The aim of this study was to measure the concentrations of As, Cd, Hg, Pb, Cr, Cu, Fe and Zn in the muscle, liver and kidney of wild boar (Sus scrofa) in Papuk Nature Park, Eastern Croatia. Muscles, liver and kidney of 38 wild boars, up to 3 years of age, were collected and the concentrations of elements were determined by ICP-MS. Cadmium exceeded the permitted levels acceptable for human consumption in 50% of kidney samples (max. = 6.64 mg kg⁻¹), 20% of liver samples (max. = 4.60 mg kg⁻¹) and 43% of muscle samples (max. = 0.672 mg kg⁻¹). Lead exceeded acceptable levels in 63% of liver samples (max. = 0.463 mg kg⁻¹), 51% of kidney samples (max. = 11.8 mg kg⁻¹) and 65% of muscle samples (max. = 9.10 mg kg⁻¹). Mercury concentrations in the liver were higher than allowed in 13% (max. = 0.552 mg kg⁻¹) in kidneys in 27% (max. = 0.484 mg kg⁻¹), and in the muscles in 15% (max. = 0.103 mg kg⁻¹) of cases. Arsenic concentrations in muscles exceeded the permissible value in 30% of cases (max. = 0.286 mg kg⁻¹). The concentrations of Cr, Cu, Fe and Zn did not significantly differ from the values reported in other studies. Median concentrations of Cr, Cu, Fe and Zn ranged as follows: muscle (0.193, 2.94, 44.5 and 20.6 mg kg⁻¹), kidney (0.140, 5.32, 110 and 23.3 mg kg⁻¹) and liver (0.130, 3.71, 278 and 36.0 mg kg⁻¹).

This study is the first investigation into the content of heavy metals (ecotoxic) and metalloids in the available water resources of the Papuk Nature Park (Croatia), conducted after the war in Croatia. Analyses of 13 elements, As, B, Ba, Cd, Co, Cr, Cu, Fe, Ni, Pb, Sr, V and Zn, were carried out on 21 water samples from rivers and their tributaries using the ICP-MS method. The concentration of heavy metals and metalloids in the water of the rivers and their tributaries was low, revealing an intact water environment. Depending on the area of sampling, medians (in µgL⁻¹) were 0.50–4.22 (As), 1.90–141.78 (B), 0.31–60.01 (Ba), 0.16–0.57 (Cd), 0.095–0.62 (Co), 0.18–0.66 (Cr), 1.59–15.89 (Cu), 12.1–1692.2 (Fe), 0.26–8.21 (Ni), 0.017–4.45 (Pb), 0.039–126.09 (Sr), 0.48–2.53 (V), and 3.01–25.95 (Zn). Higher concentrations of Fe (median ranged from 155.42 to 968.20 µgL⁻¹) were found in the northern part of the Papuk Nature Park and are considered to be of natural origin; therefore, anthropogenic influences are excluded. The watercourses of the Papuk Nature Park are generally characterized as a clean ecosystem. This, in part, can be attributed to the human activism legislation that declared Papuk a Nature Park, and the self-healing potential of nature.

Eastern Croatia includes settlements with historically elevated arsenic (As) concentrations in drinking water. Of 488 recruited adults, nine were excluded solely because no questionnaire was available; the exclusion was independent of measured arsenic concentrations, and the harmonised analytical cohort therefore comprised 479 adults from eight settlements. Total As concentrations in drinking water, hair, serum, and urine were measured in samples collected in June 2015 by inductively coupled plasma mass spectrometry. Kidney cancer data (ICD-10 C64) for 2000–2018 were obtained from the Croatian National Cancer Registry and analysed ecologically. MDCK1 cells were exposed to As₂O₃ at 10–200 µg/L for 48, 72, and 96 h, and acetylcholinesterase (AChE) activity was measured in human erythrocytes. Čepin had the highest median As concentrations in drinking water (191.75 µg/L) and urine (68.14 µg/L). Across all eight settlements, drinking-water As was strongly associated with urinary As (slope = 0.537; 95% CI, 0.352–0.722; R² = 0.894; p < 0.001). However, in a sensitivity analysis excluding Čepin and using the seven non-Čepin settlement means reported, the association weakened (r = 0.740; R² = 0.548; slope = 1.246; 95% CI, −0.054 to 2.547; p = 0.057), indicating substantial influence of the Čepin hotspot. Associations with hair As (R² = 0.294; p = 0.165) and serum As (R² = 0.239; p = 0.219) were not statistically significant. In a multivariable Gamma generalized linear model, residence in Čepin was associated with higher expected urinary As than residence in Vladislavci (adjusted mean ratio, 2.90; 95% CI, 1.90–4.42; p < 0.001), while female sex was associated with a lower expected concentration (adjusted mean ratio, 0.80; 95% CI, 0.66–0.97; p = 0.024). No statistically significant effect of As₂O₃ on MDCK1 viability or erythrocyte AChE activity was observed. The findings support urinary total As as a biomarker of recent environmental exposure, but do not establish causal associations with kidney toxicity or kidney cancer.