Towards a holistic approach to the geochemistry of solid inorganic particles in the urban environment

Natural and anthropogenic impact on the microclimate and particulate matter in the UNESCO show cave

Particulate matter concentrations (PM10, PM2.5, PM1) and microclimatic parameters (air temperature, CO2) were monitored in the Škocjan Caves (Slovenia). The effects of tourist visits on the PM concentrations and the cave's microclimate are immediate and direct, but these values normalise relatively quickly. The results showed seasonal, diurnal, and spatial differences in all parameters studied. Due to the higher number of visitors, their influence on the cave's microclimate and PM10 and PM2.5 concentrations is greater in summer than in winter. The measured PM1 levels depend on the ventilation in the cave, as air transport plays an important role in their introduction into the cave. PM consists of minerals of natural origin resulting from the re-suspension of cave sediments due to strong air currents generated by the opening of the doors to tourists and their walks. The second most common influence is the anthropogenic phases originating from maintenance work in the cave, electronic devices, cave lighting and emissions from outside the cave (aerosols from the polluted Reka River, industry, traffic, gypsum waste disposal). In order to upgrade the sustainable use of the UNESCO-listed Škocjan Caves for tourism, we propose regular monitoring of PM and a detailed characterization of individual PMs and their sources, in addition to monitoring of the cave's microclimate and biology.

Oral bioaccessibility of potentially toxic elements in various urban environmental media

An important aspect of geochemical studies is determining health hazard of potentially toxic elements (PTEs). Key information on PTEs behaviour in the human body in case of their ingestion is provided with the use of in vitro bioaccessibility tests. We analysed and compared oral bioaccessibility of a wide range of PTEs (As, Cd, Ce, Cr, Cu, Hg, La, Li, Ni, Pb, Sb, Sn, Zn), including some that are not often studied but might pose a human health hazard, in soil, attic dust, street dust, and household dust, using Unified BARGE Method (UBM). Additionally, feasibility of usage of scanning electron microscope techniques in analyses of solid residuals of UBM phases was tested. Results show that bioaccessible fractions (BAFs) of PTEs vary significantly between individual samples of the same medium, between different media and between the gastric and gastro-intestinal phases. In soil, attic dust and street dust, bioaccessibility of individual PTE is mostly higher in gastric than in gastro-intestinal phase. The opposite is true for PTEs in household dust. In all four media, with the exception of Pb in household dust, among the most bioaccessible PTEs in gastric phase are Cd, Cu, Pb, and Zn. During the transition from the stomach to small intestine, the mean BAFs of most elements in soil, attic dust, and street dust decreases. The most bioaccessible PTEs in gastro-intestinal phase are Cu, Cd, Ni, and As. Micromorphological and chemical characterisation at individual particle level before and after bioaccessibility test contribute significantly to the understanding of oral bioaccessibility.

Potentially Harmful Elements Associated with Dust of Mosques: Pollution Status, Sources, and Human Health Risks

Potentially harmful elements (PHEs) associated with dust generated from anthropogenic sources can be transported into mosques and deposited on the filters of the air-conditioners (AC); thereby, children and adults are exposed to such PHEs while visiting mosques. Data dealing with the assessment of PHEs pollution and its human health risk in mosques dust in Saudi Arabia are scarce. Therefore, this work aims to examine the levels and pollution status of PHEs in AC filter dust (ACFD) of mosques and their associated human health risk in three Saudi cities: Jubail, Jeddah, and Dammam metropolitan. A similar concentration pattern of PHEs is observed in three cities' mosques with noticeably higher concentrations than both global crustal and local background values for Zn, Cu, Pb, As, and Cd only. Except for Fe, Al, and Mn, the highest PHEs concentrations were found in Jeddah (1407 mg/kg), followed by Dammam (1239 mg/kg) and Jubail (1103 mg/kg). High PHEs' concentrations were also recorded in mosques located near workshops and suburban areas compared to urban areas. Based on the spatial pattern, enrichment factor, geo-accumulation index, pollution load index, and ecological risk values, Jubail, Jeddah, and Dammam have shown moderate pollution levels of Cd, As, Pb, and Zn. On the other hand, Cu. Zn, Cu, Cr, Pb, Ni, As, and Cd had degrees of enrichment levels that varied from significantly enriched to extremely highly enriched in the ACFD of the three cities. Heavy pollution is found in Jubail, which posed a higher potential ecological risk than in Jeddah and Dammam. Cd presents the highest ecological risk factors (ER) in the three cities. Carcinogenic and non-carcinogenic risks for children and adults follow the order: Jeddah > Dammam > Jubail, and the ingestion pathway was the main route for exposure. Carcinogenic and con-carcinogenic risks in the mosques of the various studied cities were generally within the acceptable range.

Using community science for detailed pollution research: a case-study approach in Indianapolis, IN, USA

Heavy metal contamination in urban environments, particularly lead (Pb) pollution, is a health hazard both to humans and ecological systems. Despite wide recognition of urban metal pollution in many cities, there is still relatively limited research regarding heavy metal distribution and transport at the household-scale between soils and indoor dusts-the most important scale for actual human interaction and exposure. Thus, using community-scientist-generated samples in Indianapolis, IN (USA), we applied bulk chemistry, Pb isotopes, and scanning electron microscopy (SEM) to illustrate how detailed analytical techniques can aid in interpretation of Pb pollution distribution at the household-scale. Our techniques provide definitive evidence for Pb paint sourcing in some homes, while others may be polluted with Pb from past industrial/vehicular sources. SEM revealed anthropogenic particles suggestive of Pb paint and the widespread occurrence of Fe-rich metal anthropogenic spherules across all homes, indicative of pollutant transport processes. The variability of Pb pollution at the household scale evident in just four homes is a testament to the heterogeneity and complexity of urban pollution. Future urban pollution research efforts would do well to utilize these more detailed analytical methods on community-sourced samples to gain better insight into where the Pb came from and how it currently exists in the environment. However, these methods should be applied after large-scale pollution screening techniques such as portable X-ray fluorescence (XRF), with more detailed analytical techniques focused on areas where bulk chemistry alone cannot pinpoint dominant pollution mechanisms and where community scientists can also give important metadata to support geochemical interpretations.

Spatial Distribution, Contamination Levels, and Health Risk Assessment of Potentially Toxic Elements in Household Dust in Cairo City, Egypt

Urban areas’ pollution, which is owing to rapid urbanization and industrialization, is one of the most critical issues in densely populated cities such as Cairo. The concentrations and the spatial distribution of fourteen potentially toxic elements (PTEs) in household dust were investigated in Cairo City, Egypt. PTE exposure and human health risk were assessed using the USEPA’s exposure model and guidelines. The levels of As, Cd, Cr, Cu, Hg, Mo, Ni, Pb, and Zn surpassed the background values. Contamination factor index revealed that contamination levels are in the sequence Cd > Hg > Zn > Pb > Cu > As > Mo > Ni > Cr > Co > V > Mn > Fe > Al. The degree of contamination ranges from considerably to very high pollution. Elevated PTE concentrations in Cairo’s household dust may be due to heavy traffic emissions and industrial activities. The calculated noncarcinogenic risk for adults falls within the safe limit, while those for children exceed that limit in some sites. Cairo residents are at cancer risk owing to prolonged exposure to the indoor dust in their homes. A quick and targeted plan must be implemented to mitigate these risks.

Characterization of Atmospheric Deposition as the Only Mineral Matter Input to Ombrotrophic Bog

Ombrotrophic peatlands contain a very small percentage of mineral matter that they receive exclusively from atmospheric deposition. Mineral matter deposited on the Šijec bog was characterized using scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS). We collected solid atmospheric deposition from snow, rainwater, and using passive samplers. Samples were collected at average atmospheric conditions and after two dust events. Size, morphology, and chemical composition of individual particles were determined. We distinguished four main particle groups: silicates, carbonates, organic particles, and Fe-oxyhydroxides. Silicate particles are further divided into quartz and aluminosilicates. Proportions of these groups vary between samples and between sample types. In all samples, silicate particles predominate. Samples affected by dust events are richer in solid particles. This is well observed in passive deposition samples. Carbonates and organic particles represent smaller fractions and are probably of local origin. Iron-oxyhydroxides make up a smaller, but significant part of particles and are, according to their shape and chemical composition, of both geogenic and anthropogenic origin. Estimated quantity and percentage of main groups vary throughout the year and are highly dependent on weather conditions. Dust events represent periods of increased deposition and contribute significantly to mineral matter input to peatlands.

Hazardous enrichment of toxic elements in soils and olives in the urban zone of Lavrio, Greece, a legacy, millennia-old silver/lead mining area and related health risk assessment

Lavrio is a Greek town with several abandoned Ag/Pb mines. In this study, 19 potentially toxic elements (PTEs) were measured in soil, weeds, and olives. Levels of seven of the studied PTEs in soil were highly elevated: Zn (56.2-58,726 mg kg^-1), Pb (36.2-31,332), As (7.3-10,886), Cu (8.3-1273), Sb (0.99-297.8), Cd (0.17-287.7), and Ag (0.09-38.7). Synchrotron-based X-ray absorption near edge structure analysis of the soils revealed that As was predominantly associated with scorodite, Pb with humic substances, Zn with illite, Zn(OH)₂ and humic substances, and Fe with goethite-like minerals. The transfer of the PTEs to weeds was relatively low, with the transfer coefficient being less than 1.0 for all PTEs. Cadmium in table olives surpassed 0.05 mg kg^-1 fresh weight (the limit in EU), while Pb surpassed its limit in approximately half of the samples. Health risk assessment confirmed soil contamination in the study area where As and Pb hazard quotients were well above 1.0 and the average hazard index equaled 11.40. Additionally, the cancer risk values exceeding the 1 × 10^-4 threshold. The results obtained in the study indicate that Lavrio urgently requires an adequate ecofriendly remediation plan, including revegetation with tolerant species and targeted efforts to chemically stabilize harmful PTEs. The presented approach may serve as a pivotal study for industrial areas with similar contamination levels.

Road sediment, an underutilized material in environmental science research: A review of perspectives on United States studies with international context

Road sediment is a pervasive environmental medium that acts as both source and sink for a variety of natural and anthropogenic particles and often is enriched in heavy metals. Road sediment is generally understudied in the United States (U.S.) relative to other environmental media and compared to countries such as China and the United Kingdom (U.K.). However, the U.S. is an ideal target for these studies due to the diverse climates and wealth of geochemical, socioeconomic, demographic, and health data. This review outlines the existing U.S. road sediment literature while also providing key international perspectives and context. Furthermore, the most comprehensive table of U.S. road sediment studies to date is presented, which includes elemental concentrations, sample size, size fraction, collection and analytical methods, as well as digestion procedure. Overall, there were observed differences in studies by sampling time period for elemental concentrations, but not necessarily by climate in the U.S. Other key concepts addressed in this road sediment review include the processes controlling its distribution, the variety of nomenclature used, anthropogenic enrichment of heavy metals, electron microscopy, health risk assessments, remediation, and future directions of road sediment investigations. Going forward, it is recommended that studies with a higher geographic diversity are performed that consider smaller cities and rural areas. Furthermore, environmental justice must be a focus as community science studies of road sediment can elucidate pollution issues impacting areas of high need. Finally, this review calls for consistency in sampling, data reporting, and nomenclature to effectively expand work on understudied elements, particles, and background sediments.

Attic dust: an archive of historical air contamination of the urban environment and potential hazard to health?

A comprehensive study of attic dust in an urban area is presented. Its entire life cycle, from determining historical emission sources to recognising the processes that take place in attic dust and its potential to impact human health is discussed. Its chemical composition and morphological characteristics of individual solid particles reflect past anthropogenic activities. High levels of Be-Cd-Cu-Sb-Sn-Pb-Te-Zn and occurrence of Cu-Zn shavings are typical for an industrial zone characterised by a foundry and a battery factory. High levels of Co-Fe-Mo-Ni-W-Ba-Cr-Mg-Mn-Nb-Ti and occurrence of various solid Fe-oxides, particularly spherical particles, were identified in another industrial zone, which was dominated by the automotive and metal-processing industries. Emissions from coal combustion affected the distribution of S-Se-Hg-Tl-As-Ag-U. The predominant mineral in attic dust is gypsum, which was presumably formed in situ by the reaction of carbonate dust particles and atmospheric SO₂ gas. The high oral bioaccessibility of As-Cd-Cu-Pb-Zn in the gastric phase and high bioaccessibility of As-Cu-Cd-Ni in the gastrointestinal phase were identified. Determined characteristics of attic dust and identified possibilities of prolonged human exposure to it indicate that attic dust should be treated as an excellent proxy for historical air contamination as well as a potentially hazardous material for human health.

Distribution of potentially harmful elements in attic dust from the City of Coronel (Chile)

Attic dusts provide an indirect measure of airborne pollutants deposited in the urban environment. The objectives of this study are: (1) to determine the concentrations of As, Ba, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr, V and Zn in attic dust in the City of Coronel, (2) to evaluate the source apportionment of PHE and (3) to assess the risk of health effects from exposure in adults and children. In the City of Coronel, attic dust samples were collected in 19 houses. The concentrations of As, Ba, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr, V and Zn were measured in ICP-OES after Aqua Regia digestion of < 75 µm dust sample. The median (and the range) concentration (mg kg^-1) of potentially harmful elements was: As 16 (7-72), Ba 154 (53-251), Cd 0.8 (0.25-14.5), Co 12, (8-22), Cr 38 (22-482), Cu 107 (44-1641), Mn 698 (364-1245), Ni 51 (24-1734), Pb 66 (18-393), Sr 131 (52-252), V 129 (57-376) and Zn 815 (107-9761). The exploratory data analysis shows that Ni, Cu, Cr, Zn, Pb and As distribution is dominated by anthropogenic sources and characterized by high extreme values. Principal component analysis shows four factors. One factor is geogenic, while the other three factors are associated with transport emissions and the industrial park. The resulting median of cumulative noncarcinogenic risk (HI_s) value for attic dust was 3.49 for children. This is significant, as any value greater than one indicates an elevated risk.

Using Community Science to Better Understand Lead Exposure Risks

Lead (Pb) is a neurotoxicant that particularly harms young children. Urban environments are often plagued with elevated Pb in soils and dusts, posing a health exposure risk from inhalation and ingestion of these contaminated media. Thus, a better understanding of where to prioritize risk screening and intervention is paramount from a public health perspective. We have synthesized a large national data set of Pb concentrations in household dusts from across the United States (U.S.), part of a community science initiative called "DustSafe." Using these results, we have developed a straightforward logistic regression model that correctly predicts whether Pb is elevated (>80 ppm) or low (<80 ppm) in household dusts 75% of the time. Additionally, our model estimated 18% false negatives for elevated Pb, displaying that there was a low probability of elevated Pb in homes being misclassified. Our model uses only variables of approximate housing age and whether there is peeling paint in the interior of the home, illustrating how a simple and successful Pb predictive model can be generated if researchers ask the right screening questions. Scanning electron microscopy supports a common presence of Pb paint in several dust samples with elevated bulk Pb concentrations, which explains the predictive power of housing age and peeling paint in the model. This model was also implemented into an interactive mobile app that aims to increase community-wide participation with Pb household screening. The app will hopefully provide greater awareness of Pb risks and a highly efficient way to begin mitigation.

Determination of Total Mercury and Carbon in a National Baseline Study of Urban House Dust

Mercury (Hg) is one of the top ten chemicals of concern for public health, according to the World Health Organization. This study investigates Hg concentrations in house dust collected from urban single family homes, to better understand typical indoor residential exposures. Using direct solid sample analysis, total Hg and carbon (TC) were determined in the <80 µm fraction of settled dust samples collected under the Canadian House Dust Study. Hg concentrations displayed a log-normal distribution with median/geomean of 0.68/0.70 mg/kg (n = 995). A small subset (<1%) of homes exhibited anomalously high dust Hg concentrations (>9.0 mg/kg). A comparison of Hg concentrations in fresh dust and household vacuum dust collected from the same homes indicated no significant difference in the two sampling methods. Total carbon concentrations displayed a median/geomean of 29.3/28.5% (n = 1011). A significant correlation between total Hg and TC in house dust (p < 0.00001) reflects the association between Hg and organic carbon previously observed in soil and sediments. The results of this study indicate a 10-fold enrichment in house dust compared with the average background concentrations reported for soil and sediments (0.07 mg/kg). The observed enrichment is attributable to Hg emissions from indoor sources and/or Hg carried home from occupational sources.

Lead Pollution, Demographics, and Environmental Health Risks: The Case of Philadelphia, USA

Lead (Pb) soil contamination in urban environments represents a considerable health risk for exposed populations, which often include environmental justice communities. In Philadelphia, Pennsylvania (PA), Pb pollution is a major concern primarily due to extensive historical Pb-smelting/processing activity and legacy use of Pb-based paints and leaded gasoline. The U.S. Environmental Protection Agency (USEPA) organized and/or compiled community-driven soil sampling campaigns to investigate Pb content in surface soils across Philadelphia. Using these data (n = 1277), combined with our own dataset (n = 1388), we explored the spatial distribution of Pb content in soils across the city using ArcGIS. While assessing Zone Improvement Plan (ZIP)-code level data, we found strong correlations between factors, such as the percentage of children with elevated blood lead levels (% EBLL) and % minority population as well as between % EBLL and % children in poverty. We developed a “Lead Index” that took demographics, median measured Pb-in-soil content, and % EBLLs into account to identify ZIP codes in need of further assessment. Our results will be used to help lower the Pb-exposure risk for vulnerable children living in disproportionately burdened communities.

Characteristics and health risk assessment of heavy metal contamination from dust collected on household HVAC air filters

Heavy metals associated with airborne particulate matter are detrimental to human health, but risk assessment is difficult due to the technical challenges of determining exposure rates. In houses and other buildings, the heating, ventilation and air conditioning (HVAC) system is equipped with an air filter that captures airborne particulate matter from the indoor air that enters the HVAC system. This study used the air filter dust as a proxy for the heavy metal exposure of children and adults, based on a household study in Kuwait. Air filter dust contained from 12.5 ± 5 mg Co/kg dust to 14 453 ± 5046 mg Fe/kg dust. Houses had high levels of Fe, Al, Zn, and Mn and relatively low concentrations of As and Co. Source apportionment revealed that metals in air filter dust were from natural and anthropogenic sources, including vehicular emissions, fossil fuel combustion, and metals-related industries. The total Hazard Index (HI; Σ exposure routes) for heavy metals was >1 for children and adults. Total cancer risks (TCR; Σ exposure routes) were 5.93 × 10^-3 (95% CI: 5.28 × 10^-3- 6.59 × 10^-3) for children and 5.16 × 10^-3 (95% CI: 4.59 × 10^-3 - 5.73 × 10^-3) for adults. Heavy metals, particularly the Cr and Pb concentrations, contribute to the non-carcinogenic and carcinogenic health risks of children and adults in Kuwait households.

Investigation of Pb-contaminated soil and road dust in a polluted area of Philadelphia

A multi-analytical geochemical investigation of Pb-contaminated collocated road dust and soils, at two size fractions, was performed in Fishtown, Philadelphia, PA, USA. The combinations of methods employed in this case study were chosen to better characterize the contamination, enhance identification of pollution sources, improve understanding of the impact of former Pb smelters, and to study the relationships between two media and between two size fractions. High concentrations of Cu and Sn were observed in both bulk and finer road dust, whereas large concentrations of Zn and Pb were found in both bulk and finer soil samples, implying pollution. There were no obvious associations between Pb soil concentrations and former smelter locations. Therefore, the primary source of the high mean Pb content in bulk (595 ppm) and fine soils (687 ppm) was likely legacy lead paint and/or leaded-gasoline products. Using electron microscopy, we found that Pb particles were mainly 0.1-10 µm in diameter and were ubiquitous in both soil and dust samples. Two-way analysis of variance tests revealed that, for most chemical elements explored here, there were statistically significant differences in concentrations based on media and size fractions, with finer sizes being more polluted than the bulk. The mineralogical composition and the sources of several pollutant elements (Cr, Cu, Zn, Pb), however, were similar for both soil and dust, pointing to material exchange between the two media. We suggest that future investigations of collocated road dust and soils in urban environments use the methodologies applied in this study to obtain detailed insights into sources of roadside pollution and the relationships between neighboring media.