Wild game source of lead for those who eat the hunted meat.
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Iqbal, S, W Blumenthal, C Kennedy, FY Yip, S Pickard, WD Flanders, K Loringer, K Kruger, KL Caldwell and MJ Brown. 2009. Hunting with lead: Association between blood lead levels and wild game consumption. Environmental Research doi:10.1016/j.envres.2009.08.007. |
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| journeyguy/flickr |
| Lead in bullets used to hunt game like deer and elk can contaminate the meat and raise lead levels in people who eat the animals. |
Context
Lead is still used in many products and continues to linger in the environment, even though some countries have banned its use in paint and gasoline. One often overlooked source is ammunition. Lead was banned for hunting waterfowl in 1991 but bullets used for other types of hunting and shooting sports still contain the metal. In the US, efforts to ban lead from these bullets is ongoing, and they remain a source of environmental lead exposure.
Many bullets used by sportsmen end up in firing ranges or skeet-shooting fields. Also, once shot, bullets can fragment and lodge in the meat and bone of animals that were hunted. People who eat the meat are exposed to the lead because the metal leaches from the fragments into the wild game (MNDNR 2008; Hunt et al. 2009). Research studies have documented this transfer – which can raise blood lead levels – mainly between game birds and people and within native or subsistence populations (Johansen et al. 2006). Raptors and other wildlife that eat the carcasses are also vulnerable to lead poisoning.
Lead has a long history with hunting. Pellets used in classic black powder or muzzle loading firearms common during earlier centuries were pure lead. The current high-velocity bullets are made of a lead core or a harder alloy of lead and tin called typesetter’s lead. They are generally jacketed with copper, cupronickel or steel.
Despite its toxicity, lead is used for fabricating bullets because it is cheap, dense and malleable. Each day, between 400-600 tons of lead are used for manufacturing ammunition.
In the US, hunting for wild game is a popular activity, especially in the West North Central region. Rates of people older than 16 years old who hunt in this part of the country are more than double the national average. North Dakota has one of the highest percentage – more than 17 percent – of residents who hunt.
The wild game meat is often processed by hunters for personal consumption. In some instances, meat is donated to charity to serve as a source of protein for low-income individuals. The “Sportsmen against Hunger” is one of the organizations that helps distribute the excess wild game meat from hunting.
Lead shot found in donated meat prompted safety concerns for those eating the meat. Virtually no organ is immune to the effects of lead, but it is especially harmful to the nervous, circulatory and reproductive systems. Children are especially vulnerable due to their developing brains and nervous system.
The cognitive and health effects from lead exposure can persist for many years. In the US, the Centers for Disease Control and Prevention have set the lead level of concern at 10 micrograms per deciliter of blood. Some experts believe there is no level of lead exposure that is safe for people (CDC 2007).
What did they do?
Scientists compared lead levels in blood and wild game consumption habits of 736 volunteers who lived in six North Dakota cities (Bismarck, Fargo, Minot, Jamestown, Dickinson and Grand Forks). The volunteers ranged in age from 2 to 92 years old, were mostly white and had middle to high income.
Participants filled out a questionnaire about their socio-demographic background, housing, lead-related hobbies, occupation and wild game consumption habits, including how often, processing methods, portion sizes and types of game eaten. Game was classified as venison, other game (such as moose and elk) and birds (other than waterfowl).
Blood samples were collected from all participants, and lead levels were determined by mass spectrometry. Statistical methods were used to control for other sources of lead exposure, such as through hobbies, work and paint in homes.
What did they find?
The amount, frequency and types of wild game eaten were significant factors in the increased levels of lead measured in the blood of the study's participants. Blood lead levels were higher in those who ate more meat, who ate it more often and who ate all three types of game. It was also significantly higher in those who ate a meal in the last month.
Age and sex were other associating factors. Male subjects had higher lead levels; so did older subjects. Volunteers older than 65 years of age had the highest levels of lead in their blood averaging 1.77 micrograms/deciliter (ug/dl) – probably due to a lifetime of cumulative exposure.
After taking into account factors that might influence blood lead levels, such as hobbies and demographics, the reseachers report that eating any type of wild game was significantly associated with an increase of 0.30 ug/dl of blood lead levels, when compared to those who did not consume the meat. Those who consumed all three categories of wild meat had even higher differences in blood lead levels – 0.5 micrograms/deciliter – than those who did not eat any game.
Individuals who ate wild game meat had an average of 1.27 ug/dl blood lead levels as compared to 0.84 ug/dl for non-consumers. Blood lead levels ranged from 0.18 - 9.82 ug/dl, so none of the volunteers tested exceeded the concern level of 10 ug/dl of blood set by the US Centers for Disease Control and Prevention.
Based on the questionnaire, 80 percent of participants had eaten at least one type of wild game meal during the previous year. Of those, 86 percent ate multiple types of game. Almost all ate venison (99 percent), while 84 percent consumed birds and over half – 65 percent – ate other game.
The meat was eaten throughout the year by most of the respondents. Venison was consumed most frequently – sometimes weekly. Reported serving sizes averaged less than two ounces per serving.
The vast majority of the participants had either hunted the meat themselves or gotten it from a family member or friend. About 82 percent said they or a family member processed the game, and 92 percent discarded the meat around the wound channel. Others had butchers and meat packers process the meat.
What does it mean?
Wild game consumption is associated with an increase in blood lead levels. This increase is presumably due to the use of lead ammunition.
These results confirm findings of other small-scale studies performed in humans and animals that report a significant increase in blood lead levels following consumption of contaminated wild game meat with lead ammunition (Kosnett 2008).
The results, in combination with prior studies, suggest that eating wild game shot with leaded bullets is a source of environmental lead exposure. Blood lead levels have been declining in the US in recent years, but any source of lead exposure can pose a health danger, especially to the developing fetus and children.
Although care is taken to remove the bullets from the game before consumption, it may not be enough to prevent exposure. In many cases, the bullet shatters after hitting the bone and scatters throughout the game, making it very difficult to remove all of the fragments.
The participants in this study were mostly educated white adults and the wild game was mostly processed and consumed by the hunters’ family and friends. Since children and low-income individuals were underrepresented, this study has limited generalization.
The “Sportsmen against Hunger” program donates excess wild game meat provided by hunters to charitable organizations as a source of protein for low-income residents. For this group, frequent consumption of lead-tainted wild game has important public health implications.
Careful butchering practices – to remove all bullet fragments and the meat that has come into contact with them – can dramatically decrease the amount of lead exposure through eating wild game.
Alternatively, use of non-lead bullets or hunting with bow and arrow can eliminate this type of lead exposure.
ResourcesCenters for Disease Control and Prevention. Concerns rise over known and potential impacts of lead on wildlife. US Geological Survey. Hunt, WG, RT Watson, JL Oaks, CN Parish, KK Burnham, RL Tucker, et al. 2009. Lead bullet fragments in venison from rifle-killed deer: potential for human dietary exposure. PLosOne 4(4),e5330, doi:10.1371/journal.- Johansen, P., HS Pedersen, G Asmund and F Riget, 2006. Lead shot from hunting as a Kosnett, MJ. 2008. Health effects of low-dose lead exposure in adults and children, and preventable risk posed by the consumption of game meat harvested with lead ammunition. In: Conference Proceedings: Symposium on Ingestion of Lead from Spent Ammunition: Implications for Wildlife and Humans, Lead. ToxFAQs. Agency for Toxic Substances and Disease Registry. Lead information for hunters. 2008. Minnesota Department of Natural Resources (MNDNR). |
Lead contamination and hunting
