revealed that 95 percent of the fish analyzed contained DEHP 
residues with an average DEHP concentration of 3.15 ppm. 
The alkyl phthalate measurements reported here can be com¬ 
pared, at least indirectly, to available toxicity data. Chem¬ 
ical toxicity results for aquatic organisms are usually 
presented as LC^q values (LC^g is the estimated concentration 
where the toxic substance in the surrounding water will kill 
half the population of exposed organisms within a certain time 
period, usually 96 hours.) Since the present study presents 
values for sediment concentrations, not water, an estimate of 
the water concentration using the octanol/water partitioning 
model was made. The partitioning constant (Kow) of phthalate 
esters is estimated to be 10 3 - 10 4 (TSCA 1978). The average 
sediment values on an organic carbon basis (C oc ) for the mor¬ 
tality zone are 2 ppm, 20 ppm and 2 ppm (yg/g organic acid) for 
DEP, DBP, and DEHP, respectively. The estimated ester concen¬ 
trations in water are, therefore, 0.2 ppb, 2 ppb, and 0.2 ppb 
(yg/L), respectively, for DEP, DBP and DEHP. Mayer and Sanders 
(1973) reported that acute 96 hours LC 50 values for DBP with 
fathead minnor, channel catfish, rainbow trout, scud and cray¬ 
fish fell between 730 and 10,000 ppb (yg/L). The LC^ concen¬ 
trations for DEHP were estimated to be above 10,000 ppb. The 
estimated water concentrations in the Chester River are cur¬ 
rently significantly less than these values. In addition, the 
average alkyl phthalate concentrations in oyster tissue in the 
Chester River range from 3 to 8 ppm. This is 1000-fold lower 
than the acute toxicity of alkyl phthalates for rats (intra- 
peritonel) which ranges from 3-14 g/kg (percent). In comparison, 
the LD 5 o's for organochlorine pesticides in rats are three 
orders of magnitude lower (20 - 300 mg/kg) than alkyl phthalates 
(TSCA 1978). 
Chronic toxic effects of alkyl phthalates on aquatic orga¬ 
nisms appear at much lower levels than acute toxicity. Mayer 
and Sanders (1973) reported that a concentration of only 3 ppb 
of DEHP in the water was sufficient to significantly decrease 
growth and reproduction of the crustacean Daphnia magna . Zebra 
fish and guppy reproduction was also impaired when their food 
was spiked with 50 and 100 ppm of DEHP. Various effects of 
alkyl phthalate have been reported for brine shrimp, goldfish 
and ring doves at concentrations varying from 3 to 10,000 ppb. 
No chronic or acute toxicological data are available on the 
effects of phthalates on oysters. Martin and Roosenburg (1979) 
studied oyster mortality at 10 stations in the Chester River. 
No significant mortality occurred during the four-month period 
of observation. However, during July and August five stations 
furthest upstream had dieoff of the fouling organisms and re¬ 
duced growth rates of the oysters. Ninety-six hour acute 
toxicity studies were performed on golden shiners and crayfish 
in streams receiving effluents from the Campbell's Soup plant. 
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