BANGKOK, Thailand - Myanmar's cyclone-devastated Irrawaddy delta and Indonesia's Sumatra island face high risks of arsenic contamination in groundwater that could cause cancer and other diseases in residents, according to a new study.

Using a digitalized model that examines geological features and soil chemistry in Southeast Asia, researchers writing in the peer-reviewed journal Nature Geoscience mapped several likely hot spots that had never been assessed for arsenic risks.

"Obviously, there is concern," said Michael Berg, one of the five authors, who is a senior scientist at the Swiss Federal Institute of Aquatic Science and Technology in Dubendor, Switzerland. "If you look at our data, there is risk of arsenic in the ground water."

Arsenic, especially in drinking water, is a global threat to health, affecting more than 70 countries and 137 million people. The country worst affected is Bangladesh, where hundreds of thousands of people are in danger of dying from cancers of the lung, bladder and skin.

Odorless and tasteless, arsenic enters water supplies from natural deposits in the ground or from agricultural and industrial practices. Arsenic is poisonous when consumed in high doses, but even smaller amounts can cause cancer, skin problems and abnormal heart rhythms.

Berg and the other authors determined a high risk of arsenic contamination exceeding World Health Organization guidelines in Myanmar's Irrawaddy delta, a low-lying area hit by a May cyclone that killed at least 84,537 people.

Their models also found that 38,610 square miles of Sumatra's east coast was at risk as well as the Chao Phraya river basin in central Thailand — although the dangers in the Chao Phraya were lower because residents in the area tap deeper aquifers.

Researchers said regions with organic-rich sediment containing silt and clay have a higher likelihood of arsenic contamination.

"These are very young sediments. Only in young formation do we find that arsenic can be released from the sediment," Berg said Friday, adding that arsenic in soil that is much older has been mostly washed away.

Berg said he hopes the maps they developed could serve as "a red flag" for authorities to take precautions before building wells or other water facilities in areas deemed at high risk of arsenic contamination. Until now, testing for arsenic has been rare in many regions because it is costly and time consuming, he said.

Lex van Geen, a geochemist at Columbia University's Lamont-Doherty Earth Observatory who has studied arsenic contamination in Bangladesh and did not participate in the study, said it should be lauded for drawing attention to areas where little research has been done on the arsenic threat, such as Myanmar. But he said the digital models do not identify areas well below the surface where water quality is good.

"Using the mapping based on surface geology will identify settings where arsenic could be high in shallow groundwater," van Geen said. "What it can't tell you is how deep you might have to go to reach the low arsenic water, which is really what matters from a mitigation point of view."

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