Overflowing cities: The State of the World's Toilets 2016

Human beings are now largely an urban species: for the first time in history, more than half of the world's population (54%, or 3.9 billion people) lives in towns cities and megacities. By 2050, that's expected to rise to two thirds.

Many new urbanites, and particularly the poorest are not moving into gleaming apartment blocks or regenerated post-industrial areas. They are arriving – or being born into – overcrowded, rapidly expanding slums.

Economic growth is usually driven by urbanisation, and all industrialised countries already have a mostly urban population. This means that nearly all the current urban population is happening in developing countries. UN Habitat estimates that more than one-third of the developing world's urban population – over 863 million people – live in slums. Often, city planning and infrastructure building have been unable to keep pace.

In this year's State of the World's Toilets, we look at some of the world's worst countries for urban sanitation, and some of the jobs that are created when the challenge is addressed head-on.

With only 14 years to achieve the UN's Global Goal 6 – to deliver safe water and sanitation to everyone everywhere by 2030 – there's no time to waste.