West Bengal || Bangladesh
Middle Ganga Plain, Bihar ||
27 days detailed field survey information from April 1999 to February, 2000
In many villages while working in the field we had found tubewells were coloured 'Red' and 'Green' after testing by field kits. Red indicates unsuitable to drink where arsenic concentration is above 0.05 µg/l and Green suitable to drink where arsenic concentration is less than 0.05 µg/l. While working in field we collected time to time samples from tubewells coloured red/green and found after analyzing by FI-HG-AAS technique that some of them were not rightly coloured. SOES with NGO Forum Bangladesh jointly conducted a study to evaluate the efficiency of the field kits (GPL, NIPSOM, and MERCK) which are widely used in Bangladesh. After comparing 3 field kits with hundreds of synthetic and field samples we came to following inferences.
1. These kits are not suitable to
measure the arsenic level below 0.08 µg/l with certainty.
To justify our findings SOES jointly with DCH Bangladesh went to field and collected water samples from 2866 tubewells colored red/green after testing with field-kit. Out of them, 1143 samples were marked green and remaining 1723 were marked red. We analysed samples from the same source for arsenic by FI-HG-AAS in laboratory to cross check the status of the tube-wells in terms of green and red. We had standardized our FI-HG-AAS system from inters laboratory comparison as well using Standard Reference Material. We can determine arsenic up to 0.002 µg/l with 95% confidence level. According to the results obtained by FI-HG-AAS out of 1143 tubewells colored green by field kits, 1058 tubewells were found green and 84 tubewells red. Thus it appears that 91.8% of the tube-wells were correctly identified safe to drink by field kit method. Out of 1723 tubewells colored red by field kits, 849 were found red and the remaining 874 were green by our FI-HG-AAS system. Thus it appears that Field-Kit could correctly identify 49.3% tube-wells. Therefore it may be mentioned that field kit could not detect the actual status of 874 + 84 =958 tubewells. Most surprisingly out of 958 tubewells (false declaration), 843 tubewell were safe according to the results obtained by FI-HG-AAS. Where scarcity of uncontaminated water already prevails, declaration of tubewells, which were really safe as unsafe, would not only aggravate the problem of having drinking water but also causes mental agony. Simultaneously, it has a tremendous impact on socio-economic condition.
The analytical result obtain
by FI-HG-AAS system for 2866 samples were compared with the status (green
or red) of tubewells made by field kits at different concentration ranging
from less than 0.003 to greater than 0.6 µg/l. The results shown in Table-10
revealed that 1920 tubewells were safe according to FI-HG-AAS, but the
kit indicated 1058 tube-wells were safe and the remaining 862 are unsafe.
Therefore, in the lower level, 44.9% false detection was made. Also in
this level, false detection was varying from 17.9% to 80.9%. The high
percentage of violation was observed in 0.03 to 0.039 ppm and in 0.04-0.049
ppm. The possible reasons may be the semiquantative nature of the kits.
Whereas in higher level, starting from the range of 0.05-0.06 µg/l to
ppm to >0.6 µg/l false detection were significantly reduced from 15.79%
to 4.17% in decreasing order except in one range of 0.06-0.07 µg/l. Therefore
it appears field-kit may not be suitable to measure arsenic concentration
to lower level. From our FI-HG-AAS we noted 665 samples below 0.003µg/l
where field kit indicated more than 0.05 µg/l 398 thus 59.8% false detection.
It appears 59.85% false detection of arsenic concentration level <0.003
µg/l is not realistic. It is also not consistent with our earlier observation
(SOES-NGO Forum field-kits study) with trained field workers where we
observed better performance of field kits at level <0.01 µg/l. But
results of our analyses for 2866 field samples by FI-HG-AAS showed unreliability
of field kit even at arsenic concentration level <0.003 µg/l. We feel
field workers operating field kits may be responsible for such anomaly.
The information /data we gathered during our field survey is narrated
(a) Field-kit users were mainly non-technical persons. They feel themselves important persons when they are in field as large crowd surrounds them and they eagerly wait for the comment of field workers on their tubewell contamination and skin lesions. Even we know the case (Abdul Mannan, Farakpur, Bheramara - 7040, Kustia Sadar) where one field worker tried to convince the engineer that his small moles on body are arsenical skin lesions.
(b) When field-kit workers get one after another tube-wells in some areas safe (below <0.05 µg/l) after testing, they are not happy to have the entire tube-wells safe. Consequently they decide to color at least few tube-wells red (this information we had received from a field co-ordinator).
(c) Quality of work gets diluted when an organisation makes a sub-contract of his contract.
(d) A page from our field diary as shown below will further explain it:
We heard from the villagers
a strange incident related to field testing and colouring of the tubewells
in this village. A group of field workers after testing with their field
testing-kits made a large number of tubewells red in this village. A next
group came later for testing and after their testing they made some of
the red tubewells green. A villager then approached to the field workers
and requested them to test the water of two hand tubewells. After testing.
it was said that one tubewell is green and another red. The villagers
then assaulted the field workers. The reason, the villager collected 2
glasses of water from same tubewell that field workers had coloured green
only some time before.