Environmental Engg.

Lesson-31 Effects of air pollutants on living beings

Effect of Acid rain

When an air pollutant, such as sulphuric acid combines with the water droplets that make up clouds, the water droplets become acidic. When those droplets fall to the ground as rain or snow, the acidity of the water can have damaging effects on the environment. When acid rain falls over an area, it can kill trees and harm animals, fish, and other wildlife. Acid rain destroys the leaves of plants. When acid rain infiltrates into soils, it changes the chemistry of the soil making it unfit for many living things that rely on soil as a habitat or for nutrition. Acid rain also changes the chemical properties of the lakes and streams that the rainwater flows into, harming fish and other aquatic life.

Ozone layer depletion

Air pollutants called chlorofluorocarbons (or CFCs) destroy ozone molecules in the stratosphere. This has left places in the layer where the ozone is thin. These areas of thin ozone are called ozone holes. The ozone layer, located in the stratosphere layer of Earth’s atmosphere, shields our planet from the Sun’s ultraviolet radiation. Ultraviolet radiation causes skin cancer and damages plants and wildlife.

Tropospheric ozone harms living things

Ozone molecules in the troposphere damage lung tissues of animals and prevent plant respiration by blocking the openings in leaves, called stomata, where respiration occurs. Without sufficient respiration, a plant is not able to photosynthesize at a high rate and will not be able to grow. Ozone is also able to enter the stomata and decay plant cells directly.

Global warming harms living things

Our planet is currently warming much more rapidly than expected because of additional greenhouse gasses that are released into the atmosphere from air pollution. When fuels are burned, some of the pollutants released, such as carbon dioxide, are greenhouses gasses. Through the process of photosynthesis, plants convert carbon dioxide into oxygen and use the carbon to grow larger. However, the amount of carbon dioxide released by burning fuels is far greater than plants can convert. Cutting down forests exacerbates the problem

Human health effects

• Exposure to air pollution is associated with numerous effects on human health, including pulmonary, cardiac, vascular, and neurological impairments. 

• The health effects vary greatly from person to person. High-risk groups such as the elderly, infants, pregnant women, and sufferers from chronic heart and lung diseases are more susceptible to air pollution.

• Exposure to air pollution can cause both acute (short-term) and chronic (long-term) health effects. 

• Acute effects are usually immediate and often reversible when exposure to the pollutant ends. Some acute health effects include eye irritation, headaches, and nausea. 

• Chronic effects are usually not immediate and tend not to be reversible when exposure to the pollutant ends.  Some chronic health effects include decreased lung capacity and lung cancer resulting from long-term exposure to toxic air pollutants.

Effects on human respiratory system

• Both gaseous and particulate air pollutants can have negative effects on the lungs. 

• Solid particles can settle on the walls of the trachea, bronchi, and bronchioles. 

• Continuous breathing of polluted air can slow the normal cleansing action of the lungs and result in more particles reaching the lower portions of the lung. 

• Damage to the lungs from air pollution can inhibit this process and contribute to the occurrence of respiratory diseases such as bronchitis, emphysema, and cancer.

Effect of different air pollutants on living beings

Carbon monoxide

CO (carbon monoxide) combines with haemoglobin to lessen the amount of oxygen that enters our blood through our lungs. The effect of carbon monoxide leads to headaches, reduced mental alertness, heart attack, cardiovascular diseases, impaired fetal development, death.

Sulphur dioxide

It can oxidize and form sulphuric acid mist. Thus, presence of sulphur dioxide is responsible for causing acidity in rains and hence causes corrosion of metal objects and buildings.   SO₂ in the air leads to diseases of the lung and other lung disorders such as wheezing and shortness of breath.  Sulphur dioxide also causes eye irritation, chest tightness.

Nitrogen dioxide

Eye and nasal irritations are the common problems caused by nitrogen dioxide.   Nitrogen dioxide also results in respiratory infections, irritation of the lung and respiratory symptoms (e.g., cough, chest pain, difficulty breathing).

Ozone

Exposure to Ozone leads to eye and throat irritation, coughing, respiratory tract problems, asthma, lung damage.

Lead

Lead is responsible to anemia, high blood pressure, brain and kidney damage and neurological disorders.  Prolonged exposure can cause damage to the nervous system, digestive problems, and in some cases cause cancer. It is especially hazardous to small children.

Particulate matter

Presence of particulate matter leads to eye irritation, asthma, bronchitis, lung damage, cancer, heavy metal poisoning, cardiovascular effects.

Volatile organic compounds.

Volatile compounds can cause irritation of the eye, nose and throat. In severe cases there may be headaches, nausea, and loss of coordination. In the longer run, some of them are suspected to cause damage to the liver and other parts of the body.

Formaldehyde

Exposure to formaldehyde causes irritation to the eyes, nose and may cause allergies