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Average levels of lead in game meat, measured in recent years,
have been many times higher than the suggested maximum
permissible concentration in domestic meat. Some individual
meals prepared from gamebirds killed with lead shot have over
one hundred times the maximum permissible level for domestic
meat (Green and Pain 2015).
Since the impacts of lead are largely hidden, usually undetectable
without medical study, we can reasonably assume that we have
much bigger human health problems caused by lead ammunition
thanpreviouslyrecognised.Leadpoisoningcouldpotentiallyaffect
people anywhere in theUK, if they eat wildwaterfowl or game, but
particularly those for whom wild game forms a significant part
of the diet (such as some of the shooters themselves and their
families and associates). Diabetes, mental and renal problems are
some familiar illnesses that are known to be exacerbated by lead.
Recent surveys have shown that, among the hunting community
alone, up to 12,500 children in the UK are now exposed to dietary
ammunition-derived lead from game meat in sufficiently large
amounts to be at risk from some health consequences (as defined
by the European Food Safety Authority).
Effects on wildlife
Lead is similarly toxic to a range of other vertebrates, especially
mammals and birds. Some species, such as waterfowl, game
birds and pigeons, ingest spent gunshot incidentally along
with the grit needed in food breakdown, while meat-eating
scavengers ingest lead fragments from the carcasses and
discarded gut piles of shot animals on which they feed. A deer
shot through the thorax with a lead bullet may have large
numbers of lead fragments in the pile of viscera discarded in the
field by the hunter. Worldwide, more than 130 wild bird species
are known to be affected in this way. In some species thousands
or tens of thousands of individuals die from lead poisoning every
year in North America alone. There is no reason to think that the
situation is much different in Europe. These incidental casualties
include quarry species which the hunters themselves would
otherwise seek to preserve. Recent estimates imply that some
50,000-100,000 waterfowl may die of ingested lead poisoning in
the UK each year (Pain et al. 2015). This lead poisoning does not
normally produce obvious mass mortalities of the type that can
result from disease, because birds die slowly through the year,
a few at a time, their carcasses swiftly removed by scavengers.
Lead-caused mortality is therefore largely hidden, invisible to
the average hunter or country-dweller.
While this incidental mortality of waterfowl, game birds and
scavengers may be substantial, we have few assessments of
its effects on population levels. For lead-poisoning to reduce
a population, or cause it to be smaller than it would be in the
absence of lead, it has to be additive to other deaths, and
not compensated by reduction in other mortality. However,
quantitative circumstantial evidence indicating population-
level effects is available for some waterfowl (Mateo 2009), and
for some scavenging birds of prey, such as eagles and vultures
(various in: Watson et al. 2009). Such evidence is available for
the white-tailed eagle Haliaeetus albicilla in central Europe and
the Steller’s sea eagle Haliaeetus pelagicus in Japan (the latter
problem having been reduced recently by a legal ban on lead
bullets). The evidence on population effects is particularly
striking in the California condor Gymnogyps californianus in
North America, which can no longer maintain a self-sustaining
population in its historic range: the mortality from ingested
lead-based ammunition well exceeds its natural reproductive
rate. Wherever lead-based bullets of current design are used as
now in game hunting, it is recognised that the condor is unlikely
to survive without intensive remedial intervention anywhere in
North America. It is being kept from extinction in the wild only
by a programme of conservationmanagement involving annual
releases of captive-bred birds, coupled with veterinary care,
involving frequent capture of wild individuals and treatment to
reduce their blood-lead levels (Green et al. 2008).
Of course, we are not concerned with Condors in Europe, but
southern and central Europe has vultures that are certainly
affected by lead, though population-level effects have not been
documented. And northern Europe has scavenging raptors that
are exposed to ammunition-derived lead, but again no research
to examine population-level effects has been done.
If lead ammunition was banned, given all the lead already
in the environment, how can we be sure that such a ban
would reduce the mortality of affected species, and that their
populations (if reduced by lead) would recover? Well, first
of all, the uptake of lead by waterfowl and others is much
greater in the shooting season than during the rest of the
year, which implies that birds are ingesting recently-applied
lead, not older stuff much of which presumably eventually
sinks into the substrate, putting it beyond reach. A seasonal
cycle in lead uptake is also apparent in raptors and other
scavengers that feed on the carcasses of quarry species (Pain
et al. 2015). Most strikingly, however, we have the example of
the sedentary mute swan Cygnus olor in Britain (Perrins 2015).
Oxford Lead Symposium: closing remarks