This interactive Microsoft Powerpoint toolbox has been designed by the SoBRA asbestos sub-group to assist risk assessors in undertaking asbestos in soil human health risk assessments. It is a collation of the information sources and practices of the sub-group members, assembled in the form of a flowchart. The toolbox provides users with summary information and links to relevant external reference sources, and advocates a process by which asbestos in soil risk assessment can be carried out. It is hoped that it will aid in the consistency and robustness of asbestos in soil risk assessment.
SoBRA’s asbestos sub-group surveyed UK laboratory methods for the identification and quantification of asbestos in soil back in 2018-2019. With the withdrawal of the Standing Committee of Analysts (SCA) Blue Book method for the quantification of asbestos in soil last year this paper should help in understanding some of the key differences in the methods used by laboratories, and it also makes recommendations for how asbestos results should be reported to best inform subsequent risk assessment.
SoBRA is pleased to announce the publication of further work by its Asbestos Sub-Group. Since a workshop held in April 2019 the sub-group has been working on revision to the discussion white paper published in 2017 on air quality guidelines for asbestos. A key action from that workshop in 2019 was to evaluate the use the linear as well as the non-linear versions of the risk algorithms published by Hodgson & Darnton in 2000. It was the view of the participants of the workshop that the linear model for pleural mesothelioma might be more appropriate for the calculation of risk from low environmental exposures compared to the higher occupational exposures that were the primary focus of the Hodgson & Darnton paper. The updated SoBRA paper presents a comparison of risk models, including the new application of the Hodgson & Darnton algorithms. A beta version of an Excel-based spreadsheet (Jan 2024) has been developed to support the updated paper, allowing users to select from the algorithm options presented in the Hodgson & Darnton (2000) paper and the Darnton (2003) paper, and therefore enabling users to perform model choice sensitivity analysis and evaluate the difference the use of alternative algorithms makes to estimated risk. It is hoped that the updated paper and supporting Excel tool help further our understanding of potential health risk associated with exposure to airborne asbestos.
This discussion paper is a continuation of the series of discussion papers that the SoBRA asbestos sub-group has published since 2015. In 2013, SoBRA identified a number of research gaps that had direct relevance to the risk management of asbestos in soil. One of these was the lack of a collective understanding on what typical background concentrations of asbestos in soil across the UK were. To provide a complementary line of evidence to Defra’s recently published Research Project SP1014 (Establishment of typical background levels of dispersed asbestos fibres in urban and rural soils in England and Wales), SoBRA issued a request to major UK soil laboratories to provide SoBRA with anonymised asbestos in soil data. The principal aim of this paper is to provide a factual presentation of the data provided by the laboratories. The information presented may be used by risk assessors and decision makers as a line of evidence as they see fit.
This report presents a methodology for derivation of AGAC that risk assessors may choose to use to help in the assessment of acute health risks from short-term exposure to contaminants in soil. In the UK, the assessment of risks to humans from land contamination has traditionally tended to focus on chronic exposure scenarios. However, focusing on chronic exposure may not always be protective of potential acute exposure scenarios, especially in non-residential settings, and/or if statistical methods are used to interpret site soil data. The report was developed to address the absence of such guidance in order to support risk assessment practitioners and promote awareness within the contaminated land sector.
27 July 2020 Corrigendum : The authors of SoBRA’s AGAC report have discovered an error in the calculation of the AGACs for the vapour pathway for benzene (adult and child), phenol (child), trichloroethene (adult and child) and vinyl chloride (child). These had been incorrectly calculated due to use of log Koc rather than Koc in the calculation spreadsheets. A new version of the report (version 2) has been produced with these values corrected (the new AGAC are higher than before) which is available on the link below.
Volatile constituents in groundwater have the potential to cause risk to human health via volatilisation and migration of vapours into overlying buildings or outdoor air space followed by inhalation. Where the conceptual site model identifies this contaminant linkage as being of possible concern it is usually necessary to assess the risks further in order to determine whether they are acceptable or not. One method that can be used is to compare measured concentrations of volatile constituents in groundwater with conservative generic assessment criteria (GAC) protective of human health via the inhalation of groundwater-derived vapours pathway. This helps the assessor determine the level of risk associated with this particular contaminant linkage. A working group of the Society of Brownfield Risk Assessment (SoBRA) has developed a methodology and derived GAC for 66 commonly analysed volatile constituents in groundwater. The methodology utilises the Environment Agency’s (England and Wales) CLEA model to estimate the average long-term concentration in shallow groundwater (the GAC) that would lead to tolerable/minimal risk to site occupants from vapour migration and inhalation in indoor and outdoor air from chronic exposure. Screening values have been derived for residential and commercial land-use scenarios. The generic screening values are intended to complement other screening methodologies (such as exclusion depths and distances) for assessing the groundwater vapour contaminant linkages.
The report was originally published in 2017 and has been updated in 2024 (V2.0) to take account of the publication of eight Category 4 Screening Levels (C4SLs). The groundwater vapour GAC have been updated with the input parameters used in the derivation of the C4SLs for:
The aim of the approach is to have a common framework that can scale to any number of activities that might take place prior, pre, during or post development. The key aims are to have a stepwise approach to enable effective screening of potential areas of concern; encourage appropriate and sufficient data collection and site investigation to support robust decision making; facilitate timely identification and understanding of risky activities and identify the point where mitigation and further Quantitative Risk Assessment is necessary to protect vulnerable on and off site receptors.
This protocol provides a draft outline of a potential activity-based sampling approach for the testing of asbestos fibre release potential from residential garden soil as part of a staged investigation strategy for land being investigated under Part 2A of the Environmental Protection Act 1990. The primary objective of the Activity-Based Sampling (ABS) protocol is to provide a reasonable worst-case estimate of current and future fibre-release and subsequent localised airborne fibre concentrations that might be possible as a result of soil disturbance.
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