By the time the OCEANS '87 meeting was held in Halifax, Nova Scotia, a 

 consensus on future research needs was developing among researchers. This 

 consensus redirects research efforts away from delineating the degree of 

 the effect to "why" and "how" to predict at what concentrations in given 

 water bodies those effects would occur. There was no longer the need to 

 demonstrate the case against TBT in coastal waters. 



This rethinking has led to the development of this report. The areas of 

 focus for future studies should be in quantification of the sources of TBT 

 to the environment and detenriining the pathways of dispersion and 

 transport, the fate and behavior and subsequent toxicity and results of 

 the organotin species which have been introduced into the environment. 

 Because, in order to predict the effects of exposure of marine organisms 

 to tributyltin compounds in coastal waters, it will be necessary to 

 understand the processes, mechanisms and rates that effect the 

 distribution, transport, fate and behavior of tributyltin compounds in the 

 environment and in living organisms. It will be also vital to understand 

 the factors that influence the partitioning between the biotic and abiotic 

 environments and the biological and chemical processes that degrade TBT to 

 its metabolites. 



5.2.1 Sources, Transport, and Fate 



In order to predict the effects of the use of tributyltin compounds in 

 antifoulant paints, it will be necessary to understand and quantify the 

 inputs, rates of distribution and transport and subsequent fate and 

 behavior of TBT in the environment. Input of TBT to the water column and 

 the biota may continue long after regulatory actions, if the sediment 

 serves as a temporary reservoir of the excess over the limits of 

 solubility of TBT in water. To evaluate the probable consequences of a 

 proposed regulatory strategy, the scientific community needs to be able to 

 describe what occurs after TBT is introduced in the environment. Does it 

 accumulate? Where does it accumulate and how much does accumulate? How 

 fast is it converted to other products to which it is most probably 

 converted? At least two degradation pathways have been identified each 

 with a different sequence of intermediate chemical species. How many 

 other degradation pathways are there for TBT within coastal waters? 



5.2.1.1 Sources 



Tributyltin enters the marine environment and becomes available to 

 organisms in a variety of ways. Some of these pathways are not well 

 understood or sufficiently quantified. There is very little information, 

 for example, on the total contribution of nonpoint land sources (i.e. 

 marinas) , atmospheric inputs, and the quantities that become available to 

 organisms from temporary reservoirs (i.e resuspension from sediments) . 

 Past studies have clearly shown that the major source of tributyltin to 

 the marine environment is in the leachate from pleasure craft. For this 

 reason, current and planned regulations and legislation is targeted at 

 controlling this source. No legislation is being considered that will 



V-2 



