These epidemics are quite frequent not only in the developing countries, but also in the developed countries in which sewage treatment processes are widely employed. Sewage is rich in nitrate and phosphate, of which only 50 per cent may be removed after treatment and rest, is released into drainage system which may pollute the water of lakes and ponds.
Sewage can also cause pollution by promoting bacterial growth. This problem has become quite acute in India, Indonesia, Malaysia, Pakistan and Philippines (Hungspreugs, 1988: 178-82). The disposal of domestic rubbish needs landfill sites in the vicinity of urban ecosystems.
The landfills result into obnoxious odours. Such landfills also generate methane and hydrogen sulphide which are injurious to health.
Many a times the landfills become potential dangers and points of health hazards for the neighbouring communities. In the developing countries, the condition is worst as many of the people live on or near the landfills.
The industrial wastes consist of chemicals, detergents, metals and synthetic compounds besides the solid wastes and garbage.
The heavy metal chemical pollutes the water system which may be a threat to aquatic life and human health. It has been reported that mercury poisoning impairs sensory, visual, auditory functions especially in unborn foetuses. There are several examples of methyl mercury poisoning that have proved fatal on a relatively large scale.
The discharge of methyl mercury from a chemical plant near Tokyo between 1953 and 1975 provides one of the best examples of steady water pollution.
The mercury entered marine food chain and mercury rich residues became concentrated in higher trophic levels comprised fish.
These were harvested and consumed by local fishermen, resulting in about hundred deaths and disabled for up to 1,000 people (Hutton, in Hutchinson and Meena, 1987: 53-68). The discharge of heavy metal rich industrial effluent can also create health problems. Moreover, underground water and soils may also be contaminated by heavy metals.
The increased nuclear fuel is becoming as one of the major sources of non-conventional energy. At present, about 4 per cent of the world energy requirements are obtained from nuclear power.
There are many nuclear reactors in operation, especially in the developed countries. Their total number in the world is about 390, out of which 37 and 34 are in Britain and France respectively (Bunyard, in Goldsmith et al., 1988: 33-55).
The nuclear waste contains radio-active isotopes which generate large quantities of heat. These radioactive elements remain active many hundreds of thousands of years. The disposal of nuclear waste is therefore a serious danger to the biosphere.
Moreover, it has been found that nuclear wastes have created ecological problems and it has been reported that incidences of childhood leukaemias occur in population close to nuclear reactor. In October 1993, the Japanese government protested against Russia for its nuclear waste disposal into the Japan Sea in the vicinity of Japan.
The domestic, industrial and nuclear wastes and their disposal are thus serious health hazards which may endanger the biosphere.
In order to control the air, water and soil pollution by the fossil and nuclear fuels and heavy metals containing chemicals released by the industries, it is imperative to adopt drastic measures if the human civilization is to be protected. This necessitates international political cooperation and much forethought for future energy policies.