Sn 



Neutral Uhdissociated Free Association 

 TBTF in Paint Matrix 



Bu SrT Bu 



Aquated TBT Cation in 

 Water Media 



Figure 1.7 Dissociation of TBT Ion in Water 



The toxicity of organotin compounds to aquatic organisms is thought to 

 increase with the number of butyl substituents from one to three, and then 

 to decrease with the addition of a fourth butyl group. In order to assess 

 the fate of a particular tributyltin to derivation in water, one must 

 consider the dissociated active form, the TBT cation (Bu^Sn ) , and its 

 major metabolites presumably formed by progressive debutylation to 

 inorganic tin (Brinckman, 1981) . 



Elemental or inorganic forms of tin (as in mineral deposits or tin can) 

 appear to cause negligible toxicological effects in humans or wildlife. 

 However, in contrast, the TBT's display an increased fat solubility and, 

 consequently, enhanced ability to penetrate biological membranes, thereby 

 posing a greater toxicity potential. 



1-11 



