Chapter 10
Butyltin Compounds in Freshwater Ecosystems 1
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Bommanna G . Loganathan , Kurunthachalam Kannan , David A. Owen , and Kenneth S. Sajwan 1
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Department of Chemistry and Center for Reservoir Research, Murray State University, Murray, KY 42071 National Food Safety and Toxicology Center, Michigan State University, East Lansing, MI 48824 3Departmentof Biology and Life Sciences, Savannah State University, Savannah, GA 31404
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Widespread use of butyltin (BT) derivatives (mono-, di-, and tributyltin) in industrial, domestic and consumer products has resulted in contamination of freshwater ecosystems. Butyltins are ubiquitous in wastewater effluents around the world. This chapter provides background information on environmental contamination by butyltin compounds with reference to sources, bioaccumulation features, and persistence in freshwater ecosystems. Concentrations of butyltins in freshwater organisms collected from several locations in the United States and other countries are compiled and compared with those recently measured in sediment and mussel tissues collected from the lowermost Tennessee River and Kentucky Lake. A major source of butyltin compounds in freshwater ecosystems is wastewater treatment plant effluents. Butyltin compounds are moderately persistent in water with half -lives in the range of several days to several months depending on ecosystem characteristics. Butyltins persist in sediments for several years and accumulate in a variety of aquatic organisms including fish-eating water birds and aquatic mammals. Monitoring studies are needed to evaluate the sources and effects of butyltin compounds in freshwater organisms.
Tin is a soft, white, silvery metal that is insoluble i n water [1]. T i n can combine with carbon-containing materials to form organotin (OT) compounds. Depending on the number of organic moieties, O T compounds are classified as
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© 2001 American Chemical Society Lipnick et al.; Persistent, Bioaccumulative, and Toxic Chemicals I ACS Symposium Series; American Chemical Society: Washington, DC, 2000.
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135 mono-, di- tri and tetra-organotins. The first O T compound was synthesized as early as 1852 by Lowig (see Snoeij et al [2]). However, uses of OT compounds were not known until the systematic investigations by Van der Kerk and co-workers during the 1950s [3,4], The commercial uses of O T compounds have expanded rapidly during the last fifty years. Presently, tin is unsurpassed by any other metal in the number of its organic applications [5]. The annual world consumption of tin in all forms was about 200,000 tons in 1976, and of this total about 28,000 tons was in the form of O T compounds [6]. Due to the expansion of technical applications, the annual world production of O T compounds grew rapidly from 5000 tons in 1955 to 25,000 tons in 1975 [7], 35,000 tons in 1986 and 50,000 tons in 1992 [8]. The increasing annual usage of O T compounds, some of which are very toxic, attracted the attention of environmental health organizations in the 1970s. In particular, studies regarding environmental contamination and ecotoxicological effects of O T compounds have received serious attention after a tragic incident involving poisoning of 217 people and death of 100 people due to a drug that was sold in France for the treatment of staphylococcal skin infections. It was said to contain diethyltin diiodide, but the poisoning was most likely due to the contamination with triethyltin iodide [9,10]. The major O T compounds released into the environment are butyl-, phenyland octyltins. These O T compounds have been used as heat and light stabilizers in plastics and food packages, pesticides, paint and wood preservatives, marine antifouling agents, disinfectants and slime control in paper mills and as catalysts in the production of polyurethane foams and curing of silicone rubbers and epoxy resins [1]. Several aspects of the chemistry, applications and behavior of tin compounds have been reviewed by various researchers [6,11,12]. O f several OT compounds, tributyltin (TBT) has received considerable attention in the past decade due to its effect on aquatic organisms at relatively low concentrations (a few ng L ' levels). T B T was first used in antifouling paints in Europe between 1959 and 1961 [13]. Alzieu et al. [14,15] and Alzieu and Heral [16] were among the first to investigate the toxicity of T B T in 1980, reporting deleterious effects (shell thickening and abnormalities) in Pacific oysters (Crossostrea gigas). Bryan and coworkers [17,18] established a link between T B T contamination and the sterilization of certain neogastropods, which resulted in the decline of populations. Deleterious effects of T B T have been observed in microalgae, bivalve mollusks, polychaetes, crustaceans, and fish at concentrations as low as 10-100 ng L" [17,18]. A s a consequence, regulations on the use of TBT-based antifouling paints have been introduced in several countries since the late 1980s [12]. Despite a decrease in the T B T contamination in the aquatic environment after the regulations were introduced, concentrations persisted at levels considered chronically toxic to most susceptible organisms [19-21]. In addition, T B T is still used in vessels greater than 25 m long. Growing consumption of T B T lies in its use as a preservative for timber and wood, textiles, paper and leather. A small percentage of T B T also is used in dispersion paints and in a variety of other materials (e.g., P V C ) as protection against microbial or fungal attack [22]. 1
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Lipnick et al.; Persistent, Bioaccumulative, and Toxic Chemicals I ACS Symposium Series; American Chemical Society: Washington, DC, 2000.
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136 The uses of butyltin compounds are so diverse that they have been detected in a variety of aquatic matrices including sewage, sludge, sediments and water from both fresh water and marine systems. However, most studies have focused on the accumulation and toxic effects of butyltin compounds in coastal and marine environments [23-28], B T contamination in freshwater ecosystems such as rivers and lakes has not been examined in detail. For instance, imposex in gastropods has teen examined in marine waters but such studies have not been conducted in freshwaters. With increasing use of B T derivatives in industries located along the inland lakes and rivers, and in a variety of household products, it is important to monitor the concentrations of B T compounds in freshwater ecosystems. In this chapter, we discuss persistent, bioaccumulative and toxic potentials of butyltins in freshwater ecosystems. The differences in the partitioning behavior between freshwater and marine water systems are also discussed. Concentrations of butyltins in freshwater organisms collected from several locations in the U.S. are compiled and compared with those measured in sediment and mussel tissues collected from the lowermost Tennessee River and Kentucky Lake.
Sources of Butyltins in Freshwater Ecosystems Pioneering work of butyltin contaminations in freshwater systems was performed by Maguire and co-workers in Canada in the early 1980s (see Chau et al [29] for a recent report). Their studies focused on butyltins in water and sediment of various lakes and rivers in Canada. While butyltin contamination arising from antifouling paints released due to pleasure boating activities was found to be a major source in several locations, these compounds also were found in rivers where there was minimal or no boating activities. In fact, fouling of boat hulls in freshwater is a less serious problem compared with that in seawater [30]. This provided evidence for the occurrence of other sources of butyltins in the environment. Monobutyltin (MBT) and dibutyltin (DBT) are ubiquitous pollutants in municipal wastewaters which originate mainly from the leaching of P V C pipes containing these compounds as stabilizers [31]. Disposal of municipal wastewater thus contributes to butyltin contamination in receiving surface waters such as lakes or rivers. Input of D B T and T B T into surface waters from applications other than antifouling paint on vessels (i.e., use of T B T as a slimicide in the cooling water of a thermoelectric power plant) was first reported in Italy in the late 1980s [32]. Several studies have reported the occurrence of butyltin compounds in wastewaters. For example, concentrations of butyltins in raw wastewater in Zurich, Switzerland, on six sampling days ranged from 136 to 564, 127 to 1026 and 64 to 217 ng/L, respectively for M B T , D B T and T B T [33]. Water treatment processes removed butyltin compounds to a certain extent but not completely. M B T , D B T and T B T were removed at a rate of 62, 80 and 66%, respectively by sedimentation [33]. The effluent from the treatment plant in Zurich contained butyltins from 7 to 47 ng L" . The sludge contained M B T , D B T and T B T concentrations in the range of 0.1-0.97, 0.41-1.24 and 0.28-1.51 μg g* dry 1
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Lipnick et al.; Persistent, Bioaccumulative, and Toxic Chemicals I ACS Symposium Series; American Chemical Society: Washington, DC, 2000.
137 wt, respectively. Similarly, studies in Canada and Germany have shown the presence of butyltin compounds in wastewater effluents [34,35]. M B T concentration of up to 22 \x% L" was found in wastewater effluents in Canada. Presence of over hundred ng L ' concentrations of butyltin compounds in Ganges river waters in India also has been shown [36]. Studies describing the occurrence of butyltins in wastewater effluents in the U.S. are not available. Nevertheless, the above evidence suggests that butyltins are widespread contaminants in wastewater, which eventually enters into lakes or rivers. Occurrence of butyltin compounds in non-navigable areas in certain rivers [37] as well as in aquatic organisms of certain non-navigable rivers suggest the release of these compounds from wastewater [38]. Other sources of butyltin compounds in freshwater systems are the use of unregulated antifouling paints, use in timber protection, and use in industrial applications as biocides or catalysts. The contamination of riverine environments by butyltin compounds strongly indicates that the occurrence of butyltins in surface waters is widespread. 1
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Bioaccumillation of Butyltins in Freshwater Ecosystems Speciation and partitioning behavior of O T compounds can vary between seawater and freshwater due to the differences in salinity and hydrogen ion concentration (pH). Knowledge of aqueous phase chemical speciation can provide important insights into the bioavailability, bioaccumulation and toxicity of butyltins. Organotins undergo p H dependent hydrolysis when introduced into water [39]. While several studies have examined the behavior and fate of OT compounds in seawater, a few studies have examined their behavior in freshwaters. Cations are formed in water at pH
