US Geological Survey


Date of this Version



Bull Environ Contam Toxicol (2016) 97:2–3


U.S. Government Work


By the 1960s, research and monitoring efforts on chlorinated

pesticide residues in tissues of wildlife were well

underway in North America and Europe. Conservationists

and natural resource managers were attempting to resolve

whether pesticide exposure and accumulated residues were

related to population declines in several species of predatory

and scavenging birds (e.g., bald eagle Haliaeetus

leucocephalus, peregrine falcon Falco peregrinus, brown

pelican Pelecanus occidentalis and osprey Pandion haliaetus).

The avian egg was a favored sampling matrix even

before the realization that eggshell thinning was linked to

population declines (Ratcliffe 1967; Hickey and Anderson

1968) and that the concentration of p,p’-DDE in an egg was

associated with the shell thinning phenomenon (e.g., Blus

et al. 1972; Wiemeyer et al. 1988). The necessity for

making wet-weight concentration adjustments to account

for natural moisture loss during incubation of viable eggs

was realized. Correction for the more dramatic moisture

loss in non-viable decaying eggs was recognized as being

paramount. For example, the DDT residues in osprey

eggs were reported to vary by as much as eightfold without

accounting for moisture loss adjustments (Stickel et al.

1965). In the absence of adjusting concentrations to the

fresh wet-weight that was present at the time of egg laying,

the uncorrected values exaggerated contaminant concentrations,

yielding artifactual results and ultimately incorrect

conclusions. The adjustment to fresh wet-weight concentration

is equally important for many other persistent

contaminants including PCBs, dioxins, furans, and brominated

diphenyl ethers.