Companion dogs’ hair and nails as biomarkers of metal(loid) exposure in a former gold and arsenic mining area, France

A century of mining activities in the gold/arsenic mine of the Salsigne district (Southern France) has resulted in the contamination of water, soil, and wildlife with arsenic (As) as well as other metal(loid)s. The aim of this study was to detect As and 16 other metal(loid)s in non-invasive keratinized samples from companion dogs in the former mining area. In total, 49 hair samples (N = 22 from the control area in central France and N = 27 from the former Salsigne mining area) and 14 nails (N = 6 from the control area and N = 8 from the mining area) were collected from dogs. Analysis of covariance showed higher As levels in hair of dogs (p = 0.046) from the former mining area (mean ± SD 232 ± 382, median 86.8, range 17.8-1759 µg/kg dry mass) compared to those from the control area (70.9 ± 99.7, 48.3, 21.0-506 µg/kg), when sex, age, and body mass of animals were taken into account. Spatial differences in As levels in nails were not statistically confirmed although hair and nail As levels correlated significantly (r = 0.71, p = 0.004). Research has demonstrated that hair of companion dogs cohabiting humans reflect spatial differences among former mining and control groups and therefore can serve as early warning for exposure in the human population.