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Two Hundred Pound Canaries Warn of New Poisons
Like the canaries of coal mining lore, harbor seals are our harbingers of new pollutant problems for the Bay, not to mention for its human neighbors. Flame retardants recently turned up in the tissues of Bay seals and Bay Area women at levels among the highest ever reported in the world. Scientists warn that these PBDEs, shorthand for polybrominated diphenyl ethers, are only some of hundreds of new chemicals approved by the FDA, EPA, and other agencies and entering the market, and the environment, before all of their potential impacts are known.
"Just because a chemical is not in the regulatory books doesn't mean problems don't exist," says consulting scientist Rainer Hoenicke, formerly with the S.F. Estuary Institute. "Regulations are about 10 years behind the curve."
PBDEs - unregulated chemicals used in relatively high concentrations as flame retardants in electronic equipment, computers, TVs, textiles, and many home furnishings, particularly those containing polyurethane foam - have become ubiquitous over the last decade. Exactly how they end up in the Bay isn't quite understood. "It's hard to see how my foam mattress ends up in the seals," says researcher Myrto Petreas, environmental scientist for State Department of Toxic Substances Control's Hazardous Materials Lab in Berkeley. According to Petreas, while there are some point sources of PBDEs-foam manufacturers and electronic equipment dismantlers, for example-no one understands all of the chemical's pathways into the Bay. But whatever the pathway, the Bay and its biota are getting more than a fair share. A study by She, et al., co-authored by Petreas and soon to be published in the journal Chemosphere, revealed PBDE levels in Bay seal tissues as high as 1730 nanograms per gram of fat (equivalent to parts per billion). Concentrations of PBDEs in seal tissues doubled every 1.3 years (on average) in the decade between 1989 and 1998.
Harbor seals, long-lived marine mammals at the top of the aquatic food chain, are considered good indicators of Bay health, in part because they are exposed to persistent organic compounds that bioaccumulate in the food web. But in the Bay Area, it is not only seals that have elevated levels of PBDEs in their bodies. According to the study, the highest levels of PBDEs ever reported in humans are showing up in the fatty tissues of Bay Area women-an average of 86 ng/g (none of the women in the study regularly ate fish from the Bay). While the PBDE levels do not appear to be correlated with breast cancer (the original focus of the study), they are present at higher levels in younger women, consistent with the fact that PBDEs are a recent environmental contaminant.
"PBDEs are in so many things," says Petreas, noting that California requires all furnishings to pass flammability tests (unlike some other areas of the country and world). "We don't know exactly how women are ingesting them-whether they are inhaling them as dust from indoor chair cushions or other home furnishings, or other nonpoint dust." PBDEs have also been found in sewage sludge, which is then applied as fertilizer on crops. The loop may be closed when people ingest crops, or animals that have grazed on sludge-fed crops.
Scientists say people shouldn't panic about this new contaminant, but that there are health concerns for both humans and harbor seals. PBDEs are suspected of altering the regulation of both thyroid and steroid hormones that are essential for basic metabolic and reproductive functions, explains Dianne Kopec, harbor seal biologist and another of the study's authors. In the case of the seals, the long-term, chronic effects of these endocrine disrupters may not be apparent until a population is exposed to additional stress-a virus, for example, which already-weakened seals might be less able to fight off. Also of concern, says Kopec, is the addition of a new contaminant to the existing mix of harmful chemicals and metals in the Bay. "Unlike the well-known contaminants that have been recognized, monitored, and regulated for years," says Kopec, "there are currently no regulations limiting the release of PBDEs into the environment."
Though PBDE levels in the seals are about 100 times higher than those found in humans, recent studies by Cal EPA researchers using rodents show that PBDEs could impact human neurological functions. When researchers gave lab rats high dosages, their offspring showed learning and memory problems, says Cal EPA's Tom McDonald. McDonald echoes Kopec's concern: that exposure to PBDEs is being added to exposure to existing pollutants, like PCBs, and that the cumulative impacts are unknown.
So what should regulators and policymakers be doing to address this threat? Local agencies took a first step this fall, when they made the identification and characterization of emerging pollutants in the Bay-and roadblocks to their regulation-a new priority for cooperative action (as part the S.F. Estuary Project's CCMP review process). According to McDonald, this is just one example of a groundswell of concern on the part of the regulatory agencies. Hoenicke says that that interest comes none too soon. "We don't want to leave the barn door open and let other horses escape. We already made that mistake with PCBs and DDTs," he says. Kopec agrees. "Not only further research, but also immediate action is needed to address this threat."
Contacts: Mytro Petreas (510)540-3624
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