Browsing by Subject "biomarkers"

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Parabens are environmental phenols that are most commonly found in personal care products (PCPs) worldwide. Though used widely, there is some contradictory information and data in the peer reviewed literature regarding their safety. To support informed risk assessment, more detailed information on exposure, exposure sources, and behaviors that contribute to exposure are needed. Current approaches for assessing exposure to parabens typically utilize urine samples that may not reflect average chronic exposure due to their short half-lives in the body. Wearable sensors, such as the silicone wristband (SWB), hold promise for improving exposure research in this area, particularly for chemicals that are quickly metabolized in the body. The overarching goal of this dissertation was to determine if SWBs could be an effective tool for measuring individual level exposure to parabens as a result of PCP use. Four parabens are examined herein: methylparaben, ethylparaben, propylparaben, and butylparaben. These compounds are often measured in exposure measurement matrices as a proxy for PCP exposure. Current research suggests that SWBs integrate both inhalation and dermal routes of exposure, the two major exposure routes for parabens. This dissertation therefore set out to determine if SWBs could provide more precise measures of exposure compared to more traditional approaches that utilize house dust samples, hand wipes, or spot urine samples. Aim 1 of this thesis sought to investigate the relationships between environmental and biological samples for phenols, including parabens and triclosan, in the home environment . This involved analysis of paired house dust, hand wipes, children’s urine, and SWBs collected from children in North Carolina. Guardians of these children (aged 3-6 years) completed questionnaires on habits and behaviors. All questionnaires and samples were collected between 2014 and 2016. Positive correlations for methyl-, ethyl-, and propylparaben were observed frequently in all matrices investigated. Exposure measurements from the sampled abiotic matrices were significantly correlated to associated urinary biomarkers for these parabens , although correlations with urine were higher for hand wipes and SWBs compared to dust. Everyday lotion use was also associated with significantly higher levels of urinary paraben biomarkers in children. These results demonstrated that lotion is a predictor of paraben exposure in children, and that SWBs may be a suitable tool for assessing children’s exposure to both parabens and triclosan. Aim 2 was designed to determine if SWBs could provide a quantitative estimate of total paraben internal dose by comparing their predictive ability compared to a spot urine sample. Uptake of parabens onto SWBs was assessed by asking 10 adults from central North Carolina to wear five SWBs, with one removed each day over five days. 24-hour urine samples and random spot urine samples were also collected daily to evaluate paraben biomarkers of exposure for methyl-, ethyl-, propyl-, and butylparaben. The concentrations of parabens and triclosan in SWB and spot urine samples were compared to measures of the total mass excreted over five days. Results demonstrated that butylparaben had a significant and positive linear uptake over five days, while methyl- and ethylparaben displayed an apparent steady state concentration over five days. SWBs and spot urine samples were similarly correlated to total mass excreted for parabens. Due to the advantages of SWBs over spot urine samples, such as higher sensitivity (i.e. greater detection rates), reduced participant burden, and less dependency on the timing of sample collection, SWBs may be a more suitable tool for assessing exposure to PCPs. Lastly, Aim 3 investigated the sensitivity of SWBs in their ability to detect paraben exposures resulting from the use of a specific PCP (lotion) and whether concentrations observed in SWBs correlate with the total mass of parabens excreted in urine. To support this aim, 20 adults from central North Carolina were asked to participate for two, three-day periods over two weeks. Participants were asked to keep PCP use identical between the two periods, but during one period (randomized as first or second period per participant) participants were asked to apply one pump of a body lotion (containing a known about of parabens) to the arm on which they wore the wristband. During both periods, participants wore a single SWB and collected three 24-hour urine samples. Results demonstrate that wristbands were able to differentiate paraben exposure between Lotion and No Lotion periods as well as urinary biomarkers of exposure. This study provides evidence that SWBs can detect chemical exposures originating from use of PCPs, and suggest that SWBs are a promising and sensitive tool to capture differences in PCP use in individuals. Collectively, this dissertation provides evidence that SWBs are a promising method to measure exposure to chemicals found within PCPs. Accurate exposure classification is critical for both epidemiological studies of health effects and risk assessments used for chemical regulation. This dissertation supplies the first evidence that SWBs can be used to measure common exposures, such as those from PCPs like lotions, and that these measurements realistically correlate to common measurements of internal dose.

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