Occurrence, transport and sources of metals and metalloids in the Bangpakong River in the eastern economic corridor area of Thailand.

The occurrence of elements in river water is affected by various factors, including mobility, weathering and transport processes and anthropogenic contributions. A total of six water sampling campaigns were conducted from 2021 to 2022 to study the factors affecting the occurrence of twelve elements (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn and Se) in the Bangpakong River. The total concentrations of all the elements were within the levels set by the national surface water quality standard. Comparisons of dissolved elemental concentrations in the study area with the global average for dissolved elemental concentrations in pristine rivers indicated contamination with Al, As, Co, Mn, Zn and Se in the river water. Based on the percentage of each element in particulates to the total concentration, Al (80.6 %), Cr (71.9 %), Cu (69.9 %), Fe (95.6 %), Mn (76.6 %), Pb (74.7 %), and Zn (70.6 %) were mainly transported in the particulate phase in both the dry and wet seasons. However, As (65.5 %), Co (60.3 %), and Se (77.6 %) were mainly transported in the dissolved phase in both seasons. The ratios of the dissolved Se concentration in river water to the Se concentration in the Earth's crust indicated significant and high mobility, especially in downstream sites, likely due to Se leaching from alluvial sediments. Seawater intrusion is likely the cause of As and Zn contamination in the dry season. Weathering of rocks and soils likely causes Al, Co, and Mn contamination in the wet season. The anthropogenic sources of contamination include the discharge of Mn and Zn from fertilizers in agriculture and the use of formulated feed in aquaculture. Approximately 52.98, 25.23, 5.68 and 0.63 tons of Fe, Al, Mn and Zn, respectively, are estimated to be transported from the river into the Gulf of Thailand each year.

Probabilistic assessment of the daily intake of microelements and toxic elements via the consumption of rice with different degrees of polishing.

BACKGROUND: The polishing process plays a key role in determining the beneficial quality of rice. However, the effects of polishing on human exposure to essential and toxic elements are not well reported. This study evaluated the effects of polishing on the levels of essential and toxic elements in rice grains and evaluated the status of their daily intake using probabilistic assessment. RESULTS: The levels of essential elements decreased as the degree of polishing increased. The highest reduction percentages of essential elements [24% of copper (Cu), 26% of nickel (Ni), and 52% of manganese (Mn)] were found after the first polishing step. The highest zinc (Zn) reduction (15%) was found after the fourth polishing step. For toxic elements, polishing significantly reduced the arsenic (As) concentration (15-31%) from that of the whole grains, of which 26% was removed after the first step. CONCLUSION: Polishing removed both essential and toxic elements from rice grains. The highest losses of Cu, Mn, Ni, and As were found after the first polishing step since these elements generally localize in the aleurone layers of rice grains. The last polishing step caused a significant Zn reduction from the grain. Polishing had no significant effect on the cadmium (Cd) concentration in grains. The consumption of all types of rice could not supply sufficient amounts of all microelements except Mn to maintain optimum health. Both As and Cd intake levels were lower than the benchmarks of toxic health effects. Thus, the potential health impacts of both of these elements in rice can be neglected. © 2020 Society of Chemical Industry.

Risk assessment of bioaccessible arsenic and cadmium exposure through rice consumption in local residents of the Mae Tao Sub-district, Northwestern Thailand.

Consumption of contaminated rice is a toxin exposure route in Asian populations. Since total concentrations generally overestimate health risks, the objectives of this study were to determine the levels of bioaccessible As and Cd in rice cultivated in the Mae Tao, Tak Province and evaluate their potential health impacts in local adults. In total, 59 locally grown rice samples were analyzed for their total and bioaccessible concentrations. Bioaccessible concentrations were obtained from an in vitro digestion process. Inorganic As concentrations were estimated assuming that 63.2-63.5% of the total As is inorganic As. Rice contained inorganic As (45.2% of white rice and 57.1% of sticky rice) and Cd (51.6% of white rice and 32.1% of sticky rice) levels exceeding the Codex standards. The bioaccessibilities of As (16.3-70.0%) and Cd (Null to 83.7%) in rice varied widely. The concentrations of bioaccessible As, which were 1-1.2 times greater than those of bioaccessible Cd, indicate a higher possibility of As absorption into the human body. Positive significant relationships were found between total and bioaccessible As (R2 = 0.568 for white rice and R2 = 0.704 for sticky rice) and Cd (R2 = 0.874 for white rice and R2 = 0.862 for sticky rice). The hazard quotient (HQ) of inorganic As exposure accounted for approximately 93.4% of hazard index (HI). Approximately 2-6 in 10,000 residents over a lifetime of 75 years could suffer from cancer as a result of daily rice consumption. Therefore, the consumption of the home-grown rice in this study should be limited.

Analysis and probabilistic risk assessment of bioaccessible arsenic in polished and husked jasmine rice sold in Bangkok.

Food is one of the major sources of arsenic (As) exposure in humans. The objectives of this study were to determine the bioaccessible concentration of As in rice grain sold in Bangkok and to evaluate the potential health risks associated with rice consumption. Polished (n = 32) and husked (n = 17) jasmine rice were collected from local markets. In vitro digestion was performed to determine the bioaccessible As concentrations, which were used for probabilistic health risk assessments in different age groups of the population. Approximately 43.0% and 44.4% of the total As in the grain of polished and husked rice, respectively, was in the form of bioaccessible As. Significantly higher bioaccessible As concentrations were found in husked rice than in polished rice (1.5-3.8 times greater). The concentrations of bioaccessible As in polished and husked rice were lower than the Codex standard for As in rice. The average daily dose of As via rice consumption is equivalent to the daily ingestion of 2 L of water containing approximately 3.2-7.2 µg L-1 of As. Approximately 0.2%-13.7% and 10.7%-55.3% of the population may experience non-carcinogenic effects from polished and husked rice consumption, respectively. Approximately 1%-11.6% of children and 74.1%-99.8% of adults were at risk of cancer. The maximum cancer probabilities were 3 children and 6 adults in 10,000 individuals. The probabilistic risk results indicated that children and adults were at risk of both non-carcinogenic and carcinogenic effects from both types of rice consumption.

Health impact assessment of arsenic and cadmium intake via rice consumption in Bangkok, Thailand.

Consumption of contaminated food is a major route of exposure to toxic contaminants for humans. To protect against potential negative health effects from rice consumption, As and Cd concentrations in rice sold in Bangkok were determined, and non-carcinogenic and carcinogenic risk assessments were conducted. Four types of rice (n = 97), namely, white jasmine, white, glutinous, and brown jasmine, were collected. Samples were acid-digested and analyzed for total concentrations of As and Cd by ICP-MS. The average concentrations of As and Cd were 0.205 ± 0.008 and 0.019 ± 0.001 mg kg-1, respectively. Approximately 22.8, 62.5, and 57.1% of white, white jasmine, and brown jasmine rice, respectively, contained As concentrations exceeding the Codex inorganic As standards for polished and unpolished rice. Brown jasmine rice contained significantly higher As concentrations than the other types of rice. However, Cd concentrations in all rice samples were significantly lower than the Codex standard of 0.4 mg kg-1. Children are exposed to the highest amounts of both elements. Concerning As exposure through the consumption of different types of rice in the same age group, the consumption of brown jasmine rice caused approximately 1.7 to 2.3 times higher As exposure rates compared to the consumption of other types of rice. Non-carcinogenic risks (hazard quotient (HQ)) of As exposure from all types of rice were higher than the threshold limit of 1. HQ in children ranging from 2.1 to 4.9 was significantly higher than HQ in the other age groups. The cancer risks from As exposure were negligible in all groups.