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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Reference
Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Principles of method if other than guideline:
Uptake experiment: bioaccumulation of TNT in 11-week-old fathead minnows was examined by exposing 50 fish in 16 L of 4.4 μmol/L (1mg/L) at 23 +/- 1C in a 20-: aquarium. Three fish were sampled from the aquarium after 10, 20, 30 and 45 min and 1, 2, 4, 6, 9, 12 h of initiation of exposure by dipnet, rinsed with DTW, blotted dry on absorbent paper, killed by pithing, and stored in preweighed 1.5-ml bead beating vials at 80C before undergoing solvent extraction. A 1-ml sample of exposure solution was taken at initiation of the exposure and at tissue collection time points 6 and 12 h.

Elimination experiment: elimination of TNT from the fathead minnow was measured using 40 eleven-week-old fathead minnows exposed to 4.4 μmol/L TNT for 6h as described above. Exposed fish were transferred to noncontaminated DTW and sampled, as described above, in triplicate 0, 5, 10, 15, 30, and 45 min., and 1, 3, 6, and 18h. Whole-fish samples were stored in preweighed 1.5ml bead beating vials at 80C before undergoing solvent extraction.

Additionaly BCF values were measured during toxicity study (4 and 10d exposure) - see also section 6.1.2.
GLP compliance:
not specified
Radiolabelling:
no
Test organisms (species):
Pimephales promelas
Route of exposure:
aqueous
Test type:
semi-static
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
>= 6 - <= 12 h
Nominal and measured concentrations:
Uptake experiment: 50 fish exposed to 4.4 μmol/L (1mg/L) TNT.
Elimination experiment: 40 fish exposed to 4.4 μmol/L TNT.
Details on estimation of bioconcentration:
The BCFs were estimated from the uptake experiment and the uptake portion of the elimination experiment using the following equation: BCF = Css/Cw where Css is the steady-state concentration of total TNT in the organism (μmol/kg) and Cw is the concentration of the total TNT in the exposure water (μmol/L).
Type:
BCF
Value:
8.4 L/kg
Basis:
other: mean tissue concentration
Time of plateau:
6 h
Calculation basis:
steady state
Remarks on result:
other: uptake experiment
Remarks:
Conc.in environment / dose:4.4 μmol/L (1mg/L) TNT in water
Type:
BCF
Value:
4.68 L/kg
Basis:
other: mean tissue concentration
Time of plateau:
6 h
Calculation basis:
steady state
Remarks on result:
other: elimination experiment
Remarks:
Conc.in environment / dose:4.4 μmol/L (1mg/L) TNT in water
Key result
Type:
BCF
Value:
4.97 L/kg
Basis:
other: mean tissue concentration
Time of plateau:
6 h
Calculation basis:
steady state
Remarks on result:
other: uptake experiment
Remarks:
Conc.in environment / dose:TNT only
Type:
BCF
Value:
ca. 1.7 L/kg
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: 10 d exposure
Remarks:
Conc.in environment / dose:9.1 μmol/L TNT in water
Type:
BCF
Value:
ca. 5.5 L/kg
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: 4 d exposure
Remarks:
Conc.in environment / dose:7.5 μmol/L TNT in water
Type:
BCF
Value:
ca. 9.2 L/kg
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: 4 d exposure
Remarks:
Conc.in environment / dose:17.3 μmol/L TNT in water
Type:
BCF
Value:
ca. 2.1 L/kg
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: 10 d exposure
Remarks:
Conc.in environment / dose:2.8 μmol/L TNT in water
Type:
BCF
Value:
ca. 2.7 L/kg
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: 10 d exposure
Remarks:
Conc.in environment / dose:6.8 μmol/L TNT in water
Type:
BCF
Value:
2.27 L/kg
Basis:
other: mean tissue concentration
Time of plateau:
6 h
Calculation basis:
steady state
Remarks on result:
other: elimination experiment
Remarks:
Conc.in environment / dose:TNT only
Key result
Elimination:
yes
Parameter:
DT50
Depuration time (DT):
0.31 h
Elimination:
yes
Parameter:
other: elimination rate
Depuration time (DT):
2.24 h
Conclusions:
The present study presents low bioaccumulation potential and rapid uptake of TNT in the fathead minnow.

Description of key information

To study bioaccumulation, fish were exposed to 4.4 μmol/L (1 mg/L) of TNT for 12h. Rapid bioaccumulation of TNT occurred within the first 10 min of exposure. Elimination of total TNT (molar sum of TNT and degradation products 2- and 4 -aminodinitrotoluenes) was fast, with an elimination rate of 2.24/h and a short half-life (0.31 h). The bioconcentration factors determined using 6 -h mean tissue and water concentrations of total TNT were 8.40 and 4.68 L/kg for the uptake experiment and the uptake portion of the elimination experiments respectively.

The present study presents low bioaccumulation potential and rapid uptake of TNT in the fathead minnow.

Key value for chemical safety assessment

BCF (aquatic species):
4.97 L/kg ww

Additional information