The term pollution originates from the Latin word “Pollutionem”, meaning "to defile" or "to make dirty". In modern environmental science, pollution is the entry of unwanted substances into the environment in solid, liquid, or gaseous forms, adversely affecting both humans and nature.
E.P. Odum (1971) defined pollution as “an undesirable change in the physical, chemical and biological characteristics of air, water and soil which affects human beings in various ways.”
Mishra (2006) explained pollution as “the introduction of substances or energy which are liable to cause hazards to human health, harm to living resources and ecological systems, damage to structure or amenity, or interference with legitimate use of the environment.”
Both definitions highlight that pollution can arise from human actions or natural events, such as volcanic eruptions and forest fires.
Pollution is essentially an anthropogenic addition to the bio-geo-chemical cycles that disrupts natural processes.
Pollution has reached such severe levels that accessing clean air, water, and food has become a growing global concern.
Scientists, environmentalists, and human rights advocates now view pollution as one of the greatest threats to human persistence.
Combating pollution is essential for human survival and ecological sustainability.
Environmental pollution occurs when pollutants—agents or substances that contaminate the Earth’s biosphere—are present in any of its systems.
Biodegradable pollutants break down naturally over time. Examples include tree leaves and domestic organic waste.
Non-biodegradable pollutants do not decompose and persist in the environment. These include plastics, pesticides, and nuclear waste.
Point source pollution originates from identifiable locations like sewage pipes, industrial effluents, and chimneys.
Non-point source pollution occurs over large areas, such as agricultural runoff, mining zones, and construction sites.
Air Pollution: Caused by emissions from vehicles, industries, and burning of fossil fuels.
Water Pollution: Results from dumping of untreated sewage, industrial waste, and chemicals into water bodies.
Soil Pollution: Occurs through excessive use of fertilizers, pesticides, and improper waste disposal.
Noise Pollution: Arises from transportation, industrial activities, and urban development.
WHO reports that air pollution is one of the deadliest threats in Southeast Asia. According to the United Nations, nine out of every ten people globally are inhaling polluted air.
Air is a mixture of gases that makes life possible on Earth by sustaining both plant and animal life. Air pollution refers to the physical, chemical, or biological alteration of the atmosphere, and it affects both indoor and outdoor environments.
This type of pollution leads to a wide spectrum of issues, from skin irritations to potentially fatal health conditions. It also damages ecosystems, crops, and built environments.
Pollutants are the harmful substances contaminating the air. Common examples include nitrogen oxides, hydrocarbons, sulphur oxides, carbon monoxide, and dust particles.
Sources of these pollutants range from human to natural origins. These include:
While many of these pollutants stem from anthropogenic activities, natural phenomena such as dry, vegetation-less areas, volcanic eruptions, and wildfires also contribute significantly.
Air pollutants are toxic substances impacting air quality. Their measurement is categorized into two formats:
This highly toxic pollutant is produced by the incomplete combustion of fossil fuels. It is found in high concentrations in urban zones and emitted through vehicles and power plants.
This compound is a primary agent behind acid rain. Roughly 90% of SO₂ emissions originate from burning fossil fuels, particularly coal containing around 6% sulphur, as well as from ore smelting and oil refineries.
Produced during the combustion of petrol and diesel, nitrogen oxides contribute to acid rain and urban haze. They include nitrogen dioxide, nitric oxide, and nitrous oxide.
This group includes methane (CH₄), ethane (CH₆), propane (CH₈), and butane (CH₁₀). While naturally emitted through organic decomposition, a major share comes from human-induced sources. Hydrocarbons are a key factor in the formation of urban smog.
These synthetic compounds contain chlorine, fluorine, and carbon. With atmospheric lifespans of 50 to 100 years, they are directly linked to ozone depletion and climate change. CFCs are used in refrigeration, aerosol sprays, air-conditioning, and foam manufacturing.
Composed of solid particles and aerosols, these pollutants lack a fixed chemical structure and can include soot, smoke, asbestos fibers, dust, and pesticides. Some are combinations like ammonia with sulphuric or nitric acid.
Combustion of fossil fuels in vehicles like trucks, jeeps, cars, trains, and airplanes releases pollutants such as smoke, carbon dioxide (CO₂), carbon monoxide (CO), and nitrous oxide (N₂O). These emissions contribute significantly to atmospheric pollution.
Mining involves the extraction of minerals beneath the Earth’s surface. This process emits large amounts of dust and chemicals into the air, leading to increased air pollution.
Everyday household items like cleaning products and painting supplies release toxic chemicals, leading to indoor air pollution.
Insecticides, pesticides, and fertilizers emit hazardous airborne chemicals that pollute the atmosphere. Additionally, stubble burning after paddy harvests intensifies pollution levels. Farmers often burn leftover crop residues to prepare fields for the next cycle, further aggravating air quality.
Air pollution is responsible for nearly 800 deaths every hour, exceeding the death toll of malaria, tuberculosis, and AIDS combined each year. Alarmingly, over 90% of children globally live in areas where air quality surpasses acceptable WHO limits.
Global warming refers to the rise in Earth’s surface temperature, sea levels, and melting of glaciers. This process disrupts ecosystems and displaces communities across the globe. Proactive action is essential to mitigate warming and preserve environmental balance.
Burning of fossil fuels releases sulphur and nitrogen oxides that interact with atmospheric moisture to form acid rain. This rain severely damages human health, wildlife, vegetation, and agricultural yields.
Millions suffer or die due to health conditions linked to air pollution. Children are particularly vulnerable and commonly experience asthma, respiratory infections, and pneumonia.
Chlorofluorocarbons (CFCs) and hydrocarbons cause ozone depletion. As the ozone layer weakens, harmful ultraviolet radiation increases, leading to skin disorders and eye diseases.
Water makes up about 70% of the Earth's surface, but only 2.5% is fresh and safe for consumption. As the global population rises, water resources face mounting stress from human activity. Water pollution occurs when harmful substances are released directly or indirectly into water bodies without adequate treatment, thereby degrading water quality and threatening living organisms.
Human activities such as improper waste disposal, toxic wastewater release, and unregulated sewage flows are the leading contributors. Pollution impacts rivers, lakes, oceans, and even drinking water systems globally. About 80% of this contamination originates from domestic sewage. Water pollution can be broadly classified into:
With urbanization, the reliance on groundwater has increased drastically. However, this vital resource is being polluted due to:
Contaminants found in polluted groundwater include pathogens, nitrogen, chloride, sulphate, heavy metals, dissolved organics, and fuels. Major pollution sources are:
Surface water pollution affects rivers, lakes, ponds, and reservoirs. Most of this pollution originates from human activities like:
Pollutants include untreated drain water, pesticides, herbicides, bacteria, industrial effluents, and fertilizers like nitrates and phosphates. These substances are often washed into water bodies via stormwater runoff and poor waste management.
Ocean pollution stems from both anthropogenic and natural sources. Human-induced causes include:
Natural sources such as volcanic eruptions and erosion contribute as well. Major pollutants include:
An estimated 6 million pounds of plastic and garbage enter oceans annually, severely affecting marine biodiversity.
Contaminated water is a leading cause of diseases like cholera, jaundice, dysentery, and diarrhea. Toxic elements like heavy metals and pesticides severely impact both human and animal health.
Biodegradation by microorganisms consumes dissolved oxygen in water. Organic and inorganic pollutants contribute to high Biochemical Oxygen Demand (BOD), thereby reducing oxygen levels crucial for aquatic life.
Common pollution sources include sewage, tanneries, sugar mills, distilleries, food processing units, and agro-based industries, all of which disrupt the ecological balance of aquatic environments.
Soil pollution comprises the presence of human-induced chemicals and other modifications in the soil. Human activities like the use of fertilizers, insecticides, and pesticides are major contributors that deteriorate soil quality. Other activities such as mining, agriculture, and deforestation are highly energy-intensive and directly or indirectly impact the soil.
Modern agricultural methods often involve the excessive use of fertilizers and pesticides. Additionally, solid waste disposal, leachate from landfill sites, and direct waste discharge into the soil are primary causes of pollution. This degradation can have serious consequences for humans, animals, plants, and water resources.
If garbage is not properly segregated into organic and recyclable components, the harmful effects become disastrous. Contaminated soil may cause various types of cancer, respiratory issues, and skin diseases. Landfill sites can produce foul odors and serve as breeding grounds for mosquitoes, flies, rats, and other vectors of diseases, potentially triggering epidemics.
Mining of coal and metallic ores contributes significantly to soil contamination. Industries involved in ore processing, oil and gas drilling, or coal burning generate hazardous wastes such as sodium, calcium, sulfate, chloride, and carbonate.
Deforestation refers to the clearing of trees and transforming forest land for other uses. This results in negative impacts such as soil erosion, loss of biodiversity, and decreased water-holding capacity of soil. The loosened soil particles increase erosion risks significantly.
Soil acids occur naturally but increase with the use of acid-forming fertilizers. High salinity adversely affects soil structure, microbial diversity, and plant health. It can be measured using the electrical conductivity of saturated soil samples. Salinity reduces soil productivity and contributes to environmental degradation.
Soil erosion is a natural but human-accelerated process where the topsoil layer is removed by water and wind. Chemicals like preservatives, pesticides, and fuels absorbed by the soil degrade its composition and quality.
While fertilizers are crucial for enhancing crop yield, their components—including nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and trace elements like zinc (Zn), iron (Fe), and copper (Cu)—must be carefully managed. Excessive application of any single nutrient hampers productivity and contributes to soil pollution.
Synthetic pesticides are extensively used in modern agriculture. While they help in boosting production, they significantly alter soil chemistry and nutrient composition.
High concentrations of animal waste can degrade soil quality. Additionally, overgrazing by animals disrupts soil composition and structure.
Plants grown in polluted soils transfer contaminants to humans, causing muscle blockages, skin infections, and nervous system disorders. Pollution can indirectly cause food poisoning through contaminated crops. High concentrations of mercury and lead may lead to kidney and liver diseases.
Polluted soil emits volatile compounds into the air, leading to air contamination. Hazardous substances may also leach into groundwater and pollute surface runoff, affecting nearby lakes, rivers, and oceans.
Salt accumulation in the soil—a process known as salinization—is intensified by improper agricultural practices. Irrigation runoff carrying nitrates and phosphates raises salinity levels, reducing soil moisture absorption and contributing to groundwater contamination.
Research shows that oceans are now 10 times noisier than they were 40 years ago. This rise in noise levels can significantly harm the stability of human and animal life. Noise pollution is mainly generated from sources such as loud music, mobile phone conversations, machinery, transportation systems, vehicles, trains, aircrafts, and poorly planned urban infrastructure. Even household electrical appliances contribute to noise through constant beeping and buzzing sounds.
Understanding the root causes of noise pollution is essential to prevent potential health hazards.
Overcrowded housing, shared living spaces, and conflicts over limited resources like parking often lead to loud disputes. These everyday urban challenges contribute significantly to environmental and social noise levels.
Social events—from parties and weddings to discos and religious gatherings—often peak with extremely high noise levels. In local markets, vendors shout to attract attention, and playing music at high volume late into the night worsens living conditions for nearby residents.
Industries rely on heavy machinery such as generators, compressors, grinding mills, and exhaust fans, all of which are major contributors to industrial noise pollution.
Common electronic devices—like mobile phones, televisions, pressure cookers, mixers, washing machines, vacuum cleaners, coolers, and air conditioners—create noise that adds to pollution both inside and outside homes.
The large volume of vehicles, airplanes flying over populated areas, and underground trains generate considerable noise. Prolonged exposure to such noise can impair hearing ability, even in healthy individuals.
Exposure to excessive noise in offices, construction sites, bars, and even homes can severely affect mental and psychological well-being. Studies have linked high noise levels to aggressive behavior, sleep disturbances, chronic stress, fatigue, and hypertension, particularly in elderly populations.
Loud noise disrupts sleep patterns, leading to fatigue and reduced productivity. Both humans and animals suffer from irritation and restlessness due to sleep deprivation caused by constant noise.
Excessive background noise makes it difficult for individuals to communicate effectively. Persistent exposure can cause headaches and emotional instability, impacting social interaction and mental health.