Natural Toxin Found to Accrue in Whales
Scientists who analyzed the carcass of a rare deep-sea beaked whale have found that natural compounds similar to industrial flame retardants can accumulate in whales just like man-made chemicals.
Marine chemists at Woods Hole Oceanographic Institution in Massachusetts reported Thursday in the journal Science that they had discovered chemicals that were natural in origin but similar to industrial flame retardants that had contaminated people and wildlife worldwide.
Flame retardants called PBDEs, used to treat foam furnishings and hard-plastic electronics equipment, are doubling in concentration in the breast milk of American women every few years, and have been shown to disrupt hormones and alter brain development of lab animals.
The natural chemicals found in the whale, methoxylated PBDEs, were more abundant in marine mammals than the industrial ones, and they were probably synthesized by sea sponges and spreading in the ocean’s food web, said marine chemist Christopher Reddy, a coauthor of the study.
The findings, however, do not explain the rapid, recent buildup of the flame retardant PBDEs in human bodies and wildlife.
Mehran Alaee, a researcher at Environment Canada who is an expert in PBDEs, said there was “no evidence at all” that the flame retardants in human breast milk had a natural source. Instead, they have a different chemical profile and are ubiquitous, turning up in household dust and a variety of foods, not just seafood.
Testing of archived samples shows that they didn’t contaminate animals and human tissues until the 1970s, when industry began using them.
Tom McDonald, a scientist at California’s Office of Environmental Health Hazard Assessment, agreed, saying that “the wealth of time-trend data on the PBDEs in sediment, birds, fish, marine mammals and people clearly indicate that they do not come from natural sources.”
Nevertheless, the finding is significant because it raises questions about whether creatures can adapt to toxic substances that they encounter in the ocean.
“It’s likely that many previous generations” of animals have been exposed to natural halogenated chemicals similar to industrial pollutants, Reddy said, and may have adapted to them with no harmful effects.
If so, can animals, perhaps even humans, also adapt to the industrial ones?
“This is one of the big questions. We have no answers to this yet,” Reddy said.
“It is possible that whales and other creatures may have found ways to deal with the naturally occurring PBDE-related compounds, but that does not mean that they can deal with the ones produced via industrial processes,” said Michael Ikonomou of Canada’s Institute of Ocean Sciences.
Now scientists must figure out whether the natural ones and industrial ones are similar in toxicity. Laboratory tests on animals show the flame retardants disrupt thyroid hormones and affect brain development at levels not much higher than those found in the breast milk of some American women. Nothing, however, is known about the toxicity or effects of the natural ones.
McDonald said the methoxylated PBDEs had been measured in salmon at levels equivalent to the flame retardant PBDEs.
Although no one has tried to look for them in human bodies, they likely have amassed in people’s bodies from seafood, Alaee said.
The natural PBDEs found in the whale are among the most abundant halogenated compounds in the environment, after the pesticide DDT and industrial chemicals called PCBs.
Halogenated chemicals, formed when chlorine or bromine are added to hydrocarbons, can endure in nature for decades, magnify in the food chain and reach high levels in people, whales and other top predators.
“It has been assumed that industrially produced compounds accumulate in animals, but our results show that natural products do as well,” said Emma Teuten, the study’s lead author.
There are 209 different PBDE compounds, and scientists previously had wondered if the methoxylated ones -- also found in birds, fish and dolphins -- came from industrial sources or were naturally produced in the ocean.
The findings may “provide a very small amount of relief” to chemical manufacturers that they are not responsible for the methoxylated ones in marine animals, Reddy said.
“But this does not change any of the problems that the chemical industry has regarding the environmental and biological impacts of PBDEs used as flame retardants,” he said. “They still have their hands full with the regular PBDEs.”
California has banned products containing two of the flame retardants beginning in 2008, and the only U.S. manufacturer stopped producing them last year.
The compounds were found in a True’s beaked whale, which inhabits the North Atlantic and waters around South Africa and Australia, and has been spotted at sea only a few times. It washed ashore dead in Virginia in 2003.
Isolating the chemicals was the trickiest part of the research. Extracting less than 1 ounce of them from 22 pounds of blubber took Teuten six months.
The researchers then performed a sophisticated radiocarbon analysis, which proved that the compounds came from a living organism, not a radiocarbon-free, human-produced petrochemical.