A new study in the journal Science by researchers Emma Teuten, Li Xu, and Christopher Reddy at the Woods Hole Oceanographic Institution (WHOI) is causing researchers to rethink the sources and fates of many chemical compounds in the environment.
It has been known for decades that industrially produced compounds such as polybrominated diphenyl ethers or PBDEs, used as flame retardants in furniture and clothing, accumulate in human and animal tissues. Structurally similar compounds, methoxylated polybrominated diphenyl ethers or MeO-BDEs, have recently been found in fish and marine mammals and are a new class of bioaccumulated compounds. In some samples, the MeO-BDEs are among the most abundant compounds in the environment after DDE, a breakdown product of the pesticide DDT, and several polychlorinated biphenyls or PCBs, but their source has remained unknown.
Teuten, lead author of the study and a postdoctoral fellow in the Department of Marine Chemistry and Geochemistry at WHOI, isolated two chemicals from 10 kilograms (about 22 pounds) of whale blubber from a True's beaked whale found dead at False Cape, Virginia, in November 2003. The blubber was supplied to Teuten and colleagues by the Virginia Marine Science Museum, which removed the whale from the beach to look for clues to its death.
After six months of painstaking lab work to remove fats and other material to get to the compounds of interest in their most pure form, Teuten had about 1 milligram (less than one ounce) to determine if the source was natural or human-produced. The researchers used the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility at WHOI, a precision carbon-dating laboratory, to analyze the sample. Natural sources have a detectable radiocarbon signal, human-produced sources from petrochemicals do not.
"It has been assumed that industrially produced compounds accumulate in animals, but our results show that natural products do as well," Teuten said. "Did the whale we studied accumulate these compounds from its diet of squid, and if so, where did the squid get them? Animals have been exposed to industrial compounds for years, and having natural compounds of similar chemical structure may help toxicologists explain how and why enzymes have the ability to metabolize compounds like PCBs."
For Teuten and colleagues, the study was a challenge from the start. They had to request and receive a permit from the National Marine Fisheries Service, which limits the "take" of marine mammals for research. With permit in hand, they contacted researchers at marine mammal stranding networks to alert them that they needed a sample the next time one became available. The True's beaked whale blubber arrived in January 2004, and months of lab work, countless dulled knives and several blenders, and an array of chemical procedures followed.
"It was like looking for a needle in a haystack," said Reddy, an associate scientist in the Marine Chemistry and Geochemistry Department. "This type of study had not been done before. In a sense we are chemical detectives. Our goal was to determine whether these compounds were industrially derived or naturally produced, and in this one sample we found they are not derived from flame retardants but are coming from nature. But where do they come from? Our next steps are to study other animals and other suspect compounds."
Since the team's findings show that very similar chemical compounds are made by humans and naturally by many plants and animals, Teuten and Reddy say many more questions need to be answered, among them whether these natural compounds are affecting the health of whales or other animals that accumulate them.
Reddy says a similar approach can be taken to determine the sources of chloroform in the atmosphere, something many have debated. "It would require many thousands or millions of liters of air to get enough chloroform to make a radiocarbon measurement, but with enough time and patience it can be done."
The study was supported by the National Science Foundation, The Camille and Henry Dreyfus Foundation, Inc., the J. Seward Johnson Fund, and the WHOI Ocean Life Institute.
Woods Hole Oceanographic Institution (WHOI) is a private, independent marine research and engineering and higher education organization located in Falmouth, MA. Its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the ocean's role in the changing global environment. Established in 1930 on a recommendation from the National Academy of Sciences, the Institution operates the U.S. National Deep Submergence Facility that includes the deep-diving submersible Alvin and the remotely operated vehicle Jason II, a fleet of global ranging ships and smaller coastal vessels, and a variety of other tethered and autonomous underwater vehicles. WHOI is organized into five departments, interdisciplinary institutes and a marine policy center, and conducts a joint graduate education program with the Massachusetts Institute of Technology.