Last week, a rigorous, peer-reviewed scientific study on lead ingestion in wildlife populations was published in the scientific journal PLOS ONE.
The study scientifically demonstrates how current estimates of terrestrial bird losses across Europe from ingestion of lead ammunition, which have been used also by the European Chemicals Agency (ECHA) in its restriction proposal, are based on uncertain or generic assumptions, essentially showing how the methodology behind most of the current literature is not efficient and leads to flawed outcomes.
Key findings include:
- ECHA assumes that population sizes are decreased by the additional annual mortality, however, ECHA did not have a quantitative or qualitative estimate of the percentage of terrestrial carnivorous birds with lead poisoning.
- Instead, ECHA developed a highly uncertain estimate of 1% decrease in terrestrial game birds from lead shot ingestion.
- The data supporting the estimate are mostly from the UK and ECHA has mixed different statistics that are not comparable.
Instead of ECHA’s 1-step approach, the authors have developed a 2-step population modelling approach:
- Evaluate the percentage of carcasses that died from lead ammunition ingestion (data from actual necropsy and pathology reports or available field tracking data with transmitters), and then convert that percentage into annual mortality rates; and then
- Use population modelling that incorporates population dynamics to evaluate changes in population growth rate and size based on carcasses.
Using the study’s model, the authors estimate that the final percentages after pooling across countries in Europe for gallinaceous birds were 0.2% for direct (i.e. lead is a direct cause of death) and 1.4% for the ultimate estimate of lead-shot-ingestion-caused deaths (i.e. lead is an indirect cause of death), with a midpoint estimate of 0.8%. The estimated direct cause of death (0.2%) is lower (5 times lower) than ECHA’s arbitrarily selected 1% estimate that they used to estimate primary poisoning without accounting for among-country differences in exposure or population modeling.
Of course, this study’s proposed methodology is of benefit to the hunting and shooting sector interests around the world, particularly when regulators and certain NGOs tend to push uncertain or arbitrary estimates of risk to birds from lead in ammunition. Further, the model used that can be replicated in all national and regional contexts.
The Bottom Line: Claims that lead ammunition leads to mass death in bird populations are both not scientifically founded and grossly exaggerated. It is important to note that this study was done on overall lead impact, not just lead from hunting and shooting sports. The benefits brought to habitat, wildlife, and conservation initiatives from hunting outweigh the minimal risks posed by lead ammunition to the environment.
Read the full study: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0273572#sec001
