Effects of lead exposure on oxidative stress biomarkers and plasma biochemistry in waterbirds in the field

Medina lagoon in Andalusia has one of the highest densities of spent lead (Pb) shot in Europe. Blood samples from waterbirds were collected in 2006–2008 to measure Pb concentration (PbB), δ-aminolevulinic acid dehydratase (ALAD), oxidative stress biomarkers and plasma biochemistry. PbB above background levels (>20 μg/dl) was observed in 19% (n=59) of mallards (Anas platyrhynchos) and in all common pochards (Aythya ferina) (n=4), but common coots (Fulica atra) (n=37) and moorhens (Gallinula chloropus) (n=12) were all <20 μg/dl. ALAD ratio in mallards and coots decreased with PbB levels >6 μg/dl. In mallards, an inhibition of glutathione peroxidase (GPx) and an increased level of oxidized glutathione (oxGSH) in red blood cells (RBC) were associated with PbB levels >20 μg/dl. In coots, PbB levels were negatively related to vitamin A and carotenoid levels in plasma, and total glutathione in RBCs; and positively related with higher superoxide dismutase and GPx activities and % oxGSH in RBCs. Overall, the results indicate that previously assumed background levels of PbB for birds need to be revised.

► Waterbirds were captured from a wetland with extremely high densities of Pb shot.
► Blood samples were analyzed for non-destructive biomonitoring.
► 25 years after the ban on hunting, waterbirds are exposed to Pb to different levels.
► Disruption of heme biosynthesis pathway and redox balance in blood were detected.
► Previously assumed background levels of Pb in blood for birds need to be revised.