Washington, July 13 : According to a new scientific report, millions of pounds of lead used in hunting, fishing and shooting sports wind up in the environment each year and can threaten or kill wildlife.
Lead is a metal with no known beneficial role in biological systems, and its use in gasoline, paint, pesticides, and solder in food cans has nearly been eliminated.
Although lead shot was banned for waterfowl hunting in 1991, its use in ammunition for upland hunting, shooting sports, and in fishing tackle remains common.
While noting that more information is needed on some aspects of the impact of lead on wildlife, the authors said that numerous studies already documented adverse effects to wildlife, especially waterbirds and scavenging species, like hawks and eagles.
Lead exposure from ingested lead shot, bullets, and fishing sinkers also has been reported in reptiles, and studies near shooting ranges have shown evidence of lead poisoning in small mammals.
Frequently used upland hunting fields may have as much as 400,000 shot per acre. Individual shooting ranges may receive as much as 1.5 to 23 tons of lead shot and bullets annually, and outdoor shooting ranges overall may use more than 80,000 tons of lead shot and bullets each year.
Although precise estimates are not available for lead fishing tackle in the environment, about 4,382 tons of lead fishing sinkers are sold each year in the United States.
According to USGS contaminants experts Drs. Barnett Rattner and Chris Franson, the most significant hazard to wildlife is through direct ingestion of spent lead shot and bullets, lost fishing sinkers and tackle, and related fragments, or through consumption of wounded or dead prey containing lead shot, bullets or fragments.
"Science is replete with evidence that ingestion of spent ammunition and fishing tackle can kill birds," said Rattner. "The magnitude of poisoning in some species such as waterfowl, eagles, California condors, swans and loons, is daunting," he added.
Lead poisoning causes behavioral, physiological, and biochemical effects, and often death. The rate of mortality is high enough to affect the populations of some wildlife species.
Although lead from spent ammunition and lost fishing tackle is not readily released into aquatic and terrestrial systems, under some environmental conditions it can slowly dissolve and enter groundwater, making it potentially hazardous for plants, animals, and perhaps even people if it enters water bodies or is taken up in plant roots.
According to the researchers, a better understanding of the toxicity and amount of lead poisoning in reptiles and aquatic birds related to fishing tackle is needed, as well as more information on the hazards of spent ammunition and mobilized lead at or near shooting ranges.