West Bengal || Bangladesh
Middle Ganga Plain, Bihar ||
FIELD TESTING KITS FOR ARSENIC: HOW EFFECTIVE ARE THE MILLION-DOLLAR PROJECTS?
PRACTICAL PROBLEMS IN FIELD-KIT MEASUREMENT
Field Kit a Semi-Quantitative Concept
1. At present in India and Bangladesh the permissible limit of arsenic in drinking water is 0.05 µg/l and we are expecting to know from Field- Kit data how may people are drinking arsenic contaminated water above 0.05 µg/l. Further, if we strictly obey this permissible limit, then one should not drink water containing arsenic above 0.05 µg/l.
The Field-Kits we are so far using are based on semi-quantitative concept (MERCK Field Kit for arsenic, Germany also writes on its Field Kit,"result is, semi-quantitative"). On the basis of this semi-quantitative concept of Field Kits can we say after measuring a water sample for arsenic that its concentration is less than 0.05 µg/l of arsenic or more than 0.05 µg/l of arsenic when we say 50 µg/l is our cut-off point, i.e., can we say with certainty that the water is safe drink or not safe to drink? Thus we need to add with 50 µg/l a factor ±X. But what will be the value of this factor X ? This X is to be obtained from the Standard Deviation of the results of those who are measuring arsenic with the help of Field Kits in the fields, and the value can be calculated after analyzing a large number of samples very close to 0.05 µg/l.
Field Kit results and their effect on villagers
(a) Action Research Report: UNICEF/DPHE/BRAC Arsenic Testing of Newly Installed Tubewells; Quality Control on Field Kit Analysis; March, 1999 reports (Appendix: Data, page-9) in the area Brahamanbaria, Bangladesh. Field-Kit report shows arsenic to be less than 10 µg/l, when Arsenator reference method shows 180 µg/l. So the user will think the water to be safe, when he will actually be drinking poison.
(b) NEERI-WHO-ICP report (Assessment of Arsenic Field Testing Kits, Final Report, NEERI and WHO, June, 1998) shows six samples from Bangladesh and West Bengal contain arsenic between 98 µg/l and 170 µg/l when all five Field- Kits show less than 50 µg/l, and villagers will drink knowing the water to be safe. Will this not be a criminal offence on our part.
(c) Action Research Report: UNICEF/DPHE/BRAC Arsenic Testing of Newly Installed Tubewells; Quality Control on Field Kit Analysis; March, 1999 in its report (Appendix Data, page-9) reports that out of 12 samples measured for arsenic by Field-Kit showed arsenic between 50 - 280 µg/l, and when measured by Arsenetor, 7 samples (58%) were found safe to drink. The villagers were told not to drink that water and the tubewells were painted red. Can one imagine the metnatal stress of the villagers who were made to believe that they had been drinking contaminated water. Their next problem was to find another source of safe water when neighbours were not always co-operative.
Practical Difficulties in implementation of Field Kit project (experience gathered seeing the field workers working in field and their field results)
(a) We understand villagers who will
measure arsenic with Field Kits will be trained by experts. But the
comes is how skilled
people be? BRAC mentioned [Action Research Report: UNICEF/DPHE/BRAC Arsenic
Testing of Newly Installed Tubewells; Quality Control on Field Kit Analysis;
March, 1999]--- "BRAC researchers, with technical assistance from
UNICEF trained the 120 field staff members in field kit use. Field staff
were village health workers (all women), with limited education levels."
Did we select Field-Kit workers after they pass the efficiency test?
A suggested protocol to select Field workers is like this.
The field workers will be chosen after they pass the efficiency test. The efficiency of the field workers can be evaluated when each field worker, after proper training, will measure each 25 field samples on two concentrations close to the value below and above 0.05 µg/L and the result to be checked by standard reliable technique.
(b) There should not be any favoritism in appointing the Field Workers. However, we will first try to find the skilled Field-Kit workers from the arsenic affected villages.