This is a good but also a difficult question. A lot of bioavailaibility research has been done in the last two decades, whereas the implementation of bioavailability parameters into regulation is still going rather slow. The first obstacle is the poor definition of the word bioavailability, which means very different things for different researchers. I suggest that you specify which specific bioavailability parameter you have in mind, since this should give a better feedback from and discussion within the research community.

Within a soil pollution context, the most widely accepted concept seems "bioaccessibility" that basically quantifies the part of the total pollutant content in the soil, which can be released under certain conditions. Several bioaccessibility extraction methods have been developed for organic xenobiotics, but they do not always provide sufficient sink capacity during the extraction, which then can lead to an underestimation of bioaccessibility. Several research groups are thus working on a new generation of bioaccessibility extraction methods that integrate a sorptive sink to increase the sink capacity..

Within a contaminated sediment context, the most widely accepted concept is "freely dissolved concentration" which expresses the chemical activity of the pollutants and the effective concentration for partitioning and diffusive uptake. It is the basis for the equilibrium partitioning theory introduced by Di Toro in the early 1990s. Since then  several partitioning based methods (i.e. equilibrium passive sampling) have been developed for the measurement of freely dissolved concentrations in sediments at ng/L, pg/L and even fg/L levels, and these methods are increasingly used to measure rather than estimate freely dissolved concentrations. It is my impression that passive sampling and freely dissolved concentrations are becoming rather accepted within research, monitoring and also risk assessment and management of contaminated sediments.

Finally, within a human exposure and toxicology context, "bioavailability" again means something completely different.

You are likely very aware of these differences. I mention them here, because I believe that a prerequisite for further developments in this area is that we use well  defined and clear terms. While "bioavailability" and "bioavailable concentrations" might be usefull and descriptive on a general level, they should in my opinion be replaced with more precise terms when doing research or implementing bioavailability parameters into environmental assessment, regulation and management of soil and sediment pollution. 

The following references might be relevant to look at:  

https://www.researchgate.net/publication/259003613_Passive_sampling_methods_for_contaminated_sediments_Scientific_rationale_supporting_use_of_freely_dissolved_concentrations

https://www.researchgate.net/publication/230767426_Sorptive_Bioaccessibility_Extraction_%28SBE%29_of_Soils_Combining_a_Mobilization_Medium_with_an_Absorption_Sink

https://www.researchgate.net/publication/41760242_Low_accessibility_and_chemical_activity_of_PAHs_restrict_bioremediation_and_risk_of_exposure_in_a_manufactured_gas_plant_soil

https://www.researchgate.net/publication/7077663_Two_complementary_sides_of_bioavailability_accessibility_and_chemical_activity_of_organic_contaminants_in_sediments_and_soils

Article Passive sampling methods for contaminated sediments: Scienti...

Article Sorptive Bioaccessibility Extraction (SBE) of Soils: Combini...

Article Low accessibility and chemical activity of PAHs restrict bio...

Article Two Complementary Sides of Bioavailability: Accessibility an...

     Dear Philipp,

    Thank you for your comment. Yes, I am aware of the different connotations of the term... Jean-Claude Block (Nancy, France) and I co-edited a NATO book on bioavailability 15 years ago, in which these various notions were described in detail, and analyzed by a number of authors...

    For the purposes of this question in ResearchGate, all I wanted to find out is whether in some countries, environmental regulations are considering that, for one reason or another, one should not base policy decisions on the total amount of organic xenobiotic present in a given soil or sediment, but one should make provision "sequestration" processes that may make these compounds less "available"...

Hi Philippe,

I checked some information for the Netherlands. There are a few publications from the National Institute of Public Health and the Environment (RIVM) focused on implementation of bioavailability in Dutch regulatory framework. See:

"Towards implementation of bioavailability measurements in the Dutch regulatory framework" (2009)

http://www.rivm.nl/dsresource?objectid=rivmp:19196&type=org&disposition=inline&ns_nc=1

and

"Advice on implementing bioavailability in the Dutch soil policy framework (2012)

http://www.rivm.nl/dsresource?objectid=rivmp:121498&type=org&disposition=inline&ns_nc=1

But as you know such implementations take a lot of time. From formal information like letters to Parliament of the Ministry of Infrastructure and Environment, I cannot derive any action or progress towards this specific regulation in soil policies. Last document was a letter of March 10, 2014 on modernisation of environmental policy, but that letter is stated in general terms without detail on this subject:

http://www.tweedekamer.nl/downloads/document?id=967be72e-fe25-49ec-aca0-6c178e06b56c&title=Modernisering%20Milieubeleid.pdf

Anyway, there seems to be some movement around this theme.....

it has not been considered yet in Taiwan. But, we talked about it recently in the EPA agency.

A limited but common organic and inorganic contaminants have soil standards in New Zealand. The central government National Environmental Standard (NES) does regulate the disturbance of already contaminated land for subdivision purposes. In determining such standards the Ministry for the Environment did give regard to effects on human health(including produce uptake). The context within which such standards were developed was for the purpose of sustainably using contaminated land hence the effects of derived standards on wider environment (soil biota etc) was not considered.

To view further details, NES wordings and contaminant standards (the required levels are in pages 84 and 85) please visit http://www.mfe.govt.nz/publications/rma-land-hazards/users-guide-national-environmental-standard-assessing-and-managing. This site is managed by the Ministry for the Environment, New Zealand.

A SETAC Europe Special Science Symposium covering this issue was held in Brussels last October. More information and the presentations are available at:

http://sesss10.setac.eu/home/?contentid=779&pr_id=778

We are currently working on a paper presenting the conclusions of this workshop and these will also be presented at the SETAC Europe meeting in Barcelona.

Hi Philippe,

Following John Parsons answer, you may find Willie Peijnenburgs contribution at the SETAC symposium with recent information on implementation in the Netherlands: http://sesss10.setac.eu/embed/sesss10/presentations/Willie_Peijnenburg.pdf

The content but not bioavailability is mentioned in Polish law. More information you can obtain from Dr Grzegorz Siebielec from National Institute of Soil Science and Plant Cultivation [email protected]

Hi Philippe,

Interesting and very welcome study as discussions on the integration of bioavailable pollutant shares in regulation last already for 20 years. Austrian regulation - still - uses total concentrations to derive soil quality criteria for organic contaminants. For metals, however, the amount extracted with ammonia nitrate may be used to assess risks.

Four years ago, an Austrian study report (German, Summary in English) was published regarding the risk assessment of historically contaminated sites, it covers also contaminants present in soil:

http://www.umweltbundesamt.at/aktuell/publikationen/publikationssuche/publikationsdetail/?pub_id=1935

This is a guidance document that sets out to the provision of instructions for site- and use-specific human exposure assessment of historically contaminated sites. One could understand this as framework that also allows for a consideration of the bioavailable pollutant fraction (with respect to human health) in exposure assessment. However, no guidance on how to accomplish this is given. Nor is information on the selection of methods to quantify the “bioavailable” fraction provided.

In essence, for organic xenobiotics there are no guideline or threshold concentrations in Austria that are based on the concept of bioavailability although the advantages of using this concept are obvious.

The ambiguity inherent in the term bioavailability is one reason for its limited acceptance by regulators. Their might also be non-scientific hurdles to overcome such as the complexity of communicating risk associated to chemical activity rather than to a total concentration. Probably more simple to integrate in a risk assessment framework is the maximum amount of pollutants that can be released from soil at given or anticipated conditions. This pollutant share is described as bioaccessible fraction and methods are available for quantification. Resulting numbers might be used by risk assessors and regulators less hesitantly - given that data provide a long term prediction of pollutant release.

http://www.umweltbundesamt.at/aktuell/publikationen/publikationssuche/publikationsdetail/?pub_id=1935

Hi Phillipe,

I have contacted the Danish EPA in order to get the correct answers for Denmark.

Within the last 10 years, there have been discussions and considerations about whether and how to include "bioavailability" into setting legal limits for organic pollutants in soils. However, such legal limits are still expressed on the basis of total concentrations, and bioavailability considerations have not been used to adjust these limits. It is still possible (and I think likely) that bioavailability/bioaccessibility measurements, considerations and arguments have been applied in specific cases.

Your survey clearly shows that bioavailability considerations do still not play a very central role within the regulation and management of polluted soils in most countries. For sediments there seems to be more progress. One obstacle might be the underlying assumption in this area, that there is a desorption resistant pollutant fraction that gives rise to very limited if any exposure. During the last 5 years we have tried to confirm/challenge this assumption, and we plan to publish the results this year.

Good luck with your review, and please feel free to contact me by mail if you would like to discuss further or more input

Philipp Mayer

Two years ago, I posted this question, with the full intention to write a review article on bioavailability in the following Spring. And I am really thankful for some of the feedback. Unfortunately... other writing projects got in the way, and I did not get to it. Recently, I got things re-started. I feel that, more than ever, there is a need for a decent review article on the topic. Next Autumn, I plan to have in my lab. a young, enthusiastic Spanish scientist, who will work with me on this review, and the two of us will get it done by December. I am excited by this prospect, and I know that the result will be very interesting. So, if any of you find yourself near Paris (France) this coming Autumn, and you would like to help us work on this review article, feel free to let me know and I will be glad to host you at AgroParisTech. My general attitude is that there is more in three heads than in two...

Risk based regulatory limits do that take into account in soil and groundwater remediation arena. Unfortunately, it is still generic standard in Taiwan soil and groundwater standards.

Dear T.Y. Yeh,

I am not sure I understand your comment. Do you mean to say that in Taiwan, regulatory standards do not take bioavailability into account?

Philippe

Dear Dr. Philippe

Unfortunately, the answer is yes

Ty 

For those who, at some point at least, followed this question on the bioavailability of organic xenobiotics in soils and sediments, you may be interested to know that this Autumn, in Grignon (near Paris), I will be working with Dr. María Balseiro Romero on a critical review of the literature on the topic. We hope to submit the manuscript for publication by the end of December. If you are near Paris, and would like to contribute to this critical review, let me know and we will arrange for a visit and discussions.

Dear Philippe,

I have forwarded your question to RIVM for an update of the status in the Dutch soil quality regulation. This is their answer by mrs. Joke Weezenbeek:

 RIVM has explored the possibilities for involving the bioavailability of organic substances in assessing the soil quality. However, this assessment is still based on measured total levels of chemicals. The only correction that has a relation to bioavailability is the "soil type correction", which means that for low-organic soil (and thus probably high bioavailability), a more stringent standard applies to the total content than for soil with a lot of organic matter. This is explained in the Circular Soil Remediation, Annex 1 (in attachment, last update 2013). In addition, a so-called TRIAD assessment can be applied to determine the urgency of soil remediation, while the field survey also implicitly takes bioavailability into account (see Annex 2, section 5.3).

An overview of Dutch soil legislation and other related information can be found at a specific page of Rijkswaterstaat http://rwsenvironment.eu/subjects/soil/legislation-and/

kind regards,

Marcel