Incorporating bioaccessibility into human health risk assessments of heavy metals in urban park soils

Effect of gut microbiota on in vitro bioaccessibility of heavy metals and human health risk assessment from ingestion of contaminated soils

To identify the role of gut microbiota in human health risk assessment, the bioaccessibility of heavy metals in 14 soil samples were determined in simulated gastrointestinal fluids. Compared to the small intestinal phase, the bioaccessibility values of the colon phase varied, either increased by 3.5-fold for As, by 2.2-fold for Cr, and by 1.6-fold for Ni, or reduced by 4.4-fold for Cu, respectively. The colon incubation with adult gut microbiota yielded higher bioaccessibility value of As (1.3 times) and Fe (3.4 times) than that of the child in most soil samples. Colon bioaccessibility was about 60% greater of Cd for the adult and 30% higher of Cr for the child. Congruent data on the bioaccessibility of Cu and Ni was observed. In addition, correlation analysis indicated that in vitro bioaccessibility was primarily related to total concentrations of heavy metals in soils, followed by soil pH and active Fe/Mn oxide. Significantly, risk assessment calculated based on colon bioaccessibility indicated that the target hazard quotient (THQ > 1) of As was presented in 3 soil samples for the adult (1.05-3.35) and in 9 soil samples for the child (1.06-26.93). The hazard index (HI) of the child was 4.00 on average, greater than that of the adult (0.62), primarily due to the contribution of As and Cd. It suggested non-carcinogenic risks are likely to occur in children through typical hand-to-mouth behavior. The adjustment of colon bioaccessibility will result in more accurate risk assessment of human exposure to heavy metals from oral ingestion of contaminated soils.

Heavy metal- and organic-matter pollution due to self-heating coal-waste dumps in the Upper Silesian Coal Basin (Poland)

This study provides potential insight between self-heating coal-waste dumps and related environmental pollution in southern Poland. Samples collected from dumps in the Upper Silesian Coal Basin were used to quantify released contents of organic- and inorganic pollutants, i.e., polycyclic aromatic hydrocarbons (PAHs) and trace elements (Pb, Cd, Cr, Cu, Zn, Ni, Hg, As). Elevated Hg concentrations (~100-1078 mg/kg) and Pb (~600-2000 mg/kg) attest to the evaporation of these metals from deeper parts of the dumps. The acidic pH levels (3.0-4.5) may help to mobilize these elements. Pearson's correlation coefficients for samples analyzed by AAS and ICP-MS indicate a similar origin for Cd, Zn, and As. Mostly 2- and 3-ring PAHs, especially anthracene in burnt soil, dominate in the samples. Chlorinated PAHs, thiophenol, pyridines, quinolines (and derivatives) in thermally-altered samples, and waste containing pyrolytic bitumen indicate coking conditions. The high levels of Hg, Pb, and Cd, and chlorinated PAHs and nitrogen heterocycles formed or enriched during self-heating in these dumps should be deemed a significant environmental hazard. Calculating the lifetime cancer risks due to PAHs and heavy metals accumulations in the dumps are substantial, and access to these dumps should be prohibited.

Tracing the sources of bioaccessible metal(loid)s in urban environments: A multidisciplinary approach

Understanding the links between sources of magnetic particles and bioaccessibility of metal(loids) in environmental sampling media is crucial for better evaluating human health risks, although relevant information in the scientific literature is scarce. Here, soil, road and house dust samples from a heavy industrial area in Greece were characterized in a multidisciplinary study combining magnetic measurements, SEM/EDS analyses, bioaccessibility measurements and Pb isotopic analyses of bioaccessible Pb. The oral and inhalable bioaccessible fractions of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were assessed by applying simulated gastric and lung solutions. SEM/EDS analysis revealed the abundant presence of anthropogenic Fe-containing spherules of industrial origin in all sampling media, often containing minor contents of Cr, Cu, Mn, Pb and Zn. The inhalation bioaccessibility (%) in all environmental compartments was higher than the oral one for most elements analyzed in the present study. Clear associations between magnetic susceptibility and bioaccessible amounts of most of analyzed elements were encountered for the soil and road dust. The isotopic analyses of bioaccessible Pb showed that there are significant differences in the isotopic ratios between total and bioaccessible Pb. We conclude that Pb solubilized by the simulated gastric and lung extractions is principally anthropogenic, representing a mixture of industrial Pb and Pb related to the past usage of leaded petrol. Low values of ²⁰⁶Pb/²⁰⁷Pb were accompanied by high bioaccessible contents of Cd, Pb and Zn indicating that anthropogenic (mostly industrial) sources exert influence on the bioaccessible forms of these metals. Coupling magnetic and bioaccessibility measurements with stable isotopic technique of bioaccessible Pb is more reliable for determining Pb and other metal sources with high oral and inhalation bioaccessibility.

Potential risk of exposure to heavy metals from co-processing of secondary wastes in the Republic of Korea

The co-processing of secondary wastes during ordinary Portland cement (OPC) can result in high heavy metal concentrations in OPC products. However, earlier studies have not evaluated the concentrations of heavy metals (HMs) in OPC as a function of secondary input materials. Further, the health risk assessment (HRA) model has, thus far, has not been employed to assess the potential health risks associated with secondary raw materials and secondary fuels in OPC. Hence, to address these knowledge gaps, herein, monthly data for six HMs in the input materials and fuels from seven OPC manufacturers in the Republic of Korea were analyzed and modeled. Pb and Cu concentrations were found to be approximately 10-200 and 4-200 times higher than those of the other HMs, respectively. Furthermore, maximum Pb and Cu concentrations were 2-3 and 2-5 times higher than those reported in other countries, respectively. The quantity of input material had a significant influence on the observed patterns, and secondary raw materials, secondary additives, and secondary fuels were also determined to be important. Based on HRA assessment, although the risk levels were within permissible ranges, carcinogenic hazards attributable to Cr and Pb were not negligible. The results can aid in informed decision making and in implementing effective measures for managing risks associated with HMs in the OPC industry, thereby ameliorating threats to human health and environment.

Evaluation of Chemical Parameters of Urban Drinking Water Quality along with Health Risk Assessment: A Case Study of Ardabil Province, Iran

In recent years, in addition to water resources' quantity, their quality has also received much attention. In this study, the quality of the urban water distribution network in northwestern Iran was evaluated using the water quality index (WQI) method. Then, some important trace elements were investigated, and finally, the health risk assessment was evaluated for both carcinogenic elements (Ni, Cd, Cr, Pb, and As) and non-carcinogenic elements (Ca, Mg, Na, K, F, NO3, and Cu) using carcinogenic risk (CR) and hazard quotient (HQ), respectively. In the present study, the WQI was calculated based on both World Health Organization (WHO) and Iranian drinking water standards. Comparing the results of these standards revealed that the WQI based on the Iranian standard was slightly higher. Regarding the calculated WQI for the study region, the status of water quality for drinking consumption is in the good water quality class (25 < WQI < 50). It was observed that Cu and Cd have the highest and lowest concentrations in all sampling points, respectively. Hazard Index (HI) results showed that the non-carcinogenic substances studied had a low risk for both adults and children (<1.0). However, the CR results showed that Ni, Cd, and As were above the desired level for both children and adults. The results of this study can be applied for efficient water management and human health protection programs in the study area.

Morpho-chemical characterization and source apportionment of potentially toxic metal(oid)s from school dust of second largest populous city of Pakistan

Interior settled dust is one of the greatest threats of potentially toxic metal(oid)s (PTMs) exposure to the children, especially in the school environment. Therefore, it is more worthy of having in-depth knowledge of compositional characteristics of school dust. Forty schools were selected of Lahore city for dust sampling. The school dust was analyzed to determine the PTMs (As, Cd, Cr, Cu, Ge, Mo, Ni, Pb, Sb, Sn, Sr, V, and Zn) concentrations using ICP-MS. The morphological characteristics, PTMs speciation, and mineralogy of school dust were examined using SEM with EDS, XPS, and XRD, respectively. Moreover, the geo-accumulation index (I_geo), potential ecological risk index (PERI), and multivariate statistical analysis were employed to assess the pollution levels, ecological risk, and source identification of PTMs, respectively. The I_geo indicated a heavily-extreme pollution level of Cd (I_geo = 4.92), moderate-heavy pollution of Zn (I_geo = 3.22), and Pb (I_geo = 2.78), and slight-moderate pollution of Cr (I_geo = 1.62), and Cu (I_geo = 1.53). The ecological risk has been found extremely high for Cd and moderately high for Pb and As, while potential ecological risk found extremely high posed by cumulatively all selected PTMs. Multivariate statistical analysis showed that sources of PTMs comprise of natural processes as well as several anthropogenic processes like vehicular emissions, agricultural and industrial activities. The SEM, XRD, and XPS analyses demonstrated the presence of airborne particles and PTMs containing minerals with several toxic chemical species in school dust. This study can help to develop strategies to reduce school indoor pollution and hence to establish an eco-friendly learning environment for children.

Occurrence, geochemical fraction, ecological and health risk assessment of cadmium, copper and nickel in soils contaminated with municipal solid wastes

Unscientific municipal solid waste (MSW) dumping provokes heavy metal (HM) associated ecological and human health hazards through heightened bioavailability and bioaccumulation. In this study, we focused on three important HMs Cadmium (Cd), Copper (Cu) and Nickel (Ni) and their geochemical fractions, to enable clutter free data management, analysis and interpretation. Stratified random soil sampling was carried out from twenty different locations around a Ramsar site (Deepor Beel) in Guwahati, India. The spatial concentration profiles of Cd, Cu and Ni were determined by data elicited from geochemical fractionation and the Geographic Information System (GIS). Ecological and health risks indices were used to evaluate the severity of soil pollution and assess the level of health risks. All the three HMs thus evaluated, conformed to the potential bioavailable category. Cd (54.59%) was associated mostly with the carbonate bound fraction (F3), while 25.53% of Cu and 40.60% Ni were associated with the exchangeable fraction (F2). Significant contamination levels and higher ecological risks posed by these metals were in the order Cd > Ni > Cu. Children were found to be more vulnerable towards Cd associated health risks whereas, Ni posed threats to both adults and children. Cu posed no risk to human health. Geochemical fractionation and different indices played a critical role in the integrated assessment of soil pollution, ecological and health risk assessment, and provided an empirical basis for the sustainable future planning and comprehensive adaptive management practices for MSW.

Accumulation and health implications of metals in topsoil of an urban riparian zone adjacent to different functional areas in a subtropical city

The riparian zone is a river-land ecotone, and its environmental conditions have a significant effect on the river ecosystem and population health. In this study, As, Cu, Cr, Cd, Mn, Fe, Ni, Pb, and Zn in the topsoils of urban riparian zones in a subtropical city in southeast China were quantitatively estimated by inductively coupled plasma-optical emission spectrometry. The geoaccumulation index and health risk evaluation model were adopted to assess the accumulation characteristic and health risk of residents' exposure to metals. Principle component analysis was used to determine the source of metals. The results showed that the mean contents of metals (except Fe) were higher than the soil background value, but none of the metal contents exceeded the mass limit of environmental quality standards. The order of the geoaccumulation index was Cd > Mn > Cu > Cr > Pb > Zn > As > Ni > Fe. The contamination level of Cd was classified as slight, whereas the other metals did not contribute to pollution. The spatial distribution of metals in the riparian zone was compatible with the pattern of functional zones in the adjacent urban areas, where levels of Cr, Cd, Fe, Mn, and Ni were higher in commercial areas, as were Pb and Zn in under-construction land and As in residential and industrial areas. Carcinogenic risks of Cr, As, and Pb were acceptable. The hazard index indicated no significant noncarcinogenic risks from any metals. However, noncarcinogenic risks of metals other than Mn were higher for children than for adults, and the primary exposure route of metal into the human body was ingestion for children and inhalation for adults. Principle component analysis indicated that the primary sources of Cr, Ni, Mn, Cu, and Fe were pedogenic processes and mineral weathering, whereas Zn, As, Pb, and Cd mainly originated from anthropogenic sources, specifically, Zn from transportation emission, Pb from transportation emission and industry waste, As from coal combustion and residential waste, and Cd from pigments/paint used in commercial buildings, urban greening, consumer waste, and transportation emission.

Environmental health risk assessment of heavy metal exposure among children living in an informal e-waste processing village in Viet Nam

This study was conducted to compare the exposure levels of five heavy metals via different pathways based on the field samplings and questionnaire surveys of children residing in an informal e-waste processing village and a reference village in Viet Nam. The findings revealed that levels of the total average daily intake (ADI) of the five heavy metals collected from a child at the exposed village were 3.90 times higher (p < 0.01) than that of a child at the reference village. Ingestion of cooked rice was the largest contributor to the total ADI of the children tested at both villages. However, the risks from water drinking and dermal contact of soil were negligible. The total non-carcinogenic risk and carcinogenic risk in an exposed child were significantly higher (p < 0.01) than their respective risks in a reference child. The non-carcinogenic risk to an exposed child was likely to occur, while the risk to a reference child was negligible. The carcinogenic risks found in children from both of the villages, however, were higher than the acceptable values, indicating the potential health risks to the children from both villages. The susceptibility of children to heavy metal contaminations shown in this study suggests that a mitigating measure need to be initiated jointly by a public agency and a private organization to prevent children from the risks of being exposed to the contaminants.

Assessment of human health risk due to lead in urban park soils using in vitro methods

Beijing parks always have a large flow of local residents and tourists, and the soil Pb could threaten human health by incidental ingestion. Soil samples from eleven parks in Beijing were collected to assess the human health risk associated with Pb. Lead bioaccessibility in these parks ranged from 3.2 ± 0.4% to 12.1 ± 0.5% in the physiologically based extraction test (PBET) gastric phase and increased when approaching the city center. The chemical forms and soil properties (Fe, organic matter, and grain size) were important factors affecting the soil Pb bioaccessibility. The geo-accumulation index of Beihai Park (BH, near the city center) reached 1.3 ± 0.1 indicating moderate contamination. Lead health risk to children in BH should be of concern though its hazard quotient was below one. Results obtained from the Diffusive Gradients in Thin-films (DGT)-induced fluxes in the soils (DIFS) model showed that Pb-release in some parks farther from the city center was a "partially sustained case" (R_diff < R < 0.95) indicating that soil particles could partially replenish effective Pb to the soil solution. A relatively higher desorption rate constant (k₁) and shorter characteristic response time (T_c) were also found in these parks, indicating non-negligible release risk. Soil Pb based on the PBET method and DIFS model could provide a reliable reference to park managers for the health risk management of Pb pollution.

Modifying Effect of Soil Properties on Bio-Accessibility of As and Pb from Human Ingestion of Contaminated Soil

Exposure to soils contaminated with heavy metals can pose human health risk to children through ingestion of contaminated soil. Soil properties such as soil pH, reactive Fe and Al oxide content, clay content, soil organic matter (SOM), and cation exchange capacity (CEC) can reduce contaminant bio-accessibility and exposure. In vitro bio-accessibility (%IVBA) of As and Pb in 19 soils was determined using U.S. EPA Method 1340. Soil properties reduced the bio-accessibility of As by 17–96.5% and 1.3–38.9% for Pb. For both As and Pb, bio-accessibility decreased with increasing Al and Fe oxide content. Al oxides were found to be the primary driver of As and Pb bio-accessibility. Multiple regressions with AlOx, soil pH, %clay and/or FeOx predicted %IVBA As (p < 0.001). The multiple regression including log (FeOx + AlOx) and %clay explained 63% of the variability in %IVBA Pb (p < 0.01). Fe and Al oxides were found to be important drivers of As and Pb bio-accessibility, regardless of in vitro method. These findings suggested soil pH should be used in addition to reactive oxides to predict bio-accessible As. Risk-based adjustments using soil properties for exposure via incidental ingestion should be considered for soils contaminated with As and/or Pb.

Risk Assessment of Lead and Cadmium in Some Food Supplements Available on the Romanian Market

Across the world, there has been an increase in the consumption of food supplements. This may be due to the perception that these dietary supplements cannot negatively affect the health of consumers in any way. However, dietary supplements may not have the expected effect. In addition, it has been shown that supplements can sometimes be chemically, physically or microbiologically contaminated, if the hygiene conditions and Hazard Analysis Critical Control Points (HACCP) plan are not fully complied with. The aim of this study was to determine the lead and cadmium content of 41 food supplements available on the Romanian market and to assess the risk to consumer health. The graphite furnace atomic absorption spectrometry (GFAAS) technique was used for sample analysis after wet mineralization of the samples. The risk assessment was determined based on Estimated Daily Intake (EDI), Target Hazard Quotient (THQ), and Carcinogenic Risk (CR) calculations. Values obtained for both lead and cadmium fall within the limits imposed by the legislation in force. Small risks associated with the consumption of these food supplements was shown, with a main recommendation being to decrease the recommended daily dose in the case of food supplements.

Human health and ecological risk assessment of trace elements in urban soils of 101 cities in China: A meta-analysis

Urban soils pollution by trace elements arouses the growing interest in China. The aim of this study was to assess urban soil pollution by As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in China and the possible impacts on urban inhabitants and urban green spaces (UGS). Data from more than 17,000 samples were applied to characterize the status of 101 cities. The pollution assessment proved that 11% of the cities are heavily polluted. According to the Hazard Index, the value of risk for the infant population in 15 cities exceed the standardly accepted tolerable levels. The carcinogenic risk assessment demonstrated the potential threat in the cities with the total population approximately 20,566,900. Cr and As were detected to be the most hazardous elements. UGS may be seriously threatened by trace elements toxicity in 38 cities. Cd was found to be the riskiest element for UGS. Ecosystem services of UGS can be significantly disrupted under the current situation in China and their status is expected to deteriorate in the future. For this reason, it is essential to alter the policy of the urbanization process and develop functional concepts of urban green infrastructures adapted to the high level of contamination which shall improve human well-being in China.

Contamination, oral bioaccessibility and human health risk assessment of thallium and other metal(loid)s in farmland soils around a historic TlHg mining area

In this study, tweenty-nine soil samples were collected from a historic TlHg mining area, located in southwest Guizhou, China. Total concentrations of metal(loid)s in soils and in vitro extracts were analysed by ICP-MS, and the bioaccessibility of metal(loid)s was conducted by two often used in vitro extraction methods, Simplified bioaccessibility Extraction Test (SBET) and Physiologically Based Extraction Test (PBET). The health risk assessment based on total concentrations of metal(loid)s, bioaccessibility of SBET and PBET through soil ingestion were investigated. Results indicated that the collected cultivated soils contained elevated concentrations of Tl (44.8 ± 67.7 mg kg^-1), Hg (110 ± 193 mg kg^-1), As (84.4 ± 89.2 mg kg^-1) and Sb (14.8 ± 24.8 mg kg^-1), exceeding the regional background values of Guizhou province, China and the Chinese farmland risk screening values. However, the bioaccessibility of Tl, Hg, As and Sb were relatively low, usually less than 30% for most samples and varied greatly among metal(loid)s and sampling sites. The average bioaccessibility values of Tl, Hg, As and Sb by SBET were lower than those by PBET. The non-carsinogenic risk (HQ and HI) and Carcinogenic Risk (CR) values were significantly reduced when incorporating the bioaccessibiltiy of metal(loid)s into health risk assessment. It is worth noting that the health risk to children exceeded adults. Moreover, Tl and As contributed the most to the risk, indicating that more attention should be paid on Tl and As during the daily environmental regulation and management of contaminated soils in Lanmuchang.

A review on in-vitro oral bioaccessibility of organic pollutants and its application in human exposure assessment

Generally, human oral exposure assessments of contaminants have not considered the absorption factor in the human gastrointestinal tract, thus overestimating human exposure and associated health risk. Currently, more researchers are adding the absorption factor into human exposure assessment, and bioaccessibility measured by in-vitro methods is generally replacing bioavailability for estimation because of the cheap and rapid determination. However, no single unified in-vitro method is used for bioaccessibility measurement of organic pollutants, although several methods have been developed for these pollutants and have shown good in vitro-in vivo correlation between bioaccessibility and bioavailability. The present review has focused on the development of in-vitro methods, validation of these methods through in-vivo assays, determination of factors influencing bioaccessibility, application of bioaccessibility in human exposure assessment, and the challenges faced. Overall, most in-vitro methods were validated using bioavailability, and better in vitro-in vivo correlations were obtained when absorption sinks were added to the digestion solution to mimic dynamic absorption of organic chemicals by small intestine. Incorporating bioaccessibility into the estimation of human exposure by oral ingestion significantly decreases the estimated exposure dose. However, more investigations on bioaccessibility of hydrophobic organic compounds are urgently needed because many challenges for in-vitro methods remain to be overcome.

Health Risk and Geochemical Assessment of Trace Elements in Surface Sediment along the Hooghly (Ganges) River Estuary (India)

This study investigated sediment spatial and seasonal distribution of trace elements (TEs) (n = 16) and human health effects along the Hooghly River Estuary (India). The index of geo-accumulation (Igeo), enrichment factor (EF), hazard quotient (HQ), modified hazard quotient (mHQ) and toxic risk unit (TRI) were calculated to estimate sediment pollution level, while hazard index (HI) and lifetime cancer risk (LCR) were used to assess TEs enrichment vs. human health. The concentrations (µg/g dry weight) of TEs were: Cd (0.01–1.58), Cr (41.98–105.49), Cu (16.41–51.09), Ni (28.37–63.90), Fe (22075–47919), Mn (423–630), Co (11.43–23.11), Zn (48.82–105.81), V (63.92–138.92), Pb (25.01–43.27) and Ti (0.18–3.50); As (2.92–16.26), B (59.34–98.78), Si (11.52–98.78); Be (1.71–4.81), Ba (95.23–293.72). From Igeo and EF, Cd was the major contaminant, while Ni presented moderate/high contamination (HQ and TRI). Children were more exposed to carcinogenic and non-carcinogenic risks compared to adults. For non-carcinogenic substances, no significant risk was found to both children and adults (HIs < 1). The LCR for Cr (3.924 × 10−4 for children) and As (1.379 × 10−4 for children) was higher than the threshold limit value (TLV, 10−4 and 10−6) indicating significant carcinogenic risks to be managed.

Fractions, Contamination and Health Risk of Cadmium in Alpine Soils on the Gongga Mountain, Eastern Tibetan Plateau

Anthropogenic cadmium (Cd) in alpine soils is mainly from long-range atmospheric transport. Because of the high toxicity and mobility, whether the accumulation of Cd in the soils threats to ecosystem safety remains unclear. The fractions of soil Cd along three altitudinal transects on Gongga Mountain were analyzed to decipher the drivers on its mobility, and its contamination and health risk were assessed. The concentrations of Cd in the organic (O) and mineral (A) horizons were significantly higher on the eastern and southern transects than the western transect. The Cd fractions in the two horizons dominated by acid-soluble and reducible Cd. Soil organic matter and pH modulated the mobilization of soil Cd. Cadmium reached a moderate contamination level on the eastern and southern transects, but no or slight contamination on the western transect. The soil Cd had a low non-carcinogenic risk and no carcinogenic risk despite of adults or children.

Manganese: The overlooked contaminant in the world largest mine tailings dam collapse

Manganese (Mn) is an abundant element in terrestrial and coastal ecosystems and an essential micronutrient in the metabolic processes of plants and animals. Mn is generally not considered a potentially toxic element due to its low content in both soil and water. However, in coastal ecosystems, the Mn dynamic (commonly associated with the Fe cycle) is mostly controlled by redox processes. Here, we assessed the potential contamination of the Rio Doce estuary (SE Brazil) by Mn after the world's largest mine tailings dam collapse, potentially resulting in chronic exposure to local wildlife and humans. Estuarine soils, water, and fish were collected and analyzed seven days after the arrival of the tailings in 2015 and again two years after the dam collapse in 2017. Using a suite of solid-phase analyses including X-ray absorption spectroscopy and sequential extractions, our results indicated that a large quantity of Mn^II arrived in the estuary in 2015 bound to Fe oxyhydroxides. Over time, dissolved Mn and Fe were released from soils when Fe^III oxyhydroxides underwent reductive dissolution. Due to seasonal redox oscillations, both Fe and Mn were then re-oxidized to Fe^III, Mn^III, and Mn^IV and re-precipitated as poorly crystalline Fe oxyhydroxides and poorly crystalline Mn oxides. In 2017, redox conditions (Eh: -47 ± 83 mV; pH: 6.7 ± 0.5) favorable to both Fe and Mn reduction led to an increase (~880%) of dissolved Mn (average for 2015: 66 ± 130 µg L^-1; 2017: 582 ± 626 µg L^-1) in water and a decrease (~75%, 2015: 547 ± 498 mg kg^-1; 2017: 135 ± 80 mg kg^-1) in the total Mn content in soils. The crystalline Fe oxyhydroxides content significantly decreased while the fraction of poorly ordered Fe oxides increased in the soils limiting the role of Fe in Mn retention. The high concentration of dissolved Mn found within the estuary two years after the arrival of mine tailings indicates a possible chronic contamination scenario, which is supported by the high levels of Mn in two species of fish living in the estuary. Our work suggests a high risk to estuarine biota and human health due to the rapid Fe and Mn biogeochemical dynamic within the impacted estuary.

Concentration and risk assessment of toxic metals in indoor dust in selected schools in Southeast, Nigeria

The health risk of students’ exposure to some potentially toxic metals in classroom dusts in Southeast, Nigeria was assessed. Dust particles were collected from classrooms in some public high schools and digested with aqua regia before analysis for selected metals by atomic absorption spectrophotometry. The geoaccumulation index, contamination factor and the pollution load index were assessed from the metal concentrations of the dust. Hazard quotient and cancer risk index were used to estimate the potential health risk of students’ exposure to the metals in the dust. The metal concentrations (mg/kg) were in the ranges of 1.57–175.38 (Cr); 0.93–463.28 (Cu); 31.94.76–6623.41 (Fe); 4.96–143.98 (Ni); 2.64–375.27 (Zn); and 2.35–53.96 (Pb).The geo-accumulation index values showed that all the dust samples were polluted with Fe and Cr; and unpolluted with other metals with few exemptions. The contamination factor values showed that all the schools but one had a low contamination status due to Ni and Cu. There was moderate contamination by Pb at all the schools but two. All the schools had high contamination of Cr and Fe. The pollution load index indicated that the quality of all the classrooms was deteriorated. The calculated values of hazard quotient indicated that ingestion of dust at most of the classrooms would have no significant risk of non-carcinogenic effects on the health of the students. Dermal contact with the dust at all the classrooms would expose students to adverse effects of Fe. There will be adverse effect due to Pb for dermal contact with dust at most of the schools. Ingestion of dust particles at classrooms in all the schools would have carcinogenic effect due to Ni. Correlation analysis indicated that the sources of the metals varied. This study provided baseline data for relevant bodies to use in monitoring and controlling pollution so as to protect students from toxic metals.

Speciation, contamination, ecological and human health risks assessment of heavy metals in soils dumped with municipal solid wastes

The main aim of this work is to assess the extent of soil contamination, potential ecological and health risks associated with the disposal of municipal solid waste (MSW) near a Ramsar site in Assam, India. Soil samples were collected and analysed for three heavy metals (HMs), namely, chromium (Cr), manganese (Mn) and zinc (Zn). The sources of HMs and their pollution levels were evaluated using different indices. The results demonstrated that Cr contamination was high near the metal scrap segregations unit within the dumping site, otherwise, the ecological risks associated with Zn and Mn were found to be low. The speciation of Cr and Zn were associated with the Fe-Mn oxide bound (F4) fraction, accounting 44.23% and 30.68%, respectively, whereas Mn (52.55%) was associated with the exchangeable fraction (F2). The fate and origin of HMs were assessed using mobility and enrichment factors and 16 out of the 20 sampling sites fell under the category of heavily polluted category for Cr, while others which were nearby the metal segregation units fell under the strongly to extremely polluted category. In few sites, significant enrichment was observed for Zn and minimal to moderate enrichment for Mn, respectively. Health risk assessment results indicated that Cr posed higher threat to human health through ingestion.

The effects of urban vehicle traffic on heavy metal contamination in road sweeping waste and bottom sediments of retention tanks

Diffuse pollution formed during a surface runoff on paved surfaces is a source of heavy metals (HMs) of various origin. This research study indicates the connection between bottom sediments of retention tanks located on urban streams and road sweeping wastes (RSW) that migrate during surface runoff to the stormwater drainage systems with discharge to the retention tanks. Moreover, we test the primary sources of HMs in RSW by analysing the mechanical wastes (MW) produced by vehicles in order to track the relationship between car parts and HMs deposited in the retention tanks receiving the surface runoff from streets. To identify the origin of HMs diverse source tracking approaches were used: statistical methods, Pb isotope ratios, and the flag element ratio approach. MW presented a very high HMs content (max observed values in mg/kg d.w.: 10477-Zn, 3512-Cu, 412-Pb, 3.35-Cd, 226-Ni, and 633-Cr), while for RSW the HMs content was similar to the bottom sediments. The total carcinogenic risk raises concerns due to the Cr content. The source of Zn was tyre wear and traffic. Ni, Cr, Fe, and Cd were correlated to Zn and shared a common/similar origin. PCA suggested that Cu features quasi-independent behaviour. The Pb isotopic ratios of RSW indicated Pb enrichment originating from coal combustion, while the gasoline and diesel source of Pb was excluded. The Pb isotopic ratios characteristic for MW were in within the following ranges: 1.152-1.165 (²⁰⁶Pb/²⁰⁷Pb), 2.050-2.085 (²⁰⁸Pb/²⁰⁶Pb), and 2.350-2.418 (²⁰⁸Pb/²⁰⁷Pb). The complex analysis of HMs origin confirmed the motorization origin of HMs: Zn, Cr, Ni, and Cd, except Pb (coal combustion as the main source) and Cu (non-uniform origin). The results of various source tracking methods were coherent, but Pb isotope ratios alone brought important information allowing to link Pb in sediments to the atmospheric deposition of coal combustion products.

Spatial assessment of heavy metals contamination in household garden soils in rural Limpopo Province, South Africa

Heavy metal pollution in soil poses a serious health threat to humans living in close proximity and in contact with contaminated soil. Exposure to heavy metals can result in a range of adverse health effects, including skin lesions, cardiovascular effects, lowering of IQ scores and cancers. The main objectives of this study were to (1) use a portable XRF spectrophotometer to measure concentrations of lead (Pb), arsenic (As), mercury (Hg) and cadmium (Cd) in residential soils in rural Giyani in the Limpopo province of South Africa; (2) to assess the spatial distribution of soil metal concentrations; and (3) to assess pollution levels in residential soils. There were elevated levels of As at one of the sites where 54% of soil samples exceeded the Canadian reference levels for As of 20 mg/kg. Using the geoaccumulation index (I_geo) to determine contamination levels of As, 57% of soil samples from the most polluted site were found to be moderately to heavily and extremely contaminated with As (I_geo class 2-5). The site is located near the Giyani Greenstone Belt, which is characterized by abandoned mines and artisanal mining activities. Gold ores are closely associated with sulphide minerals such as arsenopyrite, and these have been found to contain high amounts of As. This study highlighted the potential for soil contamination and the importance of site-specific risk assessment in the context of environment and health impact assessments prior to major developments, including human settlement developments.

Risk assessment of potentially toxic elements in soils and vegetables around coal-fired thermal power plant: a case study of Dhanbad, India

The present study was intended to determine the potentially toxic elements (PTEs) concentration in fly ash (FA), soil, plant, and vegetable to assess the impacts of pollution on the nearby areas of coal-fired thermal power plant (TPP). The PTEs concentrations (mg/kg) in FA were Cr (48-74) > Pb (41-65) > Cd (7.4-9.7) > As (3.19-4.43) > Hg (0.518-0.598). The contamination factor (C_f) for Cd was highest in agricultural soil (C_f = 22) followed by roadside soil (C_f = 20), and forest soil (C_f = 15), which showed that the soil was strongly polluted due to the presence of Cd. The ecological risk index (ERI) in the topsoil of roadside area was also very high (1130), due to the high value of ecological risk factor of Cd (898) and Hg (213). The health risk associated with the intake of soil containing PTEs were also estimated by calculating hazard index (HI), and the values showed that the risk posed to children was minimum (HI < 1). But in case of roadside area, the HI was very close to one (0.975) indicating that the prolong exposure may pose severe health risk. The bioaccumulation coefficient of all PTEs for Albizia lebbeck and Madhuca longifolia were < 1, indicating less PTEs accumulation in the plant species. The hazard quotient of all PTEs (except of Hg) through vegetable consumption (Allium cepa and Raphanus sativus) was > 1, which signifies that the long-time consumption of contaminated vegetables may cause severe risk to the people.

Ecological security and health risk assessment of soil heavy metals on a village-level scale, based on different land use types

Land use affects the accumulation of heavy metals in soil, which will endanger ecological safety and human health. Taking the village as an administrative unit, the ecological safety and health risks of heavy metals, namely, Cr, Cu, Zn, and Pb in soils in the Houzhai River Watershed of Guizhou Province, China, were evaluated based on land use types by the Hakanson potential ecological risk methods and human health risk model. Results showed that the spatial heterogeneity of Cu and Zn was greatly affected by primary structural factors, and Cr and Pb were interfered by both structural factors and human activities. The geo-accumulation index of the heavy metals showed a light pollution in the study area. The comprehensive potential ecological risk of heavy metal in the area was divided into three levels: slight, moderate, and intense, and it is spatially high in the northwest and low in the southeast. Both non-carcinogenic risk and carcinogenic risk of the heavy metals to the human body are not significant and are acceptable. The risks of children are higher than adults, and direct intake is the primary route of exposure in the area. The potential ecological risk and human health risk of soil heavy metals are relatively obviously affected by digital elevation data and normalized vegetation index. The study has certain reference value for the prevention and control of regional soil heavy metal risk.

Mitigation in availability and toxicity of multi-metal contaminated soil by combining soil washing and organic amendments stabilization

In order to investigate the decrease in total metal contents and to mitigate the availability and toxicity of metals from farmland near a lead mining area, a combination of two effective soil washing and eco-friendly stabilization technologies was applied in current research. The pre-treatment was performed with three types of agents including Ethylenediaminetetraacetic acid (EDTA), citric acid (CA), and mixture of hydroxylamine hydrochloride and citric acid (HA)) and the post-treatment stabilization was adopted using four rich-carbon organic waste amendments (cow manure compost (CMC), vermicompost (VC), urban sewage sludge (SS), and sludge-derived biochar (BIO)). Furthermore, the fate of residual metals (leachability, plant-availability, bioaccessibility, and chemical distribution), soil quality indicators (phytotoxicity and enzyme activities), and some soil physicochemical properties were examined before and after the two-steps remediation. The soil washing, especially using HA and CA agents, dramatically increased the labile metals and negatively changed the soil microbial activity. The two-month stabilization with SS, BIO, and VC resulted in a significant control of the leachability and plant-availability of residual Zn and Pb. However, the post-treatment was only slightly immobilized of Cd. The amendments affected the restoration of soil pH and organic carbon as well as the improvement of available nutrients. Compared to the other amendments that caused restrictions, the SS significantly restored the enzyme activities. With the exception of CMC, the SS, VC, and BIO, indicated higher germination rate and growth of wheat were also obtained. This study reveal the ability of the complementary role of stabilization with soil washing to reduce metal toxicity and confirm the usefulness of municipal and animal wastes in enhancing soil and environmental qualities.

Oral and inhalation bioaccessibility of metal(loid)s in chromated copper arsenate (CCA)-contaminated soils: Assessment of particle size influence

Soil samples adjacent to ten CCA-treated utility poles were collected, sieved into four fractions (<2 mm, 250-90 μm, 90-20 μm and <20 μm), and characterized for their total metal(loid) (As, Cu, Cr, Pb, and Zn) content and physico-chemical properties. Oral bioaccessibility tests were performed using In Vitro Gastrointestinal (IVG) method for fractions 250-90 μm and 90-20 μm. Inhalation bioaccessibility tests were performed in particle size fraction <20 μm using two simulated lung fluids: artificial lysosomal fluid (ALF) and Gamble's solution (GS). The total concentration of metal(loid)s increased with decreasing particle size. Oral As bioaccessibility (%) increased with increasing particle size in 9 out of 10 soils (p < .05), but oral As bioaccessibility expressed in mg/kg was not significantly different for both particle size. Oral Cu bioaccessibility (% and mg/kg) was not influenced by particle size, but oral Cr bioaccessibility (% and mg/kg) increased when reducing particle size (p < .05), although Cr bioaccessibility was very low (< 8%). Oral bioaccessibility (%) of metal(loid)s decreased in the order: Cu > As > Pb > Zn > Cr. Bioaccessibility (%) in simulated lung fluids decreased in the order: Cu > Zn > As > Pb ≈ Cr using ALF, and As > Cu using GS solution. For all elements, inhalation bioaccessibility (% and mg/kg) using ALF was higher than oral bioaccessibility, except for Pb bioaccessibility (mg/kg) in two samples. However, solubility of metal(loid)s in GS presented the lowest values. Copper showed the highest oral and inhalation bioaccessibility (%) and Cr showed the lowest. Moreover, organic matter content and cation exchange capacity in particle size 90-20 μm were negatively correlated with Cu and Pb oral bioaccessibility (%).

Occurrence, sources and ecological and human health risks of polycyclic aromatic hydrocarbons in soils from some functional areas of the Nigerian megacity, Lagos

The study investigated the levels of the USEPA 16 PAHs in soils collected from selected functional areas (cemetery, commercial, industrial and residential areas) of the Nigerian megacity, Lagos. The soil samples were subjected to ultrasonic-assisted extraction in a 1:1 (v/v) mixture of dichloromethane/hexane, and the PAHs in the resulting extracts were determined by gas chromatography-mass spectrometry. The Σ16 PAHs in soils of these functional areas varied between 890-4675, 485-4513, 111-15,577 and 509-2047 μg kg^-1 for cemetery, industrial, commercial and residential areas, respectively. The benzo(a)pyrene carcinogenic (BaP_TEQ) and mutagenic equivalency (BaP_MEQ) values of PAHs in these soils spanned from 523 to 1046 and 446 to 1129 µg kg^-1, respectively. The hazard index values suggested that there are adverse (non-carcinogenic) health effects for a child's exposure to PAHs in soils of commercial areas. The cancer risk values resulting from an adult's and a child's exposure to PAHs in these urban soils via dermal contact and oral ingestion surpassed the target value of 10^-6 which suggested that there is a considerable cancer risk relating to human exposure to PAHs in these urban soils. An ecological risk assessment making use of soil quality guidelines and risk quotients suggested a low ecological risk to organisms in soils of these functional areas except for those from commercial areas. PAH isomeric ratios and principal component analysis indicated that PAHs in these soils arise from petrogenic inputs, such as occasional spills of liquid petroleum fuels and discharges from automobile workshops and generator houses, as well as pyrogenic processes including traffic emissions and combustion of fossil fuels and biomass.

The relevance of particle size distribution and bioaccessibility on human health risk assessment for trace elements measured in indoor dust

Trace metal contaminants in indoor dust pose a significant potential exposure risk to people because of the time spent indoors and the readily ingested and inhaled fine-grained composition of indoor dusts. However, there is limited trace metal data available on the specific interaction of dust particle size fraction and their respective bioaccessibility/bioavailability and its consequent effect on health risk assessment. This study addresses this knowledge gap by examining bioaccessible and bioavailable trace element concentrations (As, Cr, Cu, Mn, Ni, Pb, Zn) in 152 discrete size fractions from 38 indoor vacuum samples from a larger dataset (n = 376) of indoor dust from Sydney, Australia. Arsenic, Cu, Ni, Pb and Zn were most concentrated in the 90-150 μm fraction with Cr and Mn being more concentrated in < 45 μm fraction. Dust particle size fractions < 45 μm, 45-90 μm, 90-150 μm and 150-250 μm were analysed for their individual gastric phase (G-alone) in vitro trace element bioaccessibilities. Lead exposure risk was estimated using the United States Environmental Protection Agency's Integrated Exposure Uptake Biokinetic (IEUBK) children's model. Mean Pb bioaccessibility was 59.6%, 42%, 62% and 62.2% for < 45 μm, 45-90 μm, 90-150 μm, and 150-250 μm, respectively. Mean Pb absolute bioavailability (ABA) was lower at 26.2%, 18.4%, 27.2% and 27.3% for size fractions < 45 μm, 45-90 μm, 90-150 μm, and 150-250 μm, respectively. The predicted blood Pb (PbB) levels for a hypothetical child aged 1 to 3 years for each of the dust particle size fractions was > 5 μg/dL. Lead concentrations measured in the selected dust samples show a potential for adverse health impacts on young children with the greatest risk being from indoor dust sized 90-150 μm.

Incorporating oral bioaccessibility into human health risk assessment due to potentially toxic elements in extractive waste and contaminated soils from an abandoned mine site

The waste rock, tailings and soil around an abandoned mine site in Gorno (northwest Italy) contain elevated concentrations of potentially toxic elements (PTE) exceeding the permissible limits for residential uses. Specifically, the maximum concentrations of As, Cd, Pb, and Zn were 107 mg/kg, 340 mg/kg, 1064 mg/kg, and 148 433 mg/kg, respectively. A site-specific human health risk assessment (HHRA) was conducted for residential and recreational exposure scenarios, using an approach based on Risk Based Corrective Action (RBCA) method, refined by incorporating oral bioaccessibility data. Oral bioaccessibility analyses were performed by simulating the human digestion process in vitro (Unified BARGE Method). Detailed analysis of oral bioaccessible fraction (BAF i.e. ratio of bioaccessible concentrations to total concentrations on <250 μm fraction) indicated BAF of As (5-33%), Cd (72-98%), Co (24-42%), Cr (3-11%), Cu (25-90%), Ni (17-60%), Pb (16-88%) and Zn (73-94%). The solid phase distribution and mineralogical analyses showed that the variation of BAF is attributed to presence of alkaline calcareous rocks and association of PTE with a variety of minerals. The HHRA for ingestion pathway, suggested that bioaccessibility-corrected cancer risk reached up to 2.7 × 10^-5 and 0.55 × 10^-5 for residential and recreational senarios respectively (acceptable level is 1 × 10^-5). The hazard index (HI) recalculated after incorporation of oral bioaccessible concentrations for a residential scenario ranged from 0.02 to 17.9. This was above the acceptable level (>1) for 50% of the samples, indicating potential human health risks. This study provides information for site-specific risk assessments and planning future research.

Heavy Metals in the Soils of Placer Small-Scale Gold Mining Sites in Myanmar

BACKGROUND

Artisanal and small-scale mining activities are widely practiced globally. Concentrations of heavy metals associated with gold, such as copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb) can increase in the environment as a result of mining activities, leading to environmental pollution and pose toxicity risks to humans and animals.

OBJECTIVES

The aim of the present study was to investigate soil concentrations of toxic heavy metals in placer small-scale gold mining operations in Myanmar.

METHODS

Soil samples were collected from three placer small-scale gold mining sites: Site A located in the Hmawbon public protected forest, Site B and Site C, situated in the Nant-Kyin reserved forest around Nar Nant Htun village. At each site, soil samples were collected from four gold mining stages (ore processing, sluicing, panning, and amalgamation). Atomic absorption spectroscopy was utilized to examine the concentrations of As, Cd, Pb, and Hg.

RESULTS

The highest heavy metal concentrations were generally found in the amalgamation stages across all the gold mining sites. Across the three mining sites, the maximum heavy metal concentrations in the amalgamation stage were 22.170 mg.kg^-1 for As, 3.070 mg.kg^-1 for Cd, 77.440 mg.kg^-1 for Hg, and 210.000 mg.kg^-1 for Pb.

CONCLUSIONS

The present study examined the concentrations of As, Cd, Hg and Pb in the soil of several small-scale gold mining sites in Banmauk Township, Myanmar. The results demonstrated the presence of high concentrations of heavy metals in the soil of the gold mining sites. Miners in this area work without proper personal protective equipment, and frequent exposure to heavy metals in the soil may cause adverse health effects. The present study provides baseline data for future risk assessment studies of heavy metal contamination in gold mines.

COMPETING INTERESTS

The authors declare no competing financial interests.

Potentially toxic metals and the risk to children's health in a coal mining city: An investigation of soil and dust levels, bioaccessibility and blood lead levels

Coal is a primary energy source in the world. Potentially toxic metals (PTMs) emission from coal mining and combustion are posing a serious public health concern. In order to quantify and evaluate the effect of PTMs on children's health, the concentrations of 12 PTMs (As, Co, Cr, Cu, Mn, Ni, Pb, Sr, Zn, Ca, Fe, and Mg) bound in urban soil and street dust are determined and blood lead levels of these PTMs in 229 children (0-6 years old) are collected from the coal mining city of Yulin, China. In vitro pulmonary bioaccessibilities of PTMs are evaluated by artificial lysosomal fluid and Gamble's solution, and gastrointestinal bioaccessibilities by the unified BAGRE method (UBM); correlations between chemical speciation of PTMs and their bioaccessibility are examined, and children's (0-6 years old) health risks are systematically studied. Similar distribution levels of PTMs are found in soils and dusts, with the most polluted metals being Co, Sr, Ca and Pb. All PTMs (except Cr, Fe) are from the considerable artificial lysosomal fluid extraction both in soil and dust, while Ca and Co are favorably extracted in gastro and intestinal phases than others. Significant correlations are observed between the bioaccessibilities (lung and gastrointestinal) and Fe/Mn hydroxide-bound and carbonate-bound phases, which are key factors influencing and determining PTMs' bioaccessibility. Blood lead levels for children (0-6 years old) are 27.47 (21.65, 33.30) for 0-1 year olds, 32.29 (26.39, 38.19) for 1-2 year olds, 36.99 (28.16, 45.81) for 2-3 year olds, 30.79 (22.56, 39.01) for 3-4 year olds, 27.12 (17.31, 36.93) for 4-5 year olds, 34.59 (24.22, 44.97) for 5-6 year olds and 37.83 (24.15, 51.51) μg/L for 6-7 year olds, respectively, with 3.93%, 3.49%, 4.80%, 2.62%, 1.31%, 1.75% and 1.31% exceeding 50 μg/L, respectively. This indicates that the blood lead levels elevate for 1-2 year and 5-6 year old groups, which should be paid more attention. Although the non-carcinogenic and carcinogenic risks of most PTMs are under the acceptable level, the higher carcinogenic risk of Ni and non-carcinogenic risk of Pb should be monitored continuously. We suggest that further actions will be taken to reduce PTMs exposure for children through sustainable clean and ecological energy technology for coal mining, especially for those infants of 1-2 years old.

In vitro model insights into the role of human gut microbiota on arsenic bioaccessibility and its speciation in soils

The bioaccessibility of arsenic and its speciation are two important factors in assessing human health risks exposure to contaminated soils. However, the effects of human gut microbiota on arsenic bioaccessibility and its speciation are not well characterized. In this study, an improved in vitro model was utilized to investigate the bioaccessibility of arsenic in the digestive tract and the role of human gut microbiota in the regulation of arsenic speciation. For all soils, arsenic bioaccessibility from the combined in vitro model showed that it was <40% in the gastric, small intestinal and colon phases. This finding demonstrated that the common bioaccessibility approach assuming 100% bioaccessibility would overestimate the human health risks posed by contaminated soils. Further to this, the study showed that arsenic bioaccessibility was 22% higher in the active colon phase than that in the sterile colon phase indicating that human colon microorganisms could induce arsenic release from the solid phase. Only inorganic arsenic was detected in the gastric and small intestinal phases, with arsenate [As(V)] being the dominant arsenic species (74%-87% of total arsenic). Arsenic speciation was significantly altered by the active colon microbiota, which resulted in the formation of methylated arsenic species, including monomethylarsonic acid [MMA(V)] and dimethylarsinic acid [DMA(V)] with low toxicity, and a highly toxic arsenic species monomethylarsonous acid [MMA(III)]. Additionally, a high level of monomethylmonothioarsonic acid [MMMTA(V)] (up to 17% of total arsenic in the extraction solution) with unknown toxicological properties was also detected in the active colon phase. The formation of various organic arsenic species demonstrated that human colon microorganisms could actively metabolize inorganic arsenic into methylated arsenicals and methylated thioarsenicals. Such transformation should be considered when assessing the human health risks associated with oral exposure to soil.

Assessment of potential human health risk of trace element in wild edible mushroom species collected from Yunnan Province, China

Wild edible mushrooms are rich in nutritions and popular among people, but wild edible mushrooms easily accumulate potentially harmful trace elements, and excessive intake will harm health. The aim of this study was to investigate the potential health hazards of long-term intake of wild edible mushrooms in Yunnan Province, China. The concentrations of trace element (As, Cd, Cr, Cu, Hg, Pb, Ni, and Zn) in 19 species of wild edible mushrooms in Yunnan Province were determined by inductively coupled plasma mass spectrometry (ICP-MS). Further processing of the data, the potential health risk assessments of consumers were evaluated by the target hazard quotient (THQ), hazard index (HI), and incremental lifetime cancer risk (ILCR), respectively. Results showed that concentrations of trace element in wild edible mushrooms decreased in the order of Zn > Cu > As > Ni > Cr > Cd > Pb > Hg. Compared with the maximum standard by the WHO/China, the averages of As, Cd, Cr, Hg, and Zn were significantly greater than the standard. Among the tested wild edible mushrooms, HI values of Leccinum crocipodium, Thelephora ganbajun, Lactarius luteolus, Tricholoma matsutake, and Polyporus ellisii were more than 1. Thus, Leccinum crocipodium, Thelephora ganbajun, Lactarius luteolus, Tricholoma matsutake, and Polyporus ellisii are the main sources of risk. The value of THQ in ascending order was as follows: Pb (0.11) < Cd (0.75) < As (4.27) < Hg (6.87). Thus, Hg are the primary sources of health risk in the wild edible mushrooms in Yunnan Province. ILCR_(As) values of Thelephora ganbajun, Tricholoma matsutake, Laccaria amethystea, and Polyporus ellisii were more than 10^-4, these four samples are the primary sources of health risk. The mean values of ILCR for As in wild mushroom were 1.01 × 10^-4. The results suggest that there was potential health risk to the consumer associated with the long-term consumption of wild edible mushrooms collected from Yunnan Province. We propose that the concentrations of trace element should be periodically monitored in wild edible mushrooms.

Bioaccessibility and health risk assessment of trace metals in soils of greenhouse vegetable production near the industrial areas of the Yangtze River Delta, China

As a common environmental problem in China, trace metal accumulation and contamination in soils of greenhouse vegetable production (GVP) may pose significant health risk via oral ingestion, inhalation, and dermal contact to vegetable farmers and children playing in greenhouse fields. Thus, bioaccessibility and health risk of Cr, Ni, Cu, Zn, Cd, and Pb in GVP soils collected from 13 GVP farms or bases near industrial areas of the Yangtze River Delta, China, were investigated as a case study. The results suggested that both GVP and industrial discharges contributed a lot to accumulation or contamination especially of Zn and Cd in soil, which subsequently increased their bioaccessible concentrations. In addition, soil acidification caused by GVP also increased bioaccessible Cr and Ni concentrations in soil of the Anthrosols study area. However, the health risk assessment of metals in GVP soil through inhalation and oral ingestion considering metal bioaccessibility suggested no non-carcinogenic and carcinogenic risks to both farmers and children. In contrast, there was potential carcinogenic risk within acceptable level posed by Cr in GVP soil through dermal contact to farmers and children. This indicates that both GVP and industrial activities had limited effect on health risk of trace metals in GVP soil via ingestion, inhalation, and dermal contact. However, the carcinogenic risk posed by Cr, which mainly originated from natural sources, still cannot be negligible. Overall, the results will provide valuable information for decision-makers to develop reasonable strategies and guidelines for risk management of trace metals in GVP soil.

Health Risk Evaluation of Trace Elements in Geophagic Kaolinitic Clays within Eastern Dahomey and Niger Delta Basins, Nigeria

The deliberate consumption of earthly materials is a universally recognised habit with health benefits and risks to those that practice it. Thirteen (13) samples comprising of six (6) Cretaceous and seven (7) Paleogene/Neogene geophagic kaolinitic materials, respectively, were collected and analysed for trace element concentrations (V, Cr, Co, Ni, Zn, Pb, and Fe), and possible risk on consumers’ health. The trace element compositions were obtained using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and X-ray fluorescence spectrometry (XRF) analytical methods. Based on their average concentrations, Fe > V > Cr > Ni > Zn > Pb > Cu > Co and Fe > V > Cr > Zn > Cu > Pb > Ni > Co for the Cretaceous and Paleogene/Neogene geophagic clays, respectively. Iron concentrations were significantly higher in Paleogene/Neogene geophagic clays than in Cretaceous geophagic clays. The nutritional value of Cu and Zn were lower whereas, Cr and Fe were higher than the recommended dietary intake. The index of geoaccumulation (0 < I_geo ≤ 1) showed that the geophagic materials were uncontaminated to moderately contaminated by the trace elements. The overall hazard indices (HI) for non-carcinogenic effects showed that the geophagic clays pose threat to children (HI > 1) and no threat to adults (HI < 1) health. However, the carcinogenic risk indices (CRI) for Cr, Ni, and Pb were within acceptable cancer risks (10⁻⁶ < CRI < 10⁻⁴) for children and adults. Hence, based on the trace element s HI and CRI, this study concluded that the consumption of Cretaceous and Paleogene/Neogene geophagic kaolinitic clays poses no risks to adult health but children might suffer health risk if the geophagic clays are not beneficiated before ingestion.

Mobility and accessibility of Zn, Pb, and As in abandoned mine tailings of northwestern Mexico

Generation, storage, and management of waste coming from industrial processes are a growing worldwide problem. One of the main contributors is the mining industry, in particular tailings generated by historical mining, which are barely maintained, especially in developing countries. Assessing the impact of a mining site to surrounding soils and ecosystems can be complex, especially when determining mobility and accessibility of the contaminants is required to perform ecological and human health risk assessment. As an effort to obtain information regarding mobility and accessibility of some potentially toxic elements (Zn, Pb, and As) from an historical mining site of northwestern Mexico, the abandoned mine tailings of San Felipe de Jesús in central Sonora and adjacent agricultural soils were investigated. Mobility and accessibility were assessed by means of sequential extraction procedures and using simulated physiological media. Additionally, an assessment of accidental oral intake was calculated considering the bioaccessible fractions. Results show that higher concentrations of contaminants were found in sulfide-rich tailings (Zn = 92,540; Pb = 21,288; As = 19,740 mg kg^-1) compared with oxide-rich tailings (Zn = 43,240; Pb = 14,763; As = 13,401 mg kg^-1). Concentrations in agricultural soils were on average Zn = 4755, Pb = 2840, and As = 103 mg kg^-1. Zinc was mainly recovered from labile fractions in oxide-rich tailings (~ 60%) and in a lower amount from sulfide-rich tailings (~ 30%). Pb and As were mainly associated with residual fractions (80-95%) in both types of tailings. The percentage of mobile fractions (sum of water-soluble, exchangeable, and bound to carbonate fractions) in agricultural soils was as follows: Zn ~ 60%, Pb ~ 15%, and As ~ 70%. Regarding the phytoaccessible fraction, the studied elements in mine tailings and agricultural soil samples exceeded the threshold limits, except for As in agricultural soils. According to data obtained, toxic effects were also calculated. As for daily oral intake for non-carcinogenic effects in adults and children, only Pb and As exceeded reference dose values, especially in children exposed to sulfide-rich tailings and agricultural soils. Regarding carcinogenic effects of Pb and As, most of the samples were above acceptable risk values.

Health risk assessment of heavy metals in street dust around a zinc smelting plant in China based on bioavailability and bioaccessibility

In order to investigate pollution level, chemical speciation and health risk of exposure to heavy metals in street dust from smelting district, we carried the following studies: (a). the differences in the morphology of street dust in smelting and non-smelting districts using a scanning electron microscope; (b). the chemical speciation and bioavailability of heavy metals in <100 μm and <63 μm particles near a smelting district using a modified three-stage BCR sequential extraction procedure and in vitro digestion test, respectively; (c). the evaluation of the non-carcinogenic risk of children and adults exposure to dust based on bioaccessibility. The results showed that most of the dust particles near Huludao Zinc Plant (HZP) were relatively solid with less porosity, which might originate from incompletely burned mineral particles from the smelting process. The concentrations of Pb, Cd and Cu were much higher than the background levels: 1560, 178.5 and 917.9 mg kg^-1 in <100 μm dust samples, and 2099, 198.4, 1038 mg kg^-1 in <63 μm dust samples, respectively. Pb was mostly present in the reducible fraction and the acid exchangeable fraction, while Cd and Cu were the most common heavy metals in the acid exchangeable fraction and oxidizable fraction, respectively. The rank order of bioaccessibility for the gastric and intestinal phase was Cd (58.13%) > Pb (50.00%) > Cu (19.19%) and Cd (20.36%) > Cu (15.67%) > Pb (5.08%), respectively. Hand-to-mouth ingestion poses the greatest non-carcinogenic exposure risk compared with other exposure pathways. When bioavailability is taken into account, children experienced higher non-carcinogenic and carcinogenic risks of dust exposure compared with adults, and the <63 μm particles posed greater risks than <100 μm particles.

Potentially toxic elements (PTEs) in crops, soil, and water near Xiangtan manganese mine, China: potential risk to health in the foodchain

The pollution from large-scale manganese mining and associated industries in Xiangtan (south Central China) has created a significant burden on the local environment. The proximity of mining, and other industrial activity to the local population, is of concern and impact of past industrial on the food chain was evaluated by the assessment of common food groups (rice, soybean, and sweet potato), and the associated soil and water in the region. We focused on specific potentially toxic elements (PTEs): Mn, Pb, Cd, Cr, Cu, and Zn associated with industrial activity, identifying the distribution of pollution, the potential significance of total health index (THI) for local people and its spatial distribution. The study area showed severe contamination for Mn, followed by Cd and Pb, while other PTEs showed relatively light levels of pollution. When analyzing the impact on crops exceeding the tolerance limit, the dominant PTEs were Mn, Cd, and Pb, with lower significance for Zn, Cu, and Cr. The average THI value for adults is 4.63, while for children, is 5.17, greatly exceeding the recommended limit (HQ > 1), confirming a significant health risk. In the spatial distribution of the THI, the region shows strong association with the transport and industrial processing infrastructure. Long-term management needs to consider remediation aligned to specific industrial operations and enhance contamination control measures of ongoing activity.

Pollution status and human health risk assessments of selected heavy metals in urban dust of 16 cities in Iran

Urban dust contamination is becoming progressively noticeable, and heavy metals are primary pollutants in urban environments. The contamination of heavy metals in urban dust has been affecting the urban citizens due to their adverse effects on human health, and understanding their effects is a crucial stage for its management. This study is a review of the reports of heavy metal pollution in urban dust of 16 cities in Iran, aimed at determining pollution status and health risk calculation on the nationwide scale, using geo-accumulation index (Igeo), potential ecological risk index (PER), and health risk assessment model. Six toxic elements, namely cadmium, copper, chromium, nickel, lead, and zinc were evaluated in this study. The results presented that the total heavy metal concentrations in the studied cities decreased in the sequences of Zn > Cu > Pb > Ni > Cr > Cd. The average concentrations of Cd, Cu, Ni, Pb, and Zn in the studied cities exceeded the Iran Standard Soil limits for residential areas. The mean levels of studied heavy metals for cities was in the order of Kermanshah > Tehran > Tabriz > Rafsanjan > Hamedan > Isfahan > Mashhad > Ahvaz > Abadan > Kerman > Bushehr > Kashan > Shiraz > Zahedan > Masjed-e-Soleiman > Arak. The Results of Igeo revealed that the pollution levels of Cd, Cu, Pb, Ni, Cr, and Zn in the studied cities ranged from unpolluted to moderate pollution categorizations. The mean potential ecological risk factor (Eⁱ_r) values were below (E^r_i < 40), showing a low ecological risk level. Also, Eⁱ_r values for all cities showed that Cd, Pb, and Cr had the highest ecological risks than other heavy metals. However, the total potential ecological risk index (RI) values for studied cities were 172.1, showing a moderate ecological risk level. Human health risk assessment evaluation showed that in contrast to adults, children have more possible health risks (non-carcinogenic). Among the multiple pathways of exposure, the ingestion pathway was the most important exposure for both groups of population, followed by skin exposure and then breathing exposure. Total hazard index (HI) values among three exposure routes, were less than harmless level (HI < 1), displaying that there was not a non-carcinogenic risk for both groups of population. Cancer risk (CR) study exhibited that the potential risk of cancer decreases in the order of chromium > nickel > cadmium. The CR ranks of chromium, nickel, and cadmium were less than the maximum permissible level, presented an insignificant carcinogenic risk.

Contamination, sources and risk assessments of metals in media from Anka artisanal gold mining area, Northwest Nigeria

Mining is a major human activity that has contributed significantly to high degree of environmental and human health degradation. This study was done to uncover the degree of contamination and risks associated with metals in environmental media collected from Anka area, Northwest Nigeria. A total of eighty-two (82) samples which include 42 soils, 22 stream sediments, 13 tailings and 5 plants were collected. Media were air-dried, pulverized and sieved to collect fine particles. They were digested and analyzed for toxic metal contents using High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometer (HPLC-ICPMS). Metals analyzed include As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sb, Zn and Fe. From the results, degree of contamination in samples were obtained using pollution indices, while ecological and health risks were calculated using acceptable risk indices. Average concentrations of metals in the soils were: As: 0.64 μg/g; Cr: 42.55 μg/g; Pb: 131.76 μg/g; Hg: 0.85 μg/g while in sediments, the average concentration were As: 15.46 μg/g; Cr: 111.82 μg/g; Pb: 2234.02 μg/g; Hg: 2.12 μg/g. In tailings, the mean concentration were As: 4.79 μg/g; Cr: 96.95 μg/g; Pb: 2802.56 μg/g; Hg: 1.25 μg/g. Metals in plants are above acceptable limits. Metals in the media are both from geogenic and mining activities, and they pose high ecological risks. High carcinogenic (>10^-4) and non-carcinogenic (>1) health risks are associated with metals in media from this area. Further epidemiological studies should be carried to know the extent of occurrence of diseases associated with mining in the area.

Heavy metal(loid)s in the topsoil of urban parks in Beijing, China: Concentrations, potential sources, and risk assessment

Urban parks play an important role in the urban ecosystem and are also used by residents for recreation. The environmental quality of urban park soils might influence human health following long-term exposure. To assess potential sources and pollution risks of heavy metal(loid)s in the topsoil of urban parks, we subjected metal concentrations in soil samples from 121 parks in the Beijing urban area to geostatistical analyses, conditional inference tree (CIT) analyses, ecological risk and human health risk assessment. CIT effectively explained the influence of human activity on the spatial variation and accumulation of soil metal(loid)s and identified the contributions of natural and anthropogenic inputs. The main factors influencing the accumulation of heavy metal(loid)s, including urbanization duration, park age, per capita GDP, industrial output, and coal consumption, were evaluated by CIT. Except for Cr and Ni, the average concentrations of the metal(loid)s tested (Cu, Pb, Zn, Hg, As, and Cd) were higher than the background values. In the urban parks, Ni and Cr derived mostly from soil parent materials. Concentrations of Cu, Zn, Pb, Cd, As, and Hg were strongly associated with human influences, including industrial, agricultural, and traffic activity. After assessing health and ecological risks, we conclude that heavy metal(loid)s in the soil of Beijing urban parks pose no obvious health risk to humans, and the ecological risk is also low.

Contamination and risk levels of metals associated with urban street dust in Riyadh, Saudi Arabia

Urban street dust was collected from 22 locations in Riyadh, Saudi Arabia, and nine metals (Pb, Cr, Zn, Co, Cu, Al, Fe, Mn, and Ni) were investigated. The concentrations of these metals were employed in several common contamination evaluation indices to examine the contamination and the health risk caused by metals. Evaluation of these indices showed that they had variable degrees of contamination sensitivity. For individual contaminating elements (Pb, Cr, Zn, Co, Cu, and Ni), the sensitivities of the contamination of contamination factor (CF), the potential ecological risk (Ei), and geo-accumulation index (Igeo) were very similar. Therefore, these indices should yield very similar results. However, enrichment factor (EF) exhibited a different sensitivity pattern for determining the contamination caused by metals compared with the contamination level indicated by the other indices used in this study. Therefore, to avoid potential false indication of contamination, it is not recommended to use EF alone for determining contamination level. As indicated by four contamination evaluation indices (CF, Ei, Igeo, and EF), Riyadh was mainly contaminated by Pb. However, the health risk assessment results revealed that the Pb contamination level did not exceed the significant risk level for non-cancer effects. The cancer risk values indicated a negligible cancer risk to inhabitants of Riyadh exposed to metals associated with street dust. Considering the comprehensive contamination evaluation indices, the ecological risk index (RI) showed that about 77% of the sampling locations featured high ecological risk of which approximately 41% also featured high contamination indicated by pollution load index (PLI).

Health risk assessment and bioaccessibilities of heavy metals for children in soil and dust from urban parks and schools of Jiaozuo, China

Urban parks and schools sever as the mainly activity areas for children, but risk assessment posed by heavy metals (HMs) from soil and dust in these area has rarely been investigated. In this study, six urban parks and seven schools in Jiaozuo, China, were taken as research objects to understand the contamination level and bioaccessibility of HMs from soil and dust in urban parks and schools. The results indicated that Zn, Cu, Pb, Cd, As, Ni and Co from soil and dust were above the background values, especially Zn and Cd in dust, and As and Cd in soil. Serious Cd pollution was discovered, and respective Cd concentrations in soil and dust were 17.83 and 7.52 times the background value. Additionally, the average concentration and bioaccessibility of Zn, Mn, Pb, Cd, Cr, Ni and Co in dust were both higher than in soil. High concentration and high bioaccessibility of HMs in dust suggested that HMs contamination were serious and universal in Jiaozuo. The concentrations of most HMs were higher in the gastric phase, except for Cu and Cd which remained higher in the intestinal phase. Both in the gastric phase and intestinal phase, Mn, As and Cd in soil and dust both have high bioaccessibility which all exceed 10%. The carcinogenic and non-carcinogenic risks base on the total HMs for children (soil: 7.93, 1.96E-05; dust: 6.44, 3.58E-05) were greater than those for adults (soil: 6.35E-01, 1.32E-05; dust: 5.06E-01, 2.42E-05), and urban parks and schools posed high potential risk for children. Therefore, assessment the risk posed by HMs contamination of soil and dust in urban parks and schools is vital and urgent for children.

Characterizing pollution indices and children health risk assessment of potentially toxic metal(oid)s in school dust of Lahore, Pakistan

Toxic metal pollution is a renowned environmental concern, especially to sensitive environments like school classrooms and their association with children's health. The study was planned to determine the pollution characteristics of 13 potentially toxic metal (oid)s (PTMs) and their associated children's health risk assessment from school dust samples of considerably three land-use types (residential, roadside, and industrial areas) of Lahore, Pakistan. Geo-accumulation (I_geo), pollution (PI), integrated pollution (IPI) and pollution load (PLI) indexes were used to determine the PTMs contamination and USEPA health risk assessment models were employed to assess the health risks in children. The mean concentrations of Cd, Cr, Cu, Ni, Pb, and Zn for three land-use types were found much higher than the permissible limits. Results of pollution indices revealed that school dust was strongly contaminated with Cd, Pb, and Zn whilst moderately contaminated with Cr and Cu. Moreover, the health risk assessment models revealed no significant non-cancerous risks in children with predominantly highest hazardous index (HI) of Cr in industrial (4.61E-01) and Pb in both roadside (4.30E-01) and residential (2.26E-01) area schools. According to cumulative HI of all PTMs and exposure routes, the land-use areas were in descending order as industrial > roadside > residential. The calculations of hazardous quotient (HQ) showed ingestion was the leading pathway of PTMs exposure through school dust. For carcinogenic health risk (CR), the most prominent PTM was Cr with values of 1.53E-06 in industrial area schools, found close to the tolerable range (1.0E-06). Hence, school dust of Lahore prominently contaminated with eminent PTMs triggering slight health risks predominantly by ingestion exposure to children.

Bioaccessibility and human health risk assessment of metal(loid)s in soil from an e-waste open burning site in Agbogbloshie, Accra, Ghana

Environmental pollution and human health issues due to unrestricted electronic waste (e-waste) recycling activities have been reported at a number of locations. Among different e-waste recycling techniques, open burning of e-waste releases diverse metal(loid)s into the environment, which has aroused concern worldwide. In human health risk assessments (HHRAs), oral ingestion of soil can be a major route of exposure to many immobile soil contaminants. In vitro assays are currently being developed and validated to avoid overestimation of pollutants absorbed by the human body when calculating total pollutant concentrations in HHRAs. In this study, Cu, As, Cd, Sb, and Pb bioaccessibility in polluted soils (n = 10) from e-waste open burning sites at Agbogbloshie in Accra, Ghana, was assessed using an in vitro assay, the physiologically based extraction test. A bioaccessibility-corrected HHRA was then conducted to estimate the potential health risks to local inhabitants. The in vitro results (%) varied greatly among the different metal(loid)s (Cu: 1.3-60, As: 1.3-40, Cd: 4.2-67, Sb: 0.7-85, Pb: 4.1-57), and also showed marked variance between the gastric phase and small intestinal phase. The particle sizes of soil samples and chemical forms of metal(loid)s also influenced bioaccessibility values. Using these bioaccessibility values, both the hazard index and carcinogenic risk were calculated. The hazard index was above the threshold value (>1) for 5/10 samples, indicating a potential health risk to local inhabitants.

Trace metals in different socioeconomic indoor residential settings, implications for human health via dust exposure

In this study a number of heavy metals namely chromium (Cr), cadmium (Cd), zinc (Zn), barium (Ba), copper (Cu), manganese (Mn), cobalt (Co), rubidium (Rb), selenium (Se) are studied in the floor and air condition (AC) filter dust collected from urban and rural households of Saudi Arabia. To the best of our knowledge, many of these heavy metals are reported for the very first time in the indoor dust of Saudi Arabia. Studied metals were higher in urban dust than rural except Mn and Rb which were significantly higher (P < 0.05) in rural dust. All metals, except Cd, Zn, and Ba in urban settings, were detected at higher (P < 0.05) levels in AC filter dust than household floor dust from both rural and urban residential settings. Levels of the two dominant metals i.e., Zn and Mn were up to 1600 and 700 μg/g, respectively in studied dust samples. Also associations between heavy metals and a number of different socio-economic parameters were studied which was significant for some trace metals. In literature exposure to many of trace metals are associated with various health problems, therefore health risk assessment for the Saudi population was calculated by incremental lifetime cancer risk (ILCR) and hazardous index (HI) via dust ingestion, inhalation, and dermal contact. The ILCR for all metals was within the tolerable range of reference values of USEPA (1 × 10^{- 11} to 1 × 10^{- 4}). However, calculated HI for Mn, Cu, Ni, and Zn was more than 1 via dust exposure, which signifies the non-carcinogenic risk. The study highlights the occurrence of toxic metals in the indoor environments of Saudi Arabia and provides baseline data for future studies on these toxic metals in the region.

Sources and a Health Risk Assessment of Potentially Toxic Elements in Dust at Children's Playgrounds with Artificial Surfaces: A Case Study in Belgrade

The focus of this research on children's playgrounds with artificial surfaces aimed to establish levels of potentially toxic elements (PTEs) in dust, their origin, and impact on children at 15 playgrounds: 9 on school grounds and 6 on day nurseries in Belgrade (Serbia). Soil samples were taken from the immediate vicinity of the playgrounds to establish the origin of PTEs in the dust samples. Soil analyses revealed the lithogenic origin of Co, Cr, Ni, Fe, Mn, As, Cd, Cu, Pb, and Zn and the anthropogenic origin of As, Cd, Cu, Pb, and Zn. However, in the dust samples, the origin of the elements was different with As, Co, Fe, and Mn originating from the surrounding soil; Cr and Ni levels affected by both atmospheric deposition and the surrounding soil; Cd, Pb, and Zn concentrations impacted by atmospheric deposition; and Cu levels affected by factors of a local character. No noncancer risk was found for any of the individual elements investigated, nor for any of the playgrounds being studied, while a minimal cancer risk was found from As with values greater than 1E-6 at almost all the sites. Based on the results obtained for the spatial distribution of individual PTE levels, it was determined that the surrounding soil and atmospheric deposition have an almost equal impact on noncancer risk values.