West Bengal || Bangladesh
Middle Ganga Plain, Bihar ||
27 days detailed field survey information from April 1999 to February, 2000
What percent of actual arsenic patients in affected villages we could really examine
After discussing with villagers, we feel we could examine only a small percentage (10-15%) of the total population in affected villages who have arsenical skin lesions. The reasons:
(a) In villages, the affected people think their disease is contagious and if other people get to know about their ailment they will be isolated; (b) young girls and women of conservative families do not want to be examined (Photograph-6 & 7); (c) people are frustrated and feel that there is no cure of the disease; (d) Since village roads are not good, people who are suffering seriously did not want to come to our camp travelling a long distance due to weakness; (e) normally, we were in a village during the day and at that time of the day most of the males were working in the field.
After an extensive field survey for 27 days we feel that we have got information of more villages where people have arsenical skin lesions. After 27 days field visits we have now information of 73 villages from 47 districts and also we have information of arsenic patient from 3 districts Chittagong, Manikganj and Narail.
We have evidences now from W. Bengal, India that more and more tubewells which were once safe to drink are getting arsenic contaminated.
Finally a detailed survey is necessary
to know the actual number of people drinking arsenic contaminated water
above 0.05 µg/l and people suffering from arsenical skin lesions.
We have the analytical information of arsenic from 15969 hand tube-wells with depth (from 6.4 m onwards up to depth 400 m) from 47 districts of Bangladesh where groundwater has arsenic above 0.05 µg/l. Our overall study shows arsenic concentration increases at the beginning with depth up to about 15-20 meters and then decreases with depth. The same trend we had observed in all 47 districts in Bangladesh where we have arsenic in groundwater above 0.05 µg/l. Figure-4 shows the arsenic concentration with depth from 47 districts in Bangladesh for 15969 hand tubewells.
The number of people in Bangladesh drinking water contaminated with arsenic of above 0.01 µg/l, the WHO guide line value and above 0.05 µg/l, the maximum permissible limit in drinking water of Bangladesh is a cause of concern. A report published in January, 1999 by British Geological Survey jointly with Department of Public Health Engineering (DPHE), Bangladesh, states,"assuming a large uncertainty of ± 10%, the exposed population would lie in the range 18.5- 22.7 million (Groundwater Studies For Arsenic Contamination of Bangladesh, Final Report, British Geological Survey, Mott MacDonald Ltd (UK), January 1999, page-6-2). Although, time to time, predictions on number of people exposed are made on the higher side but the scientific basis of the report is not available (Pratham Allo, Dec 20,1999;Dhaka, Bangladesh).
During our study for last 5 years in Bangladesh we had analysed 22003 tube-well water samples for arsenic by FI-HG-AAS from 64 districts of Bangladesh. In 54 districts we observed arsenic in groundwater above 0.01 µg/l and in 47 districts above 0.05 µg/l. So far we have found only in 10 districts where groundwater is safe to drink with respect to arsenic according to WHO guide line value. However, this does not mean that those districts which are at present safe or where arsenic is present less than 0.05 µg/l will remain safe in future. Only 2 years before we knew and reported groundwater of Rangpur, Jamalpur, and Bogura were safe to drink but now in many villages of these three districts not only we have observed arsenic in groundwater above 0.05 µg/l but many people are suffering from arsenical skin lesions.
To get an idea about number of people drinking arsenic contaminated water above 0.01 µg/l and 0.05 µg/l in Bangladesh; we made a scientific approach for 43 districts in Bangladesh. We had already identified 47 districts in Bangladesh where groundwater has arsenic concentration above 0.05 µg/l. Now from our duly filled-in questionnaire during fieldwork we got necessary information on the number of user for each tube-well for 16410 tube-wells from 43 out of 47 districts where groundwater contains above 0.05 µg/l of arsenic. Based on the relevant information collected by us and result obtained by our FI-Hg-AAS techniques for arsenic, an approach was made to calculate the number of user consuming drinking water contaminated with arsenic of above 0.01 µg/l and above 0.05 µg/l for each police station. For a district the calculated value of each police station based on actual observations were used to give weightage (percent/100) on the other police stations considering their relative location for which sampling were not done. Ultimately we calculated first the total number of peoples effected from 10 districts. Based on the values of these 10 districts, remaining 33 districts were calculated. Finally adding all these calculated values, we made the prediction of number of people exposed to more than 0.01 and 0.05 µg/l in 43 districts. We did not extrapolate our result to all 47/54 districts, as we do not have the available number of users in those districts.
Mode of Calculation
The following criteria we considered for our estimation:
(a) Ten districts we considered in the order, 3 from east (Lakshmipur, Noakhali, and Chandpur), 3 from the west (Jessore, Meherpur, and Kustia), 3 from south (Barisal, Khulna, and Faridpur) and one from northwest (Pabna). In these ten districts also we had adequate number of samples. The above selection was done at random with emphasis on covering the total area of 43 districts.
(b) We considered those districts where we have at least more than 100 samples from each police station and of 4 police stations from each district (Meherpur has only two police stations).
(c) The percentage was used as weight on number of population. Then distance of the location and number of people exposed to arsenic contaminated water were taken as criteria for calculating the total number of peoples exposed in districts.
The approach adopted for calculations is explained below taking Lakshmipur district as an example (Figure-5) and on the basis of our field study report of the same district (Table-11).
Lakshmipur has altogether 4 police stations (Ramganj, Raipur, Lakshmipur Sadar and Ramgati) and out of them, three police stations in northern side cover an area of 61 percent of the districts. Average population of these three police stations drinking arsenic contaminated water above 0.01 µg/l are 95.8%, 88.8% and 89.9% and above 0.05 µg/l are 84%, 80.9%, 82% respectively. The number of people in these 3 police stations is 601000, 245000 and 314880 respectively. The number of people exposed to arsenic with respect to number of tube-well samples in these three police station are 2215, 43839, 8299 above 0.01 µg/l and 1945, 39957, 7569 above 0.05 µg/l. The police station in the remaining area in Ramgati ; the population exposed to Ramgati are 3095 above 0.01 µg/l and 2747 above 0.05 µg/l. The number of people exposed will be the total population of each police station multiplied by weight. The number of people exposed in these four PS at two levels (>.01 & >.05 µg/L) are shown in Table 11. Therefore the total number people exposed in this district are 1350884 above 0.01 µg/l and 1286725 above 0.05 µg/l out of total 1504000. Percentage variation among 3 northern police station in Lakshmipur is not significant. Location wise, from Lakshmipur Sadar police station to Ramgati police station, the percentage varies from 84 to 69% with a difference of 14.3. Therefore, in 34% areas variation will not be more than 14%. If we consider the weight of 0.7, the number of peoples exposed will never be less than 2688000. That is why we have taken number given above as the number of people exposed. All the figures are given in Table-12.
Table-11: Peoples exposed in Lakshmipur district above 0.01 µg/l and 0.05 µg/l.
In this way the people exposed in other 9 districts were calculated and given in Table-12
Table-12: People exposed in other 9 district above 0.01µg/l & 0.05 µg/l
These results were extrapolated in other 33 districts where we have relevant information/data on number of user and arsenic concentration in tube-wells and final result shows that the total populations exposed above 0.01 µg/l and 0.05 µg/l in 43 districts are 51590829 and 25045633 respectively out of total 85397000 people in 43 districts.
Our attempt for predicting the people exposed to arsenic from groundwater above 0.01 and 0.05 µg/l were initiated after we had analyzed 22003 hand tube-wells. The above prediction was made based on the number of samples already drawn, which may not be adequate for all the districts. Therefore, for validation of the prediction system and its refinement, further sampling would be done.
How many hand tube-wells are in 43 districts of Bangladesh?
Time to time predictions were made about the number of hand tube-wells in Bangladesh. The following information is available
1. Hussam et al in Env. Sci. Technol., ASAP article 10.1021/es 990146 S 0013-936 X (99) 00146-7, Web Release Date September 4, P 999 writes " WHO also reports that there are about 2.5 million tube-wells (wells with a metal casing) in Bangladesh and more than 95% of Bangladesh population of 120 million drinks well water.
2. British Geology and Department of Public Health, Dhaka, Bangladesh writes an another reports 4-5 million hand tube-wells are in Bangladesh (Ground water studies for arsenic contamination in Bangladesh, Final report, British Geology Survey Mott MacDonald Ltd, UK, January 1999).
3. M. A. Bhuyan Dept. of Water Resource Engg. BUTT- Bangladesh writes, on Groundwater: Bangladesh Perspective reported that according to a 1994 estimate (Wan, 1994), three were an estimated 2.4 million tube-wells in rural Bangladesh, of which about 900,000 were public tube-wells (Arsenic in Groundwater: Scratching for Alternatives to Rural Water Supply, P 15, March 22, 1999, Dhaka, Bangladesh NGO Forum for Drinking Water Supply & sanitation).
To know the approximate number
of tube-wells in 43 districts of Bangladesh ,we made a simple calculation
from our available data of field survey questionnaire. We know that 393845
people use 16410 hand tube-wells. Thus 24 people are using one tube-well.
We know the total population of these 43 districts of Bangladesh is 85397000.
So number of tube-wells in these 43 districts are 3596333(3.6 Million).