The Chesapeake Bay – the largest estuary in the United States - is a source of sustenance and recreation well beyond the contiguous states of Delaware, Maryland, and Virginia. With over 11,000 miles of meandrous coastline, it has long been a haven for marine life. Blue crabs, oysters, and many species of birds and fish have thrived there, and, with the introduction of mankind, have been endangered there. For several decades, the bay has been a vast depository for pollutants that have greatly impacted its delicate ecosystem.
At the Virginia Institute of Marine Science (VIMS), College of William and Mary in Gloucester Point, Virginia, Senior Scientist Mark La Guardia examines the sources, abundances, and effects of priority environmental contaminants, specifically brominated flame-retardants or polybrominated diphenyl ethers (PBDEs), on the Chesapeake Bay.
Unexpected Compounds in Pollutants
What began as a state-funded fish monitoring program for priority pollutants turned into a different type of catch when research associates at VIMS started seeing unexpected compounds appear in their analyses.
“We began looking at samples from the bay and its major tributaries on a five-year cycle,” Mark explains. “We expected to find PCBs, pesticides and other historic pollutants, but beginning in the mid-90’s PBDEs started showing up in our chromatograms. Then literature started coming out from Europe identifying the flame retardants being found in wildlife, fish, and sediments.”
Mark has reported VIMS’ findings in several published papers. He is no stranger to collecting samples from little-known tributaries that run under the roads and down to the bay. He scoops up sludge from wastewater treatment plants. He happily trudges through drainpipes to reach possible sources of the pollution. Or potential hotspots like streams where as much as 99% of the stream’s flow comes from a wastewater treatment plant.
“It’s a dirty job,” he admits. “Not like most marine scientists, who spend their time out on the bay.” Much of what he examines comes from a treatment plant, specifically sludge. This sludge, or “Biosolids,” the preferred wastewater industry term, is treated and recycled as fertilizer. That takes him directly to the treatment plant, forests, or fields of farms where the recycled sludge is applied. The sludge is freeze-dried and extracted for mass analysis.
Flame Retardants – and Deca – are Ubiquitous
Using GC/MS (gas chromatography coupled with mass spectrometry) Mark looks for evidence of PBDEs, including deca-PBDE (the fully brominated diphenyl ether, containing ten bromines). He finds “deca,” as it is commercially known, with the help of the JEOL GCmate, a mass spectrometer with an extended mass range that can detect the heavier compound. Deca is 960 mu (mass units) which is beyond the measuring range of many mass spectrometers. There is also the need to determine if other PBDE congeners or degradation products are present. With interpretation and deconvolution of mass spectra, Mark has been successful in the isolating and identifying previously unreported congeners within the technical PBDE-formulations and potential deca-BDE metabolites in biota collected from wastewater tainted streams.
Flame-retardants are ubiquitous. PBDEs are found in cell phones, computers, furniture, carpeting, wiring, and building products – basically in almost everything we use in our modern world full of plastics. But what protects us and our belongings from fires has a menacing side when it finds its way into sewage treatment plants or the watershed and eventually into living organisms, including ourselves. In fact, Mark reports, most of us have PBDEs in our bodies as a result. Not being chemically bound to the plastics and wires they protect, they can be released over time and find their way into the environment.
Akin to the persistent organic pollutant polybrominated biphenyl ethers (PBBs), which were banned in the 1970’s following the Michigan livestock feed incident and subsequent transfer to humans, PBDEs were introduced thereafter, and have found their way into human blood, body fat, and breast milk. Being ubiquitous in household products, it is found in household dust. The United States has the highest rate of PBDEs in humans, and the level has risen steadily over the past 30 years.
PBDEs were commercially manufactured in various levels of bromination, typically penta-, octa-, and deca-BDE. In 2004, penta- and octa-BDEs were banned in the European Union due to environmental and health concerns, and the American manufacturer voluntarily halted production. However deca-BDEs, which made up 83.3% of the 2001 PBDE global market demand in 2001, are still in production. To date, the only country to ban deca-PBDEs is Sweden, but states like Washington and Maine have promulgated legislation restricting its usage.
However, it may be sometime until in-use products containing these flame-retardants are replaced. Also, little is known about the fate of potential PBDE degradation products, Mark adds. There are a possible 209 different configurations (congeners) deca is the most common, and presumable resistant to environmental debromination.
|Electron capture negative-ion mass spectrum of 2,2',3,3',4,4',6,6'-octabromobiphenyl ether
||Electron capture negative-ion mass spectrum of an isomeric octa-BDE (2,2',3,4,4',5,6,6'-octabromobiphenyl ether)
||Electron ionization mass spectrum of 2,2',3,3',4,4',6,6'-octabromobiphenyl ether
“We now have enough analytical standards for all two hundred and nine different congeners,” Mark says. “But, a few years ago, there were very few available commercially.” Just to have all 209 would cost around $20-$30,000. “But with a combination of EI (electron ionization) and ECNI (electron capture negative ionization) spectra, the analysts can narrow their search.” Compounds are first classified based on their homologe group (e.g. tetra-, penta-BDEs) by EI and then reanalyzed by ECNI where PBDEs with more than six bromines produced unique spectra. This allows further homologe classification by bromine ring substitution.
Analysis and recent breakthroughs
The method of analyzing a wide range of mono-through deca-BDEs is described in a recent paper published by ACS in Environmental Science & Technology. In the paper, VIMS researchers describe the examination of 64 PBDEs in six common flame retardant mixtures, 29 of which were at concentrations >0.02% by weight and 12 previously unreported.
New findings were web-published by ES&T in September 2007(article available in the October issue) that, for the first time, prove that Deca- debrominated products are now being detected in the environment. While penta- and octa-BDEs are no longer used in U.S. manufacturing, Deca is widely used and its disposal via wastewater remains unregulated. This latest paper shows that Deca “can be biologically debrominated if released out into the environment, and these debromination products need to be included in an updated risk assessment,” said Mark.
The new paper, Evidence of Debromination of Decabromodiphenyl Ether (BDE-209) in Biota from a Wastewater Receiving Stream, authored by Mark J. La Guardia, Robert C. Hale, and Ellen Harvey, can be found on the American Chemical Society (ACS) website and is published in Environmental Science and Technology. Only ACS members can access the paper at this time through this link.
For additional PBDE ECNI mass-spectra and more information on related projects at the Virginia Institute of Marine Science, visit http://www.vims.edu/research/departments/eaah/people/faculty/professional/laguardia_borrowed.php.
"Use of Electron Capture Negative Ion Mass Spectra to Establish the Identities of Polybrominated Diphenyl Ether Flame Retardants and Their Degradation Products”; Spectroscopy; May 1, 2008.
La Guardia, M.; Hale, R.; Harvey, E.; Chen, D. Flame-Retardants and Other Organohalogens Detected in Sewage Sludge by Electron Capture Negative Ion Mass Spectrometry. Environ. Sci. Technol. 2010, 44, 4658-4664.