Sunday, 23 November 2014

Even the goddamn rice

Bangladesh doesn't really have a bad press in The West (and I don't mean [West] Pakistan which used to exercise braggart rights over their Bengali co-religionists) it's rather that they have no press at all.  160 million people are effectively invisible to us here in Ireland. It's tough out there boxed in by India and exposed to the sea.  I've indicated how two of the great rivers from the Himalaya, Ganges and Brahmaputra, control the destiny of this densely populated country, not least by killing about 6000 citizens each year in floods.  While they wait for the end in the next big climate-change induced storm surge, the people must live and in order to live they must have food and water.  I've written recently about the terrible no-good-option deal they have with water&arsenic or water&dysenteric.  Turns out that the food is not much better for them.

Although it is the North of the subcontinent, Bangladesh is primarily a rice economy.  They get through 34m tons of it every year compared to only 4m tons of wheat.  It is possible to grow rice in a field and depend on the rain to satisfy its thirst for water, but yields are better for varieties that are grown in paddies.  The 30 October 2014 issue of Nature has an amazing supplement on rice which I've been reading with great interest. It turns out that rice is rather good at concentrating any arsenic that might be present in the water, and we've seen that there's a lot of that about in Bangladesh.  When rice is grown under water in paddies, the soil turns anaerobic and that tends to solubilise the arsenic so it can be more readily be taken up by the plant. Upland rice cultivation in 'dry' soil watered by rain can reduce the arsenic concentration by 30x, so clearly that is one option, but Bangladesh is rich in flat alluvial soils ideal for paddy rice and has limited hectares of suitable upland soils. Once inside, the arsenic tends to accumulate in some tissues more that others and one of those tissues is the seed-husk of brown rice. One way to reduce the intake of arsenic by humans is therefore to mill off the husk and eat white rice which has 10x less arsenic than brown rice, but the husk is full of niacin which in economies on the edge is a vitamin in chronic short supply.

Another solution hinges on the observation that some of the thousands of varieties and strains of rice accumulate much less arsenic than others.  Simple but extensive and comprehensive genetic experiments suggest that the arsenic-clearing trait might be a single gene.  They have no idea yet where the gene lies or how it works but the hunt is on.  Another nifty and elegant option is to encourage bacteria to create the gas tri-methyl-arsine from soil arsenic although that is unlikely to scale up any time soon as a way of detoxifying the soil.  Another microbial solution is to encourage the growth of bacteria that coat the rice roots with a layer of iron salts that inhibits the uptake of arsenic by the plants. That also has limited efficacy at the moment. Science has all these cards to shuffle in a deck of cause and effect that has dealt Bangladesh a poor hand; surely there is a workable solution.

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