• 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.


  • Indiscriminate use of fertilizers, pesticides, insecticides and herbicides
  • Dumping of large quantities of solid waste
  • Deforestation and soil erosion.
  • Pollution Due to Urbanization.


  1. Industrial Wastes:
  • Industrial waste includes chemicals such as mercury, lead, copper, zinc, cadmium, cynides, thiocynates, chromates, acids, alkalies, organic substances etc.
  1. Pesticides:
  • Pesticides are chemicals that include insecticides, fungicides, algicides, rodenticides, weedicides sprayed in order to improve productivity of agriculture, forestry and horticulture.
  1. Fertilizers and manures:
  • Chemical fertilizers are added to the soil for increasing crop yield. Excessive use of chemical fertilizers reduces the population of soil borne organism and the crumb structure of the soil, productivity of the soil and increases salt content of the soil.
  1. Discarded materials:
  • It includes concrete, asphalt, rungs, leather, cans, plastics, glass, discarded food, paper and carcasses.
  1. Radioactive wastes:
  • Radioactive elements from mining and nuclear power plants, find their way into water and then into the soil.
  1. 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.


  • 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.
  • Bio magnification.
  • Release of pollutant gases.
  • Reduced vegetation.
  • Ecological imbalance.
  • Clogging of drains.



  • Solid wastes are the discarded (abandoned or considered waste-like) materials.
  • Solid waste means any garbage, refuse, sludge from a wastewater treatment plant, or air pollution control facility and other discarded materials including solid, liquid, semi-solid, or contained gaseous material, resulting from industrial, commercial, mining and agricultural operations, and from community activities.
  •  But it does not include solid or dissolved materials in domestic sewage, or solid or dissolved materials in irrigation return flows or industrial discharges.



A) Types

  • Solid wastes are classified depending on their source:
  • Municipal waste,
  • Hazardous waste and
  • Biomedical waste or hospital waste.
  1. Municipal solid waste
  • Municipal solid waste consists of household waste, construction and demolition debris, sanitation residue, and waste from streets.
  1. Hazardous waste
  • Industrial and hospital waste is considered hazardous as they contain toxic substances. Hazardous wastes could be highly toxic to humans, animals, and plants and are corrosive, highly inflammable, or explosive.
  • Household waste that can be categorized as hazardous waste include old batteries, shoe polish, paint tins, old medicines, and medicine bottles.
  • In the industrial sector, the major generators of hazardous waste are the metal, chemical, paper, pesticide, dye, refining, and rubber goods industries.
  1. Hospital waste
  • Hospital waste is generated during the diagnosis, treatment, or immunization of human beings or animals or in research activities or in the production or testing of biologicals.
  • These chemicals include formaldehyde and phenols, which are used as disinfectants, and mercury, which is used in thermometers or equipment that measure blood pressure.
  • It may include wastes like soiled waste, disposables, anatomical waste, cultures, discarded medicines, chemical wastes, disposable syringes, swabs, bandages, body fluids, human excreta, etc.


  • Stockholm Conventionon 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”.


  • 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 notaddress the movement of radioactive waste.


  • 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.


A) 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.

B) Landfills

  • 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.

C) 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.

D) 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.

E) Pyrolysis

  • 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 andfuel gas.

F) Composting

  • 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.

G) Vermiculture

  • 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.


  • WMC helps Small and Medium Industrial Clusters in waste minimisation in their industrial plants.
  • This is assisted by the World Bankwith 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.


  • 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.

A) Source and health effects



  • 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, Maharashtraranks first followed by Tamil Nadu (2nd), Andhra Pradesh (3rd), Uttar Pradesh (4th), Delhi (5th), Gujarat (6th), Karnataka (7th) and West Bengal (8th).
  • 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.


  • 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.

A) Lead

  • Lead enters the atmosphere from automobile exhaust.
  • Tetraethyl lead (TEL) was added to petrol as an anti-knock agentfor 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.

B) Mercury

  • 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.

C) Arsenic

  • Arsenic is associated with copper, iron and silver ores.
  • Arsenic is also emitted from fossil fuel burning.
  • Liquid effluents from fertilizer plantsalso 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.

D) Cadmium

  • 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 diseasefirst 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.

E) Other Heavy Metals

  • Metals such as zinc, chromium, antimonyand 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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