Health and sociocultural aspects of water use

EFFECT OF CHRONIC INGESTION OF ARSENIC-CONTAMINATED WATER IN RURAL COMMUNITIES OF BANGLADESH

UT-Group, Principal Investigators: Prof. Ryutaro OHTSUKA (Representative), Prof. Kazuo YAMAMOTO, Dr. Chiho WATANABE, Dr. Tsukasa INAOKA

BACKGROUND

In Bangladesh, people used to use surface waters for their daily consumption up to the 1970's. Due to the extremely high population density and the resulting bacteriological contamination of the surface water, they were forced to give up surface water and construct tubewells for pumping groundwater. This program was guided by the international organizations such as UNICEF and World Bank.

Although the shift to groundwater has reduced the incidence of gastrointestinal infections, it was realized twenty years later that this cannot be the final, perfect solution for providing safe water for everyone in this country. Another problem which threatened people's life began to emerge: the groundwater is contaminated by naturally-occurring arsenic.

In 1993, National Institute of Preventive and Social Medicine (NIPSOM), a Bangladesh governmental institution, reported the first diagnosed case of arsenicosis in the northwestern part of Bangladesh. Since then, many governmental and international groups and NGOs have become very active in addressing this problem. However, reliable quantitative information about the scale of the arsenic contamination has been rather limited until recently.

OUR OBJECTIVES

The long-term overall goal of this project is to establish scientifically reliable and socioeconomically feasible guidelines for water use patterns in arsenic polluted areas. It is important to satisfy the criteria of environmental sustainability and to meet the people's demands for higher living standards and quality of life, defined by minimized prevalence of arsenic pollution and drinking water-derived infectious diseases and by maximized agricultural productivity. Since there are many regions and countries where the groundwater which people rely on is contaminated by naturally-derived arsenic, such guidelines are expected to be important not only in Bangladesh, but also in many other countries, for example in Viet Nam, China Mongolia, Mexico, Chile, and Argentina.

To achieve this goal, scientists from different fields/disciplines are collaborating in this project. The UT group has been working on THE HEALTH AND SOCIOCULTURAL ASPECTS, the EAWAG/ETH group on household-scale removal of arsenic from tubewell water, and the MIT group on the geochemical aspects of arsenic contamination. We expect that the basic frameworks for solving and/or mitigation arsenic poisoning in local ecosystems will be clarified through the integration of these studies.

THE HEALTH AND SOCIOCULTURAL ASPECTS

The primary purpose of the work of UT GROUP is to describe the human toxicological and public health aspects at the community level. Information regarding the prevalence and the possible risk population is to be incorporated in designing and planning mitigation or counteracting measures. Our team has so far conducted several field surveys in two rural communities of Northwestern Bangladesh.

These are typical rice-farming communities where cases of arsenicosis has been found and registered by the local health officers. Each community consists of 150-200 households, meaures less than 1 square kilometer, and is located within 5 km from each other.

SUBJECT AREA AND THE FINDINGS

The Two communities have approximately 100 tubewells in total, which are used for drinking, cooking, washing, and bathing . The arsenic concentration of these tubewells varies considerably, ranging from less than 0.001 to more than 0.5 mg/L. Part of this variation was related to the depth of the tubewells (median ~ 80 ft), but not to the age of the tubewells (median ~ 6rs). Approximately 30% of these tubewells have arsenic concentrations exceeding 0.05 mg/L, which is the current regulatory upper limit for drinking water in Bangladesh (the WHO recommends a lower limit of 0.01 mg/L).

The ARSENIC IN SPOT URINE SAMPLES was found to be a good indicator for arsenic exposure. Pairs of samples obtained from the same group of individuals at three month intervals showed only small within-individual variations. Concentrations of the urinary arsenic and the tubewell arsenic showed a good correlation [Fig1], suggesting that a major source of the arsenic intake in these communities is the tubewell water.

We have examined and graded the DERMATOLOGICAL MANIFESTATIONS, including keratosis on the sole or palm and melanosis on the trunk, which are known sensitive response factors to chronic arsenic exposure and were presumably due to arsenic in this region. More than half of the adults (age > 20; n~450) exhibited at least one of these signs, and the prevalence was significantly higher in males than in females, even when the exposure levels were taken into account.

We found similar prevalence data among children (age 5-15; n~250), where no sex-related difference was apparent. In the males of one community, there was a distinct dose-response relationship, which was not obtained in the females [Fig 2]. In children, analyses of dose-response is under way. The cause of the sex-related difference in adults has not been elucidated and needs to be clarified not only to understand the toxic mechanism of arsenic but also to be implemented in the mitigation planning.

The NUTRITIONAL STATUS of the population may affect the manifestations of arsenic toxicity. Our anthropometry data indicated that there was no severe energy-protein malnutrition in this area, but there was a mild degree of deficiency in the major nutrients. Thus, we have evaluated the nutritional status of the people by a preliminary food survey. Basically, in terms of the major nutrients such as energy and protein, the adults were comparable to several recommended intakes for developing countries. It was suggested that intakes of vitamins A and E may be insufficient both in males and females. A preliminary evaluation of the nutritional status for the trace elements suggested that there was no severe deficiency of selenium. A mild deficiency of iodine, whose impacts on arsenic toxicity is currently unknown, is possible

The interview survey on the PERCEPTION AND BEHAVIOR TOWARD ARSENICOSIS (adults; n~500) revealed that the subjective awareness of arsenicosis did not arise while the symptoms were mild or even moderate. A number of individuals, particularly the lower-status ones, did not try any countermeasures to solve the problems nor sought medical treatment even if they regarded themselves as affected by arsenic. These results indicate the need for and the importance of health education programs.

FUTURE DIRECTION

Based on the data described above, a nutritional intervention is being implemented in these and other regions. We are particularly interested in the possibly beneficiary effects of supplementation of vitamins, which, together with arsenic-free water, was reported to be effective in improving the skin manifestations. Another important issue is the effect of arsenic on children, for which systematic evaluations are scarce.

Special volume in "Environmental Sciences"

We have recently published an anthology regarding the arsenic problems in Asian countries. Researchers in our team working in Bangladesh as well as those working in China, India (West Bengal), and Thailand contributed to this volume. The anthology has been published as a special issue of a peer-reviewed, commercial, scientific journal, "Environmental Sciences" (index in the Chemical Abstracts), Vol 8, Issue 5, December 2001.
The title of the issue is "Arsenic problems in developing countries".

In this volume, the health effects of arsenic in the field, a follow-up of an intervention trial in arsenic-affected population, as well as various aspects/approaches of the mitigation are described, which will give a good picture of what have been happening in the As-affected areas in the Asian countries. For those who are interested in this Special Issue, information is available at the publisher's web-site, or just contact Dr. Chiho Watanabe (of our UT team) at chiho@humeco.m.u-tokyo.ac.jp.


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