Well over half the world's population -- 4.4 billion people -- cannot access safely managed drinking water, a new study has shown.

Around 4.4 billion people is more than double the estimates made in by The World Health Organization (WHO) in 2022.

But the report only examined access to clean water in low and middle-income countries, meaning the figure would likely be greater once poor access in higher income countries is accounted for.

"The information which we have points towards very high rates of contamination," said lead researcher Esther Greenwood from ETH Zurich, Switzerland.

The new figures come from more sophisticated methods to collect data about water contamination.

The risks of drinking contaminated water

Unsafe drinking water has a risk of causing a variety of severe water-borne diseases like cholera, dysentery, typhoid, and less severe diseases like norovirus.

To be considered "safely managed", water must be available on demand, on premises and contaminant-free, and designed to deliver safe water.

The majority of those without access to such services are limited by likely fecal contamination, according to the research published in the journal Science.

Greenwood's study was conducted to plug existing data gaps. Satellite observations and household survey information were analysed using artificial intelligence to define areas of safe and unsafe water access.

As well as representing more than half the global population, the 4.4 billion people who don't have access to safe drinking water account for two-thirds of those living in low and middle-income countries.

Greenwood says the findings are conservative as the data are samples taken on a single day rather than over extended timescales.

"It could actually be that the numbers are even higher," she said.