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Influence of study parameters on TTC
Abstracts / Toxicology Letters 180S (2008) S32–S246
R03 Interindividual variability of cytochrome P450 (CYP)-dependent alkoxyresorufin-dealkylase activities in human lung and relevance for the risk assessment of chemicals Ulrike Bernauer 1,∗ , Barbara Heinrich-Hirsch 1 , Mario Toennies 2 , Ursula Gundert-Remy 1 1
Federal Institute for Risk Assessment, Berlin, Germany, Klinikum Emil von Behring, Berlin, Germany
2
Helios
Background: The lung represents an important target for the toxic effects of chemicals. Target tissue toxicity can be explained by local metabolic activation. As demonstrated by mRNA and Western Blot analysis, xenobiotic metabolizing CYPs are expressed in human lung. Their variation within the human population is not known, although this is important for the risk assessment of chemicals. From interindividual variability, pathway-specific assessment factors (AFs) can be derived. This is of special importance in the lung, where metabolism is capacity-limited due to low abundance of CYPs. We determined the variability of CYP450-related ethoxyresorufin-O-deethylase- (EROD-), methoxyresorufin-O-demethylase- (MROD) and pentoxyresorufinO-depentylase- (PROD) activities in a large panel of human lung samples. The activities are related to CYP1A1/1B1 (EROD), CYP1A2 (MROD) and CYP2B enzymes (PROD). Methods: Human lung tissue was obtained after informed consent. Microsomes were prepared and total protein content was determined. Enzyme activities were determined using fluorometric methods for dealkylation of alkoxyresorufins modified for human lung tissue. Assessment factors were derived by the ratio of the 95% percentile (P95)/median. Results: EROD-, MROD-, and PROD activities were determined in 110 samples. The following P95/median ratios were obtained: 2.7 (EROD), 2.9 (MROD) and 3.2 (PROD). For an improved risk assessment, enzymes involved in chemical metabolism should be identified. Determination of enzyme variation allows replacing the default AF of 3.16 for the kinetic part of intraspecies variability by a pathway-specific AF. Our results demonstrate that the pathwayspecific AF for the enzyme activities investigated in the lung is almost equal to the default AF of 3.16. doi:10.1016/j.toxlet.2008.06.542 R04 Risk assessment of coccidiostats after cross-contamination of feed: Implications for animal and human health Ulla Bertelsen 1,∗ , Jean-Lou C.M. Dorne 1 , María Luisa FernándezCruz 2 , Derek W. Renshaw 3 , Kimmo Peltonen 4 , Arturo Anadón 5 , Alexander Feil 6 , Pascal Sanders 7 , Pieter W. Wester 8 , Johanna Fink-Gremmels 9 1
EFSA, Parma, Italy, 2 Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Madrid, Spain, 3 Food Standards Agency, London, United Kingdom, 4 Finnish Food Safety Authority EVIRA, Helsinki, Finland 5 Universidad Complutense de Madrid, Facultad de Veterinaria, Madrid, Spain 6 Forschungsinstitut Futtermitteltechnik, Braunschweig, Germany 7 AFSSA - LERMVD, Fougères, France 8 RIVM, Food and Consumer Safety, Bilthoven, Netherlands 9 Utrecht University, Veterinary Medicine, Utrecht, Netherlands Eleven coccidiostats are authorised in the EU as feed additives in one or more species (chicken, turkey, rabbits). These coccidiostats are classified as ionophoric (lasalocid, monensin, maduramicin, narasin, salinomycin, semduramicin) or non-ionophoric
S61
(decoquinate, diclazuril, halofuginone, nicarbazin, robenidine). Cross-contamination of feed during production can result in exposure of non-target animals and thereby of consumers. Risk assessments for non-target animals and humans have been performed by the Panel on Contaminants in the Food Chain (CONTAM) of the European Food Safety Authority (EFSA), based on cross-contaminated feed containing 2%, 5% and 10%, respectively, of the maximum level authorised for target species. The risk to non-target species from cross-contaminated feed was found to be negligible with the exception of salinomycin and monensin in horses, for which adverse effects are likely to occur when crosscontamination exceeds the levels of 2% and 5%, respectively. Residue concentrations in animal products were calculated using occurrence and kinetic data. Human exposure was estimated for high consumers using standard food basket consumption figures for eggs, meat, and edible offal, and the exposure was compared to the acceptable daily intake (ADI). Considering 10% cross-contamination, residue levels from 9 coccidiostats corresponded to between 0.8% and 17% of the respective ADIs, whereas lasalocid and halofuginone exposures were slightly above the ADIs. However, a daily consumption of residue-containing edible tissues and eggs at the estimated (worst case) concentrations is very unlikely to occur in real life, and therefore it was concluded that cross-contamination of feed is unlikely to adversely effect consumers’ health. doi:10.1016/j.toxlet.2008.06.543 R05 Influence of study parameters on TTC Sylvia Escher, Annette Bitsch ∗ , Monika Batke, Christine Melber, Nelly Simetska, Inge Mangelsdorf Fraunhofer Institut für Toxikologie und Experimentelle Medizin, Hannover, Germany The Threshold of Toxicological Concern (TTC) concept established by Munro et al. provides generic exposure thresholds for groups of chemicals. Below the TTC no appreciable risk to human health is assumed. Thresholds for oral toxicity were defined by grouping food ingredients into three structural classes according to the Cramerdecision-tree. In order to apply the Cramer classification to industrial chemicals and to study the influence of study duration, species and route on TTC, a comparison of the Munro database with RepDose (database on repeated dose toxicity) was performed. Both databases contain a similar number of chemicals, 95 are identical. NOELs/LOELs in both databases show a wide distribution in each Cramer-class. Median/mean analyses reveal that NOELs/LOELs in RepDose are lower than in Munro, also for the shared 95 substances. Means/medians decrease significantly from Cramer-class 1 to 3 in both databases the difference being higher in Munro than in RepDose. A comparison of subchronic, chronic and lifespan studies reveals a significant decrease of mean/median LOELs with study duration. Class 1 and 3 differ significantly for lifespan/subchronic studies in Munro and for all categories in RepDose. As seen before, the difference of Classes 1 and 3 does not exceed a factor of 5 in RepDose. The analysis of species gave similar results. Besides oral application, RepDose also contains inhalation studies. A preliminary analysis of LOELs/NOELs indicates, that inhalation studies will provide lower thresholds than oral application. doi:10.1016/j.toxlet.2008.06.544
R03 Interindividual variability of cytochrome P450 (CYP)-dependent alkoxyresorufin-dealkylase activities in human lung and relevance for the risk assessment of chemicals Ulrike Bernauer 1,∗ , Barbara Heinrich-Hirsch 1 , Mario Toennies 2 , Ursula Gundert-Remy 1 1
Federal Institute for Risk Assessment, Berlin, Germany, Klinikum Emil von Behring, Berlin, Germany
2
Helios
Background: The lung represents an important target for the toxic effects of chemicals. Target tissue toxicity can be explained by local metabolic activation. As demonstrated by mRNA and Western Blot analysis, xenobiotic metabolizing CYPs are expressed in human lung. Their variation within the human population is not known, although this is important for the risk assessment of chemicals. From interindividual variability, pathway-specific assessment factors (AFs) can be derived. This is of special importance in the lung, where metabolism is capacity-limited due to low abundance of CYPs. We determined the variability of CYP450-related ethoxyresorufin-O-deethylase- (EROD-), methoxyresorufin-O-demethylase- (MROD) and pentoxyresorufinO-depentylase- (PROD) activities in a large panel of human lung samples. The activities are related to CYP1A1/1B1 (EROD), CYP1A2 (MROD) and CYP2B enzymes (PROD). Methods: Human lung tissue was obtained after informed consent. Microsomes were prepared and total protein content was determined. Enzyme activities were determined using fluorometric methods for dealkylation of alkoxyresorufins modified for human lung tissue. Assessment factors were derived by the ratio of the 95% percentile (P95)/median. Results: EROD-, MROD-, and PROD activities were determined in 110 samples. The following P95/median ratios were obtained: 2.7 (EROD), 2.9 (MROD) and 3.2 (PROD). For an improved risk assessment, enzymes involved in chemical metabolism should be identified. Determination of enzyme variation allows replacing the default AF of 3.16 for the kinetic part of intraspecies variability by a pathway-specific AF. Our results demonstrate that the pathwayspecific AF for the enzyme activities investigated in the lung is almost equal to the default AF of 3.16. doi:10.1016/j.toxlet.2008.06.542 R04 Risk assessment of coccidiostats after cross-contamination of feed: Implications for animal and human health Ulla Bertelsen 1,∗ , Jean-Lou C.M. Dorne 1 , María Luisa FernándezCruz 2 , Derek W. Renshaw 3 , Kimmo Peltonen 4 , Arturo Anadón 5 , Alexander Feil 6 , Pascal Sanders 7 , Pieter W. Wester 8 , Johanna Fink-Gremmels 9 1
EFSA, Parma, Italy, 2 Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Madrid, Spain, 3 Food Standards Agency, London, United Kingdom, 4 Finnish Food Safety Authority EVIRA, Helsinki, Finland 5 Universidad Complutense de Madrid, Facultad de Veterinaria, Madrid, Spain 6 Forschungsinstitut Futtermitteltechnik, Braunschweig, Germany 7 AFSSA - LERMVD, Fougères, France 8 RIVM, Food and Consumer Safety, Bilthoven, Netherlands 9 Utrecht University, Veterinary Medicine, Utrecht, Netherlands Eleven coccidiostats are authorised in the EU as feed additives in one or more species (chicken, turkey, rabbits). These coccidiostats are classified as ionophoric (lasalocid, monensin, maduramicin, narasin, salinomycin, semduramicin) or non-ionophoric
S61
(decoquinate, diclazuril, halofuginone, nicarbazin, robenidine). Cross-contamination of feed during production can result in exposure of non-target animals and thereby of consumers. Risk assessments for non-target animals and humans have been performed by the Panel on Contaminants in the Food Chain (CONTAM) of the European Food Safety Authority (EFSA), based on cross-contaminated feed containing 2%, 5% and 10%, respectively, of the maximum level authorised for target species. The risk to non-target species from cross-contaminated feed was found to be negligible with the exception of salinomycin and monensin in horses, for which adverse effects are likely to occur when crosscontamination exceeds the levels of 2% and 5%, respectively. Residue concentrations in animal products were calculated using occurrence and kinetic data. Human exposure was estimated for high consumers using standard food basket consumption figures for eggs, meat, and edible offal, and the exposure was compared to the acceptable daily intake (ADI). Considering 10% cross-contamination, residue levels from 9 coccidiostats corresponded to between 0.8% and 17% of the respective ADIs, whereas lasalocid and halofuginone exposures were slightly above the ADIs. However, a daily consumption of residue-containing edible tissues and eggs at the estimated (worst case) concentrations is very unlikely to occur in real life, and therefore it was concluded that cross-contamination of feed is unlikely to adversely effect consumers’ health. doi:10.1016/j.toxlet.2008.06.543 R05 Influence of study parameters on TTC Sylvia Escher, Annette Bitsch ∗ , Monika Batke, Christine Melber, Nelly Simetska, Inge Mangelsdorf Fraunhofer Institut für Toxikologie und Experimentelle Medizin, Hannover, Germany The Threshold of Toxicological Concern (TTC) concept established by Munro et al. provides generic exposure thresholds for groups of chemicals. Below the TTC no appreciable risk to human health is assumed. Thresholds for oral toxicity were defined by grouping food ingredients into three structural classes according to the Cramerdecision-tree. In order to apply the Cramer classification to industrial chemicals and to study the influence of study duration, species and route on TTC, a comparison of the Munro database with RepDose (database on repeated dose toxicity) was performed. Both databases contain a similar number of chemicals, 95 are identical. NOELs/LOELs in both databases show a wide distribution in each Cramer-class. Median/mean analyses reveal that NOELs/LOELs in RepDose are lower than in Munro, also for the shared 95 substances. Means/medians decrease significantly from Cramer-class 1 to 3 in both databases the difference being higher in Munro than in RepDose. A comparison of subchronic, chronic and lifespan studies reveals a significant decrease of mean/median LOELs with study duration. Class 1 and 3 differ significantly for lifespan/subchronic studies in Munro and for all categories in RepDose. As seen before, the difference of Classes 1 and 3 does not exceed a factor of 5 in RepDose. The analysis of species gave similar results. Besides oral application, RepDose also contains inhalation studies. A preliminary analysis of LOELs/NOELs indicates, that inhalation studies will provide lower thresholds than oral application. doi:10.1016/j.toxlet.2008.06.544