Polybrominated diphenyl ethers (PBDEs) are a group of flame retardant additives used in thermoplastics, polyurethane foam, and textiles. These diphenyl ethers possess one to ten bromine atoms; although 209 congeners are possible, only some of these are manufactured or result as degradation products. The three commercial mixtures of PBDEs, each named for the bromination level of its dominant components, are "PentaBDE," "OctaBDE," and "DecaBDE."
Flame retardant use has become widespread in large part due to unusually strict flammability standards in the state of California. California Environmental Protection Agency (Cal/EPA) studies of PBDEs in people and wildlife in the San Francisco Bay Area have revealed extremely high levels relative to the rest of the world, indicating the region is a global PBDE contamination "hot spot."
State and federal governments have responded to the rising environmental and human health concerns over PBDEs by enacting bans and encouraging voluntary phase-outs on production and use. The major manufacturer of PentaBDE and OctaBDE ceased producing these mixtures by the end of 2004, and the California Legislature banned the same commercial mixtures as of 2006. Also in 2006, the United States Environmental Protection Agency (USEPA) issued a significant new use rule on these substances, ensuring any proposed uses of these chemicals would be reviewed for safety by the agency. American chemical manufacturers voluntarily phased out the DecaBDE formulation in 2013. Also in 2013, a key California agency revised a state flammability standard to eliminate the need to incorporate these substances into upholstered furniture and many items for infants and young children.
The Regional Monitoring Program for Water Quality in the San Francisco Bay (RMP), administered by the San Francisco Estuary Institute (SFEI), has undertaken a series of monitoring and research projects to investigate the impacts of PBDEs in San Francisco Bay. The findings of this body of work are summarized in this report.
The RMP has found that PBDEs are widely detected in San Francisco Bay matrices including water and sediment, as well as in small and large tributaries to the Bay. These contaminants are also ubiquitous in Bay biota including bivalves, fish, bird eggs, and seals.
At present, a state risk assessment suggests that PBDE contamination of the Bay does not impair the beneficial use of sport fish consumption. Contamination is also unlikely to impair reproduction and development of Bay birds, according to a recent RMP-sponsored study of the toxicity of PentaBDE to tern eggs. On the other hand, it is possible that current levels of contamination may impair the health of Bay harbor seal populations, though further research is necessary to elucidate potential impacts, particularly for young, highly exposed, weaning pups. In addition, limited toxicity information suggests Bay fish and benthic organisms may also be susceptible to low level adverse effects.
Likely in response to the phase-outs and bans described above, RMP monitoring indicates a decline in contaminant levels for Bay organisms under routine study. This decline is expected to continue, and should diminish any potential impacts of PBDEs on Bay biota. The RMP developed a PBDE mass budget model that indicates rapid recovery is possible with reduced contaminant loads expected as these compounds are removed from the market.
In contrast to trends seen in Bay wildlife, concentrations in abiotic Bay media such as water and sediment have shown fewer clear temporal trends. Bay-wide averages of the dominant congener in water, PentaBDE component BDE-47, suggest a decline in contamination since 2004, though the trend is not yet statistically signficant (p > 0.05). Bay-wide averages of the dominant congener in sediment, DecaBDE component BDE-209, show little change over time. Because the phase-out of DecaBDE is still ongoing, it may be some time before a clear trend emerges for this congener.
However, levels of BDE-47 in sediment display a significant declining trend over the last decade. Because sediment mixing and sample compositing can cloud any signal of recent changes to sediment contaminant loads, it is notable that a temporal trend has already emerged in average Bay BDE-47 sediment concentrations.
The evidence of declining PBDE levels in biota and the outcome of the RMP’s mass budget forecast modeling together suggest that management actions to eliminate production and use of PBDEs should be sufficient to address the potential impacts of contamination of San Francisco Bay. The last section of this report includes recommendations for monitoring based on this review and the management actions taken to eliminate use of PBDE flame retardants.
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Over the last decade, researchers and government agencies have begun to collect occurrence, fate, and toxicity data for a number of chemicals. Some of these chemicals have been classified as contaminants of emerging concern (CECs), often due to due to their high volume use, potential for toxicity in non-target species, and the increasing number of studies that report their occurrence in the environment.