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Neurotoxicity of chemical mixtures assessed with multielectrode array chips
S36
Abstracts / Toxicology Letters 211S (2012) S35–S42
OS1-4 Neurotoxicity of chemical mixtures assessed with multielectrode array chips Bibiana Scelfo 1 , Taina Palosaari 2 , Matteo Politi 2 , Fabiano Reniero 2 , Maurice Whelan 2 , Jose Manuel Zaldìvar Comenges 2 1
European Commission – JRC, Italy, 2 European Commission, JRC – IHCP, Italy Living organisms and humans are exposed to chemical mixtures in the environment, in food and in consumer products. Experimental data demonstrate toxic effects of mixtures even when each component is below its toxic threshold concentration. In addition, toxicity assessment for hazard identification relies mostly on the use of animals. This approach is costly and time-consuming, and demand for the development of alternative in vitro testing methods is increasing. In this context neurotoxicity (NT) assessment represents a major challenge. Neurons cultured on microelectrode arrays (MEAs) are an optimal model for investigating NT in vitro. The MEAs provide a simpler approach and higher throughput than conventional electrophysiology techniques and have been already used to perform functional toxicological screening. Here we studied the effects of binary mixtures on neurons cultured on MEAs. We have considered compounds with similar and different mode-of-action to assess their combined effects. Individual and binary mixture dose-response curves based on spontaneous neuronal activity have been generated and the IC50 was considered as the end-point for neurotoxicity assessment. The two approaches to mixtures study: Concentration Addition and Independent Action have been applied to compare calculated and experimental results. Nuclear Magnetic Resonance spectroscopy has been employed to confirm no chemical reaction or complexation between mixtures components. The results suggest that both Concentration Addition and Independent Action are able to predict the toxicity of the mixture and that the combination of in vitro test methods with in silico approaches has a strong potential as alternative tool for the prediction of mixtures toxicity. doi:10.1016/j.toxlet.2012.03.152
OS1-5 Munition related metals – Combined toxicity of antimony, copper, and lead Per Leffler, Rune Berglind, Jan Sjöström, Jeff Lewis Swedish Defence Research Agency, FOI, Sweden Lead (Pb) has so far been in focus as the main toxic component in fine caliber ammunition. The main reason is the fear of Pb leaching into groundwater and surface water recipients. The importance of alloy elements copper (Cu) and antimony (Sb) have so far been neglected in the technical risk assessment of their human and environmental impact. The present study aimed at estimating the combined toxicity of these elements in the model systems Vibrio fischeri (bioluminescent bacteria test) and Daphnia magna (acute toxicity test in water flea). A multivariate design was created for the toxicity studies using EC10 and EC90 values from initial metal studies, as minimum and maximum exposures doses in the design. EC50-values were 0.2 mg Sb/L (V. fischeri) and 12 mg Sb/L (D. magna 48 h). Main results from multivariate interpretation of data show significant
toxicity of Sb and Cu in both test systems. The combined effect of Sb and Cu indicate a reduced toxicity. A similar reduction in toxicity was indicated for the combination Sb and Pb, however not statistically significant. The higher sensitivity in the bioluminescent test indicates a more direct access of Sb to critical targets in the bacteria. The water flea is more tolerant due to delayed uptake of toxicant, resulting in slower accumulation at target sites of toxicity. The potential antagonistic effect of Cu and Pb on Sb toxicity indicated by the result may challenge the future human and environmental risk assessment of the composition in ammunition. doi:10.1016/j.toxlet.2012.03.153
OS1-6 Comparison of aggregate exposure approaches in the risk assessment of parabens Ilse Gosens 1 , Christiaan Delmaar 1 , Wouter Ter Burg 1 , Jacqueline Biesterbos 2 , Natalie Von Goetz 3 , Martine Bakker 1 , Cees De Heer 1 , Gerlienke Schuur 1 RIVM, Netherlands, 2 Radboud University, Nijmegen Medical Centre, Netherlands, 3 ETH Zurich, Switzerland
1
Aggregate exposure is the total exposure to a chemical that arises from multiple sources and via multiple exposure pathways (oral, dermal and inhalation). For risk assessment, it is important to estimate the total exposure to a chemical to avoid an underestimation of the risk. A risk assessment for four parabens present in personal care products is performed. A detailed assessment of the aggregate exposure is performed by comparing a deterministic worst-case (tier 1) approach and a probabilistic (tier 2) approach. Tier 1 serves as a starting point for an aggregated exposure assessment. In case of concern, tier 2 is suitable to analyze the uncertainty and the drivers of exposure. Based on adverse effects caused by estrogenic activity found in young animals and a ban declared by Denmark on the use of propyl- and butylparaben for children, the assessment is focused on children between 0 and 3 years old. In the tier 1 approach, default exposure parameters of twelve different products are used resulting in a worst-case estimate. This results in no concern for methyl- and ethylparaben. For propyl- and butylparaben, the Margin of Safety is below 100, giving rise to concern. For the tier 2 approach, a small survey provided more detailed information on habits and practices. Distributions of exposure estimates are used as input data rather than single values. For propyland butylparaben, some children in the population might still be exposed to significant levels. Detailed tier 2 analysis showed that baby wipes have a high contribution. doi:10.1016/j.toxlet.2012.03.154
OS1-7 Perinatal exposure to environmental contaminants affects bone properties in rats Lubna Elabbas 1 , Maria Herlin 1 , Mikko Finnilä 2 , Filip Rendel 1 , Wayne Bowers 3 , Juha Tuukkanen 2 , Matti Viluksela 4 , Agneta Åkesson 1 , Helen Håkansson 1 Karolinska Institute, Sweden, 2 University of Oulu, Finland, 3 Health Canada, Canada, 4 Nat. Institute for Health and Welfare, Finland 1
Abstracts / Toxicology Letters 211S (2012) S35–S42
OS1-4 Neurotoxicity of chemical mixtures assessed with multielectrode array chips Bibiana Scelfo 1 , Taina Palosaari 2 , Matteo Politi 2 , Fabiano Reniero 2 , Maurice Whelan 2 , Jose Manuel Zaldìvar Comenges 2 1
European Commission – JRC, Italy, 2 European Commission, JRC – IHCP, Italy Living organisms and humans are exposed to chemical mixtures in the environment, in food and in consumer products. Experimental data demonstrate toxic effects of mixtures even when each component is below its toxic threshold concentration. In addition, toxicity assessment for hazard identification relies mostly on the use of animals. This approach is costly and time-consuming, and demand for the development of alternative in vitro testing methods is increasing. In this context neurotoxicity (NT) assessment represents a major challenge. Neurons cultured on microelectrode arrays (MEAs) are an optimal model for investigating NT in vitro. The MEAs provide a simpler approach and higher throughput than conventional electrophysiology techniques and have been already used to perform functional toxicological screening. Here we studied the effects of binary mixtures on neurons cultured on MEAs. We have considered compounds with similar and different mode-of-action to assess their combined effects. Individual and binary mixture dose-response curves based on spontaneous neuronal activity have been generated and the IC50 was considered as the end-point for neurotoxicity assessment. The two approaches to mixtures study: Concentration Addition and Independent Action have been applied to compare calculated and experimental results. Nuclear Magnetic Resonance spectroscopy has been employed to confirm no chemical reaction or complexation between mixtures components. The results suggest that both Concentration Addition and Independent Action are able to predict the toxicity of the mixture and that the combination of in vitro test methods with in silico approaches has a strong potential as alternative tool for the prediction of mixtures toxicity. doi:10.1016/j.toxlet.2012.03.152
OS1-5 Munition related metals – Combined toxicity of antimony, copper, and lead Per Leffler, Rune Berglind, Jan Sjöström, Jeff Lewis Swedish Defence Research Agency, FOI, Sweden Lead (Pb) has so far been in focus as the main toxic component in fine caliber ammunition. The main reason is the fear of Pb leaching into groundwater and surface water recipients. The importance of alloy elements copper (Cu) and antimony (Sb) have so far been neglected in the technical risk assessment of their human and environmental impact. The present study aimed at estimating the combined toxicity of these elements in the model systems Vibrio fischeri (bioluminescent bacteria test) and Daphnia magna (acute toxicity test in water flea). A multivariate design was created for the toxicity studies using EC10 and EC90 values from initial metal studies, as minimum and maximum exposures doses in the design. EC50-values were 0.2 mg Sb/L (V. fischeri) and 12 mg Sb/L (D. magna 48 h). Main results from multivariate interpretation of data show significant
toxicity of Sb and Cu in both test systems. The combined effect of Sb and Cu indicate a reduced toxicity. A similar reduction in toxicity was indicated for the combination Sb and Pb, however not statistically significant. The higher sensitivity in the bioluminescent test indicates a more direct access of Sb to critical targets in the bacteria. The water flea is more tolerant due to delayed uptake of toxicant, resulting in slower accumulation at target sites of toxicity. The potential antagonistic effect of Cu and Pb on Sb toxicity indicated by the result may challenge the future human and environmental risk assessment of the composition in ammunition. doi:10.1016/j.toxlet.2012.03.153
OS1-6 Comparison of aggregate exposure approaches in the risk assessment of parabens Ilse Gosens 1 , Christiaan Delmaar 1 , Wouter Ter Burg 1 , Jacqueline Biesterbos 2 , Natalie Von Goetz 3 , Martine Bakker 1 , Cees De Heer 1 , Gerlienke Schuur 1 RIVM, Netherlands, 2 Radboud University, Nijmegen Medical Centre, Netherlands, 3 ETH Zurich, Switzerland
1
Aggregate exposure is the total exposure to a chemical that arises from multiple sources and via multiple exposure pathways (oral, dermal and inhalation). For risk assessment, it is important to estimate the total exposure to a chemical to avoid an underestimation of the risk. A risk assessment for four parabens present in personal care products is performed. A detailed assessment of the aggregate exposure is performed by comparing a deterministic worst-case (tier 1) approach and a probabilistic (tier 2) approach. Tier 1 serves as a starting point for an aggregated exposure assessment. In case of concern, tier 2 is suitable to analyze the uncertainty and the drivers of exposure. Based on adverse effects caused by estrogenic activity found in young animals and a ban declared by Denmark on the use of propyl- and butylparaben for children, the assessment is focused on children between 0 and 3 years old. In the tier 1 approach, default exposure parameters of twelve different products are used resulting in a worst-case estimate. This results in no concern for methyl- and ethylparaben. For propyl- and butylparaben, the Margin of Safety is below 100, giving rise to concern. For the tier 2 approach, a small survey provided more detailed information on habits and practices. Distributions of exposure estimates are used as input data rather than single values. For propyland butylparaben, some children in the population might still be exposed to significant levels. Detailed tier 2 analysis showed that baby wipes have a high contribution. doi:10.1016/j.toxlet.2012.03.154
OS1-7 Perinatal exposure to environmental contaminants affects bone properties in rats Lubna Elabbas 1 , Maria Herlin 1 , Mikko Finnilä 2 , Filip Rendel 1 , Wayne Bowers 3 , Juha Tuukkanen 2 , Matti Viluksela 4 , Agneta Åkesson 1 , Helen Håkansson 1 Karolinska Institute, Sweden, 2 University of Oulu, Finland, 3 Health Canada, Canada, 4 Nat. Institute for Health and Welfare, Finland 1