Environment affects human health in two ways. The first way is concerned with direct effect of pollutants discharged by industries into air and water as well as by the emission of gases by automobiles. In urban population the occurrence of diseases are closely linked to the deterioration of air and water quality.
The second way is concerned with the quality of environment at the place of work. Over the years it has been recognized that workers in certain occupations, such as textile mills or stone crushers suffer from occupational diseases. The deterioration of environment such as stagnant pools in villages and cities provides fertile ground for breeding of vectors.
Many such diseases carrying vectors have developed immunity to pesticides, overcrowding and unhygienic living condition in cities especially in slums have also contributed to spread of other communicable diseases.
One-fifth of vehicular population in India is concentrated in the major metropolitan cities. Nearly 70 per cent of vehicles are two and three wheelers which are mostly two stroke engine driven. Petrol driven four stroke engines constitutes only 14 per cent and diesel driven 8 per cent of total.
Two-wheeler vehicle has been growing at rate of 20 per cent per year which will increase to 36 million in 2000 against 7 million in 1987. The consumption of gasoline and diesel by automobiles has increased from 1.5 and 7.2 million tonnes in 1980-81 to 3.5 and 14.8 million tonnes (per cent of world fuel consumption).
The principal pollutants emitted by vehicles are carbon monoxide, hydrocarbons, Nitrogen oxide and particulate matter. Vehicle using petro-cum-based fuels also emit polynuclear hydrocarbons and traces of aldehydes. In addition, a varying amount of Sulphur dioxide is also emitted depending upon the sulphur content in the fuel.
India is predominantly an agricultural country. In India almost 50% of the potential of food grains production is lost annually due to insect/ pests, pathogen etc. Pesticide plays an important role for control of pests in agriculture and public health programmers. India at present is the largest manufacturer as well as consumer of pesticide chemical in Southern Asia.
Pesticide possesses potential health hazard not only to livestock and human beings but also to aquatic flora and fauna. The biomagnifications and bioaccumulation of the pesticide in food chain of fishes of serious concern.
The pesticides are most widely used to protect the standing crops from pest and to increase the yields of crops. However, they cause major harm to aquatic fauna via agricultural run-off and this has resulted in major ecological problems.
The use of pesticides was new era in the application of manmade chemicals in control of pest in which increased the production of food and helped in the eradication of diseases, but this great achievement has resulted in injury and death of variety of forms of life.
Used in insect control these pesticides have contaminated the ecosystem and entered food chain causing damaging effects on the ecosystem and non-target species. The potential toxic compounds get distributed by variety of means and build up concentration in the soil and water and finally reach man. In this pathway they leave degrees of injuries to the life process.
The aquatic organisms like fish are able to accumulate several fold higher concentration than the surrounding water with the contaminated pesticides residues. Fish can store up such pesticides in their visceral fat and edible muscle. Although the quantities of pesticides may be relatively small but the concentrations are still sufficient to have a deleterious impact on the fresh water ecosystems.
A multiple of environmental problem has been associated with modern methods of agriculture. Most of these stem from abuse of pesticides and the use of persistent plant protection chemicals which have been banned in developed nations. Uses of synthetic fertilizers have led to nitrate pollution of water resources. The release of methane from paddy fields is another form of agricultural pollution, and even the pesticides residues in food chain (vegetables, eggs, fish, meat, milk products, edible oil and breast milk) have been detected.