Arsenic removal from iron-containing groundwater by delayed aeration in dual-media sand filters.

Generally, abstracted groundwater is aerated, leading to iron (Fe2+) oxidation to Fe3+ and precipitation as Fe3+-(hydr)oxide (HFO) flocs. This practice of passive groundwater treatment, however, is not considered a barrier for arsenic (As), as removal efficiencies vary widely (15-95%), depending on Fe/As ratio. This study hypothesizes that full utilization of the adsorption capacity of groundwater native-Fe2+ based HFO flocs is hampered by rapid Fe2+ oxidation-precipitation during aeration before or after storage. Therefore, delaying Fe2+ oxidation by the introduction of an anoxic storage step before aeration-filtration was investigated for As(III) oxidation and removal in Rajshahi (Bangladesh) with natural groundwater containing 329(±0.05) µgAs/L. The results indicated that As(III) oxidation in the oxic storage was higher with complete and rapid Fe2+ oxidation (2±0.01 mg/L) than in the anoxic storage system, where Fe2+ oxidation was partial (1.03±0.32 mg/L), but the oxidized As(V)/Fe removal ratio was comparatively higher for the anoxic storage system. The low pH (6.9) and dissolved oxygen (DO) concentration (0.24 mg/L) in the anoxic storage limited the rapid oxidation of Fe2+ and facilitated more As(V) removal. The groundwater native-Fe2+ (2.33±0.03 mg/L) removed 61% of As in the oxic system (storage-aeration-filtration), whereas 92% As removal was achieved in the anoxic system.

Perceptions and behavior related to noncommunicable diseases among slum dwellers in a rapidly urbanizing city, Dhaka, Bangladesh: a qualitative study.

The increasing burden of noncommunicable diseases (NCDs) in Bangladesh can be attributable to rapid urbanization and coinciding changes in lifestyle accompanied by nutrition transition. The objective of this study is to explore respondents' lived experiences and perceptions relating to NCDs and nutrition change in an urban slum community in Dhaka. Qualitative methods were employed to explore a general understanding of behavior related to NCDs among residents of the slum community. We conducted key informant interviews of six men and seven women of various backgrounds and five focus group discussions to focus salient topics emerged from the interviews. The transcriptions of the audio-recordings were thematically analyzed, using the constant comparison method. Four major themes emerged: (1) financial hardship influencing health; (2) urbanized lifestyle affecting diet; (3) tobacco and sweetened tea as cornerstones of social life; and (4) health-seeking behavior utilizing local resources. One notable finding was that even with general economic improvement, respondents perceived poverty to be one of the major causes of NCDs. A promising finding for potentially curbing NCDs was the current trend for women to walk for exercise contrary to the commonly held notion that urban dwellers generally lead sedentary lifestyles. This study described how urban slum dwellers in Dhaka, experiencing a transition from a traditional to urbanized lifestyle, perceived their daily practices in relation to NCDs and nutrition. Our research revealed both adverse and encouraging elements of perceptions and behavior related to NCDs, which may contribute to the optimal design of NCD prevention and health promotion programs.

Prevalence of non-communicable disease risk factors among poor shantytown residents in Dhaka, Bangladesh: a community-based cross-sectional survey.

OBJECTIVES: This study aims to describe the prevalence of non-communicable disease (NCD) risk factors among the urban poor in Bangladesh. DESIGN: We conducted a community-based cross-sectional epidemiological study. SETTING: The study was conducted in a shantytown in the city of Dhaka. There were 8604 households with 34 170 residents in the community. Those households were categorised into two wealth strata based on the housing structure. PARTICIPANTS: The study targeted residents aged 18-64 years. A total of 2986 eligible households with one eligible individual were selected by simple random sampling stratified by household wealth status. A total of 2551 residents completed the questionnaire survey, and 2009 participated in the subsequent physical and biochemical measurements. OUTCOME MEASURES: A modified WHO survey instrument was used for assessing behavioural risk factors and physical and biochemical measurements, including glycated haemoglobin (HbA1c). The prevalence of NCD risk factors, such as tobacco use, fruit and vegetable intake, overweight/obesity, hypertension, diabetes (HbA1c ≥6.5%) and dyslipidaemia, was described according to household wealth status and gender differences. RESULTS: The prevalence of current tobacco use was 60.4% in men and 23.5% in women. Most of them (90.8%) consumed more than 1 serving of fruits and vegetables per day; however, only 2.1% consumed more than 5 servings. Overweight/obesity was more common in women (39.2%) than in men (18.9%), while underweight was more common in men (21.0%) than in women (7.1%). The prevalence of hypertension was 18.6% in men and 20.7% in women. The prevalence of diabetes was 15.6% in men and 22.5% in women, which was much higher than the estimated national prevalence (7%). The prevalence of raised total cholesterol (≥190 mg/dL) was 25.7% in men and 34.0% in women. CONCLUSION: The study identified that tobacco use, both overweight and underweight, diabetes, hypertension and dyslipidaemia were prevalent among the urban poor in Bangladesh.

Population profile and residential environment of an urban poor community in Dhaka, Bangladesh.

OBJECTIVES: A population survey was conducted in an urban shantytown in Bangladesh, as a baseline study of future epidemiological studies. This paper aims to describe the findings of the study, including the population profile and residential environment of the urban poor. METHODS: We conducted a complete count household survey in an urban poor community in Dhaka. Using a brief structured questionnaire in Bengali language, trained interviewers visited each household and asked questions such as: duration of residence; ownership of house, toilet and kitchen; water supply; number of family members; age, sex, education, occupation, tobacco use, and history of diseases of each family member. RESULTS: We found that there were 8604 households and 34,170 people in the community. Average number of household members was 4.0. Most people had access to safe water, but only 16% lived in the house with a toilet. Based on the proxy indicators of household wealth levels, we identified that about 39% were relatively well-off, while the rest were very poor. Tobacco use was prevalent in men regardless of age and in women aged over 35 years. Prevalence of self-reported hypertension and diabetes was slightly higher in women than in men, although over 70% of the respondents didn't know if they had such diseases. Incidences of diarrhea in the last one month were relatively low. CONCLUSIONS: The study showed population profile and sanitation environment in an urban poor community by a complete count survey. We expect the study to serve as a baseline for future epidemiological studies.

Drinking cholera: salinity levels and palatability of drinking water in coastal Bangladesh.

OBJECTIVES: To measure the salinity levels of common water sources in coastal Bangladesh and explore perceptions of water palatability among the local population to investigate the plausibility of linking cholera outbreaks in Bangladesh with ingestion of saline-rich cholera-infected river water. METHODS: Hundred participants took part in a taste-testing experiment of water with varying levels of salinity. Salinity measurements were taken of both drinking and non-drinking water sources. Informal group discussions were conducted to gain an in-depth understanding of water sources and water uses. RESULTS: Salinity levels of non-drinking water sources suggest that the conditions for Vibrio cholerae survival exist 7-8 days within the local aquatic environment. However, 96% of participants in the taste-testing experiment reported that they would never drink water with salinity levels that would be conducive to V. cholerae survival. Furthermore, salinity levels of participant's drinking water sources were all well below the levels required for optimal survival of V. cholerae. Respondents explained that they preferred less salty and more aesthetically pleasing drinking water. CONCLUSION: Theoretically, V. cholerae can survive in the river systems in Bangladesh; however, water sources which have been contaminated with river water are avoided as potential drinking water sources. Furthermore, there are no physical connecting points between the river system and drinking water sources among the study population, indicating that the primary driver for cholera cases in Bangladesh is likely not through the contamination of saline-rich river water into drinking water sources.

Indoor air pollution and health of children in biomass fuel-using households of Bangladesh: comparison between urban and rural areas.

OBJECTIVES: Indoor air pollutants from biomass combustion pose a risk for respiratory diseases in children. It is plausible that distinct differences in the indoor air quality (IAQ) exist between urban and rural areas in developing countries since the living environment between these two areas are quite different. We have investigated possible differences in IAQ in urban and rural Dhaka, Bangladesh and the association of such differences with the incidence of respiratory and some non-respiratory symptoms in children of families using biomass fuel. METHODS: Indoor air concentrations of carbon monoxide (CO), carbon dioxide (CO(2)), dust particles, volatile organic compounds (VOCs), and nitrogen dioxide were measured once in the winter and once in the summer of 2008. Health data on 51 urban and 51 rural children under 5 years of age from 51 families in each area were collected once a week starting in the winter and continuing to the summer of 2008. RESULTS: Mean concentrations of CO, CO(2,), dust particles, and major VOCs were significantly higher in urban kitchens than in rural ones (p < 0.05). The incidence rate ratio (IRR) suggests that compared to the urban children, the children in the rural area suffered significantly more from respiratory symptoms [IRR 1.63, 95% confidence interval (CI) 1.62-1.64], skin itchiness (IRR 3.3, 95% CI 1.9-5.7), and diarrhea (IRR 1.8, 95% CI 1.4-2.4), while fewer experienced fever (IRR 0.5, 95% CI 0.4-0.6). No difference was observed for other symptoms. CONCLUSIONS: We found lower IAQ in the homes of urban biomass fuel-users compared to rural ones in Bangladesh but could not attribute the occurrence of respiratory symptoms among children to the measured IAQ. Other factors may be involved.

Indoor air pollution and the health of children in biomass- and fossil-fuel users of Bangladesh: situation in two different seasons.

OBJECTIVES: Indoor air pollution levels are reported to be higher with biomass fuel, and a number of respiratory diseases in children are associated with pollution from burning such fuel. However, little is known about the situation in developing countries. The aim of the study was to compare indoor air pollution levels and prevalence of symptoms in children between biomass- and fossil-fuel-using households in different seasons in Bangladesh. METHODS: We conducted a cross-sectional study among biomass- (n = 42) and fossil-fuel (n = 66) users having children <5 years in Moulvibazar and Dhaka, Bangladesh. Health-related information of one child from each family was retrieved once in winter (January 2008) and once in summer (June 2008). The measured pollutants were carbon monoxide (CO), carbon dioxide (CO(2)), dust particles, volatile organic compounds (VOCs), and nitrogen dioxide. RESULTS: Mean concentration of dust particles and geometric mean concentrations of VOCs such as benzene, toluene, and xylene, which were significantly higher in biomass- than fossil-fuel-users' kitchens (p < 0.05), were significantly higher in winter than in summer (p < 0.05). Levels of CO and CO(2), which were significantly higher in biomass than fossil-fuel users (p < 0.05), were significantly higher in summer than winter (p < 0.05). However, no significant difference was found in the occurrence of symptoms between biomass- and fossil-fuel users either in winter or in summer. CONCLUSIONS: It was suggested that the measured indoor air pollution did not directly result in symptoms among children. Other factors may be involved.