygen in the water causing the death of marine species including both animals and plants. Exposure to SO2 can cause damages to the eyes lacrimation and corneal opacitymucous membranes, the skin redness, and blistersand respiratory tracts. Bronchospasm, pulmonary edema, pneumonitis, and acute airway obstruction are the most common clinical findings associated with exposure to SO2. They are deep lung irritants that can induce pulmonary edema if been inhaled at high levels.

They are generally less toxic than O3, but NO2 can pose clear toxicological problems. Although these levels may be high, epidemiologic studies demonstrate effects of NO2 on respiratory infection rates in children. Coughing and wheezing are the most common complication of nitrogen oxides toxicity, but the eyes, nose or throat irritations, headache, dyspnea, chest pain, diaphoresis, fever, bronchospasm, and pulmonary edema may also occur.

In another report, it is suggested that the level of nitrogen oxide between 0. It is emitted from motor engines, particularly with those using petrol containing Pb tetraethyl. Smelters and battery plants, as well as irrigation water wells and wastewaters, are other emission sources of the Pb into the environment. Because it is not readily excreted, Pb can also affect the kidneys, liver, nervous system, and the other organs. Retained Pb absorption through alveoli is absorbed and induces toxicity.

Pb is a powerful neurotoxicant, especially for infants and children as the high-risk groups.

Effects of Air Pollution

Mental retardation, learning disabilities, impairment of memory, hyperactivity, and antisocial behaviors are of adverse effects of Pb in childhood. Pb may also replace calcium as a second messenger resulting in protein modification through various cellular processes including protein kinase activation or deactivation.

Abdominal pain, anemia, aggression, constipation, headaches, irritability, loss of concentration and memory, reduced sensations, and sleep disorders are the most common symptoms of Pb poisoning. Exposure to Pb is manifested with numerous problems, such as high blood pressure, infertility, digestive and renal dysfunctions, and muscle and joint pain.

Other air pollutants Other major air pollutants that are classified as carcinogen and mutagen compounds and are thought to be responsible for incidence and progression of cancer in human include VOCs such as benzene, toluene, ethylbenzene, and xylene, PAHs such as acenaphthene, acenaphthylene, anthracene, and benzopyrene, and other organic pollutants such as dioxins, which are unwanted chemical pollutants that almost totally produced by industrial processes and human activity.

Table 1 Standard level of criteria air pollutants and their sources with health impact based on the United States Environmental Protection Agency Open in a separate window As the negative impact of poor air quality on humans and plants can be easily understood, fossil fuel consumption shares the largest part of air contamination.

Air pollutants can also be classified into anthropogenic and natural according to their source of emission. From anthropogenic aspect, air contamination occurs from industrial and agricultural activities, transportation, and energy acquisition. While from natural contaminant has different sources of emission such as volcanic activities, forest fire, sea water, and so on. According to available data, the main toxic effects of exposure to air pollutants are mainly on the respiratory, cardiovascular, ophthalmologic, dermatologic, neuropsychiatric, hematologic, immunologic, and reproductive systems.

However, the molecular and cell toxicity may also induce a variety of cancers in the long term. Depending on the dose of inhaled pollutants, and deposition in target cells, they cause a different level of damages in the respiratory system.

In the upper respiratory tract, the first effect is irritation, especially in trachea which induces voice disturbances. Air pollution is also considered as the major environmental risk factor for some respiratory diseases such as asthma and lung cancer.

Cardiovascular dysfunctions Many experimental and epidemiologic studies have shown the direct association of air pollutant exposure and cardiac-related illnesses. On the other hand, a study on animal models suggested the close relationship between hypertension and air pollution exposure.

Neuropsychiatric complications The relationship between exposure to air suspended toxic materials and nerve system has always been argued. However, it is now believed that these toxic substances have damaging effects on the nervous system. The toxic effect of air pollutants on nerve system includes neurological complications and psychiatric disorders. Neurological impairment may cause devastating consequences, especially in infants.

In contrast, psychiatric disorders will induce aggression and antisocial behaviors.