The world’s largest sanitation initiative which provided almost 25,000 individuals in rural with access to toilets did not reduce exposure to fecal pathogens or decrease the occurrence of diarrhoea or child malnutrition, a new study has claimed.

“The programme is effective in building latrines, but not all households participate,” said lead author Professor Thomas Clasen from Emory University, Atlanta, US and the School of Hygiene & Tropical Medicine in the UK, who conducted the study in 100 rural villages in Odisha.

“Moreover, many householders do not always use the latrines. This, combined with continued exposure from poor hygiene, contaminated water, and unsafe disposal of child feces, may explain the lack of a health impact,” said Clasen.

Worldwide, around 2.5 billion people lack access to basic sanitation facilities such as a latrine, a third of whom live in India, researchers said.

Two-thirds of the 1.1 billion people who practice open defecation and a quarter of the 1.5 million who die every year from diarrhoeal diseases caused by poor hygiene and sanitation also live in India, they said.

This cluster randomised trial involved 9,480 households (50,951 individuals) in 100 rural villages in Odisha, with a child younger than 4 years or a pregnant woman.

Households in 50 villages were randomly assigned to receive the sanitation intervention in early 2011; control villages received the intervention after a 14-month surveillance period.

The intervention increased the average proportion of households in a village with a latrine from 9 per cent to 63 per cent, compared an increase of 8 per cent to 12 per cent in control villages.

However, the researchers found no evidence that the intervention protected against diarrhoea in children younger than 5 years: 7-day prevalence of reported diarrhoea was 8.8 per cent in the intervention group (data from 1,919 children) and 9.1 per cent in the control group (1,916 children).

The intervention did not reduce the prevalence of parasitic worms that are transmitted via soil and can cause reduced physical growth and impaired cognitive function in children. There was also no impact on child weight or height – measures of nutritional status, researchers found.

The researchers say that further studies are needed to identify why the intervention failed to improve health, but suggest a number of possible explanations including insufficient coverage and inconsistent use of latrines, or that a lack of hand-washing with soap or animal feces could also be contributing to the disease burden.

“This rigorous assessment is important, because it provides the best evidence so far for the uncomfortable conclusion that well-funded, professionally delivered sanitation programmes, even when they reach coverage levels that are quite commendable for large scale interventions, do not necessarily improve health,” Dr Stephen Luby, from in the US, said.

The study was published in the journal Lancet.