4.2 TREBUTYIHTN RELEASE PATES FRCM ANl'lKXJIJNG PAINTS 



The lack of acceptable (standardized) data estimating the release rates of 

 organotin compounds from different antifouling paint formulations led EPA 

 to issue a Data Call In Notice (Ed) to paint manufacturers in order to 

 obtain this information (EPA, 1986) . Over the next few years, the amount 

 of information available on the release rates of various paint 

 formulations will increase significantly. Table 4.2 is a summary of the 

 release rate data that was available prior to EPA's DCI Notice. 



4.2.1 Factors Effecting Tributyltin Release Rates from Painted Surfaces 



The Navy has determined that the release rate of organotin compounds from 

 antifouling paints from painted surfaces is dependent upon several 

 factors: (1) the chemistry of the coating, (2) the chemistry of the 

 seawater (particularly the pH and salinity) , (3) the water temperature, 

 (4) flow rate (vessel speed) and turbulence, (5) the extent of biological 

 activity, and (6) the age of the paint film. Direct measurements 

 (in-situ) of organotin release rates from ship hulls have been determined 

 by researchers at NOSC for several paint formulations (see Table 4.2). 

 Lieberman et al. (1985) have reported in-situ organotin release rates 

 (measured from Navy ships at different locations) ranging from 0.33 to 2.8 

 ug/cnr/d of TBT. laboratory studies of measurements of tributyltin 

 release rates from antifouling paints on panels have been conducted by 

 several Navy groups and have been found to range from less than 0.1 to 1.9 

 ug/cnr/d of TBT, see Table 4.3 from Desmatics (1984) who conducted the 

 data analysis for the Navy. 



To make direct TBI release rate measurements from ships, the U.S. Naval 

 Ocean Systems Center (NOSC) developed an in-situ process to measure 

 released organotin compounds from painted surfaces of ships. The protocol 

 consists of using a polycarbonate half dome, which is held on the 

 underwater surface of a ship hull by differential water pressure 

 (Lieberman et al., 1985). As utilized, this device permits collection of 

 water samples that can be analyzed to estimate release rates from aged as 

 well as fresh paint coatings under representative environmental conditions 

 (salinity, temperature, dissolved oxygen and other water quality 

 parameters). The effect of bacterial and algal films on the, paint 

 surface, which may modify the rate of TBT release is thereby accounted for 

 by using the in-situ device. The rate of water circulation through the 

 device can be regulated to simulate different harbor conditions, vessel 

 speeds or can be used to determine steady state release rates. The 

 purpose of these studies was to determine the relative release rates of 

 different paint formulations that the Navy had under consideration for 

 fleetwide use. In the NOSC studies, tributyltin cation reported as the 

 oxide was the form of butyltin which was measured by atomic absorption 



IV-3 



