Mohammad Alauddin

Electrochemical measurement and speciation of inorganic arsenic in groundwater of Bangladesh

The presence of arsenic in groundwater above the maximum permissible limit of 50 mug l(-1) has threatened the health of more than 50 million people in Bangladesh and neighboring India. We report here the development of an inexpensive anodic stripping voltammetric (ASV) technique for routine measurement and speciation of arsenic in groundwater. The measurements are validated by more expensive atomic absorption, atomic emission and other techniques. To understand the present situation in Bangladesh, we measured As(III) in 960 water samples collected from 18 districts. A random distribution of 238 samples was used to measure both As(III) and As(V). The results from the present study indicate that most toxic form of inorganic arsenic, As(III), has the broad range of 30-98%. It shows 60% of the samples have 10 mug l(-1) and 44% of the samples have 50 mug l(-1) or more As(III). The fractional distribution pattern shows significant skew towards high percent occurrence which may indicate a progressive reduction process with a single source or a single mechanism for the formation of As(III). For direct consumption, this is possibly one of the most toxic groundwater known today. Speciation distribution at groundwater pH value shows H(3)AsO(3) is the predominant species including H(2)AsO(4)(-) and H(2)AsO(4)(2-) whose distribution is significantly pH dependent. This is also supported by E(h)-pH measurements. The depth distribution for Kushtia shows most of the As(III) is located within 100-200 ft deep aquifers. Similar fractional distribution of As(III) is found in deeper aquifers and may indicate contamination by leakage from upper aquifer. This study clearly demonstrates the aquifer environment is reductive and conducive to the formation of As(III) species.

Groundwater arsenic contamination in Bangladesh—21 Years of research

Department of Public Health Engineering (DPHE), Bangladesh first identified their groundwater arsenic contamination in 1993. But before the international arsenic conference in Dhaka in February 1998, the problem was not widely accepted. Even in the international arsenic conference in West-Bengal, India in February, 1995, representatives of international agencies in Bangladesh and Bangladesh government attended the conference but they denied the groundwater arsenic contamination in Bangladesh. School of Environmental Studies (SOES), Jadavpur University, Kolkata, India first identified arsenic patient in Bangladesh in 1992 and informed WHO, UNICEF of Bangladesh and Govt. of Bangladesh from April 1994 to August 1995. British Geological Survey (BGS) dug hand tube-wells in Bangladesh in 1980s and early 1990s but they did not test the water for arsenic. Again BGS came back to Bangladesh in 1992 to assess the quality of the water of the tube-wells they installed but they still did not test for arsenic when groundwater arsenic contamination and its health effects in West Bengal in Bengal delta was already published in WHO Bulletin in 1988. From December 1996, SOES in collaboration with Dhaka Community Hospital (DCH), Bangladesh started analyzing hand tube-wells for arsenic from all 64 districts in four geomorphologic regions of Bangladesh. So far over 54,000 tube-well water samples had been analyzed by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS). From SOES water analysis data at present we could assess status of arsenic groundwater contamination in four geo-morphological regions of Bangladesh and location of possible arsenic safe groundwater. SOES and DCH also made some preliminary work with their medical team to identify patients suffering from arsenic related diseases. SOES further analyzed few thousands biological samples (hair, nail, urine and skin scales) and foodstuffs for arsenic to know arsenic body burden and people sub-clinically affected. SOES and DCH made a few follow-up studies in some districts to know their overall situations after 9 to 18 years of their first exposure. The overall conclusion from these follow-up studies is (a) villagers are now more aware about the danger of drinking arsenic contaminated water (b) villagers are currently drinking less arsenic contaminated water (c) many villagers in affected village died of cancer (d) arsenic contaminated water is in use for agricultural irrigation and arsenic exposure from food chain could be future danger. Since at present more information is coming about health effects from low arsenic exposure, Bangladesh Government should immediately focus on their huge surface water management and reduce their permissible limit of arsenic in drinking water.

Antioxidants in detoxification of arsenic-induced oxidative injury in rabbits: preliminary results.

Abstract To assess the oxidative injuries caused by arsenic toxicity in rabbits and evaluate the detoxifying effects of exogenous antioxidants, we administered arsenic trioxide (3–5 mg/kg/day) in rabbits through a feeding tube for seven days. These rabbits were then treated with a recipe of vitamins, zinc, selenium (VZS) or a plant polyphenol or a placebo for the next seven days. Blood samples were collected from ear vein for spectrophotometric assay of reduced glutathione (GSH), thiobarbituric acid reactive substances (TBARS), and nitrite/nitrate (NO x ; index of nitric oxide formation) before arsenic administration, seven days after arsenic administration, and seven days after antioxidant treatment. The total arsenic concentrations in hair and spot urine samples of rabbits before arsenic administration were 0.6 ± 0.21 µg/g and 34.0 ± 5.9 µg/L, respectively. Administration of arsenic trioxide significantly increased arsenic concentrations in hair and in urine to 2.8 ± 0.40 µg/g (p<0.001) and 7372 ± 1392.0 µg/L (p<0.001), respectively. Arsenic administration to rabbits significantly reduced GSH concentration (post-arsenic,17.5 ± 0.81 mg/dL vs. pre-arsenic, 32.0 ± 0.76 mg/dL, p<0.001), increased TBARS concentration (post-arsenic, 8 ± 1.1 µM vs. pre-arsenic, 5 ± 0.7 µM, p<0.05), and NO x concentration (post-arsenic, 465 ± 38.5 µM vs. pre-arsenic, 320 ± 24.7 µM, p<0.001) as compared to the pre-arsenic levels. There was a negative correlation between TBARS and GSH concentrations (r = −0.464, p<0.01) and between NO x and GSH concentrations (r = − 0.381, p<0.05) of intoxicated rabbits. The recovery of the depleted GSH was significantly greater in the polyphenols (77.0 ± 12.0%) or VZS (67.0 ± 17.0%) treatment groups compared with the placebo group (36.0 ± 7.0%). The decrease in NO x level of arsenic-treated rabbits was significantly greater in polyphenols treatment group than the placebo group (60.0 ± 9.0% vs. 17.0 ± 6.0%, p<0.001). These results indicate that arsenic induces toxicity in rabbits associated with an increase in lipid peroxidation. Arsenic toxicity increases nitric oxide production in the body. Exogenous antioxidants such as polyphenols and recipe of vitamins, zinc, and selenium are useful for arsenic detoxification.

SOLID PHASE MICROEXTRACTION: MEASUREMENT OF VOLATILE ORGANIC COMPOUNDS (VOCs) IN DHAKA CITY AIR POLLUTION

ABSTRACT A solid phase microextraction (SPME) technique was applied for the sampling of volatile organic compounds (VOCs) in ambient air polluted by two stroke autorickshaw engines and automobile exhausts in Dhaka city, Bangladesh. Analysis was carried out by capillary gas chromatography (GC) and GC-mass spectrometry (MS). The methodology was tested by insitu sampling of an aromatic hydrocarbon mixture gas standard with a precision of ±5% and an average accuracy of 1–20%. The accuracy for total VOCs concentration measurement was about 7%. VOCs in ambient air were collected by exposing the SPME fiber at four locations in Dhaka city. The chromatograms showed signature similar to that of unburned gasoline (petrol) and weathered diesel containing more than 200 organic compounds; some of these compounds were positively identified. These are normal hydrocarbons pentane (n-C5H12) through nonacosane (n-C29H60), aromatic hydrocarbons: benzene, toluene, ethylbenzene, n-propylbenzene, n-butylbenzene, 1,3,5-trimethylbenzene, xylenes, and 1-isocyanato-3-methoxybenzene. Two samples collected near an autorickshaw station contained 783 000 and 1 479 000 µg/m3 of VOCs. In particular, the concentration of toluene was 50–100 times higher than the threshold limiting value of 2000 µg/m3. Two other samples collected on street median showed 135 000 µg/m3 and 180 000 µg/m3 of total VOCs. The method detection limit of the technique for most semi-volatile organic compounds was 1 µg/m3.

Speciation of Arsenic Metabolite Intermediates in Human Urine by Ion-Exchange Chromatography and Flow Injection Hydride Generation Atomic Absorption Spectrometry

Abstract Biomethylation is considered as the principal metabolic and detoxification pathway for inorganic arsenic in human. The end products of methylation are less toxic and more readily excreted through urine. Therefore, speciation of metabolites in urine is essential to a better understanding of arsenic metabolism, health effects and detoxification ability of individuals exposed to arsenic through drinking water, food and environmental materials. Speciation of inorganic and methylated arsenic in urine is an analytical challenge and often requires expensive instrumentation. We have applied a relatively inexpensive technique for the separation and analysis of various arsenic species, such as, arsenite, arsenate, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in human urine. The technique is based on ion exchange chromatographic separation followed by flow injection hydride generation atomic absorption spectroscopy (FI-HG-AAS). The detection limit varies from 1.0 to 2.0 µg/L for various species. The technique has been successfully applied to speciation of arsenic metabolite intermediates in urine samples collected from patients in Hajiganj, a serious arsenic affected area in Bangladesh. Arsenite (AsIII) was found to be the major component in the urine from these patients. Our findings from patients in Hajiganj, Bangladesh are presented in this paper. The technique permits us to carry out arsenic speciation in urine, essential for toxicological studies and possible nutritional intervention in combating arsenic poisoning in Bangladesh.

Observation of the seleno bis-(S-glutathionyl) arsinium anion in rat bile.

Certain arsenic and selenium compounds show a remarkable mutual cancelation of toxicities, where a lethal dose of one can be voided by an equimolar and otherwise lethal dose of the other. It is now well established that the molecular basis of this antagonism is the formation and biliary excretion of seleno bis-(S-glutathionyl) arsinium anion [(GS)2AsSe](-). Previous work has definitively demonstrated the presence of [(GS)2AsSe](-) in rabbit bile, but only in the presence of other arsenic and selenium species. Rabbits have a gall bladder, which concentrates bile and lowers its pH; it seems likely that this may be responsible for the breakdown of biliary [(GS)2AsSe](-). Since rats have no gall bladder, the bile proceeds directly through the bile duct from the hepatobiliary tree. In the present work we have shown that the primary product of biliary co-excretion of arsenic and selenium in rats is [(GS)2AsSe](-), with essentially 100% of the arsenic and selenium present as this species. The chemical plausibility of the X-ray absorption spectroscopy-derived structural conclusions of this novel arsenic and selenium co-excretion product is supported by density functional theory calculations. These results establish the biomolecular basis to further explore the use of selenium dietary supplements as a possible palliative for chronic low-level arsenic poisoning of human populations.

Selenium content of rice, mixed plant foods and fish from Bangladesh

Selenium (Se), an essential trace mineral, is obtained by individuals from foods ingested and is necessary for 25 human proteins including the antioxidant family of glutathione peroxidases. Since plants are not known to require Se for growth, the quantity of this mineral in plant foods depends on the soluble Se in soils that is passively accumulated by plants. As all animals require Se, it is usually stored more uniformly and to a greater degree in animal than plant protein foods. Owing to the alluvial origin, high rainfall and flooding upon the soils of Bangladesh these soils appear to be low in measured soluble Se. These low levels of soluble Se in Bangladeshi soils reflect the low levels of Se in plant foods, rice and vegetables, staples of the rural and poor Bangladeshis diet. This study reports on the dry-weight content of Se found in samples of rice, other plant foods and fish from Bangladesh. Rice grain averaged 0.105 µg Se g−1 from Jessore and 0.212 µg Se g−1 from 5 other districts of Bangladesh. Gourds and potatoes from Jessore averaged 0.471 and 0.181 µg Se g−1 respectively. All other district plant foods averaged 0.26 µg Se g−1. All 7 different but unidentified species of fish sampled in Jessore and quantitated fluorimetrically averaged 1.318 µg Se g−1. Fish was the single highest food source of dietary Se per unit dry weight. Fish in particular, but also other animal foods, are likely to serve as better dietary sources of Se for the people of Bangladesh.

Assessment of Nutritional Status of Infants Living in Arsenic-Contaminated Areas in Bangladesh and Its Association with Arsenic Exposure

Data is scarce on early life exposure to arsenic and its association with malnutrition during infancy. This study followed the nutritional status of a cohort of 120 infants from birth to 9 months of age in an arsenic contaminated area in Bangladesh. Anthropometric data was collected at 3, 6 and 9 months of the infant’s age for nutritional assessment whereas arsenic exposure level was assessed via tube well drinking water arsenic concentration at the initiation of the study. Weight and height measurements were converted to Z-scores of weight for age (WAZ-underweight), height for age (HAZ-stunting), weight for height (WHZ-wasting) for children by comparing with WHO growth standard. Arsenic exposure levels were categorized as <50 μg/L and ≥50 μg/L. Stunting rates (<−2 SD) were 10% at 3 months and 44% at both 6 and 9 months. Wasting rates (<−2 SD) were 23.3% at 3 months and underweight rates (<−2 SD) were 25% and 10% at 3 and 6 months of age, respectively. There was a significant association of stunting with household drinking water arsenic exposure ≥50 μg/L at age of 9 months (p = 0.009). Except for stunting at 9 months of age, we did not find any significant changes in other nutritional indices over time or with levels of household arsenic exposure in this study. Our study suggests no association between household arsenic exposure and under-nutrition during infancy; with limiting factors being small sample size and short follow-up. Difference in stunting at 9 months by arsenic exposure at ≥50 μg/L might be a statistical incongruity. Further longitudinal studies are warranted to establish any association.