totally eliminate the use of organotin antifouling paints and, therefore 

 some amounts of TBT will continue to enter the Nation's estuaries. 

 Because of the serious concern about the toxicity of TBT to certain 

 organisms, databases should be developed that will allow quantification of 

 total loadings and identification of geographical areas of concern as well 

 as providing direction for management decisions. 



Currently, ambient concentrations of tributyltin are only being monitored 

 in a few locations, particularly where there is a large U.S. Navy 

 presence. The measurement of TBT should be included in ongoing routine 

 watershed water quality monitoring programs. It is only in this manner 

 that managers can evaluate the effectiveness of the reduction of inputs by 

 legislation or regulation. Another area that is not well quantified is 

 the contribution of TBT to receiving waters due to episodic events, such 

 as heavy rainfall or flooding, that can deliver large amounts of TBT from 

 nonpoint sources over very short periods of time. Frequently these 

 episodic events occur in the spring when much of the boat bottom painting 

 is done (at least for pleasure craft) and can coincide with spawning 

 events in rivers and estuaries. The result is the intermittent exposure 

 of sensitive live history stages (i.e. eggs and larvae) to toxic levels of 

 TBT. 



Studies are needed to provide information on: 



o What are the quantities of atmospheric and other nonpoint source 

 of TBT entering the marine environment. 



o What monitoring of TBT is necessary to evaluate the effectiveness 

 of the new legislation and regulation? 



o What are the quantities of TBT delivered to receiving water 

 during episodic or climatic events? 



o What practices should be encouraged or required to ensure proper 

 disposal by marinas of spilled paint, used brushes and rags, TBT 

 contaminated sandpaper and grit, and empty paint cans? 



5.2.1.2 Transport 



To be able to predict downstream concentrations of tributyltin compounds, 

 it is necessary to understand the patterns of tributyltin partitioning 

 occurring in the environment. This means one has to be able to predict 

 what proportion of the organotin, which is introduced into the 

 environment, remains in solution in the water? What proportion resides in 

 the surface microlayer and what portion is absorbed onto sediment? Within 

 the sediments, how is the organotin species partitioned between the 

 nephloid layer, the interstitial pore water and the subsurface layers? 

 Can the behavior of organotin in different localities be described by 

 similar partitioning coefficients? 



V-3 



