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Soil Pollution, Solid Waste, Hazardous Waste, Electronic Waste

Soil Pollution

  • Soil pollution is defined as the ‘addition of substances to the soil, which adversely affects physical, chemical and biological properties of soil and reduces its productivity.
  • It is a build-up of persistent toxic compounds, chemicals, salts, radioactive materials, or disease-causing agents in the soil which have adverse effects on plant growth, human and animal health.

Causes and Sources of Soil Pollution

Plastic bags

  • They accumulate in soil and prevents germination of seeds. They stay in the soil for centuries without decomposing (non-biodegradable).
  • Burning of plastic in garbage dumps release highly toxic and poisonous gases like carbon monoxide, carbon dioxide, phosgene, dioxins and other poisonous chlorinated compounds.
  • Toxic solid residue left after burning remains in the soil. The harmful gases enter soils through chemical cycles.

Industrial sources

  • They include fly ash, metallic residues, mercury, lead, copper, zinc, cadmium, cyanides, chromates, acids, alkalies, organic substances, nuclear wastes
  • A large number of industrial chemicals, dyes, acids, etc. find their way into the soil.

Pesticides and fertilisers

  • Chlorohydrocarbons (CHCs) like DDT, endosulfan, heptachlor accumulate in soil and cause biomagnification. Some of these pesticides like DDT and endosulfan are banned by most of the countries.
  • Excessive use of chemical fertilisers reduces the population of soil-borne organisms and the crumb structure of the soil, productivity of the soil and increases salt content of the soil.

Other pollutants

  • Many air pollutants (acid rain) and water pollutants ultimately become part of the soil, and the soil also receives some toxic chemicals during weathering of certain rocks.
  • Radioactive elements from mining and nuclear power plants, find their way into the water and then into the soil.

Effects of soil pollution

  • Reduced soil fertility due to increase in alkalinity, salinity or pH.
  • Reduced nitrogen fixation due to the reduced number of nitrogen fixers.
  • Increased erosion due to loss of forests and other vegetation.
  • Runoff due to deforestation cause loss of soil and nutrients.
  • Deposition of silt in tanks and reservoirs due to soil erosion.
  • Health effects are similar to the effects of water pollution.
  • Ecological imbalance.

Solid Wastes

  • Solid wastes or municipal solid wastes generally comprise paper, food wastes, plastics, glass, metals, rubber, leather, textile, etc.
  • Open-burning reduces the volume of the wastes, although it is generally not burnt to completion and open dumps often serve as the breeding ground for rats and flies.
  • Sanitary landfills were adopted as the substitute for open-burning dumps. In a sanitary landfill, wastes are dumped in a depression or trench after compaction and covered with dirt every day.
  • Landfills are also not much of a solution since the amount of garbage generation especially in the metros has increased so much that these sites are getting filled too.
  • Also, there is a danger of seepage of chemicals, etc. from these landfills polluting the underground water resources.

Effects of Plastic Waste

  • Conventional plastics, right from their manufacture to their disposal are a major problem to the environment.
  • The land gets littered by plastic bag garbage and becomes ugly and unhygienic.
  • Conventional plastics have been associated with reproductive problems in both humans and wildlife.
  • Dioxin (highly carcinogenic and toxic) by-product of the manufacturing process is one of the chemicals believed to be passed on through breast milk to the nursing infant.
  • Burning of plastics, especially PVC releases dioxin and also furan into the atmosphere.
  • Dioxins are environmental pollutants. They belong to the so-called “dirty dozen” – a group of dangerous chemicals known as persistent organic pollutants (POPs).
  • The name “dioxins” is often used for the family of structurally and chemically related polychlorinated dibenzo para dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs).
  • Plastic bags can also contaminate foodstuffs due to leaching of toxic dyes and transfer of pathogens.
  • Careless disposal of plastic bags chokes drains, blocks the porosity of the soil and causes problems for groundwater recharge.
  • Plastic disturbs the soil microbe activity. The terrestrial and aquatic animals misunderstand plastic garbage as food items, swallow them and die.
  • Plastic bags deteriorate soil fertility as it forms part of manure and remains in the soil for years.

Industrial solid waste

  • Thermal power plants producing coal ash/fly ash;
  • The integrated iron and steel mills producing blast furnace slag;
  • Non-ferrous industries like aluminium, copper and zinc producing red mud and tailings;
  • Sugar industries generating press mud;
  • Pulp and paper industries producing lime mud;
  • Fertilizer and allied industries producing gypsum;

Plastic waste in road construction

  • Polyblend is a fine powder of recycled and modified plastic waste.
  • This mixture is mixed with the bitumen that is used to lay roads.
  • Blends of Polyblend and bitumen, when used to lay roads, enhanced the bitumen’s water repellent properties, and helped to increase road life by a factor of three.

Issues with treatment and disposal of solid waste

Open dumps

  • Open dumps refer to uncovered areas that are used to dump solid waste of all kinds.
  • The waste is untreated, uncovered, and not segregated. It is the breeding ground for flies, rats, and other insects that spread disease.
  • The rainwater runoff from these dumps contaminates nearby land and water thereby spreading disease.


  • It is a pit that is dug in the ground. The garbage is dumped, and the pit is covered with soil every day thus preventing the breeding of flies and rats.
  • After the landfill is full, the area is covered with a thick layer of mud, and the site can thereafter be developed as a parking lot or a park.
  • All types of waste are dumped in landfills, and when water seeps through them it gets contaminated and in turn, pollutes the surrounding area.
  • This contamination of groundwater and soil through landfills is known as leaching.

Sanitary landfills

  • Sanitary landfill is more hygienic and built methodically to solve the problem of leaching.
  • These are lined with materials that are impermeable such as plastics and clay and are also built over impermeable soil.
  • Constructing a sanitary landfill is very costly.

Incineration plants

  • The process of burning waste in large furnaces at high temperature is known as incineration.
  • In these plants, the recyclable material is segregated, and the rest of the material is burnt.
  • Burning garbage is not a clean process as it produces tonnes of toxic ash and pollutes the air and water.
  • At present, incineration is kept as the last resort and is used mainly for treating infectious waste.


  • It is a process of combustion in the absence of oxygen or the material burnt under a controlled atmosphere of oxygen. It is an alternative to incineration.
  • The gas and liquid thus obtained can be used as fuels.
  • Pyrolysis of carbonaceous wastes like firewood, coconut, palm waste, corn combs, cashew shell, rice husk paddy straw and sawdust, yields charcoal along with products like tar, methyl alcohol, acetic acid, acetone and fuel gas.


  • Composting is a biological process in which micro-organisms, mainly fungi and bacteria, decompose degradable organic waste into humus-like substance in the presence of oxygen.
  • This finished product, which looks like soil, is high in carbon and nitrogen and is an excellent medium for growing plants.
  • It increases the soil’s ability to hold water and makes the soil easier to cultivate. It helps the soil retain more plant nutrients.


  • It is also known as earthworm farming. In this method, Earthworms are added to the compost.
  • These worms break the waste, and the added excreta of the worms makes the compost very rich in nutrients.

Waste Minimization Circles (WMC)

  • WMC helps Small and Medium Industrial Clusters in waste minimisation in their industrial plants.
  • This is assisted by the World Bank with the Ministry of Environment and Forests acting as the nodal ministry.
  • The project is being implemented with the assistance of the National Productivity Council (NPC), New Delhi.
  • The initiative aims to realise the objectives of the Policy Statement for Abatement of Pollution (1992), which states that the government should educate citizens about environmental risks, the economic and health dangers of resource degradation and the real economic cost of natural resources.
  • The policy also recognises that citizens and non-governmental organisations play a role in environmental monitoring, therefore, enabling them to supplement the regulatory system and recognizing their expertise where such exists and where their commitments and vigilance would be cost effective.

Hazardous Waste

  • Any substance that is present in the environment or released into the environment causing substantial damage to public health and welfare of the environment is called hazardous substance.
  • Any hazardous substance could exhibit any one or more of the following characteristics: toxicity, ignitability, corrosivity or reactivity (explosive).
  • Thus, any waste that contains hazardous or very hazardous substance is called hazardous waste.
  • Hazardous wastes can originate from various sources such as household, local areas, urban, industry, agriculture, construction activity, hospitals and laboratories, power plants and other sources.

Stockholm Convention on Persistent Organic Pollutants

  • Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty.
  • Came into effective in 2004.
  • Aims to eliminate or restrict the production and use of persistent organic pollutants (POPs).
  • POPs are defined as “chemical substances that persist in the environment, bioaccumulate through the food web, and pose a risk of causing adverse effects to human health and the environment”.

Important Listed substances

  • Aldrin: Used as an insecticide
  • Heptachlor: Uses as a termiticide (including in the structure of houses and underground), for organic treatment and in underground cable boxes
  • Hexachlorobenzene: Use as a chemical intermediate and a solvent for pesticides
  • Endrin: Endrin has been used primarily as an agricultural insecticide on tobacco, apple trees, cotton, sugar cane, rice, cereal, and grains.
  • Polychlorinated biphenyl: PCB’s commercial utility was based largely on their chemical stability, including low flammability, and physical properties, including electrical insulating properties. They are highly toxic.
  • DDT: DDT is the best-known of several chlorine-containing pesticides used in the 1940s and 1950s.

Basel Convention

  • Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and Their Disposal.
  • An international treaty that was designed to reduce the movements of hazardous waste between nations.
  • Main goal is to prevent the transfer of hazardous waste from developed to less developed countries (LDCs).
  • It does not address the movement of radioactive waste.

Rotterdam Convention

  • Rotterdam Convention on the Prior Informed Consent Procedure for Certain Hazardous Chemicals and Pesticides in International Trade.
  • Multilateral treaty to promote shared responsibilities in relation to the importation of hazardous chemicals.
  • The convention promotes an open exchange of information and calls on exporters of hazardous chemicals to use proper labelling, safe handling, and inform purchasers of any known restrictions or bans.
  • Signatory nations can decide whether to allow or ban the importation of chemicals listed in the treaty.

Electronic waste | E-WASTE

  • The discarded and end-of-life electronic products ranging from computers, equipment, home appliances, audio and video products and all of their peripherals are popularly known as Electronic waste (E-waste).
  • E-waste is not hazardous if it is stocked in safe storage or recycled by scientific methods or transported from one place to the other in parts or totality in the formal sector.
  • The e-waste can, however, be considered hazardous if recycled by primitive methods.

Source and health effects

Particulars Source Health Effects
  • Used in glass panels and gaskets in computer monitors
  • Solder in printed circuit boards and other Components
  • Lead tends to accumulate in the environment and has high acute and chronic effects on plants, animals and microorganisms.
  • Occurs in SMD chip resistors, infra-red detectors, and semiconductor chips
  • Some older cathode ray tubes contain cadmium
  • Toxic cadmium compounds accumulate in the human body, especially the kidneys.
  • It is estimated that 22 % of the yearly world consumption of mercury is used in electrical and electronic equipment
  • Mercury is used in thermostats, sensors, relays, switches, medical equipment, lamps, mobile phones and in batteries
  • Mercury, used in flat panel displays, will likely increase as their use replaces cathode ray tubes
  • Mercury can cause damage to organs including the brain and kidneys, as well as the foetus.
  • The developing foetus is highly vulnerable to mercury exposure.
  • When inorganic mercury spreads out in the water, it is transformed to methylated mercury which bio-accumulates in living organisms and concentrates through the food chain, particularly via fish.
Chromium VI 29
  • Chromium VI is used as corrosion protector of untreated and galvanized steel plates and as a decorative or hardener for steel housings Plastics (including PVC): Dioxin is released when PVC is burned.
  • The largest volume of plastics (26%) used in electronics has been PVC. PVC elements are found in cabling and computer housings.
  • Many computer mouldings are now made with the somewhat more benign ABS plastics
  • Chromium VI can cause damage to DNA and is extremely toxic in the environment.
  • Barium is used in computers in the front panel of a CRT, to protect users from radiation
  • Studies have shown that short-term exposure to barium causes brain swelling.
  • Beryllium is commonly found on motherboards and finger clips
  • It is used as a copper-beryllium alloy to strengthen connectors and tiny plugs while maintaining electrical conductivity
  • Exposure to beryllium can cause lung cancer.
  • Beryllium also causes a skin disease that is characterised by poor wound healing and wart-like bumps.
  • Found in the plastic printer cartridge containing black and colour toners.
  • Inhalation is the primary exposure pathway, and acute exposure may lead to respiratory tract irritation. Carbon black has been classified as a class 2B carcinogen, possibly carcinogenic to humans.
Phosphor and


  • Phosphor is an inorganic chemical compound that is applied as a coat on the interior of the CRT faceplate.
  • The phosphor coating on cathode ray tubes contain heavy metals, such as cadmium, and other rare earth metals, for example, zinc, vanadium as additives. These metals and their compounds are very toxic.
Q. Due to improper/indiscriminate disposal of old and used computers or their parts, which of the following are released into the environment as e-waste?
  1. Beryllium
  2. Cadmium
  3. Chromium
  4. Heptachlor
  5. Mercury
  6. Lead
  7. Plutonium

Select the correct answer using the codes given below.

  1. 1, 3, 4, 6 and 7 only
  2. 1, 2, 3, 5 and 6 only
  3. 2, 4, 5 and 7 only
  4. 1, 2, 3, 4, 5, 6 and 7
  • Heptachlor is a Chlorohydrocarbon (CHC) which is used as an insecticide.
  • Plutonium is a radioactive metal and hence not used in computers.
  • So, the answer should not contain either 4) or 7).

Answer: b) 1, 2, 3, 5 and 6 only

E-Waste in India

  • India generates about 18.5 lakh metric tonnes (MT) of electronic waste every year, with Mumbai and Delhi-NCR accounting for the biggest chunk. The figure is likely to reach up to 30 lakh MT per year by 2018.
  • Bangalore, Chennai, Kolkata, Ahmadabad, Hyderabad, Pune, Surat and Nagpur are other important cities generating a substantial amount of e-waste.
  • Among the eight largest e-waste generating states, Maharashtra ranks first followed by Tamil Nadu (2nd), Andhra Pradesh (3rd), Uttar Pradesh (4th), Delhi (5th), Gujarat (6th), Karnataka (7th) and West Bengal (8th).

E-Waste in India E-Waste in India

  • Over half of the e-waste generated in the developed world are exported to developing countries, mainly to China, India and Pakistan, where metals like copper, iron, silicon, nickel and gold are recovered during the recycling process.
  • Unlike developed countries, which have specifically built facilities for recycling of e-waste, recycling in developing countries often involves manual participation thus exposing workers to toxic substances present in e-waste.

Heavy Metal Toxicity and Methods of Their Prevention

  • Toxic metals are dispersed in the environment through metal smelting industrial emissions, burning of organic wastes, automobiles and coal-based power generation.
  • Heavy metals can be carried to places far away from their source of origin by winds when they are emitted in gaseous form or form of fine particulates.
  • Rain ultimately washes the air having metallic pollutants and brings them to the land and to water bodies.
  • Heavy metals cannot be destroyed by biological degradation.
  • The heavy metals often encountered in the environment include lead, mercury, arsenic, chromium. These are known to cause toxic effects in living organisms.


  • Lead enters the atmosphere from automobile exhaust.
  • Tetraethyl lead (TEL) was added to petrol as an anti-knock agent for a smooth running of engines.
  • Lead in petrol is being phased out by the introduction of lead-free petrol.
  • Many industrial processes use lead, and it is often released as a pollutant.
  • Battery scrap also contains lead. It can get mixed up with water and food and create cumulative poisoning.
  • Lead can cause irreversible behavioural disturbances, neurological damage and other developmental problems in young children and babies. It is a carcinogen of the lungs and kidneys.


  • In Japan, mass mercury poisoning (Minamata disease) was observed in the 1960s, caused by eating fish from Minamata Bay which was contaminated with methyl mercury.
  • Mercury kills cells in the body and damages organs and thus impairs their functioning.
  • Inhalation of mercury vapours is more dangerous than its ingestion.
  • Chronic exposure causes lesions in the mouth and skin and neurological problems.
  • Mercury thermometers used earlier are getting replaced by mercury-free thermometer.


  • Arsenic is associated with copper, iron and silver ores.
  • Arsenic is also emitted from fossil fuel burning.
  • Liquid effluents from fertilizer plants also contain arsenic.
  • Groundwater contamination with arsenic is very common in areas where it is present.
  • Chronic arsenic poisoning causes melanosis and keratosis (dark spots on the upper chest, back and arms are known as melanosis. The next stage is keratosis in which palms become hard) and leads to loss of appetite, weight, diarrhoea, gastrointestinal disturbances and skin cancer.
  • Surface waters are generally free from arsenic pollution and should be preferred for drinking and cooking.


  • Mining, especially of zinc and metallurgical operations, electroplating industries, etc., release cadmium in the environment.
  • It may enter the human body by inhalation or from aquatic sources including fish, etc.
  • It may cause hypertension, liver cirrhosis, brittle bones, kidney damage and lung cancer.
  • Itai-itai disease first reported from Japan in 1965 was attributed to cadmium contamination in water and rice caused by the discharge of effluents from a zinc smelter into a river.

Other Heavy Metals

  • Metals such as zinc, chromium, antimony and tin enter food from cheap cooking utensils.
  • Preserved foods stored in tin cans also cause contamination by tin.
  • Zinc is a skin irritant and affects the pulmonary system.
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