12The relative bioavailability of arsenic, antimony, cadmium and lead for the ingestion pathway was 22Using benchmark criteria for assessing the 'fitness for purpose' of the UBM bioaccessibility data to 23 act as an analogue for bioavailability in risk assessment, the study shows that the UBM met criteria

The Bioaccessibility Research Group of Europe (BARGE) has carried out an interlaboratory trial of a proposed harmonised in vitro physiologically based ingestion bioaccessibility procedure for soils, called the Unified BARGE Method (UBM). The UBM includes an initial saliva phase and simulated stomach and intestine compartments. The trial involved the participation of seven laboratories (five European and two North American) providing bioaccessibility data for As (11 samples), Cd (9 samples) and Pb (13 samples) using soils with in vivo relative bioavailability data measured using a swine model. The results of the study were compared with benchmark criteria for assessing the suitability of the UBM to provide data for human health risk assessments. Mine waste and slag soils containing high concentrations of As caused problems of poor repeatability and reproducibility which were alleviated when the samples were run at lower soil to solution ratios. The study showed that the UBM met the benchmark criteria for both the stomach and stomach & intestine phase for As. For Cd, three out of four criteria were met for the stomach phase but only one for the stomach & intestine phase. For Pb two, out of four criteria were met for the stomach phase and none for the stomach & intestine phase. However, the study recommends tighter control of pH in the stomach phase extraction to improve between-laboratory variability, more reproducible in vivo validation data and that a follow up inter-laboratory trial should be carried out.

1This paper presents a multi-laboratory comparison study of in vitro models assessing 2 bioaccessibility of soil-bound lead in the human gastrointestinal tract under simulated fasted 3 and fed conditions. Oral bioavailability data from a previous human in vivo study on the same 4 soil served as a reference point. In general, the bioaccessible lead fraction was significantly 5 (P<0.05) different between the in vitro methods and ranged for the fasted models from 2% to 6 33% and for the fed models from 7% to 29%. The in vivo bioavailability data from literature 7 were 26.2 ± 8.1% for fasted conditions, compared to 2.5 ± 1.7% for fed conditions. Under fed 8conditions, all models returned higher bioaccessibility values than the in vivo bioavailability, 9 whereas three models gave a lower bioaccessibility than bioavailability under fasted 10 conditions. These differences are often due to the method's digestion parameters that need 11 further optimization. An important outcome of this study was the determination that the 12 method for separating the bioaccessible lead from the non-bioaccessible fraction 13 (centrifugation, filtration, dialysis) is crucial for the interpretation of the results. 14 Bioaccessibility values from models that use more stringent separation methods better 15 approximate in vivo bioavailability results, yet at the expense of the level of conservancy. We 16 conclude from this study that more optimization of in vitro digestion models is needed for use 17 in risk assessment. Moreover, attention should be paid to the separation method since it 18 largely influences what fraction of the contaminant is considered bioaccessible. 19 20

An investigation for assessing pulmonary bioaccessibility of metals from reference materials is presented using simulated lung fluids. The objective of this paper was to contribute to an enhanced understanding of airborne particulate matter and its toxic potential following inhalation. A large set of metallic elements (Ba, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr, and Zn) was investigated using three lung fluids (phosphate-buffered saline, Gamble’s solution and artificial lysosomal fluid) on three standard reference materials representing different types of particle sources. Composition of the leaching solution and four solid-to-liquid (S/L) ratios were tested. The results showed that bioaccessibility was speciation- (i.e., distribution) and element-dependent, with percentages varying from 0.04% for Pb to 86.0% for Cd. The higher extraction of metallic elements was obtained with the artificial lysosomal fluid, in which a relative stability of bioaccessibility was observed in a large range of S/L ratios from 1/1000 to 1/10,000. For further investigations, it is suggested that this method be used to assess lung bioaccessibility of metals from smelter-impacted dusts.

The revised Environmental Protection Act Part 2A contaminated land Statutory Guidance (England and Wales) makes reference to 'normal' levels of contaminants in soil. The British Geological Survey has been commissioned by the United Kingdom Department for Environment, Food and Rural Affairs (Defra) to estimate contaminant levels in soil and to define what is meant by 'normal' for English soil. The Guidance states that 'normal' levels of contaminants are typical and widespread and arise from a combination of both natural and diffuse pollution contributions. Available systematically collected soil data sets for England are explored for inorganic contaminants (As, Cd, Cu, Hg, Ni and Pb) and benzo[a]pyrene (BaP). Spatial variability of contaminants is studied in the context of the underlying parent material, metalliferous mineralisation and associated mining activities, and the built (urban) environment, the latter being indicative of human activities such as industry and transportation. The most significant areas of elevated contaminant concentrations are identified as contaminant domains. Therefore, rather than estimating a single national contaminant range of concentrations, we assign an upper threshold value to contaminant domains. Our representation of this threshold is a Normal Background Concentration (NBC) defined as the upper 95% confidence limit of the 95th percentile for the soil results associated with a particular domain. Concentrations of a contaminant are considered to be typical and widespread for the identified contaminant domain up to (and including) the calculated NBC. A robust statistical methodology for determining NBCs is presented using inspection of data distribution plots and skewness testing, followed by an appropriate data transformation in order to reduce the effects of point source contamination.

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Editorial handling by M. Kersten a b s t r a c tSurface soils from a 19 km 2 area in east London, UK were analysed for polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB) (n = 76).P 16 PAH ranged from 4 to 67 mg/kg (mean, 18 mg/ kg) and P 50 PAH ranged from 6 to 88 mg/kg (mean, 25 mg/kg).P 7 PCB ranged from 1 to 750 lg/kg (mean, 22 lg/kg) and P tri-hepta PCB ranged 9 to 2600 lg/kg (mean, 120 lg/kg). Compared to other international cities concentrations were similar for PAH but higher for PCB. Normal background concentrations (NBC) were calculated and compared to risk-based human health generic assessment criteria (GAC). Benzo[a]pyrene NBC for urban (6.9 mg/kg), semi-urban (4.4 mg/kg) and urban + semi urban (6 mg/kg) domains exceed residential (1 mg/kg) and allotment (2.2 mg/kg) LQM/CIEH GAC (at 6% SOM) and the Indeno[1,2,3-cd]pyrene NBC for urban (6.8 mg/kg) and urban + semi-urban (5.2 mg/kg) domains exceed the residential (4.2 mg/kg) LQM/CIEH GAC (at 6% SOM). Capsule Abstract: Normal background concentrations of polycyclic aromatic hydrocarbons and polychlorinated biphenyls are elevated in east London soils and in some cases exceed regulatory assessment criteria.