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consider that the complete molecular characterization of the CIB found would be essential
to assess its possible relationship with the increased tolerance.
A qualitative relationship linking genomic and population changes has been high-
lighted in these examples, reflecting accidental situations or severe chronic stress levels. It
would be worthwhile to investigate example situations of lower stress levels to determine
thresholds of contamination acceptable for populations in the long term.
13.4 Quality Threshold for Health Safety
Determination of quality thresholds of aquatic pollutants is one of the outcomes of eco-
toxicity studies. Usually, quality thresholds are determined for every pollutant separately,
on the basis of the results of controlled experiments. Ideally, concentration-effects rela-
tionships should be established from
in situ
studies, in order to integrate pollutant inter-
actions within complex environments. The latter approach still requires much research.
Such an innovative approach has been used by the National Marine Fisheries Service
(NMFS) of the NOAA to determine sediment quality thresholds for PAHs. This approach
will be highlighted here, because it answers our dilemma/questions on how to take into
account multipollution, environmental complexity, and management constraints in envi-
ronmental regulation (Johnson et al. 2002). In the NMFS approach, robust data based on
actual responses of living species to PAH polluted sites have been collected over decades.
The responses analyzed consisted of genotoxicity effects, hepatic lesions, disturbances
of reproduction, development, growth, and immunological effects in the English sole
P. vetulus
.
The response of the English sole to PAHs has been widely documented, especially in
Puget Sound, as discussed in Section 13.1.1 and Chapter 15. Relationships between sedi-
ment TPAH concentrations and biological responses have allowed an estimation of a
threshold with confidence limits, for each type of effect measured. The list of 18 PAHs con-
sidered (10 congeners with 2-3 rings, 8 congeners with 4-6 rings) was close to the list of the
16 PAHs defined by the EPA. BaP equivalents were not used because of the high emphasis
given to high molecular weight carcinogenic congeners, whereas LMW PAHs contributed
to reproduction and growth alterations (Johnson et al. 2002).
In order to assess the likely degree of injury experienced by English sole exposed to sed-
iments with different sediment PAH concentrations, expected prevalences of liver lesions
and reproductive abnormalities were calculated using a regression model. The sediment
TPAH threshold concentration below which no significant carcinogenic or adverse repro-
ductive effects in English sole are observed has been estimated as 1000 μg kg
-1
dry weight
(or 1000 ng g
-1
dry weight).
This threshold was well below the sediment quality criteria for PAHs set by the
Washington State Department of Ecology in 1995 of 7400 μg kg
-1
dry weight for LMW
aromatic hydrocarbons and 19,200 μg kg
-1
dry weight for high molecular weight aro-
matic hydrocarbons, assuming a typical value of 2% total organic carbon for Puget Sound
sediment. This estimated threshold was not based on the lowest threshold values (DNA
damage and nonneoplastic liver lesions in English sole) and was therefore not overly con-
servative; indeed, the estimated thresholds for DNA damage were 290 ng g
-1
d.w. sediment
(with upper confidence limit of 1318 ng g
-1
d.w. sediment), and 630 ng g
-1
d.w. sediment for
several reproductive effects.
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