Polybrominated diphenyl ethers (PBDEs), flame retardants commonly used in consumer products around the world, and an emerging environmental contaminant, have been reported in increasing concentrations in people. Little is known about the toxicology or method of ingestion of these compounds, however, over 140 million pounds are produced annually worldwide, while production of other environmentally persistent chemicals, such as polychlorinated biphenyls (PCBs) and organochlorine pesticides, have been curtailed.
"The worry is that PBDEs, like other persistent and ubiquitous contaminants such as PCBs, are in the environment and have been reported not only in fish and in various foods, such as meat, milk and eggs, but also in substantial quantities in indoor air," says Alex Trent, executive director, Salmon of the Americas (SOTA). "While there is little that salmon farmers can do about PBDEs in the environment, we are taking steps now to identify ways to keep them out of farmed salmon." Salmon of the Americas is the trade organization representing salmon farmers in Chile, the United States and Canada.
As a first step, SOTA has just completed the first round of testing for PBDEs in farmed and wild salmon. "By tracking levels and analyzing the sources of contaminants early on, we intend to deal with the issue before it becomes a food safety problem in the hopes that other food producing groups will follow suit," says Trent.
No Established Tolerances
"There are no established guidelines or tolerances yet from the Food and Drug Administration or any other regulatory body," says Trent. Currently several organizations are working on developing the proper methodology to determine levels and several comprehensive market basket studies are in the planning stages. This will define the PBDE levels in all foods.
"In the meantime, through our own tests, we found very low levels, on the order of 1 to 4 parts per billion (ppb) in farmed salmon and only slightly lower levels in wild salmon. These levels contrast with marine fish levels of 11 to 21 ppb in striped bass and 2 to 28 ppb in halibut in California as reported in an Environmental Working Group 2002 study. Other studies show average levels of 30 ppb in freshwater striped bass in Virginia," says Trent.
Experts explain that insufficient information is currently available about PBDE toxicology or how people ingest them. "We do know that not all brominated flame retardants are the same," says Dr. Robert Hale, professor, Virginia Institute of Marine Science, College of William of Mary. "The three major PBDE formulations are used to treat different products and have different physical properties. This likely affects environmental release and exposure. But at present we don't know conclusively all the routes by which PBDEs are getting into humans or their relative importance. While food may be one source, the environment in our homes and offices are additional potential routes."
Sorting Out Risk Versus Benefit
One of the most urgent needs is for broad toxicological assessments of the different PBDE types (congeners) says Dr. Mike Gallo, director of Toxicology/professor, Robert Wood Johnson Medical School, Department of Environmental & Occupational Medicine, Piscataway, New Jersey. "It is likely, as with other compounds of this sort, that there will be varying degrees of toxicity. Only after we have tested these compounds will we know what kind of a problem we have. Current levels may be low and at the moment there does not appear to be a food safety issue. However, we need to work quickly to get more exposure and toxicity information to prevent increasing amounts from getting into the environment and the food chain."
Too Early to Draw Conclusions
Preliminary evaluations in the United States indicate low levels of PBDEs in a variety of foods. Dr. Arnold Schecter, Professor of Environmental Sciences, University of Texas School of Public Health-Dallas, recently conducted a small-scale market basket study testing 32 samples of several foods. He found large variations in PBDE levels in the sampled foods and that all food of animal origin was contaminated with PBDEs unless fat was removed. Soy infant formula did not contain any measurable PBDEs. However a recent study in the U.K. shows vegan diets to be only about 30 percent lower in PBDEs than an omnivourous diet, thereby indicating non-animal food sources.
"While this is a start, it is way too soon to draw any conclusions about health consequences or even how representative this first market basket survey is," Schecter says. "When it comes to human health, there is still much that is unknown concerning the impact of PBDEs on the human body."
Trent points out that testing for PBDEs is complicated by the fact there are few laboratories that can accurately analyze for these compounds. He notes that an evaluation of a dozen laboratories in the United States and Canada revealed only a few which had the ability to do the work to SOTA standards.
"We are ready to share our information and combine efforts in a joint evaluation of PBDEs with other food producers. We also plan to propose a unified approach to keeping these contaminants out of all foods," says Trent. "What we have is a good start."
More information: Alex Trent, Salmon of the Americas: ed@salmonoftheamericas.com
Download "PBDEs Factsheet" and "PBDE in Fish Factsheet" from the Salmon of the Americas website
