Using emerging science to inform risk characterizations for wildlife within current regulatory frameworks.

Many jurisdictions have regulatory frameworks that seek to reduce the effects of environmental exposures of anthropogenic chemicals on terrestrial wildlife (i.e., mammals, birds, reptiles, and amphibians). The frameworks apply for new and existing chemicals, including pesticides (prospective assessments), and to environmental contamination from releases (retrospective risk assessments). Relatively recently, there have been many scientific advances that could improve risk estimates for wildlife. Here, we briefly describe current regulations from North America (United States and Canada) and from Europe that include risk assessments for wildlife to ascertain whether they are conducive to the use of emerging science and new methods. We also provide examples where new and emerging science may be used to improve wildlife risk characterization and identify areas in need of future research. Integr Environ Assess Manag 2024;20:765-779. © 2024 His Majesty the King in Right of Canada and The Authors. Integrated Environmental Assessment and Management © 2024 Society of Environmental Toxicology & Chemistry (SETAC). Reproduced with the permission of the Minister of Environment and Climate Change Canada. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Persistence, bioaccumulation and toxicity-assessment of petroleum UVCBs: A case study on alkylated three-ring PAHs.

Substances with (very) persistent, (very) bioaccumulative, and/or toxic properties (PBT/vPvB) are of environmental concern and are identified via hazard-based PBT-assessment approaches. The PBT-assessment of well-defined substances is optimized over the past decades, but is under development for substances of unknown or variable composition, complex reaction products or biological materials (UVCBs). Particularly, the large number of constituents and variable composition complicate the PBT-assessment of UVCBs. For petroleum UVCBs, the use of the hydrocarbon block method (HBM) is proposed. Within this method, groups of constituents with similar physicochemical properties and structure are treated as a single entity and are expected to have comparable environmental fate and hazard properties. So far, however, there is a lack of experience with the application of the HBM for PBT-assessment purposes. The aim of this study is to investigate the suitability of the HBM for the PBT-assessment of petroleum UVCBs by evaluating the group of alkylated three-ring polycyclic aromatic hydrocarbons (PAHs). The presented approach is based on experimental data and model predictions and followed the guidelines of the European Chemicals Agency. Because of a lack of relevant experimental data, relative trend analyses were applied. The results indicate that alkylated three-ring PAHs are more persistent, bioaccumulative, and toxic than the parent three-ring PAHs. As the parent three-ring PAHs are currently identified within Europe as PBT/vPvB substances, the alkylated three-ring PAHs could also be considered as PBT/vPvB. Accordingly, this case study provides the prospects for the application of the HBM for the PBT-assessment of UVCBs using trend analysis.

Variability in fish bioconcentration factors: Influences of study design and consequences for regulation.

The fish bioconcentration factor (BCF) is an important aspect within bioaccumulation assessments. Several factors have been suggested to influence BCF values - including species, developmental stage, mixture exposure, and calculation method. However, their exact contribution to variance in BCF values is unknown. Within this study we assessed the relative impact of these test characteristics on BCF values and analyzed the reproducibility of aquatic exposure bioconcentration tests. Linear mixed effects analyses were performed on a newly develop database to investigate the relationship between the response variable (i.e. lipid normalized log BCF values) and several test characteristics as fixed effects. Lower BCF values were observed for substances that were simultaneously applied with high molecular weight polycyclic aromatic hydrocarbons compared to single substance exposure (with an average difference of -0.81 log BCF). Also, lower BCFs upon kinetic determination were observed compared to steady-state BCFs (log BCF -0.27), and lower BCFs for species from the Ostariophysi subcohort level (log BCF -0.17 to -0.15). In addition, data analysis showed high variation within BCF values for single substances (average SD = log BCF 0.21), which questions the robustness of the current bioaccumulation assessments. For example, the 95% confidence range of a BCF value of 2500 ranges from 953 ('not-bioaccumulative') to 6561 ('very bioaccumulative'). Our results show that the use of one single BCF leads to a high uncertainty in bioaccumulation assessments. We strongly recommend that within future bioconcentration studies, the used experimental design and test conditions are described in detail and justified to support solid interpretation.

Review of existing terrestrial bioaccumulation models and terrestrial bioaccumulation modeling needs for organic chemicals.

Protocols for terrestrial bioaccumulation assessments are far less-developed than for aquatic systems. This article reviews modeling approaches that can be used to assess the terrestrial bioaccumulation potential of commercial organic chemicals. Models exist for plant, invertebrate, mammal, and avian species and for entire terrestrial food webs, including some that consider spatial factors. Limitations and gaps in terrestrial bioaccumulation modeling include the lack of QSARs for biotransformation and dietary assimilation efficiencies for terrestrial species; the lack of models and QSARs for important terrestrial species such as insects, amphibians and reptiles; the lack of standardized testing protocols for plants with limited development of plant models; and the limited chemical domain of existing bioaccumulation models and QSARs (e.g., primarily applicable to nonionic organic chemicals). There is an urgent need for high-quality field data sets for validating models and assessing their performance. There is a need to improve coordination among laboratory, field, and modeling efforts on bioaccumulative substances in order to improve the state of the science for challenging substances.

An evaluation of bioaccumulation data for hexachlorobenzene to derive water quality standards according to the EU-WFD methodology.

Hexachlorobenzene (HCB) is a priority hazardous substance within the Water Framework Directive (WFD). For aquatic systems, the European Commission has derived quality standards (QS) for HCB in biota. However, in some countries a preference may exist for QS based on water concentrations. The conversion of biota QS into water QS can be done by dividing the quality standard for biota by a reliable bioaccumulation factor (BAF) or by the product of the bioconcentration factor (BCF) and the biomagnification factor (BMF) (BCF × BMF). An extensive literature review of HCB bioaccumulation was performed, and data on bioaccumulation, biomagnification and bioconcentration, both from the field and the laboratory, were assessed for their usefulness to recalculate biota standards into water standards. The evaluation resulted in 10 reliable values for field BAFs, with a geometric mean of 221 000 L/kg (5% lipid-normalized). Bioaccumulation factor measurements show a high variation of more than 1 order of magnitude. At lower trophic levels (algae, small zooplankton), accumulation of HCB already exceeds expected accumulation through equilibrium partitioning by far. This affects BAFs at higher trophic levels as well. Moreover, observed BAF values for HCB in fish cannot be easily explained from the age of the fish, but there is a significant increase with trophic level. Reliable values for laboratory BCFs for fish were retrieved from literature, partly with water-based exposure and partly with dietary exposure. The 5% lipid-normalized BCF of all these data is 12 800 L/kg. Regarding biomagnification, a number of reliable BMF and trophic magnification factor values, mostly determined in the field, were retrieved. From these data, an overall BMF of 3 per trophic level can be deduced. When comparing BCF values for fish multiplied by the BMF (12 800 × 3 = 38 400 L/kg) to the observed BAF values for fish (geometric mean 238 000 L/kg), there appears to be a large gap. Thus, the uncertainties surrounding values for bioaccumulation of HCB are high. Although the confidence in laboratory BCFs is higher, these data seem to be not relevant for small fish in the field. This makes it difficult to obtain a reliable BAF or BCF × BMF value to recalculate biota standards into water standards. On the other hand, biota concentrations in the field show a high variability that also hampers comparison with a fixed limit such as a quality standard. Thus, compliance checking using biota in the field means that a relatively large amount of fish will have to be used to obtain a reliable estimate. The following "tiered approach" is suggested: 1) calculate a water quality standard, using the BAF value that is most relevant for the trophic level to be protected, and 2) if this standard is exceeded in the field, sample representative biota in the field and compare concentrations of HCB in biota and water with their respective standards in a weight of evidence approach for compliance checking. In this way, unnecessary biota sampling can be avoided for reasons of efficiency and animal welfare.

Ecotoxicological environmental risk limits for total petroleum hydrocarbons on the basis of internal lipid concentrations.

A method is described for deriving ecotoxicological environmental risk limits (ERLs) for total petroleum hydrocarbons (TPH). Toxicity data for two oil types (light and heavy) to benthic organisms and corresponding estimated internal lipid concentrations, calculated by equilibrium partitioning, are used as a measure of toxicity by narcosis. It is assumed that uptake by organisms takes place from the aqueous phase, and for partitioning, both oil droplets or coating and organic carbon of sediment are taken into account. To distinguish between the different fractions of TPH, the method used is based on a fraction analysis approach in which aliphatic and aromatic compounds are regarded separately and both are further divided into different fractions. A toxic unit approach is applied to these fractions to take additivity into account. Lethality of the lighter oil type (internal concentration 28-204 mmol/Llipid) was in good agreement with data on internal concentrations retrieved from the literature. For the heavier oil type the observed toxicity was slightly higher and can probably be attributed to physical soiling of the organisms by oil or oxygen depletion due to biodegradation of the oil. For deriving ERLs, chronic endpoints are considered. The most sensitive chronic endpoints appear to be similar for both types of oil. The distribution of estimated total internal concentrations for chronic endpoints (1.38-149 mmol/Llipid) is used as a basis for the ERLs. The resulting ERLs for the mixture of TPH are comparable with ERLs for single compounds.

The evaluation of the equilibrium partitioning method using sensitivity distributions of species in water and soil.

The equilibrium partitioning method (EqP-method) can be used to calculate soil quality standards (expressed in mg/kg) from aquatic quality standards (expressed in microg/l) using a partitioning coefficient. The validity of this application of the EqP-method was studied comparing aquatic with terrestrial toxicity data. The data set collected for deriving environmental quality standards in the Netherlands, was used for this study. For 10 organic substances (chlorpyrifos, atrazine, carbofuran, pentachlorophenol, chlordane, aldrin, trichlorobenzene, heptachlor, trichlorophenol and trichloroethene) and for 8 metals, sufficient data were available. The aquatic toxicity data were multiplied by the partitioning coefficient in order to obtain aquatic data expressed in mg/kg. For some compounds the terrestrial toxicity data were significantly higher than the aquatic data but for other compounds it was the other way around. These differences indicate that the EqP-method can give significant over-or underestimations, due to inaccurate partitioning coefficients or differences in species sensitivities. These over- or underestimations can have an impact on the setting of environmental quality standards which are based on the hazardous concentration 5% (HC5) values. The uncertainty in the calculation of HC5 values attributed to the use of the EqP-method, was quantified. The HC5 values derived using the EqP-method were in 5% of the cases more than 20 times higher than the corresponding HC5 values that were derived directly from soil toxicity tests. Despite of this uncertainty the use of the EqP-method can still be advocated for setting soil quality guidelines when only a very limited number of terrestrial toxicity data are available.