Bioaccessibility

Figure 1 Schematic of the UBM method
Figure 2 Plot of bioaccessibility vs bioavailability data for the UBM {Denys, 2012 #2714}

The Environmental Protection Act 1990: Part 2A – Contaminated Land Statutory Guidance (revised April 2012) has as overarching objectives to

  • Identify and remove unacceptable risks to human health and the environment
  • Seek to ensure that contaminated land is made suitable for its current use
  • Ensure that the burdens faced by individuals, companies and society as a whole are proportionate, manageable and compatible with the principles of sustainable development

In order to meet these there is therefore a clear need for a practical methodology that measures the fraction of the contaminant in the soil that can enter the systemic circulation of the human body and cause toxic effects. For Potentially Harmful Elements PHE) in soil, the most important exposure route is through ingestion and therefore measurement of oral bioaccessibility (a conservative estimate of bioavailability) of a substance, defined as the fraction that is soluble in the gastrointestinal environment and is available for absorption, is important for robust human health risk assessments.

BGS offers bioaccessibility testing of soils by the application of a methodology that simulates conditions in the gastrointestinal tract to assess the human bioaccessibility of potentially harmful elements by ingestion. The methodology applied has been developed by the BioAccessibility Research Group of Europe (BARGE) and known as the Unified BARGE Method or UBM (www.bgs.ac.uk/barge). The UBM (schematic in Figure 1) has been validated for arsenic, cadmium and lead against an in vivo model (Denys et al., 2012) and is in current use by BARGE research collaborators across Europe (see Figure 2 for example validation plot). These tests can be followed up with an investigation into the source of the potentially harmful elements using a method of Chemometric Identification of Substrates and Element Distribution (CISED) (Cave et al., 2004; Wragg and Cave, 2012).

The laboratory offers a package that includes the analysis for the total elemental concentration and the proportion of the element of interest that is extracted during the UBM as well as a loss on ignition at 450°C to determine the organic content of the soil and a determination of soil pH, which is accredited under the MCERTS Standard.

A second package incorporates the sequential leaching of a soil sample with increasing concentrations of aqua regia followed by analysis of the leachants for a wide range of major and trace elements. The analytical data are then analysed by a mathematical model for the CISED which provides a geochemical understanding of the controls on the PHE bioaccessibility.

Example applications of the UBM and CISED methodology are given in the references (Appleton et al., 2012; Appleton et al., 2008; Gal et al., 2007; Gal et al., 2006; Pelfrene et al., 2011; Roussel et al., 2010; Wragg et al., 2011) with further studies and technical information avaialble at the BARGE web site.

References

Appleton, J D, Cave, M R, and Wragg, J. 2012. Modelling lead bioaccessibility in urban topsoils based on data from Glasgow, London, Northampton and Swansea, UK. Environmental Pollution, Vol. in Press.

Appleton, J D, Rawlins, B G, and Thornton, I. 2008. National-scale estimation of potentially harmful element ambient background concentrations in topsoil using parent material classified soil:stream-sediment relationships. Applied Geochemistry, Vol. 23, 2596-2611.

Cave, M R, Milodowski, A E, and Friel, E N. 2004. Evaluation of a method for Identification of Host Physico-chemical Phases for Trace Metals and Measurement of their Solid-Phase Partitioning in Soil Samples by Nitric Acid Extraction and Chemometric Mixture Resolution. Geochemistry: Exploration, Environment, Analysis, Vol. 4, 71-86.

Denys, S, Caboche, J, Tack, K, Rychen, G, Wragg, J, Cave, M, Jondreville, C, and FEIDT, C. 2012. In Vivo Validation of the Unified BARGE Method to Assess the Bioaccessibility of Arsenic, Antimony, Cadmium, and Lead in Soils. Environmental Science & Technology, Vol. 46, 6252-6260.

Gal, J, Hursthouse, A, and Cuthbert, S. 2007. Bioavailability of arsenic and antimony in soils from an abandoned mining area, Glendinning (SW Scotland). Journal of Environmental Science and Health Part A, Vol. 42, 1263 - 1274.

GAL, J, Hursthouse, A S, and Cuthbert, S J. 2006. Chemical availability of arsenic and antimony in industrial soils. Environmental Chemistry Letters, Vol. 3, 149-153.

Pelfrene , A, Waterlot, C, Mazzuca, M, Nisse, C, Bidar, G, and Francis, D. 2011. Assessing Cd, Pb, Zn human bioaccessibility in smeltercontaminated agricultural topsoils (northern France). Environmental Geochemistry and Health.

Roussel, H, Waterlot, C, Pelfrene, A, Pruvot, C, Mazzuca, M, and Douay, F. 2010. Cd, Pb and Zn oral bioaccessibility of urban soils contaminated in the past by atmospheric emissions from two lead and zinc smelters. Arch Environ Contam Toxicol, Vol. 58, 945-954.

Wragg, J, and Cave, M. 2012. Assessment of a geochemical extraction procedure to determine the solid phase fractionation and bioaccessibility of potentially harmful elements in soils: A case study using the NIST 2710 reference soil. Analytica Chimica Acta, Vol. 722, 43-54.

Wragg, J, Cave, M R, Basta, N, Brandon, E, Casteel, S, Denys, S E B, Gron, C, Oomen, A, Reimer, K, Tack, K, and Van De Wiele, T. 2011. An Inter-laboratory Trial of the Unified BARGE Bioaccessibility Method for Arsenic, Cadmium and Lead in Soil. Science of the Total Environment, Vol. 409, 4016-4030.

Contact

Please contact Dr Michael Watts for further information