DDT, Chlordane, Toxaphene and PCB Residues in Newport Bay and Watershed: Assessment of Hazard to Wildlife and Human Health - Reviews of Environmental Contamination and Toxicology - page 142

Overall, chlordane concentrations in sediments from Newport Bay are weakly
correlated with toxicity to organisms in the benthos. This correlation is not by itself
an indication of causation. The toxicity correlated with chlordane levels could well
be explained by the presence of metals that also correlated with toxicity or by the
hundreds of other chemicals that could be present, but were not measured. Other
investigators (Bay et al. 2004 ) have suggested that amphipod toxicity is associated
with the existence in the sediment and water of unmeasured organic compounds,
possibly organophosphorus or pyrethroid insecticides. The authors of the Bay
Protection and Toxic Cleanup Program report (CSWRCB 1998 ) also noted the pres-
ence of uncharacterized organic compounds that could have contributed to sediment
toxicity.

4.2.2 Effects Range Median (ERM)

Since the SARWQCB staff report ( 2006 ) compared chlordane levels to the ERM
(Long and Morgan 1990 ), the data underlying the ERM for chlordane becomes
important to any conclusions reached by the triad analysis of impairment. The ERM
is calculated from 12 data points reproduced below (Table 30 ) from Long and
Morgan ( 1990 ).
The fi rst two data points (0.3 and 0.6 ppb chlordane) were derived by equilibrium
partitioning from the chronic marine CTR standard for water to sediment using the
lower 95th and 99th percentile of the variability in K oc values (Pavlou et al. 1987 ).
These two data points are in error for two reasons. The fi rst reason is that the K oc

Table 30 Twelve data points
used to calculate the ERM for
chlordane. Table 33
reproduced from Long and
Morgan ( 1990 )
Table 33 Effects range-low
and effects range-median
values for chlordane and 12
concentrations used to
determine these values
arranged in ascending order

Concentrations
(ppb) End Point

0.3 EP 99 percentile chronic marine

0.5 ER-L

0.6 EP 95 percentile chronic marine

2.0 San Francisco Bay, California, AET

3.5 San Francisco Bay, California,

bioassay COA

3.5 San Francisco Bay, California,

bioassay COA

4.1 San Francisco Bay, California,

bioassay COA

6.0 ER-M

6.4 San Francisco Bay, California,

bioassay COA

17.4 EP freshwater lethal threshold

25.0 DuPage River, Illinois, benthos COA

31.3 Trinity River, Texas, bioassay COA

120.0 SSB LC50 for C. septemspinosa

<5,800.0 SSB LC50 for N. virens