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Bioconcentration and elimination of Triphenyltin hydroxide in fish
Marine En vironmen tal Research 28 (1989) 215-218
Bioconcentration and Elimination of Triphenyitin Hydroxide in Fish J. Wieke Tas, Joop L. M. Hermens, Martin Van den Berg & Willem Seinen Environmental Toxicology Section, Research Institute Toxicology, University of Utrecht, PO Box 80176, 3508 TD Utrecht, The Netherlands
A BSTRA CT The bioconcentration and elimination of 14C-radiolabelled triphenyltin hydroxide ( T P T H ) was studied in two fish species: guppy (Poecilia reticulata) and rainbow trout (Salmo gairdneri) larvae. Uptake and elimination rate constants (kl and k 2, respectively) were estimated, assuming .first-order kinetics. For the guppy k 1 and k 2 were estimated to have a value of 2"94 4- 0.33 ml/g h and 0"0002 4- 0"0012 per h, respectiveO,. For the rainbow trout larvae these numbers were 0"87 4- 0.13 ml/g h and O'O013 +_O'O003 per h, respectively. The ratios between the concentrations o['TPTH in fish and water at the end of the period of exposure were 632 ml/g jor guppy after 8 days ~[ exposure, and 82ml/g .for rainbow trout after 4days of exposure. Since equilibrium was not reached in either experiment, these concentration ratios underestimate the real hioconcentration./'actor.
Organotins are used as agricultural fungicides. Triphenyltin hydroxide (TPTH) is a very active agent for the control of potato and sugar beet blight. As a result of the application of TPTH considerable amounts are introduced into the environment. In this study we present results on the accumulation and elimination of TPTH in guppy and rainbow trout larvae. A static and a semi-static system were used. In the static system the test water was not renewed, while in the semi-static system the test water was renewed every day during the first 3 days and every other day during the remaining period. After the period of exposure the fish were replaced in clean water to study the elimination. The water was renewed every o t h e r day. 215 Marine Environ. Res. 0141-1136/90/$03'50 !i~ 1990 Elsevier Science Publishers Ltd, England. Printed in Great Britain
216
J. Wieke Tas, Joop L. M. Hermens, Martin Van den Berg, Willem Seinen TABLE 1 Concentration Ratios of TPTH Between Fish Tissue (wet weight) and Aqueous Phase During the Exposure Period Time (days)
0.2 1 2 4 6 8
Concentration ratio qfl [14C] TPTH [fish]/[water], (ml/g) Gupp.v
Rainbow trout
27_+3 62_+ 14 149_+25 220 + 31 332-+37 632 -+ 180
7_+0.7 38_+8 60_+5 82 -+ 9
Values expressed as means _+SD.
Fish were held in 41itres of non-aerated tap water. '4C-Radiolabelled TPTH was added by a stock solution in methanol so that the methanol concentration in the water did not exceed 2.5 x 10- 3 % by volume. Guppies were kept at 20°C, and rainbow trout larvae at 10°C. Guppies were exposed to 6/2g/litre TPTH for 8 days (semi-static). After this period the elimination was studied for 6days. Rainbow trout larvae were exposed directly after hatching to 3/2g/litre TPTH for 4 days (static). Then the elimination was studied until the larvae started swimming ( 12 days). The pH of the test water was between 7 and 8, and the oxygen concentration was at least 6 mg/litre. Water and fish samples were taken at regular time intervals. The amount of TPTH was measured by counting the radioactivity. Radioactivity in the samples, expressed as concentrations of TPTH in fish during period of exposure and elimination, are given in Tables 1 and 2, respectively. Calculations of TPTH concentrations in fish tissues and aqueous phases were done by assuming that the counted radioactivity was only due to TPTH. Tsuda et al.1 found that 97% of the organotin in goldfish was present as TPT, so it seems unlikely that a high proportion of the 14C label was in the metabolite pool. During the period of exposure the concentration of TPTH in the water remained constant in both experiments. During the elimination period the concentration of the excreted TPTH in the water remained below the detection limit. No equilibrium was reached in either experiment between the [~'~C]TPTH concentration in fish tissue and in the aqueous phase, after the period of exposure. Calculations of uptake and elimination rate constants
Triphenyltin hydroxide in fish
217
TABLE 2
Logarithms of the Concentrations of [14C]TPTH in Fish Tissue During Elimination Period In [ TPTH] in fish
Time (days)
0 0.3 1.3 2 3 4 6 8 10 13
(ltg/kg! Guppy
Rainbow trout
8.2 + 7.0 7.9_+5-5 8.3+6.3 8.1 +7.0 .... 8-2 _+1.4
5.4 _+3.3 5.3_+2.8 5.4_+3.6 5.2 + 2.0 5.2_+4.1 5.0_+ 1.6 5.1 _+4-2
Values expressed as means _+SD. (kl and k 2, respectively) were carried out by assuming first-order kinetics. The uptake rate constant was calculated from the increase in the concentration ratio of T P T H between fish and water versus time (Table l). The elimination rate constant was calculated from the logarithm of the T P T H concentration in fish versus time (Table 2). Eight days' exposure of guppy to TPTH resulted in a fish/water concentration ratio of 632 ml/g (no equilibrium). The k I was 2.94 _+0.33 ml/g h and k 2 0.0002 _+0-0012 per h. Based upon the elimination rate constant and the period of exposure it is possible to calculate how far the situation is from equilibrium. 2 Consequently, an estimation of the bioconcentration factor can be made. For the guppy the standard deviation o f k 2 is rather high, so an estimation of the maximum clearance rate constant of 0"0012 per h was used for this calculation. It was found that maximum 24% of equilibrium was reached during the 8 days period. As a result the actual bioconcentration factor is at least approximately 3 x 103 ml/g. Four days' exposure of rainbow trout larvae to TPTH resulted in a concentration ratio of 82 ml/g (no equilibrium). The k 1 and k 2 were 0-87 + 0.13 ml/g h and 0"0013_ 0"0003 per h, respectively. In the case of rainbow trout a maximum 12% of equilibrium is reached after 4days. Hence, the expected bioconcentration factor is approximately 8 × 102 ml/g. In this study it was found that the TPTH concentration in the fish increases up till 8 days. For another organotin c o m p o u n d (bis(tributyltin) oxide), Ward et al. 3 found that an equilibrium was not reached, even after an
218
j. Wieke Tas, Joop L. M. Hermens, Martin Van den Berg, Willem Seinen
exposure period of 58 days. Chemicals which are accumulated and very slowly eliminated are a potential threat to the environment. Additional research that also pays attention to the formation of metabolites will be carried out in the near future. From the results of the described experiments several conclusions can be drawn: (1)
(2)
Under the described conditions no equilibrium was reached. Although the uptake of T P T H is very rapid, much longer accumulation periods are required to reach a state of equilibrium between the concentrations of T P T H in fish tissue and the aqueous phase. The elimination of [14C]TPTH from fish tissue is extremely slow, and is comparable to that of other hydrophobic chemicals such as polychlorinated hydrocarbons.
REFERENCES 1. Tsuda, T., Wada, M., Aoki, S. & Matsui, Y., Toxicol. Environ. Chem., 18 (1988) 11 20. 2. Hawker, D. W. & Connel, D. W., Wat. Res., 22(6) (1988) 701-7. 3. Ward, C. S., Cram, G. C., Parrish, P. R., Trachman, H. & Slessinger, A., In Aquatic Toxicology and Hazard Assessment: Fourth Conference, ASTM STP 737, eds D. R. Branson & K. L. Dickson. American Society for Testing and Materials, Philadelphia, 1981, pp. 183 200.
Bioconcentration and Elimination of Triphenyitin Hydroxide in Fish J. Wieke Tas, Joop L. M. Hermens, Martin Van den Berg & Willem Seinen Environmental Toxicology Section, Research Institute Toxicology, University of Utrecht, PO Box 80176, 3508 TD Utrecht, The Netherlands
A BSTRA CT The bioconcentration and elimination of 14C-radiolabelled triphenyltin hydroxide ( T P T H ) was studied in two fish species: guppy (Poecilia reticulata) and rainbow trout (Salmo gairdneri) larvae. Uptake and elimination rate constants (kl and k 2, respectively) were estimated, assuming .first-order kinetics. For the guppy k 1 and k 2 were estimated to have a value of 2"94 4- 0.33 ml/g h and 0"0002 4- 0"0012 per h, respectiveO,. For the rainbow trout larvae these numbers were 0"87 4- 0.13 ml/g h and O'O013 +_O'O003 per h, respectively. The ratios between the concentrations o['TPTH in fish and water at the end of the period of exposure were 632 ml/g jor guppy after 8 days ~[ exposure, and 82ml/g .for rainbow trout after 4days of exposure. Since equilibrium was not reached in either experiment, these concentration ratios underestimate the real hioconcentration./'actor.
Organotins are used as agricultural fungicides. Triphenyltin hydroxide (TPTH) is a very active agent for the control of potato and sugar beet blight. As a result of the application of TPTH considerable amounts are introduced into the environment. In this study we present results on the accumulation and elimination of TPTH in guppy and rainbow trout larvae. A static and a semi-static system were used. In the static system the test water was not renewed, while in the semi-static system the test water was renewed every day during the first 3 days and every other day during the remaining period. After the period of exposure the fish were replaced in clean water to study the elimination. The water was renewed every o t h e r day. 215 Marine Environ. Res. 0141-1136/90/$03'50 !i~ 1990 Elsevier Science Publishers Ltd, England. Printed in Great Britain
216
J. Wieke Tas, Joop L. M. Hermens, Martin Van den Berg, Willem Seinen TABLE 1 Concentration Ratios of TPTH Between Fish Tissue (wet weight) and Aqueous Phase During the Exposure Period Time (days)
0.2 1 2 4 6 8
Concentration ratio qfl [14C] TPTH [fish]/[water], (ml/g) Gupp.v
Rainbow trout
27_+3 62_+ 14 149_+25 220 + 31 332-+37 632 -+ 180
7_+0.7 38_+8 60_+5 82 -+ 9
Values expressed as means _+SD.
Fish were held in 41itres of non-aerated tap water. '4C-Radiolabelled TPTH was added by a stock solution in methanol so that the methanol concentration in the water did not exceed 2.5 x 10- 3 % by volume. Guppies were kept at 20°C, and rainbow trout larvae at 10°C. Guppies were exposed to 6/2g/litre TPTH for 8 days (semi-static). After this period the elimination was studied for 6days. Rainbow trout larvae were exposed directly after hatching to 3/2g/litre TPTH for 4 days (static). Then the elimination was studied until the larvae started swimming ( 12 days). The pH of the test water was between 7 and 8, and the oxygen concentration was at least 6 mg/litre. Water and fish samples were taken at regular time intervals. The amount of TPTH was measured by counting the radioactivity. Radioactivity in the samples, expressed as concentrations of TPTH in fish during period of exposure and elimination, are given in Tables 1 and 2, respectively. Calculations of TPTH concentrations in fish tissues and aqueous phases were done by assuming that the counted radioactivity was only due to TPTH. Tsuda et al.1 found that 97% of the organotin in goldfish was present as TPT, so it seems unlikely that a high proportion of the 14C label was in the metabolite pool. During the period of exposure the concentration of TPTH in the water remained constant in both experiments. During the elimination period the concentration of the excreted TPTH in the water remained below the detection limit. No equilibrium was reached in either experiment between the [~'~C]TPTH concentration in fish tissue and in the aqueous phase, after the period of exposure. Calculations of uptake and elimination rate constants
Triphenyltin hydroxide in fish
217
TABLE 2
Logarithms of the Concentrations of [14C]TPTH in Fish Tissue During Elimination Period In [ TPTH] in fish
Time (days)
0 0.3 1.3 2 3 4 6 8 10 13
(ltg/kg! Guppy
Rainbow trout
8.2 + 7.0 7.9_+5-5 8.3+6.3 8.1 +7.0 .... 8-2 _+1.4
5.4 _+3.3 5.3_+2.8 5.4_+3.6 5.2 + 2.0 5.2_+4.1 5.0_+ 1.6 5.1 _+4-2
Values expressed as means _+SD. (kl and k 2, respectively) were carried out by assuming first-order kinetics. The uptake rate constant was calculated from the increase in the concentration ratio of T P T H between fish and water versus time (Table l). The elimination rate constant was calculated from the logarithm of the T P T H concentration in fish versus time (Table 2). Eight days' exposure of guppy to TPTH resulted in a fish/water concentration ratio of 632 ml/g (no equilibrium). The k I was 2.94 _+0.33 ml/g h and k 2 0.0002 _+0-0012 per h. Based upon the elimination rate constant and the period of exposure it is possible to calculate how far the situation is from equilibrium. 2 Consequently, an estimation of the bioconcentration factor can be made. For the guppy the standard deviation o f k 2 is rather high, so an estimation of the maximum clearance rate constant of 0"0012 per h was used for this calculation. It was found that maximum 24% of equilibrium was reached during the 8 days period. As a result the actual bioconcentration factor is at least approximately 3 x 103 ml/g. Four days' exposure of rainbow trout larvae to TPTH resulted in a concentration ratio of 82 ml/g (no equilibrium). The k 1 and k 2 were 0-87 + 0.13 ml/g h and 0"0013_ 0"0003 per h, respectively. In the case of rainbow trout a maximum 12% of equilibrium is reached after 4days. Hence, the expected bioconcentration factor is approximately 8 × 102 ml/g. In this study it was found that the TPTH concentration in the fish increases up till 8 days. For another organotin c o m p o u n d (bis(tributyltin) oxide), Ward et al. 3 found that an equilibrium was not reached, even after an
218
j. Wieke Tas, Joop L. M. Hermens, Martin Van den Berg, Willem Seinen
exposure period of 58 days. Chemicals which are accumulated and very slowly eliminated are a potential threat to the environment. Additional research that also pays attention to the formation of metabolites will be carried out in the near future. From the results of the described experiments several conclusions can be drawn: (1)
(2)
Under the described conditions no equilibrium was reached. Although the uptake of T P T H is very rapid, much longer accumulation periods are required to reach a state of equilibrium between the concentrations of T P T H in fish tissue and the aqueous phase. The elimination of [14C]TPTH from fish tissue is extremely slow, and is comparable to that of other hydrophobic chemicals such as polychlorinated hydrocarbons.
REFERENCES 1. Tsuda, T., Wada, M., Aoki, S. & Matsui, Y., Toxicol. Environ. Chem., 18 (1988) 11 20. 2. Hawker, D. W. & Connel, D. W., Wat. Res., 22(6) (1988) 701-7. 3. Ward, C. S., Cram, G. C., Parrish, P. R., Trachman, H. & Slessinger, A., In Aquatic Toxicology and Hazard Assessment: Fourth Conference, ASTM STP 737, eds D. R. Branson & K. L. Dickson. American Society for Testing and Materials, Philadelphia, 1981, pp. 183 200.