An author who opens her book clambering into a manhole wearing crotch-high, tungsten-soled waders is clearly not shy of a challenge. In this study of the parlous state of world sanitation, Rose George bravely and ably meets the challenge of writing about “shit”. (One quickly learns not to hide behind euphemisms.)

A book on this subject inevitably provokes disgust; this is not breakfast-time reading. But it also inspires outrage. Sanitation, we discover, is the world's biggest health crisis, easily outstripping malaria or HIV-Aids. Four in 10 people have no lavatory - not even a pigsty or a hole, just scrubland, a railway line or a plastic bag flung in a back alley.

Diarrhoea, as a result, has killed more children in the past decade than all the casualties of war since 1945. In one village in India, contaminated water ensured that 60% of women had skin disease or gynaecological infections. In another, 10% of girls went to school before they built clean facilities; afterwards, 80% attended. In London, New York and scores of developed cities around the world, raw sewage is still pumped into the seas and rivers. As George acutely observes, “The irony of defecation is that it is a solitary business yet its repercussions are plural and public.”

For daring to fling back the privy door, George deserves a medal. So, too, do the sanitary pioneers she tracks down and whose characters she wryly sketches with a few deft flicks of the pen. We meet engineers, inventors and campaigners, from the man dubbed South Africa's “minister for toilets” to the founder of India's sulabh convenience, who asserts that, while Gandhi came into people's homes via the spinning wheel, “we're entering through the toilet”. Most fascinating are the unshrinking encounters with frontline workers. In Mumbai, George drinks yellow water from a tin beaker in solidarity with outcaste latrine scavengers. In Dar es Salaam, she interviews the unloved “pit-scooper” or “frogman”. Without the efforts of people like him, we begin to understand, his city - all our cities - would fail.

The Big Necessity by Rose George
To buy this book at the offer price of £11.69 rrp £12.99 please call 0870 160 8080 or click here

Times Recommends

• The 100 Best Books of the Decade
• The Times picks the 50 best paperbacks of 2009
• The conversation: James Ellroy