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Sewage pollution and its effects

Sewage pollution of the sea is, of course, as old as civilization. It provides nutrients which, in moderation, can benefit sea life. The problem arises when there is too much of it in too small an area. Even in ancient times some stretches of sea, such as the Bosporus, became badly polluted. Now with the rapid growth of the world's population (doubling since the 1960s), and its increasing concentration around the coasts – especially in developing countries – many inshore waters have become overwhelmed.

This is more than just an aesthetic nuisance. Sewage pollution ruins large areas for fisheries, recreation and tourism, causing major economic loss. Eutrophication and blooms of algae, stimulated by too much nutrition from sewage and agricultural chemicals and wastes, does widespread and serious damage to the life of coastal waters.

And there are frequent outbreaks of gastrointestinal disease such as cholera, typhoid and infectious hepatitis caused by contaminated seafood and bathing water – particularly in areas where there are many carriers of the pathogens, and sewage treatment and disposal is inadequate. A major outbreak of cholera in Naples in 1973, for example, came from eating shellfish. An even greater epidemic of the disease which affected many millions of people in Latin America from 1991 to 1995 – and took 10,000 lives – started in the coastal cities of Peru.

Yet such dramatic outbreaks are responsible for only a small part of the toll of disease caused by sewage pollution. A new study sponsored by GESAMP and the World Health Organization (WHO) now shows that – far from just causing isolated, local problems –microbiological contamination of the sea has precipitated a health crisis with massive global implications.