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Marine Pollution Bulletin 46 (2003) 401–409
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Assessment of organotin contamination in marine sediments
and biota from the Gulf and adjacent region
Stephen J. de Mora *, Scott W. Fowler, Roberto Cassi, Imma Tolosa
International Atomic Energy Agency, Marine Environment Laboratory 4, Quai Antoine 1er BP 800 Monaco, MC 98012, Monaco
Abstract
Butyltin species were measured in sediments from coastal locations in the Gulf and Gulf of Oman. Both butyltin and phenyltin
species were measured in biota samples from four countries in this region. With tributyltin (TBT) concentrations up to 60 ng Sn g1 ,
some sediments could be classified as contaminated (i.e. TBT > 1:3 ng Sn g1 ), namely Dukhan (Qatar), the BAPCO industrial
complex and Askar (Bahrain), and Hilf and the Raysut Port Area (Oman). Higher concentrations of total butyltins were found in
oysters relative to fish, but ranging from 6.5 to 488 ng Sn g1 dry weight they are nonetheless relatively low. Diphenyltin and triphenyltin were found in some fish and bivalves from the Gulf, but not in biota from the Gulf of Oman. The environmental levels of
organotin species are comparatively low by global standards and pose no immediate public health problems.
Ó 2003 Elsevier Science Ltd. All rights reserved.
Keywords: Organotin; TBT; Oman; Qatar; Bahrain; United Arab Emirates
1. Introduction
Organotin compounds exhibit varying degrees of
toxicity towards a broad range of organisms and accordingly have seen widespread applications as biocides
(Blunden and Evans, 1990). Triphenyltin (TPhT) compounds, found in some marine paint formulations, have
been widely utilised in agriculture as fungicides and insecticides. Tributyltin (TBT) compounds have been used
most extensively as the main biocide in marine antifouling paints. Organotin-based paints have seen service
on boats of all sizes, from small yachts to supertankers, thereby ensuring the global dispersion of TBT
throughout the marine environment, from the coastal
zone to the open ocean. These compounds are persistent
in the marine environment owing to their slow degradation rates and consistent flux (Michel and Averty,
1999; Stewart and de Mora, 1990).
TBT accumulates in a variety of marine organisms,
from plankton and fish to various marine birds and
mammals (Alzieu, 1996; Cooney, 1995; Iwata et al.,
1997). Numerous deleterious biological effects of TBT
on non-target organisms have been observed. The most
*
Corresponding author. Tel.: +377-97977236; fax: +377-97977276.
E-mail address: [email protected] (S.J. de Mora).
obvious manifestations of TBT contamination have
been shell deformation in Pacific oysters (Alzieu, 1996)
and the development of imposex (i.e. the imposition of
male sex organs on females) in marine gastropods
(Gibbs and Bryan, 1996). The latter effect demonstrates
that TBT acts as an endocrine disrupter.
Although human toxicology of organotin compounds
is not fully resolved (Benson, 1997; World Health Organisation, 1990), there are real public health concerns
about these substances. One study from Poland has reported measurable butyltin concentrations in human
liver, presumably due to seafood consumption (Kannan
and Falandysz, 1997). Clams from three sites in Coos
Bay estuary (Oregon, USA) contained TBT levels
ranging from 168 to 457 ng g1 , which were considered
sufficiently high for health authorities to issue a shellfish
consumption advisory in 1995 (Elgethun et al., 2000).
Furthermore, dietary studies in Taiwan indicated that
TBT levels in oysters posed a significant potential threat
to human health for fishermen in coastal areas (Chien
et al., 2002).
Organotin compounds are toxic and persistent, and
have been found throughout the marine environment.
Sediments provide a valuable means to assess contamination and given the public health concerns, seafood
analyses are prudent. Although there have been organotin investigations throughout the world (Champ
0025-326X/03/$ - see front matter Ó 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0025-326X(02)00481-2
402
S.J. de Mora et al. / Marine Pollution Bulletin 46 (2003) 401–409
and Seligman, 1996; de Mora, 1996), there are very few
data for the marine environment of the Middle East.
TBT was investigated in sediments from Bahrain (Hasan
and Juma, 1992) and various organotin species have
been measured in fish from the Gulf (Watanabe et al.,
1998). No studies have been reported for bivalves in the
region, and there are no data at all for organotin distributions in the Gulf of Oman.
The Gulf and Gulf of Oman comprise a special marine environment that merits close scrutiny for a number
of reasons. The region has marine ecosystems that are
relative fragile. Given that ambient water temperature
tends to be very high, many marine organisms are
functioning close to their limits of temperature tolerance. Thus, many organisms are sensitive to additional
stresses, as might arise from organotin contamination.
The Gulf, an enclosed sea, also has quite dense shipping
owing to the large number of oil tankers that transit the
region. Thus, a coastal pollution survey was conducted
to assess organotin contamination in sediments and
biota. This paper describes a survey of organotin compounds, notably butyltin and phenyltin substances, in
the coastal zone of Bahrain, Qatar and the United Arab
Emirates, together with the first such data from the Gulf
of Oman.
Fig. 1. Location of sampling sites in the RSA.
dorsal muscle from a single individual was dissected for
the sample. In some cases, liver tissue was also removed
and prepared for analysis. All biological samples were
stored frozen ()18 °C) in glass bottles until subsequently
analysed in Monaco.
2.2. Sample preparation
2. Materials and methods
2.1. Sample collection
Marine sediment and biota samples were collected as
part of a collaborative IAEA/ROPME 1 contaminant
screening project. Material was obtained during the
following three missions to the ROPME Sea Area
(RSA), which comprises the Gulf and the Gulf of Oman:
Qatar and the United Arab Emirates (March 24–April
4, 2000); Bahrain (November 23–25, 2000) and Oman
(July 27–August 1, 2001). Sediment sampling sites are
shown on a map of the RSA (Fig. 1). Details of dates,
locations and sample types are given in Tables 1 and 2.
In general, all sampling procedures were carried out
according to internationally recognised guidelines
(UNEP, 1991). Surface sediments (top 2 cm) were
collected directly into Teflon jars and then stored deepfrozen at )18 °C until analysed. Pearl oysters, rock
oysters, rock scallops, and barnacles were collected by
hand at low tide or by scuba diving. The soft parts from
1–15 individuals were dissected and drained of excess
liquid prior to storage. Different species of fish, caught
by local fishermen using nets or hand-line, were immediately returned to the laboratory and 100–300 g of
1
ROPME stands for Regional Organisation for the Protection of
the Marine Environment.
Sediment samples were freeze-dried for several days
and then sieved through a pre-cleaned 250 lm stainless
steel sieve to remove bits of shell and other debris. Organotin compounds were extracted from sediments,
using approximately 3 g aliquots, by shaking with 10 mL
concentrated acetic acid for 30 min (Astruc et al., 1992).
The slurry was centrifuged and filtered through a
Whatman filter using organotin-free seawater as a rinse.
Finally, sodium acetate buffer and ammonia were added
to stabilise the pH at 5–6. The samples were simultaneously derivatised and extracted using 500 ll of sodium
tetraethylborate (NaBEt4 ) and 5 ml of n-hexane. The
mixture was shaken for 10 min and the organic phase
was recovered following phase separation. A second
extraction with 5 ml of n-hexane was repeated and the
organic phase recovered and combined with the first
one. The extracts were then dried with pre-cleaned sodium sulfate and concentrated under a gentle stream of
pure nitrogen. Sulfur, a potential interferent during
subsequent gas chromatography, was removed using a
few small drops of elemental mercury.
Using approximately 0.5 g aliquots of freeze-dried
tissue, samples were solubilised in 10 ml tetramethylammonium hydroxide under agitation in an ultrasonic
bath at 50 °C for 1.5 h (Cassi et al., 2002). Upon complete dissolution of tissues, a buffer and acetic acid were
added to stabilise the pH at approximately 5–6. The
samples were simultaneously derivatised and extracted
S.J. de Mora et al. / Marine Pollution Bulletin 46 (2003) 401–409
403
Table 1
Location of sediment samples from Qatar, UAE, Bahrain and Oman
Station
Date
Location
1
2
3
4
5
28/3/00
29/3/00
29/3/00
30/3/00
30/3/00
24°56.3980 N,
25°21.0690 N,
25°20.2570 N,
25°47.0000 N,
25°37.4270 N,
51°37.7090 E
50°45.7180 E
51°34.4560 E
51°35.7750 E
51°32.8890 E
6
7
8
9
10
1/4/00
1/4/00
2/4/00
2/4/00
4/4/00
25°06.9910 N,
24°27.9570 N,
24°06.2000 N,
24°09.8420 N,
25°28.9770 N,
55°09.1150 E
54°18.2940 E
53°29.2070 E
52°38.8870 E
56°21.9400 E
11
4/4/00
25°28.7210 N, 56°21.7700 E
Askar
Off BAPCO Refinery
Jasra
North of Meridien Hotel
12
13
14
15
23/11/00
23/11/00
25/11/00
25/11/00
26°03.1020 N,
26°06.1380 N,
26°11.0980 N,
26°16.0560 N,
Mina Al Fahal (PDO Beach)
Ras Al Hamra
Ras Al Yei (Masirah east coast)
Hilf (Masirah west coast)
Mughsayl (beach)
Raysut Port Area (east beach)
Mirbat
Al Sawadi
16
17
18
19
20
21
22
23
27/7/01
27/7/01
28/7/01
29/7/01
30/7/01
31/7/01
31/7/01
01/8/01
23°37.9780 N, 58°30.6930 E
23°38.3630 N, 58°29.4950 E
20°31.3480 N, 58°57.0740 E
20°38.1030 N, 58°51.8130 E
16°52.9560 N, 53°47.6050 E
16°59.00 N, 54°01.00 E
16°58.500 N, 54°41.500 E
23°47.2600 N, 57°47.6330 E
Qatar
Umm Said
Dukhan
Doha
Ras Laffan
Ras Al Nouf
UAE
Jebel Ali
Abu Dhabi
Al Marfa
Al Ruweis (Al Dhannah)
Akkah Head, ‘‘Three Rocks’’ north of
Bidya
Akkah Beach, South of ‘‘Three Rocks’’
Bahrain
Oman
using 1000 ll of sodium tetraethylborate (NaBEt4 ) and
5 ml of n-hexane. The samples were shaken for 10 min,
then centrifuged at 5000 rpm for 15 min at 0 °C. The
organic phase was recovered and a second extraction
with 5 ml of n-hexane was performed followed by centrifugation. The organic phase was recovered and combined with the first one, and the extracts were then dried
with pre-cleaned sodium sulfate and concentrated under
a gentle stream of pure nitrogen.
Clean-up of all samples was completed using solid
phase extraction cartridges filled with 1 g of florisil and
eluted with 10 ml of n-hexane. The purified samples were
then concentrated with a gentle stream of pure nitrogen
prior to analysis by gas chromatography.
2.3. Organotin determinations
The organotin compounds were determined by capillary gas chromatography with a flame photometric
detector (cGC-FPD) at k ¼ 610 nm using an Hewlett
Packard HP5890. The detector and splitless injector
were maintained at 250 °C. Separations were carried out
on a HP-5 column (30 m 0:25 mm i:d: 0:25 lm film
thickness) under a helium flow rate of 1.3 ml min1 . The
temperature programme was 60 °C for 2 min, 60 °C to
270 °C at 6 °C min1 , and 270 °C for 20 min. Under
such conditions, the following organotin species were
resolved: monobutyltin (MBT), dibutyltin (DBT), TBT,
diphenyltin (DPhT) and TPhT.
Site no.
50°37.9590 E
50°37.7730 E
50°26.5230 E
50°31.4230 E
A quality control system based on three internal
standards was adopted (Cassi et al., 2002). Tripropyltin
was used to indicate the derivatisation reaction efficiency, and all the chromatographic peak areas were
normalised to that of tripropyltin. Tetraoctyltin was
used to check the overall solvent extraction efficiency.
Both internal standards were spiked just prior to
leaching. Tetrabutyltin, spiked in all samples prior to
injection, was used as a GC-internal standard to quantify the recoveries of both internal standards. Appropriate blanks were analysed with each batch of samples
and, in addition, reference materials were determined
simultaneously. BCR-462 (coastal sediment) was used
for sediment samples, while for biological samples BCR477 (mussel tissue) and NIES-12 (fish tissue) were
quantified.
The detection limit for organotin analyses, based on a
typical instrumental signal-to-noise ratio of 3:1, varies
somewhat between samples. These variations are real
and depend on the sample weight, the final volume of
the extract, and the recovery efficiency of the internal
standard because the response factor for each compound is normalized to the response of the internal
standard. The detection limits (ng Sn g1 dry weight) for
organotin species in sediments were MBT 0.12–0.53,
DBT 0.06–0.39, and TBT 0.06–0.39. In biota, the detection limits (ng Sn g1 dry weight) were MBT 0.57–5.5,
DBT 0.56–5.1, TBT 0.8–4.0, DPhT 1.4–8.3 and TPhT
0.59–6.2.
404
S.J. de Mora et al. / Marine Pollution Bulletin 46 (2003) 401–409
Table 2
Location and types of biota samples from Qatar, UAE, Bahrain and Oman
Qatar
Location
Fish/bivalve
Al Khawr
Epinephelus coioides (‘‘Hamoor’’ or
Orange-spotted grouper)
’’
’’
Lethrinus nebulosus (‘‘Sheiry’’ or
Spangled emperor)
Umm Said
Doha
Al Dakhira (North of Al Khawr)
UAE
Jebel Ali (buoy #7)
Abu Dhabi (off artificial island in
front of Sheraton Hotel)
Abu Dhabi (off Silos near port
entrance)
Al Marfa
Al Ruweis (Al Dhannah)
Akkah Head ‘‘Three Rocks’’
north of Bidya
Akkah Beach South of ‘‘Three
Rocks’’
Bahrain
Askar
North of Meridien Hotel
Badaiya
Fasht Al Adham
Oman
Ras Al Hamra
Quriyat
Ras Al Yei
Hilf
Mirbat
Raysut Port Area
Sagar
Al Sawadi
Mina Al Fahal (PDO Beach)
No. of samples
Weight (kg)
Length (cm)
1
1.7
50
1
1
3
2.2
1.7
0.1
55
49
Pinctada radiata (Pearl oyster)
Pinna muricata (Pen shell)
Spondylus sp. (Rock scallop)
6
3
5
Pinctada radiata (Pearl oyster)
6
Epinephelus coioides (‘‘Hamoor’’ or
Orange-spotted grouper)
Lethrinus nebulosus (‘‘Sheiry’’ or
Spangled emperor)
Epinephelus coioides (‘‘Hamoor’’ or
Orange-spotted grouper)
Lethrinus nebulosus (‘‘Sheiry’’ or
Spangled emperor)
Pinctada radiata (Pearl oyster)
1
4.7
69
1
1.7
49
1
2.8
60
1
1.7
49
Saccostrea cucullata (Rock oyster)
1
19
15
Pinctada radiata (Pearl oyster)
Pinctada radiata (Pearl oyster)
Epinephelus coioides (‘‘Hamoor’’ or
Orange-spotted grouper)
’’
’’
’’
1
8
1
1.6
48
1
1
1
1.15
1.26
1.03
47
45
42
Saccostrea cucullata (Rock oyster)
(1) Epinephelus coioides (‘‘Hamoor’’
or Orange-spotted grouper)
(2) ’’
Saccostrea cucullata (Rock oyster)
’’
’’
Lethrinus nebulosus (‘‘Sheiry’’ or
Spangled emperor)
Lethrinus nebulosus (‘‘Sheiry’’ or
Spangled emperor)
Saccostrea cucullata (Rock oyster)
Balanus trigonus (Barnacles)
15
1
1.8
–
1.8
–
1.55
–
1.45
–
3. Results and discussion
The concentrations of butyltin compounds in sediments from the RSA are shown in Table 3. In the UAE,
no organotin was detected other than a small amount
(1.08 ng Sn g1 ) of MBT found at the Jebel Ali port
complex. Similarly, no butyltin was measured at one site
in Qatar (Ras Al Nouf), and only MBT was observed at
two other locations (Doha and Ras Laffan). In contrast,
all three species were measurable at Umm Said and
Dukhan. Dukhan was the only location that could be
considered contaminated with respect to TBT (i.e.
1
15
15
15
1
1
15
2
TBT > 1:3 ng Sn g1 ) according to the classification
scheme of Dowson et al. (1993). As TBT degrades only
slowly in marine sediments (Stewart and de Mora,
1990), the high relative percentage of MBT at all sites
other than Dukhan indicates that there has been little
recent input of TBT into the marine environment of the
UAE and Qatar.
More variability was observed for organotin distributions in both Bahrain and Oman. There were two sites
in Bahrain (Jasra and North of Meridien Hotel) and
three in Oman (Al Sawadi, Mina Al Fahal and Mughsayl) without measurable butyltin levels. This observa-
S.J. de Mora et al. / Marine Pollution Bulletin 46 (2003) 401–409
405
Table 3
Organotin concentrations (ng Sn g1 dry weight) in marine sediments from UAE, Qatar, Bahrain and Oman
UAE
Qatar
Bahrain
Oman
Compound
Jebel Ali
Abu Dhabi
Al Marfa
Al Ruweis
Akkah Head
‘‘ThreeRocks’’
MBT
DBT
TBT
1.08
<0.10
<0.11
<0.17
<0.11
<0.12
<0.14
<0.08
<0.09
<0.12
<0.07
<0.08
<0.16
<0.10
<0.11
Compound
Umm Said
Doha
Ras Laffan
MBT
DBT
TBT
3.1
1.4
0.8
1.3
0.71
1.7
1.5
<0.14
<0.14
0.74
<0.06
<0.06
Compound
Askar
BAPCO
Jasra
North of
Meridien
Hotel
MBT
DBT
TBT
6.3
2.4
1.8
10
30
40
<0.53
<0.39
<0.39
<0.53
<0.39
<0.39
Compound
Al Sawadi
Mina Al
Fahal
Ras Al Yei
Hilf
Raysut Port
Area
Mughsayl
MBT
DBT
TBT
<0.3
<0.2
<0.2
<0.2
<0.1
<0.1
0.9
<0.2
<0.2
9.7
2.0
60
<0.3
<0.2
3.3
<0.3
<0.2
<0.2
Dukhan
tion for Mina Al Fahal, Oman, was surprising given that
this location was very close to the oil terminal. In contrast, all three butyltin species were detected in sediments off the BAPCO industrial complex and at Askar
in Bahrain. The comparatively high amounts of TBT
near BAPCO reflect the importance of shipping at this
site near the refinery. In Oman, only TBT was detected
(3.3 ng Sn g1 dry weight) at the Raysut Port Area in
Oman, indicative of recent TBT inputs. Relatively high
organotin concentrations were observed at Hilf on the
west coast of Masirah Island (e.g. 60 ng Sn g1 dry
weight for TBT). The source of these organotin compounds is not immediately apparent. Hilf does have a
ferry terminal for the small vessels that service the island
and several fishing boats are based in the port. Both
BAPCO in Bahrain and at Hilf in Oman are classified as
moderately contaminated (Dowson et al., 1993). Apart
from these two contaminated sites, the relatively high
percentage of MBT in most sediments suggests that
there has been little recent input.
The only published data for TBT in sediments in the
RSA are from Bahrain (Hasan and Juma, 1992). They
reported TBT concentrations in sediments in the early
1990s ranging from 128 to 1930 ng Sn g1 , i.e. one to two
orders of magnitude higher than the 40 and 60 ng Sn g1
dry weight measured at BAPCO (Bahrain) and Hilf
(Oman), respectively. This apparent sharp decrease in
concentration over the last decade may reflect changing
TBT usage during these past years, particularly with
respect to Japanese vessels.
Akkah Beach south of
‘‘Three Rocks’’
<0.20
<0.13
<0.13
Ras Al Nouf
<0.23
<0.14
<0.15
Concentrations of butyltin compounds were very low
in most fish samples and in many cases can only be reported as Ôless thanÕ values (Table 4). Exceptions were
8.8 and 20 ng Sn g1 dry weight for TBT in muscle of
two orange-spotted groupers from Badaiya, Bahrain,
and 6.4 and 5.9 ng Sn g1 dry weight in the same species
from Umm Said and Doha, respectively, in Qatar.
Likewise, two grouper from Quriyat in Oman contained
9.3 and 18 ng Sn g1 dry weight for TBT in their muscle
tissue. Overall, the total butyltin concentrations in
muscle tissue, ranging from approximately 1.2–30
ng Sn g1 dry weight (0.3–7.0 ng Sn g1 wet weight), are
comparable to other data reported for various fish species in the RSA (Watanabe et al., 1998). However, these
concentrations are quite low when compared to fish
from other areas. For example, bluefin tuna from the
Mediterranean have average butyltin concentrations of
62 ng g1 wet weight (range 16–230 ng g1 wet weight) in
muscle (Kannan et al., 1996). Fish from coastal areas in
the North Sea and Baltic Sea contain much higher
concentrations in muscle, namely 293 21 ng g1 wet
weight and 14–455 ng g1 wet weight, respectively
(Kannan and Falandysz, 1997; Shawky and Emons,
1998). Fewer liver samples from fish in the RSA were
analysed and the results were quite variable. All three
butyltin species were measurable in 3 of the 5 liver
samples investigated, a much greater frequency than for
the muscle and indicative of the enhanced rate of debutylation in this organ relative to muscle. Nevertheless,
TBT and total butyltin concentrations were low in
406
S.J. de Mora et al. / Marine Pollution Bulletin 46 (2003) 401–409
Table 4
Organotin concentrations (ng Sn g1 dry weight) in fish from Qatar, UAE, Bahrain and Oman
UAE
Qatar
Bahrain
Oman
Compound
Al Marfa
Orange-spotted
grouper
Muscle
Al Marfa
Spangled
emperor
Muscle
Al Dhannah
Spangled
emperor
Muscle
Al Dhannah
Orange-spotted
grouper
Muscle
MBT
DBT
TBT
DPhT
TPhT
<3.9
<3.7
<3.0
<6.6
<4.0
<3.9
<3.7
<3.0
<6.6
<4.0
<1.3
<1.3
1.2
<2.4
2.4
<0.9
<1.0
<0.8
<1.5
2.5
Compound
Al Khawr
Orange-spotted
grouper
Muscle
Umm Said
Orange-spotted
grouper
Muscle
Doha
Orange-spotted
grouper
Muscle
Al Dakhira
Spangled
emperor
Muscle
MBT
DBT
TBT
DPhT
TPhT
<3.1
<3.2
<2.8
7.6
8.3
<3.6
<3.7
6.4
<5.2
4.9
<5.5
<5.1
5.9
<8.3
<6.2
<4.6
<4.7
<4.0
<8.3
<5.9
Compound
Badaiya
Orange-spotted
grouper (1.6 kg)
Muscle
Liver
Badaiya
Orange-spotted
grouper (1.15 kg)
Muscle
Fasht Al Adham
Orange-spotted
grouper (1.26 kg)
Muscle
Liver
Fasht Al Adham
Orange-spotted
grouper (1.03 kg)
Muscle
Liver
MBT
DBT
TBT
DPhT
TPhT
<0.57
<0.56
8.8
<1.5
3.9
<0.57
<0.56
20
<1.5
<0.59
<1.0
<1.8
<0.82
<2.1
<1.3
<0.57
<0.56
1.2
<1.5
<0.59
<0.57
<0.56
2.0
<1.5
<0.59
Compound
Quriyat
Quriyat
Sagar
Orange-spotted grouper (1)
Orange-spotted grouper (2)
Muscle
Liver
Muscle
Liver
Raysut port
area
Spangled
emperor
Muscle
Spangled
emperor
Muscle
<2.4
<2.3
9.3
<2.3
<2.1
11
13
7.5
<1.9
<1.7
6.7
5.1
18
<2.2
<2.0
9.2
14
8.5
<1.6
<1.5
<4.0
<4.0
<2.7
<3.9
<3.6
6.3
<3.1
<2.1
<3.1
<2.8
MBT
DBT
TBT
DPhT
TPhT
40
14
4.4
<2.1
<1.3
comparison to studies conducted elsewhere; for example
in Sri Lanka, total butyltin concentrations in fish liver
were as high as 11–38 lg g1 wet weight (Guruge and
Tanabe, 2001).
Concentrations of organotin compounds were much
higher in bivalves than in fish, with levels of TBT, DBT
and MBT reaching 196, 229 and 63 ng Sn g1 dry
weight, respectively, in pearl oysters from Abu Dhabi
(Table 5). These bivalves also displayed maximum levels
for other metals and organic contaminants (unpublished data). Likewise, pearl oysters collected at Askar,
relatively near to the BAPCO industrial complex in
Bahrain, also contained a relatively high amount of
TBT (150 ng Sn g1 dry weight). The high TBT=
ðMBT þ DBTÞ ratio of 3.9 indicates the likelihood of
fresh inputs of TBT near this location. Rock scallops
<1.0
<1.8
<0.82
<2.1
<1.3
from Abu Dhabi also displayed an elevated concentration of TBT (110 ng Sn g1 dry weight), however, the
corresponding DBT levels (24 ng Sn g1 dry weight)
were an order of magnitude less than were found in the
pearl oysters from the same site. Both species were
collected in areas near the port of Abu Dhabi where
small and large boat traffic is common. This striking
difference in DBT concentrations could reflect differing
debutylation efficiencies in the two species of bivalves.
TBT concentrations in rock oysters from the Gulf of
Oman were all relatively low except in those originating
from Akkah Beach, UAE (25 ng Sn g1 dry weight) and
Hilf on Masirah Island in southern Oman (176 ng Sn g1
dry weight). Both these locations are fairly remote. With
respect to the high TBT concentration in oysters from
Hilf, they closely reflect the high TBT levels measured in
S.J. de Mora et al. / Marine Pollution Bulletin 46 (2003) 401–409
407
Table 5
Organotin concentrations (ng Sn g1 dry weight) in bivalves from UAE, Bahrain and Oman
UAE
Bahrain
Oman
Compound
Jebel Ali
Abu Dhabi
Abu Dhabi
Pearl oysters
Akkah Head
‘‘Three Rocks’’
Pearl oysters
Pearl oysters
Rock scallops
MBT
DBT
TBT
DPhT
TPhT
<3.6
11
23
<4.8
<3.4
4.6
24
110
<3.8
16
Compound
Askar
Pearl oysters
North of Meridien
Hotel
Pearl oysters
MBT
DBT
TBT
DPhT
TPhT
5.0
33
150
<1.5
<0.59
<0.57
<0.56
20
<1.5
<0.59
Compound
Al Sawadi
Rock oysters
MBT
DBT
TBT
DPhT
TPhT
2.6
6.2
7.8
<1.6
<1.3
Rock oysters
63
229
196
<4.8
38
4.1
8.0
23
<2.7
<2.0
11
20
25
<2.5
<1.7
Ras Al Hamra
Rock oysters
Ras Al Yei
Rock oysters
Hilf
Rock oysters
Mirbat
Rock oysters
5.0
12
12
<1.6
<1.3
2.6
3.1
0.8
<1.4
<1.2
69
108
176
<1.5
<1.3
3.0
9.1
8.2
<2.0
<1.7
the surrounding sediments (Table 3) and clearly indicate
fairly fresh inputs of TBT at this location, presumably
due to boating activities at this minor port. Such TBT
concentrations (ranging from 0.8 to 176 ng Sn g1 dry
weight) are similar to those measured in Sydney rock
oysters from Australia (approximately 1–90 ng Sn g1
dry weight using a dry/wet ratio of 0.23) in 1991 following the banning of TBT usage (Batley et al., 1992).
Much higher concentrations have been measured in
oysters elsewhere, for example 0.13–0.62 lg Sn g1 dry
weight in Taiwan (Chien et al., 2002) and 0.10–1.80
lg Sn g1 dry weight in Korea (Hwang et al., 1999).
Concentrations of total butyltins in oysters from the
RSA ranged approximately two orders of magnitude
from 6.5 to 488 ng Sn g1 dry weight (Table 5). If the two
highest concentrations at Abu Dhabi and Hilf are excluded, the range (6.5–188 ng g1 dry weight) is narrowed
considerably. These concentrations can be compared with
those from the US. Mussel Watch Programme in which
total butyltin levels from the east, west and Gulf coasts
ranged from 50 to 770, 200 to 2820, and <5 to 1677
ng Sn g1 dry weight, respectively (Wade et al., 1991;
Wade et al., 1988). Thus, considering the range of butyltin
concentrations in oysters from a variety of coastal sites in
various regions of the world (Alzieu, 1996), the levels in
oysters and other bivalves from the RSA generally fall
in the lower end of the range of typical concentrations.
Organotin species were also measured in barnacle
samples collected from the single buoy moorings (SBM)
Akkah Beach
Table 6
Organotin concentrations (ng Sn g1 dry weight) in barnacles from the
SBM at Mina Al Fahal, Oman
Compound
SBM-1
SBM-2
MBT
DBT
TBT
DPhT
TPhT
31
57
85
<4.0
<2.0
6.6
24
56
<3.1
<1.6
at the oil terminal Mina Al Fahal in Oman (Table 6).
TBT concentrations, 85 and 56 ng Sn g1 dry weight,
seemed high, but there are no data in the literature for
comparison. The predominance of TBT relative to its
breakdown products of DBT and MBT indicates recent
input, as might be expected at an oil terminal. However
as noted previously, there was no apparent accumulation of organotin compounds in adjacent sediments
(Table 3).
Both DPhT and TPhT were also analysed in all biota
samples (Tables 4–6). Whereas phenyltins were not detected in any sample from Oman, quantifiable amounts
were observed in fish samples from the UAE, Qatar, and
Bahrain. Notably, DPhT (7.6 ng Sn g1 ) and TPhT (8.3
ng Sn g1 ) were found in a grouper from Al Khawr,
Qatar, that had undetectable amounts of all three butyltin species. The low frequency of observations, with
TPhT detected in only 5 of 21 fish, contrasts with the
sole previous study in which phenyltins were found in 42
408
S.J. de Mora et al. / Marine Pollution Bulletin 46 (2003) 401–409
out of 55 fish samples (Watanabe et al., 1998). Also,
whereas that study found higher concentrations of
TPhT in liver than in the muscle, here phenyltin was not
detected in any liver sample. There are few other studies
for comparison. TPhT has been measured in the liver,
digestive tube and gills of red mullet from the Catalan
coast (Morcillo et al., 1997) and flatfish from Gdansk
Bay (Albalat et al., 2002), but unfortunately concentrations in muscle were not reported. TPhT concentrations in fish from Japan varied from undetectable
concentrations up to 0.130 lg g1 , as TPhT wet weight
(Harino et al., 2000; Harino et al., 1998). As a final note,
DPhT was detected in only one sample, namely grouper
muscle from Al Khawr in Qatar, suggesting that TPhT
degradation in fish muscle must proceed very slowly.
No phenyltin was detected in bivalves from the RSA
except for TPhT in one rock scallop sample (16
ng Sn g1 ) and one pearl oyster sample (38 ng Sn g1 )
from the UAE. These are the first phenyltin data reported for bivalves in the RSA and there are still few data
from other regions for comparison. TPhT was similarly
found in only a few of the mussel samples from the
Catalan coast (Morcillo et al., 1997), with concentrations
up to 311 ng Sn g1 dry weight, however, this compound
was not detected in mussels along the Polish coast (Albalat et al., 2002). TPhT concentrations as TPhT wet
weight in scallops and mussels from Japan were 0.24–9.8
and 0.04–0.18 lg g1 , respectively (Harino et al., 1998).
The distribution of phenyltin residues in fish and
bivalves shown here is clearly sporadic and differs
greatly from that of butyltin species. Whereas the butyltins are derived from the TBT in marine antifouling
paints and its degradation products, phenyltin compounds are used as biocides not only in marine paints
but also in agrochemicals (Blunden and Evans, 1990).
Markedly different explanations for the distribution of
butyltin and phenyltin species are found in the literature.
TPhT in fish from the Mediterranean (Morcillo and
Porte, 2000) and Baltic (Albalat et al., 2002) Seas was
deemed to originate from fungicide usage. On the other
hand, the positive correlation between TBT and TPhT
observed in mussels from Otsuchi Bay, Japan, was
readily explained as originating from marine antifoulant
usage in an adjacent shipyard (Harino et al., 1998).
Likewise, TPhT in mussels from Masnou, Spain, was
considered to be derived from local marina traffic
(Morcillo et al., 1997). It has already been suggested that
the TPhT in fish from the RSA is derived from marine
antifoulants on Japanese vessels that are not permitted
to use TBT (Watanabe et al., 1998). However, this
conclusion is not consistent with data reported here,
especially for the barnacles from the SBM at the oil
terminal of Mina Al Fahal in Oman (Table 6). Whereas
these barnacles contained quite high concentrations of
butyltin species, phenyltin species could not be detected.
Thus, agrochemicals are likely to have been the source
of phenyltins in the Gulf, although marine antifoulants
cannot be ruled out as a contributing factor, especially
in Abu Dhabi.
In summary, the environmental levels of organotins
found in coastal sediments from the RSA are relatively
low by global standards. Only a few sites can be described as TBT-contaminated. Similarly, the organotin
content of the marine biota is comparatively low. Based
on the limited information concerning the dangers to
public health from organotin compounds (Benson, 1997;
Penninks, 1993; World Health Organisation, 1990), organotin concentrations in edible fish and bivalves from
the four countries investigated here pose no immediate
public health problems.
Acknowledgements
This was a collaborative project between the IAEA
and ROPME, financially supported by both organisations. The IAEA Marine Environment Laboratory operates under agreement between the International
Atomic Energy Agency and the Government of the
Principality of Monaco. We acknowledge with gratitude
the logistic support received in each country: in Bahrain
from the Ministry of Housing, Municipalities & Environment; in Oman from the Ministry of Regional
Municipalities and Environment; in Qatar from the
Ministry of Municipal Affairs and Agriculture; and in
the UAE from the Federal Environment Agency. Finally, we thank Dr. Nahida Al-Majed for assistance
with sample collection in Bahrain and Oman, Dr. Barry
Jupp for providing the barnacle samples in Oman and
Mr. Jean Bartocci for assistance in the laboratory in
Monaco.
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