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Wednesday, February 27, 2008

Treatment Of High Blood Pressure

Hypertension is the most common cardiovascular disease. It has been estimated that after the age of 40,about one third of men and one fifth of women suffer from hypertension. Elevated arterial pressure causes pathological changes in the vasculature and also cause hypertrophy of the left ventricle. As a result hypertension is the principal cause of stroke, coronary artery disease, myocardial infraction and sudden cardiac death. Hypertension is broadly grouped into two categories
1. The essential or primary hypertension, the exact cause of which is not known but there is generally a narrowing of blood vessels.
2. Secondary htpertension due to the involvement of some organs or systems such as kidneys, adrenal glands, disorders like toxaemia of pregnancy.
In seconcary hypertension the cause can be removed and the B.P. is brought back to normal. The diagnosis is based on repeated, reproducible measurements of elevated blood pressure. The sevrity of hypertension is classified based on diastolic pressure. For the purpose of clinical management, essential hypertension is divided into mild(90-104 mm Hg), moderate(105-114 mm Hg) and servre(more than 115 mm Hg) based on diastolic pressure. The aim of drug therapy is to lower the elevated blood pressure to within normal range. The antihypertensive therapy effectively controls the blood pressure, prevents the complications and prolongs the life of the patients.
Some fifty years back we did not have any drug which could lower blood pressure in hypertensive patients. The drugs which are described in this section have all been developed in the last 30 years or so. In the ayurvedic medicine the roots of Rauwolfia gave been used for verious aliments. The alkaloid reserpine separated from these roots was found to have blood pressure lowering properties and has been used in the treatment of hypertension .However with the discovery of a large number of drugs which are safer and have lesser side effects,the use of reserpin has declined. The drugs described here do not eliminate the cause of the hypertensive state but they do allow a person to lead a near normal life and also prevents the worsening of his cardiovascular system.

Different Dosage Forms

A drug may be defined as an agent, intened for use in the diagonosis, mitigation, treatment, cure or prevention of disease in man or in other animals. Drugs are rarely administered in their original pure state. They are administered in different dosage forms after converting them in to a suitable formulation. Every dosage form is a combination of the drug and different kind of non-drug components called “additives”.the additives are used to give a perticular shape to the formulation to increase its stability and also to increase its palatability as well as to give more elegance to the preparation.
Important Dosage Forms
Transformation of drug into different dosage forms is done for the following resons are
1. To protect the drug substance form oxidation, hydrolysis, and reduction.
Example:-coated tablets and sealed ampoules.
2. To protect the drugs form the destructive effect of gastric juice of the stomach after oral administration.
Example:-enteric coated tablets.
3. To provide a safe and convenient delivery of accurate dosage.
4. To conceal the bitter,salty or obnoxious taste or ordur og a drug substance.
Example:-capsule,coated tablets and flavoured syrups etc.
5. To provide for the optimum drug action through inhalation therapy.
Example:-inhalation aerosols and inhalants.
6. To provide for the insertion of the drug in to one of the body cavities.
Example:-rectal or vaginal suppositories
7. To provide form the maximum drug action form topical administration sites .
example:-creams,ointments,ophthalmic preparation and E.N.T. preparation.
8. To provide sustained released action through controlled released mechanism.
Example:-sustained released tablets, capsules and suspensions.
9. To provide liquid dosageform of the drugs soluble in a suitable vehicle.
Example:-solution
10. To provide liquid preparation of the drugs which are insoluble or unstable in different vehicles.
Example:-suspension
11. To provide the drugs within body tissues.
Example:- injection
12. Many dosage forms can be easily identified form their distinct colour,shape or identifying markings.

The dosages are divide in three forms
a. Solid dosage forms
b. Liquid dosage forms
c. Semi-solid dosage forms
Solid Dosage Forms
The solid dosage forms are available mostly in unit dosage forms such as tablets,capsule,pills,cachets or powders.When drugs are to be administered orally in dry state,tablets and capsules are yhe most convenient dosage form.They are effective and patients have no problem in their handling,identification and administration.Some solids are packed and supplied in bulk.The bulk forms meant for internal use are supplied either as garnules or fine powder.the bulk powders meant for external use are dusting powders,insufflations,snuffs and tooth powders.
Dusting Powders
These are meant for external application ti the skin and generally applied in a very fine state of subdivision to avoid local irritation.Hence,dusting powders should be passed through a 80 sieve to enhance their effectiveness.
Insufflations
These are medicated dusting powders meant for introduction into the body cavities such as nose,throat,ears and vagina with the help of an apparatus known as “Insufflator”.It sparys the powder into a stream of finely divided particles all over the site application.
Snuffs
Yhese are finely divided solid dosage forms of medicament are inhaled into nostrils for its antiseptics,bronchiodilator and decongestion action.
Tablets
These are solid dosage forms of medicament or medicaments which are prepared by moulding or by compression.Certain excipients are also added to the medicaments in the formulation of tablets
Capsules
The capsule are solid unit dosage form in which one or more medicaments and inert substances are enclosed within a small shell,generally prepared from a suitable form of gelatin.
Pills
Pills are small, rounded solid dosage forms containing medicament and are intended to be administered orally.The medicameents are mixed with excipients to form a firm plastic mass.the mass is rolled uniforms pill pipe,which is cut into a number of pills.These are rounded to form pills of uniform size and shape.
Liquid Dosage Forms
Liquid stage forms are meant for internal,parenteral or external use.Example,syrups,elixirs,drops.
syrups
simple syrup is a saturated solution of sucrose in purified water.The concentration of suger is 66% w/w.The syrups are sweet viscous preparations.The syrups containing medicinal substances are called “Medicated syrups” and those containing aromatic or flavoured substances are known as “Flavoured syrups”.
Elixirs
Elixirs are sweet aromatic preparation and are usually coloured.The main ingredients of elixirs are ethyl alcohol(4-40%),water,glycerin or propylene glycol,flavouring agent,surup and some suitable preservative.The medicated elixirs usually contain some very potent drug,such as antibiotics,antihistamines or sedatives.The flavouring elixirs are used as flavours vehicles.
Drops
These are liquid preparations meant for oral administrations.The oil soluble vitamins,such as vitamin A and D concentrates in fish-livor oil are presented as drops for administrations. Since these preparations contain potent medicaments,the dose must be measured accurately.
Semi-sold Dosage Forms
Semi-solid dosage forms are mainly meant for exrernal application.Example,Ointments.creams
Ointments
Ointments are semi-solid preparations meant for application to the skin or mucous membrance.They usually contain a medicament or medicaments dissolved,suspended or emulsified in the ointment base.The ointments are mainly used as protective or emollient for the skin.The ointments which are meant for application to the eye are called “Ophtgalmic Ointments”.These ointments are sterile and free from irritation.
Creams
These are viscous semi-solid emulsions which are meant for external use. The creams are of two types,aqueous and oily creams.In case of aqueous creans, the emulsions are in oil-in-water type and in case of oily creams, emulsions are water in oil type.The oil-in-water type cream is relatively non-greasy.In aqueous creams,the emulsifying anionic,cationic and non-ionic waxes,polysorbates and triethanolamine soaps are used as emulsifying agent.The oily creams are generally prepared with emulsifying agent,such as wool fat, wool alcohols, beeswax and calcium soaps.A suitable preservative is generally added in aqueous creams which have the tendency to bacterial and fungal growth.

Monday, February 18, 2008

Chemotherapy Of Sexually Transmitted Diseases(AIDS)

All most any communicable disease can be sexually transmitted during sexual contact.In modern times,the Sexually Transmitted Diseases (STD) have reached epidemic proportions in the Western societies and in india also,though we do not have stastistical data available.STD are on the increase.The devastating disease,Acquired Immune Deficiency Syndrome (AIDS) has drawn international attention.The risk of contacting STD andAIDS depends on the number and nature of sexual partners and the type of sexual contact.Sexually active young and unmarried individuals,homosexuals (gay-man) with multiple partners and those in the lower educational and socio-economic stastus are at high risk in acquring such diseases.
Acquired Immune Deficiency Syndrome(AIDS)
AIDS is a complex viral diseases due to a defect in the immune system.Because of the immune deficiency the patient becomes susceptible to serious infection caused by bacteria,fungi,viruses and other parasites.AIDS is caused by human immunodeficiency retrovirus (HIV) or lymph-adenopathy-associated virus (LAV). The virus can be transmitted both heterosexually or homosexually. Although the virus dose not invariably cause AIDS, in patients who develop the disease,it takes 6 months to 6 years or more for the development of AIDS symptoms.In india the firstHIV seropositive individuals was detected in 1986 and since then the HIV prevalence in our country has increased from 0.2% in 1986 to approximately 0.7% in 1994.It is estimated that about 0.61 million persons are infected in india and by turn of the 20th century nearly 10 million or more people would infected with this virus.
The diseases has attained alarming proportions,mainly because of free sex and increased mobility of the society.The young adults in cities like Mumbai and Delhi are at higher risk of contacting the disease.The disease is commonly seen in homosexually and bisexually actives males,intravenous drug abusers, hetrosexual partners of the above groups, haemophilics and other recipients of blood or blood components and infants of infected mother.The HIV virus is a transmitted during the intimate contact with infected body fluids such as blood,semen,saliva,urine and faeces or by exposure to infected blood as in the use of infected drug injection needles by addicts or by receiving an unscreened blood transfusion.

SYMPTOMS
Most of HIV infected individuals are asymptomatic and are capable of carrying out their usual daily activities.In active disease,there is occurrence of the symptoms such as feeling of fatigue,fever,loss of appetite,weight loss,diarrhoea.night sweets and lymph gland enlargement.About 85% of AIDS patientsdevelop either pneumonia(a parasitic infection of lungs) or a cancer (Kaposi’s sarcoma).The mortality rate in AIDS is very high (33% to 100%) depending up on the infection and length of exposure to the diseases.

TREATMENT
Zidovudine(ATZ,Retrovir) is an inhibitor of the reverse trancriptase enzymes of HIV virus. The recommended oral dose is 200mg every 4hr around the clock. The side effects associated with ATZ treatment are mainly haematologic toxicity including granulocytopenia and severe anaemia requiring blood transfusion.Blood picture should be periodically monitored. Use of other drugs which effects blood picture, nephotoxic and cytotoxic drug along with ATZ may increase the risk of toxicity.The quality as well as survial rate in AIDS patients who are on Zidovudine has increased,it is not a cure for AIDS and AIDS patients continue to be susceptible to infections although it prolongs life and reduced morbidity.Side effects of Zidovudine are headache, agitation, insomnia, diarrhoea, rashes and fevers.Morrow serious side effects are bone marrow depression , server anaemia, granulocytopenia and even thrombocytopenia.Other dtugs used for this disease are didanosine, Zalcitabine and stavudine.
Didanosine has efficacy against zidovudine-resistant strains in vitro.Thus, switching to didanosine after a period of zidovudine threapy has been shown to be beneficial. It is administered in a dose of 125-200 mg twice daily. The adverse effects includes peripherl neuropathy and fatal pancreatities. Zalcitabine is used in combination with zidovudine. The recommened dosage is 0.75 mg zalcitabine with 200 mg zidovudine ecery 8 hours.Zalcitabine causes painful sensory and motor peripheral neuropathy.Patient is advised to seek expert medical care for this before treatment is started.

SAFETY PRECAUTIONS
1. Know the sexual background and habbits of partners, and to stop sexual relationship if the partner is high risk patient.
2. Use of condoms which prevent the entry of the virus into the blood stream and the use of spermicide such as foams, creams or tablets.
3. Avoid sexual practices that may injure bodily tissues,example – anal intercourse.
4. Avoid the use of unprescribed intravenous drugs and do not share needles of syrunges as they are likely sources of infection.

Soil Management

I.INTRODUCTION
Soil Management, the basis of all scientific agriculture, which involves six essential practices: proper tillage; maintenance of a proper supply of organic matter in the soil; maintenance of a proper nutrient supply; control of soil pollution; maintenance of the correct soil acidity; and control of erosion.

II.TILLAGE
The purpose of tillage is to prepare the soil for growing crops. This preparation is traditionally accomplished by using a plough that cuts into the ground and turns over the soil, removing or killing any weeds growing in the area, loosening and breaking up the surface layers of the soil, and providing a bed of soil that holds sufficient moisture to permit the planted seeds to germinate. Traditional tillage may harm the soil if practiced continuously over many years, especially if the fertile topsoil layer is thin. Today, many farmers use a programme of minimum or reduced tillage to conserve the soil. In this form of tillage, any dead plant material that remains on the ground after the crop is harvested is left on or near the surface of the soil, rather than being ploughed deeply into the ground as in traditional tillage; this helps to keep moisture within the ground, and protects the soil from erosion.
Ploughs, which are the chief mechanical implements used for tillage in all parts of the world, may be designed for a number of purposes ranging from the simple cutting of a furrow through the ground to the complete reversal, or turning over, of soil, usually to a depth of 15 to 20 cm (6 to 8 in). In certain areas and for certain purposes the plough is replaced as a primary tillage instrument by various types of harrows, tools that scrape or scarify the surface of the ground without digging deeply into it. In most areas, such implements are employed merely to break up and pulverize the soil after ploughing. Harrows or tools of the same general design are almost universally used for the cultivation of the ground between rows of growing crops.
Deep ploughing and subsequent harrowing are necessary in areas where the soil is compact and impermeable to water and plant roots. Excessive tillage may, however, result in the deterioration of soil structure, particularly if performed in wet soil. This problem is more acute in finely textured soils than in sand and loam, which normally require less tillage. Climate also plays its part in determining not only the amount but also the time of tillage. In areas, with high humidity, tillage should be limited to times when no great amount of rainfall is expected, for newly-tilled fields are susceptible to water erosion. On the contrary, in arid or sub humid areas, land should be tilled before periods of anticipated rainfall so that the ground can absorb the maximum amount of water.
Among the secondary but important benefits of tillage is the aeration, exposure to the air, resulting from pulverization. This aeration not only provides a freer circulation of oxygen and water but also results in increased biological activity in the soil, including that of organisms that fix atmospheric nitrogen. Tillage contributes to the health of plants by inhibiting plant diseases and by discouraging the development of various types of insects that harm plants.
The type of tillage affects the loss of soil through erosion by wind and water. When furrows are ploughed in an uphill-and-downhill direction, water tends to flow down the furrows, carrying away small particles of the top layers of soil as it flows. By ploughing across the slope instead, the water stays in the furrows and sinks into the soil rather than running off. Tillage of this type is commonly known as contour ploughing because the furrows follow the natural contours of the land.
The kind and amount of cultivation between the rows of growing crops is essentially determined by the character of the soil. Heavy, waterlogged soil benefits by the stirring up and aeration that cultivation provides, while hard, caked soils may also require cultivation to permit them to absorb the moisture that the crops need. For soils that are in good physical condition, however, the primary purpose of cultivation of row crops is to permit weed control.

III.MAINTENANCE OF ORGANIC MATTER
Organic matter is an important element in maintaining good physical conditions in the soil; it contains the entire soil reserve of nitrogen and significant amounts of other nutrients, such as phosphorus and sulphur. Soil productivity is thus markedly affected by the organic-matter balance maintained in the soil. Because most cultivated vegetation is harvested instead of being left to decay, organic materials that would ordinarily enter the soil upon plant decomposition are lost. To compensate for this loss, various standardized methods are employed. The two most important of these methods are crop rotation and artificial fertilization.
Crop rotation consists of growing different crops in succession on the same land, rather than utilizing a one-crop system or a haphazard change of crops. In the rotation system, crops are alternated on the basis of the amounts and types of organic matter that each returns to the soil. Because frequent tillage hastens the oxidative loss of organic matter, rotations usually include one or more sod crops (crops that grow on the surface of the ground) that require little or no tillage. Deep-root penetration on the part of certain leguminous crops, such as alfalfa, provides better drainage as a result of the channels left after the roots decay (see Legume).
The rotation system employs special types of crops such as cover crops and green-manure crops. Cover crops are those crops planted to protect the soil during winter and, if a leguminous crop is used, to promote nitrogen fixation. Green-manure crops are grown solely to be ploughed into the ground and serve to increase the organic-matter content of the soil. Although no yield is expected of a green-manure crop, it should increase the yield of subsequent crops planted in the same fields.
The older method of increasing the organic content of the soil is the use of such fertilizers as manure and compost. The manuring of soil with animal waste has been practiced for many thousands of years and serves as a source of various complex organic compounds that are important in the growth of plants. Compost, which usually consists of a mixture of dead vegetable and animal matter, has a purpose similar to that of manure and is often treated with chemical fertilizers to increase its effectiveness.

IV.NUTRIENT SUPPLY
Among soil deficiencies that affect productivity, deficiency of nutrients is especially problematic. The nutrients most necessary for proper plant growth are nitrogen, potassium, phosphorus, iron, calcium, sulphur, and magnesium, all of which usually exist in most soils in varying quantities. In addition, most plants require minute amounts of substances known as trace elements, which are present in the soil in very small quantities and include manganese, zinc, copper, and boron. Nutrients often occur in the soil in compounds that cannot be readily utilized by plants. For example, phosphorus combined with calcium or magnesium can be used by plants, but phosphorus combined with iron or aluminum usually cannot. Enrichment with artificial fertilizers and by treatments hastening the breakdown of complex compounds often increases the supply of usable minerals in soil. The supply of available phosphorus, for example, is often increased by the addition of super phosphate fertilizers. Adding calcium to soils also decreases soil acidity and makes phosphorus more readily available to vegetation. The existence of phosphorus in several unavailable forms is sometimes advantageous, however, as it helps to conserve the phosphorus supply in the soil and makes the effects of super phosphate applications last for several years. Copper and sulphur are often added to the soil through the use of spray solutions. Other elements are added by direct application or by the use of specific artificial fertilizers.

V.SOIL POLLUTION
Soil pollution is defined as the build-up in soils of persistent toxic compounds, chemicals, salts, radioactive materials, or disease-causing agents, which have adverse effects on plant growth and animal health. The increasing amounts of fertilizers and other agricultural chemicals that were applied to soils following the end of World War II, plus industrial and domestic waste-disposal practices, led to increasing concern over soil pollution by the mid-1960s. Although the application of fertilizers containing the primary nutrients—nitrogen, phosphorus, and potassium—has not led to soil pollution, the application of trace elements has. The irrigation of arid lands often leads to pollution with salts. Sulphur from industrial waste has polluted soils in the past, as has the accumulation of arsenic compounds in soils following years of spraying crops with lead arsenate. The application of pesticides has also led to short-term soil pollution. See Environment.

VI.PESTICIDE RESIDUES
The effectiveness of a pesticide as well as the hazards of harmful residues depends largely on how long the pesticide remains in the soil. For example, DDT, a chlorinated hydrocarbon, has a half-life of three years in cultivated soils, while organ phosphorus insecticides persist for only days or months. Chlorinated hydrocarbons persist longer in soils that have a large amount of organic matter, although more of the chemical must be applied to such soils to kill pests. Insecticides persist longer if worked into the soil than if left on the surface. Herbicides applied to soils may not persist at all or may persist up to two years or longer, depending on the compound. Simiazine is one of the most persistent herbicides, although all pesticides disappear eventually because of evaporation and vaporization, leaching, plant uptake, chemical and microbial decomposition, and photodecomposition.

VII.SOIL ACIDITY ADJUSTMENT
Maintenance of specific soil acidities is important in soil management in order to control the adaptation of various crops and native vegetation to different soils. For example, cranberries can be successfully grown only in moderately to strongly acid soils, whereas alfalfa and other legumes are successful only in weakly acid or slightly alkaline soils. The ordinary procedure for correcting excess soil acidity is the application of lime in the form of limestone, dolomitic limestone, or burnt lime. When lime is added, the hydrogen of the complex soil colloid is exchanged for the calcium of lime. Acid soils are found predominantly in regions of high rainfall; in arid regions, the soil is usually alkaline.

VIII.MECHANICAL CONTROL OF EROSION
The mechanical loss of fertile topsoil is one of the gravest problems of agriculture. Such loss is almost always caused by erosion resulting from the action of water or wind. For a discussion of the problem and the various methods for combating erosion.

Air Pollution

I.INTRODUCTION
Air Pollution, contamination of the atmosphere by gaseous, liquid, or solid wastes or by-products that can endanger human health and the health and welfare of plants and animals, or can attack materials, reduce visibility, or produce undesirable odours. Among air pollutants emitted by natural sources, only the radioactive gas radon is recognized as a widespread major health threat, although gases and particles from volcanic eruptions can cause serious more localized problems. A by-product of the radioactive decay of uranium minerals in certain kinds of rock, radon seeps into the basements of homes built on these rocks, posing a risk of lung cancer to residents.
Each year industrially developed countries generate billions of tons of pollutants. The most prevalent and widely dispersed air pollutants are described in the accompanying table. The level is usually given in terms of atmospheric concentrations (micrograms of pollutants per cubic metre of air) or, for gases, in terms of parts per million, that is, millilitres of gas per thousand litres of air. Many come from directly identifiable sources; sulphur dioxide, for example, comes from electric power plants burning coal or oil. Others are formed through the action of sunlight on previously emitted reactive materials (called precursors). For example, ozone, a dangerous pollutant in smog, is produced by the interaction of hydrocarbons and nitrogen oxides under the influence of sunlight. Ozone also causes serious crop damage. On the other hand, the discovery in the 1980s that air pollutants such as fluorocarbons are causing a loss of ozone from the Earth's protective ozone layer has caused the phasing out of these materials. A further category of air pollution is heavy metals, present as particulates and arising from many industrial processes.

II.METEOROLOGY AND HEALTH EFFECTS
Pollutant concentration is reduced by atmospheric mixing, which depends on such weather conditions as temperature, wind speed, and the movement of high and low pressure systems and their interaction with the local topography, for example, mountains and valleys. Normally, temperature decreases with altitude. But when a colder layer of air settles under a warm layer, producing a temperature or thermal inversion, atmospheric mixing is retarded and pollutants may accumulate near the ground. Inversions can become sustained under a stationary high-pressure system coupled with low wind speeds.
Periods of only three days of poor atmospheric mixing can lead to high concentrations of hazardous materials in high-pollution areas and, under severe conditions, can result in injury and even death. An inversion over Donora, Pennsylvania, in 1948 caused respiratory illness in over 6,000 people and led to the deaths of 20. Severe pollution in London took 3,500 to 4,000 lives in 1952 and another 700 in 1962. Release of methyl isocyanate into the air during a temperature inversion caused the disaster at Bhopal, India, in December 1984, with at least 3,300 deaths and more than 20,000 illnesses. The effects of long-term exposure to low concentrations are not well defined; however, those most at risk are the very young, the elderly, smokers, workers whose jobs expose them to toxic materials, and people with heart or lung disease. Other adverse effects of air pollution are injury to livestock and crops.
Often, the first noticeable effects of pollution are aesthetic and may not necessarily be dangerous. These include visibility reduction due to tiny particles suspended in air, or bad odours, such as the rotten egg smell produced by hydrogen sulphide emanating from pulp and paper mills.

III.SOURCES AND CONTROL
The combustion of coal, oil, and petrol accounts for much of the airborne pollutants. About 60 per cent of the sulphur dioxide and 20 per cent of the nitrogen oxides emitted into the atmosphere in the United Kingdom are produced by fossil-fuel-fired electric power plants. About 70 per cent of the carbon monoxide and 50 per cent of the nitrogen oxides come from burning petrol and diesel in cars and lorries. Other major pollution sources include iron and steel mills; smelters; municipal incinerators; oil refineries; cement plants; and nitric and sulphuric acid plants.
Potential pollutants may exist in the materials entering a chemical or combustion process (such as sulphur in coal), or they may be produced as a result of the process itself. Carbon monoxide, for example, is a typical product of internal-combustion engines. Methods for controlling air pollution include removing the hazardous material before it is used, removing the pollutant after it is formed, or altering the process so that the pollutant is not formed or occurs only at very low levels. Car exhaust pollutants can be controlled by burning the fuel as completely as possible, by recirculating fumes from fuel tank, carburettor, and crankcase, and by changing the engine exhaust to harmless substances in catalytic converters. Industrially emitted particulates may be trapped in cyclones, electrostatic precipitators, and filters. Pollutant gases can be collected in liquids or on solids, or incinerated into harmless substances.


IV.LARGE-SCALE EFFECTS
The tall smokestacks used by industries and utilities do not remove pollutants but simply boost them higher into the atmosphere, thereby reducing their concentration at the site. These pollutants may then be transported over large distances and produce adverse effects in areas far from the site of the original emission. Sulphur dioxide and nitrogen oxide emissions from Britain and other industrialized countries of Western and Central Europe are causing acid rain in Norway and Sweden. The pH level, or relative acidity, of many freshwater lakes has been altered so dramatically by acid rain that entire fish populations have been destroyed. Sulphur dioxide emissions and the subsequent formation of sulphuric acid can also be responsible for the attack on limestone and marble at large distances from the source. There are also claims that acid rain is causing widespread damage to forests in Europe, but the precise role is unclear and earlier predictions of large-scale forest death are unfounded.
The worldwide increase in the burning of coal and oil since the late 1940s has led to ever-increasing concentrations of carbon dioxide. The resulting “greenhouse effect”, which allows solar energy to enter the atmosphere but reduces the reemission of infrared radiation from the Earth, may well lead to a warming trend that might affect the global climate and lead to a partial melting of the polar ice-caps. Possibly an increase in cloud cover or absorption of excess carbon dioxide by the oceans (in the so-called carbon cycle) would check the greenhouse effect before it reached the stage of polar melting. Nevertheless, many research reports released during the 1990s have indicated that the greenhouse effect is definitely under way and that the nations of the world should be taking immediate steps to deal with it. In June 1999 a massive cloud of air pollution, roughly the size of the United States, was discovered 1 km to 3 km (’ mi to 2 mi) above the Indian Ocean. The thick brown haze included soot, sulphates, nitrates, mineral dust, and significant amounts of gases such as carbon monoxide and sulphur dioxide. Scientists believe it was created by human activities, especially the burning of fossil fuels, and could have a significant impact on the regional and global climate, as well as plant and animal life.

V.ACTION BY GOVERNMENTS
Various countries have set standards in legislation in the form of concentration levels that are believed to be low enough to protect public health. Source emission standards are also specified to limit the discharge of pollutants into the air so that air-quality standards will be achieved. However, the nature of the problem requires the implementation of international environmental treaties, and to this end 49 countries agreed in March 1985 on a United Nations convention to protect the ozone layer. This “Montreal Protocol”, which was renegotiated in 1990 and 1992, called for the phaseout of certain chlorocarbons and fluorocarbons by the end of the century and provides aid to developing countries in making this transition. In addition, several international protocols have been aimed specifically at reducing the incidence of acid rain. In December 1999 the Montreal Protocol announced that almost all production and consumption of virgin ozone depleting substances had been phased out in the developed world. Similar control measures were introduced for developing countries in July 1999, and it was anticipated that all developing countries would be able to meet their freeze targets and subsequent obligations under the protocol.
Concern over trans-boundary air pollution, including acid rain, in Europe has led to the United Nations Economic Commission for Europe (UNECE) developing air quality guidelines, called Critical Loads and Levels, which represent thresholds below which it is believed that damage will not occur to different ecological systems. Critical Loads are based on the amount of acidity that an ecosystem can tolerate being deposited indefinitely. Critical Levels are concentrations of ozone, sulphur dioxide, and nitrogen oxides over different averaging times and applicable to different categories of vegetation. Massive cuts are being made in emissions in Europe in order to move towards these thresholds. In contrast, in many developing countries, pollutant concentrations are rising very rapidly due to increased industrialization and motor traffic; concern in such places is primarily with impacts on human health in cities. The World Health Organization has published air quality guidelines designed to protect health.

Water Pollution

I.INTRODUCTION
Water Pollution, contamination of water by foreign matter such as micro-organisms, chemicals, and industrial or other wastes, or sewage. Such matter deteriorates the quality of the water and renders it unfit for its intended uses.

II.MAJOR POLLUTANTS
The major pollutants of water are the following: Sewage and other oxygen-demanding wastes (largely carbonaceous organic material, the decomposition of which leads to oxygen depletion). Infectious agents. Plant nutrients that can stimulate the growth of aquatic plants, which then interfere with water uses and, when decaying, deplete the dissolved oxygen and produce disagreeable odours. Exotic organic chemicals, including pesticides, various industrial products, surface-active substances in detergents, and the decomposition products of other organic compounds. Petroleum, especially from oil spills. Inorganic minerals and chemical compounds. Sediments consisting of soil and mineral particles washed by storms and floodwater from croplands, unprotected soils, mine workings, roads, and bulldozed urban areas. Radioactive substances from the wastes of uranium and thorium mining and refining, from nuclear power plants, and from the industrial, medical, and scientific use of radioactive materials.
Heat may also be considered a pollutant when increased temperatures in bodies of water result from the discharge of cooling water by factories and power plants.

III.EFFECTS OF WATER POLLUTION
Notable effects of water pollution include those involved in human health. Nitrates (the salts of nitric acid) in drinking water can cause a disease in infants that sometimes results in death. Cadmium in sludge-derived fertilizer can be absorbed by crops; if ingested in sufficient amounts, the metal can cause an acute diarrhoeal disorder and liver and kidney damage. The hazardous nature of inorganic substances such as mercury, arsenic, and lead has long been known or strongly suspected.
Lakes are especially vulnerable to pollution. One problem, eutrophication, occurs when lake water becomes artificially enriched with nutrients, causing abnormal plant growth. Run-off of chemical fertilizer from cultivated fields may trigger this. The process of eutrophication can produce aesthetic problems such as bad tastes and odours and unsightly green scums of algae, as well as dense growth of rooted plants, oxygen depletion in the deeper waters and bottom sediments of lakes, and other chemical changes such as precipitation of calcium carbonate in hard waters. Another problem, of growing concern in recent years, is acid rain, which has left many lakes in northern and eastern Europe and north-eastern North America totally devoid of life.

IV.SOURCES AND CONTROL
The major sources of water pollution can be classified as municipal, industrial, and agricultural.
Municipal water pollution consists of wastewater from homes and commercial establishments. For many years, the main goal of municipal sewage disposal was simply to reduce its content of suspended solids, oxygen-demanding materials, dissolved inorganic compounds (particularly compounds of phosphorus and nitrogen), and harmful bacteria. In recent years, however, more stress has been placed on improving the means of disposal of the solid residues from municipal treatment processes. The basic methods of treating municipal wastewater fall into three stages: primary treatment, including grit removal, screening, grinding, flocculation (aggregation of the solids), and sedimentation; secondary treatment, which entails oxidation of dissolved organic matter by means of biologically active sludge, which is then filtered off; and tertiary treatment, in which advanced biological methods of nitrogen removal and chemical and physical methods such as granular filtration and activated carbon adsorption are employed. The handling and disposal of solid residues can account for 25 to 50 per cent of the capital and operational costs of a treatment plant.
The characteristics of industrial wastewaters can differ markedly both within and among industries. The impact of industrial discharges depends not only on their collective characteristics, such as biochemical oxygen demand and the amount of suspended solids, but also on their content of specific inorganic and organic substances. Three options (which are not mutually exclusive) are available in controlling industrial wastewater. Control can take place at the point of generation within the plant; wastewater can be pretreated for discharge to municipal treatment systems; or wastewater can be treated completely at the plant and either reused or discharged directly into receiving waters.
Agriculture, including commercial livestock and poultry farming, is the source of many organic and inorganic pollutants in surface waters and groundwater. These contaminants include both sediment from the erosion of cropland and compounds of phosphorus and nitrogen that partly originate in animal wastes and commercial fertilizers. Animal wastes are high in oxygen-demanding material, nitrogen, and phosphorus, and they often harbour pathogenic organisms. Wastes from commercial feeders are contained and disposed of on land; their main threat to natural waters, therefore, is via run-off and leaching. Control may involve settling basins for liquids, limited biological treatment in aerobic or anaerobic lagoons, and a variety of other methods.

V.MARINE POLLUTION
Wastes that are discharged directly into United States marine waters are estimated conservatively to exceed 45 million tonnes per year. About 80 per cent of this amount is waste produced by dredging, 10 per cent is industrial waste, and 9 per cent is sewage sludge. The presence of toxic substances, the rapid uptake of contaminants by marine organisms, heavy deposits of materials on the bottom environment near the shore, and excessive growth of undesirable organisms—the combination of all these aspects has very serious consequences. In the United Kingdom, dumping of industrial waste in coastal waters finished at the end of 1992. Of the remaining types of waste dumped at sea, the average annual amount in the period 1981 to 1994 was estimated at 39,676,000 tonnes. Of this, sewage sludge represented 22 per cent, and dredging (mainly from ports and estuaries) 78 per cent (gravel and mud comprising 14 per cent, and sand and silt 64 per cent). The dumping of sewage sludge by the United Kingdom is scheduled to finish at the end of 1998.

VI.OIL SPILLS
Large-scale accidental discharges of liquid petroleum products are an important cause of pollution along shorelines. The most spectacular cases of oil pollution involve the supertankers used for its transport, but many other ships also spill oil, and offshore drilling operations contribute a large share of the pollution. One estimate is that of every million tonnes of oil shipped, one tonne is spilled. Some of the largest spills thus far recorded involve the tanker Amoco Cadiz off the French coast in 1978 (1.6 million barrels of crude oil) and the Ixtoc I oil well in the Gulf of Mexico in 1979 (3.3 million barrels). The spill of 240,000 barrels by the tanker Exxon Valdez in Prince William Sound, Gulf of Alaska, in March 1989, caused within a week a 6,700-sq-km (2,600-sq-mi) slick that endangered wildlife and fisheries in the entire gulf area. On the other hand, the spill of 680,000 barrels from the Braer on the coast of the Shetland Islands in January 1993 was broken up by the wave action of exceptionally severe storms and had mostly dispersed within a few days.
The oil spills in the Persian Gulf in 1983, during the Iran-Iraq conflict, and in 1991, during the Gulf War, when up to 8 million barrels were released, resulted in enormous damage to the entire area, especially to the marine life.

Thursday, February 14, 2008

what is toxicology ?

TOXICOLOGY
Toxicology is a science that deals with the study of the adverse effects of chemical on living organisms.The word is derived from two words , Toxicon meaning poison and logos meaning discourse.Therefore , Toxicology involves the study of poisons.That is their biological activity and effects,procedures for detecting their presence and the treatment of the poisoned patient.Poison are substances(chemical/drugs)that cause harmful,dangerous of fatal symptoms in animals and human beings.The word poison is mostly used for legal purposes.Many drugs in large doses act as poisons.For example barbiturates can cause toxic effects in large doses.Other common agents having toxic or fatal effects include insecticides and pesticides heavy metals , industrial products(acids and alkalies)or Environmental pollutants present in air , water or food.
DEVLOPMENT OF TOXICOLOGY
The awareness of toxic effects of drugs and their legal aspects is recent , the knowledge of toxic effects of animal venoms and poisonous arrow for hunting and warfare has been reported even in prehistoric times.Hindu mythology and vedic literature give the description of use of metals, opium preparation and other toxic substances.
Paracelsus(16th century)the greek physician made the first scientific observation that “All substance are poisons, there is none that is not a poison.The rifht dose differentiatesa poison and a remedy”.This classic observation holds good even today and perhaps forms the basic of modern toxicology.Claude Bernard (1813 - 1878) who studied the physiology of arrow poison(Tubocurarine)gave the impetus to the devlopment of toxicology in Europe during 19th century.
Devlopment of antidotes for arsenic war gas (BAL,British anti Lewisite) used in the second world war,discovery of presticides,insecticides(DDT,Dichloro-Diphenyl-Trichloroethane),other organophosphorous compounds and more particularly,the thalidomid tragedy have changed the face of toxicology in the last 50years.
SCOPE OF TOXICOLOGY
It is a brsnch of pharmacology,toxicology has devloped in to full discipline in itself.The following scopes are
TOXICOLOGIST:- A specialist who is a trained pharmacologist involved in the study of poisons,adverse or toxic effects of drugs.
DESCRIPYIVE TOXICOLOGIST:- Investigates or evaluates risks of chemical exposure to man and environment.
REGULATORY TOXICOLOGIST:- Determines or sets regulatory control for drugs and chemical for their toxic doses or levls. He works under the regulatory control of the druf regulatory aythorities.
FORENSIC TOXICOLOGIST:- It is concerned with the medicolegal aspects of the use of chemical and drugs that are harmful to man and animals.His functions combine both analytical chemistry and fundamental toxicology.He assists in postmortem, investigations,helps in establishing the cause of death.He gives medicolegal opinion in the case of death due to poison of toxicity.
CLINICAL TOXICOLOGIST:- Focuses on dieases that are caused by or uniquely associated with toxic substances.A clinical toxicologist is a well trained physician who differentiates,diagonoses and treat patients who are poisoned by drugs and other toxic chemical or substances.
The following is the sequences of toxicology, and a toxicologist encompases all these aspects.
Therapeutic dose à Side effects à Adverse effects
Toxic dose à Toxic effects.