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.

Assessment and source identification of As and Cd contamination in soil and plants in the vicinity of the Nui Phao Mine, Vietnam.

This study investigated the contamination levels and sources of As and Cd vicinity area from Nui Phao mine that is one of the largest tungsten (W) open pit mines in the world. Soil and plant samples were collected from the study area to identify the concentrations of As and Cd using aqua-regia or HNO3 digestion. According to the Vietnamese agricultural soil criteria, all soil samples were contaminated with As and Cd. The distribution of As concentration is related to the distance from the Nui Phao mine. The higher As concentrations were measured in the area close to the mine. However, the Cd distribution in the soil showed a different pattern from As. Enrichment factor and Geoaccumulation Index (Igeo) indicated that As in the soil is derived from the mining activities, while Cd could have other geogenic or anthropogenic sources. The ranges of As and Cd concentration in polished rice grains in the Nui Phao mine area exceeded the CODEX criteria (0.2 mg/kg), which indicated extreme contamination. The arsenic concentration between soil and plant samples was determined to be a positive correlation, while the Cd concentration showed a negative correlation, implying that As and Cd have different geochemical behavior based on their sources.

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.

Human health risk assessment of cadmium exposure through rice consumption in cadmium-contaminated areas of the Mae Tao sub-district, Tak, Thailand.

The Mae Tao sub-district is located in the Mae Tao watershed, an important cadmium (Cd)-contaminated area in Thailand. This study was conducted to (i) determine Cd concentrations in rice collected from households in the area, (ii) assess the Cd exposure and potential health risk (HQ) from rice consumption in local adults and (iii) investigate how the factors of individual characteristics and consumption behavior affect the level of HQ. A total of 159 rice samples were collected from households in all 6 villages of the Mae Tao sub-district for analysis of Cd by inductively coupled plasma mass spectrometry. Biodata information and rice consumption behavior were surveyed from local residents at the same time as rice sample collection. Approximately 19.8% and 19.1% of white rice and sticky rice, respectively, contained total Cd higher than the Codex maximum standard of Cd in rice (0.4 mg kg-1). Locally grown rice contained an average of 1.5 times more Cd than retail rice. Cd exposure from consuming only sticky rice was the highest (2.26 × 10-3 mg kg-1 day-1), followed by the consumption of both types of rice (1.39 × 10-3 mg kg-1 day-1) and the consumption of only white jasmine rice (6.30 × 10-4 mg kg-1 day-1). The highest and lowest average HQ values were found in the only sticky rice consumption pattern (2.263) and the only white rice consumption pattern (0.630), respectively. The potential health risk from Cd in each rice consumption pattern was mainly influenced by the total Cd concentration in rice and the rice ingestion rate.

Arsenic health risk assessment related to rice consumption behaviors in adults living in Northern Thailand.

The rice consumption behaviors of Thai citizens vary among regions. However, the influence of different consumption patterns on arsenic (As) exposure has never been reported. This study was conducted to investigate the effects of rice consumption behavior on As exposure levels. White rice (n = 96) and sticky rice (n = 63) samples were collected from local households in northern Thailand. The actual rice consumption behavior (type, frequency, and amount of rice consumed) was surveyed from the households where the rice samples were collected and used to calculate individual As exposures. The white rice (2.1%) and sticky rice (6.3%) samples contained inorganic As at higher concentrations than the Codex standard (0.2 mg kg-1). Approximately 58.3% of participants consumed white rice for breakfast and sticky rice for lunch and dinner, while 41.8% of participants consumed only white rice or sticky rice daily. Wide variations of As exposure (1 × 10-4 to 2 × 10-3 mg kg-1 day-1) were found. The average As exposure from only sticky rice consumption and combined rice consumption was 2 times higher than the As exposure from only white rice consumption. The rice ingestion rate was the most important factor affecting the level of As exposure resulting from the white rice-only and combined rice consumption patterns. For the combined rice consumption pattern, 45.7 to 93.5% of the total As exposure was from sticky rice consumption. Regarding individual characteristics, older and lower weight participants tended to consume lower amounts of rice. Thus, lower As exposure and fewer health impacts were found in those participants.

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.

Assessment of metal and bacterial contamination in cultivated fish and impact on human health for residents living in the Mekong Delta.

Fish is the main source of animal protein and micronutrients for inhabitants in the lower Mekong River basin. Consumption of fish in the basin ranges from 41 to 51 kg capita(-1) year(-1). Thus, concerns of human health impacts caused by daily intake of metals contained in fish, and the incidence of bacterial contamination from Listeria and Escherichia coli have been raised. This study was conducted to 1) determine concentrations of metals, fecal indicator organisms, and Listeria spp. in cultivated common diet fish, and 2) assess human health risks as results of fish consumption on a daily basis. The results showed significant impacts of metal accumulation in fish especially from the intensive aquaculture. Chemical use to promote the rapid allometric growth of fish was expected to be the explanation for this finding. Concentrations of metals contained in different fish species were not statistically different with the exceptions of Na, Mn, and Zn. This might be due to the mobility of elements in aquaculture farms. Listeria and E. coli log CFU/g were 1.36 ± 0.11 (standard error) and 1.57 ± 0.1 s.e., respectively with higher counts observed in samples collected in market sites. Lastly, for human health risk assessment via fish consumption, it was found that hazard quotients of consuming As, Cu, and Zn contained in all fish species could contribute adverse health effects to the local residents (hazard quotients higher than 1). Therefore, risk management measures must be promoted and implemented in all study areas to reduce potential risks to local Vietnamese residents.

Human health risk assessment for ingestion exposure to groundwater contaminated by naturally occurring mixtures of toxic heavy metals in the Lao PDR.

This study constitutes the first systematic risk assessment in the Lao PDR of the safety of groundwater for consumption. Groundwater and hair samples were collected from seven Lao provinces to determine the quantitative health impact of heavy metals through ingestion exposure. Contamination levels for arsenic (As; 46.0 %) and barium (Ba; 16.2 %) exceeded World Health Organization (WHO) guidelines, especially in Mekong River floodplains. A USEPA assessment model for health risks from daily groundwater ingestion, with adjustments for local water consumption values, was applied to estimate the size of the population at risk for noncarcinogenic and carcinogenic health problems. As was the only element contributing to noncarcinogenic health risks in all contaminated areas. The populations of Bolikhamxai, Savannakhet, Saravane, Champasak, and Attapeu, moreover, were at risks of cancer. In addition to the As groundwater concentration factor, noncarcinogenic and carcinogenic risks were positively correlated with the average daily dose of As, exposure duration, and subject body weight. The level of As in hair correlated with groundwater consumption and average daily dose of As. 25.5 % of the population (n = 228) showed As levels in hair above the toxicity level.