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Worsening droughts could increase arsenic exposure for some Americans

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https://www.popsci.com/environment/arsen...r-drought/

EXCERPTS: Recent research from the US Geological Survey (USGS) suggests that droughts, particularly the prolonged kind happening in parts of the US, could increase the risk of harmful arsenic exposure for people that rely on well water.

Hundreds of millions of years ago, the baseline quality of your drinking water may have been set in stone, literally. Arsenic is a common groundwater contaminant, largely because of local geology. In Maine, for instance, the formation of the Appalachian Mountains and volcanic activity came together to concentrate arsenic and other metals into cracks inside the bedrock, explains Sarah Hall, a geologist at College of the Atlantic in Bar Harbor. From those fissures, subtle shifts in acidity, temperature, or water flow rates can draw contaminants out of the rock and into underground aquifers.

And it’s not just Maine. In many parts of New England, the Midwest, and the Southwest arsenic levels above the 10 parts per billion (ppb) federal level are particularly common—posing an especially big problem for families that rely on well water, which can be contaminated without homeowners knowing it.

Arsenic exposure can cause a litany of health issues, including bladder and lung cancers, heart problems, lung infections, immune system depression, and cognitive decline in children, says Bruce Stanton, a molecular physiologist at the Geisel School of Medicine at Dartmouth in New Hampshire.

[...] The study offers a couple of explanations for why droughts might increase the risk of arsenic exposure through well water in some areas. During droughts, groundwater levels decrease. This change in volume can cause shifts in water chemistry, like increased acidity. Because metals leaching out of rock is a chemical reaction, changes in water chemistry can speed up the process. Less groundwater also means contaminants already present in the water become more concentrated. So, even if a drought doesn’t change the total amount of dissolved arsenic in a well, every glass of water from that well may contain more.

The USGS research also partially accounted for human responses to drought that might lead to increased exposure in certain regions. During periods of extended drought in California, for instance, surface water is limited and more water is pumped from underground to meet the state’s needs, says Rich Pauloo, a hydrologist studying the issue. Overpumping can cause the land itself to sink, in the process squeezing natural arsenic out of clays and into groundwater used for drinking, according to a 2018 study published in Nature Communications.

Lombard’s study model was based on previously observed drought conditions, but climate change is projected to continue to increase the number and intensity of droughts worldwide... (MORE - missing details)
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