As I mentioned in my previous post, I was recently in San Francisco for the 6th International Symposium on Flame Retardants. California is a fitting host for a conference on flame retardants, as their unique flammability standard, TB-117, has likely contributed to the ubiquitous contamination of humans and the environment with brominated flame retardants (BFRs), specifically the polybrominated diphenyl ethers (PBDEs). Research has shown repeatedly that PBDEs are environmentally persistent, capable of bioaccumulating in organisms, and potentially toxic. As a result of these facts, PBDEs have been banned in several jurisdictions, and industry has agreed to a voluntary phase-out. This has led replacement chemicals being used in place of the PBDEs. These replacements are less well studied than traditional BFRs, and given that they can be structurally and functionally very dissimilar there is a need for new measurement methodologies and descriptions of their environmental fate and biological activity. The efficacy of flame retardants, which are designed to increase public safety, has also recently been called to question. At this symposium the most current state of the science for flame retardants was presented, and below I highlight some of the interesting research from the various sessions.
Studying BFRs often comes with certain analytical challenges. BFRs are tricky to analyze, and given their widespread use, they have become ubiquitous, background contaminants, often showing up in blank laboratory samples. One way to minimize background contamination is to automate and contain the entire extraction procedure. Philip Bassignani of Fluid Management Systems, presented Validating multiple matrix analysis of PBDEs using pressurized liquid extraction and multi-column clean-up, where he showcased the available technology for incorporating Pressurized Liquid Extraction (PLE) and automated multi-column Clean-up as a sample prep procedures, thereby reducing many of the problems associated with traditional manual approaches, and saving loads of time. It was a very cool talk, and made me really wish that this type of instrument was available during my research.
Another problem that was touched upon in this session was the lack of analytical standards for many of these emerging flame retardants. Standards are needed so the identity of a compound can be verified. This is particularly tricky when you are not even sure what you are looking for. Such is the case when you are trying to determine what degradation products, metabolites, or unknown compounds may be in a sample. Mehran Alaee of Environment Canada presented the work Post target determination of brominated flame retardants and related compounds in American Eels captured in Eastern Canada, which was somewhat of an environmental detective story, where they were able to deduce the structure of several unknown contaminants in samples of Eel. This is accomplished by gaining an accurate mass for the unknown compound from the time of flight mass spectrometer, and then determining the possible combination of atoms that could result in that mass, then determining whether the mass spectra of that possible combination fits with the observed spectra in the sample. It is like trying to solve a puzzle, without knowing what the picture is supposed to be.
Measurements in Abiotic Media
Once the methods are developed for analyzing these flame retardants (again not an easy task), next you can go out an measure them in real samples. Rob Letcher of Environment Canada presented the paper Comparative photolytic debromination of decabromodiphenyl ether, decabromodiphenyl ethane, and tetradecabromodiphenoxybenzene flame retardants and environmental considerations, in which he highlights some of the measurements of new and relatively huge BFRs, and some of the pathways by which they can be transformed into more toxic compounds.
Measurements in Biota
In addition to measuring flame retardants in environmental samples like, air, dust, water, and sediment, it is also important to monitor these compounds in biota. The uptake of compounds from the environment into biota is known as bioaccumulation, and if the accumulation is great enough, this can result in toxic effects. Roxana Sühring of Helmholtz-Zentrum Geesthacht, Institute of Coastal Research presented work on the accumulation of flame retardants in two different species of eel, throughout their lifecycles, From glass to silver eel – brominated flame retardants and Dechloranes in European and American eels. The work was very interesting, largely in part because of the unique life-history traits of eels (future post), and the varying susceptibility to contaminants and contaminant profile during their life cycle.
One of the reasons for concern over flame retardants is due to their toxicity. Flame retardants tend to not be acutely toxic, but rather demonstrate a chronic toxicity, often mediated through endocrine system, as several flame retardants have structural similarities to hormones, particularly the thyroid hormones. David Volz of the University of South Carolina presented some very compelling evidence Aryl phosphate esters within a major penta-BDE replacement product induce cardiotoxicity in developing zebrafish embryos: potential role of the aryl hydrocarbon receptor, that demonstrated that some flame retardants are exerting their toxicity through the aryl hydrocarbon receptor; the toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin is also mediated through this receptor.
Regrettably I missed this session as I was discussing my posters with other researchers over lunch and things went long. However, the talk Associations between maternal serum PBDEs and fetal thyroid hormones: Results from the Chemicals, Health and Pregnancy (CHirP) study, looked really cool.
Before there can be toxicity, there must be exposure. This session showed many ways (mainly dust and food) which we are being exposed to these compounds, but two of the talks were about unique occupational exposures. The first, by Anna Strid of Stockholm University looked at Exposure to brominated flame retardants during maintenance work in aircrafts. Airplanes are loaded with flame retardants, and that is probably a good thing, but continuous workplace exposure can become an issue for pilots, flight attendants, and mechanics. Another interesting and overlooked group in terms of high levels of occupational exposure, are gymnasts. Courtney Carignan of Boston University School of Public Health presented work on Gymnast exposure to flame retardants, given that much of gymnastic equipment is foam, which contains high concentration of flame retardants, levels in the air, dust and gymnasts were elevated. The work presented was just the preliminary findings and there is much more to be done, but this was really cool and will be something to keep an eye on.
The symposium concluded with talks related to how all the research that has been done can change or influence policy. One of the first challenges that will need to be addressed is to get everyone talking the same language. Andreas Rydén of Stockholm University presented A novel abbreviation standard for organobromine, organochlorine and organophosphorus flame retardants, to help get everyone on the same page, which means I will have to change all my references to TBBPA-DBPE, BEHTBP, and EHTeBB in my papers to TBBPA-BDBPE, BEH-TEB, and EH-TBB, respectively. The symposium ended with a panel discussion, which focused on whether there is a need for these flame retardants in various consumer products (e.g., insulation, couches, children’s toys and products), and the current regulatory system for flame retardants which is highly stove-piped (e.g., EPA, California Bureau of Home Furnishings, Department of Toxic Substances Control all have interests and regulations relating to flame retardants) and largely ineffective. There was a comment from the audience that flame retardants (and other chemicals in consumer products, (e.g., PFCs, musks, nanoparticles) should be regulated just as food, drugs, and pesticides are currently. One comment that really struck me is that scientists are spending lots of time and money (often public funds), to just determine what substances are in the products we are exposed to everyday. Recently, there has been lots of excellent work by researches focused on determining what is in our couches, knowledge that industry has, but does not share because of its proprietary nature. This just seems so backwards to me.
Overall it was a great symposium filled with an almost overwhelming amount of interesting research and discourse. Flame retardants are going to be an environmental and human health issue for a long time, and forums like this symposium are crucial for helping researchers gain insights and share ideas.