Main Controlling Factors and Empirical Models for Total Mercury and Methylmercury Accumulation in Rice (Oryza Sativa L.)

It has been reported that rice consumption is the main mercury (Hg) exposure pathway for humans, and soil properties could significantly affect the methylation and accumulation process of Hg in soil-rice system. In this study, 19 paddy soil with various properties were spiked with exogenous Hg(II) at three concentration levels to conduct a pot experiment after a 60-days aging period. Stepwise multiple linear regression was applied to determine the controlling soil factors and develop prediction models for the methylmercury (MeHg) concentration in soil and total Hg (THg) and MeHg in brown rice. The results showed that THg in brown rice was positively correlated with THg in soil, while it had a negative correlation with soil pH and clay content. Soil organic matter (OM) promoted Hg methylation and inhibited the accumulation of MeHg in brown rice. Soil pH and clay content were negative factors when soil MeHg was used to predict MeHg in brown rice. THg and MeHg in brown rice could be well predicted by soil THg, pH and clay content. These results may provide a theoretical basis for safe production of rice in Hg contaminated paddy field.

Heavy Metal Contamination and Human Health Implications in the Chan Thnal Reservoir, Cambodia

Chan Thnal reservoir, built during the Pol Pot period, is the major water source for the people in Krang Chek commune, Kampong Speu Province, Cambodia. Metal pollution caused by agricultural activities, improper wastewater treatment, and municipal waste disposal poses serious environmental health problems. In this study, the concentrations of four potential toxic metals (i.e., Cd, Cu, Pb, and Zn) from six locations across the reservoir were investigated both in the water and sediment. The results reflected progressive deterioration and indicated moderate to heavy pollution from the metals. The metal levels in the water were in the order of Zn > Cu > Pb > Cd. The statistical analysis revealed primary sources of heavy metals contamination in the water. Cd, Cu, Zn, and Pb in the water likely originate from anthropogenic activities including agricultural runoff (i.e., the use of fertilizers and pesticides) and urban runoff (i.e., improper wastewater discharge and waste disposal). Among the four metals, the Pb levels in the water significantly exceeded the guideline for drinking water in all locations. The health risk assessment revealed serious non-carcinogenic risks of Pb intake in the children at the age below 10 and infants. Appropriate control and protection strategies are urgently needed to cut off the main Pb exposure pathway in pregnant women, children, and infants.

Characterization and Evaluation of Human Health Risk of Heavy Metals in Tin Mine Tailings in Selected Area of Plateau State, Nigeria

Tin mining tailings are unprocessed waste materials that overlie an ore which are displaced during mining activities. This research work is aimed at characterizing and evaluating the human health risk of heavy metals in tin mine tailings in Zabot (S3) and Tafan (S4) districts in Barkin Ladi Local Government Area of Plateau State, Nigeria. The samples were characterized using EDX-XRF and SEM. The concentrations of seven heavy metals (Pb, Cr, As, Ni, Cd, Cu and Zn) were determined in S3 and S4. The results showed that Cr, Ni, Cd, Cu and Zn were within the USEPA permissible limits, except for Pb and As with range of (270-300) mg/kg and (40-70) mg/kg respectively for both mining and control sites of S3 and S4. The SEM results revealed small particles size with fine porous structure, and rough areas with varying sizes and pores distributed over the surface for S3 and S4 respectively. Results of the risk assessment showed that the hazard quotient HQ and HI values were greater than 1 indicating high risk. The Carcinogenic and non-carcinogenic risks associated with Pb, Zn, Cd, Cr, Ni and As were evaluated for S3 and S4 for the three exposure pathway and it was found that the mining sites pose more risk than the control and the children were more exposed than the adults. The carcinogenicity of these samples were due to the high hazard quotient for ingestion and dermal exposure pathway. The R total results for As, Cr, Pb and Ni for mining site S3 were found to be (1.39 × 102 , 2.02 × 10-7 , 3.30 × 103 and 8.17 × 10-8 ), and control site (3.42 × 103 , 2.64 × 10-5 , 38.30 × 101 , 6.90 × 10-8 ) for As, Cr, Pb and Ni respectively. From the R total results As and Pb were more than the acceptable threshold, while Cr and Ni were below the threshold of 1 × 10-4 . For the mining site S4, the R total were found to be (5.70 × 102 , 1.82 × 10-7 , 3.63 × 104 and 9.64 × 10-9 ),and the control (1.16 × 103 , 1.71 × 10-7 , 31.1 × 102 and 1.51 × 10-8 ) for As, Cr, Pb and Ni respectively. From the results of the mining and control sites, As and Pb R total were higher than the acceptable threshold, while Cr and Ni were below the threshold of 1 × 10-4 .

Health Risk Assessment of Metals via Multi-Source Oral Exposure for Children Living in Areas with Intense Electronic Manufacturing Activities

Oral ingestion is the predominant pathway of metal(loid)s exposure. In this study, the health risks of typical metal(loid)s (including Mn, As, Cr, Cd, and Pb) via multi-source, oral pathways for children aged 3–12 years, living in an area of China dominated by the electronic manufacturing industry, were studied based on the field sampling of duplicated diet, soil, and drinking water. Child-specific ingestion parameters were measured (except the soil ingestion rates, which were from a previous study of the same population), and a Monte Carlo method was applied to determine the uncertainty of the risk assessment. It was observed that children living in such environments were at risk of metal(loid)s exposure, with the accumulative carcinogenic risk exceeding the maximum acceptable level. Food intake was identified to be the primary exposure pathway. Moreover, Pb and Cr were the major risk elements to local children’s health. Compared with primary school students, kindergarten children experienced a higher risk. This study highlights that high attention should be paid to children living in suburban areas dominated by the electronic manufacturing industry, and that priority should be given to studies on metal(loid)s exposure deriving from different types of food and their corresponding bioavailability, in order to further discern the precise risk sources to protect children’s health.

Ecological and Health Risks Assessment of Potentially Toxic Metals and Metalloids Contaminants

Potentially toxic environmental contaminants, including metals and metalloids, are commonly found in emerging economies. At high concentrations, elements such as As, Cr, and Ni can be hazardous and may lead to various health problems in humans, including cancer. The current study measured As, Cd, Cr, Cu, Ni, Pb, V, and Zn concentrations in agricultural soils. Pollution levels and potential negative impacts on human and environmental health were determined using the United States Environmental Protection Agency (USEPA) standard methodologies. According to the study’s findings, the studied element concentrations descended in the following order: Zn > Cr > V > Ni > As > Cu > Pb > Cd. Of these, As (27.6 mg/kg), Cr (85.7 mg/kg), Ni (61.9 mg/kg), and Zn (92.3 mg/kg) concentrations were higher than average world background levels. Each of these elements also had an enrichment factor (EF > 1), indicating their anthropogenic origin. The combined pollution load index (PLI > 1) and geo-accumulation index (Igeo) range values of −0.2–2.5 further indicated that the soil was polluted up to 58%. However, the ecological risk factor (Er ≤ 40.6) and potential ecological risk index (PERI = 79.6) suggested low ecological risk. A human health risk evaluation showed that only As, with a hazard index (HI) of 1.3, posed a non-carcinogenic risk to infants. Additionally, As, Cr, and Ni, with total carcinogenic risk (TCR) values of 1.18 × 10−4 and 2.06 × 10−4 for adults and children, respectively, proved carcinogenic to both age groups. The elements’ carcinogenic risk (CR) potential descended in the following order: Ni > As > Cr. Additionally, for both adults and children, oral ingestion is the most likely exposure pathway. Our findings support the need for closer monitoring of potentially toxic metals and metalloids levels in cultivated soils and farm produce in Qatar.

Groundwater Arsenic-Attributable Cardiovascular Disease (CVD) Mortality Risks in India

Cardiovascular diseases (CVDs) have been recognized as the most serious non-carcinogenic detrimental health outcome arising from chronic exposure to arsenic. Drinking arsenic contaminated groundwaters is a critical and common exposure pathway for arsenic, notably in India and other countries in the circum-Himalayan region. Notwithstanding this, there has hitherto been a dearth of data on the likely impacts of this exposure on CVD in India. In this study, CVD mortality risks arising from drinking groundwater with high arsenic (>10 μg/L) in India and its constituent states, territories, and districts were quantified using the population-attributable fraction (PAF) approach. Using a novel pseudo-contouring approach, we estimate that between 58 and 64 million people are exposed to arsenic exceeding 10 μg/L in groundwater-derived drinking water in India. On an all-India basis, we estimate that 0.3–0.6% of CVD mortality is attributable to exposure to high arsenic groundwaters, corresponding to annual avoidable premature CVD-related deaths attributable to chronic exposure to groundwater arsenic in India of between around 6500 and 13,000. Based on the reported reduction in life of 12 to 28 years per death due to heart disease, we calculate value of statistical life (VSL) based annual costs to India of arsenic-attributable CVD mortality of between USD 750 million and USD 3400 million.

Maternal high-fat diet during pregnancy with concurrent phthalate exposure leads to abnormal placentation

Di(2-ethylhexyl) phthalate (DEHP) is a synthetic chemical commonly used for its plasticizing capabilities. Because of the extensive production and use of DEHP, humans are exposed to this chemical daily. Diet is a significant exposure pathway and fatty food contain the highest level of phthalates. The impact on pregnancy following DEHP exposure and the associated interaction of high fat (HF) diet remains unknown. Here we report that exposure of pregnant mice to an environmentally relevant level of DEHP did not affect pregnancy. In contrast, mice fed a HF diet during gestation and exposed to the same level of DEHP display marked impairment in placental development, resulting in poor pregnancy outcomes. Our study further reveals that DEHP exposure combined with a HF diet interfere with the signaling pathway controlled by nuclear receptor PPARγ to adversely affect differentiation of trophoblast cells, leading to compromised vascularization and glucose transport in the placenta. Collectively, these findings demonstrate that maternal diet during pregnancy is a critical factor that determines whether exposure to an environmental toxicant results in impaired placental and fetal development, causing intrauterine growth restriction, fetal morbidity, and mortality.

Risk of exposure to metals in soil contaminated by steel industry waste for a population in Volta Redonda, RJ

The aim of this study was to identify the risk of population’s exposure, by different exposure routes, to Zn, Ni, Cu, Cr, and Pb in the soil of a condominium. Six sampling points in three campaigns provided thirty-six soil samples, collected at two depths, one superficial, 0.20 m, and the other underground, between 2.00 and 3.00 m. The results show that the levels of metals in the condominium's soil are generally high. Children cannot withstand the same doses as adults since they are more susceptible and risk greater damage to health. The non-carcinogenic risk based on the hazard quotient (HQ) and the health index (HI) values for each exposure pathway and for each metal were observed to be less than (<) 1. The results showed an immediate carcinogenic risk by chromium ingestion for children. Nevertheless the combined effect for each exposure pathway (TCRI) for adults is close to becoming unacceptable after exposure to Cr by ingestion. The results suggest that contamination by metals is more likely to occur among children than adults at similar exposure levels. Thus, the condominium built on an area contaminated by steel industry waste raises concern, requiring the continuous monitoring of its population.

A Brief Review of the Structure, Cytotoxicity, Synthesis, and Biodegradation of Microcystins

Harmful cyanobacterial blooms pose an environmental health hazard due to the release of water-soluble cyanotoxins. One of the most prevalent cyanotoxins in nature is microcystins (MCs), a class of cyclic heptapeptide hepatotoxins, and they are produced by several common cyanobacteria in aquatic environments. Once released from cyanobacterial cells, MCs are subjected to physical chemical and biological transformations in natural environments. MCs can also be taken up and accumulated in aquatic organisms and their grazers/predators and induce toxic effects in several organisms, including humans. This brief review aimed to summarize our current understanding on the chemical structure, exposure pathway, cytotoxicity, biosynthesis, and environmental transformation of microcystins.