Fraunhofer Institute for Biomedical Engineering IBMT, Sulzbach, Germany.
Fraunhofer Institute for Biomedical Engineering IBMT, Sulzbach, Germany.
Int J Hyg Environ Health. 2019 Jun;222(5):831-839. doi: 10.1016/j.ijheh.2019.04.009. Epub 2019 Apr 26.
To document trends in human exposure to environmental pollutants, the German Environmental Specimen Bank (ESB) has been routinely collecting and archiving 24-h urine samples from young adults at four sampling sites in Germany on an annual basis. For the purpose of normalizing measured analyte concentrations, urinary creatinine (UC), specific gravity (SG), conductivity (CON), and total urine volume (UV) of 24-h urine samples have also been recorded. These parameters are however susceptible to variation over time, as well as within/among participants and normalization against them can thus affect the interpretation of data regarding exposure to environmental pollutants. To evaluate the influence of normalization against these parameters, we first sought to determine variations of these parameters with regard to differences between sexes and trends over time. We analysed data from 8619 urine samples collected from 1997 to 2016. We observed an inverse relation between UV and UC, SG, and CON. We also found differences between sexes for UC, SG and CON, but not UV. UC, SG, and CON showed significant decreasing trends over time in both sexes. In contrast, a significant increase of over 30% in UV, independent of participant age and BMI, was revealed. This increase in UV and the concomitant sample dilution is likely to have an impact on measured analyte concentrations in 24-h urine samples. Hence, normalization of urinary concentrations is warranted when interpreting time trends of human exposure. Next, urinary calcium (Ca) concentrations of ESB participants were used to demonstrate the effects of normalization against each of the four urine parameters. From 1997 to 2016, measured Ca concentrations showed a statistically significant but scientifically implausible decrease. Normalization of Ca concentrations against UV (by calculating the total daily excretion), UC, or CON, but not SG, eliminated this decrease. Consistent with previous work, Ca concentrations in urine and total daily Ca excretion were higher for males than females. Normalization against UC, SG, or CON, however, attenuated this difference. Thus, to avoid misinterpretation in trend analysis and sex-specific excretion in 24-h urine samples, the calculation of the total daily excretion is recommended.
为了记录人体接触环境污染物的趋势，德国环境标本库（ESB）每年定期在德国四个采样点采集并保存年轻人的 24 小时尿液样本。为了使测量分析物浓度标准化，还记录了 24 小时尿液样本中的尿肌酐（UC）、比重（SG）、电导率（CON）和总尿量（UV）。然而，这些参数容易随时间变化，并且在参与者内部和之间也会发生变化，因此针对它们进行标准化可能会影响对环境污染物暴露数据的解释。为了评估针对这些参数进行标准化的影响，我们首先试图确定这些参数随性别差异和时间趋势的变化情况。我们分析了 1997 年至 2016 年采集的 8619 份尿液样本的数据。我们观察到 UV 与 UC、SG 和 CON 呈反比关系。我们还发现 UC、SG 和 CON 存在性别差异，但 UV 没有。UC、SG 和 CON 在两性中均呈随时间显著下降的趋势。相比之下，发现 UV 增加了 30%以上，与参与者年龄和 BMI 无关。UV 和相应的样本稀释的增加很可能会影响 24 小时尿液样本中分析物的测量浓度。因此，在解释人体接触的时间趋势时，有必要对尿液浓度进行标准化。接下来，使用 ESB 参与者的尿钙（Ca）浓度来证明针对四个尿液参数中的每一个参数进行标准化的影响。从 1997 年到 2016 年，测量的 Ca 浓度显示出统计学上显著但在科学上不可信的下降。通过计算每日总排泄量对 Ca 浓度进行标准化（通过计算每日总排泄量），UC、CON，但不是 SG，消除了这种下降。与之前的研究一致，男性尿液中的 Ca 浓度和每日总 Ca 排泄量均高于女性。然而，针对 UC、SG 或 CON 进行标准化则减弱了这种差异。因此，为了避免在 24 小时尿液样本的趋势分析和性别特异性排泄中出现错误解释，建议计算每日总排泄量。
