Assistant Professor

Chemistry

Ramabai Ambedkar Government Degree College

 Gajraula, Amroha, U.P., India  

Abstract

Air pollution includes unwanted chemical particles/fumes, dust particles, smoke particles and it damages the health of humans, animals and plants. Monuments and buildings also corrode and are decoloured by the hazardous gases present in high level of air pollution. These particles may be of liquid, gas or solid states [4]. According to WHO, worlds’ most polluted cities are new Delhi (India), Karachi ( Pakistan), Lima(Peru), Cairo( Egypt) and Beijing ( China) [4]. Air pollution can also be defined as unwanted gases present in the atmosphere which are harmful for human health and other living beings or cause climate change adversely. Air pollution is produced in the air by anthropogenic and natural activities. Anthropogenic activities are man made activities such as industries produce hazardous gases, thermal power plant, biomass power plant, emission from vehicles, burning of fossil fuels ( coal, petrol, diesel, PNG< LPG, CNG etc) and household burning of fuel like-wood, crop wastes and dung. Natural activities are activities that produce high amount of  smoke, dust, fog and hazardous chemicals such as wildfires, digestion of biomass produce methane, cattle produce also methane gas during their food digestion and volcanic eruption.    

Air pollution produces as well increases the risk of diseases in humans and other living beings such as heart disease, respiratory infections, COPD [chronic obstructive pulmonary disease], stroke, impaired cognition, depression, lung cancer, cardiovascular damage and detrimental perinatal health. Air pollution exposure may lead to damage the brain health and reduced IQ level [10]. 
 High level of air pollution due to fossil fuel cause for about 3.61 million deaths per year globally. It has been now one of the top contributors to the death of humans. Poor urban air and indoor air are studied in 2008 and found world’s most toxic atmosphere [10]. 

Key Words: Atmospheric gases, Pollutants, Combustion of fuels, Sources of air pollution, Hazardous gases, Particulate matter. 

Introduction   

Indoor and outdoor environmental contamination by unwanted chemical gases, physical and biological activities that change natural composition of atmospheric gases is called air pollution. Many of these pollutants also cause greenhouse effect. These pollutants cause lung, kidney, heart, and liver related diseases [1].

Indoor air pollution-Burning of candles, coal, kerosene, wood, uplaws, LPG , other pesticides, insecticides, fungicides we use in house  and toxic molds present at damp place [4].    

Air pollution and environment -  Haze is visible form of Air pollution and it makes shapes, colors and sounds ( muffle) obscure.  Air pollution contaminate water and soil surface and reduce crop yield [4].  Earth’s climate and global ecosystems are related to air quality of that region. Many air pollutants also contribute as a source of greenhouse gases [10]. 

Sources of Air Pollution

Anthropogenic Sources: Man made activities which produce air pollution are termed as anthropogenic sources. Fossil fuel power plant and biomass power plant produce smoke stacks while oil and gas production sites release methane and hydrocarbon gases. Household burning of wood, crop wastes and dung create major source of pollution. A study (in 2014) done in China machinery and device manufacturing sectors showed that this sector produce above 50% air pollutants. Waste incinerators, motor vehicles, diesel vehicles, aircrafts, rockets create large number of pollutants in air. Deforestation lead air pollution as well as green house gases. Volatile gases from paint, varnish, organic substances produce detrimental air pollution in cities like-Los Angeles (in 2014) [10].

Industrial waste gases, construction works of roads, buildings, combustion of fuels (Petrol, diesel, LPG CNG, PNG etc) in vehicles and other machines, combustion of coal, household combustion of woods and dung [1].

Coal based power plants, fumes from chemical industries and many by-products of manufacturing units are some more sources of this air pollution [2]. Major air polluting things are port, refinery, toxic waste dumps, incineration plants, thermal power plants and all type of vehicles [1,2].

 It is caused due to anthropogenic activities like- emissions from industries, vehicles and planes, smoking, burning of wood, weeds and coal and natural activities like- storm, ash and gases from volcanoes eruptions, wildfires. It is very common in big cities and near big industries [4].

Natural Sources:  Forest fire, fog and storms are major sources of air pollution [1].

 Dust raised from barren lands. Cattle emit methane gas by their digestion. Radioactive decay produces Radon gas in the earth’s crust, it cause lung cancer. Wild fires emit large smoke and CO contribute about 75% air pollution in that region. Black gum, poplar tree, oak and willow tree produce abundant volatile organic compounds (VOC). Volcanic eruptions increase sulphur gases, chlorine and particulate gases [10].  

Emission factors: It is used to estimate the quantity of pollutant released into ambient air to activity connected with that pollutant’s emission. The weight of pollutant divided by unit mass, weight, volume, distance or time of the activity produce that pollutant. Like mg of particulate matter emitted per kg of coal burned. 

Composition of air pollution: Air pollutants include Ozone, Nitrogen dioxide, Hydrocarbons, Carbon dioxide, sulphur dioxide, Particulate matters (PM 2.5 &  PM 10) and volatile hazardous chemicals [1]. There are some examples of air pollutions, like Exhaust bellows emerge from a busy highway, sometimes black haze of pollution covers a city, when a plume come out from a smokestack. Smog is a mixture of smoke and fog, it reduce visibility in nearby atmosphere. About 6.5 ML people die each year globally due to air pollution. Air pollution is a mixture of hazardous gases or suspended particulate matters [2].

There are some examples of air pollutants such as ammonia {NH₃}, carbon monoxide {CO}, sulphur dioxide {SO₂}, nitrous oxides {NxOy}, carbon dioxide {CO₂}, methane {CH₄}, chlorofluorocarbons, biological molecules and inorganic and organic particulates [10].     

Particulate matter (PM):  Some sources of particulate matter are industrial and motor vehicle emissions, combustion of fossil fuel ( coal, petroleum products), burning of wood, cigarette smoke, wild fire, construction works.  A hair is 30 times thicker than PM 2.5. It is inhaled into lungs and create lung diseases. 

Ozone: It is very reactive gas(O₃). When oxygen is radiated by ultraviolet rays, ozone is formed naturally in stratosphere. It stops harmful UV radiation of sun from reaching earth surface and save our life from UV light in one way, UV rays can produce skin cancer and cataract. Where we breath is troposphere. In troposphere, Ozone is produced in the photochemical reaction between nitrogen oxides (sources are power plants, motor vehicles, industrial furnace) and gaseous organic molecules (sources are chemical plants, hydrocarbons, paints and printing industries). It produces smog or haze near earth surface which is very harmful for us. It damages respiratory tract, skin and lungs [3].

Hazardous gases: Carbon monoxide ( CO), Carbon dioxide (CO₂), nitrogen oxides ( NO₂, NO, N₂O₃), sulphur oxides ( SO₂, SO₃), Hydrochloric acid, exhaust of motor vehicles, volatile organic molecules, Halogens etc. SO2, SO3 and NO2, N2O5 etc are causes of acid rains. It change soil quality. Thus damage young plants, crops, aqua life and buildings [4].  

Volatile organic compounds (VOC): The substances which are gas at room temperature is known as VOC. These are obtained from drycleaner activity, paint, pesticides, hydrocarbons (CH₄, C₂H₆, petrol, diesel, CNG, PNG, LPG).

Polycyclic aromatic hydrocarbons (PAH): More than 100 PAH are spreading in the environment. These are derivatives of benzene. It produces in power generation coal plants, steel, iron and rubber manufacturing units as by products.

Smog: The word comes from combination of smoke and fog. It makes the air murky or unclear.

Air Quality Index: AQI is a scale to measure the air quality and it range from 0 to 500. High AQI value shows high air pollution level and more adverse effect on humas health.

AQI is divided into six categories. Each category has its own colour to represent the air pollution levels. EPA establishes five major air pollutants such as [1] ground level ozone [2] particulate matter pollutions ( it include PM 205 and PM10) [3] carbon monoxide [4] Sulphur dioxide [5]  nitrogen dioxide[11].

Effects of air pollution: At first site, air pollution seems accountable mainly for respiratory diseases but it affects brain, heart, kidney and digestion system as well. Cardiovascular diseases, neurological diseases, lung and throat cancer due to gaseous compounds of heavy metals and carcinogenic chemicals. Workers residing near or work in polluting industries and stone cutting sector are very much affected from lung cancer and brain disorder [7]. Effects of air pollution on humans may last for years or for whole life. It also damages central nervous system of human body. About 2.5 million people are being killed worldwide each year from indoor and outdoor air pollution. It is also found to have some merit in birth defects cases.

 Short term effects- Pneumonia/ Bronchitis, discomforts due to itching in nose, ear, eyes, throat and skin. headache, nausea, foul smell comes from garbage and sewer.

Long term effects- Some harmful effects may prevail for years. It includes heart and lung disease, respiratory problem (Emphysema). It damage to brain system, nerves, liver and kidney etc.It can also cause birth defects. Young children and old people are more susceptible from this pollution and more affected from pneumonia and asthma, heart disease etc [4]. 

Air pollution and global warming – Temperature of ocean and our atmosphere increase at globally. This is due to the greenhouse gases (CO₂, CH₄, SO₂,NO, N₂O NO₂, N₂O₅, fluorinated hydrocarbons, Chlorofluorocarbons (CFC) ) emissions from all vehicles, industries and from decomposition of organic wastes. These gases absorb heat energy in atmosphere (Otherwise this heat energy would have been escaped to space). Many countries decided to reduce greenhouse gases emissions. These countries ( About 183) assembled in Kyoto, Japan in 1997 to reduce CO₂ emissions. WHO issues its guidelines in 2006 to reduce air pollution [4]. Air pollution increase the risk of a number of pollution related diseases like-heart disease, respiratory infections, COPD [chronic obstructive pulmonary disease], stroke, impaired cognition, depression, lung cancer, cardiovascular damage and detrimental perinatal health. Air pollution exposuremay lead reduced IQ level [10]. 
Outdoor air pollution due to fossil fuel become cause for about 3.61 million deaths per year globally. It has become one of the top contributors to the death of humans. Poor urban air and indoor air are studied in 2008 and found world’s most toxic atmosphere [10]. 

References:

1. WHO. Air pollution. https://www.who.int/health-topics/air-pollution#tab=tab_1

2. Air pollution and your health. National institute of environmental health sciences.  https://www.niehs.nih.gov/health/topics/agents/air-pollution/index.cfm

3. What is ozone, United states environmental protection agency.

https://www.epa.gov/ozone-pollution-and-your-patients-health/what-ozone#:~:text=Stratospheric%20ozone%20is%20formed%

20naturally,radiation%20reaching%20the%20Earth's%20surface.

4. Air pollution, National geographic.

https://education.nationalgeographic.org/resource/air-pollution.

5. Ama Lorenz, Topic- Ocean pollution, Types and effects of water pollution, December 10, 2019, 

https://www.fairplanet.org/story/types-and-effects-of-water-pollution/

6. Melissa Denchak, Water pollution: everything you need to know. April 18, 2022.

https://www.nrdc.org/stories/water-pollution-everything-you-need-know.

7.  Jillian Mackenzie. Air pollution: everything you need to know. 22 june 2021.

https://www.nrdc.org/stories/air-pollution-everything-you-need-know.

8. Air pollution, National geographic.

https://education.nationalgeographic.org/resource/air-pollution

9. Topper. Soil pollution, Environment chemistry.

https://www.toppr.com/guides/chemistry/environmental-chemistry/soil-pollution/.

10. Air pollution, sources and health effects in Wikipedia.                                                                                         

https://en.wikipedia.org/wiki/Air_pollution.  

11. Air quality index basics. https://www.airnow.gov/aqi/aqi-basics/. 

12. What is air quality index? https://www.aqi.in/blog/aqi/.