A. Di Guardo

Theoretically exploring direct and indirect chemical effects across ecological and exposure scenarios using mechanistic fate and effects modelling

Predicting ecosystem response to chemicals is a complex problem in ecotoxicology and a challenge for risk assessors. The variables potentially influencing chemical fate and exposure define the exposure scenario while the variables determining effects at the ecosystem level define the ecological scenario. In absence of any empirical data, the objective of this paper is to present simulations by a fugacity-based fate model and a differential equation-based ecosystem model to theoretically explore how direct and indirect effects on invertebrate shallow pond communities vary with changing ecological and exposure scenarios. These simulations suggest that direct and indirect effects are larger in mesotrophic systems than in oligotrophic systems. In both trophic states, interaction strength (quantified using grazing rates) was suggested a more important driver for the size and recovery from direct and indirect effects than immigration rate. In general, weak interactions led to smaller direct and indirect effects. For chemicals targeting mesozooplankton only, indirect effects were common in (simple) food-chains but rare in (complex) food-webs. For chemicals directly affecting microzooplankton, the dominant zooplankton group in the modelled community, indirect effects occurred both in food-chains and food-webs. We conclude that the choice of the ecological and exposure scenarios in ecotoxicological modelling efforts needs to be justified because of its influence on the prevalence and magnitude of the predicted effects. Overall, more work needs to be done to empirically test the theoretical expectations formulated here.

Pharmaceuticals as Environmental Contaminants: Modelling Distribution and Fate

Concern is growing over the environmental consequences of the use of drugs for human and animal health. Long term treatments for several illnesses are a common mass practice in human health care (e.g. diuretics, beta blockers, antibiotics), a number of females are taking daily hormones to prevent unwanted pregnancies, modern life stress is handled very frequently through sedatives and tranquillizers, moreover there is in animal farming a general trend towards the intensification of production methods and production gains based on greater reliance on pharmaceuticals, feed additives, hormones and potent parasiticides (Halling-Sorensen et al. 1998).

Classification of environmental pollutants for global mobility potential

The environmental behaviour of global organic contaminants is known to be controlled by the physico-chemical properties of the compounds themselves. The principal component analysis of some physico-chemical properties, particularly relevant in determining mobility potential (vapour pressure, Henrys law constant, water solubility, K OW , K OA and melting point) allows a multivariate approach to a ranking of organic pollutants according to their intrinsic tendency towards mobility, and the definition of four a priori mobility classes for screening purposes. Quantitative structure-property relationships (QSPRs) were used to predict missing values for octanol/air partition coefficients. Finally, a classification method employing theoretical molecular descriptors was used to assign studied chemicals to four mobility classes. The proposed approach assesses, directly and simply, a pollutants inherent tendency towards mobility using only knowledge of the pollutants molecular structure; the approach is particularly useful for a preliminary screening and the prioritisation of organic pollutants of emerging environmental concern.

The ChimERA project: Coupling mechanistic exposure and effect models into an integrated platform for ecological risk assessment

Current techniques for the ecological risk assessment of chemical substances are often criticised for their lack of environmental realism, ecological relevance and methodological accuracy. ChimERA is a 3-year project (2013–2016), funded by Cefic’s Long Range Initiative (LRI) that aims to address some of these concerns by developing and testing mechanistic fate and effect models, and coupling of these models into one integrated platform for risk assessment. This paper discusses the backdrop against which this project was initiated and lists its objectives and planned methodology.

Environmental Exposure Assessment

Environmental exposure is usually assessed by evaluating the concentration of a specific chemical in the main environmental media (air, soil, water, sediment) and in biota as food source for other organisms (predators) by secondary poisoning. The study of exposure is complicated by the complexity of the many ecosystems to protect and the high number of chemicals that can be found in the environment. Exposure in the environment can be evaluated using monitoring data or predictive approaches, such as environmental fate models. When more details on organism uptake and levels are needed, specific bioaccumulation models can be used.