77
(7.1 +/- 9.0 µg(Pb)/g dw). An experiment in which earthworms
collected from both sites were exposed to soil that had been
artificially augmented with lead found a decrease in condition
of earthworms from the control site, but not of those from the
shooting site, suggesting the development of high tolerance to
lead in the shooting site worms.
Exposure to lead from ammunition sources in areas of high
shooting intensity has been reported to have impacts on small
mammals and amphibians. White-footed mice Peromyscus
leucopus and green frogs Rana clamitans sampled within the
shot-fall area of a shooting range with high pellet density had
depressed ALAD enzyme levels (Stansley and Roscoe 1996), a
recognised indicator of sub-clinical lead toxicosis in mammals,
and the mice also had reduced haemoglobin levels. Stansley
et al. (1997) exposed eggs of pickerel frogs Rana palustris
and bullfrogs R. catesbeiana to 0, 25, 50, 75 and 100% lead-
contaminated surface water from a trap and skeet range. Total
lead concentrations in 100% range water treatments varied
from 840–3,150 μg/l, with the filterable form accounting for
approximately 4–5% of the total. Hatching was not affected in
either species but there was highly significant mortality (100%
and 98%) in pickerel frog tadpoles after 10 days of exposure
to 100 and 75% range water; mortality was not significantly
increased in bullfrogs.
It has been shown experimentally that pigeons Columbia livia
dosed with soil contaminated with lead from a shooting range
absorbed lead in a dose-response manner as reflected in blood,
tissues, feathers and erythrocyte protoporphyrin, a biomarker
of lead effect (Bannon et al. 2011). In the field, Vyas et al. (2000)
found elevated erythrocyte protoporphyrin levels in some
ground foraging passerines held in aviaries in the vicinity of a
clay pigeon shoot in Maryland, USA, relative to controls. The
authors could not determine whether this was from ingestion
of one or a combination of shot directly, degraded shot in soil
(soil can be an important routes of exposure to lead in some
bird species and situations (Beyer et al. 1998)) or other lead-
contaminated dietary components. A case of lead poisoning has
also been described in a grey squirrel Sciurus carolinensis in the
vicinity of a law enforcement firing range in Georgia, USA (Lewis
et al. 2001).
These studies, and those cited in preceding sections, show
that where invertebrate and vertebrate animals are exposed to
elevated levels of lead of ammunition origin, irrespective of the
exposure route (i.e. ammunition fragments, soil, water or biota)
it can exert sub-lethal negative effects on animal physiology
(i.e. both welfare and individual survival) in many species, and
in some animals may cause mortality. Effects are related to
exposure levels and amounts absorbed, thus animals (e.g. birds)
ingesting ammunition fragments directly are at particularly
high risk as described in preceding sections. Nonetheless, local
effects on a range of wildlife in areas of intensive ammunition
use appear likely in many exposed species. While some inter-
specific differences in susceptibility to the effects of lead occur
across many taxa, the few studies available suggest that this
may particularly be the case in invertebrates, with the possibility
that this may be acquired (for one species studied). Insufficient
data exist to be able to evaluate numbers of animals potentially
affected via routes other than direct ingestion of ammunition
fragments by birds.
CONCLUSIONS
The toxic effects of lead on humans and other vertebrates
have long been known and most uses of lead causing elevated
exposure to humans and wildlife have been phased out or
heavily regulated across most of the world (Stroud 2015).
Lead derived from ammunition now appears to be the most
significant geographically widespread and common source
of unregulated environmental lead contamination to which
wildlife is exposed. Lead from ammunition has primarily been
studied in birds, with the two main exposure pathways being
direct ingestionof spent gunshot (e.g. bywildfowl and terrestrial
gamebirds), and ingestion by predators and scavengers of
lead gunshot, bullets, or fragments from these, in the flesh of
their prey. Thousands of tonnes of lead ammunition, primarily
gunshot, is deposited and accumulates in the UK environment
every year. Lead ammunition degrades very slowly, and while
deposited gunshot settles through soils and sediments it may
take several decades to become unavailable to feeding animals.
Predators and scavengers can be exposed to lead in dead and
unretrieved game, discarded viscera from shot deer, and in the
flesh of prey that have been wounded but survived. Studies on
a variety of species/populations of live wildfowl have shown
that a high proportion individuals (an average of >20% across
22 species) carry gunshot in their flesh.
Studies of exposure to, and poisoning by, lead from ammunition
inbirdshave included: experimental dosingstudies, postmortem
examinations of birds, X-radiography studies of live birds for
incidence of ingested ammunition or fragments, examination of
regurgitated pellets for ammunition or ammunition fragments,
Lead poisoning of wildlife in the UK