ORLANDO, Fla., April 2, 2019 -- Hundreds of everyday items, from furniture to cell phones to floor wax, contain organophosphate ester (OPE) flame retardants and plasticizers. Some of these semi-volatile compounds make their way into the air, onto surfaces and even inside our bodies, with uncertain health effects. Today, researchers report that hands play a central role in transferring OPEs and other flame retardants and plasticizers throughout the indoor environment.
The researchers will present their results today at the American Chemical Society (ACS) Spring 2019 National Meeting & Exposition. ACS, the world's largest scientific society, is holding the meeting here through Thursday. It features nearly 13,000 presentations on a wide range of science topics.
Increasingly, manufacturers have relied on OPEs to replace brominated flame retardants, some of which were banned or heavily restricted because of health concerns. However, a few recent epidemiological studies have linked the replacements themselves to adverse health effects. "The toxicity of OPEs is not well understood," says Miriam Diamond, Ph.D., the project's principal investigator. "Studies are emerging that associate some OPEs with developmental effects in kids, fertility problems and possibly some types of cancer."
Previous studies have found relatively high concentrations of OPEs in indoor air and dust. However, the sources of these compounds were not always clear. "We wondered if electronic devices, especially those that heat up during use, such as computers or printers, might be important sources of flame retardants and plasticizers," says Diamond, who is at the University of Toronto.
To find out, the researchers collected about 400 samples from the homes of 51 Canadian women enrolled in the Ontario Environment Health Study. These included urine samples and hand wipes from the women, surface wipes of their electronic devices, and air and dust samples. The team used mass spectrometry to determine the concentrations of 23 different OPEs in the wipes and eight OPE metabolites in urine.
To the researchers' surprise, all indoor surfaces had similar chemical profiles, and larger electronic devices that heat up had no higher OPE levels than handheld devices. "We went into this study expecting to find that surface wipes of different electronic devices would have elevated levels of one or a few flame retardants and plasticizers that were added to their casings during the manufacturing process," Diamond says. "Instead, we found that most of the OPEs, and other flame retardants and plasticizers, were in most of the surface wipes, floor dust and on participants' hands, as well as on the electronic devices. In other words, we found most of the chemicals everywhere."
Another unexpected result was that the level of OPEs on the surface wipes of cell phones predicted about 25 percent of the variability in urine levels of OPE metabolites -- suggesting that cell phones might be major sources of internalized OPEs, or perhaps they accumulate the compounds from other sources. When people use their cell phones (which most people touch hundreds or even thousands of times per day), they ingest the compounds or absorb them through their skin.
More recently, the researchers conducted a network analysis to find correlations among the chemical profiles they identified from all of the samples. They found that regardless of which group of chemicals they examined, hands were at the center of the network. "We believe that hands are central to moving chemicals around the indoor environment," Diamond says. "This makes intuitive sense -- your hands touch everything. It's also consistent with how infectious organisms can be spread by hands that touch multiple surfaces."
Is there anything a person can do to minimize their exposure to flame retardants and plasticizers? "Yes, wash your hands!" Diamond says. "Also, wash your cell phone and other handheld electronic devices." She adds that parents should be careful about giving cell phones to small children, who often put their hands in their mouths and also gnaw on and lick objects rather than using them in the intended manner. "We didn't collect any data on kids' exposures," she says, "but it's obvious that our results could hold insights into pathways of exposure for them."
A press conference on this topic will be held Tuesday, April 2, at 3 p.m. Eastern time in the Orange County Convention Center. Reporters may check-in at the press center, Room W231B, or watch live on YouTube http://bit.ly/ACSLive_Orlando2019 ("ACSLive_Orlando2019" is case-sensitive). To ask questions online, sign in with a Google account.
The researchers acknowledge support and funding from Health Canada, Canada's Chemicals Management Plan, Natural Sciences and Engineering Research Council of Canada and the Canadian Cancer Society.
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"Everything is everywhere": A network analysis of SVOCs indoors with implications for human exposure
Due to "chemical intensification", modern indoor environments are typified by numerous natural and synthetic chemicals within consumer products, furnishings and building materials. Knowing that nearly all North Americans tested through biomonitoring are exposed to flame retardants and plasticizers, we asked which electronic devices could be sources of these chemicals and what are the likely exposure pathways. To probe these questions, we sampled and analyzed surface wipes of handheld and non-handheld electronic devices, residents' hands (palms and backs sampled twice), indoor air and dust in a study of 51 homes. First, the results showed that analytes with >50% detection frequency were 42 in total (11 organophosphate esters (OPEs), 15 polybrominated diphenyl ether congeners (PBDEs), 10 non-PBDE halogenated flame retardants (HFRs), and 6 phthalate esters). Second, we found that these chemicals, which were presumably added to specific products and materials, were distributed among all indoor surfaces sampled leading to all surfaces having similar chemical profiles or "everything is everywhere." This was contrary to expectations of finding characteristic profiles on specific device surfaces that would have indicated emission sources. Third, chemical profiles of hand palms and backs were most frequently (number of chemicals) and highly correlated with those of other surfaces sampled, especially handheld devices, rather than air or dust. A network analysis of chemical profiles showed the centrality of hands to all surfaces. From this we postulate that hands are agents of chemical transfer indoors, serving to homogenize the chemical signature of indoor surfaces. Fourth, we found differences in networks according to chemical group. For example, OPE profiles showed stronger correlations between hands and handheld devices, especially cell phones, where OPE concentrations were significantly higher on handheld than non-handheld devices. In contrast, chemical profiles in air were more central to the network for phthalates, which is consistent with the higher vapor pressure of this chemical group. Dust was more central for HFRs and PBDEs, again consistent with their generally lower vapor pressures. Finally, the finding of the centrality of hands to networks of chemical profiles has implications for exposure since chemical profiles on hands are related to absorbed dose of these chemicals.