Portable X-ray Fluorescence for Measuring Lead in the Hair of Wild Mammals

Abstract

Lead (Pb) toxicity is a threat to scavenging wildlife across the globe. To allow inexpensive measurement of long-term lead exposure from archived wildlife tissues, portable X-ray fluorescence (XRF) devices have been optimized to measure lead concentrations in bone samples from avian species. In this study, we assessed portable XRF for hair lead measurement in an Australian mammalian scavenger, the threatened Tasmanian devil (Sarcophilus harrisii). We attempted to first validate the method by analysing relatively large (~1.0 g) hair samples from 39 deceased animals initially with XRF, and then with inductively coupled plasma mass spectrometry (ICP-MS) (validation study). We then measured lead concentrations via XRF only in a further 61 hair samples taken from live devils trapped in a plantation forestry landscape, where devils may scavenge on browsing marsupials that are regularly culled using lead ammunition (plantation study). Portable XRF hair lead measurement demonstrated a positive correlation with ICP-MS results (R2 = 0.95), although the relationship was weak at low lead concentrations. In the validation study, 95% of sampled Tasmanian devils had relatively low lead levels (≤ 3 mg/kg), but the remaining two animals showed considerably elevated lead levels (> 15 mg/kg), suggesting that harmful long-term lead exposure can occur in this species. In the plantation study, lead levels were comparable to those found in the hair of mammals in other studies, though a higher proportion (11%) of devils showed levels > 3 mg/kg than in the validation study, suggesting devils may have higher exposure to lead in a landscape subjected to regular culling of browsing mammals. Our results suggests that portable XRF is a promising emerging technology, and after some refinement, may allow non-invasive real-time measurement of lead concentrations in the hair of mammals.