Characterization of Phthalate Exposure among Pregnant Women Assessed by Repeat Air and Urine Samples

Abstract

BackgroundAlthough urinary concentrations of phthalate metabolites are frequently used as biomarkers in epidemiologic studies, variability during pregnancy has not been characterized.MethodsWe measured phthalate metabolite concentrations in spot urine samples collected from 246 pregnant Dominican and African-American women. Twenty-eight women had repeat urine samples collected over a 6-week period. We also analyzed 48-hr personal air samples (n = 96 women) and repeated indoor air samples (n = 32 homes) for five phthalate diesters. Mixed-effects models were fit to evaluate reproducibility via intraclass correlation coefficients (ICC). We evaluated the sensitivity and specificity of using a single specimen versus repeat samples to classify a woman’s exposure in the low or high category.ResultsPhthalates were detected in 85–100% of air and urine samples. ICCs for the unadjusted urinary metabolite concentrations ranged from 0.30 for mono-ethyl phthalate to 0.66 for monobenzyl phthalate. For indoor air, ICCs ranged from 0.48 [di-2-ethylhexyl phthalate (DEHP)] to 0.83 [butylbenzyl phthalate (BBzP)]. Air levels of phthalate diesters correlated with their respective urinary metabolite concentrations for BBzP (r = 0.71), di-isobutyl phthalate (r = 0.44), and diethyl phthalate (DEP; r = 0.39). In women sampled late in pregnancy, specific gravity appeared to be more effective than creatinine in adjusting for urine dilution.ConclusionsUrinary concentrations of DEP and DEHP metabolites in pregnant women showed lower reproducibility than metabolites for di-n-butyl phthalate and BBzP. A single indoor air sample may be sufficient to characterize phthalate exposure in the home, whereas urinary phthalate biomarkers should be sampled longitudinally during pregnancy to minimize exposure misclassification.

Biomonitoring of polycyclic aromatic hydrocarbon exposure in pregnant women in Trujillo, Peru — Comparison of different fuel types used for cooking

“…However, a study based on the collection of urine samples throughout the gestation period, and using a more effective method such as specific gravity adjustment for adjusting for urine dilution, is the only way to verify whether the observed increase represents actual changes in exposure across pregnancy stages. Creatinine adjustment may be inadequate as creatinine excretion is known to increase by 30% during the course of pregnancy (Adibi et al, 2008;Williams, 2005), and could have introduced some errors into the results, especially with regards to the changes of creatinine adjusted concentrations of OH-PAHs across the pregnancy trimesters. We also observed a non-significant increase of about 15% from the first to the second trimester which stabilized in the third trimester in our study subjects.…”

Interpreting variability in population biomonitoring data: Role of elimination kinetics

“…19 With some exceptions, these studies found that intra-individual variability in repeated spot samples for the examined analytes exceeds inter-individual variability for compounds with relatively short elimination half-lives. Exceptions included mono benzyl phthalate (MBzP) 20,21 and MEP 7 as well as summed inorganicderived arsenic species (but not individual inorganic-derived arsenic metabolites 22,23 ). These findings suggest that exposure profiles for these compounds within individuals may be more stable because of more consistent and frequent exposure events.…”

“…These findings suggest that exposure profiles for these compounds within individuals may be more stable because of more consistent and frequent exposure events. For example, Adibi et al 20 found the highest ICC among phthalate metabolites for MBzP (0.66) and that MBzP in urine was highly correlated with repeated measurements of the parent compound, butylbenzylphthalate (BBzP), in indoor air (which also showed a high ICC of 0.83). Exposure via indoor air would result in an exposure profile that is characterized by short exposure interval (nearly continuous exposures) and a correspondingly larger value for HL/t.…”

Characterization of Urinary Phthalate Metabolites Among Custodians

“…The aerosolization of phthalate-containing cleaning products presents an inhalation risk for phthalate exposures, especially for the more volatile low molecular weight phthalates. Buildings also contain flooring and wall materials that may contain high-molecular weight phthalates, which despite having low volatility have been shown to off-gas (Adibi et al, 2003(Adibi et al, , 2008Rudel et al, 2003), presenting an additional inhalation risk for phthalate exposures. Dermal exposure to phthalates can occur through direct skin contact with products during mixing or cleaning, which can be mitigated with glove use.…”