Environmental Health Catastrophe in Eastern India: A Case Study of Arsenic Morbidity in West Bengal
M Guha, A Chattopadhyay, D Nagdeve
Citation
M Guha, A Chattopadhyay, D Nagdeve. Environmental Health Catastrophe in Eastern India: A Case Study of Arsenic Morbidity in West Bengal. The Internet Journal of Third World Medicine. 2005 Volume 3 Number 2.
Abstract
An environmental health catastrophe is slowly unfolding in West Bengal where millions of people drink groundwater with arsenic concentration above the permissible limit as recommended by the World Health Organization (WHO). A cross-sectional case control study was conducted in one of the worst hit districts of West Bengal. This paper reports the epidemiological and social context of the crisis based on the survey of sample population in six villages. Morbidity from skin lesions due to chronic arsenic toxicity has been found in almost one-third of the study population aged more than 15 years. The study shows a higher prevalence of arsenic skin lesions among males, with clear dose-response relationship. There was a significant association of the diseases with the exposure levels and to the dose index (p<0.05), regardless of sex. The overall high prevalence rate in the "case" villages underlines an alarming sign of arsenic exposure. With higher doses and lower body weight, even children with lower exposure are susceptible to the arsenic-specific morbidity. Individuals with some symptoms of arsenicosis have an enhanced susceptibility of developing respiratory problems, general weakness, stomach ailments and burning sensation in the affected areas. The gravity of the situation calls for immediate provision of safer source of drinking water, which is the best preventive measure of arsenic morbidity and mortality.
Introduction
Healthy living depends upon successful and optimal exploitation of natural resources. An imbalance in the equilibrium manifests itself in the form of environmental hazards. Arsenic contamination of groundwater is one such impending hazard, which is a serious public health problem in most countries with detectable limits of arsenic concentration. The arsenic contamination of groundwater in the Lower Ganga Plain of West Bengal in India was first identified in July 1983. Presently, Bangladesh and India are grappling with the largest mass poisoning of a population in history and the estimation predicts that out of 125 million inhabitants, about 35 to 77 million are at the risk of drinking arsenic contaminated water (Khan et al. 1997; Dhar et al. 1998). The scale of this environmental disaster is even greater than what have been before; it is beyond the accidents at Bhopal, India, in 1984, and Chernobyl, Ukraine, in 1986. Although the arsenic contamination problem in West Bengal reached public concern almost 20 years ago, there are few concrete plans and much less achievements to solve this problem. The villagers are usually more severely affected than they were 20 years ago. Even now, many who are drinking arsenic contaminated water are not aware of this fact and its consequences.
Sources of arsenic in West Bengal
Bagla and Kaiser, 1996 and Bhattacharya et al., 1997 propounded two principal hypotheses on the origin of arsenic in groundwater with support from the UK- based British Geological Survey (BGS),
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Natural Sources: the arsenic derived from the ferric hydroxide minerals present in the aquifer sediments.
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Anthropogenic Sources: the arsenic derived from the oxidation of arsenic-rich pyrite in the shallow aquifers as a result of lowering of the water table due to over extraction of groundwater for irrigation.
Most of the arsenic affected areas of West Bengal lie in the alluvial plains formed during the Quarternary period (last 1.6 million years). The broad alluvial plains of the Ganga and the Brahmaputra rivers in the Garo-Rajmahal Gap - called the Himalayan Fore deep - extend to the northwest and northeast, respectively. To the north of this line are the crystalline rocks and meta-sediments of the great Himalayan thrust blocks. West Bengal (Purulia district), Bihar and the Shillong Plateau (north of Sylhet and Mymensingh districts of Bangladesh) are the extensive areas of Pre-Cambrian era (last 570 million years) having metamorphic rocks and granites with widespread sulphide mineralization. Because of their position in this arsenic-prone area, close to where the river Ganga enters Bangladesh (geologically speaking), British Geological Survey (BGS) suggested that they might be the primary source of arsenic in the Bengal alluvium.
Need for the study
In West Bengal, arsenical toxicity was practically unknown up to 1978. But of late, the appearance of this disease - Arsenical Dermatitis (ASD) or arsenicosis or arsenical toxicity - is rampant in villages having drinking water contaminated with arsenic. In 1983, K. C. Saha, Department of Dermatology, School of Tropical Medicine in Kolkata, identified the first case of arsenic-induced skin lesions. After ruling out other causes, water sources used by the patients were analyzed, and the diagnosis of arsenic-caused diseases was confirmed. Even after 22 years of the first confirmation, it is contended that not only thousands of present sufferers but countless future generations are still gravely at a risk from groundwater contamination in Bengal. The present situation of West Bengal is that a total of 2600 villages in 75 blocks of nine districts (
This study focuses in detail, on the clinical stage (symptomatic or overt stage) of arsenicosis with specification of each symptom as described by Yeh, 1973. The aim of this research is to measure the prevalence rate of skin lesions associated with arsenic exposure. A graded mean score of skin symptoms was used to measure the intensity of the problem. For the suspected and probable cases of arsenicosis, the general health problems and the perceived arsenic related morbidity pattern have been studied 1 .
The study area
A cross-sectional case-control study was conducted in Malda district, one of the worst arsenic affected districts of West Bengal . This district is a low-lying plain with the land sloping towards the south. The soil of the area is alluvial formed by the rivers of Ganga, Kalindi, Tangan, Punarbhaba and Mahananda. The economy is purely rural in character as majority of the workers depend on primary activities as their principal source of livelihood.
Of the total fifteen blocks, five blocks namely
Sampling design and sample size
Among the five affected blocks of Malda, two blocks, namely, Kaliachak-I and Kaliachak-II were selected purposively for the present study. From the two selected blocks, six villages, two each from high, medium and low category were chosen according to the ranking given by the Public Health and Engineering Directorate (PHED) to the villages by arsenic concentration levels in the tube wells. In all three villages, one each from high, medium and low category have been selected from Kaliachak-I and II respectively. The level of arsenic concentration and the related information of different villages selected for the study purpose are given in table 1.
Figure 1
The criterion for dividing the villages into
Methodology
The disease prevalence rate of arsenic- specific skin lesions have been calculated both for case and control villages by the varying arsenic levels in the groundwater of the studied villages. The respondents were stratified by sex and six age categories. All the prevalence rates were directly standardized considering the age distribution of the study population as standard.
The individual exposure to chronic arsenic toxicity has been assessed in terms of levels of arsenic contaminated water or by daily dose per body weight (µg/L-kg/day). This has been described with the help of the dose index (Tondel et al. 1999), which is the present arsenic level in water (consumed by the individual) divided by individual body weight expressed in micrograms per liter per kilogram (µg/L-kg), which may crudely account for the arsenic intake in relation to body size. The arsenic concentration in the drinking water in micrograms per liter was taken as the current exposure level. Keeping in view the higher levels of arsenic in the case villages the cut off points for the dose index has been specified as 1 for ≤3µg/L-kg, 2 for 3.01-6µg/L-kg and 3 for >6µg/ L-kg.
Assuming that the early manifestations of arsenic poisoning are more frequent than the advanced cases, a score was assigned to each of the symptoms in order of increasing severity and decreasing prevalence as specified by Yeh (1973). Appendix -I gives the score values assigned to each symptom in accordance with their occurrence in different parts of the body. Thus, the most common and earliest manifestation has a score of 1 and the rare symptom as 5.5. Keratosis being a much-advanced dermatological symptom, a person having keratosis has been considered positive for all the other earlier symptoms of melanosis. Hence, in that case, the overall score for each individual has been derived by adding up the scores of all the earlier symptoms. Lastly, a mean score has been calculated (range 1-35.25) to assess the severity of the problem for all the suspected and probable cases of arsenical dermatitis.
Findings
Prevalence rate by case and control villages
The age-adjusted disease prevalence rate of arsenic-specific skin lesions was found to be 17 percent for females and 41 percent for males in the villages of
Figure 2
Figure 3
Among males, the prevalence is as high as 78 percent compared to 55 percent for females in the 48+ age group in the villages of
Individual exposure assessment
An apparent dose-response relationship was found, independent of all background characteristics, in case of any kind of skin lesions (table 3). The dose-response relationship reveals that higher concentration of arsenic in drinking water is associated with the higher risk of the disease prevalence even among children. About 86 percent children in the age group 0-14 have a dose index >6µg/L-kg which reveals the fact that dermal manifestations are observable even at lower exposure but higher doses. For the dose index value of 2, the percent distribution of males and females are 40 and 42 percent respectively. This higher percentage in case of females can be attributed to low body mass index (BMI) and low nutritional level, which intensifies the susceptibility factors leading to detectable disease.
Figure 4
The duration of stay has a strong association with dose-index in the sense that lower the duration of stay, higher is the dose index and vice versa. About 59 percent of the cases fall in the third category of the dose index with duration of stay less than 15 years. With duration of more than 15 years, the percentage is as high as 40 percent even in dose index 1. Compared to the case villages, the control villages do not show a higher dose index as arsenic level in the water is below the permissible limit of 0.05mg/L and all the suspected cases with skin symptoms have a residence history of more than 15 years in the same locality.
Symptoms of arsenic morbidity
The mean score, explaining the intensity of the problem in view of higher arsenic concentration for the case villages is found higher by 8 percent than the control villages (table 4). Children in the case villages have a high mean score of 7.4 as compared to zero in the control villages. A sex-differential is apparent in the mean score of males and females with 13.9 and 10.7 respectively in the case villages. Respondents with duration of stay in the present area for less than 15 years have a lower mean score of 8.0 as compared to those having higher duration. All the suspected cases (12) even in the control villages show some skin symptom in case of longer duration of stay (more than 15 years). This reveals that longer duration and higher concentration account for increased severity of arsenic-related disease incidence. The correlation coefficient of score and concentration of arsenic in the tube well water has come out to be positive and significant.
Figure 5
Perceived health problems
The symptoms of acute poisoning through oral consumption of arsenic contaminated water are often manifested through minor ailments like headache, drowsiness, confusion, convulsion, decrease in sensitivity to touch, pain, and temperature sensation, weakness of grip and wrist drop (Col et al. 1999). Among the suspected and probable cases in the study population, the most frequent health complaints (faced during the past three months) are- tingling and numbness of hands and feet, reported by 84.9 percent, followed by 78.3 percent with general weakness and fatigue (table 5). Weakness is a highly subjective symptom, which has previously been reported, in arsenic-exposed patients (Guha Mazumdar et al. 1997). The other symptoms included frequent high fever with cold and cough (48.7 percent), indigestion problem (46.7), muscular and joint pain, eye and urine problem. The respondents have rarely been found to take medicine for any of these ailments, in spite of facing difficulties in daily activities.
Figure 6
Disease history
The disease history of the affected individuals for the past six months shows that the most common diseases other than skin lesions have been dysentery, jaundice, malaria, liver disease, etc (table 6). The ingestion of inorganic arsenic in drinking water may be a contributory factor for other co-morbidity symptoms like pulmonary effects - 7 percent having complaints of chronic bronchitis; digestive system disorders, with 22 percent reporting dysentery, 7 percent diagnosed with ulcer and 14 and 7 percent suffering from jaundice and liver diseases respectively among the affected population. Although numbers were small, there was evidence of cancer (3 percent) among the suspected cases.
Figure 7
Discussion
This study is an effort to investigate the health effects (in the form of skin lesions) of arsenic contaminated drinking water. For this purpose a detailed case-control study was carried out to assess the dose-response relationship of arsenic in drinking water and skin lesions. These dermatological manifestations pose an important public health problem because advanced forms of keratoses are painful and changes in pigmentation can lead to social isolation in the villages. In contrast to cancers that take decades to develop, the latency for the dermatological effects is shorter, depending on the levels of past exposure. Thus, arsenic-induced skin lesions are early biomarkers of long-term exposure since they may appear after shorter periods. They might also be indicators for more serious long-term incidence of cancers of the skin and other internal organs.
The overall prevalence of cutaneous manifestations was 7 per 100 females and 23 per 100 in males. Men had higher prevalence of dermal lesions in all exposure categories, which indicate that males are more susceptible to get the disease. But the prevalence rate shows an increasing trend for both the sexes in accordance with progressive higher levels of arsenic and increasing age. The age-adjusted prevalence of skin lesions is strongly related to arsenic concentrations in water, rising from zero in the lowest exposure category (≤0.05 mg/L) to 16 per 100 for females consuming water containing >0.26001 mg/L. In males, the age-adjusted prevalence of skin lesions increased from 7 per 100 in the lowest level to 44.3 per 100 in the highest category. Surprisingly, a number of individuals with skin lesions were found to be consuming lower levels of arsenic (≤0.05 mg/L). This is particularly evident in the control villages, where 7 per 100 males are affected while for females the figure is zero.
Morbidity from skin lesions due to chronic arsenic toxicity has been found in almost one-third of the study population aged more than 15 years. This points to a strong dose-response while using dose index instead of only arsenic levels to assess exposure. Therefore, it may be assumed that arsenic levels in relation to body weight reflect more accurately the dose of arsenic obtained by the individual rather than just the water concentration. There also exist sex differences in dose-response relationship with varying exposure that may be accounted for by three factors. First, the cumulative exposure is much higher in males who were born in these villages, than in females who might have migrated from less contaminated areas after marriage. The other two confounding factors are sunlight exposure (Memon et al. 2000) and primarily masculine habits like smoking bidi or cigarette and chewing of tobacco that may account for the observed differences. However, the intensity of arsenicosis is more among females and children rather than males, which may be a function of individual immunity, nutritional status and higher dose index as supported by Smith et al. 2000.
The dose-response relationship for arsenic has been controversial (Haque 2000), but the present study made an attempt to assess the participant's current drinking water sources, which helped examine the relationship using a more refined exposure assessment. There is a significant positive relationship between duration of stay (considered here as exposure period) and individual dose index. The individual exposure assessment suggests that as arsenic levels were higher in the case villages, the highest dose index was stipulated at >6µg/L-kg. With higher doses and lower body weight, even children with lower exposure are susceptible to the arsenic-specific morbidity. The age factor plays a dominant role and the disease prevalence has been found to be higher among adults (both males and females) than in children. Based on limited exposure assessment, some cases appear to be occurring at surprisingly low levels of exposure. The mean score for arsenic-induced skin lesions was found to be higher by 8 percent in the case villages compared to the control villages. In addition, individuals with some symptoms of arsenicosis have an enhanced susceptibility of developing respiratory problems, general weakness, stomach ailments and burning sensation in the affected areas.
Conclusion
Based on the present study it can be concluded that clear evidence of dermatological manifestations in population exposed to arsenic through drinking water sources have been established by carrying out a case-control study. The prevalence, if not the severity, of skin lesions among the rural populace may be as high as in the various populations observed in the world where the use of arsenic contaminated drinking water commenced in recent years. We emphasize that the discontinuation of drinking arsenic contaminated groundwater and switching over to ‘safe' sources of drinking water remain of primary importance in managing patients with skin lesions. What we need at this moment to combat the situation is an alternative source of water other than underground water. There is an urgent need for a technical solution on how to provide ‘good quality' drinking water to such a large population. A proper watershed management can go a long way to provide a practical solution for this crisis. In addition, stringent laws are needed in developing countries like India, so that the environmental pollution will not lead to contamination of the groundwater. State health administrators should also undertake the regular testing of water that is used for drinking in order to check the levels of toxic metals. There is greater need for continuous monitoring of arsenic content in water as it varies with time and space. Even the safe tube wells should be tested for arsenic in every 3-6 months, to avoid ignorance about the subsequent contamination. Only the deep aquifer should be tapped for drinking water supply. The water in the new tube wells should be tested for arsenic prior to commissioning. The government should take initiative in providing large-scale arsenic removal plants and also developing cheap domestic filters to be fitted in hand pumps with safe sludge disposal arrangements. A proper assessment of the actual magnitude of the arsenic problem in all these villages is urgently needed through detailed epidemiological, clinical and therapeutic studies. The arsenic calamity of West Bengal, the second largest in the world, should be dealt with immediate effect. The world should learn a lesson from this instance that any country where water extraction from underground sources goes similarly unchecked could be leaving them open to a similar calamity.
Notes
Melanosis i.e., dark pigmentation – diffuse or spotted with keratosis i.e., dry, rough spotted nodules on palms and soles are the chief symptomatology of arsenical dermatitis (ASD). There are various causes of melanosis, keratosis, spotted and diffused, genetic or acquired. The combination of pigmentation (melanosis) and nodular rough skin (spotted palmo-plantar keratosis) in the same patient points to chronic arsenic toxicity and the diagnosis of arsenical dermatitis (ASD), excluding hundreds of causes of isolated pigmentation and nodular rough skin. Genetic disorders are often present since childhood and acquired diseases like arsenicosis often appear in later life.
Diffused darkening of skin starts in the palm, trunk and gradually spreads to the whole body. This is the earliest symptom and a comparison with the normal palm reveals mild melanosis. It is not necessary that people suffering from arsenic toxicity will have symptom of diffuse melanosis.
It is also an early symptom and arsenic patients normally show spotted melanosis on chest, back and sometimes on the limbs, i.e., hands and legs.
Arsenic patients having spotted melanosis develop pigmented and depigmented spots on legs or trunk. Leucomelanosis, which are black and white spots, side by side, is also seen in many patients. Probably, stimulation of melanocyte produces pigmentation and damage in later stage is responsible for depigmented spots. Leucomelanosis is common in persons who have stopped drinking arsenic contaminated water but had spotted melanosis earlier.
Keratosis is the middle stage of arsenicosis. The skin, in portions becomes hard and fibrous; it is as if the body has broken out into hard boils, or ulcers (Cuzick, et.al., 1992). Diffuse or nodular keratosis on the palm of the hand or sole of the foot is a sign of moderately severe toxicity. Rough and dry skin, often with palpable nodules in dorsum of hands, feet and legs means severe toxicity. This can lead to formation of gangrene and cancer (Sommers and McManus, 1953).
After 5 to 10 years of spotted melanosis, palmo-plantar skin (Cuzick, et.al., 1984) shows spotted keratosis (may be early depending on concentration of arsenic in contaminated water, amount consumed and nutritional status). Still later (after 10 years) skin becomes dry and thickened leading to diffused keratosis, mainly on palms and soles. Gradually, thickening of soles can give rise to cracks and fissures – hyperkeratosis. If the concentration of arsenic in tube well water is high or the disease is of long duration, more than 10-15 years, keratosis also develops in the dorsal skin of hands, feet, legs (dorsal keratosis) or even other parts of the body or the skin (whole body keratosis).
Acknowledgement
The authors express their deepest sense of gratitude to Dr. Devdutta Chatterjee, Medical Officer, Arsenic Clinic, SSKM Hospital, Kolkata, who assisted them during the preparation of interview schedule and the process of data collection. His help, guidance and practical insights in this field have been of immense help to prepare the manuscript and revise it subsequently. The successful completion of the work would not have been possible without the help from each and every staff member of the School of Environmental Studies (SOES), Jadavpur University, Kolkata, who helped me by providing details of projects reports, maps and photographs. My sincere thanks and respects to Dr. Dipankar Chakraborti, Director of SOES, Jadavpur University, and the beacon in the field of research relating to arsenic crisis in the state of West Bengal and Bangladesh.
Appendix
Scores of different arsenic-induced dermatological manifestations
Figure 8
Abbreviations
DMP - Diffuse Melanosis on Palm.
DMT - Diffuse Melanosis on Trunk.
SMP - Spotted Melanosis on Palm.
SMT - Spotted Melanosis on Trunk.
LEU - Leuco-melanosis.
WBM - Whole Body Melanosis.
DKP - Diffuse Keratosis on Palm.
DKS - Diffuse Keratosis on Sole.
SKP - Spotted Keratosis on Palm.
SKS - Spotted Keratosis on Sole.
DK- Dorsal Keratosis.