New Publication on Planetary Boundaries for Chemical Pollution

Here is the final version of our paper entitled ”Exploring the planetary boundary for chemical pollution”, which was just published in Environment International. Paywall, unfortunately. But drop me an email if you’d like a reprint.

The publication is the outcome of a workshop that my colleague Sverker Mollander organised a while back. Thanks for setting things in motion, Sverker!

The abstract reads as follows:

Rockström et al. (2009a, 2009b) have warned that humanity must reduce anthropogenic impacts defined by nine planetary boundaries if “unacceptable global change” is to be avoided. Chemical pollution was identified as one of those boundaries for which continued impacts could erode the resilience of ecosystems and humanity. The central concept of the planetary boundary (or boundaries) for chemical pollution (PBCP or PBCPs) is that the Earth has a finite assimilative capacity for chemical pollution, which includes persistent, as well as readily degradable chemicals released at local to regional scales, which in aggregate threaten ecosystem and human viability. The PBCP allows humanity to explicitly address the increasingly global aspects of chemical pollution throughout a chemical’s life cycle and the need for a global response of internationally coordinated control measures. We submit that sufficient evidence shows stresses on ecosystem and human health at local to global scales, suggesting that conditions are transgressing the safe operating space delimited by a PBCP. As such, current local to global pollution control measures are insufficient. However, while the PBCP is an important conceptual step forward, at this point single or multiple PBCPs are challenging to operationalize due to the extremely large number of commercial chemicals or mixtures of chemicals that cause myriad adverse effects to innumerable species and ecosystems, and the complex linkages between emissions, environmental concentrations, exposures and adverse effects. As well, the normative nature of a PBCP presents challenges of negotiating pollution limits amongst societal groups with differing viewpoints. Thus, a combination of approaches is recommended as follows: develop indicators of chemical pollution, for both control and response variables, that will aid in quantifying a PBCP(s) and gauging progress towards reducing chemical pollution; develop new technologies and technical and social approaches to mitigate global chemical pollution that emphasize a preventative approach; coordinate pollution control and sustainability efforts; and facilitate implementation of multiple (and potentially decentralized) control efforts involving scientists, civil society, government, non-governmental organizations and international bodies.

Rockström, J., Steffen, W., Noone, K., Persson, A., Chapin, F.S., Lambin, E., Lenton, T.M., Scheffer, M., Folke, C., Schellnhuber, H.J., Nykvist, B., de Wit, C.A., Hughes, T., van der Leeuw, S., Rodhe, H., Sorlin, S., Snyder, P.K., Costanza, R., Svedin, U., Falkenmark, M., Karlberg, L., Corell, R.W., Fabry, V.J., Hansen, J., Walker, B., Liverman, D., Richardson, K., Crutzen, P., Foley, J., 2009a. Planetary boundaries: exploring the safe operating
space for humanity. Ecol. Soc. 14 ([online] URL:

Rockström, J., Steffen, W., Noone, K., Persson, A., Chapin, F.S., Lambin, E.F., Lenton, T.M., Scheffer, M., Folke, C., Schellnhuber, H.J., Nykvist, B., de Wit, C.A., Hughes, T., van der Leeuw, S., Rodhe, H., Sorlin, S., Snyder, P.K., Costanza, R., Svedin, U., Falkenmark, M., Karlberg, L., Corell, R.W., Fabry, V.J., Hansen, J., Walker, B., Liverman, D., Richardson, K., Crutzen, P., Foley, J.A., 2009b. A safe operating space for humanity. Nature 461, 472–475.

Empowering academic research in chemical risk assessment and management

The following text will appear as an editorial in Integrated Environmental Assessment and Management in the April 2015 issue. As usual a button for a printer-friendly format is found at the bottom of the text.

Scientists in the fields of toxicology and ecotoxicology are expected to explain how chemicals act on organisms and ecosystems and to make predictions that help guide regulatory actions and policy-making. The role of academic science in this context is challenged time and again, often with the argument that its contributions are not sufficiently in line with regulatory approaches for chemical risk assessment and management. Here we argue that nonconformity in academic research should be welcomed because academia’s crucial role is that of examination and forecasting of science, policy, and social issues potentially looming on the horizon.

Academic scientists are motivated to explore unknown phenomena, new chemicals, and novel endpoints. They often engage in exploratory toxicological or ecotoxicological research that delivers a posteriori hypotheses about cause-effect relationships, modes and mechanisms of action, and susceptible biocenoses, species, organs, tissues or cells. This type of research searches for patterns, devises novel theoretical models, and develops new experimental techniques. It is useful for determining whether a condition or problem warrants further investigation and, if so, provides the information for appropriate research designs and data collection methods. Such work often embraces John Tukey’s (1962) philosophy that it is “far better to have an approximate answer to the right question, which is often vague, than an exact answer to the wrong question, which can always be made precise”. Exploratory research informs regulatory chemical risk assessment and management, but rarely are the results sufficient for final regulatory decision-making.

Confirmatory research, on the other hand, is inherently narrower in scope and starts with a well-defined a priori hypothesis. It confirms or refutes a pre-specified causal relationship or mechanism of toxic action, underpins the relevance of a phenomenon, and maximizes Society’s confidence in the work presented. Confirmatory research is often intended to provide the regulatory community with the data needed to derive robust quantitative conclusions on the toxicological or ecotoxicological consequences of chemical exposure.

A great deal of value of academic science lies in exploratory research and the ability to build critical, long-term perspectives on current practices and the consequences of human activity. Researchers in academia should therefore strive to be more than service providers for regulatory risk assessment. Rather, academics should contemplate how regulatory goals, for example the substitution of hazardous chemicals with less harmful alternatives, could be implemented, or how new methods and tools could strengthen regulatory practice. Academic research in toxicology and ecotoxicology should prepare the foundation for the next generation of regulatory guidelines, which are urgently needed in an increasingly interconnected world with limited natural resources and planetary boundaries that are becoming more and more obvious.

Consequently, education in academic research institutions should provide the platforms for training the next generation of critically thinking scientists that have the intelectual capacity to ask fundamental and challenging questions about chemical interactions with the environment and human health. Education should, of course, teach students both current and new or emerging analytical tools and techniques; but education should also emphasize the limitations of current knowledge and how different laboratory and field-based studies support or distract from scientifically sound chemical risk assessment and management.

Academic research, happily ignoring prescriptive regulatory practices, guidelines, and the (eco)toxicological ‘flavor of the month’, is absolutely vital for the continuous development of new ecotoxicological and toxicological knowledge needed to solve tomorrow’s problems. The tendency to pressure academia – via grants and continuous external and internal evaluations – to justify the immediate societal value of every activity therefore warrants more critical assessment.

Academic research is increasingly built on external funding, and public institutions providing the funding rarely agree to sponsor confirmatory studies. Herein lies a challenge facing the present day chemical management as a whole: the role of the impartial, confirmatory analyst in toxicology and ecotoxicology is largely vacant. Confirmatory research in business is largely focused on chemicals and human activities immediately relevant to a particular business, and therefore not always sufficiently systematic and publicly disseminated, as well as sometimes embued with conflict of interest. Regulatory authorities often lack the financial, laboratory capacity, and technical resources necessary to build upon or confirm the results of exploratory research. Consequently, the lack of systematically planned, well implemented, documented, and disseminated confirmatory research constitutes a critical gap in our ability to assess and manage chemical risks.

Regulatory guidelines serve specific purposes, but scientific discovery and the exploration of unknown phenomena are not amongst them. This, however, does not imply that results generated from non-standard, exploratory approaches should be readily dismissed. The two volumes of “Late Lessons from Early Warnings”, published by the European Environment Agency in 2001 and 2013 [1,2] should remind us that high quality academic research can properly motivate early regulatory actions. Regrettably, assessment approaches and decision criteria addressing when and how regulatory agencies should respond to academic research (exploratory or otherwise) remain largely lacking.

The body of toxicological and ecotoxicological knowledge must be safeguarded from incomplete knowledge and spurious results. In the long run, this obligation can only be met by supporting a collaborative combination of exploratory and confirmatory research that is published and discussed in the open scientific literature.

Academic institutions have enjoyed centuries of postulating and opining on all facets of science, often leaving the task of discerning the practicality, relevance, and usefulness of academic research to business, governments, and other institutions. This needs to change, particularly with the aim to improve chemical risk assessment and management. The academic community needs to find its voice and engage more actively in promoting the value of academic research for the long-term development of toxicology and ecotoxicology and its benefits to Society.

1. European Environmental Agency, Late lessons from early warnings: the precautionary principle 1896-2000. Environmental Issue Report 22, 2001. Available at the Agency’s website for direct download (PDF)
2. European Environmental Agency, Late lessons from early warnings: science, precaution, innovation, Report 2013/1, 2013. Available at the Agency’s website for direct download (PDF)

Prof. Thomas Backhaus
Senior Editor, Integrated Environmental Assessment and Management
University of Gothenburg, Sweden

Dr. Xenia Trier
Technical University of Denmark, Denmark

New publication on mixtox assessment for the registration of new biocidal products

Here’s a new one that has just been published in its final version:

Backhaus, T, Altenburger R, Faust M, Frein D, Frische T, Johansson P, Kehrer A, Porsbring T: Proposal for environmental mixture risk assessment in the context of the biocidal product authorization in the EU, Environmental Sciences Europe, 2013, 25:4, DOI: 10.1186/2190-4715-25-4

It’s Open Access, so can directly download the paper here:


Review frustration…

I have been reviewing six manuscripts in the last weeks. And half of them were written by young, inexperienced lead authors, with rather experienced senior authors. The typical setup for the first manuscript that results from a PhD project.

Which makes things interesting on the one hand – some genuinely interesting new thoughts. But it was also frustrating. Simply because all authors were struggling to explain things that they are quite familiar with to an outside audience – and were also often falling into the trap of trying to be complete (“I’ll explain the world on 20 manuscript pages”).

I (vaguely) remember my first attempts to put things on paper. And I also remember that at least one of my co-authors always took care of the manuscript before submission. Which obviously took him more time than writing the damn’ thing himself.

However, I can’t shake the feeling that a lot of the seniors are now trying to delegate this task to the external reviewers (or maybe I simply had bad luck with the manuscripts that ended on my desk). Anyway, the texts did very obviously did not go through any internal review prior to submission. That’s the only reason that I can come with why for example a manuscript led by a non-native speaker with no publication record to be found in Scopus, but with a (very) experienced US senior author has dozens of spelling and grammar mistakes.

Frustrating for (almost) everybody involved – and cudos to everybody who actually does invest the time to go through the manuscript with his/her PhD student before submitting it to a journal.

Thomas (slightly annoyed)

New Publication: Conceptual Framework for Mixture Risk Assessment

We just published the following policy analysis in ”Environmental Science and Technology”:

Thomas Backhaus, Michael Faust: “Predictive environmental risk assessment of chemical mixtures: a conceptual framework” DOI:10.1021/es2034125.

Abstract: Environmental risks of chemicals are still often assessed substance-by-substance, neglecting mixture effects. This may result in risk underestimations, as the typical exposure is towards multi-component chemical “cocktails”. We use the two well established mixture toxicity concepts (Concentration Addition (CA) and Independent Action (IA)) for providing a tiered outline for environmental hazard and risk assessments of mixtures, focusing on general industrial chemicals and assuming that the “base set” of data (EC50s for algae, crustaceans, fish) is available. As mixture toxicities higher than predicted by CA are rare findings, we suggest applying CA as a precautious first tier – irrespective of the modes/mechanisms of action of the mixture components. In particular, we prove that summing up PEC/PNEC ratios might serve as a justifiable CA-approximation, in order to estimate whether there is a potential risk for an exposed ecosystem in a first tier assessment if only base-set data are available. This makes optimum use of already existing single substance assessments as more demanding mixture investigations are requested only if there are first indications of an environmental risk. Finally we suggest to call for mode-of-action driven analyses only if error estimations indicate the possibility for substantial differences between CA- and IA-based assessments.

One of the central discussion points of the paper is the comparison between the sum of PEC/PNECs and the sum of Toxic Units. Especially the use of PEC/PNEC sums has been challenged, for example in the recent SCHER opinion which states that “[…] a combination of PNECs may be misleading.” The mathematical analysis of the relationship between the sum of PEC/PNECs and the sum of Toxic Unis (which is a widely accepted implementation of Concentration Addition) is published as supporting information to the paper and is freely available. ES&T doesn’t make it available (yet) on their website, so here’s a direct link.

I always feel a bit awkward doing that during the review process or even in the final manuscript. But I have to say that I was really impressed by the amount of work and critical comments that we received by some of our reviewers (as usual, there was an outlier…). “Critical” in the positive sense of the word – the feedback really helped fine-tuning the text. So, whoever you are: thanks a lot, much appreciated!


New publications

proofs We just finished two manuscripts that are online now:

Silva, E., Rajapakse, N., Scholze, M., Backhaus, T., Ermler, S., Kortenkamp A. Joint effects of heterogeneous estrogenic chemicals in the E-Screen – exploring the applicability of concentration addition. Tox Sciences, in press doi:10.1093/toxsci/kfr103

Backhaus, T., Porsbring, T., Arrhenius, A., Brosche, S., Johansson, P., Blanck, H. Single substance and mixture toxicity of 5 pharmaceuticals and personal care products to marine periphyton communities, Env. Tox. Chem, in press doi:10.1002/etc.586

The first one provides details on the predictability of the joint action of various mixtures of endocrine disrupters in the well-known E-Screen. Usually, Concentration Addition works rather well, but we found some interesting patterns. To simply summarize from the paper:

[…] we identified estrogen mixtures that followed CA, but statistically significant deviations from additivity occurred with mixtures that contained both steroidal estrogens
665 and synthetic estrogenic chemicals. There are some indications that the observed weak antagonisms are related to differential expression of CYP 1B1, although it is likely that additional factors are also at play.

The second one also goes for the investigations of mixture effects (surprise, surprise…). But this time on a completely different level. Switching the scenery from a proliferation assay with an isolated breast cancer cell line to a study analysing the impact of pharmaceutical mixtures on ecological succession in microbial communties. However, a (sort of) similar result: in principle the mixtures were ”well behaved”, but on the fringes it became obvious that we are only dealing with coarse models of reality. In the case of the biofilm communities, we saw strong stimulatory effects (hormesis) – but only in the mixture, not in the single substances. To be frank, currently we can only speculate on the reasons for this pattern. Our current hypothesis revolves around indirect effects caused by one of the compounds in the mixture.

When talking about hormesis, I would like to provide another quote from the paper:

It should finally be pointed out that hormetic effects of a chemical or chemical mixture certainly cannot be considered the opposite of harmful, adverse ecological effects. Similarly to an inhibition of growth, they indicate a disturbance of the network and interactions within an ecological community. An assessment of their implications for risk assessment, however, is not possible without further detailed knowledge on the underlying causes.

This paragraph was introduced following a comment from one of the reviewers of that manuscript. So, thanks for that suggestion!

Actually, I was really impressed with the quality of both reviews that we received for this manuscript – they certainly added a lot of critical reflection to the manuscript. And provided some food for thought (and follow-up studies). Sometimes peer-review still works nicely…

And my sincere apologies to the editoral staff of ET&C who had to suffer through my not always optimum response times – and an initially missing figure in the final version of the manuscript.