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[SANET-MG] arsenic pollution of rice and drinking water in asia



August 6, 2004

Prof. Joe Cummins

“Arsenic pollution of drinking water and rice in Asia”

Asia is facing a growing disaster in the use of arsenic contaminated
ground water for drinking and in irrigation of rice paddies. Arsenic
pollution is a severe problem over Bangladesh/West Bengal (1) and in the
Red River Delta of Vietnam (2) but it is also a chronic problem in
Taiwan, China and Thailand (1). Most arsenic pollution is of natural
origin , amplified by drawing water from contaminated deep aquifers but
China has experienced arsenic pollution from burning high arsenic
containing coal (3). Arsenic has been shown (from studies in Taiwan) to
cause cancer and circulatory problems at very low levels, the cancers
observed include cancers of liver, lung, bladder and kidney (4). It has
been estimated that average arsenic pollution of drinking water in the
United States causes 3000 cancer cases per year (3).

In Asia the arsenic is problem amplified by the pollution of rice, the
prime food source ( (1,2,5). Arsenic has been accumulating in paddy soil
leading to contamination of the grain (5). Rice contributes to ,an
estimated, 30 to 60% of the dietary intake of arsenic in polluted
regions (5).

There is hope that rice strains can be selected that take in less
arsenic than do the varieties of rice currently in use. It has been
found that arsenic is sequestered on iron plaque on the roots of rice
varieties that accumulate reduced levels of arsenic in grain (5,6). Rice
paddies will continue to be polluted with arsenic in the soil because
there is no practical method known to remediate the vast expanses of
polluted soil. Breeding rice to reduce grain pollution seems to be an
effective first step towards improving the diet in polluted areas and
varieties with reduced grain input of arsenic are known.

There is a potential conflict in governmental and foundation programs to
develop and disseminate high iron grain to alleviate iron deficiency
among rice consumers. The high iron rice varieties currently under
development include amplifying ferritin in grain and solubilizing iron
using a phytase gene from a fungus (7).In the iron plaque rice varieties
arsenic reduced iron in shoots and roots while the varieties lacking
arsenic sequestering plaque did not have reduced iron in the presence of
arsenic(6). The iron enhanced grain designed to combat iron deficiency
are bound to contain high arsenic levels in the arsenic polluted areas
of Asia. It seems a devilish dealing to make high iron rice available at
the cost of elevated arsenic. A solution to the problems of iron
deficiency and arsenic poisoning should be sought that deals with both
problems together and not separately.

References

1.Meharg,A. and Rahman,M. Arsenic contamination of Bangladesh paddy
field soils: implication for rice contribution to arsenic consumption
2003 Environ Sci Technol 17,229-34

2.Berg,M,Tran,H,Nguyen,T,Pham,H,Schertenleib,R. and Giger,W. Arsenic
contamination of groundwater and drinking water in Vietnam: a health
threat 2001 Environ Sci Technol 35,2621-7

3. Liu,J Zheng,B, H. Aposhian,H,Zhou,Y,Chen,M,Zhang,A. and Waalkes,M.
Chronic Arsenic Poisoning from Burning high-Arsenic-Containing Coal in
Guizhou, China 2002 Environmental Health Perspectives 110, 119-22

4. Morris,R. Environmental Health Issues 1995 Environmental Health
Perspectives 103 (suppl 8) 1-14

5.Meharg,A. Arsenic in rice-understanding a new disaster for south-east
asia 2004 trends in plant sciences in press

6. Lui,W,Zhu,Y,Smith,E. and Smith,S. Do phosphorous nutrition and iron
plaque alter arsenate (As) uptake by rice seedlings in hydroponic
culture 2004 New Phytologist 162,481-8

7. Cummins.J. Pumping iron in transgenic rice 2004 Science in Society in
press

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