Categories: Pollution Article 4

Introduction

In 1998, Lanphear published an article in Science (Lanphear 1998) entitled “The Paradox of Lead Poisoning Prevention”, that commented on the state of remediation efforts in the USA to counteract the prevalent lead poisoning of children. Lanphear’s main argument was that while the permanent, deleterious impacts of lead poisoning upon human health have been documented scientifically for a very long time, attempts to achieve primary prevention of the disease have been illusory. This author defined the paradox as a nation, with the capacity to deliver a scientifically-based strategy for eliminating subclinical lead toxicity in children, failing because of competing political and economic interests, leaving continual monitoring as the only tangible evidence of action. While the paper by Lanphear (1998) addresses only human heath concerns, it has several parallels at the broader environmental level, and especially for the lead poisoning of wildlife from shooting and angling.

The majority of lead related to pollution has been derived from human activities across at least 4 millennia, especially in Europe. The science devoted to the consequences of lead pollution has addressed predominately human health issues (Nevin 2000), but in recent decades, a broader environmental impact of lead has been detected, especially upon wildlife. However, the general understanding of the consequences of lead pollution, rather than being represented as a continuum in which human toxicology issues intertwine with environmental issues, are better described as two solitudes, in which human issues appear separated from other manifestations of lead in wild ecosystems (Thomas 1997a; 1997b). This reflects the professional division between the medical/health scientists and wildlife scientists, the latter being somewhat newer to lead toxicosis in wild animals, and also being fewer in relative numbers. Because lead poisoning of wildlife from shooting and fishing has generally been separated from other forms of human lead pollution, there are different standards, attitudes, policies and laws related to these issues, whether in North America or Europe (Thomas 1997a; 1997b). Major reviews of the scientific literature on the effects of lead pollution on human animal health exist (e.g. National Research Council 1993; Royal Society of Canada 1986; World Health Organisation 1989), all of which focus on the human dimensions of lead pollution. However, offsetting them are reviews of the literature documenting the impacts of lead on wild species (Eisler 1988; Pain 1995), and more specifically, the toxic impacts of lead from shot and fishing weights upon birds (U.S. Fish and Wildlife Service 1986; Pain 1992; Scheuhammer and Norris 1995; Guitart et al. 1999). Despite the previous dichotomous approaches, the Organisation for Economic Cooperation and Development (OECD) did address poisoning from shot and weights in its review monograph on lead risk reduction (OECD 1993). What these reviews indicate (when taken together with many hundreds of other published papers) is a single environmental lead syndrome that has similar manifestations across animal species (including human beings), and also across biological kingdoms.

This is apparent in cases where lead shot ammunition is used to harvest wild game that becomes the staple diet of human beings. Johansen et al. (2001) reported that the lead in the seabird diet of Greenlanders is derived principally from lead shot. Fifteen per cent of radiographs taken from the native people of the James Bay region of Canada revealed the intestinal presence of lead shot derived from their wild waterfowl diet (Tsuji and Nieboer 1997), shot that may contribute to elevated blood lead levels (Madsen et al. 1998), appendicitis (Carey 1977), and neuropathy (Hillman 1967). In addition to these examples of direct human lead poisoning, secondary lead poisoning may occur, when humans eat the organs of harvested waterfowl that exhibit high tissue lead levels from ingested shot (Guitart et al. 2002).

The common nature of the lead syndrome among different species can be related to certain properties of lead. The biological effects of lead are associated with the ability to mimic or inhibit the physiological action of calcium, due to chemical similarities between the metals (Manahan 1989). Lead ions also show a proclivity for binding to key sites on enzymes, causing metabolic and anabolic disruption in animals (Manahan 1989; Klaassen 1996). The physiological and biochemical systems of vertebrates share close similarities because of their common evolutionary origins. This is why the fundamental nature of lead toxicosis is common across taxa, even though the clinical manifestations of the toxicosis may vary slightly among species (World Health Organisation 1989; Lumeij 1985). We argue that, given all that is known about the broad toxicity of lead and its routes of entry into the human and natural environments, the real paradox is that governments have not acted more decisively to reduce the use of lead shot and sinkers, and introduce the same legislative standards for wildlife as have been proposed and/or adopted for human protection.

Amounts of Lead Shot and Sinkers Added to the Environment

Lead toxicosis is caused by spent lead shot that is ingested by birds searching for grit, or by fishing weights that are ingested by fish-eating birds. Secondary lead toxicosis arises when predators eat the bodies of birds containing lead shot in their tissues (U.S. Fish and Wildlife Service 1986; Twiss and Thomas 1998). The ammunition and fishing tackle industries are not required to report the amount of lead shot and sinkers produced and sold in any country. Consequently, figures for the tonnage of lead released to the environment from these sources are estimates. Guitart et al. (1999) estimated that about 100 000 tonnes of lead are used annually, worldwide, for shot alone. If the values presented by Eisler (1988) are still valid, this single use of lead constitutes the World’s third largest value (about 8 per cent of the total), after lead use in batteries and pigment/chemical manufacture. The amount of lead shot produced and used each year varies by country. The USA uses about 66 000 t annually (Eisler 1988), and Spain, about 6000 t (Guitart et al. 2002). Waterfowl hunters in Canada use about 2000 t yr (Scheuhammer and Norris 1995). The main feature of shot that distinguishes it from all other forms of human lead use is that shot is made to be fired, deliberately, into the environment after a target. Whether the target is hit or missed, the shot will fall to earth or water, and remain there, where it may become solubilised over time and enter groundwater or wildlife (Jørgensen and Willems 1987; Ma 1989). The lead used to make batteries is contained and usually recycled, and it is only when the recycling process breaks down that substantial amounts of lead enter the environment, as via landfill sites (Thomas and Orlova 2000). Thus, even though shot production accounts for only 7-8 per cent of annual total world lead production, the absolute amount of lead that enters the environment directly from this source is probably far higher than this percentage indicates.

As with lead shot, the amount of lead entering aquatic habitats each year from lost fishing weights can only be estimated. The latest estimates for the USA and Canada report that 3977 and 559 t of lead, respectively, are used annually in these countries to make weights (Scheuhammer et al. 2002). Although not all fishing weights are destined to be lost, losses are high (Scheuhammer et al. 2002; Bell et al. 1985). The U.S. Environmental Protection Agency (1984) estimated that more than 450 million lead and/or zinc fishing weights are lost to aquatic environments each year. Comparable data for other countries are not available at present. However, given the popularity of angling in many countries, and the predominant use of lead for weights, commensurate figures for lead weight production and losses are plausible.

Progressive Adoption of Non-toxic Products

Lead poisoning in waterfowl has been reported in over 21 countries (Beintema 2001): this number would be higher if the lead poisoning known to occur in upland species were added. Between 1991 and 2001, eight nations had placed a ban on the use of lead shot for hunting waterfowl (Beintema 2001). This is due to there being a large amount of scientific evidence of lead toxicosis of waterfowl in those countries, coupled with the existence of legislation that attempts to regulate other forms of environmental contamination. Geographically, North America and Scandinavia is where the greatest effort to eliminate the use of lead shot is seen, in addition to The Netherlands and Switzerland. These bans apply mainly to the hunting of waterfowl species; only Denmark and The Netherlands have extended the ban to the hunting of all game species, whether found in wetlands or uplands. This is despite the evidence that lead poisoning of upland species of wildlife occurs (Kendall et al. 1996; Scheuhammer et al. 1999). Consequently, a large market for traditional lead shot ammunition continues to exist, in addition to that used by clay target shooters. Countries that practice a lot of hunting, but where there is a dearth of scientific information on the prevalence of lead accumulation and lead toxicosis, such as Italy, Greece and Turkey, show little inclination to adopt non-toxic shot (Beintema 2001). 

Fewer countries have required the use of non-toxic fishing weights for angling. England banned lead weights commonly used in angling to reduce the mortality of swans (Cygnus olor) from lead poisoning (Birkhead 1982), and Canada placed a similar ban on the use of lead weights in all national parks and national wildlife areas in 1997. The USA has prohibited the use of lead fishing weights in 17 specific areas (Scheuhammer et al. 2002). Given the number of countries that practice recreational shooting and angling, it is clear that the phase-out of lead products is in its infancy, but the list of countries is growing slowly (Beintema 2001).

Benefits of Using Non-Toxic Products

The USA has had 11 years in which to evaluate the effectiveness of its national non-toxic shot policy. Banning the use of lead has produced a dramatic saving of waterfowl by reducing the prevalence of fatal lead poisoning. After only 5–6 years of non-toxic shot use, the mortality of mallard ducks (Anas platyrhynchos) of the Mississippi flyway from ingested lead shot was reduced by 64 per cent. This saving, together with those from other species, was estimated to have added an extra 1.4 million birds in just one year to the US population (Anderson et al. 2000). Further American studies confirm the role of non-toxic shot in lowering the prevalence of lead toxicosis in waterfowl (Samuel and Bowers 2000).

The saving of an estimated 1.4 million waterfowl in one year has to be compared with other initiatives to conserve waterfowl in North America. The North American Waterfowl Management Plan is a 15-year plan devised to increase the size of continental waterfowl populations by acquiring and improving wetland habitats. The goal of the plan is to add 750,000 birds each year to the population, at an average cost of US$100,000 a year (Norton and Thomas 1994). Clearly, the use of non-toxic shot throughout the flyways is contributing many more birds a year than investment in habitat improvements. Furthermore, the costs of reducing lead poisoning have been internalised entirely among the hunters who pay for the higher costs of non-toxic ammunition, whereas funding to undertake habitat restoration is provided partly by public funds. This is a very good case of the Polluter Pays Principle in action (Rio Declaration on Environment and Development 1992). Insofar as this approach has been shown to work in North America, it should yield similar benefits in Europe, or any other part of the world where waterfowl hunting occurs.

A positive effect of banning lead fishing weights upon the national population of English swans was reported (Delany et al. 1992), in which the population size increased 37 per cent from 1983 to 1990. No other confirmatory studies exist, due largely to the fact that few jurisdictions have required the use of non-toxic weights, and even fewer are monitoring the consequences.  These reported savings of wildlife should not detract from the fact that there is an enormous tonnage of lead shot and fishing weights, accumulated over the centuries, and lying in wetlands, uplands and water bodies, awaiting ingestion by birds. Extremely high densities of spent lead shot have been reported in wetlands (Pain 1992a; Mateo et al. 1997). These pellets will remain there and contribute to lead poisoning of birds in the future because there is no requirement in any country that has banned lead shot for spent lead shot or weights to be recovered. Thus, while lead-producing and polluting industries are subject to clean-up and site remediation, the hunting and angling public is exempt, especially on publicly-owned lands and waters. The high densities of remaining lead shot are encountered occasionally by migratory birds, resulting in large-scale mortality for several years. Adoption of nontoxic shot will reduce the prevalence of such die-offs in future, but may never eliminate them.

Developing Better Policy for Remediation of Lead

Toxicity In every nation, the shooting, hunting and sport fishing communities that use lead products have shown themselves unwilling to press for reform of the issue of lead shot and weight use. The voluntary approach to using lead products does not work because there is no real obligation to comply. Therefore, there is little inducement for industry to develop and market substitutes widely, a fact that further confounds voluntary use by negating broad availability of non-toxic substitutes. Commoner (1990) suggested that, in the USA, the most successful environmental remediation has all resulted from legal bans of products because this provides the basis for regulation and public compliance. Thomas and Orlova (2000) cautioned that attempting to reduce pollution without first developing alternate technologies will be met by major non-compliance, thus requiring extra enforcement on the part of governments. In the case of lead shot and fishing weights, technology has produced effective substitutes, but there is still the problem of inducing public change in many countries. It is opined that enforced, legal bans provide the means for change on the part of sportsmen, and simultaneously, provide the incentives for industry to make alternative products available.

Given the evidence for a single lead pollution problem in both human and natural environments, it is not expedient policy for governments to attempt to deal with specific types of lead pollution (e.g. leaded gasoline or lead shot) individually, on a case by case basis, especially when substitutes are available. This piecemeal approach fragments the issue across different levels of a country’s government, and also across different departments/ministries of a government. This is evident in all the nations of North America, Europe and Australasia that have addressed lead pollution, and it results in inconsistent policy and legislation (if any).

Lead shot and fishing weights are privately-owned commodities that, through use and loss, quickly become public environmental pollution problems. Hunters, shooters and anglers who use lead materials simply externalise the pollution problem to the rest of society and its wildlife. Then the most expedient way to deal with the problem is to treat it at the level of broad, national pollution prevention, using the appropriate legislation. This is what was intended by the Canadian Standing House Committee on Environment and Sustainable Development when it recommended that Canada ban all use, import and manufacture of lead shot and fishing weights under the Canadian Environmental Prevention Act (Caccia 1995). Such legislative action removes the issue from legislation pertaining only to the regulation of hunters and anglers, and deals more realistically with the legacy of lead products already in the environment. More importantly, it removes the issue from one of use by a specific sporting interest group, and deals with it by preventing the potential pollutant from becoming available in the first place. Broad environmental legislation is, generally, better able to address the concerns of diverse environmental components than specific legislation addressing hunting and angling. Thus, under the provisions of an environmental protection act, the known lead contamination of groundwater, soil and vegetation (Thomas 1997b) can be addressed more effectively.

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