EXPOSURE ROUTES

There are four main routes bywhich birds and other wild animals

(vertebrates and invertebrates) can be exposed to ammunition-

derived lead:

Direct ingestion of spent lead gunshot deposited in the

environment. This affects mainly wildfowl, other waterbirds

and terrestrial gamebirds.

Ingestion of lead gunshot or bullets, or fragments from

these, in the flesh of either dead or living animals that

have been shot but remain unretrieved. This affects mainly

predatory or scavenging birds, primarily raptors, and

potentially some carnivorous mammals.

Ingestion of soil, water, or lower organisms contaminated

with lead that has degraded from lead ammunition and

entered the environment.

Absorption of lead mobilised from pellets shot into the

tissues of animals that have been wounded but survived.

The first two of these appear to be the most significant exposure

routes. We do not deal with the last exposure route in this paper

because, while there is strong evidence that embedding of lead

ammunition occurs (

e.g.

see Table 1), there is uncertainty about

whether this causes increases in tissue lead levels. While there

is evidence that ducks with embedded lead gunshot survive

less well (Tavecchia

et al.

2001), this might be due to wounding,

irrespective of gunshot type, rather than the toxic effects of

absorption of lead from embedded gunshot.

The exposure routes plus the outcomes are illustrated and

summarised in Figure 1.

Figure 1:

Schematic illustrating and summarising the 4 exposure routes (see text) and range of impacts on wildlife of poisoning from lead

ammunition sources.

Lead poisoning of wildlife in the UK