Impacts of Lead Ammunition and Sinkers on Wildlife
This document is intended to provide information to sportsmen/women on the impacts of lead on wildlife species from recreational sport hunting and fishing. Discussion and interest on this subject has been growing within the hunting, fishing and natural resource communities. It is hoped this summary document will assist hunters and anglers in making informed decisions. Lead in ammunition and fishing tackle is currently banned by some states and agencies and additional bans may occur in the future. It is necessary for the public to understand the issue so they might provide input on future management actions. Relevant information has been assembled and alternatives are given for hunters and anglers. It is hoped this document is found useful and encourage further exploration of the impacts of lead on the environment.
Lead is a heavy metal designated as Pb in the periodic elements table. It is known as a nonessential element to biological life. However, it has been found to be a useful material in many applications. This metal has been used by humans for centuries because it is abundant and easy to smelt. Its malleability, low cost and density has made it attractive for ammunition and lead weights in fishing tackle. Unfortunately, lead is extremely toxic. The metal has been shown to cause anemia, neurological impairment, and immune system impairment. A major problem with lead is that it bioaccumulates in animal tissue. This means that it is absorbed at a faster rate than it is expelled. Thus, toxic levels can be reached if continued lead is absorbed. Due to these serious health issues, lead was banned from paint in 1977, plumbing used for drinking water in 1986, and gasoline in 1996 in the U.S.; however, it is still widely used in other applications such as ammunition and weights (e.g., lead sinkers for fishing tackle). While lead has been linked to human health concerns for centuries, only recently has its harm to wildlife been addressed. Lead is especially problematic for birds, since lead can accumulate in a bird’s gizzard where it is continually ground into smaller particles and readily absorbed into the blood stream.
Sources and Amount of Lead
The primary sources of lead from sporting activities are from lead shot, bullets and fishing weights. The Environmental Protection Agency (EPA) estimates that about 70,000 tons of lead is deposited at shooting ranges each year. While this presents many water quality challenges, the more direct threat to wildlife is lead deposited in the field while hunting and fishing. Prior to the lead ban for waterfowl hunting, it was estimated that more than 2,700 tons of shot where deposited in wetlands each year. Most troubling was that waterfowl tend to congregate in large numbers. Thus, waterfowl hunting and lead shot tended to be concentrated. Likewise, dove hunting may be concentrated on prepared dove food plots and harvested agriculture fields. It is estimated that more than 2.5 million pellets per acre are deposited each year in some of these dove fields. While lead bullets from rifle hunting contribute far less total lead into the environment, fragments remaining in animal carcasses or gut piles left in the field can be hazardous to scavenging animals.
Lead is also used extensively in fishing. Nearly 4,000 tons of lead sinkers are purchased in the U.S. each year. While it is not known how much of that is deposited into the aquatic environment, it is assumed that a high percentage of this lead is lost each year. Various studies have examined the amount of lead along shorelines and the results have ranged from almost none up to more than 100 pieces per square yard in heavily fished areas.
The availability of all this lead shot, bullets, and fishing tackle is dependent on the depth of the lead in the soil. In grassland and forest settings, the lead may be available only for a short time before litter covers it. However, in agriculture areas, lead may be covered and then uncovered annually through cultivation. Additionally, management practices such as fire, grazing and discing can make it available. Thus, the long-term persistence can be for many years, depending on the management of that site. In aquatic systems, lead has been found to accumulate at the top of the sediment and remain there for long periods of time. Lead breaks down within 100 to 300 years, and is no longer available for direct ingestion by wildlife; however, it can then enter the water system and potentially poison wildlife and people.
Impacts to wildlife
Ingestion of lead by birds
There are several ways birds can consume lead. It can be consumed in contaminated plant material, sediment or animal carcasses; it may be even be mistaken for food or grit (which is used in the gizzard to grind food). These last two examples are the most common. Incidental exposure of lead from pellets lodged in the skin or other tissue appears to be of minimal concern, as lead is not easily absorbed into the bloodstream through tissue.
The earliest records for impacts to birds involved waterfowl in the late 1800s, yet it would be several decades before the full impacts were realized. Waterfowl are particularly vulnerable to lead due to the high concentration and availability of lead shot on bare soil (prepared fields) and in shallow wetlands. As few as one or two lead pellets can kill waterfowl. Even if mortality does not occur, poisoned waterfowl have depressed activity and are more at risk of harvest or predation. Prior to the lead ban, estimates of waterfowl mortality in the U.S. ranged from 1.6 to 3.9 million birds per year. The ban on lead for waterfowl hunting has led to a 50 percent reduction of lead ingestion by waterfowl, saving an estimated 1.4 million ducks annually. One #4 lead pellet has negative impacts for three months after ingestion.
Upland game birds are also susceptible to lead poisoning. Lead impacts have been documented for virtually every species of upland game bird in the U.S., including ring-necked pheasant, northern bobwhite, chukar and wild turkey, but perhaps no other upland game bird is more at risk than the mourning dove. The primary reason for their susceptibility is the same as waterfowl—concentrated hunting. Some dove fields collect more than 2.5 million pellets per acre each year. Since the ground is often bare or nearly bare in prepared fields, lead is more available for ingestion. Also, the size shot commonly used for dove hunting is very similar to seeds consumed by the mourning dove (Figure 1). Doves have difficulty maintaining their core body temperature after ingesting lead and appear to die rapidly. As few as two pellets can kill a mourning dove, but doves often consume multiple pellets (Figure 2). Chukar may also be susceptible to ingestion of lead because they frequently use water sources where concentrated shooting can occur. Additionally, the vegetation community that chukar inhabit typically consists of a high amount of bare ground. Research in Utah has demonstrated that up to 11 percent of wild chukar have lead exposure and as few as one lead pellet can kill a chukar. While it is known that lead is consumed by many species of upland game birds, information on the population effects of lead ingestion for most species is lacking. Further, there is little known about the impacts of lead on passerine bird species (e.g., sparrows, thrushes, etc.), but it is likely that lead is most detrimental to species that forage on the ground.
Figure 1. Popular shot sizes for bird hunting is similar in size to many preferred game bird foods. Clockwise from top left, #6 lead shot, #8 lead shot, wooly croton seed and Pennsylvania smartweed seed.
Figure 2. Lead shot ingested by mourning doves is apparent in these X-ray images. Note the bright areas indicating the dense lead shot (Courtesy of Missouri Department of Conservation).
Lead ingestion is not limited to shot; fishing tackle is also a concern for some aquatic birds. Swans, geese, ducks, pelicans and loons have died from lead poisoning. Lead tackle under 2 ounces is most often consumed. Loons probably ingest the lead incidentally as they are eating bait off broken fishing lines. Some studies have found that about half of all loon mortalities were due to lead poisoning. Swans all over the world also have high mortalities from lead. In fact, 90 percent of the mortality of some mute swan populations in Britain was due to lead poisoning from fishing tackle.
Raptor and Scavenger Impacts
Consumption of lead shot, bullets or bullet fragments has been a major mortality cause for imperiled birds of prey and scavengers. For example, through 1996, there were five different states where at least 20 bald eagles died from ingesting lead from carcasses. This is a continual problem for the endangered California condor in California, Utah and Arizona, where strategies to reduce lead poisoning may include capturing birds to cleanse lead from the blood, or having both mandatory and voluntary “no lead” zones for big game hunting. One strategy that has proven successful in Arizona and Utah is issuing vouchers for free copper ammunition to license holders, and encouraging hunters to remove potentially contaminated gut piles from the field. Any unrecovered or wounded animal shot with lead ammunition could potentially cause lead poisoning mortality of a bird of prey. Lead poisoning can also occur in scavenging mammals such as coyotes, wolves and foxes, but because mammals pass lead pieces through their digestive system rather quickly, it is not usually fatal.
Alternatives to lead
Just as nontoxic alternatives have been available for waterfowl hunters for decades, there are now readily available alternatives for upland gamebird hunting and big game hunting. Copper or brass bullets are now readily available in virtually every rifle and handgun caliber. While slightly more expensive than solid lead or lead core bullets, ballistics are similar or better, and weight retention during penetration is usually superior. In fact, the U. S. military is in the process of making a transition to non-lead ammunition. Additionally, frangible bullets, composed of densely packed non-lead alloy powders, some with copper jackets and some unjacketed, are widely used now for law enforcement and personal defense, and are available in some hunting calibers as well. These frangible bullets also have the obvious advantage that there is little or none of the projectile remaining resulting from complete penetration or ricochet. For shot, various alloys of tungsten and bismuth shot are available, but steel shot has been the most popular choice due to lower costs and higher availability. The main things to know when using steel shot is to use larger shot (because it is less dense than lead) and a more open choke (because it does not deform like lead). General recommendations are as follows:
- Go up two shot sizes to achieve similar effectiveness. For example, if you typically shoot # 8 lead, change to # 6 steel.
- Use a slightly heavier load. For example, if you typically use 1 oz. lead loads, use 1 1/8 oz. when shooting steel. This will adjust for the decreased pellet count associated with increased shot size (see Table 1).
- Use a more open choke. For example, if you would typically use a modified choke for lead shot, change to an improved cylinder or skeet choke for steel.
- Pattern your gun to determine the best choke/shot size/shot weight combination for your needs.
- Avoid shooting steel shot through old guns or really tight chokes, which could cause barrel damage.
- Table 1 should serve as a good starting point.
Table 1. Nontoxic equivalents for common lead shot sizes.
|Lead||Recommended Steel Equivalent|
|Size||Shot wt.||Pellets||Size||Shot wt.||Pellets|
|4||1 1/8||152||2||1 1/4||156|
|4||1 1/4||169||2||1 3/8||170|
|5||1 1/8||191||3||1 1/4||194|
|6||1 1/8||251||4||1 1/4||237|
|6||1 1/4||276||4||1 3/8||260|
|7.5||1 1/8||388||5||1 1/4||304|
|7.5||1 1/4||431||5||1 3/8||334|
|8||1 1/8||461||6||1 1/4||394|
|8||1 1/4||511||6||1 3/8||433|
Some hunters are concerned about the cost of using nontoxic shot. While premium steel and alloy loads can cost considerably more than lead shot, some steel loads are priced comparably to lead. There are also many nontoxic alternatives for lead fishing weights. Metals such as steel, brass, and tungsten are produced in an array of sizes and types. Steel and brass are less dense than lead, thus the size for an equivalent weight will be larger. Tungsten is actually denser than lead. However, none of these alternatives are as pliable as lead.
At one time, there were close to 400 lead smelting plants in the U.S., but in December 2013, the last lead smelting plant in the U. S., Missouri’s Doe Run plant, was closed by the Environmental Protection Agency. This does not mean we will suddenly experience a lead shortage, as vast stockpiles of lead bullion exists, and newer smelting plants that can meet the strict clean air guidelines set by the EPA may eventually be built to augment the couple of dozen major lead smelting plants in other countries. But, as the cost of lead inevitably rises, the production of non-toxic ammunition will likely continue its rapid ascent. Thus, in addition to the environmental concerns, the complete transformation to non-toxic ammunition may be forthcoming in the near future.
Current Restrictions on Lead
In the U.S., nontoxic shot is required for all waterfowl hunting, including ducks, geese, swans and coots. Nearly half of all states have specific lead regulations beyond the federal restrictions, many requiring nontoxic shot on certain management units. Additionally, many public hunting areas have toxic shot regulations. Waterfowl Production Areas (WPA) and U.S. Fish and Wildlife Service refuges generally require nontoxic shot for hunting upland bird species because these areas are managed primarily for waterfowl, and often contain numerous wetlands. In Oklahoma, non-toxic shot is currently required for all hunting at Sequoyah National Wildlife Refuge, Washita National Wildlife Refuge, and Hackberry Flats Wetlands Wildlife Management Area, as well as portions of a number of other state wildlife management areas. Various state agencies also limit lead ammunition. For example, Nevada restricts the use of toxic shot on all Wildlife Management Areas. The limitations are put in place to prevent lead shot accumulation in and around these wetland units.
Some species-specific issues have lead to both mandatory and voluntary lead limitation. For example, areas supporting the federally endangered California condor have regulations in place to reduce consumption of lead-contaminated big game carcasses by condors. California requires nontoxic ammunition for big game hunting in areas where condors occur, and both Arizona and Utah provide vouchers to hunters to purchase nontoxic rifle ammunition in the portions of those states where condors occur. This voluntary program has been popular with hunters (with more than 80 percent compliance), and moderately effective at reducing lead risk to the California condor. Hunters are also encouraged to remove potentially contaminated gut piles. Additionally, California is scheduled to have a statewide ban on all lead ammunition by 2019.
Currently, at least seven states have some restrictions on lead in sportfishing; however, several federal lands have bans on lead for fishing. Other countries, such as the United Kingdom, have banned lead fishing tackle altogether.
It is difficult to gauge the success of lead bans on wildlife populations due to limited information. However, the ban on lead for waterfowl has both greatly reduced the availability of lead and the associated mortality for waterfowl. Yet many sportsmen are understandably concerned about impacts any future restrictions might have on their outdoor activities. A common concern is that lead bans will increase the cost of hunting and fishing to the point that sportsman numbers drop. Based on past experience with lead restrictions in waterfowl hunting, we might expect an initial drop in hunter numbers, but as waterfowl populations increased in the 1990s, the number of hunters followed. In fact, the number of federal duck stamps sold only dipped during the 1992 season from 1.43 million to 1.35 million hunters. The following year it was back to 1.4 million and continued to rise to a high of 1.7 million hunters in 1997. Thus, it is questionable that a complete ban on lead in ammunition and fishing tackle would contribute to large, sustained declines in hunting and fishing activities.
It is likely that in the coming years there will be continued restrictions placed on public lands limiting the use of lead ammunition and fishing tackle. Additionally, the EPA at some point may completely restrict the use of lead, which will by default, eliminate its use in hunting and fishing activities and recreational shooting. Voluntary restrictions are much preferred over regulation by most people. As hunters and anglers, it is our responsibility to limit the negative impacts we might have on wildlife populations and the natural resources There is ample data to indicate that lead has negative consequences for many wildlife species. Additionally, nontoxic alternatives exist for nearly every application where lead is currently used. As supply and options continue to increase for nontoxic alternatives, price should decrease.
We encourage each hunter, angler and recreational shooter to carefully consider how he/she might voluntarily reduce impacts to wildlife by restricting the use of lead. This would have a positive impact on some wildlife, and ensure sportsmen/women continue to provide stewardship for not only game species, but for all our nation’s wildlife resources.
For additional information:
Rattner, B.A., J.C. Franson, S.R. Sheffield, C.I. Goddard, N.J. Leonard, D. Stang, and
P.J. Wingate. Sources and Implications of Leadbased Ammunition and Fishing Tackle to Natural Resources. Wildlife Society Technical Review. The Wildlife Society, Bethesda, Maryland, USA.
Sapp, R. 2010. Gun Digest Book of Green Shooting – A practical guide to non-toxic hunting and regulation. Krause Publications, Iola, WI.
Thomas, V. G. 2013. Lead-free hunting rifle ammunition: product availability, price, effectiveness, and role in global wildlife conservation. AMBIO 42:737-745
Natural Resource Ecology and Management
Sutton Avian Research Center
State 4-H Program Leader