Rising Sea Levels Increase Threat Of Arsenic In Drinking Water

(Bloomberg) —Rising seas due to climate change could exacerbate the threat of arsenic in drinking water, according to a study published in PLOS ONE in January. Researchers focused on arsenic in well water in Bangladesh, where up to 97% of the population relies on such water for drinking.

Arsenic occurs naturally in the earth’s crust, but how much arsenic is present in groundwater depends on geology, fertilizer habits and land use patterns, among other factors. (Industrial activities like tanning leather release arsenic, for example.) The researchers determined that sea level rise can increase even modest levels of arsenic due to a phenomenon known as saltwater intrusion.

Seawater can ordinarily only move so far inland; the saltwater-freshwater meeting point is known as the “salt front.” When sea levels rise, though, that front can move inland as the heavier saltwater pushes the groundwater table up from below and as storm surges and high tides flood more land and send saltwater into groundwater supplies from above. Saltwater is better at dissolving certain minerals than freshwater — picture a car corroding after it’s exposed to road salt — which means even small increases in groundwater salinity can cause more arsenic to dissolve.

The PLOS ONE study focused on Bangladesh because of groundwater’s importance to the country’s drinking supply, and because flooding is already prevalent during monsoon season. “Tens of millions of people” in Bangladesh are drinking well water with arsenic concentrations above the safety threshold identified by the World Health Organization, the researchers note.

According to the WHO, arsenic is naturally present at high levels in groundwater in countries that include Bangladesh, Argentina, China and the US.