Many sneak out discreetly under the cover of darkness. Some make their way to the fields while some hide behind shrubs and bushes. Then there are those living in some of the world's most crammed urban slums. Privacy or space is not an option here. They take to public spaces, busy roadsides and even railway tracks.
From holding their heads down to pulling a cloth over their faces - they attempt to cover their embarrassment and shame. Every day, 1.1 billion people suffer the indignity of defecating in the open.
From Asia to Africa and Latin America - open defecation exists in all regions across the developing world. And almost everywhere shit is the unspoken "dirty" word, a taboo akin to sex that is rarely acknowledged in public or seldom talked about even in the most private conversations.
In rural India they prefer saying "going to the jungle" and in Cambodia they call it "folding legs". So stigmatised is the most basic biological function that colloquial expressions, code names and even numerical references are used in all parts of the world to steer clear of dealing with the muck.
It is thus not surprising that despite one out of every seven persons on this planet defecating in the open, the issue has never been a priority on the global agenda. Sanitation does not make news or political careers. It even lacks the "emotional pull" to be a successful development campaign.
It has ample potential to raise a stink, yet it has not inspired clever virals, created Twitter armies or least of all spurred the thought of a sweeping revolution by hundreds of millions who are affected by it.
More mobiles than toilets
The list of nations where the problem is most acute extends from the most rapidly growing economies like China, India and Brazil to some of the poorest nations such as Nepal and Niger. India alone accounts for over 600 million people or almost 60 per cent of all those practising open defecation in the world. There are more mobile phones in India than there are toilets.
China, Indonesia and Pakistan collectively account for more than 110 million which is nearly the entire population of the United Kingdom and France put together. Even as Brazil prepares for its crowning moment on the world stage by hosting the next FIFA World Cup and the Olympics, it is faced with the tough challenge of tackling over 7 million of its population defecating in the open.
Often cultural and behavioural attitudes are cited by authorities when confronted with such embarrassing figures. This is true to some extent as customs and traditional beliefs play a major rule in wide acceptance of the problem as perfectly normal.
In places like Cameroon's Far North Region many of those who practice defecation in the open believe they are fertilising the arid soil. Some refuse to dig latrines in their houses for fear of "witches". However, the complete picture is quite different and hugely complex.
Toilets are essentially part of the larger problem of water and sanitation which has remained a silent crisis despite global efforts. One in 10 of the world's population has no access to safe water. The figure spirals to 2.5 billion people who do not have access to adequate sanitation, almost two fifths of the world's population.
Construction of large numbers of modern toilets in remote rural areas in Asia and Africa has been tried with spectacular failures. Modern flush toilets, for example, use 10 times the average daily drinking water requirement - and are therefore hopelessly ill-suited to countries and villages which have virtually no access to water and non-existent sewerage networks.
An average person in the United States uses around 570 litres of water per day. Contrast this against 1.1 billion people who live more than a kilometre away from their main water source and survive on just five litres of unsafe water a day.
Streets in Delhi's poorer suburbs in India often turn into violent battlefields as people desperately fight for every drop of drinking water delivered through tankers during peak summer months.
People living in the slums of Jakarta, Manila and Nairobi pay 5 to 10 times more for water than those living in high-income areas in those same cities and more than consumers in London or New York.
Health and economic impact
The consequences of poor sanitation on public health are startling. Every day almost 2,000 children die from diarrhoea caused by inadequate sanitation, unsafe water and poor personal hygiene. The disease kills more children than AIDS, malaria and measles combined.
In Africa, 115 people die every hour from diseases linked to contaminated water, poor sanitation and bad hygiene. The impact of poor sanitation is so widespread that at any given time, half the hospital beds in the developing world are filled with people suffering from one or more of the main diseases associated with dirty water and poor sanitation.
All this involves a huge economic cost. According to the World Bank, India alone loses a staggering US $53.8bn each year to economic impact of inadequate sanitation. This cost stands at nearly 4 per cent of its GDP for Pakistan and $5.5bn for 18 African countries where open defecation is practised.
There are robust arguments in favour of spending more on sanitation. According to UK's Department for International Development (DIFD) every $1 invested in improved sanitation, translates into an average return of $9.
Those benefits are experienced specifically by poor children and in the disadvantaged communities that need them most. There is also evidence to suggest that sanitation and hygiene promotion are among the most cost effective measures for controlling endemic diarrhoea ranking higher than many other health interventions, including combating HIV/AIDS, tuberculosis and malaria.
Disparities and inequity
Extensive research and expert data on the state of world's sanitation are not in short supply and neither are suggestions of an effective solution, yet not enough has translated into action on the ground.
According to the UN, 1.8 billion people have gained access to improved sanitation since 1990. However, the steady growth in population, particularly in the developing countries, has meant that the absolute number of people defecating in the open has consistently remained above the one billion mark.
It is almost certain that the world will fail to meet the Millennium Development Goal of halving the proportion of people without sustainable access to safe drinking water and sanitation by 2015.
But what is more worrying is the element of disparity and inequity in the progress that is being achieved as part of the global efforts to meet this seemingly insurmountable challenge.
Invariably, in all situations it is the poorest and the most marginalised who have benefited the least from efforts to deal with water and sanitation problems. They disproportionately continue to suffer inadequate or no sanitation.
The 2012 update on global "Progress on Drinking Water and Sanitation" issued by UNICEF and WHO outlines major disparities. The poorest 40 per cent of the population in Southern Asia have barely benefited from billions of dollars spent on improvements in sanitation so far.
Similarly, the poorest 60 per cent in sub-Saharan Africa are largely denied the comforts and health benefits of a piped drinking water supply on premises. The gap between rural and urban sanitation are even more pronounced than those in drinking water supply.
Globally, nearly 80 per cent of the urban population uses an improved sanitation facility, compared to just 47 per cent of the rural population.
Even among those who are worst affected, women and girls bear the biggest burden of lack of safe water and sanitation. In rural Africa, for example, women spend one fourth of their time collecting water, as they walk at least five miles to the nearest water source. This time doubles in the dry season.
Strict social codes in many societies mean where latrines are not available, women and girls only step out after dark to defecate, exposing themselves to a greater risk of harassment and sexual assault.
With safety being a real concern they often delay or ignore their natural body functions increasing the likelihood of health problems such as urinary tract infections, chronic constipation or mental stress particularly during menstrual cycles.
Lack of toilets results in adolescent girls routinely pulling out of schools in Asia and Sub Saharan Africa. It thus acts as another debilitating barrier for girls to access education thereby severely limiting their chances in life.
Sanitation a human right
In 2010, the UN General Assembly for the first time explicitly recognised the human right to water and sanitation. The UN resolution serves as an emphatic acknowledgement that safe drinking water and sanitation are indispensable to sustain life and health, and fundamental to the dignity of all. It thus makes a distinction that water and sanitation are not just development challenges but human rights creating entitlements and obligations.
The human rights approach is particularly of concern to people who do not have access to safe sanitation. It puts the larger issue of inequalities associated with water and sanitation at the centre of human rights framework and attempts to reach out to the most vulnerable, such as children, women, people with disabilities, the chronically ill or the poorest of the poor.
A number of governments have established a plan of action aimed at progressive realisation of access to sanitation for all. Organisation for Economic Co-operation and Development (OECD) estimates that $35 trillion capital is required globally to finance investment in key infrastructure for water and sanitation.
Several countries in Sub-Saharan Africa and South Asia are already facing acute financial shortfalls in meeting their requirements. Additionally, many countries are also grappling with their ability to effectively use available funding to deliver sanitation.
Constructing toilets alone does not guarantee their use, nor results in improved sanitation and hygiene. Conventional approaches to sanitation have involved offering subsidies as an incentive. But this does not ensure long-term sustainability and creates dependency on financial assistance.
Learning from their experience, development organisations like Plan International are focusing on community led approach to sanitation which shifts the focus from toilet construction for individual households to the creation of "open defecation-free" villages.
Educating communities, that as long as even a minority of people continue to defecate in the open, everyone is at risk of disease. This is an essential part of creating the desire for change.
The basic practice of washing hands before meals and after defecation can save hundreds of thousands of lives. Plan's experience has shown that the ownership and sustainability of sanitation can be effectively managed by mobilised communities.
Sanitation is not merely a development wish list; it is a fundamental requirement on which several other aspects of human development rest. It directly affects people's survival, health, education and economic potential of nations.
The scandal of more than a billion defecating in the open every day flies in the face of modern achievements from space programmes to universal access to mobile phones. Human dignity is compromised daily for the millions who have to defecate in the open, but the shame is certainly not theirs.
Davinder Kumar is London based award-winning development journalist and press officer for global child rights organisation Plan International. He is also a Chevening Human Rights Scholar.
Follow him on Twitter: @davtox