Laboratory Practices

Wristband Preparation and Shipment

Silicone wristband stock material is low cost and commercially available. Yet, the stock material must be properly prepared in order to remove chemicals that can adversely impact analysis and chemicals that are in the desired analytical method. To minimize solvent use, wristband preparation can occur via vacuum oven conditioning when prepared according to Anderson et al. (2017). Alternatively, wristband preparation can also occur using Soxhlet extraction (Hammel et al. 2016, Hammel et al. 2018, Romanak et al. 2018). Following the preparation processes, wristbands can be analyzed using chromatography and spectrometry to ensure removal of chemicals (Anderson et al. 2017).

FIGURE 9.5 Silicone wristbands can promote collaborations between diverse stakeholders. Process steps to assess personal chemical exposures can include preparation in the laboratory, study volunteer participation, sampler transport, chemical extraction and analysis, and community engagement.

Silicone wristbands can be individually transported to study locations in airtight, impermeable containers, such as airtight polytetrafluoroethylene (PTFE) bags (Figure 9.5) (Anderson et al. 2017). Each PTFE bag can be labeled with necessary study information, such as sample identification number and the sampler on and off dates and times. Wristbands can be transported to each study location at ambient temperature through standard mail services (Figure 9.5).

Chemical Stability in Wristbands

When stored in PTFE bags, both VOCs and SVOCs have been demonstrated to be stable in the wristbands for extended periods of time (Anderson et al. 2017). Under simulated transport conditions (30°C), 17 VOCs were stable in the wristbands for 7 days and 131 SVOCs for up to 1 month (Anderson et al. 2017). Because there was no chemical loss in wristbands stored in PTFE bags at elevated temperatures, wristbands and other wristbands can be shipped long distances at ambient temperature, reducing transportation costs. Similarly, during long-term storage at -20°C, all chemical levels were stable for up to 3 months for VOCs and 6 months for SVOCs (Anderson et al. 2017), and this dataset has since been extended to 21 months. The transport and storage stability of organic chemicals provides time and cost advantages over other exposure assessment methods. By comparison, the US EPA SVOC method 8270 for water samples maintains that extractions be completed in 14days. Storage stability of chemicals in wristbands allows greater flexibility for stakeholders.

Chemical Extraction

The extraction of chemicals from wristbands can vary depending upon study design and analytes of interest. The majority of literature on wristbands include a post-deployment cleaning step to remove surface particulates (O’Connell et al. 2014a. Donald et al. 2016, Kile et al. 2016, Anderson et al. 2017, Bergmann et al. 2017a, Vidi et al. 2017, Dixon et al. 2018, Paulik et al. 2018, Dixon et al. 2019, Harley et al. 2019). Particle-bound contaminants, which are generally not bioavail- able for dermal exposure, can be removed by washing the wristbands (Anderson et al. 2008, Anderson et al. 2017). Following post-deployment cleaning, wristbands are amenable to a wide variety of chemical extraction procedures. Solvent extractions are currently the most common method (Anderson et al. 2017). For example, wristbands can be extracted with ethyl acetate (O’Connell et al. 2014a, Anderson et al. 2017, Aerts et al. 2018). Alternatively, thermal desorption onto sorbent tubes is another option which can significantly decrease extraction time compared to solvent extractions.

For any extraction method, researchers must consider the number and amount of chemicals that are removed by the silicone preparation step compared to the extraction steps after use. If the silicone preparation process removes fewer interference chemicals than the post-use extraction process, researchers are potentially analyzing chemicals left over from the original silicone manufacturing process. In practice, the silicone preparation steps should be more rigorous (e.g. higher temperature) than the post-use solvent extraction.

Chemical and Biological Analysis

Solvent extracts from wristbands can be analyzed for chemicals on a wide variety of different analytical methods, using both gas and liquid chromatography. One analytical method is a quantitative screen for 1530 target organic chemicals with only 50 minutes of instrument time per sample (Bergmann et al. 2018). Experienced chemists spend under 20 minutes per sample reviewing the chromatographic results. The target analytes include pesticides, PAHs, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), phthalates, and fragrances, which can all contribute to chemical mixtures. Although this method is a targeted screen, there is interest in applying non-targeted chemical analysis to extracts from wristbands as demonstrated by Manzano et al. (2019) and Ulrich et al. (2019).

For biological analysis, extracts can be applied to bioassays and investigated using an effects-directed analysis (Bergmann et al. 2017b, Geier et al. 2018). For instance, the developmental zebrafish model has allowed researchers to test multiple toxicity endpoints, such as physiological deformities and neurobehavioral changes, with chemical extracts from PSDs (Geier et al. 2018). The zebrafish developmental model, or other bioassays, paired with extracts from wristbands offers countless opportunities for chemical risk assessment.

Human Research Ethics

Silicone wristbands can be easily integrated into studies requiring Institutional Review Board (IRB) approval. At academic institutions, IRB approval is required for all studies involving human participants. This process ensures volunteers understand the risks, benefits, and expectations of participating in a research study. As determined by Oregon State University’s IRB on silicone wristband research, “The probability and magnitude of harm or discomfort anticipated in the research are not greater in and of themselves than those ordinarily encountered in daily life.” For other stakeholders interested in using silicone wristbands outside of a research study, IRB approval might not be required.

In several studies from Oregon State University, volunteers are given the option to have their wristband chemical results returned to them. Returning chemical results gives volunteers opportunities to learn more about scientific studies, reduce their chemical exposures, and engage in public discourse (Brody et al. 2007, Brody et al. 2014, Ohayon et al. 2017). Even if chemical exposure limits and potential health effects of exposure are not known, previous research has demonstrated that participants report benefits from receiving their chemical results (Morello-Frosch et al. 2009, Adams et al. 2011, Ohayon et al. 2017, Dixon et al. 2019). For example, members of the Swinomish Indian Tribal Community received their wristband results and volunteers reported that this information helped them become more aware of potential PAH sources in their community (Rohlman et al. 2019b). Several volunteers also reported changing their behaviors to try to reduce their exposure to PAHs (Rohlman et al. 2019b).

Silicone Wristband Applications

Since 2014, researchers have demonstrated the applicability of wristbands, compared wristbands with other conventional exposure assessment methodologies, and investigated associations between wristband results and health effects (Table 9.1).

Initial Field Applications

In two occupational settings with hot asphalt applications in O’Connell et al. (2014a), silicone wristbands were worn by roofers at an outdoor and indoor training facility and analyzed for PAHs and oxygenated-PAHs. Average PAH concentrations were three times higher at the indoor worksite compared to the outdoor worksite (O’Connell et al. 2014a). This initial wristband publication garnered significant interest in applications in areas of exposure science, occupational health, and epidemiology.

Paulik et al. (2018) focused on personal PAH exposures in non-occupational settings (n = 19) of rural Ohio, using both silicone wristbands and stationary air PSDs nearby. With the expansion of natural gas extraction (NGE) in the United States, this was one of few studies documenting personal PAH exposures with NGE occurring nearby. Wristbands from participants with active NGE wells on their properties had a significantly higher sum of 62 PAHs than participants without (Wilcoxon ranked sum, p < 0.005) (Paulik et al. 2018). Furthermore, PAH concentrations in wristbands were positively correlated with PAH concentrations sampled in air near participants’ homes (simple linear regression, p < 0.0001). This linear relationship underestimated

(Continued)

^a Gas chromatography (GC)-mass spectrometry (MS). ^b GCxGC-time of flight (ToF)-MS. ^c GC-electron capture detector (ECD).

^d Ultra-high performance liquid chromatography (UHPLC)-MS/MS.

and overestimated some personal PAH exposures based on stationary air monitors, indicating the importance of personal wristband data.

In Aerts et al. (2018), volunteers (n = 30) in Leuven, Belgium, wore silicone wristbands to assess non-occupational pesticide exposures in an urban setting, while a second wristband was placed near each volunteer’s home (Aerts et al. 2018). Researchers analyzed wristband extracts for 200 polar pesticides. Thirty-one pesticides were detected, with 48% of those pesticides being detected only in the wristbands worn by volunteers and not detected in the wristbands placed outside. Volunteers with diets featuring increased vegetable consumption were associated with increased pesticide detections, demonstrating that wristbands capture ingestion and dermal exposures. Aside from five wristbands with only ZV,(V-diethyl-meta- toluamide (DEET) detected, all other wristbands had a unique profile of pesticide detections, revealing how highly individualized chemical exposures can be and the importance of personal monitoring (Aerts et al. 2018).

As further evidence of individualized exposures, Donald et al. (2016) found that no two wristbands worn by different volunteers (n = 35) had the exact same pesticides detected. In this study, volunteers from rural farming families in Diender, Senegal, wore wristbands in the first assessment of personal occupational pesticide exposures in West Africa (Donald et al. 2016). Each volunteer wore a wristband for two separate periods, for a total of 70 wristbands in the study (100% compliance). Although inter-individual differences were large between different volunteers for the 63 pesticides in the analysis, the pairs of wristbands worn by the same individuals revealed that intra-individual differences were small. Within each individual’s paired wristbands neither the number of detections nor concentrations were significantly different (Wilcoxon signed-rank, p < 0.003). These results may be attributable to consistent behaviors and activities of individuals from week to week, whereas behaviors can vary widely between different people. Researchers can use wristbands to detect inter- and intra-individual chemical exposure patterns.

In the remote region of Alto Mayo, Peru, volunteers (n = 68) from rural and urban communities wore wristbands, as described in Bergmann et al. (2017). Wristbands were screened for the presence of 1,397 chemicals, and chemical patterns based on demographics were identified (Bergmann et al. 2017a). For example, wristbands from rural communities had a higher number of pesticide and PAH detections than urban communities, and wristbands from urban communities had higher personal care product chemical detections than rural communities (chi-square likelihood ratio test, p < 0.05). Together, these studies demonstrated silicone wristband applications across diverse communities.

Comparisons with Conventional Exposure Assessment Technologies

Concentrations in silicone wearables (i.e. wristband) have been directly compared to concentrations in paired conventional exposure assessment technologies, including hand wipes, active air samplers, serum, and urine. These studies all demonstrated strong correlations between wristband chemical concentrations and paired biological metabolite concentrations, providing further evidence that wristbands sequester the bioavailable fraction.

In Hammel et al. (2016), adults from Durham, North Carolina, wore wristbands and provided one hand wipe and three spot urine samples. Pooled urine was analyzed for metabolites of four organophosphate flame retardants (OPFRs): tris(l,3- dichloroisopropyl)phosphate (TDCIPP), tris(l,3-dichloro-2-propyl)phosphate (TCIPP), triphenyl phosphate (TPHP), and monosubstitued isopropylated triaryl phosphate (mono-ITP). Concentrations of TDCIPP and TCIPP in the wristbands strongly correlated with the associated urinary metabolites (r_s = 0.5-0.65, p < 0.001), suggesting wristbands predict internal exposure to OPFRs (Hammel et al. 2016). Wristbands may be an improved OPFR exposure assessment tool compared to hand wipes.

In follow-up to Hammel et al. (2016), Hammel et al. (2018) continued the validation study by examining wristbands for PBDE exposures. PBDEs, which also act as household flame retardants, biomagnify and have longer half-lives in the body compared to OPFRs. Participants (n = 30) provided serum samples to correlate PBDE biomarkers with wristband data (Hammel et al. 2018). Between wristbands and serum biomarkers, BDE-47, -99, -100, and -153 were positively correlated (r_s = 0.39-0.57, p < 0.05), demonstrating that silicone wristbands can quantify personal PBDE exposures, as wells as OPFR exposures.

In Dixon et al. (2018), pregnant women (n = 22) in a birth cohort in New York City wore a wristband, provided a urine sample, and wore an active air sampler (i.e. polyurethane foam (PUF) and filter housed in a personal backpack). Researchers compared concentrations of PAHs and PAH metabolites between wristbands, PUFs, filters, and urine. Researchers found three times more positive, significant correlations between PAH and PAH metabolite pairs in wristbands and urine samples than between PUF-filters and urine samples (Dixon et al. 2018). Specifically, concentrations of six PAHs in the wristbands strongly correlated with concentrations of the associated urinary metabolites (r_s = 0.44-0.76, p = 0.04 to <0.001), indicating that wristband PAH exposures are predictive of internal biomarkers.

In Quintana et al. (2019), children in California (n = 31) wore silicone wristbands and provided a urine sample to investigate nicotine exposures between smoking and nonsmoking homes. Similar to Hammel et al. (2016, 2018) and Dixon et al. (2018), Quintana et al. reported strong significant correlations between concentrations in the wristbands and in the urine (r² = 0.85, p < 0.001), further demonstrating that wristbands are reflecting the bioavailable chemical fraction and body burden (Quintana et al. 2019).

Health Effects

Several studies have begun to examine chemical concentrations from wristbands in association with adverse health effects. In Kile et al. (2016) and Lipscomb et al. (2017), wristbands quantified preschool-aged children’s flame retardant exposures (n = 72) and examined exposures in the context of emotional and social behaviors. Children from Corvallis and Eugene, Oregon, enjoyed wearing the wristbands, with one child referring to it as “their own personal science bracelet” (Kile et al. 2016). Flame retardant concentrations and sociodemographic data were correlated for multiple variables, such as house age and vacuuming frequency. In the companion article, social behaviors were measured using the Social Skills Improvement Rating Scale as rated by a child’s teacher (Lipscomb et al. 2017). Higher flame retardant exposures were associated with less responsible behavior and increased externalizing behavior problems (Lipscomb et al. 2017). This study suggested that the correlation of higher flame retardant exposures with poorer social skills may impact a child’s ability to succeed academically and socially.

Vidi et al. (2018) also characterized children’s chemical exposures, but focused on para-occupational pesticide exposures and DNA damage in hair follicles. The long-term effects of pesticide exposures on health and development are poorly understood, but indirect exposures (e.g. shared housing with an agricultural worker) may lead to adverse health effects (Vidi et al. 2017). Latino children (n = 10) from farmworker households in rural North Carolina were recruited as part of a community-based participatory research project. Each child wore a wristband to quantify pesticide exposures and provided plucked hair follicle samples to quantify DNA damage. An increasing number of pesticide detections was significantly associated with DNA damage in the papilla region of the hairs, indicative of DNA damage to epithelial cells.

Rohlman et al. (2019a) developed the novel Exposure, Location and lung Function (ELF) tool to concurrently collect daily individualized chemical exposure (silicone wristbands), location (cell phone), and respiratory health outcomes (spirometer and questionnaires) (Rohlman et al. 2019a). An ELF phone app collected questionnaire data about personal behavior, potential exposure sources, and respiratory health symptoms. Volunteers also used a handheld, Bluetooth-linked spirometer to assess lung function throughout the study. In an initial pilot study using this ELF technology in Eugene, Oregon, volunteers used the ELF with high compliance (>90%) (Rohlman et al. 2019a).

Additional Configurations of Silicone Wristbands

Since the first report of silicone wristbands in 2014, new configurations of silicone PSDs have also been developed. Multiple pilot studies have demonstrated the use of novel silicone PSDs that are not worn on the wrist (e.g. wearables).

To characterize chemical exposures in animal health studies, horses have worn silicone wearables on their halters, and cats have worn silicone pet tags. The horse cohort study evaluated broodmare PAH exposures in New' York and Pennsylvania in relationship to the incidence of foal dysphagia (Rivera et al. In Preparation). A silicone wearable was secured to the horses’ halter (Figure 9.6a). A cat case-control study evaluated flame retardant exposures using pet tags (Figure 9.6b) w'orn by geriatric cats diagnosed with feline hyperthyroidism. Community cat owners volunteered their cats (n = 78) to wear the tag. With extremely positive feedback from the owmers (e.g. “The tag didn’t bother her/him at all!”), the results indicated that elevated exposures to tris(l,3,-dichloro-2-isopropyl) phosphate were correlated w'ith feline hyperthyroidism (Poutasse et al. 2019). These two examples demonstrate the widespread applicability of silicone wearables to answer chemical exposure questions for animals, as well as humans.

Additional configurations for human volunteers include lapels and military-style dog tags. A lapel configuration on top of clothing (Figure 9.6c) selectively samples

FIGURE 9.6 Silicone wearable options: (a) horse halter, (b) pet tag, (c) lapel, and (d) military-style dog tag.

inhalation exposures, as demonstrated in O’Connell et al. (2014a). By altering where and how the silicone sampler is worn, the lapel minimizes dermal uptake. Similarly, a military-style dog tag (Figure 9.6d) can be worn around the neck to assess firefighter chemical exposures. The exposure study was driven by firefighter concern over high incidences of cancer diagnoses (Daniels et al. 2014), and firefighter participants had significant input in developing the dog tag sampler. Dog tags can be worn under or over clothing to address different chemical exposure questions. Examining occupational chemical exposure mixtures provides unique opportunities for assessing behavioral health interventions.