Intra- and inter-individual variability of urinary phthalate metabolite concentrations in Hmong women of reproductive age

Abstract

The reproducibility of urinary phthalate metabolite concentrations has not been well characterized in nonpregnant women of reproductive age. Our primary study objectives were to describe the distribution of urinary phthalate metabolites concentrations among a population of Hmong women of reproductive age, and to evaluate intra- and inter-individual variability of phthalate metabolite concentrations. Ten phthalate metabolites were measured in first morning urine samples collected from 45 women and 20 of their spouses who were members of the Fox River Environment and Diet Study cohort in Green Bay, Wisconsin. Repeated first morning urine samples were collected and analyzed from 25 women who provided up to three samples over approximately one month. Measurement variability was assessed using intraclass correlations (ICCs) and surrogate category analysis. Linear mixed models were used to evaluate the associations between participant characteristics and phthalate metabolite concentrations. Nine of the 10 phthalate metabolites were detected in > 80% of all samples analyzed, of which seven were detected in all samples. As a measure of reliability, ICCs were strongest for monobenzyl phthalate (0.64) and weakest for the metabolites of di(2-ethylhexyl)phthalate (DEHP) (ranging from 0.13 to 0.22). Similarly, surrogate category analysis suggested that a single urine sample characterized average one-month exposure with reasonable accuracy across low, medium and high tertiles for all metabolites except the DEHP metabolites. Geometric mean concentrations of monoethyl phthalate increased with age, but patterns by education, income, body mass index, environmental tobacco smoke or season were not observed when measures were adjusted for urinary dilution. Our results suggest that the participant characteristics assessed in this study have limited influence on inter-individual variability of phthalate metabolite concentrations. With regard to intra-individual variability, our results suggest that urinary concentrations of some phthalate metabolites are more reproducible over time and less subject to exposure misclassification than others (e.g., metabolites of DEHP).

Temporal variability of urinary concentrations of phthalate metabolites, parabens and benzophenone-3 in a Belgian adult population

“…Afterward, in each group, the mean of the GM of the 11 repeat urine samples of each participant was calculated and log 10 backtransformed to obtain a group-specific GM. In a collection day, a monotonic increase of these group-specific GM across the 3 tertile categories indicates that the surrogate sample is reasonably representative of the 4-month average level of exposure (Hauser et al, 2004;Braun et al, 2012;Peck et al, 2010;Townsend et al, 2013).…”

“…Finally, we conducted a surrogate category analysis (Hauser et al, 2004;Braun et al, 2012;Peck et al, 2010;Townsend et al, 2013) where the participants were attributed to low, medium or high group according to day-specific tertile for each sample time. Afterward, in each group, the mean of the GM of the 11 repeat urine samples of each participant was calculated and log 10 backtransformed to obtain a group-specific GM.…”

“…The maximum likelihood estimates of variance components (s² w and s² b ) and covariances were obtained using random-effect models for subjects (Peck et al, 2010) while ICC 95% confidence intervals (95% CI) were calculated according Hankinson et al (Hankinson et al, 1995). ICC, ranging between 0 (no reproducibility) and 1 (perfect reproducibility), used to reflect a poor degree of reliability when below 0.40, a moderate to good reliability when ranging between 0.40 and 0.75, and an excellent reliability when above 0.75 (Rosner, 2011).…”

Plastics, the environment and human health: current consensus and future trends

“…Exposure data for BPA are similar but less extensive. While average concentrations of phthalates in selected populations worldwide appear quite similar, there is evidence of considerable variability in daily intake rates among individuals, and even within individuals (Peck et al 2009). Exposures through ingestion, inhalation and dermal contact are all considered important routes of exposure for the general population (Adibi et al 2003;Rudel et al 2003).…”

Prenatal phthalate exposure and reproductive function in young men

“…The limited size of our study may have reduced the power of the analyses and underestimated any true effects (Hodgson et al, 2010). Simultaneously, levels of DEHP-and DiNP metabolites vary considerably within individuals (Baird et al, 2010;Frederiksen et al, 2013;Fromme et al, 2007;Peck et al, 2010), including in pregnant women (Adibi et al, 2008;Cantonwine et al, 2014;Irvin et al, 2010), which might have decreased the power even further (Frederiksen et al, 2013). Still, these secondary metabolites are considered as the best available exposure markers (Calafat et al, 2013;Wittassek et al, 2011), and have been reported fairly reproducible by others (Kim et al, 2014;Townsend et al, 2013), also during pregnancy (Suzuki et al, 2009).…”