Metal(loid) exposure assessment and biomarker responses in captive and free-ranging European brown bear (Ursus arctos)

Lead and Other Trace Element Levels in Brains of Croatian Large Terrestrial Carnivores: Influence of Biological and Ecological Factors

“…Less consistent with differences between American and Croatian brain levels, hepatic Pb in European raptors ranged (mean: 570 μg/kg wet mass, min-max: 11–5760 μg/kg wet mass [ 64 ]; recalculated from dry mass on the basis of 68% H 2 O) similar to bears and higher than in wolves from this study. Blood Pb levels in environmentally exposed raptors and songbirds exhibiting behavioral changes (100 μg/L, [ 28 ]; 785 and 894 μg/kg wet mass [ 25 ]) and in chronically exposed mammalian species with confirmed neurotoxic effects (70–200 μg/L [ 65 ]) was in the range found in our brown bear population (5–168 μg/L [ 41 ]). A study in developing young adult humans with hair Pb levels similar to those in Croatian bears (0.397 vs. 0.401 mg/kg [ 41 ]) found weak Pb-related effects on the excitability and microstructural properties of the brain [ 42 ].…”

“…Large carnivores are at the top of the trophic pyramid and therefore accumulate more non-essential elements than their prey [ 39 ], sometimes approaching toxicologically relevant levels of Cd and/or Pb in the liver and kidneys, as found in 1–5% of Croatian brown bears ( Ursus arctos , [ 40 ]). Furthermore, Pb serum levels in this population were associated with altered antioxidative enzyme superoxide-dismutase activity [ 41 ]. Lead levels and changes in microstructural properties of gray matter were reported in Japanese humans [ 42 ], with Pb hair content similar to those in Croatian brown bears (mean 397 vs. 401 μg/kg, respectively [ 41 , 42 ]).…”

“…Furthermore, Pb serum levels in this population were associated with altered antioxidative enzyme superoxide-dismutase activity [ 41 ]. Lead levels and changes in microstructural properties of gray matter were reported in Japanese humans [ 42 ], with Pb hair content similar to those in Croatian brown bears (mean 397 vs. 401 μg/kg, respectively [ 41 , 42 ]). On those grounds, we hypothesized that with chronic exposure, some non-essential element burden may reach the brain and adversely affect some bears and other sympatric large and medium predators.…”

“…Our concern especially relates to brown bear cubs, as they are in a susceptible life stage with reported renal Pb levels that match their mothers, which may have detrimental impact on their developing brains, taking into account prolonged exposure to Pb, Cd and Hg through suckling [ 43 ]. Except for the already mentioned age of carnivores, sex, season and body condition as determinants of an animal’s health are important confounding factors that have to be taken into consideration while interpreting tissue element levels [ 40 , 41 , 44 , 45 , 46 ]. It should be stressed that Croatian bears and other predators are concomitantly exposed to trace elements and organic pollutants with toxic potential [ 40 , 47 , 48 ].…”

European mammal exposure to lead from ammunition and fishing weight sources

“…Original source of Pb is un-confirmed however ammunition predicted as major contributing factor. Lazarus et al. (2020) Legagneux et al.…”