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a harmful effect on human health if it were eaten in cooked game
meat. Shot made from iron, tungsten, and bismuth-tin alloy have
been unconditionally approved for use inNorthAmerica (Thomas
et al. 2009). The same shot types can, therefore, be used in other
countries without fear of environmental toxicity. Shot made from
zinc failed the testingandcannot beused legally inNorthAmerica,
and should not be used elsewhere (Levengood et al. 1999). Lead
shot that has been coated with plastic may degrade more slowly
in the environment than uncoated shot. However, the coat can be
ground down rapidly in a waterbird’s gizzard exposing the lead
(Irby et al. 1967). Similarly, damage to the coat, as when pellets
strike the ground, collidewith each other, or hit the target, will still
allow the lead core to be exposed and corrode, releasing lead to
the environment.
Is there evidence that using
non-toxic shot results in reduced
mortality of wildfowl?
Evidence suggests that regulations requiring the use of
alternative ammunition types are very effective, if adhered to.
For example, in theUSA andCanada, themandatory transition to
steel shot for waterfowl hunting in 1991 and 1999, respectively,
resulted in a significant reduction in the mortality of ducks from
lead poisoning within a few years (Anderson et al. 2000, Samuel
and Bowers 2000, Stevensonet al. 2005). Spain has required the
use of non-toxic shot for hunting in its Ramsar sites from 2001,
and since that time, a measurable reduction in lead–induced
mortality has occurred (Mateo et al. 2014). In the UK, a similar
situation occurredwith angler’s leadweights. Mute swanCygnus
olor mortality from lead poisoning following the ingestion of
lead angler’s weights decreased and their population increased
following restrictions on the use of lead angling weights (Sears
and Hunt 1991, Perrins et al. 2003).
In regions of California inhabited by condors Gymnogyps
californianus, a ban on the use of lead-core rifle ammunition
has been in effect since 2007. Consequently, there has been
a significant decline in the blood lead levels of golden eagles
Aquila chrysaetos and turkey vultures Cathartes aura that
would, otherwise, be exposed to secondary lead poisoning from
scavenging the gut piles from shot game (Kelly et al. 2011). Thus
the regulations of the 2007 Ridley-Tree Condor Preservation Act
(Californiastatelawrequiringhunterstouselead-freeammunition
in condor preservation zones) are having the desired effect.
However, regulations do not work if they are not complied
with. In England lead gunshot has been banned for shooting
wildfowl or over certain listed wetlands since 1999. Three
consecutive studies of compliance with the regulations (Cromie
et al. 2002, 2010, 2015) have shown that about 70% of ducks,
shot in England and sourced from game providers and other
commercial outlets, were shot illegally using lead gunshot. The
proportion of wildfowl dying of lead poisoning did not change
following the introduction of legislative restrictions on the use
of lead (Newth et al. 2012) and large numbers of birds continue
to suffer lead poisoning in England.
While legislation that is complied with has been effective at
reducing lead poisoning in birds, in the UK evidence suggests
that partial restrictions (dealing just with certain taxa or habitats)
are unlikely to be effective.
Effective transition to non-toxic ammunition for all shooting
would both remove the majority of the risk to wild birds, and
also substantially reduced risks to the health of humans that
frequently consume game meat.
How do we deal with lack of
compliance with the existing
regulations?
As described in Cromie et al. (2015), compliance with the 1999
regulations requiring the use of non-toxic shot for shooting
wildfowl and over certain listed wetlands in England remains very
low. This is despite long-standing efforts on the part of shooting
organisations to encourage compliance, including a campaign to
this effect in2013. Theremaybemany reasons behind this, but the
difficulty of policing partial regulations, which in England require
the use of non-toxic shot for shooting some species/in some areas,
but allow the use of lead for shooting other species/in other areas,
is likely to play an important part. Under current circumstances in
England, it seems highly probable that many people will continue
to use lead gunshot illegally in the absence of a ban on its use (and
possibly also sale, possession and import) for all shooting.
It is also notable that even where there is a high degree of
compliance with the current regulations, the problem of lead
poisoning would not be solved for the wildfowl species that
graze terrestrial habitats, for terrestrial birds, or scavenging and
predatory birds. Nor would this tackle potential risks to the health
of frequent consumers of game, as most game eaten comprises
terrestrial gamebirds which are currently legally shot with lead.
Vernon G. Thomas, Niels Kanstrup & Carl Gremse