likely to become exhausted. 
It is recommended that Tenneco Pond be surveyed to establish 
the total phthalate plasticizer content. At the same time, co¬ 
operative research by Tenneco should be elicited to see if a more 
effective use of secondary waste water treatment by certain soils 
could be established in order to furnish long-range protection to 
the downstream ecology. 
MICROBIAL TRANSFORMATION OF TIN 
Tin should not be considered as the sole source of the exten¬ 
sive oyster mortality observed in portions of the Chester River. 
Tin should not be excluded as a partial cause of oyster mor¬ 
tality in the Chester River, particularly when coupled with other 
pollutants and with low dissolved oxygen. 
When tin enters an aquatic ecosystem, it should be assumed 
that microorganisms are present which can convert it to volatile 
tin compounds. 
Studies should be undertaken, using recently developed meth¬ 
odology, to determine if oysters bioaccumulate tin and if the 
oyster's gut flora can produce significant quantities of volatile 
tin compounds. 
9 
