Within- and between-person variability of urinary phthalate metabolites and bisphenol analogues over seven days: Considerations of biomonitoring study design.
Level 4 - case-series / case-control
Small prospective repeat-measures observational panel study without a comparator group
PubMed 35131323 · doi:10.1016/j.envres.2022.112885
What was done
Eighteen phthalate metabolites and eight bisphenol analogues were measured in consecutive spot urine samples (total n = 401) collected from 12 individuals over seven consecutive days. Researchers calculated intraclass correlation coefficients (ICCs) to evaluate within- and between-person variability across spot samples, evaluated the impact of creatinine and specific-gravity adjustments, and compared first morning voids against daily composites.
What was found
Intraclass correlation coefficients for unadjusted spot urine were poor for monomethyl phthalate (ICC: 0.002) and bisphenol A (ICC: 0.121), while remaining moderate for monoethyl phthalate (ICC: 0.514) and monobenzyl phthalate (ICC: 0.462). Adjusting concentrations for creatinine or specific gravity increased ICC values across analytes. In addition, mono(2-ethylhexyl) phthalate functioned as a short-term marker of di(2-ethylhexyl) phthalate exposure, and most analytes measured in first morning voids correlated significantly with 24-hour composite measurements.
Why it matters
Single spot urine samples fail to reliably characterize individual exposure to rapidly cleared chemicals like bisphenol A and certain phthalates. These findings support using specific gravity or creatinine adjustment and first morning void sampling protocols to improve exposure estimates in environmental biomonitoring studies.
Limits
The study is limited by a very small cohort size (12 participants) followed for only seven days, precluding evaluation of seasonal or long-term exposure patterns. The abstract does not provide demographic characteristics, specific exposure sources, or quantitative correlation coefficients between first morning voids and daily composites.
Cited by
- supports Phthalates are water-soluble compounds whose metabolites are excreted and measurable in human urine.