Bioaccumulation, elimination and metabolism of triphenyltin chloride by early life stages of minnows Phoxinus phoxinus

Review of measured concentrations of triphenyltin compounds in marine ecosystems and meta-analysis of their risks to humans and the environment

The state of scientific knowledge regarding analytical methods, environmental fate, ecotoxicity and ecological risk of triphenyltin (TPT) compounds in marine ecosystems as well as their exposure and health hazard to humans was reviewed. Since the 1960s, TPT compounds have been commonly applied as biocides for diverse industrial and agricultural purposes. For instance, they are used as active ingredients in antifouling systems on marine vessels and mariculture facilities, and as fungicides in agriculture. Due to their intensive use, contamination of coastal waters by TPT and its products of transformation has become a worldwide problem. The proportion of quantified TPT to total phenyltin compounds in the marine environment provides evidence that TPT is photodegradable in water and sediment but resistant to biotransformation. Concentrations of TPT in marine biota are consistently greater than concentrations in water and sediment, which implies potential of TPT to bioaccumulate. TPT is toxic to both marine plants and animals. The predicted no effect concentration (PNEC) for TPT, as determined by use of the species sensitivity distribution approach, is 0.64 ng L(-1). In some parts of the world, concentrations of TPT in seawater exceed the PNEC, indicating that TPT can pose risks to marine life. Although there is negligible risk of TPT to average human consumers, TPT has been detected in blood of Finnish people and the concentration was greater in fishermen who ate more seafood. It is, therefore, advocated to initiate regular monitoring of TPT in blood and breast milk of populations that consume greater amounts of seafood.

Retinal Neuronal Cell is a Toxicological Target of Tributyltin in Developing Zebrafish

Organotins are among the most common marine pollutants in the world, as they are widely used as antifouling paint on ships and fishing nets. It has been reported that organotin preferentially accumulates in the central nervous system, especially in the retinal neurons of marine organisms including fish. In this study, we investigated the effects of waterborne tributyltin (TBT) on early-stage developing zebrafish (Danio rerio). Below the lethal concentrations, TBT specifically increased the number of apoptotic cells in the retina as well as some cells near trigeminal neurons, detected by terminal transferase-mediated nick-end-labeling staining. Apoptosis peaked at 60 hpf and decreased by 72 hpf, which was associated with macrophage accumulation. Furthermore, the effect of TBT was markedly inhibited by antioxidants, ascorbic acid or trolox. These results suggest that TBT preferentially induces apoptosis in the retinal neuron of developing zebrafish. Oxidative stress may be involved in this toxicological response.

Bioaccumulation of contaminants in fish

The term bioaccumulation is defined as uptake, storage, and accumulation of organic and inorganic contaminants by organisms from their environment. Bioaccumulation therefore results from complex interactions between various routes of uptake, excretion, passive release, and metabolization. For fish, the bioaccumulation process includes two routes of uptake: aqueous uptake of water-borne chemicals, and dietary uptake by ingestion of contaminated food particles. The contribution to bioaccumulation that results from aqueous exposure and is taken up by the gills is called bioconcentration. The contribution to bioaccumulation resulting from dietary exposure via uptake by intestinal mucosa is termed biomagnification. In both cases, important co-determinants for bioaccumulation are the various elimination mechanisms. This chapter presents a short historical survey of the problem of bioaccumulation with particular reference to fish and of the various approaches to study bioaccumulation. This is followed by an overview of our present knowledge about basic physico-chemical determinants that either increase or reduce the bioaccumulation potential of various chemicals, and about the physiological basis of gills, blood circulation and intestines, as far as they are crucial for our understanding of uptake and accumulation. Finally, selected quantitative data and modelings of bioaccumulation in fish will be discussed, with regard to such problems as the relative importance of aqueous and dietary uptake.

Bioaccumulation processes in ecosystems

The fate of environmental pollutants--the various isotopes of elements, and inorganic or organic compounds--is a fundamental aspect of ecology and ecotoxicology, and bioaccumulation is a phenomenon often discussed in this context. Human activities have drastically altered natural concentrations of many substances in the environment and added numerous new chemicals. An understanding of the processes of bioaccumulation is important for several reasons. 1) Bioaccumulation in organisms may enhance the persistence of industrial chemicals in the ecosystem as a whole, since they can be fixed in the tissues of organisms. 2) Stored chemicals are not exposed to direct physical, chemical, or biochemical degradation. 3) Stored chemicals can directly affect an individual's health. 4) Predators of those organisms that have bioaccumulated harmful substances may be endangered by food chain effects. While former theories on the processes of bioaccumulation focused on single aspects that affect the extent of accumulation (such as the trophic level within the food chain or the lipophilicity of the chemical), modern theories are based on compartmental kinetics and the integration of various environmental interactions. Concepts include results from quantitative structure-activity relationships (QSAR), pharmacokinetics, ecophysiology and general biology, molecular genetic aspects and selection, and finally the structure of communities and man-made alterations in them.