Arctic study finds mother whales pass contaminants to fetus.

Aug 17, 2012

Desforges, J-PW, PS Ross and LL Loseto. 2012. Transplacental transfer of polychlorinated biphenyls and polybrominated diphenyl ethers in Arctic beluga whales (Delphinapterus leucas). Environmental Toxicology and Chemistry 31:296-300.

Synopsis by Craig Butt

Pregnant beluga whales pass to their fetus a portion of the pollutants – PCBs and flame retardants – they carry in their bodies, report researchers who measured the chemicals in the animals' blubber. The study is one of the first to show whales, like people, can transfer and expose their developing offspring to the long-lived contaminants.

A study of Arctic beluga whales confirms that mothers can pass more than a tenth of their chemical burden of PBDE flame retardants and PCBs to their unborn calves.

Mammals transfer contaminants during pregnancy to the developing fetus and during lactation when the baby is nursing. Lactation transfer has been well studied in marine mammals, but very little is known about the transfer of pollutants during pregnancy.

The study is unique because it examines blubber from healthy pregnant whales. Previously most research has investigated beached or ill whales. This study is only the second to report mother to fetus transfer of PBDE flame retardants in whales.

The study is also important because it focuses specifically on the amount of chemicals transferred to the fetus during pregnancy. Overall, they found about 11 percent of the total of each chemical group – PCBs and PBDEs – measured was handed down from mother to fetus.

Chemical exposure during critical times of gestation is known to cause abnormal growth and development. In some instances, prenatal exposures can impact health in adults many years later. Both classes of chemicals measured in the study are long-lived and can accumulate in animals at the top of the food chain.

The findings further understanding of potential risks associated with chemical exposures to the developing fetus before birth and nursing begins. In mammals, hormones direct critical physical and mental development during gestation. The fetus is vulnerable to chemicals that can alter hormones – generally called endocrine-disrupting chemicals. Both the PCBs and PBDEs targeted in the study can disrupt hormone functions.

PCBs and PBDEs are known to cause a diverse range of health effects, including cancer, immune system problems and thyroid diseases. In addition, early exposure to PCBs has been linked to cardiac diseases in animals.

PCBs and PBDEs are a large group of chemicals that have 1 to 10 chlorine (PCBs) or bromine (PBDEs) atoms in their chemical structure. The chemicals with fewer chlorines or bromines were more readily transferred to the fetus. The different PCB and PBDE chemicals have varying toxic effects, and this research helps scientists understand fetal exposures and potential harm from them.

PCBs had widespread use as insulating fluids in electrical equipment and other commercial products until their ban in the late 1970s. PBDEs were commonly used as flame retardant chemicals in furniture foams, textiles and electronics. Two commercial PBDE mixtures – pentaBDE and octaBDE – have been banned in many countries. The other PBDE mixture (decaBDE) is scheduled for phase out n the United States by 2013.

However, despite the ban in production, PCBs and PBDEs are still routinely detected in the environment, people and wildlife. In the environment, PCBs and PBDEs breakdown very slowly and can travel long distances, accumulating in wildlife, people and remote locations such as the Arctic.

With the help of Inuvialuit subsistence hunters who live in Canada's western Arctic, the researchers collected blubber from two pregnant beluga whales and their near-term fetuses. The whales were captured close to Hendrickson Island near Tuktoyaktuk, Northwest Territories, Canada, in 2008 and 2009. The blubber was analyzed for a variety of different PCBs and PBDEs. PCBs and PBDEs accumulate in the fatty tissues such as blubber. The total mass of PCBs and PBDEs in the mothers and fetuses was calculated based on the mass of blubber in the animals.

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