Research - Category III: Water Quality
Experimental Determinations of Henry's Law Constants of Polybrominated
Diphenyl Ethers (PBDEs) to Evaluate Exposure to Aquatic Biota
(Funded 2002-2003)
Principal Investigators:
M. Judith Charles
Department of Environmental Toxicology
UC Davis
(530) 754-8757
mjcharles@ucdavis.edu
Hugo Destaillats
Department of Environmental Toxicology
UC Davis
(530) 752-2541
hdestaillats@ucdavis.edu
Executive Summary:
Recent research establishes the polybroninated diphenyl ethers (PBDPEs) flame-retardants are ubiquitous global pollutants and toxicants, whose prevalence in air and waters world-wide is attracting international attention. Recent research also establishes that PBDPEs bioaccumulate and biomagnify in aquatic organisms, and strongly suggests that low-level exposure to PBDPEs can adversely affect the health of humans and biota. PBDPEs are a complex mixture of 209 chemicals whose structure resembles polychlorinated biphenyls (PCBs), toxic persistent organic pollutants (POP). Unlike PCBs, whose production was banned in the 1970s, PBDPEs are currently used extensively as flame-retardants in a wide range of commercial products. They enter the environment primarily through the disposal of wastes (e.g., landfills, sewage, incineration). If current time trends continue, PBDPEs will replace PCBs and DDT as the major environmental POP over the next 15-30 years.
Because data on PBDPEs is just emerging, state and federal regulatory agencies are only becoming aware of the environmental and environmental health significance of PBDPEs. The identification of PBDPEs in harbor seals (Phoca vitulina richardsii) in the estuarine environment of the San Francisco Bay, in combination with the known ubiquity of PBDPEs warrants further investigation of these pollutants in California waters. Specifically, we must gain insight into processes governing the distribution and bioavailability of PBDPEs. Herein, we propose research that is a first step towards accomplishing this goal.
By providing the first experimental values of Henry's law constants (KH), we will be able to assess whether, like PCBs, volatilization is an important process affecting the loss of PBDPEs from waters, and inputs of PBDPEs to the atmosphere. We will measure the KH by using the established batch gas-stripping method that introduces a known volume of inert gas (N2) from the bottom of a column containing the aqueous solution. Samples will be taken over time, and the KH will be calculated from changes in the aqueous concentration.
Knowledge about volatilization and air-water exchange of PBDPEs can be used by state and federal regulatory agencies to guide a new avenue of research aimed at understanding the environmental fate and transport of PBDPEs and the aquatic toxicity of PBDPEs. The data can also provide insight into which PBDPE congeners pose the greatest health risk to aquatic organisms. For example, PBDPEs with lower KH maybe be more bioavailable to pelagic organisms, and justify research on the bioavilability of PBDPEs in the water column. Further, the data can be used to assist in reducing inputs to aquatic systems. For example, air-sparging is a conventional treatment to remove pollutants from wastewater. Should volatilization be demonstrated as a fate process, agencies may stipulate air-sparging of wastes prior to disposal to waters
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