Several congeners were found at each level of 

 chlorination for both PCDDs and PCDFs in the samples from the 

 present study. This information and the ratios of congeners 

 indicate that the sources of these compounds are probably 

 combustion processes. For example, particulates released in 

 automobile exhaust and deposited on roads may be washed from 

 road surfaces during rains and thereby enter Black Rock Harbor. 

 This, however, is only speculation and many other sources of 

 these compounds, such as power plants, incinerators and various 

 industries, are also possible. 



Assessing the effects of environmental levels of PCDDs 

 and PCDFs is a very difficult task. Many of the compounds have 

 been shown to produce toxic, teratogenic and carcinogenic effects 

 in various organisms (Safe et al., 1986). Some congeners also 

 show very high bioconcentration factors (Geyer et al., 1987). 

 The effects of these compounds vary tremendously between 

 congeners and between species tested. For example, the "no 

 effect" level for fetotoxicity and teratogenicity to rats is 100 

 million times lower for 2 , 3 , 7 , 8-tetra-CDD than for 1, 3 , 6, 8-tetra- 

 CDD (Karasek and Hutzinger, 1986) . Similarly, the LD-50 for 

 2, 3, 7, 8-tetra-CDD is 3 500 ug/kg for the hamster and 0.6 ug/kg for 

 the guinea pig (Karasek and Hutzinger, 1986) . Little is known 

 about the effects of these compounds on man (Tschirley, 1986) . 

 To complicate matters, there is large variability in the 

 bioavailability of these compounds from different soils (Umbreit 

 et al., 1986) and the accumulation of these compounds from 

 sediments is dramatically different between congeners (Kuehl et 

 al., 1987). In addition, very little is known about the effects 

 of complex mixtures of these compounds. 



In general, however, the 2 , 3 , 7, 8-substituted congeners 

 are bioconcentrated to the greatest extent (Kuehl et al., 1987) 

 and are the most toxic. Safe et al. (1986) collected data on 

 body weight loss, thymic atrophy and aryl hydrocarbon hydroxylase 

 activity in rats. Their data would suggest the following ordered 

 list of decreasing toxicity for several of the congeners 

 quantified in the present study; 2 , 3 , 7, 8-tetra-CDD > 1,2,3,7,8- 

 penta-CDD > 1, 2 , 3 , 4 , 7 , 8-hexa-CDF > 1, 2 , 3 , 7 , 8-penta-CDF > 2,3,7,8- 

 tetra-CDF. 



Few guidelines exist for assessing the significance of 

 various levels of PCDDs and PCDFs in sediments. The Center for 

 Disease Control, however, did state that exposure to soil 

 containing concentrations of 2 , 3 , 7, 8-tetra-CDD above 1 ng/g could 

 constitute a potential health risk (Belton et al . , 1985). Also, 

 the U.S. Food and Drug Administration (FDA) has set "Levels of 

 Concern" for 2 , 3 , 7, 8-tetra-CDD in fish. FDA recommends that fish 

 with concentrations greater than 0.050 ng/g wet weight not be 

 eaten. Only two meals per month should be consumed for fish 



12 



