EN ISO 17402:2011

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Kakovost tal - Zahteve in navodilo za izbiro in uporabo metod za ocenjevanje biološke razpoložljivosti onesnaževal v tleh in talnih (zemeljskih) materialih (ISO 17402:2008)Bodenbeschaffenheit - Anleitung zur Auswahl und Anwendung von Verfahren für die Bewertung der Bioverfügbarkeit von Kontaminanten im Boden und in Bodenmaterialien (ISO 17402:2008)Qualité du sol - Lignes directrices pour la sélection et l'application des méthodes d'évaluation de la biodisponibilité des contaminants dans le sol et les matériaux du sol (ISO 17402:2008)Soil quality - Requirements and guidance for the selection and application of methods for the assessment of bioavailability of contaminants in soil and soil materials (ISO 17402:2008)13.080.05Preiskava tal na splošnoExamination of soils in generalICS:Ta slovenski standard je istoveten z:EN ISO 17402:2011SIST EN ISO 17402:2011en,fr,de01-november-2011SIST EN ISO 17402:2011SLOVENSKI
STANDARD
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN ISO 17402
June 2011 ICS 13.080.01 English Version
Soil quality - Requirements and guidance for the selection and application of methods for the assessment of bioavailability of contaminants in soil and soil materials (ISO 17402:2008)
Qualité du sol - Lignes directrices pour la sélection et l'application des méthodes d'évaluation de la biodisponibilité des contaminants dans le sol et les matériaux du sol (ISO 17402:2008)
Bodenbeschaffenheit - Anleitung zur Auswahl und Anwendung von Verfahren für die Bewertung der Bioverfügbarkeit von Kontaminanten im Boden und in Bodenmaterialien (ISO 17402:2008) This European Standard was approved by CEN on 10 June 2011.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2011 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 17402:2011: ESIST EN ISO 17402:2011

Reference numberISO 17402:2008(E)© ISO 2008
INTERNATIONAL STANDARD ISO17402First edition2008-06-15Soil quality — Requirements and guidance for the selection and application of methods for the assessment of bioavailability of contaminants in soil and soil materials Qualité du sol — Lignes directrices pour la sélection et l'application des méthodes d'évaluation de la biodisponibilité des contaminants dans le sol et les matériaux du sol
ISO 17402:2008(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
©
ISO 2008 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body in the country of the requester. ISO copyright office Case postale 56 • CH-1211 Geneva 20 Tel.
+ 41 22 749 01 11 Fax
+ 41 22 749 09 47 E-mail
copyright@iso.org Web
www.iso.org Published in Switzerland
ii © ISO 2008 – All rights reserved
ISO 17402:2008(E) © ISO 2008 – All rights reserved iii Contents Page Foreword.v Introduction.vi 1 Scope.1 2 Normative references.1 3 Terms and definitions.2 4 Bioavailability in relation to assessment of soil function.6 4.1 Soil functions and organisms to protect.6 4.2 Risk assessment.6 4.3 Protection goals.7 5 Concepts of bioavailability.8 5.1 Definitions.8 5.2 Links between bioavailability and biological effects and/or bioaccumulation.10 6 Description of methods to assess bioavailability.11 6.1 General.11 6.2 Assessment of bioavailability using chemical test methods.12 6.3 Assessment of bioavailability using ecotoxicological test methods.13 7 Pathways related to soil quality (both organism and soil).14 7.1 General.14 7.2 Human.14 7.2.1 General.14 7.2.2 Soil ingestion.14 7.2.3 Dermal contact.15 7.2.4 Inhalation of soil.15 7.2.5 Groundwater used for drinking water.15 7.3 Exposure of higher animals.15 7.4 Exposure of soil organisms.15 7.4.1 General.15 7.4.2 Exposure of soil micro-organisms.15 7.4.3 Exposure of soil invertebrates (micro-, meso- and macro-fauna).16 7.5 Exposure of plants.16 8 Available methods to measure bioavailability.17 8.1 General.17 8.2 Chemical methods to measure environmental availability.17 8.2.1 General.17 8.2.2 Methods for soil ingestion.18 8.2.3 Methods for dermal uptake.19 8.2.4 Methods for plants.19 8.2.5 Methods for leaching from the solid phase to the soil solution.19 8.2.6 Methods for biodegradation.20 8.2.7 Methods for soil organisms.20 8.2.8 Available and promising chemical methods to measure bioavailability.20 8.3 Ecotoxicological test methods to measure bioavailability.22 9 Requirements.25 9.1 General.25 9.2 Requirements for selection and application.25 9.2.1 Requirements for selection.25 9.2.2 Requirements for application.26 SIST EN ISO 17402:2011

ISO 17402:2008(E) iv © ISO 2008 – All rights reserved 9.3 Requirements for development.27 Annex A (informative)
Bioavailability in relation to biodegradability.29 Annex B (informative)
International Standards for the determination of the toxicity of chemicals on sediment organisms (laboratory tests).30 Bibliography.31
ISO 17402:2008(E) © ISO 2008 – All rights reserved v Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 17402 was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 7, Soil and site assessment. SIST EN ISO 17402:2011

ISO 17402:2008(E) vi © ISO 2008 – All rights reserved Introduction Laboratory and field studies have demonstrated that biological effects are not related to the total concentration of a contaminant in the soil. Instead, an organism responds only to the fraction that is biologically available (bioavailable) for that organism. This is particularly true in soils that undergo interaction of contaminant molecules with the soil, in such a way that the contaminant is not attainable anymore by the organism or is present in a non-available form (sometimes referred to as sequestration or irreversible sorption). The bioavailable fractions of contaminants are dependent on soil properties and various processes varying with time and on the biological receptors. The conservative approach of exposure assessment, as typically described in a regulatory context, assumes that the total concentration of a contaminant present in a soil or soil material is available for uptake by organisms, including man, and as such will overestimate the risks. Therefore, a risk assessment can be optimised by using an approach that is based on estimated exposure representing the available, effective concentration of the contaminant(s) and on (existing) intrinsic toxicity data. This assumption is not new as, already in the last half of the nineteenth century, agronomists and soil scientists began to search for chemical methods to determine the concentration of individual plant-available nutrients in agricultural soils. The impetus for this search was the need for recommended nutrient additions to achieve maximum crop yield. Mulder [1] stated already in 1860: “The unnecessary full analysis of soil to learn if it is fertile or not cannot be argued enough. The long and short of it is availability, which cannot be derived beforehand. The analysis shows what there is, agriculture must draw its own conclusions from that.” Chemical methods were devised to reasonably predict the availability of inorganic ions necessary for plant development. Chemical partial extraction methods are now commonly used to evaluate available levels of nutrients in soils. Extraction methods have been optimised by correlating extraction results with response of susceptible crop species to the addition of fertilisers. The concept of availability is nowadays applied to the risk assessment of contaminants and can be tailored to the specific protection goals. Depending on the intended use of a soil or soil material, soil characterisation for different purposes (e.g. assessment of habitat and retention functions, risk assessment and compliance with regulatory values) may include chemical testing and ecotoxicological testing with selected representative test organisms. These tests will, in many cases, be soil- or site-specific at a given point in time, and cannot be extrapolated to other soils or points in time where other factors may control bioavailability. Bioavailability may be assessed in two complementary ways (see also Figure 1): ⎯ Chemical methods (e.g. extraction methods) which determine the fraction of a well-defined class of contaminants available for defined specific biotic receptors or the mobility of the contaminants in the soil. Usually these chemical methods were developed to predict the amount of contaminants taken up by the organisms. Nevertheless, these analytically determined values can also be correlated with effects. In a routine assessment of soil quality, chemical measurements may replace biological testing, if a correlation between the resulting chemical values and effect or accumulation has been demonstrated. ⎯ Biological methods which expose organisms to soil or soil eluates in order to monitor effects. If accumulation and/or effects (e.g. mortality, growth inhibition) are encountered, bioavailable contaminants are likely to be present even if they cannot be chemically identified. More knowledge on processes controlling bioavailability can close the still existing gap between chemical measurements and biological effects. SIST EN ISO 17402:2011

ISO 17402:2008(E) © ISO 2008 – All rights reserved vii
Figure 1 — Methods to assess bioavailability — Relation between chemical and biological assays and bioaccumulation Under regulatory aspects of soil protection, the risk assessment should be based upon the same common concept with regard to determination/assessment of exposure and measurement/assessment of effects. Thus, existing concepts and derived trigger values based on total concentrations of pollutants in soils or soil materials can be transferred to the proposed concept based on the prediction of the bioavailable fraction by using the more accurate description of exposure. For instance, the translation of information on bioavailability into acceptable evaluations of “how clean is clean” (e.g. site-specific limits for regulating the extent to which the remediation of soil is required) is essential for establishing realistic risk assessments and the determination of proper endpoints for remediation. A harmonised framework on bioavailability is considered in order to promote the development and introduction of workable standard methods to be used in soil and site assessment. In addition, methods for the estimation of bioavailable effective concentrations of contaminants according to the protection goals envisaged are required. These methods should preferably be described in International Standards and that standardization process should result in a limited set of established methods for the measurement of bioavailability [2]. As described in this International Standard, this process will not lead to one single method to measure bioavailability, because bioavailability depends on variables such as the contaminant, the target and the actual soil properties. Therefore, methods should not only use the word bioavailability but also refer to these variables (bioavailable for). In this International Standard, requirements and guidance are given to select methods to assess bioavailability for different target species with regard to several classes of contaminants. Methods to assess bioavailability are not described in this International Standard. Reference is made to existing International Standards and additional principles of measurement, which may need to be worked out in these International Standards. As only a few standards exist, reference is also made to measuring principles. Guidance is also provided for further standardization of a method where promising first results are reported. After a short description of methods (Clause 6), the pathways of a contaminant to the target organism are discussed (Clause 7). A summary of existing methods and promising methods that should be further developed is given in Clause 8. Clause 9 gives recommendations and includes the minimal requirements for application and further development.
INTERNATIONAL STANDARD ISO 17402:2008(E) © ISO 2008 – All rights reserved 1 Soil quality — Requirements and guidance for the selection and application of methods for the assessment of bioavailability of contaminants in soil and soil materials 1 Scope This International Standard provides guidance for the selection and application of methods to assess bioavailability for the characterisation of contaminated soil and soil materials. This International Standard does not give a selection of the best applicable methods, but specifies boundary conditions and principles of methods to be used and gives the minimal requirements for the development of methods. The results obtained from such methods can be used as an estimate of bioavailability in a risk-assessment approach. In this International Standard, when the term “soil” is only quoted for simplification, the broader term “soil and soil material” shall be considered. The contaminants considered in this International Standard are metals, including metalloids, and organic contaminants, including organometal compounds. This International Standard is also applicable to metals originating from natural geological and pedological processes (natural pedo-geochemical content). This International Standard can also be applied to sediments. NOTE An assessment procedure based on the bioavailable fraction of the total amount of contaminants in the soil or soil material can contribute to the development of regulatory requirements of risk-based assessment procedures for soils. According to the protection goals envisaged, applications of existing methods are recommended and their limitations discussed, with the intention of promoting the development and introduction of workable standard methods to be used in soil and site assessment. These methods are required to allow for the quantification of factors influencing bioavailability. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 11074:2005, Soil quality — Vocabulary ISO/TS 21268-1:2007, Soil quality — Leaching procedures for subsequent chemical and ecotoxicological testing of soil and soil materials — Part 1: Batch test using a liquid to solid ratio of 2 l/kg dry matter SIST EN ISO 17402:2011

ISO 17402:2008(E) 2 © ISO 2008 – All rights reserved 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 11074 and the following apply. 3.1 bioavailability degree to which chemicals present in the soil may be taken up or metabolised by human or ecological receptors or are available for interaction with biological systems NOTE 1 Adapted from ISO 11074:2005. NOTE 2 The concept of bioavailability is further explained in Clause 5. NOTE 3 In ISO/TS 17924, a definition specific for human uptake through ingestion is given as the fraction of a substance present in ingested soil that reaches the systemic circulation (blood stream). 3.2 contaminant substance or agent present in the soil as a result of human activity [ISO 11074:2005] NOTE There is no assumption in this definition that harm results from the presence of the contaminant. 3.3 critical body residues CBR internal concentration accumulated in a tissue, organ or all of the body that is correlated with an adverse effect 3.4 environmental availability fraction of contaminant physico-chemically driven by desorption processes potentially available to organisms NOTE 1 See also Figure 2. NOTE 2 Environmental availability contains 1) an actual available fraction or the actual dissolved amount of pollutant at ambient conditions, or 2) a potentially available fraction, which is the maximum amount that can be released under (predefined) worst-case conditions. The potentially available fraction includes the actual available fraction. 3.5 environmental bioavailability fraction of the environmentally available compound which an organism takes up through physiologically driven processes NOTE See also Figure 2. 3.6 habitat function ability of soil/soil materials to serve as a habitat for micro-organisms, plants, soil-living animals and their interactions (biocenosis) [ISO 11074:2005] SIST EN ISO 17402:2011

ISO 17402:2008(E) © ISO 2008 – All rights reserved 3 3.7 leaching test test during which a material is put into contact with a leachant under strictly defined conditions and some constituents of the material are extracted [ISO/TS 21268-1:2007] 3.8 leachant liquid used in a leaching test [ISO/TS 21268-1:2007] 3.9 natural pedo-geochemical content concentration of a substance in soils, resulting from natural geological and pedological processes, excluding any addition of human origin [ISO 11074:2005] NOTE In the background content [concentration of a substance in soil, resulting from natural geological and pedological processes, including diffuse source inputs (ISO 19258)], the natural pedo-chemical content is combined with the content resulting from diffuse pollution. 3.10 pollutant substance or agent present in the soil (or groundwater), which due to its properties, amount or concentration causes adverse impacts on soil functions or soil use NOTE Adapted from ISO 11074:2005. 3.11 potentially harmful substance substance which, when present in a sufficient concentration or amount, may be harmful to humans or the environment NOTE It may be present as a result of human activity or naturally. 3.12 receptor potentially exposed person or part of ecosystem 3.13 retention function ability of soils/soil materials to adsorb pollutants in such a way that they cannot be mobilised via the water pathway and translocated into the terrestrial food chain [ISO 11074:2005] NOTE In this International Standard, reversible adsorption and desorption processes are also considered. 3.14 sediment or subhydric soil soil and its parent material beneath the surface water body SIST EN ISO 17402:2011

ISO 17402:2008(E) 4 © ISO 2008 – All rights reserved 3.15 soil upper layer of the Earth's crust composed of mineral particles, organic matter, water, air and living organisms NOTE 1 In a broader civil engineering sense soil includes top-soil and subsoils; deposits such as clays, silts, sands, gravels, cobbles, boulders and organic deposits such as peat; and materials of natural origin or of human origin (e.g. fills and deposited wastes). NOTE 2 Adapted from ISO 11074:2005. 3.16 soil material material coming from soil and displaced and/or modified by human activity, including excavated soil, dredged materials, manufactured soils, and treated soils and fill materials NOTE For the purposes of this International Standard, sediments are considered as soil material. 3.17 soil organisms all organisms living completely, or during specific parts of their lifetime, in the soil or on the soil surface (including the litter layer) and which contribute to soil processes (e.g. nutrient cycling), including plants (including soil algae), microflora, invertebrate and (a few) vertebrate species 3.18 toxicological bioavailability internal concentration of pollutant accumulated and/or related to a toxic effect NOTE 1 See also Figure 2. NOTE 2 This definition refers to internal concentrations in humans, mammals and other organisms. SIST EN ISO 17402:2011

ISO 17402:2008(E) © ISO 2008 – All rights reserved 5
Figure 2 — From total concentration in soil to effect (modified after Reference [7] in the Bibliography) SIST EN ISO 17402:2011

ISO 17402:2008(E) 6 © ISO 2008 – All rights reserved 4 Bioavailability in relation to assessment of soil function 4.1 Soil functions and organisms to protect Assessment of soil quality is relevant in a number of situations, for example, when contaminated soil and soil materials have to be evaluated for the degree of necessary clean-up, when excavated soil is to be reused for a specific purpose, or when land areas are to be evaluated with respect to proper land use. This assessment is very dependent on the availability of the contaminants in question, but other important factors are the presence or absence of a relevant type of receptor and its sensitivity to the contaminant. Bioavailability cannot be discussed without stating for whom the availability is relevant. In ISO 11074, the retention and habitat functions (see Clause 3) are distinguished. They include the following specific soil functions: ⎯ control of substance and energy cycles as components of ecosystems; ⎯ basis for the life of plants, animals and man; ⎯ carrier of genetic reservoir; ⎯ basis for the production of agricultural products; ⎯ buffer inhibiting movement of water, contaminants or other agents into groundwater. Apart from the retention and habitat functions and risk-assessment schemes derived, other scenarios, including the uptake of soil by humans (children's playgrounds) (see ISO/TS 17924) or by higher animals like grazing cattle, may be considered in an assessment procedure. This can be described more specifically as follows: ⎯ (bio)availability for different but defined target soil organisms or biotopes (habitat or retention); ⎯ (bio)availability for organisms able to transform or mineralise the contaminant (habitat); ⎯ (bio)availability for plant uptake (habitat); ⎯ (bio)availability for human uptake (ingestion, inhalation, dermal contact) (habitat); ⎯ (bio)availability for leaching processes (retention). 4.2 Risk assessment Characterisations of bioavailability should be performed as a part of a risk and/or compliance assessment. A risk assessment comprises the following steps. Step 1 The hazard identification: which in this context is the recognition of the potential of a substance to cause harm to human health or the environment. Step 2 The exposure assessment: which is the process of establishing whether, and how much, exposure will occur between a receptor and a contaminated source. The contact time or exposure time is an important parameter for the exposure. Step 3 The dose-response assessment: which is the characterisation of the relationship between the dose (exposure) of a chemical and the anticipated incidence of an adverse health or environmental effect in an exposed population. Dose-response assessments are typically carried out at national level as a part of the setting of criteria and are thus usually not undertaken as a part of the assessment of a specific site. Step 4 Finally, and based on the above: the risk characterisation, a description of the nature and magnitude of a health or environmental risk. The description combines results of exposure assessment and hazard identification and describes the uncertainty associated with each step. SIST EN ISO 17402:2011

ISO 17402:2008(E) © ISO 2008 – All rights reserved 7 The exposure assessment (step 2) is the process wherein the intensity, frequency, and duration of the exposure of the receptor in question to a contaminant are estimated, and it comprises: ⎯ source identification and characterization; ⎯ identification of exposure routes; ⎯ identification of relevant receptors/target groups; ⎯ and, based on this, the actual exposure assessment. Exposure assessments can be carried out in order to assess either the total exposure of a given receptor group (e.g. the population at risk) or the additional exposure from a given source or activity. Since, in this International Standard, only the risk resulting from the exposure to soil contaminants is addressed, it is limited to the direct contact of the target with soil. Other indirect effects like consumption of crops growing on contaminated land are part of an assessment procedure, but the bioavailability of contaminants in consumed crops is not a subject of this International Standard. The actual exposure routes will depend on the site use. Both the actual and planned use of a contaminated area may be included in the assessment, as this may define which exposure routes are of relevance. Average, worst or reasonable-case exposure can be evaluated, and depending on the purpose of the exposure assessment, the data needs can differ for these situations. The actual exposure time can differ between similar site uses due to differences in climate and actual site use patterns (e.g. number of days per week that the site is in use). 4.3 Protection goals In soil assessment, the protection goal is a leading principle. The following protection goals can be distinguished. ⎯ Human and higher animals: ⎯ humans; ⎯ grazing animals, e.g. cattle; ⎯ wildlife. ⎯ Soil habitat function: ⎯ invertebrates; ⎯ soil micro-organisms; ⎯ vegetation; ⎯ food web (food web should be a protection goal, but as follows from this International Standard, it is not possible to have one single method to establish bioavailability for the whole foodweb). ⎯ Soil retention function: ⎯ water organisms; ⎯ groundwater and surface water. NOTE With regard to exposure in connection with groundwater, reference is made to ISO 15175. In ISO 15175, it is also considered that the mobile fraction of the total contaminant concentration controls groundwater exposure based on a similar hypothesis to that used in the bioavailability concept. Because the mobile contaminant fraction can also provide a good prediction of the bioavailable fraction for organisms in contact with the pore water, the mobile fraction is also described in this International Standard on bioavailability. SIST EN ISO 17402:2011

ISO 17402:2008(E) 8 © ISO 2008 – All rights reserved Depending on the potential use of the land — nature conservation, forests, pastures, arable land, paddy fields, horticulture, allotments, playgrounds, parks, below sealed areas, industrial areas or landfill covering — protection goals may differ. For instance, in playgrounds, human beings are the protection goals, while in nature conservation the goals mentioned under the habitat and retention function have to be considered. In industrial areas, it is usually most important to protect the groundwater (retention function). Defining the protection goals is a part of the assessment procedure and is not described in this International Standard. 5 Concepts of bioavailability 5.1 Definitions The definition of bioavailability (3.1) is comprehensive, but is not explicit enough as a definition of bioavailability as a measurable quantity. Bioavailability depends on a specific target organism and specific contaminants and includes the following aspects: exposure time, transfer of contaminants from soil to organisms, their accumulation in the target organisms and the subsequent effects. For practical purposes, more specific definitions have been derived, for example as follows: ⎯ bioavailability is the flux of contaminants to biota [3]; ⎯ bioavailability is the amount of chemicals in the soil that are present in forms and amounts that plants or other organisms can take up during the time they are alive [4]; ⎯ bioavailability is the rate at which a chemical compound can be transported to the specified biological population [5]. These definitions can be grouped into two categories, for example, the bioavailability defined in terms of flux or rate (mol⋅m−2⋅s−1) and that defined in terms of content (mol⋅kg−1). Theoretically, the content-based bioavailability is obtained by integrating the rate- or flux-based bioavailability over a period of interaction. In practice, it is difficult to directly measure the rate of processes, and the flux- or rate-based bioavailability is estimated from content-based bioavailability. Therefore, the content-based bioavailability is of primary importance from an evaluation point of view. It should be realised that a content-based bioavailability is based on a net flux of the chemical to the target organism or organ. Bioavailability can conceptually be defined as a dynamic process, which can be described by the following three steps (Figure 2): a) availability of the contaminant in the soil (e.g. environmental availability); b) uptake of the contaminant by the organism (e.g. environmental bioavailability); c) within the organisms, accumulation and/or effect of the contaminant (e.g. toxicological bioavailability) [6], [7]. Bioavailability is considered as soil- or organism-dependent but many organisms, as is the case for plants, may also modify soil characteristics (e.g. pH changes in the rhizosphere) making contaminants more or less available. Because the total exposure of organisms depends on time, the available fraction is not a fixed fraction, but should be divided into more fractions or described as a continuum. The release of the contaminants (see Figure 3) depends on local environmental conditions (e.g. pH). The simplest approach is to define ⎯ an actual available fraction or the actual dissolved amount at ambient conditions, ⎯ a potentially available fraction, which is the maximum amount that can be released under (predefined) worst-case conditions, and ⎯ a non-available fraction. SIST EN ISO 17402:2011

ISO 17402:2008(E) © ISO 2008 – All rights reserved 9 The potentially available fraction includes the actual available fraction but cannot exceed the total concentration. To establish the potential bioavailability, it is important to define the total system: soil, including the organisms, and environmental conditions that influence the fate of a contaminant in the soil or the activity of organisms. The subdivision in terms of actual and potential availability is important because it broadens the role of the pore water. Bioavailability covers not only the amount in the pore water, but may include the amount that desorbs during the time an organism is in contact with the soil. Regarding the organisms, a “bioinfluenced” zone could be defined [8]. This zone comprises the pore water and, depending on the organism, parts of the soil matrix. Consequently, the available concentration may have different values depending on the type of target organisms and time scale and, in turn, there could be numerous specific definitions (operational definition). The bioavailability processes are also discussed in Reference [9] in the Bibliography. This description combines the conceptual and operational definition as used in this International Standard. Bioavailability is also used to predict the amount of degradation of organic contaminants in a remediation process (see Annex A). With biodegradation, it is assumed that organisms degrade the contaminant. Bioavailability is used to predict a decrease of contaminant concentration. In a successful approach, the conceptual definition, the operational definition and the used tool should have relations as indicated in Annex A.
Key X total concentration CBR Y chemical response, bioaccumulation, biological response A Zone A: the contaminant is detected, but there is no detectable effect B Zone B: concentration-response curves parallel for chemical and biological assays: then the chemical assay constitutes a useful surrogate test C Zone C: assays become non-linear and correlation is lost 1 chemical assay 2 bioaccumulation 3 biological effect 4 bioassay a Possible correlation between biological/chemical; chemical assay = useful surrogate test. Figure 3 — Response of chemical assays and bioassays as a function of the total concentration (modified after Reference [8] in the Bibliography) SIST EN ISO 17402:2011

ISO 17402:2008(E) 10 © ISO 2008 – All rights reserved 5.2 Links between bioavailability and biological effects and/or bioaccumulation Whichever definition is used, the only direct way of measuring bioavailability for an organism to be protected is the use of that organism to measure the accumulation and/or effect (e.g. toxicological bioavailability). If this is not possible because of ethical (e.g. with higher organisms like human beings) or ecological (e.g. too many species in the ecosystem to be tested) reasons, one way could be to use surrogate species. They can then be used as indicators to study potential effects on and/or accumulation in the organism to be protected or the functional groups or total ecosystem. It should be kept in mind that, due to intra- and inter-species variations, the results obtained with the surrogate may not be extrapolated to the specific receptor to be protected. As an example, if the protected organisms are human beings, the surrogate organism to assess toxicological bioavailability may be a pig, and a chemical test may also be developed in order to determine environmental availability. If one considers the protection of plants or soil invertebrates, surrogate species may be used (e.g. lettuce, earthworms) for which a chemical test may also be developed. If environmental bioavailability (i.e uptake of the contaminant) for an organism or a group of organisms in a soil can be mimicked by a chemical process, then a chemical test can be used. The required condition to approximate environmental bioavailability with a chemical test which estimates the environmental availability is that a function exits between both in a statistical sense (Figure 3, Zone B). In general, since the rate of the mimicking chemical process is not the same to that of actual uptake processes, the time needed to estimate environmental availability is not the same (usually less time is necessary) compared to that for environmental bioavailability. Figure 3 shows the relationship between chemical assays, biological effects and bioaccumulation. Only in Zone B do chemical and biological tests give parallel responses, meaning that the chemical method can be a surrogate of the biological one. The internal concentration which results from the uptake and accumulation can be used as a link to the observed effect, providing that the organism is not able to eliminate the contaminant. This concentration is defined as critical body residues [8]. As shown previously, we cannot have a general definition of bioavailability. ⎯ For this International Standard, the content- or concentration-based bioavailability is of primary importance from the experimental point of view. ⎯ Bioavailability is strongly linked to the exposure
...