Postmortem reference concentrations of elements in blood and urine

Abstract

To establish postmortem reference concentrations of elements. Fatal intoxications, both accidental and intentional, are a global issue. In the western world intoxications with pharmaceuticals dominate, but in other parts of the world other substances are more common. Intoxication with elemental compounds is generally considered to be uncommon. In a forensic setting, elemental intoxications are of great importance when investigating both accidental, suicidal, and homicidal deaths. Arsenic, for example, is a classical poison which also has relevance in the modern era. Unlike for pharmaceuticals, postmortem reference concentrations for elements are scarce. For many elements it is therefore unknown if, and to what extent, they are affected by postmortem redistribution. The current study presents normal postmortem reference concentrations of 68 elements in femoral blood and urine. In addition, possible sources of error such as contamination from collection tubes, preservative potassium fluoride solution and storage time are evaluated. Paired blood and urine samples from 120 cases of death by suicidal hanging in Sweden were collected. 20 cases from each of the six local units of forensic medicine were used to account for possible regional differences. Additionally, the included cases reflected both short and long storage times. To account for possible elemental contamination from collection tubes and the added potassium fluoride solution, multiple batches of tubes and multiple samples of potassium fluoride solution were also analysed. Concentrations of elements were determined by double focusing sector field ICP-MS. Key descriptive statistics for all 68 elements are provided (including mean, median and percentiles) in blood and urine. Forensic highlights include blood concentrations of total arsenic (mean: 4.25 μg/g), thallium (mean: 0.14 μg/g) and antimony (mean: 14.82 μg/g). For several elements in blood and urine ( n = 24 and n = 25, respectively) a majority of elemental concentrations were below the limit of detection. The contribution of contamination from collection tubes were minor compared to the overall mean elemental concentrations in both blood and urine. Though the added solution of potassium fluoride contained a large assortment of elements, given the small amounts of this solution added to samples, the overall contribution is minor for most elements relative to the overall mean. However, there was a significant difference between samples with short and long storage time for 22 elements in blood and 17 elements in urine. These differences reflected both increases and decreases in concentration. Relative to antemortem elemental concentrations the postmortem concentrations show both increases and decreases. Of special note are markedly higher concentrations for several elements in blood (such as cadmium, chromium, manganese and antimony) compared to several antemortem populations. In general, it can be assumed the phenomenon of postmortem redistribution is as large for elements as it is for drugs and other substances. When evaluating individual concentrations, it is important to be aware of potential sources of contamination and the potential influence of storage time. Concentrations indicating overexposure must be evaluated together with autopsy findings and case circumstances to form a holistic view of the case as a whole. The present study provides an important tool when evaluating postmortem elemental concentrations. It fills a needed gap between large antemortem population studies and postmortem case reports or small case series of elemental intoxications. Together with the forensic autopsy and circumstantial information the present references will aid in diagnosing cases of potential elemental overexposure.