When a widely used chemical is identified as an environmental health hazard and targeted for phase-out and elimination, among the most challenging questions for those involved with using and making such a chemical are: What to use instead? and Will the replacement be safe? The US Environmental Protection Agency’s (EPA) report identifying alternatives to the flame retardant hexabromocyclododecane (HBCD) illustrates how difficult those questions can be to answer. It also highlights how important it is to consider the entire life-cycle of finished products when looking for hazardous chemical replacements.
So what’s the problem? HBCD has been used as a flame retardant since the late 1960s, primarily in the polystyrene foams known as expanded and extruded polystyrene (EPS and XPS) used to insulate buildings. It’s also been used in high-impact-polystyrene plastics in electronic equipment and the back-coatings of textiles, mainly for upholstered furniture. But like other brominated flame retardants (notably the widely-used polybrominated biphenyl ethers – PBDEs) HBCD has turned out to be persistent, bioaccumulative (able to biomagnify and move up the food web as it collects in fat tissue) and toxic. It’s an endocrine disruptor with adverse reproductive, developmental, neurological and other hormonal effects. It’s also potentially carcinogenic and highly toxic to aquatic organisms. HBCD has been found in wildlife worldwide, in indoor air, household dust, human blood, fat tissue and breast milk, and it has the ability to cross the placenta. Its toxicity has earned it a spot on the list of chemicals covered by the Stockholm Convention on Persistent Organic Pollutants. Europe will discontinue its use in 2015, Canada a year later and Japan has added HBCD to the list of highly toxic substances whose use is prohibited.
Given these concerns,any new use of HBCD must be reported to the US EPA, and the EPA’s Design for Environment Program (DfE) convened a process to find out what safer alternatives might exist for use in insulation foams.
What the DfE process found were three existing chemical products that could be used as possible drop-in replacements for HBCD in these polystyrene foams. Two are TBBPA (tetrabromobisphenol-A) compounds that are environmentally persistent and – like HBCD – are bioaccumulative and also have an array of adverse health effects. The third, which the DfE report identifies as a “viable” and “safer” alternative to HBCD is a compound called butadiene styrene brominated copolymer. While this chemical is also environmentally persistent, as a polymer, this flame retardant is a big molecule, so in EPA’s assessment the butadiene styrene brominated copolymer is considered “unlikely to be released from the polystyrene” in which it’s used. Because of its molecular size and structure, it’s also expected to have low adverse human and environmental health effects, although the DfE report notes that data are not available for all toxicity endpoints and “its long-term behavior in the environment is not currently known.”
Limitations of the DfE process
While the EPA’s DfE process did find an apparently less toxic, drop-in replacement for HBCD, EPA notes that its identification of such a chemical doesn’t mean that the agency is recommending this substance. And the DfE process has limitations that prevent it from focusing on solutions that may be safer throughout the entire life-cycle of the products where HBCD has been used. The DfE assessments are limited to chemicals as they’re marketed commercially – in this case, the whole polymer being used as a flame retardant – rather than the chemicals that make up that product.The process is also structured so that DfE focuses on the problem chemical – such as the HBCD – rather than the design of the whole product in which it’s used.
What this means is that the DfE process as it’s structured doesn’t allow EPA to look at the environmental health impacts of the butadiene and styrene – both potential carcinogens – that are components of the flame retardant identified as a safer alternative to HBCD. This also means that the DfE analysis does not really delve into the environmental heath impacts or implications of relying on polystyrene foam for the EPS and XPS-based insulation products.
“Polystyrene is inherently flammable,” points out Kathy Curtis, Executive Director of Clean and Healthy New York, whose organization participated in theDfE HBCD Partnership, as the process is called. She commends what EPA has done to consider materials that can be used instead of polystyrene foams in addition to drop-in replacements for HBCD – the DfE report includes an overview of such products, among them mineral wool and perlite – but says more attention needs to be paid to solutions that aren’t direct substitutes. “Design matters,” says Curtis.
A 2011 United Nations Environment Program (UNEP) Risk Management Evaluation of HBCD, which outlines alternatives to polystyrene insulation foam containingHBCD in greater detail than the EPA’s DfE report, noted that “current building practice from Sweden and Norway, where most of the EPS and XPS used is HBCD-free, suggests that fire-safety of building materials and buildings can be obtained at a reasonable cost without the use of HBCD and without altering traditional building and construction techniques to a great extent.” While the DfE report mentions this possibility along with other options for insulation materials, it doesn’t attempt to look at these products’ environmental health impacts. But if other countries can safely insulate buildings without environmentally persistent and potentially toxic flame retardants, why can’t this be done in the US?
Whole product and life-cycle concerns
Healthy Building Network Senior Researcher Jim Vallette points out that when it comes to occupational hazards of working with EPS and XPS insulation materials, “Other than the HBCD, the logical primary concern is residual styrene monomer in the polystyrene.”
He’s talking about people working with the finished insulation products, but also explains that exposure concerns would be greater for workers involved with manufacturing these polystyrene foams and for those employed in plants where HBCD is produced. Occupational exposures are also a concern at the end of product life, when these insulation or other materials containing HBCD (or polystyrene) are disposed of.
The EPA DfE report cites a European study that measured elevated airborne HBCD dust levels in an industrial plant and found HBCD in plant workers’ blood. It also cites a study from China suggesting that over 60% of the HBCD particles released during thermal cutting of EPS and XPS would be able to penetrate lung tissue. And despite the large volume of published studies on the environmental fate of HBCD and its health effects – including by US scientists – the DfE report notes what seems to be a striking lack of comparable attention to occupational exposure to HBCD. “No readily available HBCD occupational exposure information – including biomonitoring data – was found for U.S. workers,” writes EPA.
But polystyrene with HBCD is not the only plastic insulation material prompting occupational health concerns. One of the other popular insulation products, spray polyurethane foams that are used in buildings, also pose health hazards for workers. (They’re also a serious concern in the automotive industry where these spray polyurethanes are often used.) These materials are made with isocyanates – a common one is toluene diisocyanate – that pose serious respiratory hazards and can cause asthma, bronchitis and emphysema among other illnesses. (California has selected these spray polyurethanes as one of its targeted “priority products” under the state’s Safer Consumer Products Regulations.) Isocyanates can be absorbed through the skin as well as inhaled and don’t carry an odor that might signal exposure. And it’s entirely possible that people working in construction and the automotive industry – among others – may be exposed to both the isocyanates in polyurethane spray insulation materials, and the HBCD and any other compounds, including some styrene, while manufacturing, preparing and installing EPS- and XPS-based insulation.
But it doesn’t look as if polystyrene products – which make up about 40% of global styrene production (estimated at more than 21 million tons in 2010) – will be going away any time soon. In anticipation of the 2015 EU date for eliminating HBCD use, chemical manufacturers have been ramping up production of the substitute polymeric flame retardant that the DfE report identified – a move supported by chemical companies that produce styrene, an industry worth about $41.8 billion in 2012.
The challenges of finding alternatives to these insulation products that perform equally well are considerable – but some are already in use. But as the problems with HBCD and those associated with drop-in replacements suggest, perhaps the questions we should be asking are: What’s the best way to insulate buildings? and What are the life-cycle impacts of these materials? Obviously these aren’t easy or inexpensive questions to answer but the gains in improved human and environmental health seem well worth the investment.
Elizabeth Grossman is the author of Chasing Molecules: Poisonous Products, Human Health, and the Promise of Green Chemistry, High Tech Trash: Digital Devices, Hidden Toxics, and Human Health, and other books. Her work has appeared in a variety of publications including Scientific American, Yale e360, Environmental Health Perspectives, Ensia, The Washington Post, Salon and The Nation.