Northwest Fisheries Science Center

The dynamics of persistent organic pollutant (POP) transfer from female dolphins to their offspring during gestation and lactation

Results of recent studies on Southern Resident killer whales demonstrate that they have high body burdens of persistent organic pollutants (POPs), namely PCBs and DDTs (Krahn et al. 2007, 2009). Most Southern Resident killer whales, including four juveniles, sampled exceeded the health-effects threshold for total PCBs in marine mammal blubber (Krahn et al. 2009). Because maternal transfer of contaminants to juveniles during rapid development of their biological systems may put these young whales at greater risk than adults for adverse health effects (e.g., immune and endocrine system dysfunction), it is important to understand the dynamics of POP transfer during gestation and lactation. There is limited information on the transfer of POPs from marine mammal females to their young during gestation and lactation, particularly for cetaceans (whales and dolphins). None of the previous studies on cetaceans have tracked how contaminant levels in mothers’ milk and in the blood of females and their calves change over the course of lactation. In order to fill this data gap, Dr. Dawn Noren is conducting a study in collaboration with the U.S. Navy Marine Mammal Program and scientists from NWFSC’s Environmental Assessment Program (Environmental Conservation Division) to concurrently measure POPs in milk and blood of bottlenose dolphin mother/calf pairs during lactation. Specifically, POPs (PCBs, PBDEs, DDTs, HCHs, and CHLDs) and lipid content are quantified in milk and blood serum collected from captive female bottlenose dolphins and their calves at four time intervals up to 15 months post-partum. POPs are also quantified in placentas from several females. Because maternal age and reproductive histories are known for all females, the researchers also hope to assess how these factors influence POP transfer dynamics from mothers to calves. These results will inform assessments of risk to delphinid calves, including killer whales, from POP exposure.


Krahn, M.M., Hanson, M.B., Baird, R.W., Boyer, R.H., Burrows, D.G., Emmons, C.K., Ford, J.K., Jones, L.L, Noren, D.P., Ross, P.S., Schorr, G.S., and Collier, T.K. 2007. Persistent organic pollutants and stable isotopes in biopsy samples (2004/2006) from Southern Resident killer whales. Marine Pollution Bulletin 54:1903-1911.

Krahn, M.M., Hanson, M.B., Schorr, G.S., Emmons, C.K.. Burrows, D.G., Burrows, D.G., Bolton, J.L., Baird, R.W., and Ylitalo, G.M. 2009. Effects of age, sex and reproductive status on persistent organic pollutant concentrations in “Southern Resident” killer whales. Marine Pollution Bulletin 58:1522-1529