Lindsay McCormick is a Research Analyst.
Chemical and Engineering News (C&EN) recently featured an article on simple, silicone wristbands used to detect chemicals in the everyday environment. Developed by researchers from Oregon State University, these wearable wristbands act like sponges to absorb chemicals in the air, water and everyday consumer products. EDF sees exciting promise in this technology, and has begun using this tool to make the invisible world of chemicals, visible.
The C&EN article highlighted two new studies which used the wristbands to characterize flame retardant exposure – the first two published studies to demonstrate that the wristband technology can be effectively used for this purpose.
There is good reason to explore flame retardant exposure. A 1975 California flammability standard resulted in the addition of flame retardant chemicals to hundreds of millions of foam products in the U.S. including couches and foam baby products. As furniture and other products get old and breakdown, flame retardants are released into surrounding air and settle in the dust in our homes. Evidence from the CDC’s National Biomonitoring Program demonstrates that 99% of people tested have polybrominated diphenyl ether (PBDE) flame retardants in their body, and other studies indicate that children are more highly exposed to flame retardants than adults.
In the mid-2000s, certain PBDEs (penta-BDE and octa-BDE) were voluntarily phased out of production in the U.S. due to concerns about health impacts like adverse cognitive effects in children and persistence in the environment. A new suite of flame retardants emerged as replacements, including organophosphate flame retardants (OPFRs) and new brominated flame retardants (BFRs).
While less is known about the toxicity of many of these replacement flame retardants, emerging research is linking these chemicals to health effects like neurotoxicity and hormone disruption as well as persistence in the environment. Currently, the CDC biomonitoring program only examines human exposure to the PBDE flame retardants, but other studies are detecting the replacement flame retardants all over the place – in house dust, wastewater, breastmilk, and even marine animals.
The wristbands can detect more than 40 different flame retardants including PBDEs and some of the replacement flame retardants. The two studies featured in the C&EN article had children and adults wear the wristbands to explore flame retardant exposure and the performance of the wristband technology. Let’s see what they found.
Children wear the wristband
In the first study, researchers from Oregon State University used the wristbands to investigate flame retardant exposure to children, and to characterize the children’s experience wearing the wristbands.
Seventy-two preschool-aged children wore the wristbands for one week. The study revealed a total of 20 flame retardant chemicals in the children’s environments, including 14 PBDEs, four OPFRs, and two BFRs – with generally higher concentrations of the OPFRs than the PBDEs and BFRs.
The Oregon State University researchers suggest that the higher concentration of OPFRs detected in this study may reflect the shift away from PBDEs in the U.S market to these replacement flame retardants. However, they also caution against directly comparing concentrations of different flame retardants detected, given that each compound has a different affinity for the silicone wristband. More simply stated, one cannot definitively conclude that a higher concentration of OPFRs in the wristbands means the children were exposed to higher levels of OPFRs than PBDEs.
The study also explored what factors might lead to higher individual exposures to PBDEs and OPFRs. Three factors stood out: age of house, frequency of vacuuming, and sociodemographic factors.
Age of housing
Children living in houses built before 2005 tended to have higher levels of PBDE flame retardants in their wristbands than those children living in houses built after 2005, while the inverse was true for the OPFRs. These findings could reflect the phase-out of PBDEs during this timeframe and shift to the replacement flame retardants, but more investigation is necessary.
Frequency of vacuuming
In contrast to popular belief that vacuuming regularly ensures cleaner indoor air, the study found that aggregate PBDE and OPFR flame retardant levels were higher in the wristbands of children living in households where vacuuming occurred frequently (>6 times a month). The researchers surmise that the physical agitation and heat generated during vacuuming could volatilize flame retardants from house dust into the air – allowing both for inhalation of these compounds and absorption by the wristband. Some experts, however, recommend vacuuming specifically with a HEPA filter vacuum to reduce dust containing flame retardants. This study did not distinguish between households using HEPA filter vacuums versus standard vacuums.
Finally, the researchers calculated a “family context score” that integrates parental education and employment status, household income, and the home learning environment. Children living in homes with a lower family context score tended to have higher levels of flame retardants, especially for the OPFRs. These results contribute to the large body of evidence that disadvantaged communities in our society too often bear the heaviest burden of exposure to hazardous chemicals and pollution.
So, how did the kids fare wearing the wristbands? Parents reported that the children wore the wristbands with little problem. Some children even seemed to like the wristband, calling it “their own personal science bracelet.”
A good estimate of exposure
The second study compared the ability of the wristbands and hand wipes— a common tool to measure flame retardant exposure — to estimate how much of these flame retardants actually make their way into the body.
In this study, forty adults wore a wristband for a five day period, at the end of which the researchers wiped their hand with a cotton hand wipe. The researchers also collected urine samples on three separate days during the five-day study period. For two of the four OPFRs tested, the researchers found a correlation between urinary levels of these flame retardants and the levels detected by the wristbands and hand wipes. For these compounds, the wristband levels correlated more strongly to the urinary levels than did the hand wipe levels.
These results provide suggestive evidence that the wristband may more accurately represent internal flame retardant exposure than hand wipes. However, more research is needed to replicate this study with a larger sample size.
The researchers suggest that while the hand wipes may provide a good estimate of recent dermal exposures from touching contaminated surfaces, the wristbands may be better at predicting long-term or average exposures as well as inhalation exposures. In addition to integrating exposures over several days, wearing the wristband may emulate everyday exposure scenarios. For example, wearing the wristband while bathing may allow some chemicals at the surface of the wristband to be washed away – similar to the effect of washing your skin or hands.
But that’s not the only way that the wristbands may mimic real-world exposures. According to one of the developers of the wristband, Dr. Kim Anderson, the wristband may mimic the way the human body absorbs chemicals. The silicone polymers create a lipophilic structure that forms holes similar in size to pores in human cells (~1 nm in diameter), allowing chemicals to absorb deep into the polymer. In other words, the chemicals trapped by the wristband may have similarities to chemicals that can actually enter our bodies’ cells.
Looking towards the future
EDF is committed to emerging technologies with the potential to help solve our toughest environmental challenges. As illustrated by these two studies, a simple and easily deployable wristband holds considerable promise in helping us answer pressing questions about everyday chemical exposure through non-invasive means.
While these were both small studies, the results suggest a number of important research priorities, including a better understanding of the differential exposure to the full suite of flame retardants among vulnerable populations such as infants, children, pregnant women and low income communities.
This can in part be done by expanding the chemicals and age ranges included in the CDC’s National Biomonitoring Program and by integrating simple exposure tools like the wristbands into larger cohort studies. If the wristbands continue to offer an accurate, non-invasive measure of average exposure to flame retardants – as suggested by the two studies discussed here – they will become an increasingly useful research and citizen science tool.