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 107

Fig. 12 Recovery of ospreys in Wisconsin and the Georgian Bay area of the Great Lakes.
Figure 1 in Ewins ( 1997 ) reproduced with permission
on the wintering grounds in Latin America). Part of this ongoing steady-state is the
elimination of accumulating adipose residues by laying eggs. The DDE residues in
eggs from midwestern breeding grounds and some east coast locations appear by
the mid 1990s to be below levels associated with any signifi cant effects on shell
thickness or hatching success.
Elliott et al. ( 2000 ) reported on DDT residues in osprey eggs collected from the
Columbia and Fraser River areas in the northwest. DDE residues were high and
variable. Geometric means ranged from 1.0 to 13.8 ppm by area and year from 1991
to 1997. No trends by area or year were evident. Individual eggs ranged from 0.1 to
23.7 ppm DDE. DDE/DDT ratios were also highly variable. Some of the locations
were in forested wilderness areas where little DDT had been used. Fish sampled in
1994 from these remote areas contained less than 0.005 ppm total DDT. The authors
suggested that DDT was coming from an outside source, possibly from wintering
grounds in southern Mexico. Another factor is the very high rate of DDT applications
to apple orchards during the DDT use era (Blus et al. 1987 ). Twenty three percent
of the osprey eggs had DDE residues greater than 4.2 ppm, the level associated with
eggshell thinning that is signifi cant to hatching success.
Clark et al. ( 2001 ) published a follow-up study of the Steidl et al. ( 1991b )
Delaware Bay study summarized above. Comparisons between 1989 and 1998 at
three locations in southern New Jersey were made in residue levels in eggs and fi sh,