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Comparison of four methods for bioavailability-based risk assessment of mixtures of Cu, Zn, and Ni in freshwater.
Environ Toxicol Chem. 2017 08; 36(8):2123-2138.ET

Abstract

Although chemical risk assessment is still mainly conducted on a substance-by-substance basis, organisms in the environment are typically exposed to mixtures of substances. Risk assessment procedures should therefore be adapted to fit these situations. Four mixture risk assessment methodologies were compared for risk estimations of mixtures of copper (Cu), zinc (Zn), and nickel (Ni). The results showed that use of the log-normal species sensitivity distribution (SSD) instead of the best-fit distribution and sampling species sensitivities independently for each metal instead of using interspecies correlations in metal sensitivity had little impact on risk estimates. Across 4 different monitoring datasets, between 0% and 52% of the target water samples were estimated to be at risk, but only between 0% and 15% of the target water samples were at risk because of the mixture of metals and not any single metal individually. When a natural baseline database was examined, it was estimated that 10% of the target water samples were at risk because of single metals or their mixtures; when the most conservative method was used (concentration addition [CA] applied directly to the SSD, i.e., CASSD). However, the issue of metal mixture risk at geochemical baseline concentrations became relatively small (2% of target water samples) when a theoretically more correct method was used (CA applied to individual dose response curves, i.e., CADRC). Finally, across the 4 monitoring datasets, the following order of conservatism for the 4 methods was shown (from most to least conservative, with ranges of median margin of safety [MoS] relative to CASSD): CASSD > CADRC (MoS = 1.17-1.25) > IADRC (independent action (IA) applied to individual dose-response curves; MoS = 1.38-1.60) > IASSD (MoS = 1.48-1.72). Therefore, it is suggested that these 4 methods can be used in a general tiered scheme for the risk assessment of metal mixtures in a regulatory context. In this scheme, the CASSD method could serve as a first (conservative) tier to identify situations with likely no potential risk at all, regardless of the method used (the sum toxic unit expressed relative to the 5% hazardous concentration [SumTUHC5 ] < 1) and the IASSD method to identify situations of potential risk, also regardless of the method used (the multisubstance potentially affected fraction of species using the IASSD method [msPAFIA,SSD ] > 0.05). The CADRC and IADRC methods could be used for site-specific assessment for situations that fall in between (SumTUHC5 > 1 and msPAFIA,SSD < 0.05). Environ Toxicol Chem 2017;36:2123-2138. © 2017 SETAC.

Authors+Show Affiliations

Faculty of Bioscience Engineering, Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University (UGent), Ghent, Belgium.Faculty of Bioscience Engineering, Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University (UGent), Ghent, Belgium.Faculty of Bioscience Engineering, Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University (UGent), Ghent, Belgium.Centre for Ecology and Hydrology, Bailrigg, Lancaster, United Kingdom.Faculty of Bioscience Engineering, Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University (UGent), Ghent, Belgium.

Pub Type(s)

Comparative Study
Journal Article

Language

eng

PubMed ID

28112432

Citation

Van Regenmortel, Tina, et al. "Comparison of Four Methods for Bioavailability-based Risk Assessment of Mixtures of Cu, Zn, and Ni in Freshwater." Environmental Toxicology and Chemistry, vol. 36, no. 8, 2017, pp. 2123-2138.
Van Regenmortel T, Nys C, Janssen CR, et al. Comparison of four methods for bioavailability-based risk assessment of mixtures of Cu, Zn, and Ni in freshwater. Environ Toxicol Chem. 2017;36(8):2123-2138.
Van Regenmortel, T., Nys, C., Janssen, C. R., Lofts, S., & De Schamphelaere, K. A. C. (2017). Comparison of four methods for bioavailability-based risk assessment of mixtures of Cu, Zn, and Ni in freshwater. Environmental Toxicology and Chemistry, 36(8), 2123-2138. https://doi.org/10.1002/etc.3746
Van Regenmortel T, et al. Comparison of Four Methods for Bioavailability-based Risk Assessment of Mixtures of Cu, Zn, and Ni in Freshwater. Environ Toxicol Chem. 2017;36(8):2123-2138. PubMed PMID: 28112432.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Comparison of four methods for bioavailability-based risk assessment of mixtures of Cu, Zn, and Ni in freshwater. AU - Van Regenmortel,Tina, AU - Nys,Charlotte, AU - Janssen,Colin R, AU - Lofts,Stephen, AU - De Schamphelaere,Karel A C, Y1 - 2017/02/23/ PY - 2016/09/19/received PY - 2017/11/04/revised PY - 2017/01/20/accepted PY - 2017/1/24/pubmed PY - 2017/11/4/medline PY - 2017/1/24/entrez KW - Concentration addition KW - Independent action KW - Mixture toxicity KW - Risk assessment SP - 2123 EP - 2138 JF - Environmental toxicology and chemistry JO - Environ Toxicol Chem VL - 36 IS - 8 N2 - Although chemical risk assessment is still mainly conducted on a substance-by-substance basis, organisms in the environment are typically exposed to mixtures of substances. Risk assessment procedures should therefore be adapted to fit these situations. Four mixture risk assessment methodologies were compared for risk estimations of mixtures of copper (Cu), zinc (Zn), and nickel (Ni). The results showed that use of the log-normal species sensitivity distribution (SSD) instead of the best-fit distribution and sampling species sensitivities independently for each metal instead of using interspecies correlations in metal sensitivity had little impact on risk estimates. Across 4 different monitoring datasets, between 0% and 52% of the target water samples were estimated to be at risk, but only between 0% and 15% of the target water samples were at risk because of the mixture of metals and not any single metal individually. When a natural baseline database was examined, it was estimated that 10% of the target water samples were at risk because of single metals or their mixtures; when the most conservative method was used (concentration addition [CA] applied directly to the SSD, i.e., CASSD). However, the issue of metal mixture risk at geochemical baseline concentrations became relatively small (2% of target water samples) when a theoretically more correct method was used (CA applied to individual dose response curves, i.e., CADRC). Finally, across the 4 monitoring datasets, the following order of conservatism for the 4 methods was shown (from most to least conservative, with ranges of median margin of safety [MoS] relative to CASSD): CASSD > CADRC (MoS = 1.17-1.25) > IADRC (independent action (IA) applied to individual dose-response curves; MoS = 1.38-1.60) > IASSD (MoS = 1.48-1.72). Therefore, it is suggested that these 4 methods can be used in a general tiered scheme for the risk assessment of metal mixtures in a regulatory context. In this scheme, the CASSD method could serve as a first (conservative) tier to identify situations with likely no potential risk at all, regardless of the method used (the sum toxic unit expressed relative to the 5% hazardous concentration [SumTUHC5 ] < 1) and the IASSD method to identify situations of potential risk, also regardless of the method used (the multisubstance potentially affected fraction of species using the IASSD method [msPAFIA,SSD ] > 0.05). The CADRC and IADRC methods could be used for site-specific assessment for situations that fall in between (SumTUHC5 > 1 and msPAFIA,SSD < 0.05). Environ Toxicol Chem 2017;36:2123-2138. © 2017 SETAC. SN - 1552-8618 UR - https://www.unboundmedicine.com/medline/citation/28112432/Comparison_of_four_methods_for_bioavailability_based_risk_assessment_of_mixtures_of_Cu_Zn_and_Ni_in_freshwater_ DB - PRIME DP - Unbound Medicine ER -