Feasibility and accuracy of In Vivo and Ex Vivo XRF bone lead assessment wild birds: An example with black vultures, Coragyps atratus.

BACKGROUND

Lead (Pb) contamination in wildlife remains a critical environmental concern, particularly for scavenger species, which are at high risk due to ingestion of lead-contaminated carrion. Portable XRF (pXRF) systems can be useful to evaluate lead concentration of wild animals in vivo. However, the accuracy of these systems has never been validated for living birds.

METHODS

We evaluated differences in the quantification of lead in the tarsometatarsus (TMT) and femur bones of 19 wild-caught black vultures (Coragyps atratus) by portable (pXRF) and benchtop X-ray fluorescence (XRF) systems with validation against inductively-coupled plasma mass spectrometry (ICP-MS).

RESULTS

We found a strong correlation between benchtop XRF and ICP-MS (R² = 0.92-0.95), and lower correlation between pXRF and ICP-MS (R² = 0.62-0.67), primarily because pXRF systematically underestimated lead concentrations. When compared to ICP-MS, Intraclass Correlation Coefficients (ICC) further confirmed better performance of benchtop XRF in measuring femur and TMT lead (ICC = 0.959-0.968) compared to pXRF (ICC = 0.739-0.742). pXRF in vivo TMT lead concentrations were highly correlated (R² = 0.85) to ex vivo results with the same instrument, with the soft tissue on the living animal having minimal effect on the measurement.

DISCUSSION

Although pXRF offers critical advantages in field applications, its limitations necessitate careful interpretation of results. Future research could improve pXRF optimization and extend this approach to other wildlife populations. This work contributes valuable data on lead exposure in vultures and illustrates a mechanism by which lead exposure of birds can be evaluated in vivo in wild or captive populations.