Rice and vegetables primarily contain inorganic arsenic, followed by DMA and MMA, in samples collected from arsenic-contaminated fields

Uttam K. Chowdhury

Published Date: Apr - 17 - 2025

In this study, tubewell water, soil, crops, and vegetables were collected from agricultural fields irrigated with arsenic-contaminated water. The total arsenic content in the water and soil samples was estimated using FI-HG-AAS. The results showed that arsenic concentrations in the soil increased with the rising arsenic levels in the irrigation water.

Arsenic speciation in paddy (rice and husk), rice, husk, and vegetables were analyzed by IC-ICP-MS following TFA extraction. The results indicated that inorganic arsenic (Inorg-As) was the dominant species in rice, paddy, and vegetables. On average, arsenic species in rice samples (n = 2) comprised 91% Inorg-As, 9% DMA, and very little MMA was measured. All four husk samples contained only inorganic arsenic, with no detectable levels of DMA or MMA. In contrast, the arsenic speciation in a paddy (rice + husk) sample revealed 76.46% Inorg-As, 19.31% DMA, and 4.23% MMA.

In a sample of lady's finger, both Inorg-As (82%) and DMA (17%) were detected, with MMA present in very little amounts. A notably high arsenic concentration was found in a vegetable called “Kachu,” which grows underground and is a popular food in West Bengal, India, and Bangladesh. Interestingly, “Kachu” contained a very high concentration of Inorg-As but no detectable levels of DMA or MMA. But the possible presence of an unknown arsenic species.

Overall analysis of rice and vegetable samples indicates that 95% and 5% of the arsenic in rice is inorganic and methylated, respectively, while 96% and 4% of the arsenic in vegetables is inorganic and methylated, respectively.

Arsenic Metabolism Process and Its Toxicity in Animals

Hiroshi Tokunaga, Uttam K. Chowdhury

Published Date: May - 03 - 2025

Arsenic, a known Group 1 human carcinogen, undergoes biotransformation through methylation, resulting in metabolites such as monomethylarsonate (MMA) and dimethylarsinate (DMA). While traditionally considered less toxic, recent studies suggest that certain methylated arsenic species may retain or even enhance toxicity. This paper synthesizes current knowledge on arsenic metabolism and its toxicity in domestic animals, with comparative insights across species including cows, goats, mice, rats, and chimpanzees. Cows and goats exhibit significant arsenic methylation capacities, with urinary arsenic profiles dominated by DMA, paralleling human metabolic patterns. Methylation efficiency in cows increases with age, and evidence supports placental transfer of arsenic to offspring. In mice, arsenic metabolism is influenced by the valence state, dose, and exposure route, with higher methylation observed for arsenite than arsenate. Rats display lower methylation efficiency than mice, and chimpanzees uniquely lack the ability to methylate arsenic. Toxic effects of arsenic range from acute gastrointestinal symptoms to chronic organ damage, with younger animals being particularly vulnerable. These findings underscore the need for a better understanding of species-specific arsenic metabolism and its implications for animal and human health.

Distribution of arsenic in different parts of paddy and vegetables collected from arsenic-contaminated fields

Masanori Ando, Hiroshi Tokunaga, Uttam K. Chowdhury, Dipankar Chakraborti

Published Date: May - 17 - 2025

In this study, tubewell water, soil, crops, and vegetables were collected from agricultural fields irrigated with arsenic-contaminated water. The total arsenic content in different parts of vegetables (stem, leaf, and fruit) and paddy (rice and husk) samples was estimated using FI-HG-AAS and ICP-MS after dry ashing and microwave digestion, respectively. A strong correlation was observed between arsenic concentrations in irrigated groundwater and soil. Arsenic concentrations were higher at the surface of soil, with minimal variation at greater depths. The results showed that the average arsenic concentrations in contaminated soil, rice, and vegetables were 3.81, 3.62, and 5.66 times higher, respectively, than those in control samples. Overall, the findings indicate that arsenic concentrations in paddies and vegetables increase with higher arsenic levels in soil. In paddy, arsenic concentrations decreased in the order: shoot > seed (rice) > husk; in vegetables, the order was: leaf > stem > fruit.

Arsenic-Free and Contaminated Groundwater Status in Four Geomorphological Areas of Bangladesh

Dipankar Chakraborti, Uttam K. Chowdhury

Published Date: May - 23 - 2025

From our preliminary survey, 33,092 hand tubewell water samples collected from all 64 districts and found arsenic in 60 districts above WHO recommended valve in drinking water (10 µg/L) and in 50 districts above maximum permissible limit, 50 µg/L. In these 50 districts the actual arsenic status is, 37% contains less than 10 µg/L, 63% and 42% contains above 10 µg/L and 50 µg/L, respectively. From our study, it appears that the groundwater of Hill Tract and Tableland are almost free from arsenic contamination but Flood Plain and Deltaic areas are highly arsenic contaminated. Finally, we expect Bangladesh may have arsenic in groundwater below 50 µg/L at depths above 350 meters. However, success will depend on aquifer composition as well as design, construction, and development of tubewells.

Arsenic and Other Trace Elements in Soil, Rice, and Vegetables Grown in Fields Irrigated with Arsenic-Contaminated Water

Uttam K. Chowdhury

Published Date: May - 28 - 2025

In this study, tubewell water, soil, crops, and vegetables were collected from agricultural fields irrigated with arsenic-contaminated water. The total arsenic and other trace element contents in vegetables, rice, and paddy (rice and husk) samples were estimated using ICP-MS after dry ashing or microwave digestion. In soil samples, regression analysis was performed to examine the relationship between arsenic and other metals. No significant correlations were observed between As & Mn, As & Cu, As & Ni, and As & Pb. However, a significant positive correlation was found between As & Zn (r = +0.763, p = 0.027), and a strong negative correlation was observed between As & Hg (r = -0.802, p = 0.009). The trace elements in soil from the experimental fields (n = 6) were ranked in decreasing order as follows: Mn > Zn > Ni > Pb > Cu > As > Hg.

In rice, arsenic along with Se, Mn, Cu, Hg, Pb, and Ni were analyzed in the rice and husk of three paddy samples cultivated with arsenic-contaminated water. Regression analysis showed a negative correlation between As & Se (r = -0.999, p = 0.018), As & Pb (r = -0.992, p = 0.078), and a positive correlation between As & Cu (r = +0.998, p = 0.03). No significant correlations were found between As & Mn, As & Hg, and As & Ni. An interesting observation was that selenium concentration decreased as arsenic concentration increased in both rice and husk. The decreasing order of elements in rice from arsenic-contaminated fields was Mn > Cu > Ni > Se > As > Hg > Pb.

In vegetables, similar trends were observed in two samples studied. All analyzed elements (Se, Mn, Cu, Hg, Pb, and Ni) were present in lower concentrations (ng/g) in Kachu (taro, a tropical starchy tuberous root) compared to Data (stem amaranth), except for arsenic. Arsenic was significantly higher in Kachu than in Data, despite both being irrigated with the same arsenic-contaminated water (205 µg/L). The trace elements were ranked in decreasing order as Mn > Cu > Ni > Hg > Se, except for As and Pb. In contrast, As was significantly higher and Pb significantly lower in Kachu compared to Data.