Metal(loid) bioaccessibility and children's health risk assessment of soil and indoor dust from rural and urban school and residential areas

Kindergarten dust heavy metal(loid) exposure associates with growth retardation in children

Heavy metal contamination from electronic waste recycling sites is present in dust found in indoor kindergartens located in e-waste recycling areas, and its potential impact on child health is a significant concern. The association between heavy metal(loid)s and the child developmental indicators is still unclear. In 2019 and 2020, we enrolled 325 and 319 children in an e-waste recycling town, respectively. Corresponding 61 and 121 dust samples were collected from roads, houses, and kindergartens in the two years. The median concentrations of metals, including Cr, Ni, Cu, Zn, and Pb exceeded the allowable limits. The highest amount of cumulative enrichment (cEF) was observed in indoor kindergarten dust (cEF = 112.3400), followed by house dust (cEF = 76.6950) and road dust (cEF = 39.7700). Children residing in the e-waste town had below-average height and weight compared to their Chinese peers. Based on linear regression analysis, the daily intake of Cd, V, Mn, and Pb in indoor kindergarten dust was found to be negatively associated with head circumference (HeC) (P < 0.05). Similarly, the daily intake of As, Cd, and Ba in indoor kindergarten dust was found to be negatively associated with chest circumference (ChC) (P < 0.05). In addition, the daily intake of As, Cd, and Ba in indoor kindergarten dust was negatively correlated with body mass index (BMI), as per the results of the study (P < 0.05). Cross-product term analysis revealed a negative correlation between daily intake of heavy metal(loid)s and HeC, ChC, and BMI, with age and sex serving as influencing factors. In conclusion, exposure to heavy metal(loid)s in indoor kindergarten dust increases the risk of growth retardation and developmental delay in children.

Oral bioaccessibility of PTEs in soils: A review of data, influencing factors and application in human health risk assessment

Understanding the behavior of metal(loi)ds transported from soil to humans is critical for human health risk assessment (HHRA). In the last two decades, extensive studies have been conducted to better assess human exposure to potentially toxic elements (PTEs) by estimating their oral bioaccessibility (BAc) and quantifying the influence of different factors. This study reviews the common in vitro methods used to determine the BAc of PTEs (in particular As, Cd, Cr, Ni, Pb, and Sb) under specific conditions (particularly in terms of the particle size fraction and validation status against an in vivo model). The results were compiled from soils derived from various sources and allowed the identification of the most important influencing factors of BAc (using single and multiple regression analyses), including physicochemical soil properties and the speciation of the PTEs in question. This review presents current knowledge on integrating relative bioavailability (RBA) in calculating doses from soil ingestion in the HHRA process. Depending on the jurisdiction, validated or non-validated bioaccessibility methods were used, and risks assessors applied different approaches: (i) using default assumptions (i.e., RBA of 1); (ii) considering that bioaccessibility value (BAc) accurately represents RBA (i.e., RBA equal to BAc); (iii) using regression models to convert BAc of As and Pb into RBA as proposed by the USA with the US EPA Method 1340; or (iv) applying an adjustment factor as proposed by the Netherlands and France to use BAc from UBM (Unified Barge Method) protocol. The findings from this review should help inform risk stakeholders about the uncertainties surrounding using bioaccessibility data and provide recommendations for better interpreting the results and using bioaccessibility in risk studies.

Characterisation of the risk associated with chronic lifetime exposure to mixture of chemical hazards: case study of trace elements

Risk assessment methodology, mostly commonly used, faces the complexity of the environment. Populations are exposed to multiple sources of chemicals throughout life and the chemical mixtures they are exposed change during time (lifestyle factors, regulatory decisions, etc). The risk assessment needs to consider these dynamics and the evolution of the body with age, in order to refine the exposure assessment to chemicals and to predict the health impact of these exposures. This review highlights the latest methodologies developed to improve risk assessment, especially cor heavy metals. The methodologies aim to better describe the chemical toxicokinetic and toxicodynamic as well as the exposure assessment. Human Biomonitoring (HBM) data give great opportunities to link biomarkers of exposure with an adverse effect. Physiologically-Based Toxicokinetic (PBTK) models are more and more used to simulate the evolution of biomarkers in organisms, considering the external exposures and the physiological evolutions. PBTK models may also be used to determine the routes of exposure or to predict the impacts of schemes of exposure. The major limit is the integration of several chemicals in mixture with common adverse effects and the interactions between them.

Oral bioaccessibility of potentially toxic elements (PTEs) and related health risk in urban playground soil from a medieval bell metal industrial town Khagra, India

In vitro oral bioaccessibility assay (simple bioaccessibility extraction test) was used to assess bioaccessible PTEs (As, Cd, Co, Cu, Fe, Mn, Ni, Pb, Sn, and Zn) in 16 playground soils of Khagra, which is a medieval bell metal industrial town at Murshidabad district, West Bengal, India. The aim was also to establish levels of potentially toxic elements (PTEs) in soil, their origin, and human health risk, particularly on children. The average pseudo-total PTEs content in playground soil samples was in the decreasing order of Fe (18,988 mg kg-1) > Zn (1229 mg kg-1) > Cu (999 mg kg-1) > Mn (343 mg kg-1) > Pb (181 mg kg-1) > Sn (132 mg kg-1) > Co (8.63 mg kg-1) > As (5.21 mg kg-1) > Cd (0.88 mg kg-1). The pollution indices indicate significant enrichment of Cd, Cu, Pb, Zn, and Sn in the playground. The bioaccessible percentage of PTEs in the 16 playground soils ranged from 0 to 80.25%, where the range of percentage of bioaccessibility was 13.24-62.50, 0-61.46, 16.82-28.79, 5.05-73.06, 0.96-6.14, 2.28-38, and 0-80 for As, Cd, Co, Cu, Fe, Ni, and Zn, respectively. The order of percentage of bioaccessibility was As > Mn > Zn > Sn > Cu > Co > Pb > Cd > Ni > Fe. PCA extracted two major factors indicating the anthropogenic (Cd, Cu, Ni, Pb, Zn, and Sn) and geogenic (Co, Fe, and Mn) source. Stepwise multiple regression analysis exhibited that the oral bioaccessibility of PTEs did not correlate with physicochemical parameters like pH, EC. In contrast, Sn had a significant correlation with that of organic matter. The health risk for pseudo-total as well as bioavailable fraction in playground soil depicted that children were more vulnerable to ingestion of soil contaminated with PTEs, particularly for Cu and Pb. A risk management plan with the bioaccessible data involving detailed site-specific exposure factors to indicate the importance of the study in terms of child health safety is required.

Distribution, sources and health risks of heavy metals in indoor dust across China

The potential effects of heavy metals on human health have attracted increasing attention as most people spend up to 90% of their time indoors. Human exposure to heavy metals in indoor dust have only been characterised for limited regions in China, and full-scale data for different functional areas are not available. Therefore, this review analysed the concentrations, contamination characteristics, and potential health risks of seven heavy metals (including zinc (Zn), lead (Pb), copper (Cu), chromium (Cr), nickel (Ni), arsenic (As), and cadmium (Cd)) in indoor dust at 3392 sampling sites in 55 cities across 27 provincial regions of China based on literature data. Results revealed that the median heavy metal concentrations in indoor dust throughout China decreased in the following order: Zn > Pb > Cu > Cr > Ni > As > Cd. Traffic emissions and decorative materials are the primary sources of heavy metal pollution in indoor dust. No considerable non-carcinogenic risk was found for Zn, Cu, Cr, Ni, and Cd in indoor dust, while Pb and As exhibited potential non-carcinogenic risks to children, primarily distributed in cities across Southern China. Meanwhile, the carcinogenic risks posed by Cr and Ni were higher than those posed by As and Cd, especially in Southern China. Therefore, effective measures in Southern China should prioritised for controlling Pb, Cr, Ni and As pollution in indoor dust to reduce human health risk. This review is useful for policy decision-making and protecting human from exposure to heavy metals in indoor dust across China.

Determination of cadmium in Chinese pepper and its health implications based on bioaccessibility

The contamination of cadmium (Cd) in agro-products causes major concern because of its potential dietary risks. In this study, a total of 647 pepper samples from 21 provinces in China were randomly collected according to the distribution of pepper production. Cd pollution levels in Chinses pepper and its health risks were evaluated based on bioaccessibility, which was measured by the physiologically based extraction test (PBET). The results showed that Cd concentration in all pepper ranged from 0.002 to 1.470 mg/kg, with an average of 0.222 mg/kg and a median of 0.132 mg/kg. The highest daily intake of Cd was observed in the female child group (4.037 × 10^-5 mg/kg bw/day), which accounted for 4% of the maximum daily permissible dose - 0.001 mg/kg bw/day. The target hazard quotients of Cd were all lower than 1, indicating low potential non-carcinogenic health risks to residents via the consumption of pepper. Notably, carcinogenic risk values suggested potential adverse health effects to adults, while after considering the bioaccessibility of Cd in pepper (mean of 43.07%), those values had fallen under the acceptable level (1 × 10^-4). This may indicate that dietary risk assessment of heavy metals in crops could not be conducted just based on their content; the bioaccessibility of metals is also an important factor for consideration.

Kindergarten indoor dust metal(loid) exposure associates with elevated risk of anemia in children

Exposure to metals and metalloids in indoor dust is associated with adverse health effects in young children, but there is limited evidence for an association with anemia, which is at high risk in children. The aim of this study was to investigate the association between exposure to multiple metal(loid)s in indoor dust in kindergartens and the risk of anemia in children. In 2021, 2165 children from 25 kindergartens in eastern China were included in the study and had their hemoglobin (Hb) measured. Indoor dust samples were collected from the children's kindergartens, and the concentrations of 11 metals and metalloids in the samples were measured using inductively coupled plasma mass spectrometry (ICP-MS). The daily exposure dose (DED) of dust was used to assess the risk of metal(loid) exposure in the children. The results showed that of the 2165 children with available data, 351 (16.2 %) met the WHO definition of anemia. In multiple linear regression and logistic regression analyses, we found that for each quartile of DED increase in Cd inhalation, child Hb levels decreased by 2.703 g/L (95 % CI: -4.055, -1.351), and the risk of anemia increased 1.602-fold (95 % CI: 1.087, 2.360). Mn ingestion was associated with increased odds of anemia [odds ratio (OR) = 1.760 (95 % CI: 1.217, 2.544)]. Interaction analysis indicated that metal(loid)s exposure effects were modified by child sex, age, and body mass index (BMI). Cluster analysis found that children at high risk of metal(loid) exposure in the school environment tended to have lower Hb levels and higher prevalence of anemia compared with those at low risk, although this was not statistically significant. These findings suggest that child school exposure to metal(loid)s in indoor dust is associated with an increased risk of developing anemia in children, modified by child sex, age, and BMI.

Trace elements in indoor dust-Children's health risk considering overall daily exposure

Indoor dust presents an important source of daily exposure to toxic elements. The present study reports for the first time the levels of Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Sn, Se, Sr, Tl, V, and Zn measured in dust samples collected from 10 kindergartens and 21 cars from Zagreb, Croatia. Based on the obtained data, we assessed the health risks from overall daily exposure to trace elements for children aged 2-6 years taking into account three pathways of dust intake-ingestion, dermal absorption, and inhalation. The median concentration of most elements was significantly higher in dust obtained from cars compared to kindergartens, especially in the cases of Co (11.62 vs. 3.60 mg kg^-1 ), Cr (73.55 vs. 39.89 mg kg^-1 ), Cu (186.33 vs. 26.01 mg kg^-1 ), Mo (8.599 vs. 0.559 mg kg^-1 ), Ni (37.05 vs. 17.38 mg kg^-1 ), and Sn (9.238 vs. 1.159 mg kg^-1 ). Oral intake was identified as the most important exposure pathway, except for Cr, Ni, and Sb where dermal contact was the main route of exposure. Health risk assessment indicated that no adverse effects are expected from overall exposure to trace elements. Although the cases of high exposure to toxic elements are not common in areas with no significant environmental pollutants, due to the health threat they may present even at low levels, their status should be carefully monitored.

Potential ecological and health risks of heavy metals for indoor and corresponding outdoor dust in Hefei, Central China

The harm caused by indoor dust has received increasing attention in recent years. However, current studies have ignored comparisons with the corresponding outdoor dust. This study aimed to investigate the distribution of heavy metals in indoor and corresponding outdoor dust and the ecological and health risks they pose in Hefei, Central China. We analyzed O/I (outdoor/indoor concentration ratios) values, background comparison, and correlation analysis (heavy metal concentrations vs. particle size) and found that Cu, Zn, and Cd mainly existed in indoor sources, while V, Co, and As mainly existed in outdoor sources, and both family sizes and floor number influenced the variation of O/I. Through a new potential ecological risk assessment method, we determined that Cd risk levels in indoor and outdoor dust were extreme and high to extreme, respectively. Additionally, the carcinogenic risks of Ni, As, and Cr were not negligible. The risk of indoor dust was higher than that of outdoor dust for the heavy metals studied, implying a poor indoor environment. Notably, indoor dust from families with smaller sizes, lower floors, and smokers had higher ecological and carcinogenic risks.

Relationship between cumulative exposure to metal mixtures and heart rate among Chinese preschoolers

The cumulative exposure to metals affects cardiac conduction, and the effect of polymetallic exposure on heart rate in children is unknown. To evaluate the relationship between cumulative exposure to metal mixtures and heart rate among Chinese preschoolers, the determination of urinary 24 metals was processed by high-resolution inductively coupled plasma-mass spectrometry. Heart rate was recorded when measuring blood pressure after resting 5 min or longer. As a method to compute the Environmental risk score (ERS) according to heart rate under heavy metal mixtures, adaptive elastic net (AENET) with 299 predictors which were formed by the combination of main effects, squared terms, and pairwise interactions of heavy metals with a total number of 23, 23, 253 respectively. To further assess the associations between ERS and heart rate, regression analyses were performed with complex survey designs. The construction of ERS under heart rate-related metal mixtures was returned by AENET in according to 11 main effects (tin, arsenic, zinc, iron, titanium, vanadium, nickel, manganese, cobalt, copper and chromium) and 2 squared terms (tungsten and rubidium). A high correlation was monitored between the alteration of ERS in the study population and heart rate (β = 1.030, 95% CI: 0.730 - 1.330 in 1239; β = 1.085, 95% CI: 0.777 - 1.393 in 1061). Significant associations of ERS with higher heart rates were also pointed out (Ps < 0.05). Our study elucidates the association of the cumulative exposure of heavy metals as mixtures and heart rate among Chinese preschoolers. Further research is obliged to corroborate these findings in longitudinal studies.

Pollution characteristics, sources and health risk of metals in urban dust from different functional areas in Nanjing, China

Urban dust is an important medium of potential toxic metal (PTM) pollution that affects human health and the urban ecosystems. A total of 374 fugitive dust samples were collected in Nanjing, a fast-developing city in southern China, including six sub-types of dust (residential district, commercial district, industrial district, traffic district, cultural and educational district, green land). Chemical analysis of eighteen metal elements by inductively coupled plasma mass spectrometry was carried out to establish the sub-type sources profiles of fine particles for fugitive dust. The results show that these metals (Cu, Zn, Se, Sr, Mo, Cd, Sb, and Pb) are mainly from anthropogenic sources and present a high degree of pollution; Mn, As, and Ba are moderately affected by human activities and present a significant degree of pollution; Ni, Co, Cr, Tl, V, Be, and Ti mainly originate from natural sources and present significant, moderate and minimal degrees of pollution. For the dust types from different functional areas, the differences of enrichment factor (EF) values were relatively small. Metals were highly concentrated in dust from residential, cultural and educational district, which had high density population and would pose higher health risk. In all types of dust, the metals rich in crust (Ti, Mn, Ba, Sr) and the metals (Cu, Zn, Pb) closely connected with city activities were the main components. Factor analysis revealed that there were six main sources of metals in dust collected from Nanjing: industrial activity, building decoration, soil dust, metal smelting, traffic emissions, and brake abrasion. Generally, noncarcinogenic and carcinogenic health risks of metals found in dust are rarely found for children and adults based on health risk assessments. However, the noncarcinogenic risk of Pb in commercial districts for children should be noted because its hazard quotient was higher than the safety threshold level. For the accumulative health risk of eighteen metals, the noncarcinogenic risk values of dust from six functional areas for children were all over the threshold (1.0), whereas below 1.0 for adults. The difference between children and adults was relatively obvious. All accumulative risk values of carcinogenic metals did not exceed the carcinogenic risk threshold of 1 × 10^-4, which suggested that no risk prevention measures were needed.

Pollution evaluation and children's multimedia exposure of atmospheric arsenic deposition in the Pearl River Delta, China

The populous Pearl River Delta (PRD) region in China suffers from serious air arsenic (As) pollution. The objective of this study was to explore the pollution situation of atmospheric arsenic deposition in the PRD region, and to evaluate the associated multimedia daily intake in children. The average deposition flux was 3921.7 μg/m²/year during the 2016-2017, and the pollution situation was even worse than that in 2015. A continuously increasing trend of arsenic atmospheric deposition was found. The bioaccessibility of As in the settled dust was determined as about 22% by a physiologically based extraction test (PBET). After corrected with the bioaccessibilities of As in the settled dust and food items, the geometry means (GM) value of daily uptake through multimedia ingestion of produce (dust and diet) originated from arsenic atmospheric deposition was 0.23 μg/kg/day for 1- to 6-year-old children. The contribution of the non-dietary oral exposure (settled dust) was negligible and just accounted for only 0.01% of the daily uptake. This estimated value was much lower than those in the literatures, in which the bioaccessibility of As was not taken into account, concluding that the role of the settled dust in the total daily intake may have been overestimated previously. Milk, eggs and freshwater fish were the dominant pathways for children to intake the products derived from atmospheric arsenic deposition. There still be a concern about the high non-carcinogenic and carcinogenic risk by long-term multimedia ingestion. Special care should be considered toward the emission sources of air arsenic, including the coal combustion from industries and construction dust, etc., to reduce the negative effect of air arsenic in children.

Heavy Metals in Indoor Dust Across China: Occurrence, Sources and Health Risk Assessment

In this study, the occurrence of heavy metals including cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), and zinc (Zn) was investigated in indoor dust samples collected from 33 urban and rural areas in 11 provinces, China. The concentrations of the selected heavy metals were determined by an inductively coupled plasma mass spectrometry. The mean concentrations of Zn (166 mg kg^-1), Pb (40.7 mg kg^-1), Cr (19.8 mg kg^-1), Cu (16.9 mg kg^-1), and Cd (2.29 mg kg^-1) in indoor dust are in low or moderate levels compared with other countries or regions. Cd was significantly enriched with the highest enrichment factor of 23.7, followed by Zn, Pb, Cu, and Cr, which were all lower than 3. The concentrations of Pb from Northern China (61.4 mg kg^-1) were significantly higher than those from Southern China (8.88 mg kg^-1). The concentrations of heavy metals in indoor dusts from rural areas were higher than those from urban areas except for Cu. The multivariate analysis of variance revealed that wall cover, fuel types, and air conditioning were dominant factors influencing the levels of heavy metals in indoor dust. Principal component analysis showed that outdoor dust and wall paint were main factors for the high concentrations of Cd, Pb, and Cr, accounting for 40.6% of the total contribution; traffic sources contributed to the high levels of Cu and Zn explained 20.6% of the total variance. The hazard indexes of selected heavy metals were less than 1 and carcinogenic risk value of Cr were between 1.01 × 10^-6 and 1 × 10^-4, indicating minor noncarcinogenic and carcinogenic risks from heavy metals in indoor dust for residents in China. Pb contributed 72.0% and 86.9% to the sum of noncarcinogenic risk values of selected heavy metals for adults and children, respectively. The carcinogenic risk value of Cr was approximately 13-fold higher than that of Cd for both adults and children. Children endured higher risks from heavy metals in indoor dust compared with adults.

Trace elements in two particle size fractions of urban soils collected from playgrounds in Bratislava (Slovakia)

Today, it is proven that the contaminated urban soils are hazardous for the human health. Soil substrates of playgrounds call for special research as they are places where children are directly exposed to soil contaminants. Therefore, the objective of this work was to measure the pseudo-total contents and bioaccessibility of several metals and metalloids (As, Bi, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Sn, V, Zn) in two grain sizes (< 150 μm and < 50 μm) of playground soils in Bratislava city (the capital of Slovakia). The content of metal(loid)s in the soils was controlled by a number of factors, with their increased contents (above 75% percentile or higher) at sites influenced by point sources of pollution (industry and agriculture) or at old sites located in the city centre. Cobalt, Cr, Fe, Mn, Ni and V had relatively uniform contents in soils compared to the other elements. As regression modelling with a categorical variable confirmed, the age of urban areas influenced the accumulation of As, Bi, Cd, Cu, Hg, Pb, Sb and Sn in playground soils. Exploratory statistical techniques with compositionally transformed data (principal component analysis, cluster analysis and construction of symmetric coordinates for correlation analysis) divided trace elements into the two main groupings, Co, Cr, Fe, Mn, Ni, V and Bi, Cd, Cu, Hg, Pb, Sb, Sn, Zn. Median concentrations of the elements in smaller soil grains (< 50 μm) were significantly higher than in coarser grains (< 150 μm). Cobalt, Cu, Mn, Pb, Sn and Zn had significantly higher bioaccessible proportions (% of the pseudo-total content) in < 50 μm soil size than in < 150 μm; however, the same order of bioaccessibility was achieved in both grain sizes. The highest bioaccessibility had Cd, Cu, Pb and Zn (~ 40% and more), followed by Co, As, Mn, Sb (18-27%), Hg, Ni, Sn (10-12%) and finally Cr, Fe and V (less than 4%). The hazard index and carcinogenic risk values were higher in < 50 μm than in < 150 μm and significantly decreased in the two soil sizes when the bioaccessibility results were included in the health hazard calculation.