Pollutants

Introduction

Any change in physical, chemical and biological characteristics of the environment which harm human life is called pollution.  Pollutant is any substance or chemicals responsible for the pollution.  

On the basis of form of their occurrence, pollutants are divided into two categories-

    Primary pollutants: These are present in the same form in which they are produced. E.g. carbon monoxide, DDT.

Secondary pollutants: these are formed by reaction between the primary pollutants in the presence of sunlight, e.g., PAN, Ozone, HNO3, H2SO4 etc. Nitrogen oxides and hydrocarbons react photochemically to produce peroxyacetyl nitrates (PAN) and ozone.

Example of Pollutants

Carbon monoxide (CO):  It is the main air pollutant (or most poisonous gas) released from automobile smoke. Carbon monoxide is a highly toxic gas, it combines with haemoglobin of the blood and blocks the transportation of oxygen.

Nitrogen oxide (NO, NO2): Burning (combustion) of fossil fuel in automobiles. It forms about 10% pollutants. These nitrogen oxide form photochemical smog in the atmosphere and release ozone. Nitrogen oxide is also responsible for acid rain. Entry of these nitrogen oxide and ozone in humans causes respiratory trouble such as emphysema, bronchitis, swelling of lungs and lung cancer etc.

Sulphur oxide (SO2, SO3): These are the most harmful gaseous pollutants, main source of sulphur oxides are coal burning, smelters, oil refineries. It forms about 18% of total air pollutants. Lichen and mosses do not grow in SO2 polluted areas. Lichen and moss are indicators of SO2 pollution. Oxides of sulphur produce acid rain and smog in the atmosphere.

Smoke: SO2, SO3, NO2, NO, CO and CO2.

Mercury (Hg)

                              Mercury is highly persistent. In water it gets changed into water soluble dimethyl form [(CH3)2Hg] and enters the food chain.

                                 It kills fish and poisons the remaining fauna. Human beings feeding on such poisoned animals develop a crippling deformity called minamata disease which is characterised by impairment of various senses, diarrhoea, haemolysis, meningitis and death.

Minimata disease was first detected in Japan.The non biodegradable pollutant like Al, Hg, Fe, D.D.T., phenolic compound ABS (Alkyl benzene sulphonate) are not decomposed by microorganisms.They get accumulated in tissue in increasing concentration along the food chain is called biological magnification. The highest concentration occurs in the top consumer

Lead

Lead is a persistent pollutant and may show biological amplification or biomagnifican.  It is mutagenic and causes anaemia, headache, vomiting, colic, loss of muscle power, bluish lines around the gums, loss of appetite and damage to liver, kidney and brain.

Cadmium (Cd)

It causes itai-itai disease (a painful disease of joints), hypertension, anaemia, diarrhoea and damages – liver and kidneys.

Oil- Oil spreading on the surface of water prevents its oxygenation and inhibits photosynthetic activity of aquatic plants. Animal life is destroyed due to reduced availability of oxygen, food and toxic effects of oil.

Chlorofluorocarbons (CFC)

It is important to note that humans are not the only species affected by pollutants. For example, in the case of chlorofluorocarbons, the gases affect the protective ozone layer. Typically, aerosols are examples of chlorofluorocarbons.

Suppose the chlorine gets in contact with the earth’s protective ozone layer. In that case, it causes irreparable damage which leads to the entry of cosmic rays that are carcinogenic to human beings and causes the deterioration of marine and terrestrial plant growth.

It comes from vehicles. AC etc.

Pesticides

 Pesticides include insecticides (kill insects), fungicides (kill fungi), algicides (kill algal blooms), weedicides or herbicides (kill weeds), rodenticides (kill rodents).

  DDT (dichloro diphenyl trichloroethane). BHC (benzene hexachloride or gammexane),     aldrin, dieldrin, endrin, heptachlor etc. are chlorinated hydrocarbons used as pesticides.

    DDT and other chlorinated hydrocarbons affect CNS, cause softening of brain, cirrhosis of liver (liver cancer), cerebral haemorrhage, cancer, hypertension, thinning of egg shells in birds, malformation of sex hormones, failure of gonad development.

 Fertilisers

   Fertilisers added to soil enter the crop plants. Nitrogen fertilisers produce toxic concentrations of nitrate in the leaves and fruits. When these leaves and fruits are eaten, nitrates change into nitrites by the activity of bacteria in the alimentary canal. The nitrites enter the blood and combine with haemoglobin to form methaemoglobin. As a result oxygen transport is reduced. It gives rise to a disease known as methemoglobinemia. In infants it produces cyanosis (blue baby syndrome).

Plastic

When it concerns plastic, everyone will agree that people dispose of plastics anyhow, and it causes environmental pollution. It is why many people preach the essence of recycling. But, unfortunately, it is one of the most common environmental pollutants.

Plastic is used almost everywhere; to hold and package things such as foods, drinks, chemicals and is also used as a raw material for making various products. More than 60% of all products are made using plastic.

Yet, plastics are some of the top pollutants globally. If plastics can be effectively managed, they can be used to produce amazing items. Recycling is a method that can curb environmental pollution when it concerns plastic.

Conclusion

  Any change in physical, chemical and biological characteristics of the environment which harm human life is called pollution.  Pollutant is any substance or chemicals responsible for the pollution  Primary pollutants: These are present in the same form in which they are produced. E.g. carbon monoxide, DDT.Secondary pollutants: these are formed by reaction between the primary pollutants in the presence of sunlight, e.g., PAN, Ozone, HNO3, H2SO4 etc. Nitrogen oxides and hydrocarbons react photochemically to produce peroxyacetyl nitrates (PAN) and ozone.