CSE- Health Environment Newsletter March-April 2003

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But many drawbacks are attached to these kits, which over-shadow their merits. Arsenic concen-tration is measured in ppb, which requires a high degree of accuracy and reliability in the instrument. No kit has been able to achieve that level of efficiency till now. ¹⁰ They give false positive results (arsenic detected even in its absence) and false negative results (presence of arsenic not detected), of which the latter has more serious implications. The kits are largely based on various chemical reactions, the results of which are tallied with colour compare charts, which can lead to confounding results. ¹¹ In addition, direct sunlight alters the colour of the strips used for colour comparison. ¹² The kits generate harmful arsine gas (a mixture of arsenic and hydrogen) along with hydrogen gas. Both are toxic and destroy red blood cells and cause kidney damage. ¹³ With a wide range of kits available in the market, an evaluation procedure for them becomes imperative but does not exist. "We have no plans of undertaking an evaluation of the kits," says U C Srivastav, head, chemicals department, Bureau of Indian Standards, New Delhi.¹⁴ Therefore, there is no strict protocol underlying as to which particular method is best or which particular kit ought to be recommended.

Treating water
Various processes to remove arsenic from water
Process Co-precipitation Aluminium and ferric salts are added to precipitate arsenic in raw water. These precipitates are removed after they settle down.	Advantages • Can be used at household and community level • Chemicals easily available • Low capital cost	Disadvantages • Problem of toxic sludge disposal • Requires trained operators • Medium removal of trivalent arsenic
Adsorption Chemicals such as activated alumina, iron-coated sand, ion-exchange resins are used to adsorb arsenic.	• Commercially available • High arsenic removal efficiency • Sludge disposal is a problem	• Needs regular replenishment of chemicals • pH needs to be monitored regularly • Poor after-sale service in villages
Membrane technologies Raw water is passed through a membrane that filters out arsenic. Some common technologies are reverse osmosis and electrodialysis.	• High arsenic removal efficiency • Low space requirement	• High initial investment • High operation and maintenance cost • Requires pre-treatment of water
Source: CPCB 2002, Arsenic contamination in groundwater and its control, CPCB, Delhi, p 19.

Low-cost options for treating water
With the availability of a number of low-cost methods, the arsenic level in water can be reduced considerably so as to make it fit for consumption. Once an area is identified as arsenic affected, one of these methods can be deployed for removing arsenic from water (see Table: Treating water).

Prevention is better than cure
With no specific medical treatment currently available to cure arsenic related diseases, arsenic mitigation strategy is more about prevention than cure. Identifying arsenic-affected areas and using low-cost options for treating arsenic-laden water, coupled with judicious use of groundwater for both drinking and irrigating purposes, can go a long way in checking the spread of arsenic.

References

1. Dipankar Chakraborti undated,
http://www.soesju.org/arsenic/arsenicContents.htm?f=facilities.htm, as viewed on November 19, 2004.

2. Ritu Gupta 2004, More Arsenic, in Down To Earth, Society for Environmental Communications, New Delhi, Vol 13, No 8, pp 26-36.

3. Dipankar Chakraborti undated,
http://www.soesju.org/ arsenic/arsenicContents.htm?f=facilities.htm, School of Environmental Studies, Jadavpur University, Kolkata, as viewed on November 19, 2004.

4. Surojit Mahalanobis 2004, Arsenic slouching under Ganga-Brahmaputra Belt, in The Times of India, Bennett, Coleman and Co. Ltd., New Delhi, June 19.

5. Allan Smith 1992, Cancer risks from arsenic in drinking water, in Environmental Health Perspectives, Public Health Service, US Department Of health and human services, USA, Vol 97, pp 259–267.

6. Andrew Meharg 2004, Arsenic in rice – understanding a new disaster for South East Asia, in Trends in Plant Science, Vol 20, No 20, pp 1-3.

7. National Chemicals Laboratory 2001, Final Report on Arsenic Field Test Kit, Pune, April, p 2.

8. Kailash Khulbe 2004, Scientist, Industrial Toxicology Research Centre, Lucknow, October 12, personal communication.

9. Raj Kumar Daw 2004, Project Officer, HTN, United Nations Children’s Fund, New Delhi, October 20, personal communication.

10. Manoj Kumar 2004, Scientist, Tara Environment Monitoring Facility, Development Alternatives, New Delhi, October 7, personal communication.

11. Hach undated, Hach EZ arsenic test kit, HACH Company, Colorado, USA, p 3.

12. Oklahoma Poison Control Centre 2002, Arsine Fact sheet,
http://www.oklahomapoison.org/prevention/arsine.asp , as viewed on November 3, 2004.

14. U C Srivastav 2004, Head, Chemicals Department, Bureau of Indian Standards, New Delhi, October 15, personal communication.

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