Methodological factors influencing inhalation bioaccessibility of metal(loid)s in PM2.5 using simulated lung fluid

Metal(loid) bioaccessibility and risk assessment of ashfall deposit from Popocatépetl volcano, Mexico

Ash emission from volcanic eruptions affects the environment, society, and human health. This study shows the total concentration and lung bioaccessible fraction of eight potential toxic metal(loid)s in five Popocatépetl ashfall samples. Mineralogical phases and particle size distribution of the ashfall were analyzed by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) techniques, respectively. The bioaccessibility test of Gamble solution (GS) and Artificial Lysosomal Fluid (ALF) were conducted to simulate extracellular (pH 7) and intracellular (pH 4.5) conditions, respectively. The studied metal(loid)s showed the following total concentration (mg kg-1): 1.98 (As), 0.17 (Cd), 134.09 (Cr), 8.66 (Cu), 697.33 (Mn), 55.35 (Ni), 8.77 (Pb), and 104.10 (Zn). Geochemical indices suggested that some metal(loid)s are slightly enriched compared to the local soil background concentrations. Several mineralogical phases were identified in the collected ashfall deposits, such as plagioclase, pyroxene, and Fe-Ti oxide, among others. According to the risk assessment results, the non-carcinogenic risk related to ashfall exposure returns an HQ > 1 for children. In contrast, the estimation of carcinogenic risk was found to be within the tolerable limit. Metal(loid)s showed low bioaccessibility (< 30%) in GS and ALF, with the highest values found in ALF solution for As (12.18%) and Cu (7.57%). Despite their metal-bioaccessibility, our findings also showed that dominant ash particle size ranged between fine (< 2.5 μm) and extremely fine (< 1 μm), considered highly inhalable fractions. The results obtained in this work indicate that volcanic ashes are bioinsoluble and biodurable, and exhibit low bioaccessibility when in contact with lung human fluids.

Arsenic, cadmium, lead, antimony bioaccessibility and relative bioavailability in legacy gold mining waste

Bioaccessibility and relative bioavailability of As, Cd, Pb and Sb was investigated in 30 legacy gold mining wastes (calcine sands, grey battery sands, tailings) from Victorian goldfields (Australia). Pseudo-total As concentration in 29 samples was 1.45-148-fold higher than the residential soil guidance value (100 mg/kg) while Cd and Pb concentrations in calcine sands were up to 2.4-fold and 30.1-fold higher than the corresponding guidance value (Cd: 20 mg/kg and Pb: 300 mg/kg). Five calcine sands exhibited elevated Sb (31.9-5983 mg/kg), although an Australian soil guidance value is currently unavailable. Arsenic bioaccessibility (n = 30) and relative bioavailability (RBA; n = 8) ranged from 6.10-77.6% and 10.3-52.9% respectively. Samples containing > 50% arsenopyrite/scorodite showed low As bioaccessibility (<20.0%) and RBA (<15.0%). Co-contaminant RBA was assessed in 4 calcine sands; Pb RBA ranged from 73.7-119% with high Pb RBA associated with organic and mineral sorbed Pb and, lower Pb RBA observed in samples containing plumbojarosite. In contrast, Cd RBA ranged from 55.0-67.0%, while Sb RBA was < 5%. This study highlights the importance of using multiple lines of evidence during exposure assessment and provides valuable baseline data for co-contaminants associated with legacy gold mining activities.

Exposure to phagolysosomal simulated fluid altered the cytotoxicity of PET micro(nano)plastics to human lung epithelial cells

The occurrence of micro(nano)plastics into various environmental and biological settings influences their physicochemical and toxic behavior. Simulated body fluids are appropriate media for understanding the degradation, stability, and interaction with other substances of any material in the human body. When the particles enter the human body via inhalation, which is one of the avenues for micro(nano)plastics, they first come into contact with the lung lining fluid under neutral conditions and then are phagocytosed under acidic conditions to be removed. Therefore, it is important to examine the physicochemical transformation and toxicity characteristics after interaction with phagolysosomal simulant fluid (PSF). Here, we focused on exploring how the physicochemical differences (e.g. surface chemistry, elemental distribution, and surface charge) of micro(nano)plastics under pH 4.5 phagolysosome conditions impact cytotoxicity and the oxidative characteristics of lung epithelia cells. The cytotoxicity of lung epithelia cells to those treated with PSF and non-treated micro(nano)plastics was tested by various viability indicators including cell counting kit-8 (CCK-8), MTT, and LDH. Furthermore, the cytotoxicity background was examined through the oxidative processes (e.g. reactive oxygen species, antioxidant, superoxide dismutase (SOD), catalase, and reduced glutathione). The results showed that all tested surface physicochemical characteristics were significantly influenced by the phagolysosome conditions. The staged responses were observed with the treatment duration, and significant changes were calculated in carbonyl, carbon-nitrogen, and sulfonyl groups. Moreover, the negativity of the zeta potentials declined between exposure of 2-40 h and then increased at 80 h compared to control owing to the chemical functional groups and elemental distribution of the plastic particles. The tested viability indicators showed that the micro(nano)plastics treated with PSF were cytotoxic to the lung epithelia cells compared to non-treated micro(nano)plastics, and SOD was the dominant enzyme triggering cytotoxicity due to the particle degradation and instability.

Integrating multiple spheres to identify the provenance and risk of urban dust and potentially toxic elements: Case study from central Mexico

This study aims to improve the current method of studying potentially toxic elements (PTEs) in urban dust using direct chemical evidence (from dust, rock, and emission source samples) and robust geochemical methods. The provenance of urban dust was determined using rare earth elements (REEs) and geochemical diagrams (V-Ni-Th*10, TiO2 vs. Zr, and Zr/Ti vs. Nb/Y). The geogenic or anthropogenic source of PTEs was determined using the enrichment factor (EF) and compositional data analysis (CoDA), while a PTE's point emission source was identified using a 3.1*La-1.54*Ce-Zn diagram, mineralogy, and morphology analyses. The spatiotemporal distribution of PTEs was determined using a geographic information system, and their health risk (by inhalation) was estimated using a lung bioaccessibility test and particle size distribution. We collected urban dust (n = 38), rock (n = 4), and zinc concentrate (n = 2) samples and determined PTEs and REEs in a city of 1.25 million inhabitants in central Mexico. Results showed that urban dust derived from the San Miguelito Range. REEs, Sc, and Zr were geogenic, while Mn, Cu, Zn, As, and Pb were anthropogenic. Due to the presente of sphalerite particles, a zinc refinery was identified as the point emission source of Zn, As, and Pb. High concentrations of Zn (5000-20,008 mg/kg), As (120-284 mg/kg), and Pb (350-776 mg/kg) were found in urban dust near the zinc refinery. Additionally, particles of PM2.5 (66-84%), PM5.0 (13-27%), PM10 (3-8%), and PM20 (0-2%) and lung bioaccessibility of Sr (48.5-72.4%), Zn (9.6-28.4%), Cu (10.5-27.0%), Fe (4.5-8.6%), Mn (2.9-9.2%), Cr (38.3%) and Pb (30.6%) demonstrated a latent risk to human health. These approaches improve our understanding of the provenance of urban dust and its PTE emission sources in urban areas.

Characterizing the interaction between micro(nano)plastics and simulated body fluids and their impact on human lung epithelial cells

Micro(nano)plastics are considered an emerging threat to human health because they can interact with biological systems. In fact, these materials have already been found in the human body, such as in the lungs. However, limited data are available on the behavior of these materials under biological conditions and their impact on human cells, specifically on alveolar epithelial cells. In this study, micro(nano)plastics were exposed to various simulated biological fluids (artificial lysosomal fluids and Gamble's solution) for 2-80 h. Pristine and treated plastic particles were characterized based on their surface chemistry, zeta potentials, and elemental composition. Various toxicological endpoints (mitochondrial membrane potential, lactate dehydrogenase, protein, and antioxidant levels) were examined using A549 lung carcinoma cells. The surface characteristics of the treated micro(nano)plastics and the toxicological endpoints of A549 cells were found to be influenced by the simulated biological media, specifically with high concentrations of the treated micro(nano)plastics and increasing exposure under biological conditions. Moreover, the toxicological endpoints were strongly linked to the chemistry of plastics and included multiple processes in response to the plastics; different biological pathways were obtained in artificial lysosomal fluid and Gamble's solution.

PM2.5-bound trace metals in an urban area of Northern Mexico during the COVID-19 pandemic: characterization, sources, and health risk

Abstract

A field study was carried out in the Metropolitan Area of Monterrey (MAM), the second most populated city in Mexico, characterized by increasing urbanization, high traffic density, and intense industrial activity. These characteristics commonly present high concentrations of air pollutants leading to the degradation of air quality. PM2.5 was analyzed for heavy metals at two urban sites located within the MAM (Juarez and San Bernabe) in order to determine sources, health risk, morphology, and elemental content during the COVID-19 pandemic (autumn 2020 and spring 2021). Twenty-four-hour samples of PM2.5 were collected at each site during 30-day periods using high-volume equipment. Gravimetric concentrations and 11 metals were measured (Ca, Cd, Co, Cu, Fe, K, Mg, Mn, Ni, Cr, and Pb) by different analytical techniques (flame atomic absorption spectroscopy, graphite furnace atomic absorption spectroscopy, and inductively coupled plasma optical emission spectroscopy). Selected samples were analyzed by scanning electron microscopy-energy-disperse spectroscopy in order to characterize their morphology and elemental content. PM2.5 concentrations exceeded the Mexican standard and WHO guidelines in Juarez during spring 2021. Cu, Cd, and Co were highly enriched by anthropogenic sources, and Ni, K, Cr, and Pb had a moderate enrichment. Mg, Mn, and Ca were of crustal origin. Bivariate statistics and PCA confirmed that alkaline metals originated from crustal sources and that the main sources of trace metals included traffic emissions, resuspension from soil/road dust, steel industry, smelting, and non-exhaust emissions at both sites. Lifetime cancer risk coefficients did not exceed the permissible levels established by EPA and WHO, implying that local residents are not at risk of developing cancer. Non-carcinogenic risk coefficients revealed that there is a possible risk of suffering cardiovascular and respiratory diseases due to inhalation of cobalt at the study sites.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11869-023-01372-7.

Incorporating Bioaccessibility into Inhalation Exposure Assessment of Emamectin Benzoate from Field Spraying

The inhalation exposure of pesticide applicators and residents who live close to pesticide-treated fields is a worldwide concern in public health. Quantitative assessment of exposure to pesticide inhalation health risk highlights the need to accurately assess the bioaccessibility rather than the total content in ambient air. Herein, we developed an in vitro method to estimate the inhalation bioaccessibility of emamectin benzoate and validated its applicability using a rat plasma pharmacokinetic bioassay. Emamectin benzoate was extracted using the Gamble solution, with an optimized solid-to-liquid ratio (1/250), extraction time (24 h), and agitation (200 rpm), which obtained in vitro inhalation bioaccessibility consistent with its inhalation bioavailability in vivo (32.33%). The margin of exposure (MOE) was used to assess inhalation exposure risk. The inhalation unit exposures to emamectin benzoate of applicators and residents were 11.05-28.04 and 0.02-0.04 ng/m³, respectively, varying markedly according to the methods of application, e.g., formulations and nozzles. The inhalation risk assessment using present application methods appeared to be acceptable; however, the MOE of emamectin benzoate might be overestimated by 32% without considering inhalation bioaccessibility. Collectively, our findings contribute insights into the assessment of pesticide inhalation exposure based on bioaccessibility and provide guidance for the safe application of pesticides.

Inhalation bioaccessibility of inhaled triazole fungicides and health risk assessment during spraying

BACKGROUND

Ambient air pollution caused by pesticide drift has received great attention. To accurately evaluate the health risk of inhaled pesticides, bioaccessibility should be considered. However, methods to reliably assess pesticide residues remain limited, hindering the precise estimation of exposure assessment. We aimed to optimize an in vitro method for the inhalation bioaccessibility (IBA) measurement of triazole fungicides and to incorporate this into inhalation exposure assessment during pesticide spraying.

RESULTS

The IBA of triazole fungicides increased logarithmically with extraction duration, plateauing after 6 h. The frequency of agitation displayed a similar pattern, whereas the ratio of solid to liquid between 1/1500 and 1/250 was considerably negatively associated. The predicted values (35.9-53.5%) for IBA based on optimized methodological parameters determined using a response surface methodology showed an acceptable deviation from experimental values (30.7-50.8%), suggesting feasibility for in vitro IBA measurement. Incorporating IBA into calculations of inhalation exposure amount (IE) yielded a value of 8.5 × 10^-7 -2.1 × 10^-5  mg kg^-1  day^-1 , a 50-68% reduction compared to IE based on total amount. Additionally, the safety exposure threshold was determined for triazole fungicides using benchmark dose modelling of data from lung A549 cell proliferation toxicity assays, and in this context, margin of exposure (MOE) values were calculated to be within an acceptable level.

CONCLUSION

This in vitro method supplements bioaccessibility evaluation based on pesticide inhalation exposure, along with the risk to human health. © 2023 Society of Chemical Industry.

Heavy metal content and health risk assessment of atmospheric particles in China: A meta-analysis

In recent decades, China has devoted significant attention to the heavy metals pollution in particulate matter. However, the majority of studies have only focused on the field monitoring in relatively remote areas, which may not be representative of air quality across the country. This study reevaluated the characteristics, temporal and spatial changes, and health concerns associated with heavy metal pollution in atmospheric particulates on a national scale by coupling Meta-analysis and Monte Carlo simulation analysis. In terms of spatial distribution, the heavy metals pollution levels in the northern coast and northeastern regions are relatively high, whereas it is low along the middle Yellow River, middle Yangtze River, as well as Southwest. With the exception of Cu, the distribution of all elements in PM2.5 steadily decreased over time Moreover, PM10 and PM2.5 performed similar where Cd and Ni both first increased followed by a decline while, Cr displayed a decrease before it showed an increment. And since the implementation of prevention and control policies about the atmospheric release, the focus of industrial emission has gradually shifted from energy production and processing to living products manufacturing. Moreover, the carcinogenic risk was shown to be Cr > As, Pb > Ni, Cd, while the non-carcinogenic risk was as follows: As, Ni > Cr, Cd. Among all contaminants, Cd, As, and Cr in PM2.5 and PM10 exceeded the WHO standard in the cities with worst air quality. It was observed that As posed the largest non-carcinogenic risk to adults while, Cr caused the most carcinogenic risk to adults and children, where the carcinogenic risk of children remains higher than that of adults. Therefore, the findings of this study may offer data support to the China's heavy metal pollution standards in airborne particles and offer theoretical data support for pollution management.

Bioaccessibility of Pb in health-related size fractions of contaminated soils amended with phosphate

Lead (Pb) contamination is one of the most significant exposure hazards to human health. Contaminated soil particles may be eroded and transferred either to the atmosphere (<10 μm) or to streams; or they may be incidentally ingested (<200 μm). Among strategies for the long-term management of this risk, one of the most cost-effective is the reduction of Pb mobility and bioavailability via amendment with phosphorus-containing materials. To clarify the effectiveness of P amendment in reducing Pb mobility and bioaccessibility in different soil size fractions, an experiment was performed by adding a soluble P compound to a historically contaminated urban soil (RO), a mining soil (MI), and an uncontaminated spiked soil (SP) at different P:Pb molar ratios (2.5:1, 5:1, and 15:1). In the <10 μm fraction of soils, P addition reduced bioaccessible Pb only in the SP soil at the highest dose, with little to no effect on RO and MI soils. Similarly, in the coarse fraction, Pb was immobilized only in the SP soil with all three P doses. These results were probably due to the higher stability of Pb in historically contaminated soils, where Pb dissolution is the limiting factor to the formation of insoluble Pb compounds. The bioaccessible proportion of Pb (using SBET method) was higher than 70 % of the total Pb in all soils and was similar in both fine and coarse particle fractions. Due to the enrichment of Pb in finer particles, this implies possible adverse effects to the environment or to human health if these particles escape from the soil. These results call for increasing attention to the effect of remediation activities on fine soil particles, considering their significant environmental role especially in urban and in historically low or moderately contaminated areas.

Sub-cellular sequestration of alkaline drugs in lysosomes: new insights for pharmaceutical development of lysosomal fluid

Background and purpose

Lysosomal-targeted drug delivery can open a new strategy for drug therapy. However, there is currently no universally accepted simulated or artificial lysosomal fluid utilized in the pharmaceutical industry or recognized by the United States Pharmacopeia (USP).

Experimental procedure

We prepared a simulated lysosomal fluid (SLYF) and compared its composition to a commercial artificial counterpart. The developed fluid was used to test the dissolution of a commercial product (Robitussin^®) of a lysosomotropic drug (dextromethorphan) and to investigate in-vitro lysosomal trapping of two model drugs (dextromethorphan and (+/-) chloroquine).

Findings/Results

The laboratory-prepared fluid or SLYF contained the essential components for the lysosomal function in concentrations reflective of the physiological values, unlike the commercial product. Robitussin^® passed the acceptance criteria for the dissolution of dextromethorphan in 0.1 N HCl medium (97.7% in less than 45 min) but not in the SLYF or the phosphate buffer media (72.6% and 32.2% within 45 min, respectively). Racemic chloroquine showed higher lysosomal trapping (51.9%) in the in-vitro model than dextromethorphan (28.3%) in a behavior supporting in-vivo findings and based on the molecular descriptors and the lysosomal sequestration potential of both.

Conclusion and implication

A standardized lysosomal fluid was reported and developed for in-vitro investigations of lysosomotropic drugs and formulations.

Dissolution Behaviour of Metal-Oxide Nanomaterials in Various Biological Media

Toxicological effects of metal-oxide-engineered nanomaterials (ENMs) are closely related to their distinct physical-chemical properties, especially solubility and surface reactivity. The present study used five metal-oxide ENMs (ZnO, MnO₂, CeO₂, Al₂O₃, and Fe₂O₃) to investigate how various biologically relevant media influenced dissolution behaviour. In both water and cell culture medium (DMEM), the metal-oxide ENMs were more soluble than their bulk analogues, with the exception that bulk-MnO₂ was slightly more soluble in water than nano-MnO₂ and Fe₂O₃ displayed negligible solubility across all tested media (regardless of particle size). Lowering the initial concentration (10 mg/L vs. 100 mg/L) significantly increased the relative solubility (% of total concentration) of nano-ZnO and nano-MnO₂ in both water and DMEM. Nano-Al₂O₃ and nano-CeO₂ were impacted differently by the two media (significantly higher % solubility at 10 mg/L in DMEM vs. water). Further evaluation of simulated interstitial lung fluid (Gamble's solution) and phagolysosomal simulant fluid (PSF) showed that the selection of aqueous media significantly affected agglomeration and dissolution behaviour. The solubility of all investigated ENMs was significantly higher in DMEM (pH = 7.4) compared to Gamble's (pH 7.4), attributable to the presence of amino acids and proteins in DMEM. All ENMs showed low solubility in Gamble's (pH = 7.4) compared with PSF (pH = 4.5), attributable to the difference in pH. These observations are relevant to nanotoxicology as increased nanomaterial solubility also affects toxicity. The results demonstrated that, for the purpose of grouping and read-across efforts, the dissolution behaviour of metal-oxide ENMs should be evaluated using aqueous media representative of the exposure pathway being considered.

Increased allergic and asthmatic risks in children residing in industrial areas by surveying the pre-inflammatory (IgE, IL-4 and IL-13) biomarkers

Toxic metal(loid)s can lead to high damages on human. This work was conducted to investigate the levels of metal(loid)s in PM2.5 and a total of 123 male children's (aged 6-9 years) blood chosen from different areas in Ahvaz and their association with the pre-inflammatory (Immunoglobulin E and cytokines: IgE, IL-4 and IL-13) responses in serum cells. Six metal(loid)s (arsenic, cadmium, chromium, mercury, nickel and lead) in three regions including industrial (Padad), vehicle traffic (Golestan) and reference (Kianpars) areas were studied. Results showed the concentrations of As, Cr, Cd, Ni and Hg in the ambient air of industrial area (Padad) (P < 0.001), and Pb in vehicle traffic area (Golestan) were higher (p < 0.001). Moreover, the mean levels of IgE (mean = 146.44 pg/200landa, P < 0.003), IL-4 (mean = 548.23 pg/200landa, P < 0.001) and IL-13 (mean = 53.21 pg/200landa, P < 0.001) in Padad were higher than Golestan and Kianpars. Our results suggest that living in industrial areas leads to accelerated synthesis of IgE, IL-4 and IL-13 in blood. The spatial distribution of children's serum IgE, IL-4 and IL-13 concentrations showed an abnormal increase of 240 to 400 pg/200landa for IgE, 950 to 1400 pg/200landa for IL-4 and 90 to 128 pg/200landa for IL-13. Our results indicate children in the industrial area are prone to asthma, allergy, miRNA mutation, and other chronic diseases.

In vitro and in silico bioaccessibility of urban dusts contaminated by multiple legacy sources of lead (Pb)

Lead contamination from gasoline, paint, pesticides, and smelting have unique chemical structures. Recent investigations into Pb speciation in urban soils and dusts from multiple sources have revealed emerging forms which differ from the initial sources. This results from reactions with soil constituents leading to transformation to new forms for which the bioaccessibilities remain uninvestigated. We investigated the in vitro and in silico bioaccessibility of these emerging forms in three physiologically relevant milieux: artificial lysosomal fluid (ALF), simulated epithelial lung fluid (SELF), and simulated gastric fluid (SGF). Species were validated using extended X-ray absorption fine structure spectroscopy. Results highlight diverse bioaccessibilities which are form and compartmentally-dependent. In ALF the bioaccessibility trend was humate-bound Pb (86%) > hydrocerussite (79%) > Fe oxide-bound Pb (47%) > galena (10%) > pyromorphite (4%) > Mn oxide-bound Pb (2%). Humate-bound Pb, hydrocerussite, Fe and Mn oxide-bound Pb were 100% bioaccessible in SGF while pyromorphite and galena were 26%, and 8%, respectively. Bioaccessibility in SELF was very low (< 1%) and significantly lower than ALF and SGF (p < 0.001). In silico bioaccessibilities modeled using equilibrium solubilities in extraction solutions were in good agreement with empirical measurements. These emerging forms of Pb have a wide range of bioaccessibilities that can influence their toxicity and impact on human health.

Interaction of nanoplastics with simulated biological fluids and their effect on the biofilm formation

Over the last decade, it has become clear that the pollution by plastic debris presents global societal, environmental, and human health challenges. Moreover, humans are exposed to plastic particles in daily life and very limited information is available concerning human health, especially interactions with biological fluids. Therefore, the aim of this study is to investigate the interaction of plastic particles with simulated biological fluids (e.g., artificial saliva, artificial lysosomal fluid, phagolysosomal simulant fluid, and Gamble's solution) using various exposure stages (2 h to 80 h) and the effect of plastic particles on the formation of Staphylococcus aureus biofilms under simulated biological conditions. The plastic particles incubating various simulated biological fluids were characterized using surface functional groups, zeta potentials, and elemental composition. The results indicated that functional group indices (C-O, C = O, C-H, C = C, C-N, S = O, and OH) decreased compared to the control group during the incubation periods, except for the hydroxyl group index. The FTIR results showed that the hydroxyl group formed with the artificial lysosomal fluid, the phagolysosomal simulant fluid, and Gamble's solution. With the impact of the declining functional groups, the zeta potentials were more negative than in the control. Moreover, EDX results showed the release of the components in the particles with the interaction of simulated biological fluids as well as new components like P and Ca introduced to the particles. The biofilms were formed in the presence of nanoplastic particles under both controlled conditions and simulated biological conditions. The amount of biofilm formation was mainly affected by the surface characteristics under simulated biological conditions. In addition, the biofilm characteristics were influenced by the O/C and N/C ratios of the plastic particles with the impact of simulated biological fluids.

Novel insights into probabilistic health risk and source apportionment based on bioaccessible potentially toxic elements around an abandoned e-waste dismantling site

The study of potentially toxic element (PTE) hazards around e-waste recycling areas has attracted increasing attention but does not consider elemental bioaccessibility. Here, the respiratory and oral bioaccessibilities were incorporated into probabilistic health risk evaluation and source contribution apportionment. The results showed that soil Cd yielded the highest respiratory and oral bioaccessibility, whereas Cr in soils and vegetables attained the lowest oral bioaccessibility. When incorporating metal bioaccessibility into health risk assessment, a 48.3%-55.7% overestimation of non-cancer and cancer risks can be avoided relative to the risk assessment based on the total concentrations of PTEs. More importantly, priority control metals were misidentified without consideration of bioaccessibility. Cadmium, As, and Cr were screened as the priority metal(loid)s for targeted risk control based on the total PTEs, whereas Cd, Zn, and Cu were the priority metal(loid)s based on the bioaccessible PTEs. Furthermore, source apportionment revealed that >50% of oral bioaccessible Cd, Cu, Ni, Pb, and Zn in farmland were contributed by e-waste dismantling activities, whereas bioaccessible As and Cr mainly originated from agrochemical applications and natural sources, respectively. This study emphasizes the refinement of risk estimation and source apportionment through metal bioaccessibility adjustment, which facilitates the realistic assessment of adverse health effects in humans and the precise identification of high-risk sources.

Assessment and source apportionment of water-soluble heavy metals in road dust of Zhengzhou, China

The water-soluble concentration of heavy metals in road dust poses a considerable hazard to public health. The primary goals of the study were estimation of water-soluble contents of heavy metal, estimation of pollution indices, and source apportionment of water-soluble contents of heavy metals using UNMIX model from the road dust of Zhengzhou city. To accomplish this, inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used to determine concentrations of eight heavy metals (Cr, Cu, Ni, Zn, Cd, As, Pb, and Hg), and it has been observed that Cu and Zn were the metals with the highest concentration, while Hg, Cd, and Pb were in the lowest concentration range of metals. Pollution indices, geo-accumulation index (I_geo), contamination factor (CF), and Nemerow synthetic pollution index (PI_N) were calculated to assess the contamination level of water-soluble contents of these hazardous heavy metals. I_geo classified the contamination risk into a spectrum of categories ranging from unpolluted (Cr and Pb) to high polluted (Cu and Cd). For the CF results, the concentration of Cr and Pb was found to be low, similar to I_geo, while the concentrations of three heavy metals, Cu, Cd, and Hg, were found to be extremely high or excessive. The results of the PI_N assessment indicated that there was an enormous risk of Hg contamination in the city and that Cu, Cd, and Zn were all within a few percent of the Hg pollution level and hence fell into the high pollution group. The UNMIX model was used for source apportionment of dissolved heavy metals and showed: Source 1 (natural sources, 10%), Source 2 (copper mine tailing contamination, 19%), and Source 3 (agricultural activities22%). Source 4 accounted for (air pollution, 15%) of the total and Source 5 accounted for (industrial activity, 34%). It is imperative that immediate and comprehensive pollution control and preventive measures be implemented in the city due to the presence of metal in the dust.

Potential Heavy Metals Pollution Contribution from Wash-Off of Urban Road-Dust

Based on the different particle sizes of street dust, the potential pollution load of heavy metals from dry and wet atmospheric deposition to surface runoff in different functional areas of Zhengzhou city was estimated by using the rain-scour heavy metal index model. Compared to the EA, IA, and CA areas, RA and PA have a higher potential contribution to heavy metal runoff pollution from Road deposited sediments (RDS) than the other watersheds. Zhengzhou utilized the RDS index model to calculate pollution loads in various areas around Zhengzhou (EA, IA, CA, PA, and RA). In the different land-use areas, the RDS indices for pollutant load (RDSindex,load) and pollutant strength (RDSindex,strength) varied greatly, and the RDS index strength values increased. RDSindex,load fell in the following order: IA > RA > PA > EA. Because the RDS index incorporates RDS characteristics such as the amount of RDS, grain sizes present, RDS mobility, and associated metals, the RDSindex,load and RDSindex,strength results did not merely match variability in the amounts of RDS found or metal concentrations in the RDS in various land-use areas. Metal’s presence in the dust is a direct health risk for humans and warrants immediate and effective pollution control and prevention measures in the city.

Human health risk assessment of PM2.5-bound heavy metal of anthropogenic sources in the Khon Kaen Province of Northeast Thailand

The study aimed to assess the human health risk of PM_2.5-bound heavy metals from anthropogenic sources in Khon Kaen Province, Thailand between December 2020 and February 2021. According to the findings, the geometric mean concentration of PM_2.5 in the university area, residential area, industrial zone, and the agricultural zone was 32.78 μg/m³, 50.25 μg/m³, 44.48 μg/m³, and 29.53 μg/m³, respectively. The results showed that the estimated human health risk assessment, in terms of non-carcinogenic risks among children and adults in an urban area (residential and university), industrial zone, and the agricultural area, was of hazard index (HI) value of >1.0 indicating a greater chance of chronic effects occurring. This study showed that exposure to PM_2.5-bound heavy metal may increase the likelihood that lasting effects will result in a very high carcinogenic risk (CR) in children in residential areas, and an industrial zone with total carcinogenic risk (TCR) values of 0.23×101, and 0.12×101, respectively while resulting in a high TCR of 3.34×10−2 and 4.11×10−2 within the university areas and agricultural zone, respectively. In addition, health risk assessments among adults demonstrate high TCR values of 4.40×10−1 (residential area), 2.28×10−1 (industrial zone), and 7.70×10−3 (agricultural zone), thus indicating a potential health risk to adults living in these areas while the university area was very low effects on carcinogenic risk (CR≤10−8) for adults. Therefore, lowering the risk of exposure to PM_2.5 via the respiratory tract, for example, wearing a mask outside is a very effective self-defense strategy for people within and around the study site. This data study strongly supports the implementation of the air pollutant emission source reduction measures control and health surveillance.

Effect of ambient air PM2.5-bound heavy metals on blood metal(loid)s and children's asthma and allergy pro-inflammatory (IgE, IL-4 and IL-13) biomarkers

BACKGROUND

We investigated the concentrations of metals in fine particulate matter PM_2.5 in the outdoor air around the home sites of 123 male children from Ahvaz, average age 7.56, along with their blood samples to measure pro-inflammatory responses (Immunoglobulin E and cytokines: IgE, IL-4 and IL-13).

METHODS

We measured 6 metals (As, Cd, Cr, Hg, Ni and Pb) in three Ahvaz's regions including industrial (Padad), vehicle traffic (Golestan) and control (Kianpars).

RESULTS

The higher concentrations of metals in the Padad as the industrial ambient air i.e., arsenic, cadmium, chromium, mercury and nickel coincided with the higher concentrations of those metals in exposed children (P < 0.05) versus the controls. Children in Golestan, the high traffic air pollution area had the highest lead concentrations (p < 0.05). Also a significant association was shown in Padad between blood arsenic and IgE (β = 26.59, P < 0.001), IL-4 (β = 172.1, P < 0.001) and IL-13 (β = 14.84, P < 0.001), blood chromium and IgE (β = 10.38, P < 0.001), IL-4 (β = 75.27, P < 0.001) and IL-13 (β = 5.27, P < 0.001) and blood mercury and IgE (β = 13.11, P < 0.001), IL-4 (β = 108.09, P < 0.001) and IL-13 (β = 7.96, P < 0.001) and blood lead and IgE(β = 0.92, P = 0.025), IL-4(β = 7.16, P < 0.001) and IL-13(β = 0.58, P = 0.003). However, no significant relation was found for Cadmium, Nickel in blood with IgE, IL-4 and IL-13 levels. Moreover, children from industrial areas showed significantly higher concentrations of IgE (mean = 146.44 pg/200landa, P < 0.001), IL-4 (mean = 548.23 pg/200landa, P < 0.001) and IL-13 (mean = 52.93 pg/200landa, P < 0.001) versus Golestan and Kianpars.

CONCLUSION

Children residing in an industrial area with high concentrations of metals in PM_2.5 had high metals in blood and high production of IgE, IL-4 and IL-13, reflecting an immune dysregulation and brisk inflammatory responses.

Biomonitoring and bioaccessibility of environmental airborne manganese in relation to motor function in a healthy adult population

BACKGROUND/AIM

Santander, the capital of Cantabria, Spain (172,000 inhabitants) is 7 km from an industrial emission source (IES) of Mn located in a 10,000 inhabitants town (Maliaño) (annual air Mn arithmetic mean = 231.8 ng/m³; reference WHO guideline = 150 ng/m³). Our objective was to compare the motor function of adult healthy volunteers living in both places.

METHODS

Cross-sectional study analyzing 130 consecutive participants. Exposure to Mn was assessed in terms of source distance from the IES, by Personal Environmental Monitors (PEMs) carried for 24 h by participants consisting of a portable impactor connected to a personal pump, and by biomarkers (blood, hair and fingernails). The impactor allowed the separation of fine (PM2.5) and coarse (PM10-2.5) particles and for each particle size in-vitro bioaccessibility tests with biologically active fluids were performed to separate the soluble (bioaccessible) from the insoluble (non-bioaccessible) fraction. Mean Differences (MDs) adjusted for age, sex, and study level, were obtained for motor function tests results.

RESULTS

Regarding Grooved Pegboard, overall mean time to complete the test was 59.31 and 65.27 seconds (Standard Deviation = 10.11 and 11.69) for dominant and nondominant hands respectively. Statistically significant higher times (indicating worse function) were observed when living near the IES in both hands but MDs of only 1.22 and 2.05 seconds were obtained after adjusting for the predefined confounders (p = 0.373 and 0.221 respectively). Regarding Mn levels in their PEMs (in both bioaccessible and non-bioaccessible coarse&fine fractions) higher times were computed in participants with higher levels for the bioaccessible-fine fraction, with a MD that diminished but still yielded statistical significance after controlling for confounding: adjusted MD = 3.01 more seconds; 95%CI (0.44-5.38), p = 0.022. Poorer results were also observed for fingernails levels. Regarding Finger Tapping Test, no statistically significant differences were found with the exception of Mn fingernails levels.

CONCLUSIONS

Our results suggest poorer motor function as assessed by Grooved Pegboard test in relation to "proximity to IES", "bioaccessible-fine fraction as determined by PEMs and "Mn fingernails levels". However, our findings were affected by confounding, and only the adjusted MD for the Mn bioaccessible-fine fraction remained of sufficient magnitude to maintain statistical significance.

Health risk assessment via ingestion and inhalation of soil PTE of an urban area

Potentially Toxic Elements (PTE) are common soil contaminants and pose a significant risk to human health. In this study, ingestion (<150 μm) and inhalation (<10 μm) bioaccessibility and human health risk due to PTE were investigated in soils of the urban and peri-urban area of Torino. Lead, Cd, Cu, and Zn were observed to be the most soluble elements in simulated gastric and lung fluids. Higher bioaccessible concentrations of Pb, Ni, Co and Sb were observed in the inhalable size fraction (<10 μm) compared to ingestible one probably because of the higher concentration in fine soil size fraction. Conversely, the relative bioaccessibility of Pb, Cu, Cd, Zn and As was lower, due to the different extracting conditions and to the presumable different elemental speciation. Average values suggested that PTE would be more bioavailable if ingested than inhaled, particularly in urban areas, were the bioaccessible percentages were always higher than in peri-urban sites. Health risk assessment was conducted using bioaccessible concentrations and their corresponding toxicities via ingestion and inhalation exposures. Unacceptable non-carcinogenic risk (HQ > 1) was found through ingestion exposure for children in some urban sites and Pb was the most hazardous elements. Carcinogenic risks were under the threshold levels for every soil (CR < 10^-4), with Cr and As being the dominant contributors to risk. Therefore, necessary soil remediation activities are needed to reduce the risks of human, especially for children, exposure to Pb.

Human Health Risk Assessment of Heavy Metals in the Urban Road Dust of Zhengzhou Metropolis, China

The goal of this research is to assess hazardous heavy metal levels in PM2.5 fractioned road dust in order to quantify the risk of inhalation and potential health effects. To accomplish this, Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) was used to determine concentrations of eight heavy metals (Cr, Cu, Ni, Zn, Cd, As, Pb, and Hg) in the PM2.5 portion of road dust samples from five different land use areas (commercial, residential, industrial, parks, and educational) in Zhengzhou, China. The following were the average heavy metal concentrations in the city: Cr 46.26 mg/kg, Cu 25.13 mg/kg, Ni 12.51 mg/kg, Zn 152.35 mg/kg, Cd 0.56 mg/kg, As 11.53 mg/kg, Pb 52.15 mg/kg, and Hg 0.32 mg/kg. Two pollution indicators, the Pollution Index (PI) and the Geoaccumulation Index (Igeo), were used to determine the degree of contamination. Both PI and Igeo indicated the extreme pollution of Hg and Cd, while PI also ranked Zn in the extreme polluted range. The US Environmental Protection Agency (USEPA) model for adults and children was used to estimate health risks by inhalation. The results identified non-carcinogenic exposure of children to lead (HI > 0.1) in commercial and industrial areas. Both children and adults in Zhengzhou’s commercial, residential, and park areas are exposed to higher levels of copper (Cu), lead (Pb), and zinc (Zn).

Characterising and communicating the potential hazard posed by potentially toxic elements in indoor dusts from schools across Lagos, Nigeria

Ambient and indoor air pollution results in an estimated 7 million premature deaths globally each year, representing a major contemporary public health challenge, but one poorly quantified from a toxicological and source perspective. Indoor exposure represents possibly the greatest potential overall exposure, yet our indoor environments are still poorly understood, modelled and characterized. In rapidly growing cities, such as Lagos, Nigeria, environmental monitoring can play an important role in establishing baseline data, monitoring urban pollution trends and in environmental education. Classroom dust samples were collected from 40 locations from across the twenty local government areas (LGAs) of Lagos, in June 2019. The aim of the study was to assess the potential hazard posed by PTE in indoor dusts and to develop a suitable risk communication strategy to inform and educate the public, promoting environmental health literacy. Concentrations of total PTE in indoor dusts were assessed using Energy Dispersive X-Ray Fluorescence (ED-XRF) spectrometry. Oral bioaccessibility determinations using the unified BARGE method, and analysis by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) were also performed on the dust samples to determine the fraction available for absorption in the gastrointestinal tract. Results showed that the indoor dust samples were largely uncontaminated, with only few exceptions (2 samples). Enrichment factor pollution trend for the total PTE concentrations was in the order of Pb > Zn > U > Cr > Cu > Ba > Mn > V > As > Cd > Ni > Al. Source apportionment studies using factor analysis suggests concentrations of Al, As, Fe, Mn, Ni, and U may be influenced largely by lithogenic factors, while Cd, Cu and Pb originated principally from anthropogenic sources. Chromium, V and Zn appear to originate from mixed sources of both lithogenic and anthropogenic origin. Our oral bioaccessibility determinations indicate that the assumption of 100% bioavailability based on pseudototal or total concentrations would overestimate the hazard potential of PTE in these indoor dusts. Zinc was the most bioaccessible PTE (mean of 88%), with Mn (57%), Pb (48%), Ba (48%), Al (41%), As (37%), Cu (36%), Ni (28%), Cr (10%) and Fe (7%) the least bioaccessible. Human health risk assessment, for both children and adults using the bioaccessible fraction, showed values to be within acceptable risk levels.

Simulated biological fluids - a systematic review of their biological relevance and use in relation to inhalation toxicology of particles and fibres

The use of simulated biological fluids (SBFs) is a promising in vitro technique to better understand the release mechanisms and possible in vivo behaviour of materials, including fibres, metal-containing particles and nanomaterials. Applications of SBFs in dissolution tests allow a measure of material biopersistence or, conversely, bioaccessibility that in turn can provide a useful inference of a materials biodistribution, its acute and long-term toxicity, as well as its pathogenicity. Given the wide range of SBFs reported in the literature, a review was conducted, with a focus on fluids used to replicate environments that may be encountered upon material inhalation, including extracellular and intracellular compartments. The review aims to identify when a fluid design can replicate realistic biological conditions, demonstrate operation validation, and/or provide robustness and reproducibility. The studies examined highlight simulated lung fluids (SLFs) that have been shown to suitably replicate physiological conditions, and identify specific components that play a pivotal role in dissolution mechanisms and biological activity; including organic molecules, redox-active species and chelating agents. Material dissolution was not always driven by pH, and likewise not only driven by SLF composition; specific materials and formulations correspond to specific dissolution mechanisms. It is recommended that SLF developments focus on biological predictivity and if not practical, on better biological mimicry, as such an approach ensures results are more likely to reflect in vivo behaviour regardless of the material under investigation.

Metal(loid) bioaccessibility of atmospheric particulate matter from mine tailings at Zimapan, Mexico

Metal(loid)s are contaminants of concern emitted as particulate matter (PM) from several pollution sources. The objective was to characterize potential exposure from local airborne metal(loid)s in a community in proximity to mine tailings. Air samples were collected weekly at five sites around the municipal mine tailings using two Hi-volume samplers for simultaneously collecting PM10 and PM2.5. Total suspended particulates (TSP), concentrations, speciation, and bioaccessibility of metal(loid)s were quantified. The size and form of particles were determined by scanning electron microscopy. The concentration of TSP (μg m-3) in the airborne samples ranged from 21.2 to 64.6 for PM2.5 and 23.6 to 80.1 for PM10. The profiles of analyzed quasi-total metal(loid) concentration from all sampling sites were similar between these aerosols PM sizes except at site 2 for Cd, at site 3 for Cu, and site 4 for Zn. The order of quasi-total metal(loid) concentration, in the airborne samples for both PM sizes, was As > Zn > Fe > Pb > Cu > Mn > Cd. As speciation included As-sulfite, As(III)-O, and As(V)-O with less concentration of As(III)-O in both PM sizes. Bioaccessible metal(loid) concentrations were very high and represented a great percentage from the quasi-total airborne concentrations, for instance, 10% and 37% for Pb and 8% and 6% for As in pulmonary and gastric bioaccessible concentrations, respectively. Knowing the toxic effects of these pollutants, there is an urgent need to establish environmental regulation of bioaccessible pollutant concentrations from PM dislodged from uncovered metal(loid) mine tailings affecting not only nearby human populations but also possible long-distance ecosystem transport.

Lead smelting alters wheat flour heavy metal concentrations and health risks

Wheat (Triticum aestivum L.) flour consumption may be a major source of human metal intake, especially when wheat is cultivated in metal-contaminated soils. This work investigated Cd, Cu, Pb, and Zn distribution in whole wheat flour, wheat flour, and wheat bran when grown in an area polluted by Pb smelting. Wheat product heavy metal concentrations were analyzed, and the (non)carcinogenic risks were assessed. Mean Cd, Cu, Pb, and Zn concentrations in whole wheat flour were 0.38, 3.83, 0.48, and 29.3 mg kg^-1 , respectively; those in flour were only slightly reduced. The ratios between noncarcinogenic average daily dose of whole wheat flour and wheat flour consumption ranged from 1.06 to 3.76, with Pb having the greatest values compared with other metals. For children, the average hazard quotients (HQs) of whole wheat flour consumption of Cd, Cu, Pb, and Zn were 4.19, 1.06, 1.53, and 1.07; those for wheat flour consumption were 3.81, 0.68, 0.70, and 0.98, respectively. The HQs of adults were less than those of children. Overall results indicated that consumption of wheat products may lead to health concerns in the heavy metal contaminated area, yet when wheat flour rather than whole wheat flour is consumed, only the human health risk from Pb ingestion is reduced. Altering or removing human edible crops in the most contaminated areas should be considered.

Understanding how methodological aspects affect the release of trace metal(loid)s from urban dust in inhalation bioaccessibility tests

The bioaccessibility of metal(loid)s in ambient particulate matter (PM) has been recently used to represent the risk of inhalation exposure. Nevertheless, different methodological factors affect the bioaccessibility values; among these, the type and composition of surrogate biological fluids and the liquid to solid ratio have been revealed to be the most important. To better understand how these methodological aspects affect the bioaccessibility, a reference material corresponding to urban dust (SRM1648a) was contacted with synthetic biological fluids commonly used in the literature representing surrogate fluids that may interact with fine (Gamble's solutions, artificial lysosomal fluid (ALF)) and coarse particles (gastric fluid), for liquid to solid (L/S) ratios ranging from 500 to 20,000. Visual MINTEQ 3.1. was used to enhance the discussion on how the solubility of metals in the leaching solution depends on the composition of the simulated fluids and the speciation of metals. The results obtained indicate that a small change in the composition of Gamble's solution (the presence of glycine) may increase significantly the bioaccessibility at a L/S ratio of 5,000. The highest bioaccessibility of most of the studied metal(loid)s at a L/S ratio of 5,000 was found for ALF fluid. The study of the effect of the L/S ratio showed that metal(loid)s bioaccessibility in Gamble's fluid increased logarithmically with increasing L/S ratio, while it remained practically constant in ALF and gastric fluid. This different behavior is explained assuming that the leaching of metal(loid)s in Gamble's solution is solubility-controlled, while in ALF and gastric fluid is availability-controlled.

Lead source and bioaccessibility in windowsill dusts within a Pb smelting-affected area

Windowsill, heavy metal-containing dust samples, collected at different building heights, may provide some insight into both source and human health risk. Windowsill dust samples were collected from the 1st to 9th floor (1.4-23.2 m above ground) near a lead smelter (1 km to the smelter) and in urban areas (4.2-7.3 km to the smelter) and separated into <10, 10-45 and 45-125 μm size fractions. Samples were extracted with artificial lysosomal fluid (ALF) and the physiologically based extraction test (PBET) (<10 μm fractions only), subjected to scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDS) and Pb isotopic analysis. Greater Pb concentrations were found in 10-45 μm fraction than the other size fractions; at the PX site, dust Pb concentrations increased with windowsill height, while an opposite trend was found at other sites. Isotopic analysis and SEM-EDS results supported this contention. Higher floor samples collected near the smelter were more affected by lead smelting than lower floor samples; lower floor samples collected at urban sites were more affected by resuspended Pb-laden particles from the ground than higher floors. The Pb bioaccessible fraction (BAF) in the ALF and PBET ranged between 68.9-90.1 and 1.3-17.0%, respectively; urban samples had greater BAF values than samples collected near the smelter. This, first of its kind investigation regarding Pb in dusts at different building heights, provides further insight for reducing human health risks within Pb smelter vicinities.

Bioaccessibilities of metal(loid)s and organic contaminants in particulates measured in simulated human lung fluids: A critical review

Particle-bound pollutants can pose a health risk to humans. Inhalation exposure evaluated by total contaminant concentrations significantly overestimates the potential risk. To assess the risk more accurately, bioavailability, which is the fraction that enters into the systemic circulation, should be considered. Researchers have replaced bioavailability by bioaccessibility due to the rapid and cost-efficient measurement for the latter, especially for assessment by oral ingestion. However, contaminants in particulates have different behavior when inhaled than when orally ingested. Some of the contaminants are exhaled along with exhalation, and others are deposited in the lung with the particulates. In addition, a fraction of the contaminants is released into the lung fluid and absorbed by the lung, and another fraction enters systemic circulation under the action of cell phagocytosis on particulates. Even if the release fraction, i.e., release bioaccessibility, is considered, the measurement faces many challenges. The present study highlights the factors influencing release bioaccessibility and the incorporation of inhalation bioaccessibility into the risk assessment of inhaled contaminants. Currently, there are three types of extraction techniques for simulated human lung fluids, including simple chemical solutions, sequential extraction techniques, and physiologically based techniques. The last technique generally uses three kinds of solution: Gamble's solution, Hatch's solution, and artificial lysosomal fluid, which are the most widely used physiologically based simulated human lung fluids. External factors such as simulated lung fluid composition, pH, extraction time, and sorption sinks can affect release bioaccessibility, whereas particle size and contaminant properties are important internal factors. Overall, release bioaccessibility is less used than bioaccessibility considering the deposition fraction when assessing the risk of contaminants in inhaled particulates. The release bioaccessibility measurement poses two main challenges: developing a unified, accurate, stable, simple, and systematic biologically based method, and validating the method through in-vivo assays.

Health Risk Assessment of Heavy Metals Accumulated on PM2.5 Fractioned Road Dust from Two Cities of Pakistan

The aim of this study is to identify and investigate levels of toxic heavy metals in PM2.5 fractioned road dust to better understand the associated inhalation risk and potential health impacts. To achieve this aim, concentrations of seven traffic generated heavy metals (Cu, Pb, Zn, Cd, Ni, Sb, and Cr) were determined in the PM2.5 fraction of road dust samples from four different locations (offices, residential, hospital, and school) in two cities (Karachi and Shikarpur) of Pakistan using ICP-MS. The average concentration values of heavy metals in Karachi were as follows: 332.9 mg/kg Cu, 426.6 mg/kg Pb, 4254.4 mg/kg Zn, 62.3 mg/kg Cd, 389.7 mg/kg Ni, 70.4 mg/kg Sb, 148.1 mg/kg Cr, whereas the average concentration values of heavy metals in Shikarpur were 245.8 mg/kg Cu, 538.4 mg/kg Pb, 8351.0 mg/kg Zn, 57.6 mg/kg Cd, 131.7 mg/kg Ni, 314.5 mg/kg Sb, 346.6 mg/kg Cr. The pollution level was assessed through two pollution indices enrichment factor (EF) and geoaccumulation index (Igeo). These indices showed moderate to extreme level pollution in studied areas of both cities. The health risk assessment through inhalation contact was conducted according to the United States Environmental Protection Agency's (USEPA) model for children and adults. Both non-cancerous and cancerous risks were characterised in the road dust samples for each location. As yet, there is not a single study on the concentrations of heavy metals in PM2.5 fractions of road dust in Karachi and Shikarpur, findings of this research will facilitate researchers for further investigations in current field.

The pattern and mechanism of air pollution in developed coastal areas of China: From the perspective of urban agglomeration

The green development of coastal urban agglomerations, which are strategic core areas of national economic growth in China, has become a major focus of both academics and government agencies. In this paper, China's coastal urban agglomeration is taken as the research area, aiming at the serious air pollution problem of coastal urban agglomeration, geographic information system (ArcGIS10.2) spatial analysis and the spatial Dubin model were applied to National Aeronautics and Space Administration atmospheric remote sensing image inversion fine particulate matter (PM2.5) data from 2010-2016 to reveal the temporal and spatial evolution characteristics and Influence mechanism of PM2.5 in China's coastal urban agglomerations, with a view to providing a reference value for coordinating air pollution in the coastal cities of the world. From 2010-2016, the PM2.5 concentration in China's coastal urban agglomerations decreased as a whole, and large spatial differences in PM2.5 concentration were observed in China's coastal urban agglomerations; the core high-pollution areas were the Beijing-Tianjin-Hebei, Shandong Peninsula, and Yangtze River Delta urban agglomerations. Large spatial differences in PM2.5 concentration were also observed within individual urban agglomerations, with higher PM2.5 concentrations found in the northern parts of the urban agglomerations. Significant spatial autocorrelation and spatial heterogeneity were observed among PM2.5-polluted cities in China's coastal urban agglomerations. The northern coastal urban agglomerations formed a relatively stable and continuous high-pollution zone. The spatial Dubin model was used to analyze the driving factors of PM2.5 pollution in coastal urban agglomerations. Together, meteorological, socioeconomic, pollution source, and ecological factors affected the spatial characteristics of PM2.5 pollution during the study period, and the overall effect was a mixed effect with significant spatial variation. Among them, meteorological factors were the greatest driver of PM2.5 pollution. In the short term, the rapid increase in population density, industrial emissions, industrial energy consumption, and total traffic emissions were the important driving factors of PM2.5 pollution in the coastal urban agglomerations of China.

Correlation between lead speciation and inhalation bioaccessibility using two different simulated lung fluids

This study investigated the relationship between lead (Pb) speciation determined using Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy in <10 μm particulate matter (PM₁₀) from mining/smelting impacted Australian soils (PP, BHK5, BHK6, BHK10 and BHK11) and inhalation exposure using two simulated lung fluids [Hatch's solution, pH 7.4 and artificial lysosomal fluid (ALF), pH 4.5]. Additionally, elemental composition of Pb rich regions in PP PM₁₀ and the post-bioaccessibility assay residuals were assessed using a combination of Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) to provide insights into how extraction using simulated lung fluids may influence Pb speciation in vitro. Correlation between Pb speciation (weighted %) and bioaccessibility (%) was assessed using Pearson r (α = 0.1 and 0.05). Lead concentration in PM₁₀ samples ranged from 782 mg/kg (BHK6) to 7796 mg/kg (PP). Results of EXAFS analysis revealed that PP PM₁₀ was dominated by Pb adsorbed onto clay/oxide, while the four BHK PM₁₀ samples showed variability in the weighted % of Pb adsorbed onto clay/oxide and organic matter bound Pb, Pb phosphate, anglesite and galena. When bioaccessibility was assessed using different in vitro inhalation assays, results varied between samples and between assays, Pb bioaccessibility in Hatch's solution ranged from 24.4 to 48.4%, while in ALF, values were significantly higher (72.9-96.3%; p < 0.05). When using Hatch's solution, bioaccessibility outcomes positively correlated to anglesite (r:0.6246, p:0.0361) and negatively correlated to Pb phosphate (r: -0.9610, p:0.0041), organic bound Pb (r: -0.7079, p: 0.0578), Pb phosphate + galena + plumbojarosite (r: -0.9350, p: 0.0099). No correlation was observed between Pb bioaccessibility (%) using Hatch's solution and weighted % of Pb adsorbed onto clay/oxide and between bioaccessibility (%) using ALF and any Pb species. SEM and EDX analysis revealed that a layer of O-Pb-Ca-P-Si-Al-Fe formed during the in vitro extraction using Hatch's solution.

Influence of household smoking habits on inhalation bioaccessibility of trace elements and light rare earth elements in Canadian house dust

In this study, total concentration and inhalation bioaccessibility (dissolution in simulated biological solution) of trace elements (TE) and rare earth elements (REE) were assessed in PM₁₀ from Canadian house dust samples with smoking (n = 25) and non-smoking (n = 25) status. Compared to the natural background concentrations in Canadian soils, median Zn, Pb, Cd and Cu concentrations in PM₁₀ were 10-23 fold higher, while median La, Ce and Pr concentrations were 1.6-2.4 fold higher. Mann-Whitney tests (α = 0.05) indicated no difference between the median TE concentrations based on the smoking status of the household; however, median REE concentrations were significantly higher in the PM₁₀ of smoking households. Additionally, Cd and Ni were positively correlated (Spearman r, p < 0.05) to La, Ce and Nd in smoking households, suggesting that tobacco combustion may have contributed REE in the PM₁₀ of these households. Median inhalation-ingestion bioaccessibility assay outcomes of arsenic (As) and lead (Pb) was higher in the non-smoking households when compared to smoking households (Mann Whitney test, α = 0.05), suggesting that tobacco combustion products may be associated with less soluble species of As and Pb. Although REE bioaccessibility was negligible in simulated lung epithelial fluid regardless of the smoking status of the household, bioaccessibility in the lung-gastric phase was 23.6-27.6% in the smoking household and 34.7-36.7% in the non-smoking households, indicating a significantly lower REE dissolution in PM₁₀ of smoking households. In contrast, between 17 and 21.9% bioaccessibility of REE was observed when artificial lysosomal fluid was used, where the outcome was not significantly affected by the smoking status. This study indicates that despite a higher median REE concentration in the PM₁₀ of smoking households, inhalation bioaccessibility may be significantly influenced by the mineralogy.

Metal bioaccessibility, particle size distribution and polydispersity of playground dust in synthetic lysosomal fluids

Inhalation of playground dust-derived fine particles in schoolyards poses a risk from exposure to metal(oids) and minerals. In this work, we obtained the total concentration and bioaccessibility of metal(oids) with Gamble Solution (GS) and Artificial Lysosomal Fluid (ALF) synthetic solutions, simulating the extracellular neutral pH environment of the lung and the intracellular conditions of the macrophage, respectively. Scanning Electron Microscope (SEM), and Dynamic Light Scattering analysis (DLS) techniques were used to characterize particles with a size smaller than 2.5 μm, which can be assimilated by macrophages in the deep part of the lung. Arsenic (As), lead (Pb), copper (Cu), manganese (Mn), zinc (Zn), and iron (Fe) showed concentrations of 39.9, 147.9, 286, 1369, 2313, 112,457 mg·kg^-1, respectively. The results indicated that all studied elements were enriched when compared to (i) local geochemical background and (ii) findings reported in other cities around the world. Bioaccessibility of metal(oids) in GS was low-moderate for most studied elements. However, in ALF assays, bioaccessibility was high among the samples: for lead (Pb = 34-100%), arsenic (As = 14.7-100%), copper (Cu = 17.9-100%), and zinc (Zn = 35-52%) possibly related to hydrophobic minerals in dust. SEM and DLS image analysis showed that playground dust particles smaller than 2.5 μm are dominant, particularly particles with a size range of 500-600 nm. The polydispersity detected in these particle sizes showed that most of them might be crystalline compounds (elongated shapes) forming agglomerates instead of combustion particles (spheres). Moreover, the circularity detected varies from 0.57 to 0.79 (low roundness), which corroborates this finding. The presence of agglomerates of ultrafine/nanoparticles containing highly bioaccessible metals in playground sites may have severe implications in children's health. Therefore, further studies are required to characterize the size distribution, structure, shape and composition of such minerals which are essential factors related to the toxicology of inhaled dust particles.

In vitro lung and gastrointestinal bioaccessibility of potentially toxic metals in Pb-contaminated alkaline urban soil: The role of particle size fractions

Potentially toxic metals (PTMs), associated with different size particles in soil, may play an important role in adverse health effect and risk for human. The objective is to evaluate the lung and gastrointestinal bioaccessibility and risk of PTMs in Pb-contaminated alkaline urban soil depending on the particle size fractions. The size fractions of 50-250 μm, 5-50 μm, 1-5 μm, <1 μm in Pb-contaminated alkaline urban soil from Baoji Heavy Industrial Base City, NW China, were screened by Sequential Wet Sieving Separation Procedure (SWSSP) based on Stokes' Law. The concentrations of 9 potentially toxic metals (As, Ba, Co, Cr, Cu, Mn, Ni, Pb and Zn) in each particle size fractions were characterized by ICP-OES and ICP-MS, and the in vitro bioaccessibility dependent of size fractions were evaluated by the simulation fluids of Artificial Lysosomal Fluid (ALF) and Gamble for lung, PBET, SBET, IVG, SBRC, UBM for gastric and intestinal, respectively. Health risks were assessed considering simulated external exposure using intestinal and lung bioaccessibility. The lung and gastrointestinal bioaccessibility and exposure risks of PTMs in fine particle size (i.e. <1 μm) was higher than larger particle size fractions (i.e. 50-250 μm, 5-50 μm, 1-5 μm), however, some different variations of bioaccessibility observed the simulation fluids and time dependent. In case of single PTMs, the lung bioaccessibilities of PTMs in ALF were higher than those in Gamble fluids, most prominent in Co, Cu, Mn and Zn, while the gastrointestinal [G + I] bioaccessibility of PTMs was less than those in gastric [G], like Cu, Mn, Pb and Zn mostly. The non-carcinogenic risks of these PTMs to children via inhalation were acceptable and higher than those of adults, but reverse for carcinogenic risk. Comparatively, the non-carcinogenic and carcinogenic risks of PTMs via ingestion pathway were both higher than those for adults. Although the risks from ingestion were in acceptable range, the total carcinogenic risks for children were more than 10^-4, which would bring carcinogenic risks and should be paid attention to. It was noted that the toxic metal, Co in all size fractions was the most important contributor for noncarcinogenic risks and Cr mostly for carcinogenic risks via inhalation pathway for adults and children in local areas. However, Pb was the most important contributor for noncarcinogenic risk both for adults and children via ingestion pathway relative to Co and Cr for carcinogenic risks through hand-to-mouth ingestion. Those observations demonstrated the important role that the smaller particle fractionations in Pb-contaminated alkaline soil played in both bioaccessibility and the refinement of human health-risk assessments for the inhalation and ingestion pathway.

Metal(loid)s inhalation bioaccessibility and oxidative potential of particulate matter from chromated copper arsenate (CCA)-contaminated soils

Field-collected chromated copper arsenate (CCA)-contaminated soils and associated particulate matter (PM) were characterized for their total metal(loid)s content (As, Cr, Cu, Fe, Mn, Ni, Pb and Zn) and physicochemical properties. Copper, Ni, Pb and Zn fractionation (using sequential extraction) and inhalation bioaccessibility (using two lung fluids) of trace elements were assessed in PM samples. In Gamble's solution (GS), low average bioaccessibility (up to 12%) was observed for As, Cu, Mn, and Ni. A strong correlation (r = 0.92, p < 0.005, n = 9) between the soluble and exchangeable fraction (F1) and bioaccessibility in GS was observed for Cu. Inhalation bioaccessibility in artificial lysosomal fluid (ALF) was higher for Cu (avg. 78.5 ± 4.2%), Mn (avg. 56.8 ± 12.1%), Zn (avg. 54.8 ± 24.5%) and As (avg. 45.4 ± 18.8%). Strong correlations between inhalation bioaccessibility in ALF and the mobile (i.e. F1+F2) metal fraction were observed for all tested metals (i.e. (Cu (r = 0.95, p < 0.005), Ni (r = 0.79, p < 0.05), Pb (r = 0.92, p < 0.005) and Zn (r = 0.98, p < 0.005)), n = 9). The oxidative potential (OP) of PM was also assessed using an ascorbate (AA) depletion assay (OP_AA). Mobile Cu fractions were deemed to be the main factor influencing OP_AA ((F1 (r = 0.99, p < 0.005), F2 (r = 0.97, p < 0.005)), n = 9) in PM samples. A strong correlation (r = 0.94, p < 0.005, n = 10) was also observed between Cu bioaccessibility in GS and OP_AA.

Relationship between Pb relative bioavailability and bioaccessibility in phosphate amended soil: Uncertainty associated with predicting Pb immobilization efficacy using in vitro assays

In this study, an in vitro in vivo correlation (IVIVC) between Pb in vitro bioaccessibility (IVBA) and relative bioavailability (RBA) was explored to determine whether the efficacy of Pb immobilization in phosphate amended soils could be predicted using an in vitro approach. Mining/smelting impacted soil from Broken Hill, Australia (582-3536 mg/kg of Pb in the <250 μm soil particle fraction) was amended with Phosphoric Acid (PA), Mono Ammonium Phosphate (MAP) or Triple Super Phosphate (TSP) at Pb:P molar ratios of 1:1-1:5. Pb speciation in pre- and post-treated soil was assessed using X-ray Absorption Spectroscopy (XAS), Pb IVBA was measured using the Solubility Bioaccessibility Research Consortium (SBRC) assay (gastric and intestinal phases), and Pb RBA was determined in mice using blood Pb concentration as the bioavailability endpoint. XAS analysis revealed a 3.75-6.00 fold increase in the weighted % of Pb phosphates in soil containing >1000 mg/kg Pb while treatment effect ratios of 0.89-0.99 (SBRC-G), 0.09-0.71 (SBRC-I) and 0.27-0.80 (RBA) were observed in PA amended soil (Pb:P = 1:5). Although significant (p < 0.05) correlation were obtained between Pb RBA and IVBA (%) determined using SBRC-G (r = 0.64) and SBRC-I (r = 0.67), the strengths of the relationships were weak (r2 = 0.41-0.45). This research highlights the complexities associated with the prediction of Pb RBA in phosphate amended soil.