Loo La La! It's WC gone mad in Paris

It's not just fashion making a splash in the French capital this week. John Lichfield on a show that celebrates the art of the toilet

To pee in the street, in the 4,000 vespasiennes, or public urinals, was once a prerogative of the Parisian male. All but two of the scarcely private pissoirs have now vanished but the toilet as a public spectacle has made a triumphant return – in photographic form – to the French capital. A free, outdoor exhibition called Chiottissime! – loose translation "Bogissimo!" or, perhaps, "The Bog Picture" – is amusing, and educating, passers-by on the Boulevard de la Bastille in eastern Paris until 20 October. It brings together 46 images from 31 countries – including the work of such celebrated photographers as Robert Doisneau and Willy Ronis – which illustrate some of the oddities and inequalities of one of the most urgent of human activities.

The exhibition has been organised by an unlikely sponsor of the arts, a public sewage company created 40 years ago to serve the greater Paris area, SIAAP (Syndicat interdépartemental pour l'assainissement de l'agglomération Parisienne). Although the subject is treated with humour, and with delicacy, the exhibition also seeks to make a serious point. Toilets are as much an indicator of global disparity as hunger or life-expectancy. More than 2.6 billion people have no access to proper toilets and more than one billion have no toilets at all. The images range from a ramshackle floating wooden public toilet in Bangkok to the 24-carat gold loos in the luxury shop chain owned by the Hong Kong millionaire SW Lam. Mr Lam once caused a panic on the world gold market by threatening to melt down his toilets.

Chiottissime!, an expanded version of an exhibition shown for Unicef (the UN Children's Fund) in Belgium last year, has been created by the French writer, film-maker and environmental campaigner François Cuel. "The exhibition is meant to make people smile but also to invite them to think," he told The Independent. "Access to proper toilets, and more generally to water, is a privilege denied to many people."

Beyond that, he said, he hopes it will make passers-by – and intentional visitors – consider some of the curiosities, and ironies, of "the smallest room". "Our belief, not to mince words, that shitting should be a private act is relatively new," he said. "Until the late-18th century, three or four people would happily relieve themselves together. All that changed with the prudery brought by the French Revolution and with the invention of the water closet in Britain in the 19th century."

The toilet has now become a sanctuary and a paradox, he said, "the only place that we are officially allowed to be alone ... a place to read and think, a place of refuge for bored workers or battered children and wives. In the Lebanese civil war," he continued, "the toilet was often the only place that you could avoid the flying bullets."

Mr Cuel has a taste for the surreal. One of the images he has chosen shows an elaborate toilet and washbasin standing alone, with no obvious water connection, in the middle of the Sahara Desert in Morocco. Another image was posed by German photographer Gerhard Westrich, as part of a series on the home-life of superheroes. It shows Spider-Man sitting on a toilet (reading a book, of course). Another exhibit shows urinals in Iceland after the banking crisis of 2008. Photographs of the faces of senior Icelandic bankers have been placed in the firing line. The Parisian vespasienne (named after a Roman emperor who supposedly placed a tax on peeing) is not forgotten. There is a wonderful Doisneau photograph from the 1950s of five men relieving themselves, lightly screened from a jumble of people and vegetables in the old Paris wholesale market, Les Halles.

Les Halles has long gone. Only two vespasiennes survive. One of them is pictured in the exhibition, smeared in graffiti. It stands outside the Santé prison in southern Paris for the convenience of the police officers who patrol the surrounding streets day and night. The vespasiennes have been eliminated because, being male only, they were regarded as offensive and unfair to women.

They have been replaced by ugly cylinders with automatic doors which are unisex and free but always out of order. Mr Cuel, the curator of the exhibition at the Boulevard de Bastille (12th arrondissement, Métro Bastille) said this was a case of history repeating itself. The vespasiennes originally doubled as advertising billboards for theatres and music halls.

Women in the mid-19th century complained, understandably, that they could not read the listings while the pissoirs were in use. Thus was invented the "Morris column", the cylindrical entertainment billboard which survives in Paris, and many other cities, to this day.