due to reproductive failure even though the ambient concentrations are 

 well below the lethal limit for individuals. A great deal of effort 

 within the Chesapeake Bay has been expended to try to identify the cause 

 or causes of seriously depressed recruitment of the oyster Crassostrea 

 virqinica . Individual oysters seem healthy enough but the reproduction 

 has been so low over the past decade that the industry is in dire economic 

 straits. The State of Maryland is funding an oyster relocation program. 

 Oysters have been removed from oyster bars where reproduction is still 

 occurring to supplement the populations of those oyster bars where only 

 adults are found. 



5.2.2.1 Public Health 



The principal route of concern to public health for tributyltin is through 

 contact with the paint as an aerosol or liquid during application or 

 removal. Studies are needed to provide information on: 



o What are the most effective means to prevent dermal and 

 respiratory exposure to TBT in paints during application or 

 removal? 



o Is an acceptable daily intake (ADI) of 3200 ng/kg of body weight, 

 adequate to protect the health of seafood-consuming public? 



o Are there individuals or specific conditions (e.g. pregnancy) 

 which increase the risk of health effects from TBT in antifouling 

 paint? 



5.2.2.2 Toxicity Studies 



The issues provoking most discussions regarding laboratory toxicity 

 testing are: the need to know the actual butyltin species present and the 

 actual amounts in exposure solutions, and the need to better understand 

 the interactions of butyltins with sediment and the sediment dwelling 

 biological canmunity. 



The EPA in its special review has accumulated a significant body of 

 literature describing chronic toxic effects, lesions and tissue 

 abnormalities as well as behavioral aberrations resulting from exposure to 

 TBT in solution. As the ability to determine the actual flow through 

 concentrations in the nanogram per liter range is improved, toxicity 

 testing can be refined to the point where a true no effects level [NO-EL] 

 can be determined for organotin compounds. Studies are also needed that 

 focus on low-level physiological end-points determined by chronic exposure 

 testing over the full life cycle of the organism. Testing for such 

 effects as reproductive success, gametogenesis, imposex, calcification 

 mechanism, and suppression of the immune response system. 



V-7 



