National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia 30341, USA.
Environ Health Perspect. 2010 Dec;118(12):1748-54. doi: 10.1289/ehp.1002231. Epub 2010 Aug 25.
Phthalates are metabolized and eliminated in urine within hours after exposure. Several reports suggest that concentrations of phthalate metabolites in a spot urine sample can provide a reliable estimation of exposure to phthalates for up to several months.
We examined inter- and intraperson and inter- and intraday variability in the concentrations of monoethyl phthalate (MEP), the major metabolite of diethyl phthalate, commonly used in personal care products, and mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), a metabolite of di(2-ethylhexyl) phthalate (DEHP), a polyvinyl chloride plasticizer of which diet is the principal exposure source, among eight adults who collected all urine voids (average, 7.6 samples/person/day) for 1 week.
We analyzed the urine samples using online solid-phase extraction coupled to isotope dilution-high-performance liquid chromatography-tandem mass spectrometry.
Regardless of the type of void (spot, first morning, 24-hr collection), for MEP, interperson variability in concentrations accounted for > 75% of the total variance. By contrast, for MEHHP, within-person variability was the main contributor (69-83%) of the total variance. Furthermore, we observed considerable intraday variability in the concentrations of spot samples for MEHHP (51%) and MEP (21%).
MEP and MEHHP urinary concentrations varied considerably during 1 week, but the main contributors to the total variance differed (interday variability, MEHHP; interperson variability, MEP) regardless of the sampling strategy (spot, first morning, 24-hr collection). The nature of the exposure (diet vs. other lifestyle factors) and timing of urine sampling to evaluate exposure to phthalates should be considered. For DEHP and phthalates to which people are mostly exposed through diet, collecting 24-hr voids for only 1 day may not be advantageous compared with multiple spot collections. When collecting multiple spot urine samples, changing the time of collection may provide the most complete approach to assess exposure to diverse phthalates.
邻苯二甲酸酯在暴露后数小时内即可在尿液中代谢和消除。有几项报告表明，单次尿液样本中邻苯二甲酸酯代谢物的浓度可以可靠地估计长达数月的邻苯二甲酸酯暴露情况。
我们研究了 8 名成年人在一周内收集所有尿液（平均每人每天 7.6 个样本）时，邻苯二甲酸二乙酯（DEP）的主要代谢物单乙基邻苯二甲酸酯（MEP）和二（2-乙基己基）邻苯二甲酸酯（DEHP）代谢物单（2-乙基-5-羟基己基）邻苯二甲酸酯（MEHHP）的浓度在个体内和个体间以及日内和日间的变异性。DEP 是个人护理产品中常用的一种邻苯二甲酸酯增塑剂，饮食是其主要暴露源。
我们使用在线固相萃取与同位素稀释-高效液相色谱-串联质谱法分析尿液样本。
无论尿液类型（单次样本、晨尿、24 小时收集样本）如何，MEP 的个体间浓度变异性占总方差的比例均大于 75%。相比之下，MEHHP 的个体内变异性是总方差的主要贡献者（69-83%）。此外，我们还观察到 MEHHP 和 MEP 单次样本的日内浓度变化较大（MEHHP 为 51%，MEP 为 21%）。
在一周内，MEP 和 MEHHP 的尿液浓度变化很大，但总方差的主要贡献因素不同（日内变异性，MEHHP；个体间变异性，MEP），无论采样策略如何（单次样本、晨尿、24 小时收集样本）。评估邻苯二甲酸酯暴露时，应考虑暴露的性质（饮食与其他生活方式因素）和尿液采样时间。对于人们主要通过饮食接触的 DEHP 和邻苯二甲酸酯，与多次单次样本收集相比，仅收集 1 天的 24 小时尿液可能没有优势。在收集多个单次尿液样本时，改变收集时间可能是评估不同邻苯二甲酸酯暴露情况的最完整方法。
