PFAS dynamics in the American black bear (Ursus americanus): Physiological stages (hyperphagia, hibernation, and post-hibernation), and temporal trends from 1989 to 2015

Qaim Mehdi; Lauren E Blackman; Alina S Timshina; Oumnia Boubad; Colleen Olfenbuttel; Marcella J Kelly; J Bernardo Mesa-Cruz; John A Bowden

doi:10.1016/j.scitotenv.2025.180876

PFAS dynamics in the American black bear (Ursus americanus): Physiological stages (hyperphagia, hibernation, and post-hibernation), and temporal trends from 1989 to 2015

Sci Total Environ. 2025 Nov 20:1005:180876. doi: 10.1016/j.scitotenv.2025.180876. Epub 2025 Nov 8.

Authors

Qaim Mehdi¹, Lauren E Blackman¹, Alina S Timshina², Oumnia Boubad³, Colleen Olfenbuttel⁴, Marcella J Kelly⁵, J Bernardo Mesa-Cruz⁶, John A Bowden⁷

Affiliations

¹ Center for Environmental and Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, 32611, USA.
² Department of Environmental Engineering Sciences, College of Engineering, University of Florida, Gainesville, FL, 32611, USA.
³ Department of Chemistry, College of Liberal Arts and Sciences, University of Florida, Gainesville, FL, 32610, USA.
⁴ Wildlife Management Division, North Carolina Wildlife Resources Commission, Varsity Drive, Raleigh, NC, 27606, USA.
⁵ Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA.
⁶ Department of Fish and Wildlife Conservation, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA; Department of Biological Sciences, East Stroudsburg University of Pennsylvania, East Stroudsburg, PA, 18301, USA.
⁷ Center for Environmental and Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, 32611, USA; Department of Environmental Engineering Sciences, College of Engineering, University of Florida, Gainesville, FL, 32611, USA; Department of Chemistry, College of Liberal Arts and Sciences, University of Florida, Gainesville, FL, 32610, USA. Electronic address: john.bowden@ufl.edu.

PMID: 41207023
DOI: 10.1016/j.scitotenv.2025.180876

Abstract

Per- and polyfluoroalkyl substances (PFAS) have been detected in wildlife globally, yet limited research exists on their presence in terrestrial vertebrate hibernators, such as the American black bear (Ursus americanus). Our goal was to determine plasma PFAS fluctuations across physiological stages (hyperphagia, hypophagia, mid-hibernation, late-hibernation, and post-hibernation) and temporal trends in PFAS levels in black bears over a period of three decades. Plasma from individual black bears (n = 99) contained a range of perfluoroalkyl sulfonic acids (PFSAs; C₆_-₈) and long-chain perfluoroalkyl carboxylic acids (PFCAs; C₈_-₁₄). Total PFAS concentrations (∑₁₀PFAS) ranged from 6.55 to 113 ng/g plasma in all black bears combined. Linear mixed-effects models revealed significant increases in ∑PFSAs from hyperphagia to late-hibernation in female black bears, whereas ∑PFCAs remained stable or declined. Notably, both PFAS classes exhibited a marked decrease during post-hibernation arousal, highlighting the influence of distinct physiological stages on PFAS levels in plasma. ∑PFSA temporal trends between 1989 and 2015 peaked around year 2002 and steadily decreased, likely due to regulatory phase-outs of C₈-based compounds. In contrast, several long-chain PFCAs showed increasing trends, suggesting continued environmental inputs potentially linked to ongoing production or degradation of PFCA precursors.

Keywords: Black bears; Hibernation; PFOS; Physiology; Temporal trends; Terrestrial ecotoxicology.

MeSH terms

Animals
Environmental Monitoring*
Environmental Pollutants* / blood
Environmental Pollutants* / metabolism
Female
Fluorocarbons* / blood
Fluorocarbons* / metabolism
Hibernation*
Hyperphagia
Male
Ursidae* / blood
Ursidae* / physiology

Substances

Fluorocarbons
Environmental Pollutants