Toxic lead shards in wild pheasants pose a human health risk

The meat of wild game animals is commonly eaten in many households across the EU and UK. In these two regions alone, about five million people eat at least one meal of game meat per week. Figures from the UK show that people consume around 11,000 tons of meat derived from wild-shot game birds alone each year. 

Most of these animals are shot using lead ammunition. It has always been assumed that the lead is easy to locate and remove from the muscle tissue before consumption. A new study by UK scientists has found that this is not the case – certainly not for wild-shot pheasants that are destined to be food for humans. Instead, their research reveals that pheasants killed with lead shot contain many tiny fragments of the metal that are embedded deep within the tissues and are unlikely to be detected by means of sight or touch. These shards of lead have been shown to come from the ammunition that fractures upon entering the target animal.

The researchers examined the carcasses of eight free-ranging common pheasants that were killed on farmlands using lead shotgun ammunition and were on sale in a UK butcher’s shop. They used a high-resolution computerized tomography (CT) X-ray scanner to obtain 3D images of the carcasses and found that, while only seven of them contained obvious shotgun pellets, all eight contained multiple tiny lead fragments in their flesh. 

The mean number of shotgun pellets identified per pheasant carcass was 3.5 (n=7), while the mean number of smaller (<2 mm diameter) metal fragments per carcass was 39.0 (n=8). Of the 340 embedded metal objects that were identified on the images, 92 percent had a diameter of less than 1mm. The researchers found up to 10mg of tiny lead shards per pheasant, all of which were much too small to be detected by eye or by touch. 

Lead is toxic to humans when absorbed by the body and there is no known safe level of exposure. Lead accumulates in the body over time and can cause long-term harm, including increased risk of cardiovascular disease and kidney damage in adults. It is known to lower IQ in young children, and affect the neurological development of unborn babies. In previous studies using rats it has been found that absorption of lead into the blood stream is enhanced when the lead is in the form of very small particles.

The findings of this study, published in the journal PLoS ONE, indicate that wild-shot pheasant meat is likely to have high levels of lead contamination, even if the obvious large pellets are removed during careful preparation or chewing. 

“While lead gunshot continues to be used for hunting, people who eat pheasants and other similar gamebirds are very likely to be also consuming a lot of tiny lead fragments,” said study first author Rhys Green, a professor in the Department of Zoology at the University of Cambridge.

“It seems to have been widely assumed in the past that a lead shot embedded in a pheasant carcass remained intact, and could be removed cleanly before the pheasant was eaten – removing any health risk. Our study has shown the extent to which this is really not the case,” said Professor Green. “By eating pheasant, people are also unwittingly eating lead, which is toxic.” 

“One pheasant is a reasonable meal for two or three people. Consuming this much lead occasionally wouldn’t be a great cause for concern – but we know that there are thousands of people in the UK who eat game meat, often pheasant, every week.”

There are no UK or EU regulations about the maximum allowable levels of lead in human food from wild-shot game animals. This is in contrast with strict maximum levels for lead in many other foods including meat from cattle, sheep, pigs and poultry, and shellfish harvested from the wild.

Observational studies of humans have found a positive correlation between the concentration of lead in blood plasma and the frequency of consumption of the meat of wild animals killed using lead ammunition. This suggests that some lead derived from ammunition is both ingested and absorbed by human consumers. Since it is impossible to locate and remove all the very tiny shards of lead embedded in the flesh of the animal, it is likely that dietary exposure to ammunition-derived lead and its absorption and significance for public health may be greater than was previously thought. 

Steel shotgun pellets are a practical alternative to lead, and their use in place of lead for hunting is recommended by UK shooting organizations. But there is very little evidence of a voluntary switch away from lead being made by hunters. The UK Health & Safety Executive is currently preparing a case for banning the use of lead ammunition for hunting in the UK, and the European Chemicals Agency is doing the same for Europe.

Other game, including partridge, grouse and rabbit, is also mainly shot using lead shotgun pellets, and wild deer are shot using lead bullets. Hunters often remove the guts of deer carcasses to make them lighter to carry, and the discarded guts – which often contain many bullet fragments – are eaten by wildlife, which then also suffer the harmful effects of lead toxicity.

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By Alison Bosman, Earth.com Staff Writer