Evaluation of critical body residue data for acute narcosis in aquatic organisms

Abstract

The Environmental Residue Effects Database was evaluated to identify critical body residues of organic chemicals causing acute baseline neutral narcosis in aquatic organisms. Over 15 000 records for >400 chemicals were evaluated. Mean molar critical body residues in the final data set of 161 records for 29 chemicals were within published ranges but varied within and among chemicals and species (~3 orders of magnitude), and lipid normalization did not consistently decrease variability. All 29 chemicals can act as baseline neutral narcotics, but chemicals and/or their metabolites may also act by nonnarcotic modes of action. Specifically, nonnarcotic toxicity of polycyclic aromatic hydrocarbons and/or their biotransformation derivatives may be a significant source of variability. Complete testing of the narcosis-critical body residue hypothesis was confounded by data gaps for key toxicity modifying factors such as metabolite formation/toxicity, lipid content/composition, other modes of toxic action, and lack of steady-state status. Such problems impede determination of the precise, accurate toxicity estimates necessary for sound toxicological comparisons. Thus, neither the data nor the chemicals in the final data set should be considered definitive. Changes to testing designs and methods are necessary to improve data collection and critical body residue interpretation for hazard and risk assessment. Each of the toxicity metrics discussed-wet weight and lipid weight critical body residues, volume fraction in organism lipid, and chemical activity-has advantages, but all are subject to the same toxicity modifying factors.

Bioconcentration and Aquatic Toxicity of Superhydrophobic Chemicals: A Modeling Case Study of Cyclic Volatile Methyl Siloxanes

“…This value corresponds to 60 mmol kg −1 lw and is in the range of CBRs for acute baseline neutral narcosis in small aquatic organisms, assuming ∼5% lipid content. 26,42 This value is broadly consistent with the Redman et al 4 analysis employing the Target Lipid Model. In the latter study, CBRs for the example cVMS substances were estimated for daphnia (D. magna) of 115 mmol kg −1 lw and for C. tentans of 28 mmol kg −1 lw.…”

A high throughput passive dosing format for the Fish Embryo Acute Toxicity test

“…The lipid content of 120 hpf unexposed zebrafish was 1.63% ± 0.29% (SD) (w/w, fresh wt), and our CBR LIP50 of 167 mmol/kg lipids was very close to the expected range of 40-160 mmol/kg (Van Wezel and Opperhuizen, 1995), but was higher than the mean CBR LIP50 of 53.9 mmol/kg lipid reported for 29 narcotics in algae, invertebrates and fish (McCarty et al, 2013). Our observation that the CBR fits nicely into the expected interval while the lipid normalized CBR is rather high relative to what is expected, may be due to the fact that lipid corrected CBR values are subject to variation in both lipid content and composition, which may compromise their accuracy (McCarty et al, 2013). For sublethal effects we report EBR LIP50 (swim bladder): 16 mmol/kg lipids and EBR LIP50 (sublethal effects): 13 mmol/kg lipids, which are below the range, as expected.…”

“…Recently, van der Heijden et al (2015) showed that CBR values for seven narcotics tested in three species ranged from 2.1 to 16.1 mmol/kg fresh wt. McCarty et al (2013) reviewed a large set of CBR values and reported a mean CBR of 1.80 mmol/kg fresh wt for 29 narcotics in algae, invertebrates and fish. CBR values for phenanthrene in invertebrates ranged from 0.32 to 8.40 mmol/kg (McCarty et al, 2013).…”

“…McCarty et al (2013) reviewed a large set of CBR values and reported a mean CBR of 1.80 mmol/kg fresh wt for 29 narcotics in algae, invertebrates and fish. CBR values for phenanthrene in invertebrates ranged from 0.32 to 8.40 mmol/kg (McCarty et al, 2013). Our CBR value of 2.72 mmol/kg fresh wt fits very well into this range (Table 2).…”

A fugacity‐based toxicokinetic model for narcotic organic chemicals in fish

“…Because of the relatively short test duration, we assume negligible biotransformation and fish growth to occur during the test. These wet weight lethal body burdens are consistent with values associated with a baseline toxicity (narcotic) mode of action . Input parameters used in these simulations are presented in Tables , , and .…”