A new approach to monitoring seabirds for contamination with polychlorinated biphenyls (PCBs) and other persistent organic pollutants (POPs) has been developed by scientists in Japan. The noninvasive test could improve research efforts to track the progress and spread of POPs, according to the study's authors.

Hideshige Takada and colleagues at the Tokyo University of Agriculture and Technology explain that existing methods for obtaining samples from living birds are rather invasive and so have seriously hampered research in this field. Blood sampling, for instance, requires trained personnel and subjects birds, in particular chicks and young adults, to potentially fatal stress. The collection of bird droppings is, of course, non-invasive, but droppings must be refrigerated and shipped to a testing laboratory before analysis can be carried out.

Researchers have previously considered the oil secreted from a bird's preening gland (located at the base of the tail feathers) as being a potential source of samples. The oil from the preening gland is used to make feathers waterproof and to ward off parasites. However, data validating preen oil's usefulness has, until now, only been available for a single species of bird.

The Japanese team has now determined PCB concentrations and profiles in the preen gland oil and corresponding abdominal adipose tissue collected from thirty seabirds (2 orders, 3 families, 10 genera, and 13 species). "This could dramatically increase the availability of seabird samples," the researchers say. "The combination of this technology in ecological research with POP analysis of preen oil will increase our knowledge of the global distribution and transport of POPs, their ecological impact, and the ecology and behavior of seabirds."

The team points out that the samples were collected from seabirds that were either roadkill or had been caught inadvertently in fishing drift nets and long-lines in the North Pacific Ocean. "Significant concentrations of PCBs were detected in all oil samples, with a concentration range of 9-4834 nanograms per gram of lipid," the team says. "PCBs in the oil had more lower-chlorinated congeners than those in corresponding abdominal adipose, suggesting that they had less opportunity to undergo metabolism before they were secreted from the gland."

Environ Sci Technol, 2007, 41, 4901-4906; http://dx.doi.org/10.1021/es0701863

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