DNR conducts first ever lead fragmentation study
Information discovered last spring indicates that small lead fragments often are present in hunter-harvested venison, particularly ground venison. As a result, the Minnesota DNR conducted the first-of-its-kind lead fragmentation study to simulate how different types of bullets commonly used for deer hunting might fragment.
To date, no illnesses have been linked to consumption of lead particles in hunter-harvested venison. But the DNR recognizes that the potential impacts of lead fragments ingested when eating hunter-harvested game are not well understood. Only now are state and federal health, wildlife and food safety agencies beginning to collect, study and analyze data to determine exactly what those impacts may be.
DNR Fish & Wildlife Division staff designed the study using firearms and ammunition commonly used by Minnesota deer hunters. The results are not exhaustive but they do show that all bullets fragment, some more than others, and make it clear that lead fragments travel much farther than expected.
The intent of the study was to conduct an experiment that would control for bullet caliber and focus on examining the variability of lead fragmentation and deposition associated with distinctly different categories of bullets and firearms used to harvest deer in Minnesota. We selected bullets based on their advertised performance and consumer availability. For this study, 72 previously euthanized domestic sheep were used as a surrogate for white-tailed deer.
The study was conducted in July 2008 at Carlos Avery Wildlife Management Area. X-Rays and CT scans were taken at the University of Minnesota Small Animal Hospital and lead analysis was completed by the University of Minnesota Veterinary Diagnostic Laboratory.
The guns used for this study included centerfire rifle, muzzleloader and shotgun.
For centerfire rifle, the DNR used a .308 with 150 grain bullets and five different bullet designs:
Rapid Expansion (Ballistic Tip, Soft Point)
Controlled Expansion (exposed lead core, non-exposed lead core)
For the muzzleloader, the DNR used a .50 caliber, 100 grains of powder (2-50 grain Hodgdon 777 pellets) and two different bullet designs:
For the shotgun, the DNR used a 12-gauge and a 1-ounce Foster-style slug
The DNR also shot three sheep in the pelvic region using a ballistic tip, soft point, and slug to document dispersion of lead in animals shot poorly.
The DNR skinned and gutted each carcass, inserted a carbon fiber tube through the wound channel, then took a radiograph on the exit wound side. The DNR also rinsed carcasses of sheep shot with both types of rapid expansion bullets and took a second radiograph to determine the effect washing had on fragment distribution.
A veterinarian counted the number of fragments and measured the maximum distances the fragments travelled.
The extent of lead contamination in muscle tissue was determined using techniques similar to other studies published in scientific literature. We collected muscle tissue samples at 2, 10 and 18 inches from the exit wounds. We also measured the diameter of the entry/exit holes and the wound channel length.
The study showed that using bullets with no exposed lead (a copper case completely surrounds the lead core) or copper are two ways to significantly reduce (or eliminate) lead exposure. The non-exposed lead core bullets averaged nine copper fragments in the animal with an average maximum distance from the wound channel of seven inches. By design, copper bullets leave no lead and the few fragments that were seen on x-ray were less than an inch from the exit wound. Overall, both of these bullet designs fragmented very little and left no lead.
The ballistic tip bullet (rapid expansion) had the highest fragmentation rate, with an average of 141 fragments per carcass and an average maximum distance of 11 inches from the wound channel. In one carcass, a fragment was found 14 inches from the exit wound.
Soft point bullets (rapid expansion) left an average of 86 fragments at an average maximum distance of 11 inches from the wound channel. In this research, bonded lead-core bullets (controlled expansion, exposed lead core) performed almost identically to the soft-core bullets and left an average of 82 fragments with an average maximum distance of nine inches from the wound.
Shotgun slugs left an average of 28 fragments at an average maximum distance of five inches from the wound channel. Muzzleloader bullets (245-grain and 300-grain respectively) left an average of three and 34 fragments, respectively, at an average maximum distances of one and six inches, respectively.
A key take away message from the study is that given fragments were found so far from the exit wound, routine trimming likely will not remove all of the fragments and DNR cannot make a recommendation as to how far out trimming should occur.
In counting fragments, only about 30 percent were within two inches of the exit wound. The vast majority was dispersed further from the carcass. In some cases, researchers found low levels of lead as far away as 18 inches from the bullet exit hole. The DNR also learned that rinsing a carcass produced mixed results. While rinsing tends to reduce lead around the wound channel it also transports lead away from the wound.
The research also showed that a shot to the hindquarters of a deer -- where heavy bones are found -- will result in extensive fragmentation. Fragmentation was so pronounced that a hunter would likely not want to utilize this meat as there would be no way to remove all the fragments. The full research report is available at www.dnr.state.gov/lead.