Summary of presentation

Possible Arsenic-Contamination-Free Groundwater Source in Bangladesh

By Dipankar Chakraborti, 12 February 2001 at Dhaka Community Hospital

What I am presenting here is a summary of the above presentation. The original report is about 400 pages with more than 50 maps, 100 tables.

Background

School of Environmental Studies (SOES), Jadavpur University, Calcutta, India and Dhaka Community Hospital (DCH), Bangladesh are working on arsenic groundwater contamination in Bangladesh for about last 6 years. During June-July, 1999 we had finished 24000 (twenty-four thousand) water analyses for arsenic by FI-HG-AAS (our determination limit with 95% confidence is 3 m g/l) covering all 64 districts of Bangladesh and analyzed thousands of hair, nail, urine, skin scales from people living in arsenic affected villages and screened 25,000 people from the affected villages for arsenical skin lesions (15% of 25000 people screened have arsenical skin lesions). 

Estimated information of all these patients with nature and magnitude of skin lesions were registered. Hairs, nail, urine, skin-scale of about 35% of these patients were also analyzed. We tried to establish the co-relation between arsenic in hair, nail, urine and concentration of arsenic in drinking water. 

When skin-lesions will appear on body depends on many factors like 

(a) concentration of arsenic in drinking water 

(b) how long one is drinking the contaminated water 

(c) how much one is drinking contaminated water per day (in many families we have found those drinking too much water have arsenic skin lesions when those drinking less have no skin lesions) 

(d) nutrition status of the people drinking contaminated water also plays an important roles. 

We have hundreds of example showing that poor people suffering from malnutrition showing arsenical skin lesions but people getting better nutrition not showing any skin lesions drinking the same concentration (also close to same volume) of contaminated water. 

From our 13 years field survey screening more than 100,000 people from West Bengal and Bangladesh and having a list of 12000 registered arsenic patients with skin lesions, we can say that usually above 300 m g/l of arsenic in drinking water may show arsenical skin lesions (exceptions are always there). However, we have found a few patients with spotted melanosis drinking 90 m g/l (Kolsur village, Deganga Block, North 24-Parganas) of arsenic in drinking water in West Bengal and 80 m g/l in Samta village, Sharsha Police Station of Jessore District of Bangladesh. However these are exceptions. 

Children below 11 years normally don't show the skin lesions but we have registered a few hundred patients aged below 11 years from West Bengal, India and Bangladesh, when arsenic in drinking water is quite high around 700 m g/l and above. Children suffering from malnutrition are also suffering from arsenical skin lesions even with lower arsenic in drinking water (around 400 m g/l).

Groundwaters of Pleistocene Upland, Pleistocene Plain, Hill Tract areas of Bangladesh are mostly arsenic contamination free.

While evaluating our last five years water analysis report (n=24000) from all 64 districts of Bangladesh during middle of 1999 we noticed that in some parts Bangladesh, the contamination is minimum and in fact some parts are almost arsenic contamination free. Even we have noticed some portions within highly arsenic contaminated areas are also quite safe. 

To be sure about our findings we cross-checked samples from the same areas and facts and figures generated were almost same. While trying to find out the reason, we noticed that out of the four geo-morphological regions of Bangladesh [(A) Hill Tract (B) Flood Plain (C) Pleistocene Upland / Plain (Table Land) and (D) Deltaic Plain with Coastal region], Hill Tract and Pleistocene Upland and Pleistocene Plain are usually contamination free. 

Exceptions we have noticed in fringe area of Pleistocene Upland and Pleistocene Plain with Flood Plain; Hill Tract with Flood Plain etc. Also we have noticed that if river had eroded Pleistocene Upland / Pleistocene Plain or Hill Tract area some contamination are there (the reason may be Holocene deposition occurred in river eroded area). Please find herewith a few examples.

Example A: Dhaka District.  Out of six Police Stations (PS) of Dhaka District; 4 Police Stations-- Dhamrai, Savar, Dhaka City, Keraniganj are in Pleistocene Upland and all are arsenic contamination free but two Police Stations Nawabganj and Dohar are in Flood Plain area and these 2 Police Stations are highly contaminated.

Example B: Narayanganj District has 5 Police Stations-- Araihazar, Sonargaon, Bandar, Narayanganj Sadar and Rupganj and out of these 5 Police Stations only Rupganj Police Station is in Pleistocene Upland and is contamination free when the rest Police Stations are highly contaminated.

Example C: Gazipur district has 5 Police Stations -- Sreepur, Kaliakoir, Gazipur, Kaliganj are in Pleistocene Upland and all are contamination free while Kapasia is in Flood Plain and highly arsenic contaminated with arsenic patients.

Example D: Chittagong district is mainly in Hill Tract but a few Police Stations are partly in Hill Tract and Partly in Flood Plain and the areas in Flood Plain are arsenic contaminated while the Police Stations in Hill Tract are mostly safe. Sitakundu, Mirsharai, Anowara, Banskhali are few arsenic contaminated Police Stations in Flood Plain area of Chittagong district.

Example E: Nawabganj and Rajshahi districts are mainly in Flood Plain area but one police station of Nawabganj i.e., Nachole and two police stations of Rajshahi districts i.e., Godagari and Tanore are in Pleistocene Upland and both these three police stations are almost arsenic contamination free as we expected.

Arsenic in deep tube-wells

While looking about our results in deep tubewells above 100 m from all these 4 Geo-morphological regions we found all tubewells above 100 m in Hill Tract and Pleistocene Upland / Pleistocene Plain are arsenic contamination free. In case of Flood Plain and Deltaic Plain (including coastal region) we had noticed that deep tubewells (n=371) above 300 m are mostly (except 4) safe with respect to 50 m g/l but about 22% of tubewells contain arsenic between 10 and 50 m g/l.

On the basis of our findings up to middle of 1999 we went for a short communication and the paper was published at the end of 1999 [available online] Reference: Possible Arsenic Contamination Free Groundwater Source in Bangladesh. D. Chakraborti, B.K. Biswas, G.K. Basu, U.K. Chowdhury, T. Roy Chowdhury, D. Lodh, C.R. Chanda, B.K. Mandal, G. Samanta, A. K. Chakraborti, M.M. Rahaman, S.Roy, S. Kabir, B.Ahmed, R. Das, M. Salim and Q. Quamruzzaman, J. Surface Sci. Technol. Vol. 15, Nos. 3-4, 179-187, 1999.  Available online.

From July 1999 till January 2001 we further made a detailed study for all the 4 geomorphological regions and mainly in Pleistocene Upland and Pleistocene Plain and its surrounding areas. Altogether we further analyzed 10000 (ten thousand) water samples from all these 4 geo-morphological regions. After getting all the results of fresh 10000 samples we found it is almost the mirror image of what we found earlier. To confirm our findings we then tried to procure all the analytical results of other organizations working in Bangladesh on arsenic contamination like DPHE/BGS, NGO-Forum, BRAC, Grameen Bank, Gonosastya Kendra, CARE, etc. It appears from the comparative study that over all the findings of others are close to our findings.

Table-1 and Table-2 show the comparative study of SOES-DCH water analysis report with others on Pleistocene Upland and Pleistocene Plain and Hill Tract area.

Table-1 Comparative Study Of SOES-DCH & Other Organizations On Status Of Groundwater Arsenic Contamination In Pleistocene Upland & Plain Area

*Surveyed by CARE, Bangladesh; BDL = Below Detection Limit (Our determination limit is 3 m g/l with 95% confidence).

Table-2 Comparative Study Of SOES-DCH & Other Organizations On Status Of Groundwater Arsenic Contamination From Hill Tract Area

* Partly in Flood Plain and partly in Hill Tract. Flood Plain area is arsenic contaminated.

Arsenic contamination in Deltaic Plain (including Coastal region) and Flood Plain area

Deltaic Plain and Flood Plain region are the most arsenic contaminated area of Bangladesh. Although at present 70.5% of the tubewells show arsenic above 10 m g/l and about 55% of the samples above 50 m g/l but from our West Bengal experience we expect in long run more tubewells will become unsafe.

Deltaic Plain and Flood Plain region are the most arsenic contaminated area of Bangladesh. Although at present 70.5% of the tubewells show arsenic above 10 m g/l and about 55% of the samples above 50 m g/l but from our West Bengal experience we expect in long run more tubewells will become unsafe.

Status of arsenic contamination in 4 districts mostly in Flood Plain area in North, North-West part of Bangladesh lying between Pleistocene Upland and Pleistocene Plain

Table-3 shows arsenic concentration in shallow hand tubewells of Nilphamari, Lalmonirhat, Kurigram and Rangpur in NorthWest and northern part of Bangladesh. Out of total 28 Police Stations only Pirgachha of Rangpur is highly arsenic contaminated. From the analytical results of these 4 districts (Table-3) it appears that these 4 districts are almost safe except Pirgachha P.S. of Rangpur district. The reason is not known. We have an explanation. Although according to the geo-morphological map, most of these 4 districts are in Flood Plain but how truly they are in Flood Plain is a doubt! We suspect that these 4 Flood Plain districts between Pleistocene Upland and Pleistocene Plain where less Holocene deposition took place and sub-soil area is mostly in Pleistocene Upland & Pleistocene Plain.

Table-3 SOES-DCH Arsenic Contamination Report From 4 Districts In Northern Part Of Bangladesh Where Contamination Is Minimum

*Except Pirgachha Police Station which is highly contaminated

Conclusion

In Bangladesh Police Stations situated in Hill Tract, Pleistocene Upland, Pleistocene Plain are almost arsenic contamination free except the fringe area or where river erosion took place. Also some Flood Plain areas between Pleistocene Upland and Pleistocene Plain like Nilphamari, Kurigram, Rangpur, Lalmonirhat are almost contamination free.

12% of the deep-tubewells analyzed between 100 and 300 meter from Flood Plain and Deltaic regions including Coastal are arsenic contaminated above 50 m g/l. But deep tubewells above 300 meter are mostly safe with respect to arsenic above 50 m g/l but 22% of these deep tubewells above 300 meter contain arsenic between 10 and 50 m g/l.

Key Words

Hill Tract; Pleistocene Upland; Pleistocene Plain; Deltaic Plain (including Coastal); Flood Plain; Barind, Madhupur; Lalmai Hills; Dupitila; arsenic concentration above 50 m g/l in deep tubewells between 100 and 300 meters; arsenic concentration between 10 and 50 m g/l.

• Magnitude of arsenic contamination in 47 districts of Bangladesh with 22003 hand-tubewells analyses

• Analyses of large no. of hair, nail, urine, skin-scales from arsenic affected area (both patient and non-patient)

• Dermatological details of about 4000 registered patients.

• Number of hand-tubewells in Bangladesh.

• People drinking arsenic contaminated water >10, >50, >300 m g/l.

Read the Ph.D. Thesis "GROUNDWATER ARSENIC CONTAMINATION IN BANGLADESH"

December 2000, Bhajan Kumar Biswas, School of Environmental Studies, Jadavpur University, Calcutta - 700 032, India.  

You can purchase the Ph.D. thesis by paying US $ 100