Contaminated Land Exposure Assessment Research Articles

Determination of soil environmental criteria for high-risk trace metals in urban park soils using improved CLEA model

The trace metals (TMs) accumulated in urban park soils can pose potential threats to human health, making the management of soil quality based on health risks critically important. Based on the human health risk assessment (HHRA) model coupled with Monte Carlo Simulation, this study improved the contaminated land exposure assessment (CLEA) model. Combined with local parameters, the Soil Environmental Criteria (SEC) for high-risk trace metals (TMs) in urban park soils were calculated. Results indicated that all the mean TCR (Total carcinogenic risk) values of seven TMs exceeded the risk threshold of 1E-06, suggesting a higher likelihood of carcinogenic risks for all populations. As and Cr presented the highest potential carcinogenic risks, and were identified as high-risk TMs in the study area. The traditional CLEA model was enhanced by incorporating region-specific data, optimizing exposure parameter calculations, and addressing parameter sensitivity and uncertainty. Using the improved CLEA model, the SEC values for high-risk TMs were calculated, revealing that the SEC values gradually increased from ages 1 to 18, while significantly decreased for individuals over 80 years old. This study effectively addresses issues of parameter uncertainty and sensitivity in the CLEA model, offering new insights for the development of soil environmental quality standards.

Health Risk Assessment of Lead in Soils from an Historic Industrial Site in North-East England

The former St. Antony’s Lead Works site, now the central part of an urban recreational park (Walker Riverside Park) in the east end of Newcastle upon Tyne (England, UK), has been assessed based on the Pb concentration in topsoil according to recently derived Category 4 Screening Level (C4SL) for public open space–park (POSpark, 1300 mg/kg). The site was divided into eight sampling areas following its physical layout. In total 79 soil samples were collected, characterised for acidity and organic matter content, and analysed by energy dispersive X-ray fluorescence (ED-XRF). The Pb levels in most of the samples, particularly those from the fringes of the site, are below the generic guideline value (down to 70 mg/kg). More than 16% of the samples from nearly all sampling areas, especially those sampling points around the former horizontal condenser flue and main chimney, contain levels of Pb significantly exceeding the limit (up to 206,000 mg/kg). No correlation is found between the Pb concentration in soil samples and their acidity (mostly neutral, pH 7.0 ± 0.5) or organic matter content (15.5 ± 4.1%). Using the Contaminated Land Exposure Assessment (CLEA) model (version 1.071), the site-specific risk assessment criteria (SSAC) for Lead (C4SL child), 2862 mg/kg, is obtained based on adjusted exposure frequency and occupancy period. Nearly 9% of the individual sample Pb concentrations (n = 79) across sample locations B, C, D and H are still above the specific value. Further statistical evaluation based on 95% upper confidence limit confirms that the site still represents a potential human health risk. This is because Pb concentrations, from two areas in the centre of the site (sample locations B and C), are greatly over the SSAC specific threshold (sample mean at location B is 12,350 mg/kg and at location C is 11,745 mg/kg).

Human health risk-based Generic Assessment Criteria for agricultural soil in Jiangsu and Zhejiang provinces, China

Agricultural soil pollution in China poses a major threat to human health and food safety. There are no agricultural soil environmental standards based on human health in China, which prevents effective screening and assessment of risks. Jiangsu (JS) and Zhejiang (ZJ) provinces, located in the Yangtze River Delta (YRD) core region, have obvious differences in agricultural land conditions, which will result in differences in Generic Assessment Criteria (GAC). In this study, we derived and compared human health risk-based GAC using the Contaminated Land Exposure Assessment (CLEA) model for agricultural land scenarios in these two provinces. We found differences in the GAC between JS and ZJ due to differences in parameters. These differences are greatest for benzene, and cadmium (Cd). For Cd, the contribution of oral intake exceeds 90 %, and the vegetable consumption rate and mean daily intake (MDI) may be key parameters affecting GAC. For the volatile organic compound benzene, the inhalation of indoor vapor accounts for about 30 %, and the key parameters affecting the GAC for benzene may be the attenuation factor and soil organic matte (SOM). The derived GAC are generally lager (i.e., less stringent) than the GB15618-2018 and UK Suitable 4 Use Levels (S4ULs); however, the derived GAC for JS and ZJ were lower than the soil screening values (SSV) for residential land in China. This may be related to methods, land use types, and critical receptors. This work will contribute to the development of regional soil environmental standards in China.

Regional human health risk assessment of cadmium and hexachlorocyclohexane for agricultural land in China.

Widespread pollution of agricultural soil is posing great risks to food safety and human health. The absence of human health-based Generic Assessment Criteria (GAC) for agricultural land means Chinese farmers struggle to manage these risks efficiently and effectively. Cadmium (Cd) and hexachlorocyclohexane (HCH), two of the most concerned contaminants, demonstrate threshold toxicity meaning that background exposure (MDIoral) is considered when deriving soil Generic Assessment Criteria (GAC). The CLEA (Contaminated Land Exposure Assessment) model was used to derive GAC for Cd and HCH that reflect differences in diet and soil characteristics across 19 provinces/cities. For both cadmium and alpha-HCH, Sichuan had the lowest GAC of 0.379mgkg-1 and 0.0136mgkg-1, respectively, resulting from its significant high MDIoral values, which are approximately six to nine times larger than the average MDIoral for all the 19 provinces/cities. Jiangxi province had the highest GAC of 1.230mgkg-1 and 0.0866mgkg-1, respectively, for cadmium and alpha-HCH, caused by its notable low MDIoral values and low vegetable consumption rate. Human health risk assessment based on regional GAC for Cd revealed that agricultural land with very high to high risks is located in southern China, while very low-risk land is located in northern China. For HCH, alpha- and gamma-HCH pose negligible health risks, but beta-HCH poses some health risk in some of the provinces/cities. When applying the regional GAC for beta-HCH, agricultural land in Beijing and Sichuan posed the highest risk, and those in Heilongjiang and Jiangxi had the lowest risk. This reflects the significant influence of background and vegetable consumption pathway on the GAC. Regional GACs could simplify and speed up risk assessment of agricultural land in different regions of China, by avoiding the need to calculate site-specific assessment criteria, thus saving time and money by avoiding over or under remediation.

Use of simulated epithelial lung fluid in assessing the human health risk of Pb in urban street dust.

In many urban contexts, non-dietary Pb exposure from street dusts may add to the overall exposure burden, and the presence of high total Pb content is well documented in urban street dust from across the globe. Given the increasing recognition of the potential adverse health effects from both the quantity and the chemical and physical composition of the inhaled fraction, and the recognition that it is the soluble fraction rather than the total element content that has more direct links to health effects, attention has focused in this study on the human health risks via this exposure pathway. In order to investigate the environmental exposure to Pb from the inhalation of urban street dusts, a newly developed in vitro simulated epithelium lung fluid (SELF) has been applied to the <10μm fraction of urban street dusts. In this context, 21 urban street dust samples, across five UK cities, were selected based on their high pseudo-total Pb content. The work revealed that inhalation bioaccessibility, and hence inhalation dose, varied across the cities but was generally found to be low (<10%). Indeed, the lung bioaccessibility was far lower (% lung bioaccessibility ranged from 1.2 to 8.8) than is currently applied in two of the most commonly employed risk assessment models i.e. the Integrated Exposure Uptake Biokinetic model (IEUBK, USA) and the Contaminated Land Exposure Assessment model (CLEA, UK). The estimated inhalation dose (for adults) calculated from the PM10 bioaccessibility ranged from 7ngkg-1BWday-1 (Edinburgh) to 1.3ngkg-1BWday-1 (Liverpool). The results indicate a low potential inhalation bioaccessibility for Pb in these urban street dust samples when modelled using the neutral pH conditions of the SELF.

Evaluation of the impact of asbestos wastes on soils in Emene-Enugu, Southeastern Nigeria.

This study investigated the impacts of asbestos wastes on soils in Emene-Enugu, southeastern Nigeria, generated by the activities of a major asbestos products manufacturing company in southeastern Nigeria. The methods of investigation included vertical electrical sounding (VES), 2-D horizontal resistivity profiling (HRP), induced polarization (IP) survey, chemical analysis of plant tissues and standard penetration tests of soil samples. The 2-D HRP and IP identified six closed waste pits alongside the two active pits. The VES revealed four geoelectrical layers in the area: from bottom to top; the inferred lithologies included dark shale, clay, gravel and recent sands. The geochemical data results revealed that Cd concentration of the soils of the waste pits is above the contaminated land exposure assessment soil guideline value for residential and allotment land uses. The geochemical pollution indices classified the soils as "unpolluted" to "extremely polluted". Bioconcentration factor of Pb in plant tissues was found to be above recommended limits of 0.045. The geotechnical parameters indices revealed that the soils varied from "very soft" to "stiff" and "very loose" to "medium". Soils of the active pits have very low strength and bearing capacity while closed pits have high strength and bearing capacity. It may be safe, therefore, to conclude that as the wastes are completely turned into soils, they will assume geotechnical properties similar to those of natural soils.

Effects of pollution sources and soil properties on distribution of polycyclic aromatic hydrocarbons and risk assessment

In this study, the concentrations of polycyclic aromatic hydrocarbons (PAHs) in soil profiles and the soil properties were analyzed in Hunpu, a typical wastewater irrigation area, northeast of China. The total concentrations of 16 priority control PAHs ranged from 7.88 to 2,231.42μg/kg. Among 16 PAHs, the most abundant was Phenanthrene and the 3- or 4- ring PAHs were predominant. The PAH concentrations were higher in the upland fields near the oil wells, whereas leaching of PAH into the groundwater caused low concentrations in the paddy fields. The geochemical indices and the results from the principal component analysis of all 16 PAHs indicated that PAHs were mainly from atmospheric dusts in the top soil in I-1P/I-3P/I-7P and through soil profiles in I-4U/I-5P/I-8U, whereas those in the bottom layers were mainly from petroleum production and wastewater irrigation in I-1P/I-3P/I-7P and through soil profiles in I-2U and I-6U. In the redundancy analysis, PAHs exhibited negative correlation with pH, depth, silt, and clay, but had positive correlation with sand and organic matter. Finally, total toxic equivalent in the soil profiles and the calculated health risk of PAHs in the surface soil using contaminated land exposure assessment model elucidated the cancer risk that PAHs pose on human health in the Hunpu region.

Limitations of the CLEA model when assessing human health risks from dioxins and furans in soil at an allotments site in Rochdale, NW England

Many allotments in the UK today are situated on urban brownfield areas which creates a potential human health risk from soil borne contamination. This paper looks specifically at the risks to allotment users at a site in Rochdale, UK, from polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo-furans (PCDD and PCDF). A contaminated land investigation was undertaken involving the collection and analysis of 24 soil samples from the top 0.0-0.3 m of the soil profile. Homogenised egg samples were also collected and analysed from plots where poultry were kept. The concentration of PCDD and PCDF in soil at the site varied from 0.69 to 13.62 μg kg(-1); two plots out of a total of eight exceeded the soil guideline value (SGV) of 8 μg kg(-1), however all plots fell below the site specific assessment criteria (SSAC) of 15.9 μg kg(-1). Human health risks were assessed using the Environment Agency's contaminated land exposure assessment (CLEA) model. The assessment using CLEA alone did not provide enough evidence to indicate significant possibility of significant harm (SPOSH) across the entire allotment site. However, when the likely exposure from the soil was combined with potential exposure from consumption of site laid eggs, the results indicated that the potential risks could constitute SPOSH. This paper gives evidence to support the bioconcentration of PCDD and PCDF in eggs and highlights the importance of considering pollutant linkages outside the generic CLEA model.

Comparison of prediction methods for the uptake of As, Cd and Pb in carrot and lettuce

The New Model Framework (NMF) for uptake into crops is based on particle deposition and Transfer factors from soil to plant calculated from the BAse de données sur les teneurs en Eléments Traces métalliques de Plantes Potagères (BAPPET) database. Besides NMF, approaches developed by the National Institute of Public Health and the Environment (RIVM), Hough, and the United States Environmental Protection Agency (US EPA), and the Contaminated Land Exposure Assessment (CLEA) approach were tested. Experimental data were assembled from the BAPPET database and Danish background data of As, Cd and Pb in soil, air and crops was collected. None of the models proved able to estimate the measured concentrations in plants from the BAPPET database with an absolute normalized error smaller than 70%. On average, the predictions had an error of 80–250%. However, when applying the models to the rural Danish background scenario, the NMF and other models predicted the concentrations in carrot and lettuce within the range of measured values. Regressions considering soil pH, organic matter and clay content were not superior to simple transfer factors. The transfer from air to plant is significant, at least under background conditions, and should be considered in the prediction methods.

Accounting for pH heterogeneity and variability in modelling human health risks from cadmium in contaminated land

The authors have previously published a methodology which combines quantitative probabilistic human health risk assessment and spatial statistical methods (geostatistics) to produce an assessment, incorporating uncertainty, of risks to human health from exposure to contaminated land. The model assumes a constant soil to plant concentration factor ( CF veg) when calculating intake of contaminants. This model is modified here to enhance its use in a situation where CF veg varies according to soil pH, as is the case for cadmium. The original methodology uses sequential indicator simulation (SIS) to map soil concentration estimates for one contaminant across a site. A real, age-stratified population is mapped across the contaminated area, and intake of soil contaminants by individuals is calculated probabilistically using an adaptation of the Contaminated Land Exposure Assessment (CLEA) model. The proposed improvement involves not only the geostatistical estimation of the contaminant concentration, but also that of soil pH, which in turn leads to a variable CF veg estimate which influences the human intake results. The results presented demonstrate that taking pH into account can influence the outcome of the risk assessment greatly. It is proposed that a similar adaptation could be used for other combinations of soil variables which influence CF veg.

Plant uptake of organic chemicals: Current developments and recommendations for future research

Plant uptake of organic chemicals: Current developments and recommendations for future research

Bioaccessible arsenic in the home environment in southwest England

Samples of household dust and garden soil were collected from twenty households in the vicinity of an ex-mining site in southwest England and from nine households in a control village. All samples were analysed by ICP-MS for pseudo-total arsenic (As) concentrations and the results show clearly elevated levels, with maximum As concentrations of 486 microg g(-1) in housedusts and 471 microg g(-1) in garden soils (and mean concentrations of 149 microg g(-1) and 262 microg g(-1), respectively). Arsenic concentrations in all samples from the mining area exceeded the UK Soil Guideline Value (SGV) of 20 microg g(-1). No significant correlation was observed between garden soil and housedust As concentrations. Bioaccessible As concentrations were determined in a small subset of samples using the Physiologically Based Extraction Test (PBET). For the stomach phase of the PBET, bioaccessibility percentages of 10-20% were generally recorded. Higher percentages (generally 30-45%) were recorded in the intestine phases with a maximum value (for one of the housedusts) of 59%. Data from the mining area were used, together with default values for soil ingestion rates and infant body weights from the Contaminated Land Exposure Assessment (CLEA) model, to derive estimates of As intake for infants and small children (0-6 years old). Dose estimates of up to 3.53 microg kg(-1) bw day(-1) for housedusts and 2.43 microg kg(-1) bw day(-1) for garden soils were calculated, compared to the index dose used for the derivation of the SGV of 0.3 microg kg(-1) bw day(-1) (based on health risk assessments). The index dose was exceeded by 75% (18 out of 24) of the estimated As doses that were calculated for children aged 0-6 years, a group which is particularly at risk from exposure via soil and dust ingestion. The results of the present study support the concerns expressed by previous authors about the significant As contamination in southwest England and the potential implications for human health.

A spatially-evaluated methodology for assessing risk to a population from contaminated land

A methodology is proposed which combines quantitative probabilistic human health risk assessment and spatial statistical methods (geostatistics) to produce an assessment of risks to human health from exposure to contaminated land, in a manner which preserves the spatial distribution of risks and provides a measure of uncertainty in the assessment. Maps of soil contaminant levels, which incorporate uncertainty, are produced from sparse sample data using sequential indicator simulation. A real, age-stratified population is mapped across the contaminated area, and intake of soil contaminants by individuals is calculated probabilistically using an adaptation of the Contaminated Land Exposure Assessment (CLEA) model. An abundance of information is contained in results which can be interrogated at the population and individual level, and mapped to provide a powerful visual tool for risk managers, enabling efficient targeting of risk reduction measures to different locations.

Assessing exposure to pedogenic arsenic contamination at a dwelling in Northamptonshire, UK: a case study

Abstract. Soil associated with Northampton Sand within the area of the Borough Council of Wellingborough has elevated levels of arsenic. Arsenic in such soil at a private dwelling was analysed to determine the arsenic oral bioavailability and uptake by fruit and vegetables grown at the site. This information was used to assess the risk to a present occupant with 22 years' exposure, and to a 0–6‐year‐old girl, the critical receptor in the standard residential land use as stated in UK policy. The exposure pathways comprised soil and dust ingestion, consumption of home‐grown vegetables and ingestion of soil attached to home‐grown fruit and vegetables. The soil guideline value (SGV) for arsenic in residential land use with plant uptake derived using the Contaminated Land Exposure Assessment (CLEA) model was deemed inappropriate for use at this site, since the SGV does not include the consumption of home‐grown fruit, potentially a major pathway in this site for the current occupant, and also assumes 100% arsenic bioavailability. Hence, it was necessary to derive site‐specific assessment criteria for arsenic, for which we used the first edition of the Scotland and Northern Ireland Forum for Environmental Research (SNIFFER) framework, modified to reflect guidance in Contaminated Land Research (CLR) Reports CLR 9 and 10, and to incorporate the consumption of home‐grown fruit. The incorporation of site‐specific data on arsenic bioavailability and vegetable: soil arsenic concentration factor for the 0–6‐year‐old receptor gave a site‐specific assessment criterion (SSAC) of 139 mg kg−1 soil. For the adult female receptor, incorporating the site‐specific data on arsenic bioavailability, the vegetable: soil and the fruit: soil concentration factors gave a SSAC of 251 mg kg−1 soil. In both cases, the vegetable consumption pathway drives the risk. None of the 19 soil sample results for arsenic exceeded the site‐specific assessment criteria derived for the current occupiers, but 13 of the soil samples slightly exceeded the site‐specific assessment criteria for the putative 0–6‐year‐old girl. Given the degree of conservatism in the selection of input values for the exposure parameters in the SNIFFER framework, this exceedance was not considered to warrant further regulatory action at the time.

Metal contamination of urban soils in the vicinity of a municipal waste incinerator: One source among many

Concern from local residents about possible contamination with metals and PCDD/F (dioxins and furans) from fugitive and stack emissions from the Byker municipal solid waste incinerator in Newcastle upon Tyne led the City Council to initiate a study of the concentration of these pollutants in soils. We report here the results for the metals and arsenic. Soils were sampled at distances up to 2.25 km from the incinerator stack. The intensity of sampling in concentric zones was four times greater in the northeast (down-wind) direction, and twice as great in the northwest and southeast directions, compared to the southwest (up-wind) direction. In total 163 samples were collected and analyzed for total As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn. Concentrations were generally elevated above background levels, but were typical of those found in other urban areas. For As, Cd, Cu, Hg, Pb, and Zn, contamination hotspots were identified. These were spread throughout the sampling area, and there was no evidence of greater concentrations down-wind of the incinerator compared to other directions, nor of any trend in concentration at increasing distance from the incinerator. We concluded that metal contamination resulting from the incinerator could not be detected in an environment with generally elevated concentrations. Potential sources for many of the hotspots of contamination were identified in a survey of historic land use based on maps of the locality dating back to 1856. Detailed investigations of particular areas with serious contamination will now be undertaken by the local authorities using the CLEA (Contaminated Land Exposure Assessment) model.

Human health risk assessment using UK Guideline Values for contaminants in soils

Abstract In recent years the UK Department of the Environment has, with others, developed a framework for contaminated land risk assessment, including the derivation of new Guideline Values. These are an important component in an integrated procedure for site-specific risk assessment which combines consistency of approach with flexibility to ensure that local circumstances are taken into account. Guideline Values are derived using the Contaminated Land Exposure Assessment model (CLEA) which calculates human exposure via ten different exposure pathways. The relative contributions of the pathways vary according to site use, and hence the Guideline Values may also vary. This is consistent with the UK Government's ‘suitable for use’ policy. Guideline Values may also vary as a function of soil pH, soil organic matter, etc., reflecting the influence of such parameters on contaminant partitioning between soil solids and soil solution. The research described here is underpinned by complementary work to choose the most appropriate toxicological criteria for each contaminant. Where Guideline Values are exceeded, the intention is that either a further phase of risk assessment or remedial action is triggered. If the former is chosen the emphasis will be on establishing whether exposure conditions differ significantly from the generic conditions assumed in CLEA. This is expected to be more cost-effective in general than site-specific risk assessment procedures. It does, however, require that the exposure assumptions and data values used in deriving the Guideline Values are understood by the risk assessor so that the necessary comparisons with site-specific conditions can be made.