A new study founds that the world may be at risk of drinking arsenic-contaminated groundwater.
Researchers made a global map by combining environmental, climate and geologic data with machine learning. This shows the groundwater arsenic concentrations likeliest to exceed 10 micrograms per litre which are the declared safe drinking water limit by WHO.
Arsenic is present in fragment amounts in different types of rock and soil. Leaching of this from the soil into the groundwater becomes harmful to humans. Various chemical processes result in leaching. Long-term exposure to the skin can cause skin lesions and cancer.
Earlier, scientists have estimated several hot spots of groundwater arsenic contamination but lacked data in other regions. So, based on dozens of different environmental aspects, from temperature to soil age to pH, an environmental scientist Joel Podgorski & a hydrologist Michael Berg, created a high-resolution global map for arsenic-contaminated water.
Podgorski says, “In the last 12 years, there’s a lot more data that has become available.”
Podgorski & Berg gathered up data from the other eight studies, and then to create predictions of the arsenic risk of 1 km2, they used random forest method which is a machine learning technique. Then to create the final map, scientists averaged the results of approx. 10,000 different predictions.
Podgorski says, “The result is really the first truly global risk map of arsenic contamination in groundwater.” He added, “This is a basic message of the map; it should be used as a guide to more testing.”
The map depicts several hot spots on arsenic contamination, especial in Asia and South America. Also, it shows a possible prone risk in less well-studied regions like central Asian countries (Kazakhstan & Mongolia), the Arctic and many countries around the Sahara.
“Risk maps based on statistical models, such as the map created by Podgorski and Berg, cannot predict individual well water arsenic concentrations,” writes geochemist Yan Zheng of the Southern University of Science and Technology in Shenzhen, China, in a commentary in the same issue of Science. Also, she writes, “the map’s the greatest value lies in identifying potential areas at risk that have not had testing.”