Air Pollutants

Air Pollutants

Define Air Pollutants

Air pollutants are the substances or agents that contribute to air pollution. They can be chemical, physical, biological or radioactive (Reitze, 2001). They can come from natural sources, or they can occur because of human activities. Natural pollutants refer to pollutants that are released from natural sources, such as volcanic activity. Pollutants that occur due to human activities are referred to as anthropogenic pollutants. They occur because of human activities and processes such as the combustion of fossil fuels. Understanding the nature and cause of the air pollutants will help in controlling air pollution. Air pollution is the contamination of the air, and it occurs when the air contains harmful substances such as dust, fumes, and harmful gases and odors in levels that affect human health and the environment. Air pollutants can be primary or secondary.

Primary Sources

Primary sources release air pollutants directly into the atmosphere from sources such as exhaust pipes and factories. The sources can be anthropogenic or natural. Primary pollutants include carbon monoxide, sulfur dioxide, volatile organic compounds, particulates, and nitrogen oxides (WHO, 2006). Primary pollutants do not change their chemical format when they are released in the atmosphere. Controlling primary pollutants from anthropogenic sources is easier than controlling the secondary pollutants or primary pollutants from natural sources because they are controlled at the source.

Secondary Sources

Sometimes, primary pollutants and natural particles undergo chemical and physical changes, resulting into secondary pollutants. Primary pollutants react with other elements, and they produce secondary pollutants. The chemical reaction that occurs when producing the secondary pollutants produces products that are less reactive than the original elements. Increase in temperature, mainly from the heat produced from the sun, increases the reactivity of the products. Secondary pollutants include photochemical smog, ozone, and nitrogen oxides (WHO, 2006). It is difficult to control secondary pollutants because one has to know the chemical processes that took place when forming the pollutants, and the chemical formation of the pollutants, and identify the sources of the pollutants (EPA, 2010).

Major Air Pollutants

Carbon monoxide is one of the major pollutants. It is a colorless and odorless gas, which is harmful to human health. It occurs when there is incomplete combustion of carbon fuels. The complete combustion of carbon containing fuels release carbon dioxide. Most of the carbon monoxide occurs because of human activity. The biggest source of carbon monoxide is the transportation sector because of the exhaust from motor vehicles, and the industries that use carbon based fuels. Therefore, levels of carbon monoxide are highest in areas with many motor vehicles and traffic congestion. Other activities such as wood burning, forest fires, wood and gas stoves, and cigarette smoke contribute to increased levels of carbon monoxide in the atmosphere (EPA, 2010). Carbon monoxide combines with hemoglobin in the body, reducing a person’s oxygen. It reduces the blood supply in the body. It weakens visual perception, limits learning and work ability, and weakens a person’s ability to perform complex tasks (Reitze, 2001).

Sulfur dioxide gas is harmful to human health and it damages other materials. It is released when there is combustion of fossil fuels that contain sulfur. It is therefore prevalent in areas where people use coal as the main source of fuel. Although it is an anthropogenic pollutant, it can also occur because of volcanic activity. Other sources of sulfur dioxide are the industries that use crude oil and metallic ore as their raw materials (EPA, 2010). It has diverse effects on human health, and it affects various organs such as the eyes, lungs, and nose. It intensifies cardiovascular and respiratory diseases, and weakens the lungs’ defenses (Reitze, 2001). Sulfur dioxide is soluble in water, and it forms sulfuric acid when combined with water. This acid can fall to the earth as acid rain, which has negative effects on the environment. It combines with other gases in the atmosphere to form sulfates and other particles, which have negative effects on human health and the environment.

Fossil fuels contain varying amounts of nitrogen, and when burned, they release oxides of nitrogen in the atmosphere. Nitrogen oxides contribute to the formation of ozone. The main sources of nitrogen oxides are motor vehicles and other industries and activities that burn fuels. Nitrogen dioxide is a toxic reddish brown gas, which has a pungent odor. It has negative health effects because it decreases the body’s resistance to respiratory diseases. In high concentration, the gas aggravates acute respiratory disease in children (Rietze, 2001).

The chemical reaction of volatile organic compounds and oxides of nitrogen produce ozone when there is sunlight. The levels of the volatile organic compounds, presence and intensity of sunlight, and nitrogen in an area will determine the ozone levels in that area. However, ozone is transported over wide regions, and this means that it causes air pollution in many areas. When the ozone is present at upper levels on the atmosphere, it forms a layer that protects the earth from ultraviolet radiation (EPA, 2010). Ozone is a major component of photochemical smog. It causes respiratory problems such as asthma, and it impairs and causes inflammation on the lungs. It also reduces the body’s resistance to infections.

Particulate matter refers to heterogeneous mixture of solid particles and liquids in the atmosphere. These particles include soot, smoke and dust. Particulates can be primary or secondary pollutants. Organic chemicals, nitrates, sulfates, and metals contribute towards particle pollution. Some particles are small enough to penetrate the human body. Their effect on human health depends on their size and chemical composition. Some particulates are big and they remain on the ground, while others are smaller and they remain suspended on the air (Reitze, 2001). They enter through the nose and throat, and they reach the lungs. Some particles poison the blood. They cause serious health effects, as they affect the heart and lungs once a person inhales them. These particles can cause permanent damage to the lungs, and they aggravate respiratory problems (Reitze, 2001)

Lead is an air pollutant, and it has adverse effects on a person’s health. Once a person inhales it, it is retained in the body, and it builds up in the blood, bones, and tissues. It damages body organs such as the brain, the circulatory system, and the nervous system. It can also cause mental retardation and behavior disorders. Industries such as metal processing and battery manufacturing contribute to the increased levels of lead in the atmosphere (Reitze, 2001).

Clean Air Act

The establishment of the Clean Air Act enabled the government to reduce interstate pollution. It sets the standards for air quality regulations. It regulates emissions from mobile and stationary sources. It gives more authority to the Environmental Protection Agency (EPA), and this enables it to set the limits on the pollutants permitted anywhere in the country. One of the main objectives of the act when it was established was to ensure that it set the National Air Quality Standards in all the states to reduce the risks of the air pollutants. Although different states can set environmental regulations, they cannot enforce weaker limits than those provided in the act. Since the passage of the act, there has been a reduction in the lead levels in the atmosphere. This is because there is less sulfur on motor vehicle fuel (Raven et al., 2011).

The EPA sets different programs to ensure that the air is free from pollutants that cause acid rain, smog, and haze. It ensures that it eliminates or reduces the chemicals that destroy the stratospheric ozone, and cause diverse health problems. It has identified six criteria pollutants found all over the country, and these include particulate matter, carbon monoxide, lead, sulfuric oxides, nitrogen oxides, and ground level ozone. The agency aims to clean up these pollutants because of the risk they pose to people and the environment. The agency has established measures that will ensure that people are more responsible. For instance, it requires the manufacturers to build cleaner engines, refiners to produce cleaner fuels, and people to maintain their vehicles and other machines in good conditions. This is because the transportation sector accounts for most of the carbon monoxide in the atmosphere. Since the establishment of the Clean Air Act, people have become more aware of air pollution. Environmentalists have discovered the effects of air pollution on people and on the environment. They have discovered various forms of acid precipitation such as acid fog, acid snow, acid mist, and dry forms of acidic pollution. They have discovered the elements that contribute to increased levels of air pollution. This has led to people leading healthier lives and has contributed towards a less polluted environment.

Impact on the Environment

Air pollutants have diverse effects on the environment. They damage the vegetation, ecosystem and buildings. High concentration of air pollutants causes premature early leaf drop (senescence), which can end up killing the plants and trees. The pollutants affect the reproductive cycle of the plants, leading to stunted or reduced growth. The pollutants change the physiological and biochemical processes in plants (Vallero, 2007). They reduce the number of chloroplasts, leading to discoloration of plants. Sulfur dioxide has a negative effect on the environment because it damages trees and agricultural crops such as soybeans, corn, and wheat. It also corrodes buildings. Crops have lower yields when they are exposed to ozone. Ozone has reduced the eastern white pine trees, ponderosa, and Jeffrey trees (Reitze, 2001). Sulfur dioxide is converted to tiny particles, which in turn form aerosols. Aerosols form a haze, which reduces the amount of sunlight reaching the earth’s surface, and this affects visibility. Particulate matter contributes to the formation of smog.

Acid deposition in water bodies leads to the decline of aquatic life because of the changes in the pH levels. High metal content in water bodies is poisonous to aquatic plants and animals. It kills fish and destroys some of the aquatic plants. The lack of calcium in the water and plants affects birds. Birds lay eggs with thin and fragile shells, most of which end up drying out before they hatch. This is because the birds do not get enough calcium (Raven et al., 2011). Animals accumulate air pollutants through vegetation, and not necessarily through inhalation. Acid deposition increases soil acidity, and causes some important minerals to leach out of the soil. This affects plants and it causes decline of some plants and death of others. The effect of the acid on the soil weakens the ability of the trees to tolerate stresses from the environment. This can be disastrous on a large scale because it can cause the gradual destruction of forests (Vallero, 2007).

Acid deposition from sulfur and nitrogen oxides corrodes metals and damages buildings. Ozone oxides many products, and it damages fabrics and rubber materials. Air pollutants damage stone materials. It erodes soils and blackens them. It destroys the monuments made of stone by eroding the details. It forms crusts on these monuments and buildings. Air pollutants corrode metal surfaces, deteriorate the coating, and perforate the surfaces. The pollutants destroy glass items by corroding potash glass and soiling the modern soda glass (Watt, 2009). Therefore, air pollutants destroy the materials made from stone, rubber, wood, fabric, and metal.

References:

EPA. (2010). Air pollution. Environmental Protection Agency. Retrieved from http://www.epa.gov/apti/course422/ap2.html

Raven, H. P., Hassenzahl, M. D., & Berg, R. L. (2011). Environment. Hoboken, NJ: John Wiley & Sons

Reitze, W. A. (2001). Air pollution control law: Compliance and enforcement. Washington, DC: Environmental Law Institute

Vallero, A. D. (2007). Fundamentals of air pollution. Burlington, MA: Academic Press

Watt, J. (2009). The effects of air pollution on cultural heritage. New York, NY: Springer

WHO (2006). Air quality guidelines: Global update 2005: Particulate matter, ozone, nitrogen dioxide and sulfur dioxide. Copenhagen, Denmark: World Health Organization

 

 

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