Read the passage carefully and answer the question. The amount of water in the world is limited. The human race, and the other species, which share the planet, cannot expect an infinite supply.…

Read the passage carefully and answer the question.

The amount of water in the world is limited. The human race, and the other species, which share the planet, cannot expect an infinite supply. Water covers about two thirds of the earth's surface admittedly, but most of it is too salty for use. Only 2.5% of the world's water is not salty, and two-thirds of that is locked up in the icecaps and glaciers. Of what is left, about 20% is in remote areas. Humans have available less than 0.08% of all the earth's water. Yet over the next two decades, our use is estimated to increase by about 40%.

In 1999 the United Nations Environment Program (UNEP) reported that 200 scientists in 50 countries had identified water shortage as one of the two most worrying problems for the new millennium (the other was global warming). We use about 70% of the water, that we have, in agriculture. But the World Water Council believes that, by 2020, we shall need 17% more water than is available if we are to feed the world. So, if we go on as we are, millions more will go to bed hungry and thirsty each night than do so already. Today, one person out of five across the world has no access to safe drinking water, and one out of two lacks safe sanitation. Today, and every day, more than 30,000 children die before reaching their fifth birthdays, killed either by hunger or by easily-preventable diseases. And adequate safe water is the key to good health and a proper diet. There are several reasons for the water crisis. One is the simple rise in population and the desire of better living standards. In China, it takes 1,000 tonnes of water to produce one tonne of wheat. Another is the inefficiency of the way we use much of our water. Irrigation allows wastage on a prodigal scale, with the water trickling away or simply evaporating before it can do any good. And pollution is making more of the water that is available to us unfit for use. The Aral Sea in Central Asia is one of the starkest examples of what pollution can do, to the land as well as to the water. Increasingly, governments are seeking to solve their water problems by turning away from reliance on rainfall and surface water, and using subterranean supplies of groundwater, instead. But that is like making constant withdrawals from a bank account without ever paying anything into it. And using up irreplaceable groundwater does not simply mean the depletion of a once and for all resource. Rivers, wetland and lakes that depend on it can dry out. Saline seawater can flow in to replace the fresh water that has been pumped out. And the emptied underground aquifers can be compressed, causing surface subsidence - a problem familiar in Bangkok, Mexico City and Venice. There are some ways to begin to tackle the problem. Irrigation systems which drip water directly onto plants are one, precision sprinklers another. There will be scope to plant less water-intensive crops. And perhaps desalination may play a part though it is energy-hungry and leaves quantities of brine for disposal.

What percentage of world population, according to the author, has no access to safe drinking water?