Expanding the use of portable XRF to monitor lead exposure in an Australian duck species two decades after a ban on lead shot

There is growing worldwide recognition of the threat posed by toxic lead for wildlife and humans. Lead toxicity from ammunition has been shown to be a threat to waterbirds across the globe. Lead shot was banned for all waterfowl hunt-ing in Victoria, Australia, in 2002. However, no assessments of lead exposure in Australian waterfowl have been pub-lished since the 1990s. Our aim was to estimate contemporary lead exposure via measuring bone lead concentrations in a harvested dabbling duck, the Pacific black duck (Anas superciliosa). We collected wings from 77 Pacific black ducks, spanning 2018 (n = 30) and 2021 (n = 47), from nine sites with long-term histories of regular waterfowl hunt-ing. We sought to validate portable X-ray fluorescence (XRF) for this purpose by taking a piece of humerus bone from each bird, and measuring lead concentration (mg/kg), first via non-destructive XRF and then via destructive induc-tively coupled plasma mass spectrometry (ICP-MS) and validated the relationship via regression analysis. Portable XRF bone lead measurement demonstrated a strong correlation with ICP-MS results using root-transformed regression (R2 = 0.85). Greater than 92 % of ducks had only background lead exposure (<10 mg/kg). When compared to histor-ical studies in the same species at similar field sites from the 1990s, lead exposure levels were considerably lower, with mean lead concentrations-2-fold lower (3.7 c.f. 7.7 mg/kg), and the frequency of birds with severe lead exposure (>20 mg/kg)-3-fold lower (2.6 c.f. 7.5 %). Our results confirm that portable XRF is a useful option for measurement of bone lead in Australasian waterbird species. Our findings also demonstrate that a ban on the use of lead shot around 20 years ago has been associated with a substantial reduction in lead exposure in at least one species of waterfowl.

Automated summary

There is a growing recognition worldwide about the threat of toxic lead to wildlife and humans. This study aimed to estimate contemporary lead exposure in Australian waterfowl by measuring bone lead concentrations in Pacific black ducks. The use of portable X-ray fluorescence (XRF) showed that lead exposure levels in these ducks have significantly decreased compared to historical studies from the 1990s, indicating the effectiveness of the lead shot ban in reducing lead exposure in waterfowl.