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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Reference
Endpoint:
bioaccumulation in aquatic species: invertebrate
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1982
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: no guideline study, no glp, but method good described
Qualifier:
no guideline available
Principles of method if other than guideline:
Following the two-month acclimatization period, the
mussels were distributed among four glass aquaria,
each containing 8 1 of sea water of 36.5°/00 S obtained
from the area of collection. Experiments started with
60 organisms in each aquarium. In the first aquarium,
organisms were maintained in a medium containing
100 J.lg 1-1 Sn (as SnC14), while the second and third,
they were subjected to 250 and 500 J.lg 1-1 Sn respectively.
The fourth aquarium, without added tin, served
as a control. Experiments were conducted at 22±2*C
for 30 days. During this period, the sea water was
changed daily end, after each change, tin was added
from a stock solution containihg 1 000 mg 1-1 SnC14
in distilled water. Six contaminated and six control
mussels were sampled at time intervals of 3, 7, 14, 21
and 30 days and deep-frozen pending analyses.

At the end of the 30-day bioaccumulation period, a
further 30-day loss period was begun to investigate
whether mussels could eliminate the accumulated tin.
AU aquaria were cleaned of precipitated and adsorbed
material; they were scraped with a brush and washed
in following order: with tap water and then with diluted
(15%) HCl, again with tap water and finally with
sea water. Contaminated mussels (30 mussels in each
aquarium) were then placed in the tin-free aquaria.
Experimental conditions were similar to those described
in the previous paragraph, except that tin was not
added to any aquarium. Six test organisms and six
contrais were removed at the same time intervals (3-7-
14-21 and 30 day) as in the bioaccumulation experiment.
The mussels were fed neither during the bioaccumulation
nor the loss period.
Dry weights are based on the means of ten mussels
taken on da ys 0, 30 and 60 from each aquarium. Determination
of dry weight was carried out according to
the procedure described by Bernhard (1976).

Frozen mussels were first thawed and removed from
their shells. The soft tissues shells of each musset were
then weighed and digested in a concentrated nitric acid
(Aristar) and perchloric acid (Aristar) mixture with a
HN03:HC104 ratio of 4:1 (v/v). Digestion was carried
out at 100*C. The samples were first digested in hot
nitric acid for 12 h and then perchloric acid was added.
After twelve hours, the liquid medium was allowed to
evaporate. Following evaporation, dry samples were
collected in 25 ml of distilled water and stored in a
refrigerator until analysis. Samples were analysed by a
Varian Techtron AA6 atomic absorption spectrophotometer,
using the analytical procedure described by Braman
and Topkins (1979) and Hodge et al. (1979), and
improved by Tugrul (1982).
GLP compliance:
no
Radiolabelling:
no
Vehicle:
no
Test organisms (species):
other aquatic mollusc: Brachidontes variabilis
Route of exposure:
aqueous
Test type:
static
Water / sediment media type:
not specified
Remarks:
saltwater
Total exposure / uptake duration:
30 d
Total depuration duration:
60
Nominal and measured concentrations:
0, 100, 250, 500µg/L Sn4+ added as SnCl4
Type:
BCF
Value:
6.41 dimensionless
Basis:
other: concentration in soft tissue
Time of plateau:
3 d
Calculation basis:
kinetic
Remarks on result:
other: Conc.in environment / dose:100 µg/l
Type:
BCF
Value:
1.92 dimensionless
Basis:
other: concentration in soft tissue
Time of plateau:
3 d
Calculation basis:
kinetic
Remarks on result:
other: Conc.in environment / dose:250 µg/l
Type:
BCF
Value:
0.76 dimensionless
Basis:
other: concentration in soft tissue
Time of plateau:
3 d
Calculation basis:
kinetic
Remarks on result:
other: Conc.in environment / dose:500 µg/l

The table shows the resulting metal concentrations in the mussels. The results are the mean of four individuals analyzed separately.

After the 30-day accumulation period, the highest tin concentration was observed in organisms exposed to

the lowest (100 µg/l) external concentration. In this group, a slight increase was observed with time. The accumulation pattern was similar in both the 250 and 500 µg/l -groups: accumulation reached its maximum value at day 3 of the experiment, after which a conspicuous equilibrium occurred in these two groups and was maintained until the end of the experiments

 

 

Sn redium

% dry wt

Tin concentration in soft tissue

(ng / g wet wt)

BCF day30

BCF day60

Day 0

Day 30

Day 60

 % loss

0 µg/l

12.4±1.8

14

19

22

-

-

-

100 µg/l

-

15

641

132

79.4

6.41

1.32

250 µg/l

-

13

298

57

80.9

1.92

0.23

500 µg/l

-

14

382

69

81.9

0.76

0.14

 

In control mussels the tin concentration was slightly increased by the end of a 60-day experimental period.

The concentration factor was higher in 100 µg/l -group than in either of the other two groups The uptake of tin decreased with increasing concentration of Tin tetrachloridein the sea water. Though the tin oncentration in the 500 µg/l -groups was higher than that in the 250 µg/l -group,it may be seen from table that the latter group established a greater accumulation factor relative to the sea water than the former. In ail test groups; shells contained a significant amount of tin.

 

In conclusion the high determinate BCF in this experiment was 6.41

Validity criteria fulfilled:
not applicable
Remarks:
no guideline methode
Conclusions:
The highest determinete BCF in this experiment is 6.41

Executive summary:

A bivalve mollusc of Indo-Pacific origin, Brachidontes variabilis (Krauss), was kept in different tin concentrations (100, 250 and 500

µg/l) for 30 days to study the accumulation of tin, and for a further 30 days in clean sea water to determine how much tin was eliminated. Ail of the groups showed a significant accumulation, higher in the 100 µg/l group than in the 250 and 500 µg/l groups. The rate of uptake decreased with increase in externat tin concentration. The subsequent rate of loss of tin was constant and independent of the internai tin concentration in ali contaminated mussels. After the 30 day elimination period, the mussels contained 20% of the tin taken up during the accumulation period.

Description of key information

One reliable (RL2) aquatic bioaccumulation study indicates a low potential for bioaccumulation of Sn in aquatic freshwater organisms:

The bivalve mollusc, Brachidontes variabilis (Krauss), was exposed to different tin concentrations (100, 250 and 500 µg Sn/L) in the form of SnCl4 for 30 days to study the accumulation of tin, and for a further 30 days in clean sea water to determine how much tin was eliminated. All of the groups showed a significant accumulation. Bioaccumlation was higher in the 100 µg Sn/L group than in the 250 and 500 µg Sn/L groups. The rate of uptake decreased with increase in external tin concentration. The subsequent rate of loss of tin was constant and independent of the internal tin concentration in all contaminated mussels. After the 30 day elimination period, the mussels contained 20% of the tin taken up during the accumulation period. The highest determined BCF in this experiment was 6.41, determined by the kinetic approach.

Thus, it is concluded that Sn has a low potential for bioaccumulation in freshwater organisms.

Key value for chemical safety assessment

Additional information