Genotoxicity and immunotoxicity of organotins

Leached from various sources, all the organotin compounds have an impact on natural aquatic environments. In both freshwater and seawater ecosystems, they are dangerous in that they can have deleterious effects on biocenoses already at low concentrations. All these compounds are known to be toxic at relatively low levels, not only for aquatic invertebrates, but also for fish and laboratory mammals. Moving easily along the trophic chains, organotins are also rapidly bioaccumulated in the tissues of non-target organisms living in the water-sediment interface, causing severe, long-term toxic effects on local epifauna, with repercussions on biodiversity and human health. Among toxic effects, genotoxicity and immunotoxicity are the most important affecting the capacity for survival of animals. Genotoxicity appearing in the form of chromosomal aberrations, increasing in frequency of micronuclei and induction of cytogenetic damage has recently been reported in mammals, fish and aquatic invertebrates. Organotins interfere selectively with the immune system of vertebrates, causing atrophy of the thymic cortex and lymphoid tissues with a consequent leucopoenia. Short-term in vitro exposures of haemocytes of various vertebrate and invertebrate organisms reveal inhibition of phagocytosis, cytolysis and/or apoptosis of leucocytes after inhibition of chemotaxis and respiratory burst, with resulting depression of cell-mediated immune responses. These immunosuppressive effects are dose- and time-dependent, and vary according to the number and type of organic moiety present. Both Ca2+-dependent and Ca2+-independent mechanisms of action have been proposed. They are linked and synergistic in triggering the cascade of secondary events that lead to toxic action.