PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “ARSENICALS”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed2002

[Correlation of arsenic accumulative intake and its health effects to the residents in arsenic polluted area. Estimation of arsenic accumulative intake level of residents living in arsenic polluted area].

In order to evaluate arsenic accumulative intake level of residents living in an area with arsenic pollution in the air, the level of arsenic accumulative intake is measured by calculating residents' accumulative rice consumption and the measurement of the level via inhalation. The results show that ignoring the non-polluted time periods, the highest arsenic accumulative intake level (AAIL) appears in residents aged 50 and above who have the highest level of air inhalation and rice consumption in comparison with young residents after 32 years exposure, and their AAIL detected via inhalation are 591.4 mg for female and 612.9 for male respectively. There is 3488.74 mg arsenic obtained by their daily diet. Total AAIL are 4080.14 mg for female and 4101.66 mg for male respectively, being about 80% of estimation level reflected by daily exposure level multiplied by total exposure time (day).

Adolescent↗
PubMed1989

Biological monitoring of arsenic exposure of gallium arsenide- and inorganic arsenic-exposed workers by determination of inorganic arsenic and its metabolites in urine and hair.

In an attempt to establish a method for biological monitoring of inorganic arsenic exposure, the chemical species of arsenic were measured in the urine and hair of gallium arsenide (GaAs) plant and copper smelter workers. Determination of urinary inorganic arsenic concentration proved sensitive enough to monitor the low-level inorganic arsenic exposure of the GaAs plant workers. The urinary inorganic arsenic concentration in the copper smelter workers was far higher than that of a control group and was associated with high urinary concentrations of the inorganic arsenic metabolites, methylarsonic acid (MAA) and dimethylarsinic acid (DMAA). The results established a method for exposure level-dependent biological monitoring of inorganic arsenic exposure. Low-level exposures could be monitored only by determining urinary inorganic arsenic concentration. High-level exposures clearly produced an increased urinary inorganic arsenic concentration, with an increased sum of urinary concentrations of inorganic arsenic and its metabolites (inorganic arsenic + MAA + DMAA). The determination of urinary arsenobetaine proved to determine specifically the seafood-derived arsenic, allowing this arsenic to be distinguished clearly from the arsenic from occupational exposure. Monitoring arsenic exposure by determining the arsenic in the hair appeared to be of value only when used for environmental monitoring of arsenic contamination rather than for biological monitoring.

Arsenic↗
PubMed2002

Arsenic species in an arsenic hyperaccumulating fern, Pityrogramma calomelanos: a potential phytoremediator of arsenic-contaminated soils.

The fern Pityrogramma calomelanos is a hyperaccumulator of arsenic that grows readily on arsenic-contaminated soils in the Ron Phibun district of southern Thailand. P. calomelanos accumulates arsenic mostly in the fronds (up to 8350 microg As g(-1) dry mass) while the rhizoids contain the lowest concentrations of arsenic (88-310 microg As g(-1) dry mass). The arsenic species in aqueous extracts of the fern and soil were determined by high performance liquid chromatography coupled to an inductively coupled plasma mass spectrometer (HPLC-ICPMS) which served as an arsenic specific detector. Only a small part of the arsenic (6.1-12%) in soil was extracted into water, and most of this arsenic (> 97%) was present as arsenate. The arsenic in the fern rhizoids was approximately 60% water-extractable, 95% of which was present as arsenate. In contrast, arsenic in the fern fronds was readily extracted into water (86-93%) and was present mainly as arsenite (60-72%) with the remainder being arsenate. Methylarsonate and dimethylarsinate were detected as trace constituents in only two fern samples. Preliminary estimates of phytoremediation potential suggest that P. calomelanos might remove approximately 2% of the soil arsenic load per year. With due consideration to the type of arsenic compounds present in the fern, and their water-solubility, the option of disposing high arsenic ferns at sea is raised for discussion.

Arsenic↗
PubMed1995

Arsenic in ground water in six districts of West bengal, India: the biggest arsenic calamity in the world. Part 2. Arsenic concentration in drinking water, hair, nails, urine, skin-scale and liver tissue (biopsy) of the affected people.

In six districts of West Bengal arsenic has been found in ground water above the maximum permissible limit recommended by the WHO of 0.05 mg l-1. This water is used by the villagers for drinking, cooking and other household purposes. These six districts have an area of 34,000 km2 and hold a population of 30 million. Over the last five years we have surveyed only a few small areas of these six affected districts and our survey revealed that, at present, at least 800,000 people from 312 villages in 37 blocks are drinking contaminated water and more than 175,000 people are showing arsenical skin lesions that are the late stages of manifestation of arsenic toxicity. Most of the three stages of arsenic-related clinical manifestations are observed amongst the affected people. The common symptoms are conjunctivitis, melanosis, depigmentation, keratosis and hyperkeratosis; cases of gangrene and malignant neoplasms are also observed. The source of arsenic is geological. We have analysed thousands of arsenic contaminated water samples. Most of the water samples contain a mixture of arsenite and arsenate and in none of them could we detect methylarsonic or dimethylarsenic acid. We have also analysed a large number of urine, hair and nail samples, several skin-scales and some liver tissues (biopsy samples) of the people drinking the arsenic contaminated water and showing arsenical skin lesions. Flow injection hydride generation atomic absorption spectrometry (FI-HGAAS) was used for the analysis of hair, nails, urine and skin-scale after decomposition by various techniques. The liver tissues were analysed by Zeeman corrected-ETAAS using a few milligrams of the biopsy samples.

Adolescent↗
PubMed1977

[Studies on arsenic metabolism (XX). Arsenic accumulation in the organs and excretion into the feces and urine of rats chronically poisoned with arsenic (author's transl)].

Male and female rats (60 approximately 80 g) of Wistar strain were randomly divided into two groups and were given milk and cereal diets, respectively. Each group was further divided into two groups; one was given the diet containing 100ppm of arsenic trioxide and the other a diet containing "arsenic compound" (100ppm as arsenic trioxide). Each group included five rats of both sexes. A 6-month feeding of the test diet was followed by provision of a normal diet. The accumulated arsenic was excreted almost 100% from the brain and 20 approximately 30% from organs such as kidney, liver, spleen and lung. The arsenic level persisted in tissues in animals on the cereal diet, as compared with those fed the milk diet. There was no significant difference in the accumulation and excretion of arsenic between the groups given arsenic trioxide or "arsenic compound".

Animals↗
PubMed2002

[Estimation of arsenic accumulative intake and residents' health effects in an air pollution area--relationship between arsenic accumulative intake level and arsenicism prevalence].

This paper reports the results of epidemiological survey on health effects of residents exposed to arsenic in a pollution area and estimation of arsenic accumulative intake level (EAAIL) based on calculating accumulative rice consumption and via inhalation way. 795 persons were sampled randomly from the polluted area, among whom 674 persons and 83 persons were diagnosed with Chronic Arsenic Absorption (CAA) and Chronic Arsenicism (CA) according to the National Diagnose Standard respectively. There were 60.98% CAA in 30 years old and younger age-groups and 97.59% CA in 30 years old and older age-groups. The one youngest case of CA occurred in 15 years old age group, while its EAAIL was at 1846.47 mg. The highest EAAIL was at 8706.47 mg. The rate of CA had gone obviously up at 30 years old age group. Its EAAIL was at 3833.42 mg. One equation of relationship between the rate of CA (%) and EAAIL (mg) was fitted by means of curve fitting, its is followed: Y = X1.843/e12.694 -2.866, r2 = 0.945.

Adolescent↗
PubMed2003

Comparison of arsenic(V) and arsenic(III) sorption onto iron oxide minerals: implications for arsenic mobility.

Arsenic derived from natural sources occurs in groundwater in many countries, affecting the health of millions of people. The combined effects of As(V) reduction and diagenesis of iron oxide minerals on arsenic mobility are investigated in this study by comparing As(V) and As(III) sorption onto amorphous iron oxide (HFO), goethite, and magnetite at varying solution compositions. Experimental data are modeled with a diffuse double layer surface complexation model, and the extracted model parameters are used to examine the consistency of our results with those previously reported. Sorption of As(V) onto HFO and goethite is more favorable than that of As(III) below pH 5-6, whereas, above pH 7-8, As(II) has a higher affinity for the solids. The pH at which As(V) and As(III) are equally sorbed depends on the solid-to-solution ratio and type and specific surface area of the minerals and is shifted to lower pH values in the presence of phosphate, which competes for sorption sites. The sorption data indicate that, under most of the chemical conditions investigated in this study, reduction of As(V) in the presence of HFO or goethite would have only minor effects on or even decrease its mobility in the environment at near-neutral pH conditions. As(V) and As(III) sorption isotherms indicate similar surface site densities on the three oxides. Intrinsic surface complexation constants for As(V) are higher for goethite than HFO, whereas As(III) binding is similar for both of these oxides and also for magnetite. However, decrease in specific surface area and hence sorption site density that accompanies transformation of amorphous iron oxides to more crystalline phases could increase arsenic mobility.

Adsorption↗
PubMed2004

[Arsenic absorption and retention in acute promyelocytic leukemia patients treated with tetra-arsenic tetra-sulfide].

The objective of this study was to investigate arsenic absorption and retention in acute promyelocytic leukemia (APL) patients treated with tetra-arsenic tetra-sulfide (As(4)S(4)). Arsenic concentrations in samples from APL patients were quantitatively determinated by Hydride Generation Atomic Absorption Spectrometry. The results showed that blood arsenic level was 51.7 +/- 18.7 microg/L (n = 41), urine arsenic level was 2359.1 +/- 1910.6 microg/L (n = 36), and the average daily urinary arsenic excretion was 5.1 +/- 4.06 mg/day (n = 32) on the 7th-9th day after As(4)S(4) administration; blood arsenic level was 61.7 +/- 22.7 microg/L (n = 30), urine arsenic level was 2834.0 +/- 1958.3 microg/L (n = 27), the average daily urinary arsenic excretion was 6.3 +/- 4.98 mg/day (n = 24) on the 10th-12th day after As(4)S(4) administration; blood arsenic level was 62.8 +/- 25.1 microg/L (n = 34), urine arsenic level was 2859.3 +/- 2298.2 microg/L (n = 32) and the average daily urinary arsenic excretion was 6.82 +/- 5.58 mg/day (n = 32) on the 13th-15th day after As(4)S(4) administration. Blood arsenic level was 20.7 +/- 10.9 microg/L (n = 31), urine arsenic level was 525.5 +/- 337.1 microg/L (n = 28), and the average daily urinary arsenic excretion was 1.76 +/- 1.3 mg/day (n = 17) on the 7th-9th day after stop of treatment; blood arsenic level was 16.1 +/- 10.1 microg/L (n = 34), urine arsenic level was 207.1 +/- 164.5 microg/L (n = 28) and the average daily urinary arsenic excretion was 0.42 +/- 0.27 mg/day (n = 22) on the 13th-15th day after stop of treatment. Blood arsenic concentration, urine arsenic concentration and daily urinary arsenic excretion reach a steady state after treatment with As(4)S(4) for 10 days. The average urinary arsenic excretion was 6.82 +/- 5.58 mg/day (n = 32), arsenic absorption level was 9.74 +/- 7.97 mg/day and arsenic absorption efficiency was 0.25 +/- 0.20% during treatment. In conclusion, the majority of absorbed arsenic was excreted from urine and other ways, only a small part of absorbed arsenic was retained in body at the 14th day after therapy was discontinued, blood arsenic concentration, urine arsenic concentration, daily urinary arsenic excretion and hair arsenic concentration could be considered as useful biomarkers for monitoring arsenic absorption and retention in APL patients treated with As(4)S(4).

Absorption↗
PubMed2000

Calibrationless flow-through stripping coulometric determination of arsenic (III) and total arsenic in contaminated water samples after microwave assisted reduction of arsenic(V).

A simple and rapid procedure for the calibrationless determination of trace concentrations of As(III) and total As in contaminated water samples is presented. Arsenic is preconcentrated as As(III) in a flow-through cell with a gold plated porous electrode and is then stripped anodically by a constant current. The stripping chronopotentiogram is registered and evaluated. The As concentration is calculated directly from the combined Faraday's laws. The total As content was determined after converting all As species to As(III) by microwave-assisted reduction with hydrazine hydrochloride in a closed vessel. The detection limit was found to be 0.15 microg/L and the linear response range was 0.5 to 10,000 microg/L. Tap water, surface water, and waste water samples were analyzed.

Arsenic↗
PubMed2004

Phytofiltration of arsenic from drinking water using arsenic-hyperaccumulating ferns.

Arsenic contamination of drinking water poses serious health risks to millions of people worldwide. Current technologies used to clean arsenic-contaminated water have significant drawbacks, such as high cost and generation of large volumes of toxic waste. In this study, we investigated the potential of using recently identified arsenic-hyperaccumulating ferns to remove arsenic from drinking water. Hydroponically cultivated, two arsenic-hyperaccumulating fern species (Pteris vittata and Pteris cretica cv. Mayii) and a nonaccumulating fern species (Nephrolepis exaltata) were suspended in water containing 73As-labeled arsenic with initial arsenic concentrations ranging from 20 to 500 microg L(-1). The efficiency of arsenic phytofiltration by these fern species was determined by continuously monitoring the depletion of 73As-labeled arsenic concentration in the water. With an initial water arsenic concentration of 200 microg L(-1), P. vittata reduced the arsenic concentration by 98.6% to 2.8 microg L(-1) in 24 h. When the initial water arsenic was 20 microg L(-1), P. vittata reduced the arsenic concentration to 7.2 microg L(-1) in 6 h and to 0.4 microg L(-1) in 24 h. At similar plant ages, both P. vittata and P. cretica had similar arsenic phytofiltration efficiency and were able to rapidly remove arsenic from water to achieve arsenic levels below the new drinking water limit of 10 microg L(-1). However, N. exaltata failed to reduce water arsenic to achieve the limit under the same experimental conditions. The significantly higher efficiency of arsenic phytofiltration by arsenic-hyperaccumulating fern species is associated with their ability to rapidly translocate absorbed arsenic from roots to shoots. The nonaccumulating fern N. exaltata was unable to translocate the absorbed arsenic to the shoots. Our results demonstrate that the arsenic-phytofiltration technique may provide the basis for a solar-powered hydroponic technique that enables small-scale cleanup of arsenic-contaminated drinking water.

Absorption↗
PubMed1998

Low-level arsenic excretion in breast milk of native Andean women exposed to high levels of arsenic in the drinking water.

OBJECTIVE: To investigate the excretion of arsenic in breast milk of lactating native Andean women living in a village in northwestern Argentina with high concentrations of arsenic in the drinking water (about 200 micrograms/l) and to assess the exposure of children to arsenic during the very first period of life. METHODS: The study included ten lactating women and two nursing babies. Hydride-generation atomic absorption spectrometry (HG-AAS) was used to determine the concentration of arsenic in samples of human milk, drinking water, blood, and urine. RESULTS: The concentrations of arsenic detected in maternal blood (total arsenic) and urine (metabolites of inorganic arsenic) were high, averaging 10 and 320 micrograms/l, respectively. In subjects without known exposure to arsenic the average concentrations found in blood and urine are 1-2 and about 10 micrograms/l, respectively. The metabolites of inorganic arsenic constituted more than 80% of the total arsenic in the urine, which shows that inorganic arsenic was the main form of arsenic ingested. The average concentration of arsenic detected in human milk was 2.3 micrograms/kg fresh weight (range 0.83-7.6 micrograms/kg). Although data on background levels of arsenic in human breast milk are scarce, the present concentrations seem to be slightly elevated. However, considering the high levels of arsenic exposure in the mothers, the total arsenic concentrations measured in human milk were low. In concordance with the low concentrations of arsenic found in the milk, the concentrations of arsenic metabolites measured in the urine of two of the nursing babies were low: 17 and 47 micrograms/l, respectively. CONCLUSIONS: The low concentrations of arsenic detected in the breast milk and urine of the two nursing babies in relation to the high level of maternal exposure to arsenic indicate that inorganic arsenic is not excreted in breast milk to any significant extent. This is a very important reason for long breast-feeding periods.

Adolescent↗
PubMed2004

Absorption of foliar-applied arsenic by the arsenic hyperaccumulating fern (Pteris vittata L.).

The fact that heavy metals can enter various domains of the plant system through foliar pathways spurred us to explore if the fronds of the Chinese brake fern (Pteris vittata L.), a hyperaccumulator of arsenic, a carcinogenic metalloid, was proficient in absorbing arsenic in the form of sprays. The specific objective of this study was to investigate the impact of frond age, form of arsenic, and time of application on the absorption of foliar-applied arsenic by the brake fern; also examined were the effects of foliar sprays on surface ultrastructure and arsenic speciation in the frond following absorption. Foliar sprays of different arsenic concentrations (0, 50, 100, 200, and 400 ppm) were applied to young and fertile fronds. A positive linear relationship existed between arsenic concentration and absorption; the arsenic concentration of fronds increased from 50 to 200 ppm. Time-course analysis with excised pinnae indicated an initial linear increase followed by a plateau at 48 h. The young fronds with immature sori absorbed more arsenic (3100 ppm) than the fertile mature fronds (890 ppm). In the frond, the arsenic absorption was greatest in the lamina of the pinnae followed by the sori and the rachis. Applying arsenic during night (20:00-22:00 h) or afternoon (12:00-14:00 h) resulted in greater absorption of arsenic than the application in the morning (08:00-10:00 h). The arsenic absorption was greater through abaxial surfaces than through adaxial surfaces. The brake fern absorbed more arsenic when it was applied in the form of arsenite. Regardless of the form of arsenic and the surface it was applied to, arsenic occurred as arsenite, the reduced and the most toxic form of arsenic, after having been absorbed by the fronds. Scanning electron microscopy revealed no surface morphological alterations following all arsenic sprays. The study unequivocally illustrated that the Chinese brake fern absorbed foliar-applied arsenic with great efficiency. Consequently, the arsenic concentrations in the fronds transcended the levels of hyperaccumulation; such a characteristic could be exploited in the phytoremediation of groundwater contaminated with arsenic.

Absorption↗
PubMed1997

Arsenic methylation capacity, body retention, and null genotypes of glutathione S-transferase M1 and T1 among current arsenic-exposed residents in Taiwan.

In order to elucidate the relationships among arsenic methylation capacity, body retention, and genetic polymorphisms of glutathione S-transferase (GST) M1 and T1, a total of 115 study subjects were recruited from Lanyang Basin located on the northeast coast of Taiwan. Specimens of drinking water, blood, urine, hair and toenail were collected from each study subject. Urinary inorganic and methylated arsenic were speciated by high performance liquid chromatography combined with hydride-generation atomic absorption spectrometry. Arsenic concentration in hair and toenail were quantitated by atomic absorption spectrophotometry. The polymerase chain reaction was used to determine genetic polymorphisms of GST M1 and T1. Arsenic concentrations in urine, hair, and toenail of study subjects were positively correlated with arsenic levels in their drinking water. Percentages of various arsenic species in urine (mean +/- standard error (SE) were 11.8 +/- 1.0, 26.9 +/- 1.2 and 61.3 +/- 1.4, respectively, for inorganic arsenic, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). Men and women had similar arsenic methylation capability. No associations were observed between arsenic methylation capability and arsenic content in either drinking water or urine. Ratios of arsenic contents in hair and toenail to urinary arsenic content (mean +/- standard error) were 6.2 +/- 0.7 and 16.5 +/- 1.7, respectively. Genetic polymorphisms of GST M1 and T1 were significantly associated with arsenic methylation. Subjects having the null genotype of GST M1 had an increased percentage of inorganic arsenic in urine, while those with null genotype of GST T1 had an elevated percentage of DMA in urine. Arsenic contents in hair and toenail were significantly correlated with the increase in arsenic concentrations of drinking water and urine, while no significant associations were observed between arsenic contents in hair and toenail and polymorphisms of GST M1 and T1. The relationship between arsenic methylation capability and body retention was modified by genetic polymorphisms of GST M1 and T1. Arsenic contents in hair and toenail were negatively associated with MMA percentage and positively associated with DMA percentage among subjects having null genotypes of GST M1 and T1, but not among those with non-null genotypes.

Arsenic↗
PubMed2003

Arsenic groundwater contamination and sufferings of people in North 24-Parganas, one of the nine arsenic affected districts of West Bengal, India.

To understand the magnitude of the arsenic calamity in West Bengal, a detailed study spanning 7 years was made in North 24-Parganas, one of the nine arsenic affected districts. Area and population of North 24-Parganas district are 4093.82 sq. km and 7.3 million, respectively. Fourty eight thousand and thirty water samples were analyzed from hand tubewells of North 24-Parganas in use for drinking, cooking and 29.2% of the tubewells were found to have arsenic above 50 microg/L, the maximum permissible limit of World Health Organization (WHO) and 52.8% have arsenic above 10 microg/L, WHO recommended value of arsenic in drinking water. Out of the 22 blocks of North 24-Parganas, in 20 blocks arsenic has been found above the maximum permissible limit and so far in 16 blocks people have been identified as suffering from arsenical skin lesions. From the generated data, it is estimated that about 2.0 million and 1.0 million people are drinking arsenic contaminated water above 10 microg/L and 50 microg/L level, respectively in North 24-Parganas alone. So far, in our preliminary study 33,000 people have been examined at random from arsenic affected villages in North 24-Parganas and 2274 people have been registered with arsenical skin lesions. Extrapolation of the available data indicates about 0.1 million people may be suffering from arsenical skin lesions from North 24-Parganas alone. A sum of 21,000 hair, nail, and urine samples analyses from arsenic affected villages show 56%, 80%, and 87% people have arsenic in biological specimen more than normal/toxic (hair) level, respectively. Thus, many may be subclinically affected. Due to use of arsenic contaminated groundwater for agricultural irrigation, rice and vegetable are getting arsenic contaminated. Hence there is an additional arsenic burden from food chain. People from arsenic affected villages are also suffering from arsenical neuropathy. A followup study indicates that many of the victims suffering from severe arsenical skin lesions for several years are now suffering from cancer or have already died of cancer.

Adult↗
PubMed2004

Arsenic speciation in urine from acute promyelocytic leukemia patients undergoing arsenic trioxide treatment.

Arsenic has been used successfully in clinical trials for treating acute promyelocytic leukemia (APL). Although sublethal doses of inorganic arsenic are used, little is known about the pharmacokinetics and metabolism of the high levels of arsenic in APL patients. To fill this important gap, this study describes the speciation of arsenic in urine from four APL patients treated with arsenic. Each patient was injected daily with an arsenite (As(III)) solution that contained 10 mg of As(2)O(3) precursor. Speciation analysis of the patient urine samples collected consecutively for 48 h, encompassing two intravenous injections of arsenic, revealed the presence of monomethylarsonous acid (MMA(III)), dimethylarsinous acid (DMA(III)), monomethylarsonic acid (MMA(V)), and dimethylarsinic acid (DMA(V)). The intermediate methyl arsenic metabolites, MMA(III) and DMA(III), were detected in most urine samples from all of the patients when a preservative, diethyldithiocarbomate, was added to the urine samples to stabilize these trivalent arsenic species. The major arsenic species detected in the urine samples from the patients were As(III), MMA(V), and DMA(V), accounting for >95% of the total arsenic excreted. The relative proportions of As(III), As(V), MMA(V), and DMA(V) in urine samples collected 24 h after the injections of As(III) were 27.6 +/- 6.1, 2.8 +/- 2.0, 22.8 +/- 8.1, and 43.7 +/- 13.3%, respectively. The relatively lower fraction of the methylated arsenic species in these APL patients under arsenic treatment as compared with that from the general population exposed to much lower levels of arsenic suggests that the high levels of As(III) inhibit the methylation of arsenic (inhibits the formation of methyl arsenic metabolites). The arsenic species excreted into the urine accounted for 32-65% of the total arsenic injected. These results suggest that other pathways of excretion, such as through the bile, may play an important role in eliminating (removing) arsenic from the human body when challenged by high levels of As(III).

Adult↗
PubMed2003

Arsenic contamination of Bangladesh paddy field soils: implications for rice contribution to arsenic consumption.

Arsenic contaminated groundwater is used extensively in Bangladesh to irrigate the staple food of the region, paddy rice (Oryza sativa L.). To determine if this irrigation has led to a buildup of arsenic levels in paddy fields, and the consequences for arsenic exposure through rice ingestion, a survey of arsenic levels in paddy soils and rice grain was undertaken. Survey of paddy soils throughout Bangladesh showed that arsenic levels were elevated in zones where arsenic in groundwater used for irrigation was high, and where these tube-wells have been in operation for the longest period of time. Regression of soil arsenic levels with tube-well age was significant. Arsenic levels reached 46 microg g(-1) dry weight in the most affected zone, compared to levels below l0 microg g(-1) in areas with low levels of arsenic in the groundwater. Arsenic levels in rice grain from an area of Bangladesh with low levels of arsenic in groundwaters and in paddy soils showed that levels were typical of other regions of the world. Modeling determined, even these typical grain arsenic levels contributed considerably to arsenic ingestion when drinking water contained the elevated quantity of 0.1 mg L(-1). Arsenic levels in rice can be further elevated in rice growing on arsenic contaminated soils, potentially greatly increasing arsenic exposure of the Bangladesh population. Rice grain grown in the regions where arsenic is building up in the soil had high arsenic concentrations, with three rice grain samples having levels above 1.7 microg g(-1).

Agriculture↗