Levels of phthalate metabolites in urine among mother-child-pairs - results from the Duisburg birth cohort study, Germany.
Phthalates are used ubiquitously and human exposure is widespread. Some phthalates are anti-androgens and have to be regarded as reproductive and developmental toxicants. In the Duisburg birth cohort study we examine the associations between hormonally active environmental agents and child development. Here we report the concentrations of 21 primary and secondary phthalate metabolites from seven low molecular weight (LMW) phthalates (DMP, DEP, BBzP, DiBP, DnBP, DCHP, DnPeP) and five high-molecular weight (HMW) phthalates (DEHP, DiNP, DiDP, DPHP, DnOP) in 208 urine samples from 104 mothers and their school-aged children. Analysis was performed by multidimensional liquid chromatography coupled to tandem mass spectrometry (LC/LC-MS/MS), using internal isotope-labeled standards. In both children and mothers, 18 out of 21 phthalate metabolites were detected above the limits of quantification (between 0.2 and 1.0 ?g/l) in nearly all urine samples. Among the LMW phthalates, the excretion level (geometric mean) of the ?DiBP metabolites was most prominent in children (103.9 ?g/l), followed by ?DnBP (56.5 ?g/l), and MEP (39.1 ?g/l). In mothers ?DiBP (66.6 ?g/l) was highest, followed by MEP (50.5 ?g/l), and ?DnBP (36.0 ?g/l). Among the HMW phthalates, ?DEHP was highest in children and mothers (55.7/28.9 ?g/l). Compared to reference values derived from the German Human Biomonitoring Commission, childrens metabolite concentrations were within background levels, whereas for mothers considerably higher exposure to the LMW phthalates DnBP and DiBP, and the HMW phthalate DEHP was detected (MiBP: 10.7%; MnBP: 11.7%; ?DEHP: 23.3% of the samples were above the reference values). The LMW metabolites from DMP, DiBP, and DnBP, and the HMW metabolites from DEHP and DiNP were correlated between the mothers and children, probably indicating shared exposure in the immediate surrounding environment. Children showed higher excretion levels for most of the secondary metabolites than mothers, confirming previous findings on higher oxidized metabolite levels in children. The LMW metabolites ?DiBP, ?DnBP, and MMP, and the HMW metabolites ?DEHP were negatively associated with childrens age. The LMW metabolites ?DiBP, ?DnBP, and MBzP were inversely associated with body mass index of the children. The LMW ?DiBP metabolites revealed a significant association with nicotine metabolites in urine from both children and mothers. Further analyses are ongoing to study long-term phthalate exposure and the associations with puberty outcome in these children.