1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

SECTION 4: RISK CHARACTERIZATION
tested in sediment collected from Outer Bolsa Bay. 4,4’-DDE also showed significantly
increased bioaccumulation in worms tested in Inner Bolsa Bay sediments.
Semi-Aquatic Birds
Semi-aquatic birds used to estimate risks included the heron, stilt, and tern (Table 4-2). The
tern was the most sensitive receptor (e.g., highest HQs) followed by the heron and then stilt.
Chemicals that showed the highest risk (Category B) included cobalt and Aroclor 1254 for
the tern; and copper, lead, zinc, and 4,4’-DDE for both heron and tern. NOAEL HQs for
these chemicals ranged from 1.4 for copper (heron) to 91 for zinc (tern). The LOAEL HQs
ranged from 1.1 for copper (heron) to 10 for zinc (tern). Two chemicals, cobalt (heron) and
lead (stilt), showed some possible risk (Category C) since they exceed NOAELs, but not
LOAELs. Several chemicals (including chromium, selenium, vanadium, and dieldrin)
showed uncertain risk since they exceeded a NOAEL, but there was not a LOAEL available
to fully quantify the risks. The NAOEL HQs for these chemicals ranged from 1.0 for
vanadium (heron) to 54 for chromium (tern).
4.1.2.2 Full Tidal
Aquatic Plants
Estimates of potential risk to aquatic plants (Table 4-1) in sediments of the Full Tidal area
indicated that risks are primarily as a result of metals and PAHs. Nickel and selenium
exceeded both chronic RTVs with HQs of 8 and 380, respectively, for chronic NOECs and 3.2
and 127, respectively, for chronic LOECs. There were 16 chemicals that exceeded chronic
LOECs, indicating a possible risk to aquatic plants (Category B). The highest HQs were
observed for barium (HQ=23), benzo(a)pyrene (HQ=18), and benzo(g,h,i)perylene. Of those
chemicals exceeding chronic LOECs, 5 were evaluated using an exposure point
concentration that was ½ the reporting limit for a non-detect.
Aquatic Invertebrates
Evaluations for aquatic invertebrates (Table 4-3) showed that there were 6 inorganic
chemicals and 20 organic chemicals with probable risk (Category A). These chemicals
exceeded acute toxicity levels, as represented in Table 4-3 by the ER-M and LC 50 amphipod
test values. The chemicals that exceeded both the ER-M and LC 50 consisted of nickel,
fluorene, phenanthrene, and low MW PAHs. The HQs resulting from comparisons to LC 50 s
tended to be higher than were observed for comparisons to ER-Ms where both RTVs were
available for the same chemical. Overall, exceedances of ER-Ms resulted in HQs less than 10,
whereas HQs for LC 50 comparisons exceeded 10 for endrin ketone (54), fluorene (143), TPH
diesel (28), waste oil (14), and combined TPH diesel plus waste oil (16).
The low-effect levels (i.e., ER-L or the LC 20 value for amphipod toxicity) were exceeded for a
number of inorganic and organic chemicals. Those which did not have or exceed an acute
effect level (discussed above) were given an overall risk rating of possible risk (Category B).
This included 8 inorganics and 10 organics. The HQs for ER-L and LC 50 exceedances were
less than 10, with the exception of dieldrin with an ER-L HQ of 380.
There was only one chemical, fluoranthene, with some possible risk (Category C) since it
exceeded the NOEC, but not any of the low-effect levels. However, there were 18 chemicals
with uncertain risk (Category U) since they exceeded the Nereis toxicity NOEC, but did not
have a low-effect level available to fully quantify the risk.
ERA REPORT 4-8 SAC/143368(004.DOC)
7/31/02