Carbon-14 in the biosphere and humans

Application and implications of radiocarbon dating in forensic case work: when medico-legal significance meets archaeological relevance

The estimation of the postmortem interval for skeletal remains is a crucial aspect of forensic anthropology. This paper illustrates the importance of radiocarbon analysis for establishing medico-legal significance and supporting forensic identification, through the analysis of three case studies for which the years of both birth and death were investigated. In Audresselles, Northern France, a partial skull was discovered with no contextual information or identity. Radiocarbon dating yielded an average calibrated calendar age of 4232 BCE (92.5% probability), indicating significant archaeological value but no forensic relevance. In the second case, skeletal remains were found in the flooded underground of a historical fort at Wimereux, Northern France, also with no identity. Radiocarbon dating based on the bomb-pulse curve indicated a calibrated date of death in 1962 CE (37.3% probability) or 1974-1975 CE (58.1% probability), both surpassing the French statute of limitations. Lastly, a skeleton with a suspected identity was discovered near Valenciennes, Northern France, and various biological tissues underwent radiocarbon dating. A bone sample suggested a calibrated date of death of 1998-2002 CE (84.6% probability), differing from a hair sample (2013-2018 CE, 83.3% probability) because of the slower bone tissue remodeling process. DNA analysis confirmed the person's identity, reported missing a decade prior to the discovery of the remains, following the alignment of the radiocarbon results with the individual's year of birth based on dental tissues and year of death. These case studies reveal that traditional radiocarbon dating and bomb-pulse dating are essential tools for estimating the postmortem interval, providing mutual benefits for archaeologists, forensic anthropologists, and the criminal justice system.

Key points

Traditional radiocarbon dating and bomb-pulse dating are essential tools to establish the archaeological relevance or medico-legal significance of human skeletal remains.Bomb-pulse dating enables assessment of an individual's years of birth and death.Bomb-pulse dating helps to narrow down the pool of candidates for identification.Radiocarbon analysis provides mutual benefits for archaeologists, forensic anthropologists, and the criminal justice system.

Examining the use of different sample types following decomposition to estimate year of death using bomb pulse dating

When human remains are discovered, confirming the identification of the decedent is the first part of the forensic medical investigation. In cases where the remains are skeletonised or badly decomposed, differential preservation often increases the difficulty of this task. Bomb pulse dating, which directly compares levels of 14 C within human tissues to atmospheric levels, can provide an estimate of the year of death, which may assist in the identification process. This study measured the 14 C content in samples of hair, nail and puparia collected from donors at the Australian Facility for Taphonomic Experimental Research (AFTER). The radiocarbon results demonstrated that the nail samples provided the most accurate year of death estimation, with 91% correctly predicting YOD, closely followed by hair, with a 79% correct prediction rate, with both hair and nails having a lag time of 0-1 years. This is consistent with the time taken for atmospheric CO 2 to enter the food chain, and be taken in by humans. Puparia was found to have the highest levels of 14 C, and was the least consistent with the actual YOD (46% correct). However, predicted YOD ranges were still within 4 years of the actual YOD. Based on the results of this study, hair, nail and puparia should be considered as useful samples to obtain accurate estimates for YOD using bomb pulse dating.

Human Atherosclerotic Plaque Progression Is Dependent on Apoptosis According to Bomb-Pulse 14C Dating

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Individuals with rapidly progressing atherosclerotic plaques are at higher risk to experience acute complications. Using a ¹⁴C bomb-pulse dating method, we explored the importance of different biological components for the timeframe of plaque progression in human atherosclerosis.

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According to the ¹⁴C bomb-pulse dating method, increased apoptosis was the main component associated with a young physical plaque age, reflecting a rapid progression.

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Physically young atherosclerotic plaques also had more apoptotic cells and larger cores than physically old plaques.

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Our findings in combination with recent advances in imaging techniques could guide future diagnostic imaging strategies to identify rapidly progressing plaques or therapeutic targets, halting plaque progression.

Individuals with rapidly progressing atherosclerotic plaques are at higher risk of experiencing acute complications. Currently, we lack knowledge regarding factors in human plaque that cause rapid progression. Using the ¹⁴C bomb-pulse dating method, we assessed the physical age of atherosclerotic plaques and which biological processes were associated with rapidly progressing plaques. Interestingly, increased apoptosis was the main component associated with a young physical plaque age, reflecting rapid plaque progression. Our findings in combination with recent advances in imaging techniques could guide future diagnostic imaging strategies to identify rapidly progressing plaques or therapeutic targets, halting plaque progression.

A Review of Bomb Pulse Dating and its Use in the Investigation of Unidentified Human Remains

In cases where there is limited antemortem information, the examination of unidentified human remains as part of the investigation of long-term missing person's cases is a complex endeavor and consequently requires a multidisciplinary approach. Bomb pulse dating, which involves the analysis and interpretation of 14C concentration, is one technique that may assist in these investigations by providing an estimate of year of birth and year of death. This review examines the technique of bomb pulse dating and its use in the identification of differentially preserved unknown human remains. Research and case studies implementing bomb pulse dating have predominantly been undertaken in the Northern Hemisphere and have demonstrated reliable and accurate results. Limitations were, however, identified throughout the literature. These included the small sample sizes used in previous research/case studies which impacted on the statistical significance of the findings, as well as technique-specific issues. Such limitations highlight the need for future research.

14C BOMB-PULSE DATING AND STABLE ISOTOPE ANALYSIS FOR GROWTH RATE AND DIETARY INFORMATION IN BREAST CANCER?

The purpose of this study was to perform an initial investigation of the possibility to determine breast cancer growth rate with (14)C bomb-pulse dating. Tissues from 11 breast cancers, diagnosed in 1983, were retrieved from a regional biobank. The estimated average age of the majority of the samples overlapped the year of collection (1983) within 3σ Thus, this first study of tumour tissue has not yet demonstrated that (14)C bomb-pulse dating can obtain information on the growth of breast cancer. However, with further refinement, involving extraction of cell types and components, there is a possibility that fundamental knowledge of tumour biology might still be gained by the bomb-pulse technique. Additionally, δ (13)C and δ (15)N analyses were performed to obtain dietary and metabolic information, and to serve as a base for improvement of the age determination.

Cerebral aneurysms: formation, progression, and developmental chronology

The prevalence of unruptured intracranial aneurysms (UIAs) in the general population is up to 3%. Existing epidemiological data suggests that only a small fraction of UIAs progress towards rupture over the lifetime of an individual, but the surrogates for subsequent rupture and the natural history of UIAs are discussed very controversially at present. In case of rupture of an UIA, the case fatality is up to 50%, which therefore continues to stimulate interest in the pathogenesis of cerebral aneurysm formation and progression. Actual data on the chronological development of cerebral aneurysm has been especially difficult to obtain and, until recently, the existing knowledge in this respect is mainly derived from animal or mathematical models or short-term observational studies. Here, we review the current data on cerebral aneurysm formation and progression as well as a novel approach to investigate the developmental chronology of cerebral aneurysms.

Bomb-pulse 14C analysis combined with 13C and 15N measurements in blood serum from residents of Malmö, Sweden

The (14)C content of 60 human blood serum samples from residents of Malmö (Sweden) in 1978, obtained from a biobank, has been measured to estimate the accuracy of (14)C bomb-pulse dating. The difference between the date estimated using the Calibomb software and sampling date varied between -3 ± 0.4 and +0.2 ± 0.5 years. The average age deviation of all samples was -1.5 ± 0.7 years, with the delay between production and consumption of foodstuffs being probably the dominating cause. The potential influence of food habits on the (14)C date has been evaluated using stable isotope δ(13)C and δ(15)N analysis and information about the dietary habits of the investigated individuals. Although the group consisting of lacto-ovo vegetarians and vegans (pooled group) was not completely separated from the omnivores in a stable isotopic trophic level diagram, this analysis proved to add valuable information on probable dietary habits. The age deviation of the sampling date from the respective Calibomb date was found strongly correlated with the δ(13)C values, probably due to influence from marine diet components. For the omnivore individuals, there were indications of seasonal effects on δ(13)C and the age deviation. No significant correlation was found between the age deviation and the δ(15)N values of any dietary group. No influence of sex or year of birth was found on neither the (14)C nor the δ(13)C and δ(15)N values of the serum samples. The data were also divided into two groups (omnivores and pooled group), based on the level of δ(15)N in the samples. The consumption of high δ(15)N-valued fish and birds can be responsible for this clustering.

Carbon isotopes profiles of human whole blood, plasma, red blood cells, urine and feces for biological/biomedical 14C-accelerator mass spectrometry applications

Radiocarbon ((14)C) is an ideal tracer for in vivo human ADME (absorption, distribution, metabolism, elimination) and PBPK (physiological-based pharmacokinetic) studies. Living plants peferentially incorporate atmospheric (14)CO(2) versus (13)CO(2) versus (12)CO(2), which result in unique signature. Furthermore, plants and the food chains they support also have unique carbon isotope signatures. Humans, at the top of the food chain, consequently acquire isotopic concentrations in the tissues and body fluids depending on their dietary habits. In preparation of ADME and PBPK studies, 12 healthy subjects were recruited. The human baseline (specific to each individual and their diet) total carbon (TC) and carbon isotope (13)C (δ(13)C) and (14)C (F(m)) were quantified in whole blood (WB), plasma, washed red blood cell (RBC), urine, and feces. TC (mg of C/100 μL) in WB, plasma, RBC, urine, and feces were 11.0, 4.37, 7.57, 0.53, and 1.90, respectively. TC in WB, RBC, and feces was higher in men over women, P < 0.05. Mean δ(13)C were ranked low to high as follows: feces < WB = plasma = RBC = urine, P < 0.0001. δ(13)C was not affected by gender. Our analytic method shifted δ(13)C by only ±1.0 ‰ ensuring our F(m) measurements were accurate and precise. Mean F(m) were ranked low to high as follows: plasma = urine < WB = RBC = feces, P < 0.05. F(m) in feces was higher for men over women, P < 0.05. Only in WB, (14)C levels (F(m)) and TC were correlated with one another (r = 0.746, P < 0.01). Considering the lag time to incorporate atmospheric (14)C into plant foods (vegetarian) and or then into animal foods (nonvegetarian), the measured F(m) of WB in our population (recruited April 2009) was 1.0468 ± 0.0022 (mean ± SD), and the F(m) of WB matched the (extrapolated) atmospheric F(m) of 1.0477 in 2008. This study is important in presenting a procedure to determine a baseline for a study group for human ADME and PBPK studies using (14)C as a tracer.

Short Communication: Dating Components of Human Atherosclerotic Plaques

Rationale : Atherosclerotic plaques that give rise to acute clinical symptoms are typically characterized by degradation of the connective tissue and plaque rupture. Experimental studies have shown that mechanisms to repair vulnerable lesions exist, but the rate of remodeling of human plaque tissue has not been studied.

Objective : In the present study, we determined the biological age of different components of advanced human atherosclerotic plaques by analyzing tissue levels of 14 C released into the atmosphere during the nuclear weapons tests in the late 1950s and early 1960s.

Methods and Results : Atherosclerotic plaques were obtained from 10 patients (age 46 to 80 years) undergoing carotid surgery. Different regions of the plaques were dissected and analyzed for 14 C content using accelerator mass spectrometry. At the time of surgery, the mean biological age of the cap region was 6.4±3.2 years, which was significantly lower than that of the shoulder region (12.9±3.0 years, P <0.01), the interface toward the media (12.4±3.3 years, P <0.01), and the core (9.8±4.5 years, P <0.05). Analysis of proliferative activity and rate of apoptosis showed no signs of increased cellular turnover in the cap, suggesting that the lower 14 C content reflected a more recent time of formation.

Conclusions : These results show that the turnover time of human plaque tissue is very long and may explain why regression of atherosclerotic plaque size rarely is observed in cardiovascular intervention trials.

Accelerator mass spectrometry analysis of background (14)C-concentrations in human blood: aiming at reference data for further microdosing studies

OBJECTIVE

Phase 0 clinical studies, which are known as microdose trials, are expected to promote drug development and reduce development costs. The accelerator mass spectrometry (AMS) system is expected to play an important role in the microdosing tests, as it is a highly sensitive measurement system that can be used to determine the drug concentrations in these tests. Using the AMS system, we measured the background (14)C-concentration in human blood and evaluated the data for use as a reference in microdose studies that administer (14)C-labeled compounds in humans.

METHODS

Blood samples of five healthy Japanese volunteers (three men, two women, median age 40.4 +/- 9.8 years) were collected around the same time and just prior to when the subjects ate a meal (between 12:00 noon and 2:00 pm). Centrifugal separations of blood that was allowed to clot and the plasma were performed at 503 g for 2 min at 4 degrees C. Background (14)C-concentration for each of the samples was measured using the AMS system. The Institute of Accelerator Analysis, which is the first contract research organization in Japan that is capable of providing AMS analysis services for carbon dating and bioanalysis work, performed the AMS analysis.

RESULTS

The mean (14)C-concentration in blood was 1.613 +/- 0.125 dpm/ml (men 1.668 +/- 0.114 dpm/ml, women 1.514 +/- 0.076 dpm/ml), in clots 2.373 +/- 0.087 dpm/ml (men 2.381 +/- 0.101 dpm/ml, women 2.357 +/- 0.060 dpm/ ml), and in plasma 0.648 +/- 0.049 dpm/ml (men 0.647 +/- 0.059 dpm/ml, women 0.649 +/- 0.032 dpm/ml). The coefficient variation (CV) for blood was 7.8% (men 6.9%, women 5.0%), for clots 3.7% (men 4.3%, women 2.5%), and for plasma 7.6% (men 9.1%, women 4.9%). The (14)C-concentrations of the clot and blood were higher than those of plasma. The (14)C-concentrations in the blood and plasma were slightly different between individuals when compared with the values for the clot, although the differences were quite small, with a CV value less than 7.8%.

CONCLUSIONS

Even though the (14)C-concentration differed only slightly between individuals, (14)C-concentrations of the clot and blood were higher than those of the plasma. Therefore, the variation and difference of the background data for blood and plasma might be of use as a reference for microdosing test evaluations.