Joop Harmsen

From Bioavailability Science to Regulation of Organic Chemicals

The bioavailability of organic chemicals in soil and sediment is an important area of scientific investigation for environmental scientists, although this area of study remains only partially recognized by regulators and industries working in the environmental sector. Regulators have recently started to consider bioavailability within retrospective risk assessment frameworks for organic chemicals; by doing so, realistic decision-making with regard to polluted environments can be achieved, rather than relying on the traditional approach of using total-extractable concentrations. However, implementation remains difficult because scientific developments on bioavailability are not always translated into ready-to-use approaches for regulators. Similarly, bioavailability remains largely unexplored within prospective regulatory frameworks that address the approval and regulation of organic chemicals. This article discusses bioavailability concepts and methods, as well as possible pathways for the implementation of bioavailability into risk assessment and regulation; in addition, this article offers a simple, pragmatic and justifiable approach for use within retrospective and prospective risk assessment.

Bioavailability as a tool in site management.

Bioavailability can form the basis for describing potential risks that contaminants pose to the environment and human health, and for determining remedial options to reduce risks of contaminant dispersal and toxicity. In assessments of polluted sites, methods to measure bioavailability can lead to a realistic appraisal of the potential risks from exposure to contaminants. For remediation purposes the application of the principles of bioavailability can result in practices that reduce bioavailability and consequently the risk of contaminants. Moreover the costs of remediation can be reduced. Examples from projects with organic contaminants (PAHs, pesticides and PFOS) and heavy metals in The Netherlands, Mali, Mauretania, Australia and Taiwan are presented. It is shown that using bioavailability principles in risk-based approaches is an attractive option in terms of both cost and in situ management of contaminated sites. Regulatory and public acceptance is, however, still the Achilles heel of these new remediation strategies.

Incorporating availability/bioavailability in risk assessment and decision making of polluted sites, using Germany as an example

Nearly all publications dealing with availability or bioavailability of soil pollutants start with the following statement: the determination of total pollutant content will lead to an over-estimation of risk. However, an assessment of contaminated sites should be based on the determination of mobile fractions of pollutants, and the fractions with potential for mobilisation that threaten groundwater and surface water, and the actual and potential fractions available for uptake by plants, soil microflora and soil organisms. After reviewing the literature for method proposals concerning the determination of available/bioavailable fractions of contaminants with respect to leaching, plants, microorganisms (biodegradation) and soil organisms, we propose a testing and assessment scheme for contaminated sites. The proposal includes (i) already accepted and used methods, (ii) methods which are under standardisation, and (iii) methods for which development has just started in order to promote urgently needed research.

Towards bioavailability-based soil criteria: past, present and future perspectives

Bioavailability has been used as a key indicator in chemical risk assessment yet poorly quantified risk factor. Worldwide, the framework used to assess potentially contaminated sites is similar, and the decisions are based on threshold contaminant concentration. The uncertainty in the definition and measurement of bioavailability had limited its application to environment risk assessment and remediation. Last ten years have seen major developments in bioavailability research and acceptance. The use of bioavailability in the decision making process as one of the key variables has led to a gradual shift towards a more sophisticated risk-based approach. Now a days, many decision makers and regulatory organisations ‘more readily accept’ this concept. Bioavailability should be the underlying basis for risk assessment and setting remediation goals of those contaminated sites that pose risk to environmental and human health. This paper summarises the potential application of contaminant bioavailability and bioaccessibility to the assessment of sites affected by different contaminants, and the potential for this to be the underlying basis for sustainable risk assessment and remediation in Europe, North America and Australia over the coming decade.

Accounting for Carbon Stocks in Soils and Measuring GHGs Emission Fluxes from Soils: Do We Have the Necessary Standards?

Soil is a key compartment for climate regulation as a source of greenhouse gases (GHGs) emissions and as a sink of carbon. Thus, soil carbon sequestration strategies should be considered alongside reduction strategies for other greenhouse gas emissions. Taking this into account, several international and European policies on climate change are now acknowledging the importance of soils, which means that proper, comparable and reliable information is needed to report on carbon stocks and GHGs emissions from soil. It also implies a need for consensus on the adoption and verification of mitigation options that soil can provide. Where consensus is a key aspect, formal standards and guidelines come into play. This paper describes the existing ISO soil quality standards that can be used in this context, and calls for new ones to be developed through (international) collaboration. Available standards cover the relevant basic soil parameters including carbon and nitrogen content but do not yet consider the dynamics of those elements. Such methods have to be developed together with guidelines consistent with the scale to be investigated and the specific use of the collected data. We argue that this standardization strategy will improve the reliability of the reporting procedures and results of the different climate models that rely on soil quality data.

Chemical Bioavailability in the Terrestrial Environment – recent advances

[ R. Schulin, R. Chaney, Bioavailability, definition, assessment and implications for risk assessment, in: Naidu et al. (Ed.), Chemical Bioavailability in Terrestrial Environment, Elsevier, Amsterdam, The Netherlands, 2008, pp. 39–52, ISBN: 978-0-444-52. The assessment of potential risk that contaminants pose to terestrial biota and public health is one of the most challenging tasks onfronting scientists today. This is due to the plethora of soil iochemical and physical processes controlling the fate of contamnants and the difficulty associated with the assessment of their ioavailability which is the underlying basis for exposure characerization. Research performed over the past 25 years has detailed hat the potential adverse impacts as a result of exposure to heavy etals and organic chemicals in soils is strongly influenced by ioavailability [2]. Risk assessment based on total contaminant conentration may provide conservative estimates of exposure due o the assumption that contaminants are 100% bioavailable. This onservative assessment of exposure may result in unnecessarily ow remediation goals, use of additional remediation resources and nwarranted remediation costs with flow on social and economical mplications. The bioavailability of contaminants in the terrestrial environent is a complex and dynamic process that is influenced by oth chemical and biological factors [1]. For example, the chemical rocess of sorption is generally thought to decrease the bioavailbility of contaminants in soils [3,4], while some evidence suggests hat biological processes (e.g. microbial activity) in soils may ncrease the bioavailability of contaminants to terrestrial orgaisms [5]. Although these distinct factors appear to influence the ate of contaminants in soils, little is known about their interplay n soil systems. In addition, despite considerable research, there till exists a lack of bioavailability predictive capabilities based n contaminant/soil/organism characteristics, how contaminant ioavailability affects soil quality and appropriate (unified) assays or the determination of contaminant bioavailability for a numer of key receptors. Some of the difficulties in the development f unified or standard methodologies arise due to differences in nterpreting bioavailability concepts and relating to this to the meaurement of contaminant bioavailability. In order to facilitate the ongoing advancement in contaminant ioavailability research, CRC CARE together with the Centre for nvironmental Risk Assessment and Remediation, University of outh Australia promotes a biennial international workshop series n “Chemical Bioavailability in the Terrestrial Environment”. The ain objective of the workshop is to exchange new and emerging cientific breakthroughs in contaminant bioavailability. In 2011, the Chemical Bioavailability in the Terrestrial Environent workshop was held in Adelaide with major themes focussing n: [