(Other names: lead toxicity, lead toxicosis)
A bald eagle presenting with signs of lead poisoning. Note its drooping wings, inability to hold up its head, and apparent weakness. If you find a bird in this condition, submit a Sick or Dead Wildlife report to Indiana DNR.
Description
Lead is a dense heavy metal that is common throughout the earth’s crust. Although it has been used by humans since prehistoric times, surmounting evidence shows that lead exposure negatively affects the health of animals. More recently, there is strong evidence that lead exposure in wildlife is widespread and can cause harmful effects. Lead toxicity is commonly documented in raptors, scavenger birds, and waterfowl as a result of lead use in hunting and fishing equipment.
Transmission
Raptors and other scavengers incidentally consume lead when they ingest the remains of animals left behind by hunters who used lead shot. Waterfowl can also contract lead poisoning from ingesting lead shot, gigs, or sinkers left in or near bodies of water.
When inside an animal, lead is transported on red blood cells to tissues and eventually the bones. Particularly in birds, lead is dissolved in the gizzard or ventriculus and absorbed into body tissues. This can lead to a variety of physiological syndromes, including kidney impairment, neurological damage, liver dysfunction, and/or gastrointestinal distress. Due to the myriad of possible inflections, clinical signs of lead toxicity are nonspecific.
Clinical Signs
Clinical signs of chronic lead toxicity in waterfowl can include decreased food intake, drooping wings, apparent weakness, inability to walk or fly, watery green diarrhea, a green-stained vent, and/or emaciation . Raptors often present similar clinical signs as waterfowl, but they also commonly experience swelling, respiratory issues, and seizures. Acute lead exposure presents similarly to chronic exposure, though emaciation is often not associated.
Other clinical signs may be less apparent, including enlarged gallbladders, green-stained gizzard lining, reduced reproductive fitness, increased predation due to weakness, and increased susceptibility to other diseases.
Wildlife Management Implications
Lead toxicity is primarily caused by human actions; therefore, it is not associated with typical disease outbreak patterns. Monitoring wildlife populations and documenting lead toxicity events will aid in informing policymakers concerning the limits of lead used in ammunition and other products. For example, due to the prevalence of lead poisoning in waterfowl, lead shot for hunting waterfowl has been banned nationwide since 1991.
You can continue help protect wildlife by submitting a Sick or Dead Animal Report to Indiana DNR if you encounter an animal exhibiting signs of lead toxicity. Find more information on ways that hunters, anglers, and other outdoor enthusiasts can help reduce lead in the environment on our website.
Human Health Significance
While lead exposure is potentially harmful at any age, it is most serious in children. Children exposed to lead can suffer from permanent damage to the brain and the nervous system, slowed growth and development, learning and behavioral problems, and hearing and/or speech impairment. Ingestion of contaminated meat is not a common source of lead exposure; however, because no safe blood lead level in children has been identified and lead exposure is cumulative, parents are encouraged to minimize the risk of lead ingestion associated with hunting and fishing by using non-lead alternatives during these activities. Handling and disposing of animal tissue containing lead is not expected to be harmful.
For more information, visit the Indiana Department of Health or the Centers for Disease Control and Prevention.
Additional Resources
Carson, R. (2002). Silent spring. Houghton Mifflin Harcourt.
Demayo, A., Taylor, M. C., Taylor, K. W., Hodson, P. V., & Hammond, P. B. (1982). Toxic effects of lead and lead compounds on human health, aquatic life, wildlife plants, and livestock. Critical reviews in environmental science and technology, 12(4), 257-305.
Garvin, J. C., Slabe, V. A., & Cuadros Díaz, S. F. (2020). Conservation Letter: Lead Poisoning of Raptors. Journal of Raptor Research, 54(4), 473-479.
Grade, T., Campbell, P., Cooley, T., Kneeland, M., Leslie, E., MacDonald, B., ... & Pokras, M. (2019). Lead poisoning from ingestion of fishing gear: A review. Ambio, 48(9), 1023-1038.
Krone, O. (2018). Lead poisoning in birds of prey. In Birds of prey (pp. 251-272). Springer, Cham.
Pain, D. J., Mateo, R. & Green, R.E. 2019. Effects of lead from ammunition on birds and other wildlife: a review and update. Ambio Special Issue: LEAD USE IN HUNTING. Online 16 March 2019. DOI: 10.1007/s13280-019-01159-0