The poor's lack of access to sanitation threatens to undermine the health benefits they have gained from access to clean water, the United Nations said on Tuesday.

More than 90 per cent of the world population has access to clean water, but 2.4 billion people, most in rural areas, continue to live without toilets, the U.N. children's agency UNICEF and World Health Organisation (WHO) reported.

"Until everyone has access to adequate sanitation facilities, the quality of water supplies will be undermined and too many people will continue to die from waterborne and water-related diseases," said Maria Neira, head of public health at WHO.

World leaders are due to adopt a set of development objectives - known as the Sustainable Development Goals - in September that include ending poverty, reducing child mortality and tackling climate change, to replace the eight expiring U.N. Millennium Development Goals (MDGs).

Some 2.6 billion people have gained access to clean water and 2.1 billion gained access to toilets since 1990, but large gaps remain, especially in sub-Saharan Africa, according to the report.

In countries like Chad, Mali, Nigeria or Central African Republic less than half the population has access to toilets, the report said.

Access to clean water and adequate sanitation is critical in preventing 16 tropical diseases that cause blindness, disfigurement and death and affect more than 1.4 billion people in 149 countries, the report said.

One billion people worldwide have no choice but to defecate in the open, not into a designated toilet. As a result, 161 million children are threatened with poor health.

The goal on halving the proportion of people without access to clean water was reached ahead of the 2015 deadline, but sanitation goals remain out of reach. The U.N. cites a lack of affordable facilities for the poor, as well as inadequate efforts to change behavior.

"Though we are glad to see overall progress, this data tells us that very little has changed for the world's poorest people when it comes to access to water and sanitation," Girish Menon, deputy chief executive of the global water charity WaterAid, said in a statement.

To eliminate open defecation by 2030, which is the new development deadline, the current rate of progress will have to double, said the U.N.

WHO and Unicef said it is vitally important to learn from the uneven progress of the 1990-2015 period to ensure that the SDGs close the inequality gaps and achieve universal access to water and sanitation. To do so, the world needs:

•    Disaggregated data to be able to pinpoint the populations and areas which are outliers from the national averages;

•    A robust and intentional focus on the hardest to reach, particularly the poor in rural areas;

•    Innovative technologies and approaches to bring sustainable sanitation solutions to poor communities at affordable prices;

•    Increased attention to improving hygiene in homes, schools and health care facilities. – TradeArabia News Service and Reuters