Human teeth as historical biomonitors of environmental and dietary lead: some lessons from isotopic studies of 19th and 20th century archival material

Antlers of European roe deer (Capreolus capreolus) as monitoring units to assess lead pollution in a floodplain contaminated by historical metal ore mining, processing, and smelting in the Harz Mountains, Germany

Lead concentrations in hard antlers of adult European roebucks (Capreolus capreolus) were analyzed to assess lead exposure of roe deer roaming the floodplain of the Innerste River, a river system contaminated due to historical metal ore mining, processing, and smelting in its upper reaches. Antler lead concentrations of roebucks culled in the period 1939-2018 within or close to the Innerste floodplain ranged between <0.17 mg Pb/kg (limit of detection) and 51.5 mg Pb/kg (air-dry weight). Median lead concentration in antlers of roebucks culled within the floodplain was 11.1 mg Pb/kg, compared to 2.3 mg Pb/kg in antlers of bucks culled in the floodplain vicinity (P < 0.01). Sampling year had no significant effect on antler lead concentrations (P = 0.748). Lead isotope ratios of antlers from the Innerste downstream area (²⁰⁶Pb/²⁰⁷Pb: 1.179-1.181; ²⁰⁸Pb/²⁰⁶Pb: 2.083-2.085) fell within the range of those reported for hydrothermal vein deposits from the upper catchment area of the Innerste River in the Harz Mountains. Our study demonstrates the long-lasting impact of the historical metal ore mining, processing, and smelting in the Harz Mountains on lead pollution in floodplains of rivers draining this area and the lead exposure of wild herbivores inhabiting the floodplains. Furthermore, it highlights the suitability of roe deer antlers for monitoring environmental lead levels and the usefulness of lead isotope signatures in antlers for source apportionment of lead pollution.

The potential of trace elements mapping in child's natal tooth by laser ablation-ICPMS method

PURPOSE

Tooth enamel might provide past chronological metabolic, nutritional status and trace metal exposure during development. Thus, the trace elements distribution embedded in tooth tissues represents an archive of the environmental conditions. The choice of biomarker is estimated as critical to the measurement of metal exposure. Natal teeth are defined as teeth being present at birth.

METHODS

LA-ICP-MS provides a quantitative assessment of spatial distribution of trace elements in a natal tooth. The objective of the current study was to compare concentrations of building and other elements in a rare but reliable and valid biomarker - natal tooth.

RESULTS

It have been reported presence of potentially toxic elements: Pb, Cu, Mn, Cd, Ni distributed in prenatally and perinatally formed enamel and dentine.

CONCLUSIONS

Analyses of deciduous enamel can provide answers into individuals' earliest development, including critical pre- and perinatal period.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40201-021-00611-2.

Forensic isoscapes based on intra-individual temporal variation of δ 18O and 206Pb/207Pb in human teeth

Isotopic signatures used in the georeferencing of human remains are largely fixed by spatially distinct geologic and environmental processes. However, location-dependent temporal changes in these isotope ratios should also be considered when determining an individual's provenance and/or trajectory. Distributions of the relevant isotopes can be impacted by predictable external factors such as climate change, delocalisation of food and water sources and changes in sources and uses of metals. Using Multi-Collector Inductively-Coupled Plasma Mass Spectrometer (MC-ICP-MS) analyses of ²⁰⁶Pb/²⁰⁷Pb in tooth enamel and dentin from a population of 21 ± 1-year-old individuals born circa 1984 and isotope ratio mass spectrometry (IRMS) of δ ¹⁸O in their enamel, we examined the expected influence of some of these factors. The resulting adjustments to the geographic distribution of isotope ratios (isoscapes) found in tooth enamel and dentin may contain additional useful information for forensic identification, but the shifts in values can also impact the uncertainty and usefulness of identifications if they are not taken into account.KEY POINTSIsoscapes of ²⁰⁶Pb/²⁰⁷Pb and δ ¹⁸O used for geolocation are not static.Within a few years, the enamel and dentin of a person may exhibit measurable differences in ²⁰⁶Pb/²⁰⁷Pb even without changing locations.Changes in climatic patterns tied to rising temperatures are more significant than the direct effect of increasing temperature on δ ¹⁸O fixed in tooth bioapatite.Third molar (M3) enamel mineralisation includes material incorporated from before formal amelogenesis takes place.

Tracing fetal and childhood exposure to lead using isotope analysis of deciduous teeth

We report progress in using the isotopic composition and concentration of Pb in the dentine and enamel of deciduous teeth to provide a high resolution time frame of exposure to Pb during fetal development and early childhood. Isotope measurements (total Pb and (208)Pb/(206)Pb, (207)Pb/(206)Pb ratios) were acquired by laser ablation inductively coupled mass spectrometry at contiguous 100 micron intervals across thin sections of the teeth; from the outer enamel surface to the pulp cavity. Teeth samples (n=10) were selected from two cohorts of children, aged 5-8 years, living in NE England. By integrating the isotope data with histological analysis of the teeth, using the daily incremental lines in dentine, we were able to assign true estimated ages to each ablation point (first 2-3 years for molars, first 1-2 years for incisors+pre-natal growth). Significant differences were observed in the isotope composition and concentration of Pb between children, reflecting differences in the timing and sources of exposure during early childhood. Those born in 2000, after the withdrawal of leaded petrol in 1999, have the lowest dentine Pb levels (<0.2µgPb/g) with (208)Pb/(206)Pb (mean ±2σ: 2.126-2.079) (208)Pb/(206)Pb (mean ±2σ: 0.879-0.856) ratios that correlate very closely with modern day Western European industrial aerosols (PM10, PM2.5) suggesting that diffuse airborne pollution was probably the primary source and exposure pathway. Legacy lead, if present, is insignificant. For those born in 1997, dentine lead levels are typically higher (>0.4µgPb/g) with (208)Pb/(206)Pb (mean ±2σ: 2.145-2.117) (208)Pb/(206)Pb (mean ±2σ: 0.898-0.882) ratios that can be modelled as a binary mix between industrial aerosols and leaded petrol emissions. Short duration, high intensity exposure events (1-2 months) were readily identified, together with evidence that dentine provides a good proxy for childhood changes in the isotope composition of blood Pb. Our pilot study confirms that laser ablation Pb isotope analysis of deciduous teeth, when carried out in conjunction with histological analysis, permits a reconstruction of the timing, duration and source of exposure to Pb during early childhood. With further development, this approach has the potential to study larger cohorts and appraise environments where the levels of exposure to Pb are much higher.

Effects of motor vehicle exhaust on male reproductive function and associated proteins

Air pollution is consistently associated with various diseases and subsequent death among children, adult, and elderly people worldwide. Motor vehicle exhaust contributes to a large proportion of the air pollution present. The motor vehicle exhaust systems emit a variety of toxic components, including carbon monoxide, nitrogen oxides, volatile organic compounds, ozone, particulate matter, and polycyclic aromatic hydrocarbons. Several epidemiological studies and laboratory studies have demonstrated that these components are potentially mutagenic, carcinogenic, and endocrine disrupting agents. However, their impact on male reproductive function and associated proteins is not very clear. Therefore, a comprehensive review on the effects of motor vehicle exhaust on male reproductive function and associated proteins is needed to better understand the risks of exhaust exposure for men. We found that motor vehicle exhaust can cause harmful effects on male reproductive functions by altering organ weights, reducing the spermatozoa qualities, and inducing oxidative stress. Remarkably, motor vehicle exhaust exposure causes significant changes in the expression patterns of proteins that are key components involved in spermatogenesis and testosterone synthesis. In conclusion, this review helps to describe the risks of vehicle exhaust exposure and its relationship to potential adverse effects on the male reproduction system.

Proposed toxic and hypoxic impairment of a brainstem locus in autism

Electrophysiological findings implicate site-specific impairment of the nucleus tractus solitarius (NTS) in autism. This invites hypothetical consideration of a large role for this small brainstem structure as the basis for seemingly disjointed behavioral and somatic features of autism. The NTS is the brain's point of entry for visceral afference, its relay for vagal reflexes, and its integration center for autonomic control of circulatory, immunological, gastrointestinal, and laryngeal function. The NTS facilitates normal cerebrovascular perfusion, and is the seminal point for an ascending noradrenergic system that modulates many complex behaviors. Microvascular configuration predisposes the NTS to focal hypoxia. A subregion--the "pNTS"--permits exposure to all blood-borne neurotoxins, including those that do not readily transit the blood-brain barrier. Impairment of acetylcholinesterase (mercury and cadmium cations, nitrates/nitrites, organophosphates, monosodium glutamate), competition for hemoglobin (carbon monoxide, nitrates/nitrites), and higher blood viscosity (net systemic oxidative stress) are suggested to potentiate microcirculatory insufficiency of the NTS, and thus autism.

Toxicological status of children with autism vs. neurotypical children and the association with autism severity

This study investigates both the level of toxic metals in children with autism and the possible association of those toxic metals with autism severity. This study involved 55 children with autism ages 5-16 years compared to 44 controls with similar age and gender. The study included measurements of toxic metals in whole blood, red blood cells (RBC), and urine. The autism group had higher levels of lead in RBC (+41 %, p = 0.002) and higher urinary levels of lead (+74 %, p = 0.02), thallium (+77 %, p = 0.0001), tin (+115 %, p = 0.01), and tungsten (+44 %, p = 0.00005). However, the autism group had slightly lower levels of cadmium in whole blood (-19 %, p = 0.003). A stepwise, multiple linear regression analysis found a strong association of levels of toxic metals with variation in the degree of severity of autism for all the severity scales (adjusted R(2) of 0.38-0.47, p < 0.0003). Cadmium (whole blood) and mercury (whole blood and RBC) were the most consistently significant variables. Overall, children with autism have higher average levels of several toxic metals, and levels of several toxic metals are strongly associated with variations in the severity of autism for all three of the autism severity scales investigated.

Reconstructing the life-time lead exposure in children using dentine in deciduous teeth

Data are presented to demonstrate that the circumpulpal dentine of deciduous teeth can be used to reconstruct a detailed record of childhood exposure to lead. By combining high spatial resolution laser ablation ICP-MS with dental histology, information was acquired on the concentration of lead in dentine from in utero to several years after birth, using a true time template of dentine growth. Time corrected lead analyses for pairs of deciduous molars confirmed that between-tooth variation for the same child was negligible and that meaningful exposure histories can be obtained from a single, multi-point ablation transect on longitudinal sections of individual teeth. For a laser beam of 100 μm diameter, the lead signal for each ablation point represented a time span of 42 days. Simultaneous analyses for Sr, Zn and Mg suggest that the incorporation of Pb into dentine (carbonated apatite) is most likely controlled by nanocrystal growth mechanisms. The study also highlights the importance of discriminating between primary and secondary dentine and the dangers of translating lead analyses into blood lead estimates without determining the age or duration of dentine sampled. Further work is in progress to validate deciduous teeth as blood lead biomarkers.

Stable lead isotopes in environmental health with emphasis on human investigations

There has been widespread use of stable lead isotopes in the earth sciences for more than 40 years focussed on the origin and age of rocks and minerals with lesser application in environmental investigations where the emphasis has been directed typically to the source of lead in environmental media such as air, water and soils. In contrast, the number of environmental health investigations focussed on humans (and primates) is limited in spite of the demonstrated utility of the approach in pioneering studies in the early 1970's. This paper reviews the status of lead isotopes in human investigations especially over the past 2 decades, the period over which most activity has taken place. Following a brief introduction to the method, examples are provided illustrating the use of lead isotopes in a wide spectrum of activities including sources and pathways of lead in diverse environments from urban to mining communities, various applications associated with pregnancy, the contribution of bone lead to blood lead including in the elderly, the half-life of lead in blood, and lead in bones and other media. A brief outline of critical research on non-human primates is also given. The lead isotope method is a powerful technique for tracing lead and could be employed more widely in human investigations.

Assessment of the FDA Backgrounder on Platinum in Silicone Breast Implants: Implications for Public Health Policy

A recent report by the U.S. Food and Drug Administration reviewed the literature on the subject of platinum in silicone gel–filled breast implants. In this study the author evaluates the FDA report for scientific accuracy and impartiality, and provides relevant discussions on financial conflicts of interest, an Institute of Medicine report, and public health policy. The study suggests that the FDA used discredited scientific practices in compiling its report. Reports by regulatory agencies should be scientifically accurate, with no partiality to industry. The current policy of one-way information flow from the FDA directly to those being informed needs to be revised. Greater importance should be placed on studies in which authors have no financial conflicts of interest.

A lead isotopic assessment of tree bark as a biomonitor of contemporary atmospheric lead

The outermost bark layer of trees, predominantly Scots pine (Pinus sylvestris), was sampled at 82 non-urban locations from six arbitrarily designated areas (Northwest, Northeast, Central Highlands, Central and East, Central and Southwest, Southeast), throughout Scotland during 2002-2003 and analysed for lead concentration and stable lead isotopes by flame atomic absorption spectrometry (AAS) and inductively coupled plasma-mass spectrometry (ICP-MS), respectively. The mean lead concentration and mean (206)Pb/(207)Pb ratio (+/-1 standard deviation, SD) for bark samples from the areas were as follows: Northwest (8.0 mg kg(-1), 1.121+/-0.014, n=17), Northeast (8.9 mg kg(-1), 1.117+/-0.012, n=12), Central Highlands (11.3 mg kg(-1), 1.130+/-0.010, n=11), Central and East (35.3 mg kg(-1), 1.120+/-0.007, n=10), Central and Southwest (20.6 mg kg(-1), 1.125+/-0.018, n=22) and Southeast (34.4 mg kg(-1), 1.120+/-0.005, n=10), with an overall mean lead concentration of 18.5 mg kg(-1) (range 0.6-146 mg kg(-1), median 8.4 mg kg(-1)) and an overall mean (206)Pb/(207)Pb ratio of 1.122+/-0.014 (range 1.089-1.168, median 1.122). The overall mean (206)Pb/(207)Pb ratio for bark was therefore significantly lower (p<0.01, t test) than the mean atmospheric (206)Pb/(207)Pb ratio of 1.154+/-0.006 (range 1.144-1.167, n=50) and 1.154+/-0.010 (range 1.134-1.171, n=26) as determined in rainwater collected routinely at Glensaugh, Central Highlands, during 2002 and 2003, respectively. The bark (206)Pb/(207)Pb values, 90% of which lay between 1.10 and 1.14, were more akin to those recorded for the atmosphere (via rainwater, atmospheric particulates, moss, etc.) at various locations throughout Scotland during the 1990s, a decade over which the use of leaded petrol (mean (206)Pb/(207)Pb ratio=1.076+/-0.011) declined markedly before its complete withdrawal in 2000. This strongly suggests that the lead content and isotopic composition of tree bark from Scots pine, which reputedly sheds its outer layers every couple of years or so, reflect exposure to atmospherically deposited lead (in the atmosphere or soil) over a much longer time period than just the previous 2-3 years of exposure to contemporary atmospheric lead. The possible influence of soil lead upon tree bark through external attachment was not observed in a comparative sub-set study of 27 paired bark (mean (206)Pb/(207)Pb ratio=1.122+/-0.016) and surface (0-2 cm) soil (mean (206)Pb/(207)Pb ratio=1.145+/-0.022) samples, in only six cases (i.e. 22%) of which did the corresponding (206)Pb/(207)Pb ratios agree within +/-2 SD. Likewise, bark (206)Pb/(207)Pb values exhibited no discernible trend with distance from the nearest road, with similar average values for 0-20 m (1.123+/-0.015, n=34) and 20-700 m (1.122+/-0.012, n=48), although the corresponding mean (and median) lead concentration of 23.5 (10) mg kg(-1) vs. 14.9 (7.5) mg kg(-1) was slightly higher for the former. The influence of airborne dusts from waste deposits related to former mining/smelting of Wanlockhead/Leadhills lead ores ((206)Pb/(207)Pb=1.170+/-0.003) could be seen, however, in the sycamore bark lead concentrations of up to 3050 mg kg(-1) and (206)Pb/(207)Pb ratios (1.168-1.171) observed at a distance of 0.5 km away.