The public health situation of the population of Hanam Province in Vietnam is of great concern, as it is exposed daily to arsenic-contaminated drinking water. Optimising arsenic (As) removal efficiency of current sand filters at household level or switching to cleaner or As-free water sources is crucial to prevent or reduce community health risks

Bui Huy Tung

Hong, N.N.

Hung Nguyen-Viet

Tran Thi Tuyet Hanh

CGSpace

22 Sandec News 13 / 2012Community and Household Water SystemsHealth Impact of Exposure to Arsenic-Contaminated Drinking Water in VietnamThe public health situation of the population of Hanam Province in Vietnam is of great concern, as it is exposed daily to arsenic-contaminated drinking water. Optimising arsenic (As) removal efficiency of current sand filters at household level or switching to cleaner or As-free water sources is crucial to  prevent or reduce community health risks. Tung Bui-Huy1,2, Tuyet-Hanh Tran Thi2, Nhung Nguyen Hong2, Hung Nguyen-Viet2,3,4Drinking water from tubewells in Hanam ProvinceThe history of tubewell water use for drink-ing purposes dates back to the 1980s, when UNICEF introduced and provided tubewells to the rural areas of  Vietnam and to the Hanam Province, located some 60 km south of Hanoi. Use of tubewells has widely spread with the introduction of electricity, as it facilitates extraction of groundwater from tubewells by elec-tric instead of manual pumps. The  Chuyen Ngoai commune in the Duy Tien district of Hanam is a lowland area near the Red  River. It is located in an area where flood-ing occurs practically every year and the population therefore prefers to draw its water from tubewells rather than from deep wells, now almost entirely contam-inated and filled up. The commune does not dispose of any waterworks or water supply. The inhabitants can only use rain-water and tubewell water for drinking and daily  activities. Rainwater is used mainly for drinking and tubewell water for  other purposes like bathing, washing and wa-tering. 61.3 % of the households use both water sources for drinking, while 38.7 % use tubewell water throughout the year. The majority of households use tubewell water for drinking in January, February, November, and December when rain water is scarce.Arsenic contamination and weak removal efficiency with sand filtersWe collected 150 tubewell water sam-ples from the same households before and 150 water samples after sand fil-tration to determine As concentration by  atomic absorption spectrometer. The  results revealed that 98.7 % of the  water samples before filtration were heavily  contaminated with As. The As concen-trations in water prior to filtration ranged from 8 – 579 ppb (mean: 301 ppb), thereby exceeding the limit of 10 ppb for drinking water (Figs. 1 and 2). Since the majority of households design and build their own sand filters (Photo 1), the filters  usually do not meet the standard for As  removal. For example, 95.3 % of the sand filters do not meet the required thickness, or 66.9 % of the households do not adhere to the time required to replace/clean the filters and 90.5 % do not conform to the aeration standard. Average As concen-tration in water after filtration amounted to 26.5 ppb, which is still higher than the limit for drinking water for 80.4 % of the surveyed households (Fig. 2). Although As contamination distribution was hetero-geneous amongst villages in the Chuyen Ngoai commune (Fig. 1), no difference in As concentration before filtration was ob-served amongst the villages or between the areas.Health risks caused by As contaminationAssessment of the health risks was con-ducted by the Australian Environmental Health Risk Assessment Framework com-bined with analysis of As accumulated in Figure 1: Sampling site and As contamination (before filtration) in the Chuyen Ngoai commune.Figure 2: As concentration in tubewell water  before and after sand filtration.LegendSampling points and Asconcentration in tubewellwater before filtration (ppb):Residental areaNon residental area (rice field, garden...)Moc Nam CommuneHung YenCityLy Nhan DistrictTrac VanCommuneChuyen NgoaiCommuneThe Red River500 to 600 400 to 500300 to 400200 to 300100 to 200 50 to 100 8 to 50(8)(26)(44)(42)(19)(8)(3)Red River Dyke1.3%98.7%19.6%80.4%0%20%40%60%80%100%Before filtration After filtrationAs contamination (>10ppm)No As contamination (<10ppm)TungBui-Huy1323Sandec News 13 / 20121 Hanoi Medical College, 35 Doan Thi Diem   Street, Hanoi, Vietnam 2 Department of Environmental Health, Hanoi   School of Public Health, Hanoi, Vietnam 3 Eawag/Sandec, Switzerland4 Department of Epidemiology and Public   Health, Swiss Tropical and Public Health    Institute, Basel, Switzerland and University of    BaselThis work was supported by the Swiss National Science Foundation (SNSF) and the Swiss Agency for Development and Cooperation (SCD) through the programme of the Swiss National Centre of Competence in Research (NCCR) North-South.Contact: Hung.Nguyen@eawag.chhair samples of 150 persons. Exposure was determined not only by measuring As concentrations in tubewell water samples as aforementioned, but also by estimat-ing the water volume consumed as drink-ing water by 150 interviewed households. This provided data on the daily consump-tion volume via the oral route. As arsenic enters the body through the oral route, other exposure pathways, such as bathing and washing, were not considered. The health risk was characterised by compar-ing the As levels in water with the na tional technical regulations on drinking water quality, and by comparing the daily con-sumption dose with the Tolerable Daily In-take (TDI) value established by WHO. Fi-nally, the cancer risk of people exposed to As-contaminated water sources through eating and drinking was estimated by ap-plying the Cancer Slope Factor index and lifetime average daily dose.Twenty-four hair samples (16 %) had As levels exceeding the limit of 0.57 mg/kg, of which 6 samples (4 %) revealed an As con-centration higher than 0.8 mg/kg and cor-responding to the standard diagnosis of chronic arsenic toxicity. Arsenic levels in hair were statistically significant to be cor-related with As concentration in tubewell water after filtration.Daily consumption of As amongst 40 % of adults was higher than the TDI  level (1 μg/kg/day). The average cancer risk in adults from drinking filtered tubewell wa-ter amounted to 24 x 10-5. In other words, based on a population of 100 000  people consuming As-contaminated water, 24 persons are prone to have or develop can-cer. This cancer risk would be 1.2 and 1.5 times higher after 5 and 10 years of drink-ing filtered water, respectively. By  using filtered tubewell water over 70 years, the average cancer risk level amounts to 204 x 10-5. If tubewell water is used with-out filtering, the risk of cancer is 11.3 times higher. Different cancer risk sce-narios are presented in Fig. 3.Towards prevention and mitigation of health risksOur study revealed a high As contamina-tion level in tubewell water in Hanam, and a high risk of exposure to using As-con-taminated water for drinking. Improved filtration measures or replacement of the current drinking water sources (e.g. by rain water, clean piped water etc) are recom-mended to prevent health risks of the  local population. Risk awareness among the population, and especially amongst health workers, should be raised to prevent and mitigate the daily health effects posed by As contamination.Figure 3: Estimated risk of cancer due to As-contaminated water.  R1: Current consumption of filtered water, R2 and R3: Risk after 5 and 10 years of drinking filtered water, respectively, R4: Risk of consuming filtered water over a lifetime. Photo 1: Sand filter with tubewell in Chuyen Ngoai, Hanam.Probability of risk occurrenceRisk of cancer (10-4)1.00.80.60.40.200 0.5 1.0 1.5 2.0R1R2R3R4

Health impact of exposure to arsenic-contaminated drinking water in Vietnam

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Health impact of exposure to arsenic-contaminated drinking water in Vietnam

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