Development of Acute Generic Assessment Criteria for Assessing Risks to Human Health from Contaminants in Soil

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# ACUTE GACs

Issue Date: 30th April 2019

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.

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Development of Generic Assessment Criteria for Assessing Vapour Risks to Human Health from Volatile Contaminants in Groundwater (updated September 2024)

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# GROUNDWATER VAPOUR

SoBRA 2017

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:

cis-1,2-Dichloroethene
trans-1,2-Dichloroethene
1,2-Dichloroethane
Tetrachloroethene (PCE)
Naphthalene
Chloroethene (Vinyl Chloride (VC))
Benzene
Trichloroethene (TCE)

Download report V2.0 September 2024

Conceptual Framework for Asbestos Risk Assessment & Control

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# ASBESTOS

SoBRA 2015

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.

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Design of an Activity Based Sampling Protocol for the Testing of Asbestos Fibre Release Potential from Residential Garden Soil

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# ASBESTOS

SoBRA 2015

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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Dust Monitoring Protocol for Earthwork Activities at Brownfield Sites

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# DUST

SoBRA 2015

The aim is to obtain robust activity-based dust generation data to be able to risk-rank different remediation, earthwork and construction activities, and better understand potential fugitive environmental emissions and employee exposures. This protocol is designed to provide a monitoring method by which different activities involving earthworks at brownfield sites can be monitored in a consistent way and the data from each monitoring exercise collated to inform the potential for dust release and the subsequent risk ranking of those activities.

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Soil Sampling Protocol for Asbestos in Soil

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# ASBESTOS

SoBRA 2015

This protocol provides a draft outline of a potential sampling approach developed by the SoBRA Asbestos-in-soil sub-group. It aims to strike a balance between traditional soil survey sampling strategies and soil sampling strategies designed specifically for known asbestos containing soil, made ground and aggregate.

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