Concern for bioaccumulation stems from two areas: (1) food chain 

 accumulation (biomagnification) to higher levels, and (2) human public 

 health risks from consumption. An acceptable daily intake [ADI] to 

 quantify the maximum dose of Tributyltin considered safe for a human has 

 yet to be established. However, Schweinfurth and Gunzel (1987) have 

 estimated a provisional ADI derived from the available toxicological 

 information based largely on rat and rabbit studies. Using the no 

 observed effects level [NO-EL] of 0.32 mg/kg TBID and a safety factor of 

 100 (which takes into account interspecies and intraspecies variation) , an 

 ADI of 3.2 ug/kg TBIO was estimated from calculations. Schweinfurth and 

 Gunzel (1987) also reported a tentative ADI of 1.6 ug/kg has been 

 estimated by the Japanese Ministry of Health and Welfare. Based on a 

 provisional ADI of 3.2 ug/kg of TBIO, a person with a body weight of 60 kg 

 could safely eat 192 micrograms of TBIO in food. Assuming that the 

 average person eats 100 grams of seafood daily and has no other source of 

 exposure to TBT, a concentration of 1.9 mg/kg TBIO in seafood appear to be 

 acceptable. This is higher than the 0.5 to 1.0 mg/kg found in the salmon 

 from TBT treated pens. (Schweinfurth and Gunzel, 1987) . One concern 

 raised by Frederick Brinckman at NBS was the use of TBIO as the organotin 

 species by the authors in the above study presents a potential problem, 

 because the weight of the TBT moiety effect could be wrong by a factor of 

 two (e.g. , TBIO = Bu 3 Sn-0-SnBU3 = 2 TBT molecules) . 



4 . 6 Emm^ONMENTAL CONCENTRATIONS OF ORGANOTIN IN COASTAL WATERS 



4.6.1 Early Monitoring Studies 



The first reports of shell thickening and deformation in the U.K. were 

 published by Key in 1976. At that time, no means were available to 

 measure organotins in water at the low concentrations which were then 

 present. By 1982, the French government was sufficiently concerned to 

 proceed to ban the use of TBT by recreational and smaller fishing vessels, 

 even though very little actual measured butyl tin concentration data were 

 available. The British government issued their first regulations for TBT 

 in 1985 which were intended to reduce environmental concentrations to less 

 than 20 ng/1. 



In the United States, the first published survey of TBT levels in coastal 

 waters was by Valkirs et al. (1986). Since that time, environmental 

 sampling has been conducted only in a few locations. The impetus for 

 these studies initially was the U.S. Navy's Environmental Impact Assess- 

 ment and their subsequent decision to apply TBT copolymer ablative paints 

 to the entire fleet over a ten year span. The major studies of organotin 

 concentrations in North American coastal waters, to date are: 



Northern Chesapeake Bay - Hall, 1986 



- EPA Gulf Breeze Lab, 1987 



(Published by EPA, Chesapeake Bay 

 Program, CBP/TRS 14/87, 1987) 



IV-42 



