# Earliest evidence for heavy metal pollution on wildlife in Middle Age Europe

M. Robu, I.-C. Mirea, D. Veres, S. Olive, M. Vlaicu, P. Telouk, J.E. Martin

► To cite this version:

M. Robu, I.-C. Mirea, D. Veres, S. Olive, M. Vlaicu, et al. Earliest evidence for heavy metal pollution on wildlife in Middle Age Europe. Environmental Pollution, 2025, 368, pp.125766. 10.1016/j.envpol.2025.125766. hal-05166152

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# Earliest evidence for heavy metal pollution on wildlife in Middle Age Europe☆

M. Robu<sup>a,b,**,1</sup>, I.-C. Mirea<sup>c</sup>, D. Veres<sup>d</sup>, S. Olive<sup>e,f,g</sup>, M. Vlaicu<sup>a</sup>, P. Telouk<sup>g</sup>, J.E. Martin<sup>g,**,1</sup> ◐

<figure><img src="image_2.png" /></figure>

## ARTICLE INFO

Keywords:

Subfossil teeth

Lead concentration

brown bear

Anthropogenic pollution

Laser ablation

## ABSTRACT

Effects of past anthropogenic metal pollution on the wildlife are understudied. We investigate trace element incorporation in the dentition of a 1000 BP-year-old brown bear from the Romanian Carpathians, an area known historically for strong metallurgical activities. Background values as well as unnatural high lead (Pb), lithium (Li) and zinc (Zn) levels in a circa 5-6-year-old brown bear male were detected using trace element maps across its functional dentition. High-resolution elemental transects and histological sections reveal the seasonal extent of lead intake, which occurred during five recorded summers, i.e. when the animal was actively foraging. We interpret the elevated Pb, Li and Zn concentrations in the terminal growth lines as evidence for the earliest-known anthropogenic heavy metal pollution in a wild animal. Our study underlines the impact of early industrial activities in a large terrestrial omnivore, demonstrating that anthropogenic threats on wildlife were not solely driven by hunting or landscape modification during the most recent decades.

## 1. Introduction

The early exploitation of ore deposits and improvements in the refinement of metals were of fundamental importance in the subsequent technological development of humanity (Killick and Fenn, 2012). Evidence of intentional thermal treatment of ores to produce metals and complex metalworking already by 5000 BCE (Radivojević et al., 2010) has been uncovered in several places throughout the Balkans (Pernicka et al., 1993; Radivojević et al., 2013; Radivojević and Rehren, 2016) and in the Middle East (Roberts et al., 2009). The rich archaeological heritage of the Carpathian-Balkan region includes the earliest known sites of mining and extractive metallurgy in Europe, and recent research has shown that major metal pollution from 600 BCE onward occurred in the

Balkans, with gradually increasing values in anthropogenic metals until a peak at ca. 1620 CE (Longman et al., 2018).

One of the most common heavy metals, lead (Pb), thanks to its plasticity and softness, is used from ancient times as a component for a diverse range of products (e.g., pots, bullets, coins, weights, pipes, roofs). The exploitation of such mineral resources has a broad range of environmental impacts, including metal-contaminated wastewater and biomass, release of chemical particles into the atmosphere (More et al., 2017), and the use of toxic metals in tools (Dudka and Adriano, 1997; Csavina et al., 2012; Delile et al., 2014). The effects of highly toxic lead poisoning were documented on the broader ecosystem (Hoffman et al., 2003) and on human health during the past two millennia (Hernberg, 2000). Plants can accumulate lead in those parts considered edible for

<footnote><sup>a</sup> “Emil Racoviţă” Institute of Speleology, Department of Karstology, Karst Inventory and Cave Protection, Bucharest, Romania</footnote>

<footnote><sup>b</sup> Research Institute of the University of Bucharest, The Earth, Environmental and Life Sciences Division, 1 B.P. Haşdeu St., 50567, Bucharest, Romania</footnote>

<footnote><sup>c</sup> “Emil Racoviţă” Institute of Speleology, Department of Geospeleology and Paleontology, Bucharest, Romania</footnote>

<footnote><sup>d</sup> Romanian Academy, Institute of Speleology, Cluj-Napoca, Romania</footnote>

<footnote><sup>e</sup> Institute of Natural Sciences, Directorate Earth & History of Life, Palaeobiosphere Evolution, Rue Vautier 29, 1000, Brussels, Belgium</footnote>

<footnote><sup>f</sup> Université de Liège, Freshwater and Oceanic Science Unit of Research, Laboratory of Ecology and Conservation of Amphibians, Quai Van Beneden, 22, 4020, Liège, Belgium</footnote>

<footnote><sup>g</sup> Université de Lyon, UCBL, ENSL, CNRS, UMR, 5276 LGL-TPE, 69622, Villeurbanne, France</footnote>

<footnote>* This paper has been recommended for acceptance by Philip N. Smith.</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>** Corresponding author. "Emil Racoviţă" Institute of Speleology, Department of Karstology, Karst Inventory and Cave Protection, Bucharest, Romania. E-mail addresses: marius.robu@iser.ro (M. Robu), jeremy.martin@cnrs.fr (J.E. Martin).</footnote>

<footnote n="1">¹ These authors contributed equally to this work.</footnote>
herbivores and humans, which still jeopardizes health security in many parts of the world. Anthropogenic pollution is directly responsible for increases in the concentration of Pb in the air, waters, and food chains, with ingestion and inhalation being the most significant routes of exposure to Pb in terrestrial animals and humans (Kierdorf et al., 2000; Baranowska-Bosiacka and Chlubek, 2006; 2019; Reglero et al., 2008). In biological tissues (e.g., bones), the anthropogenic lead is usually found associated with elements like zinc (Zn), lithium (Li), copper (Cu), or barium (Ba) (Kohn et al., 2013). An important factor affecting the concentration of Pb in bones is exposure time. Short-term exposure leading even to deadly lead poisoning may not be recorded in bones or teeth. Regulation (EU) 2023/915 sets maximum levels for lead between 0.01 mg/kg (0.1 ppm; e.g., baby foods) and 3 mg/kg (3 ppm) in food supplements. In meat products, fats, and oils the lead levels should not exceed more than 0.1 mg/kg of lead (0.1 ppm); the fruits, vegetables, and fungi are acceptable between 0.1 mg/kg – 0.8 mg/kg of lead (0.1–0.8 ppm). Toxic effects of lead must have been present in animals in the past, as is indicated by contemporary studies of domestic animals exposed to lead metallurgical emissions (Liu, 2003). A baseline of the lead content in mammal dentine, from a virtually non-anthropologically polluted period (e.g., Late Pleistocene), sets an average of 0.1–0.3 ppm for Pb concentration in a mammoth molar (Anczkiewicz et al., 2023). Other trace-elements like Li or Zn are recorded in the ranges of 1 ppm and 10–1000 ppm, respectively, according to Kohn et al. (2013). The

same authors reported distinctly higher Pb concentrations in Idaho's modern brown bears (around 10 ppm) than in herbivore mammals (around 0.1 ppm). However, given that specimens were collected during 2007, such data from the wildlife are likely to reflect the effects of contemporaneous anthropogenic metal pollution (e.g., Kohn et al., 2013; Brown et al., 2022). Historically, the impact of metal pollution is expected to have affected wild biota through the same processes but has never been assessed for areas close to early metallurgic centers. In this respect, geochemical proxies such as trace elements, recorded in tooth incremental tissues (Trueman and Tuross, 2002), allow the detection of heavy metal ingestion during the lifetime of an organism. Heavy metals, such as Pb, are released into the atmosphere through mining and smelting. Once deposited, they can be preserved on a long-term in sedimentary records (peat or lake sediments), or ingested by animals. As such, heavy metals can be used as proxies for reconstructing historical pollution across a region, during a given time (Hoffman et al., 2003).

Here, we report on the occurrence of abnormally high levels of heavy metals (Pb, Zn) recorded in the teeth of a subfossil wild brown bear from the Mehedinți Mountains, Romania, and discuss their significance for investigating the role of anthropogenic pollution on past environment and megafaunal assemblages.

<figure><img src="image_3.png" /><figcaption>**Fig. 1.** Context of the discovery of a subfossil brown bear with evidence of anthropogenic Pb pollution. (A) Geographical location of the ACCG site and closest medieval metallurgical centers/mines. 1: ACCG (Avenul nr. 2 din Cracul de la Cioaca Goală); 2: Moldova Nouă; 3: Varad; 4: Nera; 5: Sasca Română; 6: Dognecea; 7: Surducu Mare; 8: Tişoviţa; 9: OgradenaVeche; 10: Eibenthal; 11: Slatina; 12: Maidan; 13: Marga; 14: Rudna Glava; 15: Belovode; 16: Bor; 17: Madjanpek. The red polygon from ACCG site indicates the brown bear potential movement area (40 km²) estimated for this species by Pop et al. (2018); (B) ACCG site and the taphonomic context of the Cl/010 mandible (2011); (C) Right medial view of the studied brown bear mandible (Cl/010); (D) Calibrated radiocarbon ages for the three sampled brown bears. The red color corresponds to Cl/010 sample. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)</figcaption></figure>
## 2. Materials and methods

### 2.1. Samples

The subfossil brown bear remains were discovered in 2011, in Ave-
nul 2 locality from Cracul de la Cioaca Goală (thereafter, ACCG; Fig. 1).
This is a *ca.* 48 m vertical-horizontal cave situated in the Vârtoape
Plateau of the Motrul Sec River basin, Mehedinți Mountains, Romania.
The Banat - Oltenia region (Romania) is known for its medieval tradi-
tion (and even pre-Roman; e.g., Vărad, Nera mines, Baia de Aramă;
Fig. 1A) in extracting heavy and base metals, smelting and alloying. The
development of mining and metallurgy of silver and lead, in the Banat
region (30-70 km, westward, from the sampling site) is recorded from
600 BCE until ~1620 CE (Longman et al., 2018).

The cave entrance is a 20 m-deep shaft, while the rest of the cave has
horizontal and near-horizontal passages. The karstic plateau is part of the
Gorganu-Piatra Cloșanilor limestone cover (Robu, 2009) of the
Danubian Autochthonous nappe and is defined by intense karst pro-
cesses and a large diversity of endo- and exo-karst landforms (Fig. 1A).
At the time of field sampling (2011), the taphonomic context of the cave
was undisturbed, with no trace of recent human activity, no archaeo-
logical evidences and no guano deposition recorded (Fig. 1B). The bone
remains of three brown bear individuals [one sub-adult female (Cl/008),
a juvenile (Cl/009) and a sub-adult male (Cl/010)] were found close to
the shaft bottom, identified and partially collected (Ersmark et al.,
2019). For reasons of specimen conservation, lab instruments avail-
ability and costs, only the right side of the mandible of Cl/010 specimen
was submitted to analyses. Moreover, Cl/008 and Cl/009 specimens
show traces of carnivore consumption on their skeletal elements. Sam-
pling the mandibles of these other two specimens would irremediably
have altered their taphonomic information.

### 2.2. Radiocarbon analysis

AMS ¹⁴C dating was commercially performed on sample Cl/010 at the Poznan Radiocarbon Laboratory (Poland). Analytical procedures were described by Longin (1971) and modified by Piotrowska and Goslar (2002). The bone treatment followed the method described by Piotrowska and Goslar (2002) and Brock et al. (2010), including the collagen extraction, purification (using Elkay 8 µm filters) and ultrafiltra- tration (Vivaspin 15 MWCO 30 kd filters). All radiocarbon data used here was calibrated using the OxCal v4.4.2 software (Brock et al., 2010; Bronk Ramsey, 2009; Reimer et al., 2020) against the INTCAL13 radiocarbon calibration curve (Reimer et al., 2020). Moreover, available results from radiometric dating of the studied MIS 1 brown bears, pre- viously published (Ersmark et al., 2019; N = 2), were added to our data. The female and the cub were subsequently radiocarbon dated to ca. 1000 cal yr BP (Ersmark et al., 2019) (Fig. 1D; Table S1). The male's skull and hemi-mandibles were found on the cave floor along with other brown bear bones, having the same stratigraphy with the other two bears' skeletons, partially buried by the cave sediment, and partially exposed (Fig. 1B).

### 2.3. Histology

To determine the age at death, one thin section per tooth (N = 5) was
made for all right-side hemi-mandible teeth (canine, p4–m3; Fig. 1C).
Teeth were cut in the middle from the apex to the root along a mesio-
distal transect. One half was dedicated to thin section while the other
half of the tooth was dedicated for laser ablation mapping (see below).
Thin sections were photographed at high resolution under natural light.
Both cementum and dentine tissues were analyzed in this respect for all
teeth (c–m3 dental line).

### 2.4. Laser ablation Pb concentration maps

We provide detailed trace element maps (N = 5) and high resolution
transects (N<sub>transects</sub> = 10; 1180 measurements) for ²⁰⁸Pb, for the
analyzed teeth, using an Excimer laser ablation system coupled to a
quadrupole ICP mass spectrometer (Thermo-Fischer ICAP TQ; Figs. 2
and 4. Tables S2–S3) at ENS de Lyon (LGLTPE, UMR CNRS 5276).
Acquisition parameters for the laser output correspond to a fluence of 6
J/cm, a repetition rate of 50 Hz, a spot diameter of 80 µm and a speed of
150 µm/s. Blank levels were measured for 20 s at the beginning of each
map. The standard NBS 610 was repeatedly measured and used as a
reference to calculate the lead concentrations. As the dentin provides a
permanent, cumulative, macroscopic and solid record of past and/or
recent heavy metal environmental exposure (Robu et al., 2019), we
focused on analyzing this tissue.

## 3. Results

### 3.1. Age of the individual and season of death

The radiocarbon age of the Cl/010 right side of the mandible (teeth present: canine, fourth premolar, first, second and third molars) places it between 993–1241 yrs cal BP (=710–957.5 yrs cal CE; 95.4% confidence) and between 963–1262 yrs cal BP (=689–987.5 yrs cal CE; 99.7% confidence), with a median age of 1160 ± 51 yrs cal BP (=845 yrs cal CE; Fig. 1D; Table S1). Moreover, the obtained radiometric age is in agreement with the taphonomy and with the previous radiocarbon data obtained for two other associated brown bears (1078 ± 55 yrs cal BP for Cl/008 and 1017 ± 32 yrs cal BP for Cl/009; Ersmark et al., 2019).

The age at death assessment, for both the dentine and cementum of the subadult male specimen (Cl/010) varies between ca. 5½ – 6½ years old, depending on the analyzed tooth and on its eruption period (Fig. 2). Given the eruption timing for bears' lower teeth, we focused on the age assessment of the lower first molar (m₁) and the lower fourth premolar, p₄ as they are the first to appear.

For the m₁, five dark layers (A = 5; attributed to winter denning; Fig. 2) and five annual light layers (LC = 5; corresponding to spring summer–early fall season) were identified within the cementum tissues, while 6 white and black intervals were identified for dentine. For p₄ cementum, we identified five annual dark layers (A = 5) and six annual light layers (LC = 6), while for dentine, six black and six white layers were identified. As the last cementum layers to be deposited, for all analyzed teeth, were light (LC layers), we estimate that the animal died before the denning season, most probably during the early fall period.

### 3.2. Anomaly in lead content in the dentition of a wild brown bear

The recorded ²⁰⁸Pb variation is clearly corresponding to the dentin
layers (Figs. 2–5). Based on the high resolution ²⁰⁸Pb maps and transects
(Figs. 2 and 4: C-C' and D-D' transects), for the lower fourth premolar
(p4) five lead peaks-trough cycles were identified within the dentine
tissue. Fig. 2 indicates the direct correspondence between the ²⁰⁸Pb
peaks and the dentine light layers [LL; assumed to roughly reflect the
summer season; S1-S5], whereas the ²⁰⁸Pb troughs are corresponding to
the dark layers [DL; assumed to roughly reflect the denning period, the
winter (Rausch, 1969); W2-W6]. These results fall within the seasonal
variation of Pb intake from natural and/or polluted sources during the
activity period (late spring–early fall; roughly summer) and lower Pb
values during the denning period (late fall–early spring; roughly
winter). For this reason, it is not possible to determine whether the wild
bear experienced Pb pollution for the first four years of its life.
Accordingly, the ²⁰⁸Pb peaks-trough cycles (N = 5) were also identified
within the dentin of the other analyzed teeth (Fig. 4). The values ob-
tained for analyzed teeth varies between 0 and 15.2 ppm, the latter
value being anomalous for a natural environment and indicates that the
<figure><img src="image_4.png" /><figcaption>**Fig. 2.** Thin sections, age estimation (cementum and dentin) and ²⁰⁸Pb distribution across tooth sections in a single bear individual (Cl/010) from the AACG site. Cementum and dentine areas magnified for skeleto-chronological purpose are indicated by a black square and by a red square, respectively. Teeth are sorted by eruption order from top to bottom in the display figure. The pink square on the canine corresponds to the magnified area that produced the corresponding ²⁰⁸Pb laser map. All other ²⁰⁸Pb laser maps were conducted on whole teeth. Abbreviations: C: cementum; D: dentine; c: canine; p₄: fourth premolar; m₁: first molar; m₂: second molar; m₃: third molar; A: annulus (LAG; dark cementum layer); LC: light cementum layer; DCJ: dentine-cementum junction; ARC: apical root canal; DL: annual dentine layers (dark + light dentine). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)</figcaption></figure>
<figure><img src="image_5.png" /><figcaption>Fig. 3. The intra-tooth record of Pb is controlled by the foraging activities of the bear, as shown here with seasonal peaks in lead incorporated during the summer months. (A) concentration map of $^{208}$Pb across the brown bear P$_{4}$ thin section (D–D’: $^{208}$Pb transect cementum-dentine of the anterior root); (B) variations in $^{208}$Pb concentration along the D-D’ transect superimposed on the thin section (under natural light) of the anterior root. Abbreviations: C: cementum; D: dentine; DCJ: dentine-cementum junction. ARC: apical root canal; S1–S5: first summer–fifth summer; W2–W6: second winter–sixth winter. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)</figcaption></figure>

wild bear recorded Pb pollution at least at the end of its life. The $^{208}$Pb “peaks” (related to the LLs) vary from 1.5 to 6.1 ppm, for $p_{4}$, and from 2.2 to 15.2 ppm, for $m_{1}$. On the other hand, the $^{208}$Pb troughs (related to the DLs) vary from 0.5 to 2 ppm for $p_{4}$ and from 0.3 to 2 ppm, for $m_{1}$. The alternance of high and low $^{208}$Pb values recorded into the dentine layers may indicate a seasonal variation of natural lead intake during the life of the studied brown bear individual. Excepting the canine, the maximum concentration of lead is recorded for the last year of life, within the last dentin layers for all analyzed teeth, roughly displaying a growing pattern, from the first active season towards the last (Fig. 4). Moreover, additional $^{64}$Zn and $^{7}$Li data (Fig. 5; Tables S4–S5) represented as maps of the analyzed brown bear teeth, support the anthropogenic pollution scenario being associated with the anomalous metal concentration in the last dentine layer (sensu Kohn et al., 2013). The $^{64}$Zn data [(m$_{1}$ – min: 1.68 ppm; max: 707.27 ppm; average: 226.94 ppm – E-E' transect; Table S4); (p$_{4}$ – min: 1.32 ppm; max: 728.70 ppm; average: 155.66 ppm – D-D' transect)] are ten-fold when compared to the data recorded for the woolly mammoth (Anczkiewicz et al., 2023), set as a baseline.

4. Discussion

Given their denning behavior involving low metabolic activity, the
mineralized record of bear teeth are ideal candidates to test for the
seasonality of environmental geochemical proxies. The alternating high
and low $^{208}$Pb levels recorded for the Cl/010 teeth dentine, implies that
the Pb intake is correlated with the biological and physiological activ-
ities of the bear, during the late spring–late fall period. Histologically,
our study confirms that during the denning period (late fall–early
spring; hibernation/denning period), the Pb intake was minimal, while
during the spring–late fall period, the high Pb values observed originate
from food, water drinking and air intake (Fig. 2–5). As a reference of Pb

poisoning levels, for humans, the neurotoxic effects are liable to occur
above a Pb concentration of 5 ppm in dentine and 2.4 µM/1 (50µg/100
ml) in blood (Hernberg, 2000). Therefore, during the last biological
active summer season, Pb peak value reaching 15.2 ppm indicates a high
level of unnatural Pb intake that is interpreted here as anthropogenic
pollution. This fact suggests similar effects upon the general state of
bear’s health as in humans (high levels of Pb intake is a stressing factor
for the animal’s physiology and a limitation for life expectancy).

The cause of death for the analyzed brown bear was linked to a pitfall
and entrapment as the entrance in this site is a *ca.* 20 m vertical shaft,
without any possibility of climbing out. However, we do not exclude that
the high Pb content might have affected the general bear’s health and
behavior. Moreover, in contexts with serious anthropogenic pollution
with Pb and other associated heavy metals (e.g., Zn), it is expected that
the lifespan to be very low compared to natural conditions (i.e. in natural
parks; 15–20 years life expectancy for the present-day Romanian brown
bears; Kalabér et al., 1994). Here, the young age at death of the indi-
vidual could lend support to the Pb intoxication hypothesis.

The brown bear Cl/010 lived during a period with increased
anthropogenic fire activity and high Pb contribution during the Early
Middle Ages, as previous research showed for the Crveni Potok peat
record, in Serbia (Longman et al., 2018). Moreover, the increase in Pb
emissions in the atmosphere associated with the production of this metal
in the 11th and 12th centuries in Central and Eastern Europe was pre-
viously reported (Cabala et al., 2022). The development of mining and
metallurgy of silver and lead, in the Banat region (30–70 km, westward,
from the ACCG site), resulted in the pollution of mining and processing
areas with lead and other heavy metals (Zn, Li, Cd, Fe and Mn)
(Longman et al., 2024). The region is known for its medieval tradition
(and even pre-roman; e.g., Várad, Nera mines; Fig. 1A) in heavy and
base metals’ extraction, smelting and alloying. Given the westerly winds
<figure><img src="image_6.png" /><figcaption>**Fig. 4.** $^{208}$Pb transects of the analyzed brown bear teeth. The various peaks in Pb incorporation can be identified in all the different teeth of the same individual, demonstrating that the bear was repeatedly facing environmental pollution. E: enamel (orange); C: cementum (gray); D: dentine (yellow); PD: pre-natal dentine; PND: post-natal dentine; NLD: neo-natal line in dentin; ARC: apical root canal; PC: pulp cavity; AA’-LL’: transects; S1-S7: summer; W1-W7: winter. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>Fig. 5. Maps of $^{208}$Pb, $^{7}$Li and $^{64}$Zn concentration across the Cl/010's lower dentition (c–m$_{3}$).</figcaption></figure>

that usually blow in the region, coupled with the median size of core activity for brown bears (ca. 40 km$^2$; Pop et al., 2018), the assumption of the lead pollution, from this area, for the studied bear, seems plausible.

Comparison with other heavy metal records in wild bear is currently limited by the fact that most studies on the wildlife rely on blood measurements (e.g. Fuchs et al., 2021; Fuchs et al., 2023). Future studies should also establish the link between lead and other heavy metal content in blood (e.g. Fuchs et al., 2021) versus mineralized tissues of modern animals. As an example, Brown et al. (2022) discuss poisoning associated with the ingestion of carcasses containing leaded ammunitions and recover an average of 2 ppm of Pb for females (n = 80) and 1.62 ppm for males (n = 115). Despite the poisoning effect discussed in their context, such whole tooth values remain smaller than what we report in several peaks identified in our study, pointing out to an anomalous Pb source for the heavy exposure in Cl/010 specimen. The high values (10 ppm) reported in Ursus premolars from Idaho by Kohn et al. (2013) are more comparable to those reported in our study. Importantly, the Idaho wildlife has a record of Pb poisoning due to mining activities in the 19th century (e.g., Blus et al., 1987).

Although difficult to extrapolate from one individual to an entire brown bear population, we do not exclude that anthropogenic Pb pollution affected wildlife at a larger scale, as the anthropogenic pollution was widespread about 1000 years ago in southwestern Romania and further (i.e. Bulgaria and Serbia; Longman et al., 2018; 2024). Moreover, it is likely that the entire wildlife mammals (not to mention domestic mammals and humans) – based on their trophic chain organization and dietary habits – have also experienced Pb pollution in the area, during these times. This early example of Pb poisoning shows that the wildlife during the Middle Ages of Europe was already threatened not only by hunting but as well by anthropogenic pollution. The magnitude of the anthropogenic pressure, during the Middle Ages in Europe is a subject to be further investigated but we already predict other mammals and humans to record such heavy metal incorporation into their mineralized tissues. The industrial revolution that took place

since the 19th century witnessed the extinction of many species at the global scale (Liao et al., 2022). Yet, anthropogenic pollution may have triggered a decline in wildlife as early as metal extraction processes were available to human societies.

## CRediT authorship contribution statement

**M. Robu:** Writing – review & editing, Writing – original draft, Visualization, Validation, Methodology, Investigation, Funding acquisition, Conceptualization. **I.-C. Mirea:** Writing – review & editing, Data curation. **D. Veres:** Writing – review & editing. **S. Olive:** Writing – review & editing. **M. Vlaicu:** Writing – review & editing. **P. Telouk:** Software, Methodology, Formal analysis. **J.E. Martin:** Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Project administration, Methodology, Investigation, Conceptualization.

## Funding

This work was supported by the TelluS Program of CNRS/INSU (to JEM and MR) and by the grants TE 187/2021 (INTEGRATE; to MR) and PD 262/2021 (PALEOTRACE; to ICM). SO and JEM received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 101032456-TNT.

## Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
## Acknowledgements

Authors would like to thank to the Speo Alpin MH and Focul Viu speleo clubs for assisting us while sampling and for permission to studying the cave map. JEM and PT thank ENS de Lyon and CNRS INSU for supporting our research. All the analysis of this study was made possible by the INSU/CNRS MC-ICP-MS national facility at ENS-Lyon. We thank the staff at Elemental Scientific Lasers for providing a laser and technical support as part of the formal collaboration with ENS-Lyon. We thank W. Chu, J. Longman and F. Rivals for providing comments on an early version of this work. The authors are indebted to the two anonymous reviewers for improving our manuscript.

## Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.envpol.2025.125766.

## Data availability

No data was used for the research described in the article.

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