Arsenic and Global Warming: The Good, the Bad and the Deadly

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Protest at water shortage in Chennai, India: the more people need water, the more groundwater can get depleted, the higher the arsenic risk
Protest at water shortage in Chennai, India: the more people need water, the more groundwater can get depleted, the higher the arsenic riskCredit: ARUN SANKAR / AFP

Global warming increases the probability that we’ll be drinking arsenic, especially if we live in Asia. At this point, between 94 million to 220 million people – of whom 94 percent live in Asia – are at risk of drinking water containing harmful levels of arsenic, according to a new map of global arsenic risk published Friday in Science. The map reveals previously unknown hot spots in central Asia, as well as broad areas of the Arctic and sub-Arctic. At low levels arsenic doesn’t hurt us, but at high levels it makes us sick or even dead.

And why might the risk get worse? So many reasons: heightened evaporation, causing concentration of contaminants; changes in water table; very importantly – over-exploitation of groundwater; and ever-growing populations requiring ever-more fresh water, whose sources are dwindling (and/or getting polluted). By the way, arsenic is tasteless and odorless.

Arsenic-laced water can kill after decades

While on the topic, in March a separate paper published in the Journal of the National Cancer Institute reported that arsenic in drinking water may have one of the longest dormancy periods of any carcinogen. A perfect if inadvertent lab to study this was Chile, where the people of Antofagasta suffered a sudden, significant increase in arsenic water concentrations in 1958, which was ameliorated by the construction of an arsenic removal plant in 1970. Checking mortality rates from lung, bladder and kidney cancer, the team concluded that increased risks continued to manifest 40 years after exposure reduction. “Our findings suggest that arsenic in drinking water may involve one of the longest cancer latencies for a human carcinogen,” the team wrote.

Hanoi, poster child for groundwater-arsenic link

In Vietnam, meanwhile, scientists using modeling demonstrated that increasing groundwater extraction to slake the thirst of the growing population of Hanoi is leading to arsenic pollution in the aquifer: arsenic-poor water can be replenished with arsenic-heavy water. If an aquifer is heavily tapped and if its replenishment comes from arsenic-heavy muds, there you have a cause, they demonstrated. A case in point is river mud regularly deposited at slower-flowing stretches of the Red River: organic matter, including bacteria in the mud, fueled a biogeochemical reaction, causing enhanced arsenic release into the aquifer underlying the Van Phuc village.

Arsenic caps in America helped

Americans are safer from arsenic in the water, according to a Columbia University study published in The Lancet Public Health – thanks to new arsenic caps handed down by the Environmental Protection Agency in 2006, reducing the arsenic allowance from 50 to 10 micrograms per liter. Compliance with the regulation led to a 17 percent decline in levels of urinary arsenic, the report found. Note, however, that nobody’s checking private wells, and that’s a significant factor because more than 45.5 million Americans draw water from their own wells, leaving perhaps 1.7 million at risk.

Elephant having a drink at a water tap in Allahabad, IndiaCredit: AP

If you drink arsenic, don’t smoke…

Oh, by the way, cigarettes will contain arsenic if that mineral is used in the pesticides used to grow tobacco free of pests. And research has shown that arsenic and cigarette smoking co-exposure increases the incidence of lung cancer by acting together to damage our DNA. This was tested in Syrian hamsters, but the results surely apply to us too. For what it’s worth, beef, fish and chicken may also contain arsenic from their feed – incredibly (with hindsight), Americans added arsenic to chicken feed in the 1940s and the additive took until the last decade to be phased out.

Global warming will increase arsenic component in rice

No newsletter on arsenic would be complete without mentioning rice. Yes! Global warming is also projected to increase the concentration of arsenic in rice, which is already notoriously rich in the inorganic compound. Is it a comfort that rice crops are expected to dramatically decline with climate change? No? In 2019, Stanford scientists projected that rice yields could plunge by 40 percent by 2100 and “changes to soil processes due to increased temperatures will cause rice to contain twice as much toxic arsenic than the rice consumed today.” Haaretz repeats that all rice, but especially brown, non-husked rice, contains a lot of arsenic – which is water-soluble. Wash your rice before cooking; cook in lots of water; and discard the excess water.

Growing rice in VietnamCredit: Reuters

Mississippi marshes pass point of no return

Another problem faced by coastal aquifers is encroachment by seawater. Now, a study from Tulane University, New Orleans, is noting the inevitable submersion of the remaining marshland in the Mississippi Delta, based on hundreds of sediment cores collected to examine how marshes responded to a range of rates of sea-level rise during the past 8,500 years. What they found is a tipping point beyond which a small upturn in the rate of sea-level rise leads to widespread submergence. In the last century, Louisiana has so far lost 2,000 square miles (5,000 square kilometers) of wetland; it has 6,000 square miles to go.

“The scary thing is that the present-day rate of global sea-level rise, due to climate change, has already exceeded the initial tipping point for marsh drowning,” said Torbjörn Törnqvist, lead author and Vokes Geology Professor in the Tulane Department of Earth and Environmental Sciences.

In the Mississippi marshesCredit: Charlie Brenner

Yes, you can use oilfield waste water for irrigation…

With a caveat. First the good news, all things being relative: Reusing the water from a specific California oilfield that’s been mixed with surface water to irrigate crops “does not pose major health risks” if the farmers grow boron-tolerant crops and keep mixing the oilfield water with freshwater to dilute the salts, researchers reported in the journal Science of the Total Environment. The caveat is that oilfield water does contain a lot of boron and salts, and if the farmer doesn’t keep on top of that – the soil will be ruined. It begs clarifying that this doesn’t mean all water from all oilfields can, even if diluted, serve to irrigate our food crops; elsewhere, the salinity in the water tends to be much higher. At least the oilfield water didn’t increase the arsenic in the crops.

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