Environmental Engineering Reference
In-Depth Information
uncertainty here, but the recovery, stability and health of populations still experiencing
marginal shell thinning, suggests no detrimental effect. In addition to choosing a
threshold for toxicity, one must also determine an appropriate biomagnifi cation
factor from fi sh to egg.
Osprey are opportunistic feeders, catching the most nutritious and easiest to
catch species at any given location and time. Typical prey species vary with season,
latitude and whether the location is coastal or inland. One should expect, therefore,
some variation in biomagnifi cation from fi sh to eggs. The variation in literature
biomagnifi cation values, however, appears more related to a lack of representative
sampling of fi sh from breeding grounds and a lack of data on residues in fi sh from
wintering grounds.
The fl ounder, menhaden and largescale sucker appear to be the most important
food species for osprey studied in North America. The largescale sucker is a fresh
water species. Only the menhaden is among the species relied upon by the NAS
panel in setting the marine fi sh recommendation to protect wildlife. For the 22
determinations of biomagnifi cation from fi sh to egg determined from data in the
reports above, there is considerable uncertainty. Therefore, the best estimate from
these data for what constitutes an appropriate biomagnifi cations factor might be the
median value of 10 (0.73-87, n = 22). Values based on fi sh scraps cast from the nest
range from 1.6 to 31 (n = 5) with a median of 10.9. For reasons explained previously,
a value of 10 is most likely to be high. For example, the two values from nonmigra-
tory populations were 0.73 and 3.8.
A recommendation for DDT residues in marine fi sh should not consider DDD,
because DDD has not been shown to cause shell thinning and is not converted to
DDE. DDE causes eggshell thinning and DDT can be converted to DDE. Thus,
DDT and DDE are the important terminal residues.
If the recommendation is to protect the osprey as a sensitive representative for
other fi sh-eating species, then one needs to select a threshold level in eggs and
divide by an appropriate biomagnifi cation factor. If one were to use a threshold that
is half of the approximate lower end of the hatchability effect threshold and divide
that value by a biomagnifi cation factor of 10, the recommendation would be 150 ppb
in fi sh. This level is three times what the NAS panel recommended, but is based on
additional information that they appeared to overlook or wasn't known until after
1972. The value of 150 ppb also served as the basis for the current National criterion
for the water column discussed below.
3.2.3
US EPA Water Column Guidance to Protect Wildlife
In
1980
, the US EPA published criteria for the protection of wildlife from DDT in
the water column. The criterion was adopted as the California Toxics Rule (CTR)
standard in 2002. The wildlife criterion of 1 pptr was based on the bioaccumulation
of DDT from water into fi sh. A fi sh target residue was chosen to be 150 ppb from a
study by Anderson et al. (
1975
) in a population of brown pelicans recovering from
the reproductive effects of DDT. Accurate analysis of pptr levels of DDT in water is
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