Water Quality Index for measuring drinking water quality in rural Bangladesh: a cross-sectional study – Journal of Health, Population and Nutrition
Assessment of drinking water quality is a timely requirement amid emerging public health problems in this context where availability of safe water is at risk due to natural and man-made activities. This cross-sectional study conducted across the country aimed at measuring drinking water quality using WQI which delivered messages on the composite effect of chemical parameters on water. The present study is a fact finding or exploratory study contributing to designing and improving program interventions which cover a larger population including high arsenic, high saline prone coastal areas. There is duality about spatial and temporal variations of some chemical parameters. A periodic assessment on arsenic concentration depicts no association with seasonal variations, while repeated assessment of arsenic contents in water based on seasons is assumed to bring little value in health surveillance [18]. In contrast, seasonal and spatial variations of arsenic concentrations in groundwater have been reported by Shrestha et al. [19].
The study findings revealed that drinking water was slightly alkaline, although the ideal pH for human consumption is stated to be 7.4 [20]. A controlled pH of water is suggested in WHO guideline to reduce the corrosion and contamination of drinking water having health consequences. Water pH is influenced by a number of factors including rock and soil composition and the presence of organic materials or other chemicals. Napacho and Manyele [21] found that pH values in shallow tubewells varied between 6.7 and 8.3 due to dissolved minerals from the soil and rocks. They further explained higher alkalinity by the presence of two common minerals, calcium and magnesium, affecting the hardness of the water. On the other hand, water with low pH values is meant to be acidic, soft, and corrosive.
The median value of manganese concentrations exceeded Bangladesh standard at most of the study sites. Other Bengali studies have reported higher manganese levels in drinking water in terms of WHO standards [22]. For example, Islam et al. [23] reported that 52 % of pond-sand filter and 45 % of pond water exceeded Bangladesh drinking water standards. The median value at our sample sites was relatively lower than some previous findings (about 0.8 and 0.9 mg/L) [24, 25] but higher than the 0.1 mg/L reported by Bouchard [26].
Children are reported to be particularly vulnerable to higher manganese concentrations due to their low protective mechanisms. Approximately 8 % of children were exposed to excess manganese concentrations that exceeded both WHO and Bangladesh standards (>0.4 and >0.1 mg/L, respectively). We found higher exposure to manganese in lowest wealth group. This finding has similarity with the other study conducted in Araihazar, Bangladesh [27]. Less exposure among the infants was reported by mothers who had access to TV. Besides, participants living in poor-quality housing type (mud vs. concrete) were more likely to report exposure among the infants. Several studies have reported that exposure to high manganese concentrations threatens children’s cognitive [28], behavioral, and neuropsychological health [25]. However, the potential impact of lower exposure and interactions with other metals are less well characterized. Infants and children are reported to be more susceptible to manganese toxicity than adults [27], and a number of Bangladesh studies have shown that children’s intellectual function, and consequently their academic achievement, was adversely affected by manganese exposure in drinking water [22, 25, 27]. Contradictory to these findings, a higher manganese level in drinking water was shown to be protective against fetal loss during pregnancy of undernourished women in Bangladesh [29].
In most of the sample sites (9 out of 12 sites), iron content in drinking water exceeded upper acceptable limit (1.0 mg/L) of Bangladesh standard. A previous study in rural Bangladesh revealed 50 times higher iron concentrations (mean value 16.7 mg/L) in ground water than WHO’s limit (0.3 mg/L) and reported that 47 % of women consumed above the daily limit of iron (45 mg), likely to increase the risk of health problems [30]. Consumption of >30 mg of iron per day in drinking water was associated with a reduced risk of anemia in individuals without thalassemia [31]. In Gaibandha, half of female respondents consuming >42 mg of iron from drinking water stayed within tolerable limits. If this limit were exceeded, however, the populations would be likely to experience health-related problems including gastrointestinal distress, zinc absorption, and others [32].
Approximately 2 % of women in developed countries but 50 % in developing countries are anemic, contributing to high rates of maternal mortality in developing countries [33]. Iron-deficiency anemia is one of the top ten contributing factors to the global burden of diseases and is considered a public health problem with a high risk of morbidity and mortality in pregnant women and young children [34]. In our study, about half of the female participants were exposed to higher iron concentrations in drinking water which exceeded both WHO and Bangladesh standard. The health impacts of exceeding recommended WHO levels of chemical substances such as iron are often not well documented [32]. There is a duality to iron concentrations: on the one hand, iron deficiency can cause anemia and fatigue, while on the other, excess iron can cause multiple organ dysfunction (e.g., liver fibrosis and diabetes) [35]. In a 10-year period of study in Bangladesh, the prevalence of anemia in women of reproductive age ranged between 23 and 95 % depending on age, pregnancy status, and residency. However, more recent studies have reported iron deficiency as the most important determinant of 7 to 60 % of anemia cases in Bangladesh [36].
Salinity in drinking water was found higher (>600 mg/L) only in Rupsha (Khulna) and Patharghata (Barguna). Geographically, these two upazilas are coastal areas. Salinity problems in coastal regions are assumed to be the effects of climate change [37], although industrial and domestic wastes [38] and geological and soil characteristics [21] are also thought to contribute. Bangladesh is at the forefront of the negative effects of climate change and has faced dramatic rises in sea level over the last three decades. Approximately 20 million people living in coastal Bangladesh [24] are dependent on tubewells, rivers, and ponds for drinking water, and these sources are increasingly becoming saline due to rising sea levels [39]. Salinity has intruded over 100 km inland from the Bay of Bengal with consequent health impacts: in a 2008 survey, higher rates of preeclampsia and hypertension were reported in the coastal than non-coastal population [40]. Consistent with this, Khan et al. [41] reported that hypertensive disorders were associated with salinity in drinking water. Furthermore, reducing salt consumption from the global estimated levels of 9–12 g/day [42] to an acceptable limit of 5 g/day [43] would be predicted to reduce blood pressure and stroke/cardiovascular disease by 23 and 17 %, respectively [44].
Most households in Dohar, Shibchar, and Sonargaon used shallow tubewells for drinking, which were affected by high levels of arsenic. In Shibchar (West Kakor village), most tubewells were affected by arsenic, and the villagers were unaware of which tubewell was arsenic free; therefore, they collected drinking water from any tubewell. In some cases (e.g., Sonargaon), people used arsenic-affected drinking water sources even though they knew that the water was contaminated and damaging to health. Bladder cancer risk is increased 2.7 and 4.2 times by arsenic exposure of 10 and 50 μg/L in water, respectively. In this study, there was an 83 % chance of developing bladder cancer and a 74 % probability of mortality at a 50 μg/L exposure level. Mortality rates are 30 % higher at 150 than 10 μg/L [45]. According to a national survey conducted in 2009 by UNICEF/BBS (2011), 53 and 22 million people were exposed to arsenic according to WHO and BDWS standards, respectively. Arsenic has been detected in the groundwater of 322 upazilas (sub-districts) and 61 districts in Bangladesh [46]. The health effects of prolonged and excessive inorganic arsenic exposure include arsenicosis, skin diseases, skin cancers, internal cancers (bladder, kidney, and lung), diabetes, raised blood pressure, and reproductive disorders [47].
The overall suitability of drinking water was assessed using a combined measure of water quality parameters: the WQI. The chemical parameters (pH, iron, manganese, salinity, and arsenic) of water samples were used to calculate the WQI value at each site. We applied the weighted arithmetic WQI method to calculate WQI values. In this method, the permissible WQI value for drinking is considered to be 100, the water quality being considered poor if the value exceeded this acceptable limit. Water quality was found excellent only in Rangabali (Patuakhali) and Kurigram Sadar. The water was considered excellent at these sites mainly due to low chemical parameter values contributing to lower composite effect on drinking water quality. In Shibchar (Madaripur), water was categorized as unsuitable for drinking, mainly due to high manganese and arsenic levels found in water at these sites. At most sample sites (e.g., Alfadanga, Kendua, Debhata, Shajahanpur, and Bijoynagar), water was classified as “poor” for drinking due to high manganese values. Moreover, arsenic was also found to be high in Alfadanga (Faridpur) and Kendua (Netrokona). However, in Anwara (Chittagong) and Kamalganj (Moulvibazar), the chemical parameter values in the water samples were very high and contributed to very poor-quality drinking water.
Most respondents at the sample sites used shallow tubewells to obtain drinking water due to lower installation costs. In some areas, such water from shallow tubewells was reported to have high iron and arsenic levels. In coastal districts such as Barguna, Satkhira, and Khulna, water from both shallow and deep tubewells were salty, as reported by the respondents. Yisa and Jimoh [16] reported higher levels of iron and manganese that contributed to poor-quality drinking water. These characteristics are consistent with unplanned waste disposal, agricultural run-off including pesticide or fertilizer, and other environmentally hazardous activities polluting surface water [48].
The study had some limitations. This study embraced cross-sectional study design. However, it would have been better to collect samples throughout the year addressing seasonality and depth of wells. We could not collect data on other WHO-recommended parameters which was beyond our scope of work. Therefore, the analysis has been limited to few water parameters as the requirement of BRAC WASH program and due to resource constraints. Measuring other WHO-recommended chemical parameters might have been a future concern for the program. In addition, water pH would have been tested on the spot using pH meter which was not possible for this study due to limited resources. The limitations observed in this study highlight the insights of future scope of work for research divisions and WASH program.
