Effect on human health
The World Health Organization (WHO) estimates that anout 5 millions people suffer and die from illness related to contaminated water annually. Contaminated water has been linked to health problems such as diarrhoea, cholera and bilharzia (a disease caused by parasite worms in human bodies).
The poisons in pesticides and chemicals are passed on to people when they consumefish caught in polluted water. One of the world's worst water pollution disaters took place in Minamata Bay, japan, in the world 1950s when mercury waste was dumped by a chemical factory. People who ate the poisoned fish caught in the Bay suffered brain damage and paralysis. The Minamata Bay was only given the 'all clear' in 1997 when mercury levels in the surrounding seas where witin safe limits.
Endangering of marine life
Certain chemicals such as nitrates and phosphoruus are nutrients for plants. Nitrates are contained in fertilisers and hosphorus in detergents. When they enter the water, these chemicals speed up the growth of algae and floating plants such as water hyacinth. This process is known as eutrophication. these plants form a cover over the waste surface, preventing sunlight from reaching other plants in the water. They also deprive the plants and other marine life of oxygen.
A lack of oxygen also occurs when there is an oil leak. A thin layer of oil floating on the surface pf the water, called an oil slick, forms during an oil leak. This blocks sunlight and oxygen from reaching plankton (minute plants and animals which are the food of fish) and other marine organisms and they eventually die from oxygen deprivation. As plankton and small fish form the base of the food chain, their scarcity may cause a chain reaction affecting other animals.
Poisoning of Seabirds and Other Animals
Seabirds and other animals that are caught in an oil spill have a very slim chance of survival. Oil is sticky and holds feathers or fur together so that they can no longer insulate the animals. The animals may freeze to death as a result. The oil also prevents the aniamals from flying or swimming so they swallow the oil while trying to clean themselves.
High Economic Costs
Water pollution affects the fishing and tourism industries. Fewer fish are caught in pollutes waters. If the water is polluted by oil, fishing will not be possible for serval months even after the oil has been removed. It will take considerable time for the aquatic animals to multiply and gor their habitats to be rebuilt.
Most oil spills take place cose to the shore and around ports. When water near the beaches is polluted, tourists will stay away. This affects the tourism industry, especially in countries with beautiful beaches.
