International journal of hygiene and environmental health
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Int J Hyg Environ Health · May 2007
Quantification of urinary chorionic gonadotropin in spontaneous abortion of pre-clinically recognized pregnancy: method development and analytical validation.
Determination of environmental impacts on reproductive health and specifically on the incidence of early spontaneous abortion requires accurate estimates of the latter. This negative reproductive outcome can be detected by the pattern of elevation and decline of human chorionic gonadotropin (hCG) levels near and shortly beyond the expected time of implantation, requiring daily biomonitoring of hCG levels during the relevant period of the menstrual cycle. Prospective pregnancy studies to assess effects of potentially toxic exposures on human reproductive outcomes can involve up to three menstrual cycles and a huge number of samples in each, for the quantification of the inherently very low hCG levels usually can be determined only in serum. ⋯ This means that the immunoassay from DPC can identify, with relatively high confidence, non-pregnant women and the typical "rise and fall" pattern of early pregnancy loss through analysis of urine samples. Results also lead to the conclusion that there is a very good agreement between expected and observed urinary hCG levels indicative of good immunoassay accuracy for the studied range of hCG concentrations. In terms of analyte stability, it can be concluded that urinary hCG is stable under the expected conditions required for ongoing investigations that include temperatures of 2-8 degrees C for up to 48 h and temperatures of around -20 degrees C for longer periods that can extend to over 3 months.
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Int J Hyg Environ Health · May 2007
The 2005 World Health Organization re-evaluation of TEFs for dioxins and dioxin-like compounds--what are the consequences for German human background levels?
In 2005 the World Health Organization (WHO) re-evaluated toxicity equivalency factors (TEFs) for dioxins and dioxin-like compounds. WHO 2005 toxicity equivalent (TEq) levels were calculated based on our data on German background levels of polychlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF) and polychlorinated biphenyls (PCB) in human blood and milk of the Duisburg birth cohort study. ⋯ The shares of PCB (31% blood, 43% milk), especially of mono-ortho-substituted PCB (4% blood and milk), on total WHO 2005 TEq has become lower. If similar congener patterns can be assumed for certain matrices, appropriate multiplication factors can be used to convert TEq values of other TEF models sufficiently to WHO 2005 TEq values.