Arsenic and hypertension in Bangladesh

Editor – The prevalence, awareness, treatment and control of hypertension among the elderly in Bangladesh and India were discussed recently in the Bulletin (1). I should like to draw attention to the role of arsenic poisoning in this respect. My colleagues and I previously reported in the Bulletin that the contamination of groundwater by arsenic in Bangladesh can be described as "the largest poisoning of a population in history, with millions of people exposed" (2). Tube-wells were installed to provide safe drinking-water and prevent diarrhoeal diseases, but were not tested for arsenic.

We have recently described a link between arsenic in drinking-water and the occurrence of diabetes mellitus and hypertension in Bangladesh (3). From a public health point of view, arsenic exposure has attracted great interest in the past few decades, especially regarding the risk of lung cancer among copper-smelting workers, but also the risk of skin and bladder cancer seen in connection with exposure through drinking-water. Studies in other countries with long-term exposure indicate that 1 in 10 persons who drink water containing 500 mg of arsenic per litre may ultimately die from arsenic-related cancers of the lung, bladder and skin.

Epidemiological data (4) indicate the dose–effect relationship between levels of arsenic in drinking-water and the pre-valence of hypertension. For a 50 mg/l concentration, the risk of hypertension was doubled compared with non- exposure. These results confirm findings reported from Taiwan, China (5). Considering time-weighted mean arsenic exposure (500 mg/l, 500–1000 mg/l, and >1000 mg/l), the adjusted prevalence ratios for hypertension among the subjects without skin lesions were 0.8 (95% confidence interval (CI) = 0.4–1.8), 1.7 (95% CI = 0.8–3.3), and 2.2 (95% CI = 1.1–4.3), respectively (4). With the same reference and exposure categories, subjects with skin lesions had adjusted prevalence ratios of 1.4 (95% CI = 0.6–3.2), 2.5 (95% CI = 1.2–5.1), and 2.9 (95% CI = 1.3–6.1), respectively (4). The dose–response trend was significant both for subjects with and without skin lesions (P50 mg/l (6). Given this frequency of exposure and the indicated excess risk for hypertension, a non-negligible proportion of the future hypertension burden in Bangladesh could be attributed to arsenic poisoning.

The epidemiological evidence supporting a causal association between well water containing inorganic arsenic and occurrence of hypertension points to the need to take arsenic exposure into account in further studies on hypertension.

Mahfuzar Rahman²

Conflicts of interest: none declared.

1. Hypertension Study Group. Prevalence, awareness, treatment and control of hypertension among the elderly in Bangladesh and India: a multicentre study. Bulletin of the World Health Organization 2001;79:490-500.

2. Smith AH, Lingas EO, Rahman M. Contamination of drinking-water by arsenic in Bangladesh: a public health emergency. Bulletin of the World Health Organization 2000;78:1093-103.

3. Rahman M. Nonmalignant health effects of arsenic exposure. Linköping: Linköping University; 1999. Medical Dissertation No. 612.

4. Rahman M, Tondel M, Ahmad SA, Chowdhury IA, Faruquee MH, Axelson O. Hypertension and arsenic exposure in Bangladesh. Hypertension 1999;33:74-8.

5. Chen CJ, Hsueh YM, Lai MS, Shyu MP, Chen SY, Wu MM, et al. Increased prevalence of hypertension and long-term arsenic exposure. Hypertension 1995;25:53-60.

6. British Geological Survey. Phase 2 groundwater studies of arsenic contamination in Bangladesh. Nottingham: British Geological Survey; 2001. Available at URL: www.bgs.ac.uk/arsenic

² Epidemiologist, Public Health Sciences Division, ICDDR, B: Centre for Health and Population Research, GPO Box 128, Mohakhali C/A, Dhaka 1000, Bangladesh (email: mahfuzar@icddrb.org).