Where can lead be found in the environment?
Lead is a naturally occurring metal found in the earth’s crust. Lead can be found many places, much because of human activity through burning fossil fuels, mining, and manufacturing. Water can be contaminated with lead from mines, waste dumps, and industrial plants. House paint and gasoline were once manufactured with lead. Fishing sinkers and jigs are often made from lead. Most firearms ammunition contain lead including pellets, shot, slugs, round balls, and bullets.
By the mid-1990s, lead had been removed from the manufacturing process in many products in the U.S., including paint and gasoline.
How does lead poison?
Lead is a potentially deadly toxin that damages internal organs of the body and can impact all animals, including humans. For both birds and people, lead must be eaten (ingested) or lead particles or fumes inhaled to elevate lead levels to cause poisoning. Examples of how people can ingest lead include eating paint chips, inhaling paint fumes and paint dust, eating wildlife harvested with lead shot or lead slugs. Stomach acid breaks down lead and then lead is absorbed into the blood stream. Fine particles and fumes that are inhaled are absorbed into the bloodstream through the lungs. Learn more about the physiology of lead from the Agency for Toxic Substances & Disease Registry (a part of the Centers for Disease Control) in this section of a medical education course! (343 KB PDF)
Primary lead exposure in animals is caused by the animal eating lead directly, mistaking it for food or grit. Secondary lead exposure in animals comes from the animal eating another animal that contains lead. This prey animal either swallowed lead or has lead shot/slug embedded in it.
Click here to learn more about SOAR’s efforts to rehabilitate birds with lead exposure.
What are the effects of lead poisoning?
Lead mimics calcium in an animal’s body, it impacts nervous tissue and is stored in bone. Blood lead levels (BLL) are measured in micrograms per deciliter. At a BLL below 10 micrograms per deciliter (10 µg/dL), this lead can cross the placenta and can be found in breast milk.
Young children and pregnant women absorb more lead than do adult males. In children, even a small amount of lead can cause learning delays, decreased intelligence, shortened attention span, and very high lead levels may cause brain damage or even death. Lead exposure in children may also result in expression of antisocial behaviors.
Very low lead levels increase an adult males’ risk of stroke and heart attack and can decrease sperm count.
Later in life, lead can re-emerge from bone tissue causing high blood pressure, kidney failure, and Parkinson’s Disease.
High BLL in birds (from loons, doves, cranes, swans, to vultures, eagles, crows, and other scavenging birds) impacts the nervous and circulatory systems and the kidneys. The weakened bird has trouble flying, hunting/feeding, is much more susceptible to infection, and often starves. In female birds with low BLL, reproduction is impacted.
Click here to read more about the lead and eagles research SOAR has done.
What are the exposure thresholds for humans and wildlife?
The current blood lead level which defines lead poisoning in children under the age of six is 5 micrograms of lead per deciliter of blood or more (≥5 µg/dL). A blood lead level of 5 or greater in a child is a trigger for continued monitoring by healthcare providers. This level changed in May 2012 upon recommendation from the Advisory Committee on Childhood Lead Poisoning Prevention from 10 to 5 µg/dL. This panel also recommended that CDC look at lowering this target level every four years. Many consider that there are no safe levels of lead in the body.
There are no established exposure levels for wildlife as it is different for each species. In clinical trials, 200 milligrams of lead (one #4 size piece of shot or the size of a grain of rice) was found to be the lethal dose for a bald eagle.
Bluer Shade of Blue
Chad Elliot, a Coon Rapids, Iowa musician wrote a song to highlight the tragic affects of lead hunting ammunition on the bald eagle. SOAR volunteer, “PharmerDave,” put a video to Chad’s music.
For more information about lead, visit:
- Environmental Protection Agency
- Centers for Disease Control
- Department of Health and Human Services, Agency for Toxic Substances and Disease Registry
Articles about the impacts of lead:
- Neurotoxicity and aggressiveness triggered by low-level lead in children: a review (135 KB PDF)
- Whole-Body Lifetime Occupational Lead Exposure and Risk of Parkinson’s Disease (506 KB PDF)
- Health Risks from Lead-Based Ammunition in the Environment: A Consensus Statement of Scientists (190 KB PDF)
- Health Risks from Lead-Based Ammunition in the Environment An editorial in Environmental Health Perspectives, June 2013 (107 KB PDF)