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Assessment of organotin in waters of selected gulf of Maine estuaries
Pergamon PII: S0025--326X(97)00030-1
Marine Pollution Bulletin, Vol. 34, No. 10, pp. 802-804, 1997 © 1997 Elsevier Science Ltd All rights reserved. Printed in Great Britain 0025-326X/97 $17.00+ 0.00
Assessment of Organotin in Waters of Selected Gulf of Maine Estuaries PETER FOSTER LARSEN*, ROBERT J. H U G G E T T t and MICHAEL A. U N G E R ? *Kennebec Area Research Endowment, Bigelow Laboratory for Ocean Sciences, West Boothbay Harbor, M E 04575, USA tSchool of Marine Science, Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, Virginia 23062, USA
It is widely accepted that tributyltin (TBT) is one of the most toxic agents ever intentionally introduced into the coastal marine environment. Its principal use has been as a biocide in antifouling paints applied to the hulls of boats and ships from whence it enters the water column through leaching and/or subsequent scraping of the hulls. For this reason, environmental levels of TBT are generally highest at sites where boating activity is concentrated such as in the vicinity of marinas and boatyards (Dowson et al., 1992). Concern about the impact of TBT on non-target species arose in 1982 when Alzieu et al. (1982) related the severe decline of the Pacific oyster (Crassostrea gigas) harvest in Arcachon Bay, France to TBT leachates from the hulls of pleasure boats. Several subsequent field and laboratory studies have documented that extremely low environmental levels of TBT can have lethal and sublethal effects on ecologically and economically important species. Examples include imposex in several gastropod species (Gibbs et al., 1988; Bryan et al., 1989; Bryan and Gibbs, 1991), malformed oysters (Crassostrea gigas) (Alzieu et al., 1989) and increased mortality and slower growth of blue mussel (Mytilus edulis) larvae (Beaumont and Budd, 1984). The severe impact of TBT on non-target species has led to bans on its use as an anti-fouling agent on boats under 25 m in many jurisdictions (1987 in the State of Maine). These bans have resulted in reductions in environmental levels of TBT, with some concommitant reductions in apparent effects (Page and Widdows, 1991; Waite et al., 1991; Huggett et al., 1992). Nevertheless, seawater concentrations in many areas, including those subject to regulations, remain above levels which have been documented to produce bioeffects (Alzieu et al., 1989; Cleary, 1991). In spite of the importance of marine resources in the mid-coast region of the Gulf of Maine, including the presence of
Contribution 97002 of the Bigelow Laboratory for Ocean Sciences, Contribution 2071 of the Virginia Institute of Marine Science.
802
species which have been impacted by low concentrations of TBT elsewhere, knowledge of organotin distributions in the region is lacking. In August and September 1991, the water column at 11 representative estuarine sites in the mid-coast Maine region of the Gulf of Maine were surveyed to screen for potential organotin contamination. The range of sites included a busy commercial shipping/offshore fishing port (site 1), an open water embayment (2), the tidal freshwater confluence of the Kennebec and Androscoggin Rivers (3), below a major shipbuilding facility in the energetic Kennebec estuary (4), near pleasure boat mooring areas (5, 6, 7), at the mouths of small estuaries draining from pleasure boat marinas (8, 9), in a yachting/inshore fishing harbour (10) and in a relatively undeveloped estuary (11) (Fig. 1). The pleasure boating season in the Gulf of Maine is relatively short, and density of boats is low, compared to other sites surveyed for organotin. All sites are well-flushed by a semidiurnal tide of approximately 3 m. Actual sample locations were chosen to avoid possible contamination hotspots such as boatyards and drydock facilities. Water samples were taken at high or ebbing tides by immersing 2 litre polycarbonate bottles to a depth of 15-20 cm. The acid cleaned bottles were rinsed with seawater prior to obtaining a sample to further minimize contamination. The samples were immediately acidified to a pH of 2 with HCI and stored in the dark at 4°C until analysis. The analytical procedure used has been described previously by Unger et al. (1986). Briefly, liquid-liquid extraction with hexane-tropolone was used to remove the organotins, followed by Grignard derivatization to form hexyl adducts. After cleaning by column chromatography, the derivatized organotins were quantified by capillary gas chromatography with flame photometric detection using tripentyltin as an internal standard. In selected samples the presence of TBT was verified by mass spectrometry. For TBT + the detection limit was about 1 ng 1-1. The results of the late summer 1991 spatial survey of TBT and its degradation products in the water column of the estuaries of mid-coast Maine are presented in
Volume 34]Number 10/October 1997
5
0
00'
•
I
I
I
I
Nautical Miles
I"
s ~ m Estuary!
Kennebec Estuary
55' !
,:N
4~ 50'
'
O
45'
o /
•
Catoe Sinai ,I
69"50' 40'
; ~
"
69*40'
Ca~oBay
0 t
i
h
~
i
Nautical Miles I
70*00'
70o10 '
Fig. 1 Locations of seawater organotin sampling sites in mid-coast Maine.
TABLE 1 Seawater organotin concentrations at selected Gulf of Maine sites, n.d. indicates not detected. Organotion concentration (ng I- 1) Site
Sample location
Sampling date
Tide stage
TBT
DBT
MBT
1 2 3 4 5 6 7 8 9 10 I1
Portland Harbor Casco Bay Merrymeeting Bay Kennebec Estuary Robinhood Cove Quahog Bay Mere Point Bay Harrasseket River Royal River Boothbay Harbor Damariscotta River
6 August 6 August 8 August 8 August 8 August 6 September 6 September 6 September 6 September 9 September 9 September
High slack Very early ebb Early ebb Mid ebb Late ebb Early ebb Mid ebb Mid ebb Late ebb late ebb late ebb
7 1 <1 2 2 3 <1 3 3 11 <1
<1 1 n.d. n.d.
<1 1 n.d. n.d. <1 <1 <1 n.d. n.d. 4 <1
T a b l e 1. S e a w a t e r T B T c o n c e n t r a t i o n s a t these sites c a n b e c a t e g o r i z e d as u n c o n t a m i n a t e d ( < 3 n g l - t ) o r lightly c o n t a m i n a t e d ( 3 - 2 0 n g 1 - t ) u s i n g the criteria o f D o w s o n et al. (1992).
T h e d e s i g n o f this p r e l i m i n a r y s u r v e y h a s u n a v o i d a b l e limitations which should be noted. First, the lack of s a m p l e r e p l i c a t i o n , i n c o n c e r t w i t h the l o w c o n c e n t r a t i o n s e n c o u n t e r e d , does n o t a l l o w m e a n i n g f u l c o n 803
Marine Pollution Bulletin sideration o f the a p p a r e n t geographic variation. Samples were taken late in the b o a t i n g season when m u c h o f the T B T in b o a t paint applied in the spring m a y have leached out. Studies in other regions suggest that o r g a n o t i n levels in the water and biota tend to be higher earlier in the s u m m e r (Hall et al., 1987; Page and Widdows, 1991). T h e sampling p r o g r a m avoided the interior o f m a r i n a s a n d dense m o o r i n g fields which would have u n d o u b t e d l y yielded higher water c o l u m n concentrations. In addition, tidal and temporal variations have a p r o n o u n c e d effect on water c o l u m n T B T concentrations. Previous investigators have noted variations in T B T c o n c e n t r a t i o n by a factor o f 2 (Cleary, 1991) to perhaps 20 (Clavell et al., 1986) over a tidal cycle. H u g g e t t et aL (1986) measured concentrations varying by an order o f m a g n i t u d e at a single site in a week's period. Clearly, future surveys in the G u l f o f Maine need to take into a c c o u n t the seasonal a n d tidal dynamics o f the region. In conclusion, f o u r years after the use o f T B T on vessels < 25 m was b a n n e d in the State o f Maine, T B T and its d e g r a d a t i o n products, D B T and M B T , were detected at m o s t o f the estuaries sampled in the midcoast Maine region o f the G u l f o f Maine. Concentrations were low relative to those reported f r o m crowded marinas a n d boatyards. Considering the high spatial and temporal variability o f seawater T B T concentrations, and its affinity for concentrating in the surface microlayer (Cleary a n d Stebbings, 1987), m o r e detailed surveys o f selected e m b a y m e n t s are indicated. Such surveys should be designed to u n c o v e r possible sediment reserviors f r o m which o r g a n o t i n s m a y be remobilized (Unger et al., 1988). This research was supported in part by the Kennebec Area Research Endowment. We are grateful to the Maine Maritime Academy for the loan of the R/V Panthalass. Todd LaJeunesse, Jim Kulpa, Jed Goldstone and Bill Wilson assisted with the field program. David Page and Christopher Heinig provided expert advice on technical aspects and resource species. Ellen Travelstead supervized the organotin analyses of environmental samples. The comments of an anonymous reviewer are gratefully acknowledged. Alzieu, C., Heral, T., Thiband, Y. and Dardignac, M. T. (1982) Influence des peintures antisalissures sur la calcification de la coquille de l'huiture Crassostrea gigas. Rev. Tray. Inst. Peches Merit. 45, 101-116.
804
Alzieu, C., SanJuan, J., Michel, P., Borel, M. and Dreno, J. P. (1989) Monitoring and assessment of butyltins in Atlantic coastal waters. Marine Pollution Bulletin 20, 22-26. Beaumont, A. R. and Budd, M. D. (1984) High mortality of the larvae of the common mussel at low concentrations of tributyltin. Marine Pollution Bulletin 15, 402-405. Bryan, G. W. and Gibbs, P. E. (1991) Impact of low concentrations of TBT on marine organisms: A review. In Metal Ecotoxicity: Concepts and Applications, eds M. C. Newman and A. W. Mclntosh, pp. 323-361. Inc. Ann Arbor, Boca Raton, Boston. Bryan, G. W., Gibbs, P. E., Huggett, R. J., Curtis, L. A., Bailey, D. S. and Dauer, D. E. (1989) Effects of tributyltin pollution on the mud snail, llyanassa obsoleta, from the York River and Sarah Creek, Chesapeake Bay. Marine Pollution Bulletin 20, 458-462. Clavell, C., Seligman, P. F. and Stang, P. M. (1986) Automated analysis of organotin compounds: a method for monitoring butyltins in the marine environment. In Proc. Oceans '86 Organotin Symposium, ed. M. A. Champ, pp. 1152-1154. Institute of Electrical and Electronic Engineers, New York, USA. Cleary, J. J. (1991) Organotin in the marine surface microlayer and subsurface waters of South-west England: Relation to toxicity thresholds and the UK environmental quality standard. Marine Environmental Research 32, 213-222. Cleary, J. J. and Stebbings, R. D. (1987) Organotin in the surface microlayer and subsurface waters of southwest England. Marine Pollution Bulletin 18, 238-246. Dowson, P. H., Bubb, J. M. and Lester, J. N. (1992) Organotin distribution in sediments and waters of selected east coast estuaries in the UK. Marine Pollution Bulletin 24, 492-498. Gibbs, P. E., Pascoe, P. L. and Burt, G. R. (1988) Sex change in the female dog-whelk, Nucella lapillus, induced by tributyltin from antifouling paints. Journal of Marine Biology Association UK 68, 715-731. Hall, L. W., Lenkevich, M. J., Hall, W. S., Pinkney, A. E. and Bushong, S. J. (1987) Evaluation of butyltin compounds in Maryland waters of Chesapeake Bay. Marine Pollution Bulletin 18, 78-83. Huggett, R. J., Unger, M. A. and Westbrook, D. J. (1986) Organotin concentrations in the southern Chesapeake Bay. In Oceans "86 Proceedings, International Organotin Symposium, Vol. 4, pp. 12621265. Institute of Electrical and Electronic Engineers, New York. Huggett, R. J., Unger, M. A., Seligman, P. F. and Valkirs, A. O. (1992) The marine biocide Tributyltin: Assessing and managing environmental risks. Environmental Science and Technology 26, 232237. Page, D. S. and Widdows, J. (1991) Temporal and spatial Variation in levels of alkyltins in mussel tissues: A toxicological interpretation of field data. Marine Environmental Research 32, ! 13-129. Unger, M. A., Maclntyre, W. G., Grcaves, J. and Huggett, R. J. (1986) GC determination of butyltins in natural waters by flame photometric detection of hexyl derivatives with mass spectrometric confirmation. Chemosphere 15, 461-470. Unger, M. A., Maclntyre, W. G. and Huggett, R. J. (1988) Sorption behavior of tributyltin on estuarine and freshwater sediments. Environmental Toxicology and Chemistry 7, 907-915. Waite, M. E., Waldock, M. J., Thain, J. E., Smith, D. J. and Milton, S. M. (1991) Reductions in TBT concentrations in UK estuaries following legislation in 1986 and 1987. Marine Environmental Research 32, 89-111.
Marine Pollution Bulletin, Vol. 34, No. 10, pp. 802-804, 1997 © 1997 Elsevier Science Ltd All rights reserved. Printed in Great Britain 0025-326X/97 $17.00+ 0.00
Assessment of Organotin in Waters of Selected Gulf of Maine Estuaries PETER FOSTER LARSEN*, ROBERT J. H U G G E T T t and MICHAEL A. U N G E R ? *Kennebec Area Research Endowment, Bigelow Laboratory for Ocean Sciences, West Boothbay Harbor, M E 04575, USA tSchool of Marine Science, Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, Virginia 23062, USA
It is widely accepted that tributyltin (TBT) is one of the most toxic agents ever intentionally introduced into the coastal marine environment. Its principal use has been as a biocide in antifouling paints applied to the hulls of boats and ships from whence it enters the water column through leaching and/or subsequent scraping of the hulls. For this reason, environmental levels of TBT are generally highest at sites where boating activity is concentrated such as in the vicinity of marinas and boatyards (Dowson et al., 1992). Concern about the impact of TBT on non-target species arose in 1982 when Alzieu et al. (1982) related the severe decline of the Pacific oyster (Crassostrea gigas) harvest in Arcachon Bay, France to TBT leachates from the hulls of pleasure boats. Several subsequent field and laboratory studies have documented that extremely low environmental levels of TBT can have lethal and sublethal effects on ecologically and economically important species. Examples include imposex in several gastropod species (Gibbs et al., 1988; Bryan et al., 1989; Bryan and Gibbs, 1991), malformed oysters (Crassostrea gigas) (Alzieu et al., 1989) and increased mortality and slower growth of blue mussel (Mytilus edulis) larvae (Beaumont and Budd, 1984). The severe impact of TBT on non-target species has led to bans on its use as an anti-fouling agent on boats under 25 m in many jurisdictions (1987 in the State of Maine). These bans have resulted in reductions in environmental levels of TBT, with some concommitant reductions in apparent effects (Page and Widdows, 1991; Waite et al., 1991; Huggett et al., 1992). Nevertheless, seawater concentrations in many areas, including those subject to regulations, remain above levels which have been documented to produce bioeffects (Alzieu et al., 1989; Cleary, 1991). In spite of the importance of marine resources in the mid-coast region of the Gulf of Maine, including the presence of
Contribution 97002 of the Bigelow Laboratory for Ocean Sciences, Contribution 2071 of the Virginia Institute of Marine Science.
802
species which have been impacted by low concentrations of TBT elsewhere, knowledge of organotin distributions in the region is lacking. In August and September 1991, the water column at 11 representative estuarine sites in the mid-coast Maine region of the Gulf of Maine were surveyed to screen for potential organotin contamination. The range of sites included a busy commercial shipping/offshore fishing port (site 1), an open water embayment (2), the tidal freshwater confluence of the Kennebec and Androscoggin Rivers (3), below a major shipbuilding facility in the energetic Kennebec estuary (4), near pleasure boat mooring areas (5, 6, 7), at the mouths of small estuaries draining from pleasure boat marinas (8, 9), in a yachting/inshore fishing harbour (10) and in a relatively undeveloped estuary (11) (Fig. 1). The pleasure boating season in the Gulf of Maine is relatively short, and density of boats is low, compared to other sites surveyed for organotin. All sites are well-flushed by a semidiurnal tide of approximately 3 m. Actual sample locations were chosen to avoid possible contamination hotspots such as boatyards and drydock facilities. Water samples were taken at high or ebbing tides by immersing 2 litre polycarbonate bottles to a depth of 15-20 cm. The acid cleaned bottles were rinsed with seawater prior to obtaining a sample to further minimize contamination. The samples were immediately acidified to a pH of 2 with HCI and stored in the dark at 4°C until analysis. The analytical procedure used has been described previously by Unger et al. (1986). Briefly, liquid-liquid extraction with hexane-tropolone was used to remove the organotins, followed by Grignard derivatization to form hexyl adducts. After cleaning by column chromatography, the derivatized organotins were quantified by capillary gas chromatography with flame photometric detection using tripentyltin as an internal standard. In selected samples the presence of TBT was verified by mass spectrometry. For TBT + the detection limit was about 1 ng 1-1. The results of the late summer 1991 spatial survey of TBT and its degradation products in the water column of the estuaries of mid-coast Maine are presented in
Volume 34]Number 10/October 1997
5
0
00'
•
I
I
I
I
Nautical Miles
I"
s ~ m Estuary!
Kennebec Estuary
55' !
,:N
4~ 50'
'
O
45'
o /
•
Catoe Sinai ,I
69"50' 40'
; ~
"
69*40'
Ca~oBay
0 t
i
h
~
i
Nautical Miles I
70*00'
70o10 '
Fig. 1 Locations of seawater organotin sampling sites in mid-coast Maine.
TABLE 1 Seawater organotin concentrations at selected Gulf of Maine sites, n.d. indicates not detected. Organotion concentration (ng I- 1) Site
Sample location
Sampling date
Tide stage
TBT
DBT
MBT
1 2 3 4 5 6 7 8 9 10 I1
Portland Harbor Casco Bay Merrymeeting Bay Kennebec Estuary Robinhood Cove Quahog Bay Mere Point Bay Harrasseket River Royal River Boothbay Harbor Damariscotta River
6 August 6 August 8 August 8 August 8 August 6 September 6 September 6 September 6 September 9 September 9 September
High slack Very early ebb Early ebb Mid ebb Late ebb Early ebb Mid ebb Mid ebb Late ebb late ebb late ebb
7 1 <1 2 2 3 <1 3 3 11 <1
<1 1 n.d. n.d.
<1 1 n.d. n.d. <1 <1 <1 n.d. n.d. 4 <1
T a b l e 1. S e a w a t e r T B T c o n c e n t r a t i o n s a t these sites c a n b e c a t e g o r i z e d as u n c o n t a m i n a t e d ( < 3 n g l - t ) o r lightly c o n t a m i n a t e d ( 3 - 2 0 n g 1 - t ) u s i n g the criteria o f D o w s o n et al. (1992).
T h e d e s i g n o f this p r e l i m i n a r y s u r v e y h a s u n a v o i d a b l e limitations which should be noted. First, the lack of s a m p l e r e p l i c a t i o n , i n c o n c e r t w i t h the l o w c o n c e n t r a t i o n s e n c o u n t e r e d , does n o t a l l o w m e a n i n g f u l c o n 803
Marine Pollution Bulletin sideration o f the a p p a r e n t geographic variation. Samples were taken late in the b o a t i n g season when m u c h o f the T B T in b o a t paint applied in the spring m a y have leached out. Studies in other regions suggest that o r g a n o t i n levels in the water and biota tend to be higher earlier in the s u m m e r (Hall et al., 1987; Page and Widdows, 1991). T h e sampling p r o g r a m avoided the interior o f m a r i n a s a n d dense m o o r i n g fields which would have u n d o u b t e d l y yielded higher water c o l u m n concentrations. In addition, tidal and temporal variations have a p r o n o u n c e d effect on water c o l u m n T B T concentrations. Previous investigators have noted variations in T B T c o n c e n t r a t i o n by a factor o f 2 (Cleary, 1991) to perhaps 20 (Clavell et al., 1986) over a tidal cycle. H u g g e t t et aL (1986) measured concentrations varying by an order o f m a g n i t u d e at a single site in a week's period. Clearly, future surveys in the G u l f o f Maine need to take into a c c o u n t the seasonal a n d tidal dynamics o f the region. In conclusion, f o u r years after the use o f T B T on vessels < 25 m was b a n n e d in the State o f Maine, T B T and its d e g r a d a t i o n products, D B T and M B T , were detected at m o s t o f the estuaries sampled in the midcoast Maine region o f the G u l f o f Maine. Concentrations were low relative to those reported f r o m crowded marinas a n d boatyards. Considering the high spatial and temporal variability o f seawater T B T concentrations, and its affinity for concentrating in the surface microlayer (Cleary a n d Stebbings, 1987), m o r e detailed surveys o f selected e m b a y m e n t s are indicated. Such surveys should be designed to u n c o v e r possible sediment reserviors f r o m which o r g a n o t i n s m a y be remobilized (Unger et al., 1988). This research was supported in part by the Kennebec Area Research Endowment. We are grateful to the Maine Maritime Academy for the loan of the R/V Panthalass. Todd LaJeunesse, Jim Kulpa, Jed Goldstone and Bill Wilson assisted with the field program. David Page and Christopher Heinig provided expert advice on technical aspects and resource species. Ellen Travelstead supervized the organotin analyses of environmental samples. The comments of an anonymous reviewer are gratefully acknowledged. Alzieu, C., Heral, T., Thiband, Y. and Dardignac, M. T. (1982) Influence des peintures antisalissures sur la calcification de la coquille de l'huiture Crassostrea gigas. Rev. Tray. Inst. Peches Merit. 45, 101-116.
804
Alzieu, C., SanJuan, J., Michel, P., Borel, M. and Dreno, J. P. (1989) Monitoring and assessment of butyltins in Atlantic coastal waters. Marine Pollution Bulletin 20, 22-26. Beaumont, A. R. and Budd, M. D. (1984) High mortality of the larvae of the common mussel at low concentrations of tributyltin. Marine Pollution Bulletin 15, 402-405. Bryan, G. W. and Gibbs, P. E. (1991) Impact of low concentrations of TBT on marine organisms: A review. In Metal Ecotoxicity: Concepts and Applications, eds M. C. Newman and A. W. Mclntosh, pp. 323-361. Inc. Ann Arbor, Boca Raton, Boston. Bryan, G. W., Gibbs, P. E., Huggett, R. J., Curtis, L. A., Bailey, D. S. and Dauer, D. E. (1989) Effects of tributyltin pollution on the mud snail, llyanassa obsoleta, from the York River and Sarah Creek, Chesapeake Bay. Marine Pollution Bulletin 20, 458-462. Clavell, C., Seligman, P. F. and Stang, P. M. (1986) Automated analysis of organotin compounds: a method for monitoring butyltins in the marine environment. In Proc. Oceans '86 Organotin Symposium, ed. M. A. Champ, pp. 1152-1154. Institute of Electrical and Electronic Engineers, New York, USA. Cleary, J. J. (1991) Organotin in the marine surface microlayer and subsurface waters of South-west England: Relation to toxicity thresholds and the UK environmental quality standard. Marine Environmental Research 32, 213-222. Cleary, J. J. and Stebbings, R. D. (1987) Organotin in the surface microlayer and subsurface waters of southwest England. Marine Pollution Bulletin 18, 238-246. Dowson, P. H., Bubb, J. M. and Lester, J. N. (1992) Organotin distribution in sediments and waters of selected east coast estuaries in the UK. Marine Pollution Bulletin 24, 492-498. Gibbs, P. E., Pascoe, P. L. and Burt, G. R. (1988) Sex change in the female dog-whelk, Nucella lapillus, induced by tributyltin from antifouling paints. Journal of Marine Biology Association UK 68, 715-731. Hall, L. W., Lenkevich, M. J., Hall, W. S., Pinkney, A. E. and Bushong, S. J. (1987) Evaluation of butyltin compounds in Maryland waters of Chesapeake Bay. Marine Pollution Bulletin 18, 78-83. Huggett, R. J., Unger, M. A. and Westbrook, D. J. (1986) Organotin concentrations in the southern Chesapeake Bay. In Oceans "86 Proceedings, International Organotin Symposium, Vol. 4, pp. 12621265. Institute of Electrical and Electronic Engineers, New York. Huggett, R. J., Unger, M. A., Seligman, P. F. and Valkirs, A. O. (1992) The marine biocide Tributyltin: Assessing and managing environmental risks. Environmental Science and Technology 26, 232237. Page, D. S. and Widdows, J. (1991) Temporal and spatial Variation in levels of alkyltins in mussel tissues: A toxicological interpretation of field data. Marine Environmental Research 32, ! 13-129. Unger, M. A., Maclntyre, W. G., Grcaves, J. and Huggett, R. J. (1986) GC determination of butyltins in natural waters by flame photometric detection of hexyl derivatives with mass spectrometric confirmation. Chemosphere 15, 461-470. Unger, M. A., Maclntyre, W. G. and Huggett, R. J. (1988) Sorption behavior of tributyltin on estuarine and freshwater sediments. Environmental Toxicology and Chemistry 7, 907-915. Waite, M. E., Waldock, M. J., Thain, J. E., Smith, D. J. and Milton, S. M. (1991) Reductions in TBT concentrations in UK estuaries following legislation in 1986 and 1987. Marine Environmental Research 32, 89-111.