Speaker abstracts

Setting the scene: Is mixtures risk assessment necessary and feasible? Andreas Kortenkamp, The School of Pharmacy, University of London, 29-39 Brunswick Square, London WC1N 1AX, United Kingdom.

There is currently considerable interest in considering whether chemicals risk assessment with its traditional focus on chemical-by-chemical evaluations should be expanded to take account of mixture effects. During the last 10 years, research on mixtures has made significant advances, especially in human and mammalian toxicology. This presentation will give a summary of the scientific state of the art of mixture toxicology and will reflect on issues of regulatory relevance for both environmental and human risk assessment.


Risk Assessment of Mixtures-the View from the European Commission. Patrick Murphy. Directorate General for the Environment, European Commission.

The purpose of the presentation is to explain what the European Commission is doing in relation to the risk assessment of chemical mixtures.


Cumulative Risk Assessment: Theory, Practice and Perspective. John C. Lipscomb, PhD, DABT, ATS, U.S. Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment, Cincinnati, Ohio, USA.

Humans are never exposed to a single agent; human exposure patterns are dynamic and complex and they modulate the ensuing response(s) among the population. Cumulative risk assessment (CRA) approaches are employed to assess the risks to a given population from multiple agents emanating from multiple sources. Two key concepts in CRA are the suite of agents and the population of interest. Several methods used for mixtures and cumulative risk assessment will be reviewed.


Mode of action approaches to mixtures. Joop LM Hermens, Institute for Risk Assessment Sciences, Utrecht University, the Netherlands.

Exposure to mixtures in the environment is the reality. Therefore, we have to deal with that in a regulatory framework, although we know that our knowledge is not perfect yet. One of the reasons that mixture toxicity is not implemented in risk assessment is maybe because the topic is complicated. Only 10 individual chemicals will lead to an enormous number of possible combinations in binary, tertiary, etc. mixtures. Another reason may be that we set our ambition too high and want to come up with a complete simple and sound system or evaluation scheme for assessing mixture toxicity. However, there is simply no excuse or scientific valid argument not to include mixture toxicity in our risk assessment process. If we don’t take mixture toxicity into account, we can be sure that risks will be underestimated. However, we have to simplify the problem of mixture toxicity in order to be able to come up with some guidance for the risk assessment process.

Within the fist part of the presentation, I will discuss a theoretical framework that can be applied to make the problem of mixture toxicity a bit simpler. In the second part, I would like to address some issues that may complicate the topic again but at the same time will challenge the scientific research in this field. The focus of the presentation is on effects on the environment.


Mixture toxicity considerations in the ecotoxicological risk assessment for plant protection products. Lennart Weltje1, Mick Hamer2 and Markus Ebeling3
1 BASF SE, Crop Protection – Ecotoxicology, Speyerer-Strasse 2, D 67117 Limburgerhof, Germany
2 Syngenta, Environmental Safety, Jealott's Hill, Bracknell, Berkshire, RG42 6EY, United Kingdom
3 Bayer CropScience AG, BCS AG-D-EnSa-ETX, Alfred-Nobel Strasse 50, D-40789 Monheim, Germany

The majority of formulated plant protection products (PPPs) consists of a mixture of chemicals: one ore more active ingredients (a.i.’s) plus other substances (water, solvents, surfactants, bactericides, adjuvants, UV stabilizers etc.) which maintain and support various functions of the a.i.‘s. Additionally, formulations are sometimes applied simultaneously in the form of liquid tank mixes. There are obvious advantages of combining a.i.’s or formulations: a single application run for the farmer saves fuel, lower amounts for single a.i.’s are required as compared to the solo formulations and the risk of resistance development in target pest species is reduced. Usually a.i.’s with different modes-of-action are combined to achieve a broader pest control spectrum.

Since PPPs have a specific biological activity and are deliberately released in a controlled way into the environment, the conduct of a prospective and detailed environmental risk assessment is required, before authorisation of their use. In this process many data are required on the a.i. and the formulated product, enabling comparisons of their respective toxicities. Further, the behaviour of the a.i. in the various environmental media (e.g. soil, plant, water, sediment, air) is studied in detail to describe the exposure patterns for the relevant non-target species. In fact, when it comes to their environmental behaviour and risks, PPPs are the best characterized and most strictly regulated chemicals. Considering the above, PPPs provide an interesting case to study hazard, exposure and risk assessment aspects of mixture toxicity.

This contribution focusses on the pre-registration process, i.e. the prospective risk assessment, and not on post-registration (e.g. monitoring) data as the latter is not specific to PPPs.


Complex mixtures of chemicals in the aquatic environment and their effects on fish. John P Sumpter, Institute for the Environment, Brunel University, U.K.

All organisms are exposed to highly complex mixtures of chemicals, both natural and man-made. Animals living in environments heavily impacted by man, such as rivers receiving effluent from sewage works, receive continuous exposure to hundreds, if not thousands, of “unnatural” chemicals that would not be present in a pristine environment. It is extremely difficult to determine if this exposure has any adverse effects on aquatic organisms, and if so, which species. If it can be demonstrated that the exposure does adversely affect some aquatic organisms, it can be equally difficult to determine which chemical, or more likely which mixture of chemicals, is responsible. For example, STW effluents can cause estrogenic effects in fish, due to the presence of many different estrogenic chemicals, both natural and man-made, in effluent. The relative contributions of each estrogenic chemical to the overall estrogenic effect is difficult to determine, and probably varies both spatially, and temporally. These, and other, complex philosophical aspects of mixtures toxicity will be discussed, using endocrine disruption in fish as an example.


How does the WFD address cumulative stress (including mixture toxicity) of pollutants to achieve good chemical and ecological status of water bodies? Theo C.M. Brock, ALTERRA, Centre for Water and Climate, Wageningen UR, The Netherlands

It is now more than ten years ago that the Water Framework Directive (WFD) was adopted by the European Parliament. The main objectives of the WFD are (i) to achieve good ecological and chemical status for inland surface waters, transitional waters and coastal waters in EU Member States, (ii) to assess the ecological and chemical status of these water bodies by means of monitoring programmes, and (iii) to implement programmes of measures to reduce environmental stress to an acceptable level. By adopting the WFD a fundamental change in management objective was introduced in the European Union, from merely pollution control to ensuring ecosystem integrity as a whole [1].

The ecological status of WFD water bodies is assessed by monitoring of biological quality elements (e.g. fish, macroinvertebrates, macrophytes, benthic diatoms, phytoplankton), general chemical and physico-chemical quality elements (e.g. pH, alkalinity, nutrients) and hydromorphological quality elements. These quality elements monitored in water bodies are compared with the status of more or less pristine reference ecosystems. If in WFD water bodies the ecological status deviates too much from the reference condition action is needed for achieving the acceptable ecological status.

The chemical status of water bodies is assessed by comparing chemical monitoring data with Environmental Quality Standards (EQS) for priority (hazardous) substances and other relevant substances. Currently, 41 priority (hazardous) substances are listed in the European Union, but a regular update of this list with emerging substances is anticipated. If in water bodies exposure concentrations of one or more of these priority (hazardous) substances are not in compliance with the officially published EQS’s for these pollutants a good chemical status is not reached and action is needed to improve this. In contrast to the EU-level priority (hazardous) substances the other relevant substances are river basin or Member State specific. These other relevant substances have been selected because they are believed to potentially impair the ecological status of specific WFD water bodies and/or related human health aspects. The methodology to derive the EQS’s for other relevant substances is similar to that of the priority (hazardous) substances. This methodology is described in the new Technical Guidance Document for deriving Environmental Quality Standards (will be officially released in 2011). In European river basins the priority (hazardous) substances and river specific pollutants have to be measured on a regular basis.

Under the umbrella of the WFD, EQS derivation is primarily based on a single substance toxicity assessment approach. In exceptional cases EQS’s for mixtures may be derived when their qualitative and quantitative composition is well-defined and/or well described (e.g. biocide preparations, PCB’s, dioxins). The concentration addition (CA) concept is used as a default when setting EQS’s for mixtures. Although compliance with good chemical status is primarily based on EQS’s for individual substances, cumulative stress (including mixtures) of toxicants may be identified as a main pressure affecting ecological status. In that case the cumulative risks caused by pollutants have to be reduced.


Eco-epidemiology as a tool for unravelling causation in the field. Scott D. Dyer, The Procter & Gamble Company, Miami Valley Innovation Center, 11810 East Miami River Road, Cincinnati, Ohio 45015 USA

It is arguable, but Ohio Environmental Protection Agency (USA) may possess the longest running and largest regional biomonitoring assessment of fish and invertebrate communities to make decisions regarding water quality management, perhaps the world over, certainly within the USA. Given the frequency of sampling and geographic spread of data collection, it has created a most unusual dataset to explore the relationship of predicted and measured chemical concentrations and risks with biomonitored data. In essence, the Ohio data provide an opportunity to determine whether current chemical risk assessment approaches are sufficiently conservative so as to protect instream biology, even when those occur as mixtures in realistic multi-stressed conditions. A key aim of eco-epidemiology is to describe, quantify and understand the relationship of chemical mixtures relative to other factors involved in biological community impairment, and Ohio data are an ideal opportunity to develop this field.


Effect-Directed Analysis to Identify Chemical Mixtures in Stressed Aquatic Ecosystems. Werner Brack, Helmholtz-Centre for Environmental Research UFZ, Leipzig, Germany.

Many aquatic ecosystems are contaminated with complex mixtures of chemicals. The EU Water Framework Directive addresses this problem by monitoring a list of 33 (+8) priority pollutants together with other river basin specific pollutants comparing measured concentrations with environmental quality standards. 16 additional compounds are under discussion. Typical numbers of compounds detected in sediment and water extracts with GC/MS or LC/MS screening methods are in the range of at least 10,000. Thus, it is not astonishing that at specific sites of interest (e.g. where a deterioration of the local ecosystem has been observed) effects often cannot be explained by measured compounds. On the other hand, a full chemical analysis of the complex mixture is neither possible nor helpful since for most compounds no or insufficient effect data are available. Thus, approaches such as effect-directed analysis (EDA) [1] or toxicity identification evaluation (TIE) try to direct chemical analysis to those compounds that contribute most to the adverse effects of the mixture. The assumption behind these approaches is that although organisms are exposed to very complex mixtures of chemicals only a much smaller subset of chemicals is responsible for most of the effect. This subset often deviates from a priori selected target compounds for monitoring and needs to be determined for a specific site in order to perform a relevant environmental risk assessment of site-specific contamination.


Determining the need for cumulative risk assessments: When is REACH insufficient and by how much? Paul S. Price and Xianglu Han. The Dow Chemical Company, Toxicology & Environmental Research & Consulting.

Human and environmental receptors are exposed to multiple chemicals from multiple sources [1-3]. REACH is designed to look at individual chemicals and does not require the consideration of cumulative exposures when determining human health and environmental effects. The question has been raised whether the determination of toxicity to humans and environmental receptors on a chemical-by-chemical basis could underestimate the total toxicity to individuals.

Despite the recognition of the need to consider cumulative exposures when determining chemical safety [4], there has been little investigation into how much greater the cumulative toxicity would be than the toxicity from individual chemicals. Because of the considerable level of resources required by cumulative assessments, it would be useful to determine when this difference is large and cumulative assessments are needed and when it is sufficiently small that the chemical-by chemical based approaches in REACH are adequate.

In this talk we describe the use of a simple tool, the Maximum Cumulative Ratio (MCR) that provides a quantitative measure of the magnitude of the toxicity that is “missed” by not performing a cumulative risk assessment. The value can be used to determine the importance of considering the cumulative impact for specific groups of chemicals. The tool can be applied whenever there are sufficient data to use the Hazard Index/Hazard Quotient approach for the evaluation of cumulative toxicity on individuals in a population.


Mixtures in the soil environment in the context of the coming soil directive. Claus Svendsen and David Spurgeon, Centre for Ecology and Hydrology, Maclean Building, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB, UK.
Kees van Gestel, Institute of Ecological Science, Department of Animal Ecology, Vrije Universiteit, Amsterdam

Contaminants are released to soil from multiple sources and as a result the soils in many urban and even rural areas are contaminated with low to moderate levels of a range of different chemically similar and dissimilar toxicants. As in waters, modelling approaches that can help to assess risks associated with these chemical mixtures are being developed in the research literature. To date, however, these methods have rarely been operalitionalised and applied in risk assessment studies.