Environmental Engineering Reference
In-Depth Information
few if any toxic impacts have been clearly delineated for DDT in the marine mammals
that are the focus of this report, and with tissue residues clearly on the decline, the
likelihood that they might be identifi ed in the future is declining.
3.2
TMDL Targets
The Regional Board's TMDL targets for DDT in the Newport Bay and Watershed
(SARWQCB
2006
) are summarized in Table
5
. In addition, wildlife guidance for a
fi sh diet by Environment Canada (
2000
) and by US EPA (
1995
) has been considered
as potential TMDL targets for Newport Bay and Watershed. The following sections
address the science underlying each of the proposed and considered targets.
3.2.1
Sediment TELs
The decision by US EPA Region IX (
2002
) and the Regional Board (SARWQCB
2006
) to use threshold effect levels (TELs) as TMDL sediment targets raised concern
among the regulated community, because TELs do not fully consider dose-response.
TELs rely to a considerable extent on the occurrence of a chemical in toxic sediments
Table 5
Proposed sediment, fi sh, and water column TMDL targets for total
DDT in the Newport Bay Watershed
Sediment targets (
g/kg dry wt)
a
San Diego Creek and tributaries
ʼ
6.98
Upper and Lower Newport Bay
3.89
Fish tissue targets for protection of human health (
ʼ
g/kg wet wt)
b
San Diego Creek and tributaries
100
Upper and Lower Newport Bay
100
Fish tissue targets for protection of wildlife (
ʼ
g/kg wet wt)
c
San Diego Creek and tributaries
1,000
Upper and Lower Newport Bay
50
Water column targets (
g/L)
d
San Diego Creek and tributaries
Acute Criterion
(
CMC
)
ʼ
1.1
Chronic Criterion
(
CCC
)
0.001
Human Health Criterion
0.00059
Upper and Lower Newport Bay
Acute Criterion
(
CMC
)
0.13
Chronic Criterion
(
CCC
)
0.001
Human Health Criterion
0.00059
a
Buchman (
1999
)
b
Pollock et al. (
1991
); Brodberg and Pollock (
1999
)
c
National Academy of Sciences (NAS
1972
)
d
US EPA Region IX (
2000
)
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