Cancer-Causing Arsenic is Building Up in the World's Rice

Arthur T Knackerbracket has processed the following story:

Throughout the Yangtze River Delta, a region in southern China famed for its widespread rice production, farmers grow belts of slender green stalks. Before they reach several feet tall and turn golden brown, the grassy plants soak in muddy, waterlogged fields for months. Along the rows of submerged plants, levees store and distribute a steady supply of water that farmers source from nearby canals.

This traditional practice of flooding paddies to raise the notoriously thirsty crop is almost as old as the ancient grain's domestication. Thousands of years later, the agricultural method continues to predominate in rice cultivation practices from the low-lying fields of Arkansas to the sprawling terraces of Vietnam.

As the planet heats up, this popular process of growing rice is becoming increasingly more dangerous for the millions of people worldwide that eat the grain regularly, according to research published Wednesday in the journal Lancet Planetary Health. After drinking water, the researchers say, rice is the world's second largest dietary source of inorganic arsenic, and climate change appears to be increasing the amount of the highly toxic chemical that is in it. If nothing is done to transform how most of the world's rice is produced, regulate how much of it people consume, or mitigate warming, the authors conclude that communities with rice-heavy diets could begin confronting increased risks of cancer and disease as soon as 2050.

Our results are very scary," said Donming Wang, the ecological doctorate student at the Institute of Soil Science, Chinese Academy of Sciences who led the paper. It's a disaster ... and a wake-up call."

[...] After nearly a decade of observing and analyzing the growth of the plants, the researchers discovered that the combination of higher temperatures and CO2 encourages root growth, increasing the ability of rice plants to uptake arsenic from the soil. They believe this is because climate-related changes in soil chemistry that favor arsenic can be more easily absorbed into the grain.Carbon-dioxide enriched crops were found to capture more atmospheric carbon and pump some of that into the soil, stimulating microbes that are making arsenic.

The more root growth, the more carbon in the soil, which can be a source of food for soil bacteria that multiply under warming temperatures. When soil in a rice paddy is waterlogged, oxygen gets depleted, causing the soil bacteria to rely further on arsenic to generate energy. The end result is more arsenic building up in the rice paddy, and more roots to take it up to the developing grain.

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