Concentrations of Phthalate and DINCH Metabolites in Urine Samples from Czech Mothers and Newborns

Esters of phthalic acid (phthalates), mainly used as plasticisers, are well-known ubiquitous contaminants of the environment. Humans can be exposed to these chemicals through various pathways (mainly ingestion, dermal absorption or inhalation). After entering the human body, phthalates are rapidly metabolised and excreted via urine. Due to the adverse effects of some phthalates on human health (disruption of the endocrine system and carcinogenicity), they are nowadays being replaced with less harmful substitutes such as di-iso-nonyl cyclohexane-1,2-dicarboxylate (DINCH). The aim of this study was to evaluate concentrations of 18 phthalate and 4 DINCH metabolites in urine samples collected from mothers and their newborns living in 2 locations of the Czech Republic (2016–2017). Sample preparation required only enzymatic hydrolysis and dilution of the hydrolysed sample with methanol. Target compounds were identified and quantified using ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC–MS/MS). The validated method (recovery 60–126%, repeatability 1–14%, limits of quantification 0.15–0.40 ng/mL urine) was used for the analysis of 315 paired urine samples collected from mothers and their newborns. The overall concentration of target analytes was 2 × lower in urine samples collected from newborns compared to their mothers. Monobutyl phthalate (MBP) was the analyte with the highest concentrations (median 22.1 ng/mL in the mothers′ urine samples; median 21.6 ng/mL in the newborns′ urine samples), followed by mono-iso-butyl phthalate (MiBP) and monoethyl phthalate (MEP). A marked difference between samples from both locations was observed in the concentrations of target analytes in newborns, suggesting that the childcare products used in one of the hospitals might have caused this difference. Primary metabolite of DINCH, MINCH, was not found in any of the tested samples and the secondary metabolites of DINCH (OH-, oxo- and cx-MINCH) were present in only 22–23% of the measured samples collected from mothers and in 4–6% of the urine samples collected from their children at relatively low levels. Similar studies abroad reported MEP to be present at the highest levels whilst our study identified MBP as the most abundant. This result could indicate different exposure sources of phthalates in the Czech population compared to other countries, which should be further investigated.