Environmental Pollution
Environmental Pollution refers to excess output/discharge of any material into the environment in amounts which are harmful enough for humans, other life or valued assets of man like buildings.
Nearly all human activities produce wastes that eventually find their way into natural reservoirs. A reservoir or sink is a place of deposition and storage of earth, Ex. air, water and soil.
Once into these sinks, planet's ecosystems have natural capacity to assimilate the wastes. But human activities are generating wastes at an accelerated pace far outpacing the ability of ecosystems to assimilate the wastes. This disequilibrium between the rate at which waste is generated and rate at which waste is assimilated by the ecosystem is leading to generation of environmental pollution.
Therefore, environmental pollution can be understood as:
i. Pollution as local concentrations in matter cycling
All ecosystems consist of biogeochemical cycling of matter. Pollution represents accumulation of matter in harmful concentrations at some stage of matter cycling. For example, soil contamination by nutrients due to over application of chemical fertilizers in agriculture.
ii. Pollution as an accelerated natural process
Human activities accelerate the pace of matter cycling and this causes generation of matter at toxic concentrations. For example, burning of fossil fuels releases tonnes of carbon into the atmosphere that was stored as Coal or petroleum underground. Had it not been for human consumption of fossil fuels, these would have taken millions of years to recycle.
Environmental pollutant is excess of any biological, physical or chemical substance that is potent enough to be harmful to life in some form.
Types of Environmental Pollution
Pollution has become a widespread problem affecting all the natural sinks of planet. Based upon the occurrence of sink, major types of environmental pollution are:
- Air Pollution - It is the accumulation of gaseous, particulate wastes and toxic compounds in atmosphere. It is of two types - indoor air pollution and ambient (outdoor) air pollution.
- Water Pollution - It is defined as degradation of water quality such that it is rendered unusable for its intended purpose. It can be either surface water pollution or ground water pollution.
- Soil Pollution - It is the presence of chemicals in soils which are either out of place or higher than normal concentrations.
Sources of Environmental Pollutants
Waste generation has become a by-product of human living post industrial revolution. Major sources of environmental pollutants are:
- industrial Sources - Major industries contributing to pollution are manufacturing; power generation like coal-based power plants; mining, and construction. Different industries, based upon their nature, can cause air, water or soil pollution.
- Vehicular Sources - Petrol and diesel-based automobiles like cars, heavy-duty trucks, passenger vehicles all generate toxic exhaust fumes. Vehicular emissions are mainly responsible for air pollution.
- Agricultural Sources - Agricultural operations like cultivation of crops and animals generate agricultural wastes. These are rich in nutrients like nitrogen and phosphorous. They may enter into water streams as agricultural run-off or stay in land causing soil pollution.
- Domestic Sources - These include households which generate sewage rich in nitrogen and phosphorous causing water pollution.
These sources of environmental pollutants can be broadly classified as -
| Pollutants from Point Sources | Pollutants from Area Sources/Non-Point Sources |
|---|---|
| These are discharged/produced from a single, identifiable source of pollution (such as a discharge pipe). | These are more diffused, difficult to isolate and identifu and discharge pollutants from many pollutants. |
| For example - smoke from smokestacks causing air pollution; pipes from industries discharging industrial effluents into river; sewage pipes discharging into rivers etc. | For example - agricultural run-off causing water pollution; acid precipitation. |
Some Important Terms - Toxic Heavy Metals, Persistent Organic Pollutants (POPs), Bio persistence, Bioaccumulation and Bioconcentration or Biomagnification
1. Toxic Heavy Metals
These are the metals with relatively high atomic weight which pose health hazards to people and ecosystems. Heavy metals like mercury attack the nervous system. Examples include mercury lead, cadmium, nickel, gold, platinum, arsenic etc. The heavy metals find application in industries. They can be a by-product of mining or industrial refining.
2. Persistent Organic Pollutants (POPs)
These are those pollutants which don't break down easily and remain in the environment for a long time. Most of these are manufactured by humans as synthetic chemicals and have carbon-based molecular structure. As these are persistent in the environment, they tend to accumulate in living tissues. A few common POPs include:
| Chemical | Used As |
|---|---|
| Polychlorinated Biphenyls (PCBs) | Liquid insulators in electric transformers |
| DDT | lnsecticide |
| Aldrin | lnsecticide |
| Dioxins | By-product of herbicide production |
3. Bio persistence
It is defined as the time duration for which a waste material remains in the biosphere.
4. Bioaccumulation
It is defined as the concentration of a toxic substance in various tissues of a living organism. It takes place within an organism when the rate of intake of a substance is higher than the rate of excretion or metabolism of that substance.
5. Biomagnification or Bioconcentration
It is the increase in concentration of a harmful substance in living tissue as it moves through the food chains and webs. It involves two steps. First, an organism takes in the substance but does not metabolize or excrete it. Then, a predator eats that organism, and, in the process, the harmful substance climbs up the food chain. The second step is common in fishes, shellfishes, carnivores like eagles etc.
For example - Cadmium is a toxic heavy metal which poses a risk of heart disease. It is present in very low concentrations in ash produced by burning coal in power plants. This, cadmium may easily enter the environment as ash is usually disposed off in a landfill.
The landfills may be covered with soil and revegetated. As some plants grow over the soil of landfill, cadmium enters the food webs. The concentration of cadmium in the plants is 3-5 times greater than the concentration in the ash. The herbivores which eat these plants will have even higher concentration of cadmium.
Similarly, in aquatic ecosystems, mercury undergoes biomagnification. Natural sources of mercury in the environment include volcanic eruptions and erosion of natural mercury deposits. And the human sources include burning coal in power plants, incinerating waste, and processing metals like gold. In mid-twentieth century a significant incident of mercury poisoning occurred due to industrial release of release methyl mercury in Minamata Bay (Kyushu Island), Japan for detailed discussion on Minamata poisoning).
These two terms, bioaccumulation and biomagnification are also used interchangeably.
Air Pollution
Over the years, air pollution has become the greatest environmental challenge being faced by people, especially in urban areas. Most often, it is caused by human activities like burning of fossil fuels in thermal power plants, other industrial processes like petroleum refining, smelting, mining, construction, transportation, agriculture etc. In addition to human sources of air pollution, it can also be caused by natural processes. For example, volcanic eruptions release Sulphur dioxide (SO2) and other pollutants, which react in the atmosphere to produce volcanic smog, called as 'Vog'.
Air pollution can occur at various scales, from local to regional.
i. Local air pollution - This occurs at a small spatial scale. For example, indoor air pollution caused due to use of unsafe cooking fuel like wood by poorer households in India, is a type of local air pollution.
ii. Regional air pollution - It is generally caused by running of industries, thermal power plants and vehicles. It is mostly a problem of urban areas of the world. However, in developing countries like India, burning of crop residue after harvest is also a major contributor to regional air pollution. There have been two recent examples where large-scale forest fires (Brazil's forest fires of 2019 and Australian bush fires of 2019-2020) caused regional air pollution.
Major Air Pollutants and their Effects
Based upon origin, air pollutants can be classified as Primary and Secondary.
| Primary Pollutants | Secondary Pollutants |
|---|---|
| These are emitted directly into the air. | These are produced through reactions between primary pollutant and normal atmospheric compounds. |
| Examples - carbon monoxide, nitrogen oxides, sulphur dioxide, particulate matter. | Examples - ozone, smog, photochemical pollutant. |
Major air pollutants, their sources and impacts are:
1. Pollutant
Sulphur dioxide (SO2)
Description
Colourless, odourless gas
Sources
Burning of fossil fuels, mostly coal in thermal power plants; Industrial processes like petroleum refining, cement production etc.
Effects
Increase in chronic respiratory diseases and asthma causing shortness of breath.
Bleaching of plant leaves and decay and death of plant tissue; stunted growth of plants.
If oxidized to acid rain it corrodes metals, damages buildings and monuments.
2. Pollutant
Nitrogen Oxides (NOx)- nitrous oxide (N2O), nitric oxide (NO) and nitrogen dioxide (NO2) are major forms
Description
Most are colourless. NO2 is reddish-brown and odourless. N2O has a slightly sweet odour.
Sources
Nitrogen oxides (N2O, NO & NO2) are generated by automobile exhaust and power plants which burn fossil fuels.
Nitrous oxide (N2O) is also generated by application of nitrogen-based fertilizers in agriculture.
Effects
Cause smog formation: Mostly non-irritating gases but aggravate symptoms of asthma and bronchitis.
If oxidized to nitric acid (acid rain) it damages buildings and monuments.
N2O is a potent green house gas and causes global warming.
NO and NO2 form ozone through chain of chemical reactions.
Tropospheric ozone is a greenhouse gas.
3. Pollutant
Carbon Monoxide (CO)
Description
Colourless and odourless gas
Sources
Incomplete combustion of fuels in fires, automobiles and other organic compounds.
Effects
Reduces the ability of circulatory system to transport oxygen; causes headache, fatigue, nausea; may be lethal causing asphyxiation
4. Pollutant
Ozone (a pollutant in troposphere and forms primary constituent of photochemical smog)
Description
colourless with slightly sweet odour. A type of photochemical oxidant formed on bright, sunny days in areas with high primary pollution.
Formed when carbon monoxide, methane or other Volatile Organic Compounds (VOCs) are oxidized in presence of nitrogen oxides and sunlight.
Sources
Automobiles, fossil fuel burning and industrial processes which produce NO and NO2.
Effects
Strong eye irritant; lung problems like coughing, chest discomfort; aggravates asthma.
Cracks rubber, reduces durability of paint.
5. Pollutant
Particulate Matter (PM 2.5, PM 10)
Description
Composed of sulphates, nitrates, sodium chloride, black carbon, mineral dust etc.
PM 2.5- is less than 2.5 micrometer in diameter.
PM 10- is less than 10mm in diameter.
Sources
Mining, construction, agriculture, vehicles, volcanic eruptions etc.
Effects
Increased chronic and acute respiratory diseases; Irritates eyes, throat, nose and lungs.
Damages trees and crops.
Accelerates metal corrosion, damages paint.
Scatter light, reducing visibility and also cause global dimming.
6. Pollutant
Volatile Organic Compounds (VOCs)
Desecription
Include wide variety of hydrocarbon molecules used in industrial processes like dry cleaning, degreasing etc.
Examples of hydrocarbon compounds include natural gas or methane, butane etc.
Sources
Industrial processes
Effects
Toxic to life through conversion into photochemical pollutants.
Particulate Matter
It is a varying mixture of particles (solid or liquid) less than 10mm suspended in air. Mining, construction, agriculture, vehicles, volcanic eruptions etc. add
considerable particulates into the atmosphere. Some of these are visible as smoke, soot or dust; while others may not be easily visible. of particular concern are PM 2.5 and PM 10 as these can be easily inhaled into the lungs and can be absorbed into bloodstream. Such particulate matter is called as Respirable Particulate Matter.
Photochemical Pollutants
These are produced when sunlight starts complex chemical reactions among NOx, VOCs and other components of air. Different types of photochemical pollutants can be formed through these reactions which can be summarised as:
VOCs + NOx, + Sunlight = Photochemical Pollutant
These can cause irritation of eyes, lungs and other mucous membranes in humans and rest of animal life. In plants, it causes stunted growth and death.
Sulphates and Nitrates - These are most significant particulate pollutants. These are secondary atmospheric pollutants produced through chemical reactions between atmospheric compounds and sulphur dioxide and nitrogen oxides.
Black Carbon - It is produced during incomplete combustion of fossil fuels. It is a Short Lived Climate Pollutant (SLCP). SLCPs persist in atmosphere for a shorter period as compared to carbon dioxide. But black carbon is one of the largest contributors to global warming after CO2.
Some Forms of Air Pollution - Acid Rain, Smog and Global Dimming
1. Acid Rain/Acid Precipitation
It is the precipitation with pH less than 5.6, that is more acidic than normal rain. Even normal rain is slightly acidic with average pH of 5.6, as water combines with naturally occurring carbon dioxide in the air thus forming weak carbonic acid. It includes both:
- i. Wet acidic depositions - This can be in form of acid rain or acid for or even acid snow can occur in colder areas.
- ii. Dry acidic depositions - These are acidic particulate matter.
It is formed majorly by sulphur dioxide or nitrogen oxides present in air which combine with water to form much stronger sulphuric acid or nitric acid respectively. Although these oxides are the main contributors to acid rain, other acids like hydrochloric acid may also be involved.
It causes damage to the biological environment of forests, lakes etc. and also physically damages buildings, causes paint discoloration, metal corrosion etc.
2. Smog
The term 'Smog' was first used in 1905 for mixture of smoke or soot and fog that produced unhealthy air. There are two types of fog:
- i. Photochemical Smog/Brown Air
- ii. Sulphurous Smog/Gray Air
| Photochemical smog/Brown Air | Sulphurous Smog/ Gray Air |
|---|---|
| Formed by reactions between Nitrogen Oxides (NOx) and Volatile Organic Compounds (VOCs). | Formed by combination of sulphur oxides and particulates under certain particulate conditions. |
| As nitrogen oxides are emitted by vehicles mostly, the development of photochemical smog is directly related to automobile use and traffic pattern. | As sulphur is present in coal as impurity, sulphurous smog is produced primarily by burning of coal or oil at large power plants. |
| Ozone is a major constituent of photochemical smog. | Sulphurous smog doesn't contain ozone. |
Formation of smog is affected by local meteorological conditions, like wind speed, direction and temperature. For example, during the winter months when wind speeds are low, it helps the smoke and fog to stagnate at lower levels of troposphere in northern regions of India.
Smog can have hazardous health impacts. Minor exposure to smog can cause eye irritation, cause inflammation of lung tissue thus aggravating asthma and breathing difficulties.
Ground level ozone in the smog inhibits plant growth and causes immense damage to crops and forests.
Global Dimming
It is the process of gradual reduction in the solar energy that reaches the Earth's surface due to particulate air pollution. It cools the atmosphere and has lessened the effects of global warming.
Air Pollution and Health
With large scale urbanisation and industrialisation in present times, the challenge of air pollution has assumed unprecedented dimensions. World Health Organisation (WHO) calls it as an invisible killer that lurks around, attacking body's defences and causing mortality from heart attacks, strokes, lung diseases and cancer. As per Global Air Pollution Database (for 2016) released by WHO in May 2018:
- 91% of the world's population lives in places where air quality exceeds WHO guideline limits.
- 97% of cities in low and middle-income countries with more than 100,000 inhabitants do not meet WHO air quality guidelines. However, in high-income countries, that percentage decreases to 49%.
- 4.2 million death occur every year as a result of exposure to ambient (outdoor) air pollution.
- 3.8 million death occur every year as a result of household exposure to smoke from dirty cookstoves and fuels.
This means that outdoor and indoor air pollution together kill more than 7 million people every year globally.
WHO has set International Standards for Air Quality by recommending limits of key air pollutants for both outdoors and inside buildings and houses. For ambient (outdoor air pollution), the guidelines were set in 2005. Pollutants covered for outdoor air pollution are annual and daily concentrations of fine particulates, nitrogen dioxide, Sulphur dioxide, carbon monoxide and ozone.
International Standards for Outdoor Air Quality by WHO
| Time Period | PM 2.5 | PM 1O |
|---|---|---|
| Annual mean (in microgram/metre cube) | l0 | 20 |
| 24-hour mean (in microgram/metre cube) | 25 | 50 |
Recently in 2014, WHO has also set guidelines for indoor air quality.
Air Pollution Control and Abatement
There are exist two basic strategies for controlling air pollution to reduce the generation of air pollutants or to collect, capture and retain the pollutants before they enter the atmosphere.
Following are the major ways to achieve this:
1. Control of pollutants like carbon monoxide, nitrogen oxides and hydrocarbons in urban areas is achievable through pollution control measures for automobiles.
It will also limit ozone formation in lower atmosphere. Clean fuel based public transport systems like Compressed Natural Gas (CNG) buses or metro rail also help in substantial reduction of emissions. Public transport systems like Bus Rapid Transport (BRT) systems have proved to be effective in reducing vehicular pollution in cities. Globally cities like Curitiba (Brazil), Bogota (Colombia) have
successful examples of BRT systems. In India, BRT systems run in cities like Bhopal, Indore and Ahmedabad. Hybrid cars and electric engines offer another innovative means for emission control.
2. As the main source of sulphur dioxide emissions is burning of sulphur rich coal, so using low-sulphur coal is an obvious solution. A few techniques for this are:
- Cleaning up relatively high-sulphur coal to remove sulphur. In this, coal is washed with water. Iron sulphide settles out due to its relatively high density. But cleanup of coal by washing has only limited effectiveness as it removes sulphur only partially.
- Coal Gasification - which converts coal that is relatively high in sulphur to a gas in order to remove the sulphur. The gas obtained from coal is quite clean to use.
- Flue Gas Desulphurization - Sulphur dioxide emissions from power plants can be reduced by removing the oxides from the emissions in the chimney stack before they reach the atmosphere. The SO2 rich gases are chemically treated with a slurry (a watery mixture) rich in lime. The sulphur oxides react with calcium to form calcium sulphite, which is collected and disposed off. This process is also called as Scrubbing.
3. Super Critical Technology based coal Power Plants - These power plants operate at higher temperature and pressure than traditional power plants. Thermodynamically, such power plants operate at pressure and temperature above critical point of water. This results in better thermal efficiency of power plants and reduced fuel consumption. Improved efficiency also means fewer emissions of GHGs and pollutants like NOx, SOx and particulate matter.
4. Emphasis on clean energy sources like solar and wind to reduce dependence on fossil fuel burning for generating electricity.
5. Particulate pollution control can be done through variety of settling chambers or collectors. The collectors have a mechanism which causes particles in gases to settle out in a location where they can be collected for disposal. This is an effective way to control particulate pollution from power plants and industry.
Water Pollution
Mankind has long dumped its wastes into natural waters because the waste can be quickly diluted and dispersed. As the human population grew, the waste disposed into rivers far outpaced the ability of natural streams to cleanse themselves. This has made water pollution as one of the greatest problems in the world today. It is highly costly in the effects it has on health of people and ecosystems.
Types of Water Pollution:
| Surface Water Pollution | Ground Water Pollution |
|---|---|
| Contamination of rivers, natural streams, lakes, canals, wetlands etc. | Contamination of sub-surface ground water aquifers. |
Some sources include:
|
Some sources include:
|
Major Water Pollutants and their Effects
Biochemical Oxygen Demand (BOD)
Dead organic matter like plant and animal waste in water streams gradually undergoes decomposition. Bacteria carrying out this decomposition will require oxygen as it is Aerobic bacteria. Biochemical decomposition includes biological activity like respiration by bacteria and chemical processes like natural oxidation.
The amount of oxygen required for biochemical decomposition process in a water body is called Biochemical Oxygen Demand (BOD).
If the bacterial activity increases enough, the oxygen dissolved in the water (or dissolved oxygen) available to fish and other organisms can be reduced to so low levels that they may die. A stream with an inadequate dissolved oxygen (DO) level is considered polluted.
BOD is commonly used as an indicator of water quality. It measures the amount of oxygen consumed by microorganisms as they break down organic matter in water. It is most commonly expressed in milligrams of oxygen consumed per Liter (mg/L). If the BOD level is higher than 3mg/L, the water is unfit for drinking.
Some Forms of Water Pollution - Eutrophication, Harmful Algal Blooms (HABs) and Acid Mine Drainage
1. Eutrophication
It is the process by which a body of water develops a high concentration of nutrients, such as nitrogen and phosphorous resulting in abundant plant growth.
(Greek eu = good; trophikos = food, so 'good food' is the literal meaning)
A lake with naturally high concentration of nutrients needed for life is called a Eutrophic Lake. Whereas a lake with a relatively low concentration of nutrients required for life is called an Oligotrophic Lake.
In freshwater systems, phosphorous is generally a limiting nutrient. In marine waters, the limiting nutrient usually is nitrogen. Limiting Nutrient is one which limits plant growth. If large amount of limiting nutrient is suddenly available, plant populations will increase rapidly. Fertilizers and human sewage are rich in both nitrogen and phosphorous (in form of nitrates and phosphates). The nutrients cause an increase in growth of aquatic plants and production of photosynthetic blue-green bacteria and algae. Algae proliferate forming surface mats on water called as 'Algal bloom'. Algal blooms reduce the light penetration to below the surface and greatly reduce photosynthesis. As the bacteria and algae die, their decomposition increases the BOD of water. If the dissolved oxygen is sufficiently lowered, then other organisms like fishes will also start dying.
Whenever eutrophication is accelerated by human activities which add nutrients to water bodies, it is called as Cultural eutrophication.
2. Harmful Algal Blooms (HABs)
HABs are the large colonies of algae and other photosynthetic organisms proliferate uncontrollably in oceans, brackish water or freshwater water bodies. They affect oceans and other water bodies like ponds, rivers, streams, lakes, and even reservoirs. They are caused by various photosynthetic organisms, like toxic phytoplankton, cyanobacteria (cyanobacteria are microscopic organisms that do photosynthesis in aquatic ecosystems), micro-algae, benthic algae and macro-algae. These algal blooms may be blue-green, red, brown or yellow in color. Thus, red tide is one type of HAB.
Major impacts of HABs are:
i. Such blooms produce toxins that can kill mammals, fishes, birds and other organisms. Toxins of HABs can contaminate food webs and can also cause human illness or death in extreme cases.
ii. Some algae are non-toxic, but they consume all the dissolved oxygen in the water. Such regions with depleted oxygen levels are called as Hypoxic zones which aren't able to sustain life. Thus, dead zones in water may be created where aquatic life cannot survive. Hypoxia means "Low Oxygen." In aquatic ecosystems, low oxygen usually means a concentration of less than 2-3 milligrams of oxygen per litre of water (mg/L). A complete lack of oxygen (0mg/L) is called Anoxia.
iii. Algae may also smother corals and block the sunlight availability for coral reef ecosystem thus affecting the health of coral reef ecosystems.
iv. Some algae may discolor water and contaminate drinking water.
HABs can occur both due to natural and human-induced factors. Increased nutrient discharge, mainly phosphorous and nitrogen, from agricultural runoff and untreated sewage can be a major driver of HABs. Apart from this, food web alterations, exotic species, changes in the water flow and climate change all play a role in HABs.
3. Acid Mine Drainage
It refers to water with a high concentration of sulphuric acid (H2SO4) that drains from coal and metal (copper, lead, zinc etc.) mines. Coal is associated with a mineral known as Pyrite, i.e, Iron Sulphide (FeS2). Pyrite undergoes chemical weathering upon coming in contact with oxygen and water and sulphuric acid is produced. The acid can seep into ground water or enter surface water streams through runoff. The acidic water is toxic to aquatic life and damages biological productivity. Improperly abandoned mines can cause similar problems.
Water Pollution Control and Abatement
There are three major ways of slowing and managing water pollution.
1. Source Reduction of Waste
It means producing less waste from input sources of pollution like industries and households. It is least costly and environmentally most benign method of slowing water pollution.
2. Wastewater Treatment
In this, wastewater from industries, cities and households is treated before discharge into natural streams. There can be multiple techniques of water treatment-
- Chlorination - It kills micro-organisms such as harmful bacteria and disinfects water.
- Septic-Tank Sewage Disposal System - This is deployed in areas with no central sewage treatment facilities. The sewer lines carry waste water from households to a septic-tank. The tank is designed to separate solids from liquids. The wastewater is then biochemically treated before disposal into natural water streams.
- Wastewater Treatment Plants - These are specially designed plants to treat municipal sewage from homes, businesses and industrial sites. The raw sewage is delivered to the plant through network of sewer pipes. The wastewater treatment is a three step process - primary treatment, secondary treatment and advanced treatment. Following treatment, the wastewater may be discharged into natural water streams or used for crop irrigation.
- Nanotechnology - In this, use of nano-particles is done. These can capture heavy metals such as lead, mercury and arsenic from water.
3. Remediation
This means cleaning up natural water streams like rivers, lakes, groundwater etc. after they have been polluted. Although it is much more expensive
than reducing pollutant input or wastewater treatment before discharge, it is sometimes the only option.
For example -
i. Groundwater can be treated with microbes to decompose organic pollutants.
ii. Lake acidity caused by acid rain can be treated with chemical bases such as lime. Lime is disseminated in the lake to neutralise acidity.
Plastic Pollution
If there is one type of waste problem, which is ubiquitous, it is Plastic Pollution. A few important facts about plastic pollution as per United Nations Environment Program (UNEP):
1. Since the early of 1950s, more than 8.3 billion tonnes of plastic has been produced. Only 9% of all plastic waste ever produced has been recycled and about 12% has been incinerated. About 60% of that plastic has ended up in either a landfill or the natural environment.
2. About 8 million tonnes of plastic end up in the world's oceans every year. Rivers carry plastic waste from deep inland to the sea. This contributes to marine pollution. Rivers like Ganga, Brahmaputra, Indus, Mekong, Yellow, Yangtze, Amur, Nile and Niger are some of the major rivers carrying plastic waste to oceanic environment.
3. Globally about 300 million tonnes of plastic waste is generated every year. Half of all plastic produced worldwide is used only once and then trashed away. Most common examples of single-use plastics are cigarette butts, plastic drinking bottles, plastic bottle caps, food wrappers, plastic grocery bags, plastic lids, straws and stirrers, and foam take-away containers.
4. Plastic pollution has become an all-pervasive problem, with some scientists suggesting that it could serve as a geological indicator of the Anthropocene era!
The developed countries like the United States, Japan and many European countries produce significant amounts of plastic waste. Per capita annual plastic consumption in the USA is about 100 kg, in Europe it is around 65 kg and in China is around 40 kg.
This is much higher than the global average of 28 kg of plastic use per person annually. (Note that the per capita plastic use in India is about 11 kg which is less than the global average.) However, developed regions like European Union, Japan and the USA are relatively good at managing plastic waste. The developing countries like China, Vietnam, Indonesia etc. are fast growing. As consumptions boom, the plastic waste generation also increases.
The most worrisome feature about plastic pollution is that it remains in the environment for centuries. Most plastics are non-biodegradable. Over time, they slowly break down into smaller fragments known as 'Microplastics'. These are extremely small plastic pieces which are less than 5 mm in size. Microplastics can come from multiple sources and can be either primary microplastic and secondary microplastic.
- Primary microplastics are tiny particles designed for commercial use. One example is of microbeads. These are very tiny pieces of manufactured polyethylene plastic that are added as exfoliants to health and beauty products, like cleansers and toothpastes.
- Secondary microplastics are those which are formed from larger plastic debris that degrades into smaller and smaller pieces. The breakdown can take place due to sun's radiation or action of ocean waves.
Environmental impacts of plastic waste are:
- Plastic bags can block waterways and exacerbate natural disasters like flooding. For example, one of the reasons of Mumbai flooding of 2019 was plastics clogging the drainage system of city.
- By clogging sewers, plastics provide breeding grounds for mosquitoes and pests. This was plastic bags can increase the transmission of vector-borne diseases like malaria.
- Plastic bags are often mistaken for food by turtles and dolphins. Marine organisms like dolphins, turtles, whales, fishes can ingest them and high concentrations of plastic materials, have been found blocking the airways and stomachs of hundreds of species.
- Microplastics are a bigger problem as it is easily ingestible by fish. This way, plastics eventually enter human food chains. Microplastics have been detected in marine organisms from plankton to whales, in commercial seafood, and even in drinking water.
- Styrofoam products are generally used for making disposable plastic cutlery like glasses, cups etc. It contains carcinogenic chemicals like styrene and benzene. These, if ingested, can damage the nervous systems, lungs and reproductive organs. The toxins in Styrofoam containers can leach into food and drinks.
- Disposing of plastic waste by burning it in open-air pits releases harmful gases like furan and dioxin.
To tackle the plastic waste menace, the theme of UNEP's World Environment Day (5 June) 2018 was 'Beat Plastic Pollution'. The World Environment Day 2018 was hosted by India.
The objective was to build momentum to fight plastic waste problem globally. Over here, India for first time made a commitment that it will ban all single-use plastic by 2022. However, later at the United Nations Environment Assembly's meet (September 2019) this was revised and India committed to reducing plastic use by the year 2030.
Recommendations offered by the UNEP to policy makers to tackle plastic pollution were:
- Governments need to improve waste management practice. They may introduce financial incentives to change the habits of consumers, retailers and manufacturers.
- Promote eco-friendly alternatives to plastics. Examples include biodegradable cutlery, bamboo straws used in India.
- Strong Government policies are needed for encouraging circular model of economy which places emphasis on reuse and recycle.
- Educate consumers to enable voluntary plastic reduction strategies.
- Successfully implement bans or levies on the use and sale of single-use plastics. Countries like Kenya, Botswana, Peru and Chile have already done that.
Later in September 2018, the UNEP along with European Union (EU) also launched Global Plastics Platform to reduce plastic pollution.
It is a network of member states to support countries and cities in establishing policies to reduce plastic pollution. Support will be provided for the transition to a more circular economy.
Municipal Solid Wastes and Hazardous Wastes
Municipal solid waste is a general term used for combination of solid, semi-solid wastes generated from household and even commercial activities like various businesses and institutions. Examples include household garbage like paper, food wastes, plastics, metals, rubber, leather, textiles, wood, glass, etc.
Hazardous wastes include substances that are chemically reactive, flammable, explosive or toxic to living organisms. These are the substances that can cause serious, irreversible health effects or present substantial danger to the environment upon exposure. Examples include -
- E-wastes with heavy metals like lead, cadmium, mercury.
- Pesticides like DDT.
- Petrochemicals like benzene (sourced from detergent production), vinyl chloride (sourced from plastic production).
- Radioactive wastes.
- Dioxin - It is a man-made toxic Persistent Organic Pollutant. It is a colourless organic chemical made up of oxygen, hydrogen, carbon and chlorine. About 75 types of dioxin are known. They are distinguished from one another by the arrangement and number of chlorine atoms in the molecule. Dioxin is by-product formed during combustion of organic compounds containing chlorine.
- Main sources of dioxin are: herbicide production, burning of plastics, burning of gasoline and diesel in vehicles, copper refining, burning of wood as a fuel etc. It is a potent human carcinogen, causes skin eruptions, birth defects and digestive disorders.
Both solid wastes and hazardous wastes have grown phenomenally over the years with rapid urbanisation, industrialisation and population growth. As these pose dangers for the environment and human health, scientific disposal of the wastes is essential for human and ecological well-being. As the two categories of wastes differ in nature, the waste treatment techniques also vary for both these types of wastes.
Solid Waste Management Techniques - Composting, Open Dumping, Sanitary Landfill and Incineration/Waste to Energy Plants
| Solid Waste Management Technique | Technique Explained and Features |
|---|---|
| Composting | Biochemical process in which organic waste like kitchen waste decomposes to a rich, soil-like material.
Involves rapid partial decomposition of most solid organic waste by aerobic organisms. |
| Open Dumps/Landfill | Landfills in which refused is piled up without any cover or protection. Can cause fire-outbreaks due to methane emissions; contribute to air and water pollution; provide breeding ground for pests. Remains the most common method of waste disposal in developing countries like India. |
| Sanitary Landfill | The wastes are confined to a specific dump area which is isolated from the surroundings by a cover. Covering the waste minimizes the surface water seeping into and gas escaping from the waste. Produces hazards like leachate and methane gas. |
| Incineration or Waste to Energy Plants (see below for types of Incineration) | The waste is burned at very high temperatures (900-1000°C) which consumes all combustible material leaving only ash and non-combustibles. Whatever is not burned is disposed off in a landfill. Large amount of heat generated from refuse burning is used to generate electric power. Produces air pollution, toxic ash and dioxin. |
Leachate - It is a noxious, mineralised liquid formed if waste buried in a landfill comes in contact with rainwater percolating down from the surface or with sub-surface groundwater. Upon such contact, an aqueous solution containing disease causing bacteria and other hazardous chemicals is formed. This can pollute the groundwater through downward percolation or the surface water through overland runoff into rivers. To prevent this, modern landfills are lined at the bottom with multiple barriers like clay and plastic liners.
Methane gas is produced as bacteria decompose certain organic material in the landfill. It can cause fire outbreaks if ignited. However, the scientific, landfills collect and sell this methane as a fuel.
In incineration, large amount of heat is generated which could be put to use. The Waste to Energy (WTE) plants perform exactly the same. There are two types of WTE plants:
- Mass-Burn Incinerators - The unsorted waste is burned at very high temperatures (900-1000°C). The heat generated from burring of refuse is recovered to produce steam that drives a turbine to generate electricity. Whatever is not burned is removed and disposed off in a landfill.
- Refuse Derived FueI (RDF) Facilities - The solid waste is sorted into various components like paper, wood and other combustibles, iron, steel and magnetic metals, glass, etc. Now recyclable materials are recovered, whereas combustibles are burned to generate electricity or formed into a fuel in form of pellets. The pellets are used as fuel in coal-powered plants. But, RDFs are often expensive to operate.
Hazardous Waste Management Techniques - secure Landfill, Deep Well Injection and Bioremediation
| Hazardous Waste Management Technique | Technique Explained and Features |
|---|---|
| Secure Landfill | Much like sanitary landfill, it is designed to confine the waste to a particular location, control the draining of leachate from the waste, collect and treat the leachate from the landfill.
No landfill could be completely secure, implying that some leakage always occurs from the landfill. |
| Deep Well Injection | Waste disposal involving injection of waste into deep wells drilled into Earth's crust. The deep well must be completely isolated from the fresh water aquifers.
For example - oil industry uses deep well injection to dispose liquid wastes like oil-field brine. Limited number of suitable sites for disposal is a limitation in widespread use of this method. |
| Bioremediation/Bio-treatment | Reduction in concentration or clean-up of toxic wastes using organisms like bacteria and fungi. Certain strains of bacteria and fungi can breakdown even highly dangerous chemicals like DDT, toxic nitrates, PCBs etc. through microbial breakdown to produce simpler, less toxic or non-toxic forms.
The micro organisms may be naturally occurring in a contaminated area or may be brought from elsewhere to the contaminated site. This method can be effective only where environmental conditions permit microbial growth and activity. For example - Bioremediation is used to treat organic petroleum waste of marine oil spills. |
International Conventions
These are three multi-lateral environmental agreements for management of hazardous waste, chemical and Persistent Organic Pollutants (POPs) worldwide.
1. Basel Convention on the Control of Trans-boundary Movements of Hazardous Waste and their Disposal
Its objective is to regulate the movement of hazardous waste like e-waste and plastics from developed to less developed countries. The industrialised world countries had stringent environmental regulations for waste management sine 1970s onwards. Since 1970s and 1980s there was increased public resistance to the disposal of hazardous wastes in their own countries. This public movement became known as the NIMBY (Not In My Back Yard). This hiked the waste management costs in developed countries. Cheaper alternative was dumping waste in developing countries of Eastern Europe, Africa and Asia as the environmental regulations and enforcement mechanisms were less stringent here. This is a typical example of 'Toxic trade'. It was against this background that the Basel Convention was adopted in 1989 at Basel (Switzerland) and entered into force in 1992.
The objective of the Basel Convention is protection of human health and the environment from the adverse effects of hazardous wastes. The Convention covers toxic, poisonous, explosive, corrosive, flammable. ecotoxic and infectious wastes.
For example, it covers e-waste and plastic waste. However, Basel Convention does not cover radioactive waste in its scope. It also covers 'other waste' like household waste and incinerator ash.
The principal aims of the Convention are:
- Reduction of generation of hazardous waste at source and promotion of environmentally sound management of hazardous wastes.
- Restriction on the trans-boundary movements of hazardous wastes except where it is perceived to be in accordance with the principles of environmentally sound management.
- Minimize the quantities of waste that are transported and treating and disposing the wastes as near as possible to the place of generation of waste.
- Creating a regulatory system for trans-boundary movements of such wastes. It is based upon the concept of prior informed consent. This means that when two States are indulging in international trade, the exporting State must provide detailed information about the goods being traded to the importing State (and States in transit) before any export takes place. The movement of these goods will only proceed when all States concerned have given their written consent.
India is a Party to the Basel Convention and ratified it in 1992.
2. Rotterdam Convention on the Prior Informed Consent (PIC) Procedure for Certain Hazardous Chemicals and Pesticides in International Trade
It was adopted in 1998 at Rotterdam (Netherlands) and entered into force in 2004. It is jointly administered by the United Nations Food and Agriculture Organisation (FAO) and UN Environment (UNEP). It prescribes obligations on the importers and exporters of certain hazardous chemicals like pesticides and industrial chemicals.
These obligations include proper labeling of the hazardous chemicals and directions for safe handling of these chemicals. Parties to the Convention can make informed decisions about the chemicals they wish to import.
The objectives of the Convention are:
- To promote shared responsibility and efforts among parties in the international trade of certain hazardous chemicals. The Convention covers pesticides and industrial chemicals that have been banned by the Parties. This protects human health and the environment from potential harm.
- To contribute to the environmentally sound use of those hazardous chemicals, by facilitating information exchange about their characteristics, by providing for a national decision-making process on their import and export and by disseminating these decisions to Parties.
The Convention creates legally binding obligations for the implementation of the Prior Informed Consent (PIC) procedure. The PIC procedure is the mechanism for formally
obtaining the consent of importing Parties, as to whether they wish to receive future shipments of certain chemicals. These are the chemicals which are listed in Annex III of the Convention.
India is a Party to the Rotterdam Convention and ratified it in 2005.
3. Stockholm Convention on Persistent Organic Pollutants (POPs)
It's a global treaty to protect human health and the environment from POPs. These are the chemicals with following properties:
- They remain intact in the environment for long periods. Thus, they have long bio persistence.
- They become widely distributed geographically by long range transport.
- They accumulate in the fatty tissue of humans and wildlife by undergoing bioaccumulation.
- They have harmful impacts on human health or on the environment.
Chronic exposure to POPs can lead to serious and adverse health effects. POPs are carcinogenic and can also cause birth defects, and damages to the nervous system. They can also lead to dysfunctional immune and reproductive systems and higher susceptibility to disease.
Stockholm Convention calls for international action on three categories of POPs - pesticides, industrial chemicals, and unintentionally produced POPs. It was adopted in 2001 and entered into force in 2004.
Under the Convention, there are three Annexes categorising different POPs. These are:
- Annex A - This includes the chemicals that are listed for complete elimination from production, use, export and import. A few examples of chemicals in Annex A are Aldrin, Dicofol, Heptachlor etc.
- Annex B - This includes the chemicals that have restriction in use and production for specific purpose only. DDT (a common pesticide) is an example of chemical listed in Annex B of the Convention.
- Annex C - This has chemicals which have unintentional production. Examples include Polychlorinated Biphenyls (PCBs).
India is a Party to the Convention and ratified it in 2006. The Parties are required to take measures to eliminate or reduce the release of these POPs into the environment. Till the year 2019,26 chemicals are listed as POPs under the Stockholm Convention. Out of these. India has ratified only the 12 initially listed POPs.
Integrated Waste Management (IWM)
All the waste treatment methods discussed as part of solid waste or hazardous waste management techniques involve some kind of limitations. To overcome these disadvantages, a novel concept is dominant today in waste management, known as Integrated Waste Management. It is defined as set of methods involving 3R's - Reduce, Reuse, Recycle.
- Reduce - It refers to reducing the generation of waste in first place. It will involve reducing consumption and major life-style changes by all and most importantly by the developed countries. For example, simple changes like saying no to plastic straws and cutlery can make a big difference.
- Reuse - It involves reusing of products in the same form or modified form for multiple uses or other uses. For example - washing and re-using plastic containers, making cloth bags from old clothes. Usually, the people in developing and low-income countries are more efficient in reusing things.
- Recycle - It means using waste as a raw material for secondary industrial process. For example - recovering old aluminium cans, melting them down and using the recovered aluminium to manufacture new products.
The ultimate objective of IWM is to reduce the amount of waste generated that will be disposed or be treated eventually through any of the already discussed techniques.
Environmental pollution has become a globally pervasive problem. It is clear that the amount and types of wastes generated by human activities are beyond the capacity of natural ecosystems to process and detoxify. Environmental science has offered many scientific and technological solutions for pollution abatement. What's needed is a smart combination of solutions like waste reduction and treatments. However for this to happen, it requires massive awareness generation amongst all the stakeholders including industry, people and Government.
Thanks to many environmental think-tanks and organisations like the UN, awareness is on the rise. And this has encouraged many people to make positive changes for the pollution reduction. Next, robust environmental legislations in a country and their effective implementation are critical for reducing the global menace of environmental pollution.
Essential Concepts Review
- Environmental pollution is defined as excess output or discharge of any material into the environment in harmful amounts for life in general.
- Environmental pollution can be broadly understood as - local concentration in matter cycling in the planet's reservoirs or an accelerated natural process. Human activities are generating wastes at pace more than the ability of planet's ecosystems to assimilate wastes.
- Based upon the occurrence of sink, major types of environmental pollution are air, water and soil pollution.
- Major sources of environmental pollution, whether industrial, vehicular, agricultural or domestic. can be broadly classified as point and non-point sources of pollution.
- A few examples of extremely harmful environmental pollutants are toxic heavy metals and Persistent Organic Pollutants (POPs). lt is because they have a tendency to persist and bioaccumulate.
- Bioaccumulation is defined as the concentration of a toxic substance in various tissues of a living organism. Bioconcentration is defined as the increase in concentration of a harmful substance in living tissue as it moves through the food chains and webs.
- Over the years, air pollution has become the greatest environmental challenge being faced by people of urban areas globally. It is caused by either primary or secondary pollutants. Examples of primary pollutants are particulate matter, sulphur and nitrogen oxides. Examples of secondary pollutants are smog, ozone and photochemical pollutant.
- Some hazardous forms of air pollution are acid rain, photochemical smog and sulphurous smog.
- The incidence of air pollution is high world over with outdoor and indoor air pollution killing more than 7 million people globally.
- There are exist two basic strategies for controlling air pollution - to reduce the generation of air pollutants or to collect, capture and retain the pollutants before they enter the atmosphere.
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