Lead is toxic to all life with no safe threshold for exposure. It is a general toxin that affects virtually all systems in the body such as the nervous and reproductive systems1. First reported in the 1870s2, lead ammunition – or lead shot – poisoning has been widely recognised as a threat since the mid-1900s following wildfowl deaths in the USA, France, Italy, Britain, and some Scandinavian countries3. Lead poisoning is now a well-known issue for humans, domestic animals and wildlife alike, with lead shot posing a particular threat to wildfowl4. Wildfowl are birds such as ducks, geese, swans, moorhens and coots.
Why is lead dangerous to wildfowl?
Lead is a widely used material in shooting sports. Despite restrictions, which are detailed below, spent lead pellets can become available in habitats used by wildfowl4. These birds accidentally ingest spent lead pellets when feeding by mistaking the pellets for items of food or grit, which they use to grind down food5. Lead pellets are then directly ingested or are slowly ground down in the gizzard of the bird. This leads to varying degrees of acute or chronic lead poisoning6.
What is the effect of lead on wildfowl?
Lead has significant harmful impacts on wildfowl. Symptoms of lead shot poisoning vary because lead is a ‘non-specific’ toxin, meaning it can affect the whole body1. Characteristic symptoms include1,2,7:
- Weight loss and muscle wastage
- Anaemia, weakness and lethargy
- Loss of vision and depth perception
- Seizures, convulsions and paralysis of limbs
- Green diarrhoea
- Wing drooping
- Lack of coordination, balance and mobility
Two of the main symptoms are muscle wastage and paralysis, which can affect the throat, gizzard and digestive system of poisoned birds. This means that eating becomes very difficult, leading to extreme weight loss and starvation8. Research in laboratories and on wild birds has shown that poisoned birds have problems with growth, development and reproduction9. Poisoned birds often exhibit changes in their behaviour, having more accidents10 and failing to avoid predators6,10,11. They also become more vulnerable to disease and parasites1,9.
Birds suffering from lead shot poisoning often die. This could either be directly because of levels of lead in their body, or because of related issues caused by increased lead levels such as starvation, predation or accidents4. Trials in mallard ducks show that the chance of a duck surviving the month decreases by 19% after ingestion of a single lead pellet12. In cases of high exposure, birds might not display any symptoms before dying1,8.
Where birds repeatedly consume lead pellets, levels of lead have the potential to build up in the body2. Consumed pellets erode in the stomach and gizzard, after which toxic lead salts enter the bloodstream and can be deposited in the kidneys, liver, bones and feathers1,13. Stored lead can also leach out of bone in female birds during egg production when the bird requires more calcium than normal1,14. Levels of lead can remain high in the blood and tissues for months at a time, persisting in bone for much longer15.
How quickly does lead poisoning happen?
When wildfowl ingest lead pellets, they fully erode and absorb into the body within 2-3 weeks2,10. Blood lead levels generally peak two days after ingestion and take up to 36 days to return to normal16. This means that in a single year, a bird can consume multiple loads of lead pellets and experience several episodes of poisoning. This results in prolonged sub-lethal effects, suffering and potential death10,16.
Why are wildfowl susceptible to the harmful effects of lead?
Wildfowl find food by diving or dabbling in water – looking for insects, molluscs, seeds, vegetation, roots and other food17. Because of this wildfowl are likely to ingest pellets, by accident, that have fallen in and around bodies of water. Lead pellets are mistaken for food or grit, which birds use to grind up food in the gizzard. This means that pellets are directly consumed or eroded in the gizzard11.
Are some species more at risk?
Any duck, goose, swan, coot or moorhen that feeds in an area where lead shot is used is at risk of lead poisoning9,16.
Studies suggest that swans (particularly Bewick’s and whooper swans) and geese are more susceptible to lead shot poisoning. Swans and geese commonly forage on agricultural land over which it is often legal to shoot with lead shot (depending on UK country specific legislation)4. Swans may also require particularly large quantities of grit when consuming more indigestible foods such as potatoes, corn and barley and so are more likely to ingest spent shot4.
Diving ducks – such as tufted ducks, pochard and goldeneye – are very likely to ingest lead pellets instead of grit, because they eat larger seeds5. They are exposed to lead shot when they gather food from the bottom of ponds and lakes, where the sediment is too compact for lead shot to sink out of reach4. Dabbling ducks – such as mallards, wigeon, and gadwall – mainly eat plant leaves and so are generally thought to be less at risk9.
In recent years scientists have found that ducks and swans can suffer lead shot poisoning at lower levels than previously realised15.
How big is the problem?
Scientists estimate that millions of birds suffer from sub-lethal effects of lead shot every year throughout Europe11. Research estimates suggest that between 30-60,00010 and 50-100,0001 birds are likely to perish in the UK each winter as a direct result of lead shot poisoning. Long-term monitoring found that 8.1% of birds found dead between 2000 and 2010 had died from ingesting lead pellets4,18. Some animals had ingested hundreds of pellets11.
Records of autopsied birds from 1971-2010 showed that 1 in 4 migratory swans and 1 in 10 wildfowl exhibited lead shot poisoning as the cause of death4,10. A total of 42.0% of whooper swans that underwent blood tests in winters between 2010 and 2014 also showed high levels of lead in their blood4,8.
Scientists estimate that 1.5-3.0% of wildfowl overwintering in the UK each year die of lead shot poisoning1.
Lead shot poisoning is difficult to quantify primarily due to the likelihood of under-estimation, although some over-estimation is possible. Lead ingestion could be more common than thought because pellets are only present for a short time before they absorb into the body. Lead shot poisoning can also present subtle, sub-lethal effects that are hard to notice9 and result in wildfowl deaths being attributed to other factors4. Birds may also consume lead pellets from other countries when they travel to and from their overwintering sites18. However, research has shown that migratory wildfowl have high blood lead levels in mid-late winter when they are most likely to have been in the UK for several weeks. Given that blood lead concentrations tend to reflect exposures within 35-40 days of testing, it is therefore probable that most will have ingested lead shot in the UK4.
It is important to remember that regardless of the number of wildfowl or other wildlife affected, lead is a harmful toxin that can cause great suffering and death. Any lack of studies providing hard data on lead shot poisoning does not mean that lead is not a serious and noteworthy issue for wildlife10.
Where dead birds are found, what signs of lead poisoning are found in a post-mortem?
When scientists discover dead birds, they will often carry out an autopsy to try to determine the cause of death. Scientists look for specific signs that ingestion of lead pellets was the cause of death, including4,5,7,18:
- Lead pellets in the crop, gizzard, stomach, or intestines
- High levels of lead in the blood
- High levels of lead in the liver, kidneys, bones, or feathers
- Low body weight
- Wastage of the gizzard and liver
- Reduced levels of d-ALAD protein (needed to make blood)
It can sometimes be difficult to find the source of lead in the body. If birds have lead in their blood or organs, as well as in their gizzards or stomachs, it is safe to assume the lead was ingested16. Scientists can also carry out tests for elevated blood levels or lead shot ingestion on live birds through x-rays and blood samples5.
How are the estimates for the number of wildfowl that die from lead poisoning generated?
Scientists can use published, long-term research on live and deceased birds to estimate the number of birds poisoned by lead ammunition. Lead shot poisoning in birds can be confirmed through post-mortem analysis, and in live birds, through taking blood samples whereby elevated blood lead levels are indicative of poisoning4,13. The most recent estimates look at the use of lead shot and the scale of lead poisoning in ducks between 1999 and 2020. These estimates compare data from the GWCT National Gamebag Census19 to shoot surveys and poisoning data1,20.
Various sources of information are needed to estimate annual mortality from lead shot poisoning. This includes (i) the average proportion of wildfowl with ingested shot, derived from UK studies of hunter-shot birds and birds found dead and autopsied; and (ii) the estimated British wintering population of wildfowl1. Adjustments can be made to account for the turnover of lead in the ecosystem and for hunting bias21, as birds that have ingested lead shot are more likely to be shot by hunters because of their weakened state1.
If mortality estimates are relatively high, why are so few dead birds found?
Birds suffering from lead shot poisoning tend to die few at a time and will crawl away, hiding in vegetation away from their flock before they die. This results in less-conspicuous deaths rather than larger die-off events4,22. There is also likely to be a bias towards finding larger birds such as geese or swans, due to their more obvious size and colour2.
Scientists have observed that predators and scavengers often remove poisoned birds before people find them. Trials show that predators remove dead birds in 24-72 hours on average, and 48% of carcasses are completely scavenged within 24 hours22.
Is this likely to result in population-level effects in any species?
Scientists know that lead shot poisoning can affect birth, death and survival rates in wildfowl. Because of that, lead shot poisoning is capable of changing population sizes, growth rates and demographics2,9,10.
Lead ammunition has been used in the UK for so long that before and after data is not available for scientists to study. There is also a lack of UK-based studies providing data to determine if population-level impacts are occurring2,10. However, more recent research on eight duck populations has shown correlations between population growth rates and lead ingestion rates, suggesting that lead shot poisoning has the potential to limit duck populations9.
Population-level impacts are near inevitable for both common and threatened species11. This is because many wildfowl species are migratory and so face many pressures throughout their range1.
How long does lead remain available in the environment for ingestion by wildlife?
Lead is a stable metal and so can persist in the environment for a long time. It can take decades or centuries to fully break down depending on the conditions2,4. Lead pellets can sink into water bodies, soils and sediments as well as remaining available in bird carcasses, which can have a knock-on effect for animals higher up the food chain11.
What about ‘legacy’ gunshot?
Legacy gunshot is ammunition that has been spent or used. There is always a chance of wildfowl consuming old lead pellets, but it is much more likely for an animal to consume recently spent pellets4. That said, historical pellets can accumulate in the environment. Spent lead pellets pose a persistent and significant threat to wildlife23.
Is lead shot the only remaining source of lead exposure for wildlife?
Lead occurs naturally in the environment and as a result, some areas have locally high levels of lead24. Other sources of lead include pollution from industry and agriculture into water and soils25. Illegal disposal of items like lead fishing weights also adds to this but has been banned since 19872,4.
Does lead shot have an impact on the wider environment?
Lead is recognised as a highly toxic substance to both humans and wildlife. Because of this, it is near-inevitable that it will have a negative impact where it occurs10.
Shooting sports in the UK release 5,000-6,000 tonnes of lead ammunition into the environment every year. Some 2,040 tonnes of this ammunition is released into the rural environment10,18. There are no precise estimates of exactly where this lead shot is dispersed. This is because there are no official estimates of the number of animals shot, cartridges fired, or shoot participants18.
In addition to wildfowl, other animal groups are affected by lead shot poisoning. Raptors and scavengers can become poisoned when they consume carcasses or live prey that contain lead shot, and lead shot may also present a risk to foraging game birds1,10.
There is as yet little evidence of the impact of lead on other species of wildlife10. There is also not much knowledge about how lead shot interacts with the environment as it degrades. But it is widely accepted that the effect of lead increases with the dose. Some research shows that lead can have varying effects on over 60 non-wildfowl species, including passerine birds, mammals and amphibians. There is also some evidence that lead can be absorbed by plants and soil micro-organisms10.
There are several routes in which lead can reach wildlife and cause poisoning, including10:
- Direct ingestion of spent lead shot from the environment
- Indirect ingestion of spent lead shot by predators/scavengers in the bodies of their prey
- Movement of spent lead shot via plants
- Movement of spent lead shot via soil organisms/invertebrates
- Movement of spent lead shot from embedded shot/bullets into body tissues
Is this why lead ammunition was banned over wetlands across Europe?
In January 2021, European Union (EU) member states voted to introduce a ban on the use of lead shot in wetlands across the EU. The ban will apply from February 2023 in all EU states, harmonising and extending existing wetland-related legislation of 22 EU states26. It will introduce a ban on lead shot over wetlands for the first time in Poland, Ireland, Romania, Slovenia and Malta27.
The ban was introduced under the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) framework. This followed an investigation by the European Chemicals Agency into the risks of lead to human and environmental health26.
Is this legislation the same across the UK?
No, the rules and legislation for the use of lead ammunition are different in each part of the UK.
The Environmental Protection (Restriction on Use of Lead Shot) Regulations were introduced in England in 199928 following a four-year voluntary phase-out29. Regulations were introduced in Wales in 200230; Scotland in 200431; and Northern Ireland in 200932. England is the only country in the UK that carries out compliance monitoring for this legislation9.
In England and Wales, the rules are28,30:
- No lead use on or over any area below high-water mark of ordinary spring tides.
- No lead use on or over Sites of Special Scientific Interest (SSSIs) included in Schedule 1 of the regulations.
- No lead use when shooting any species of duck, goose, swan, coot or moorhen.
In Scotland and Northern Ireland, the rules are31,32:
- No lead use for shooting any species on or over any wetland habitats
Is there evidence of non-compliance with existing lead ammunition legislation?
Compliance with lead shot restrictions can be monitored through methods such as:
- Analysis of soil and sediments for lead shot
- Analysis of shot wildfowl
- Surveys of cartridge manufacturers
- Analysis of wildfowl purchased from game dealers
- Surveys of shooters and landowners
Scientists at the Department for Environment, Food and Rural Affairs (DEFRA), ADAS UK, the Wildfowl & Wetlands Trust (WWT), and the British Association for Shooting and Conservation (BASC) carry out surveys assessing compliance. Recently these organisations studied samples of shot wildfowl alongside member surveys20.
These surveys found that over the winters of 2001-02, 2008-09, 2009-10 and 2013-14 over 70% of ducks sold by game suppliers were shot with lead20,33. Surveys of BASC members found at 45% of respondents admitted they ‘sometimes or never comply’ with lead shot restrictions20. Surveys of live birds in 2010-11 using blood samples also showed that 33% of birds sampled had elevated levels of lead in their blood4.
Long-term research found that between 1999 and 2020, an estimated 12.9 million ducks were illegally killed with lead shot in England. This equates to an average of 586,000 a year29. There was no recorded difference in wildfowl deaths attributed to lead shot from 1999-20104,9,29.
As a result of this data, it is fair to assume that compliance with current regulations on and around wetlands is low in England10,33. The GWCT condemns this illegal activity and has emphasised the need for compliance in its publications.
Would changing to lead-free ammunition help?
Lead ammunition is the largest source of human-induced lead emissions into soil34. Use of lead shot continues to the detriment of human health, animal welfare, and the environment35.
Use of non-lead shot means there can be no argument about game shooting using toxic material. In February 2020 the GWCT released a statement with other countryside organisations advocating for a voluntary phase-out of lead shot36.
In March 2021, we also asked our members to complete a survey on lead ammunition usage. Of 2,436 respondents, more than 24% stated they have started to test lead shot alternatives or have stopped using lead altogether. Another 27% of respondents said they were going to start testing lead alternatives next season37.
Are lead shot alternatives any good?
Field trials of steel and lead shot were carried out in Denmark, the Netherlands and Belgium. The trials found that there is no difference in the killing ability of lead and steel shot35. The European Chemicals Agency (ECHA) also found that lead shot alternatives are practically and financially feasible11.
What is happening in other countries?
A total of 33 countries across the world have partial or total bans on the use of lead shot in hunting23.
Lead shot was banned for wildfowl hunting in the USA in 199138. Because of this scientists estimate that approximately 1.4 million ducks were spared from lead poisoning in 1997 alone4,39. The Netherlands also banned the use of lead shot in all hunting in 199340.
Denmark banned lead shot in 1996 following slow uptake to a regulation introduced in the 1980s. Compliance with this ban is now close to 100%, and has reduced levels of environmental lead and its effects23.
- Pain, D.J., Cromie, R.L. & Green, R.E. (2015). Poisoning of UK birds and other wildlife from ammunition-derived lead. In: The Oxford Lead Symposium. Lead Ammunition: understanding and minimising the risks to human and environmental health.: 58–84. (eds. Delahay, R.J. & Spray, C.J.) Edward Grey Institute, University of Oxford. Oxford.
- Pain, D.J. & Green, R.E. (2014). An evaluation of the risks to wildlife in the UK from lead derived from ammunition. Lead Ammunition, Wildlife and Human Health: Appendix 4. Department for Environment, Food and Rural Affairs and the Food Standards Agency. UK.
- Mateo, R. (2009). Lead Poisoning in Wild Birds in Europe and the Regulations Adopted by Different Countries. In: Ingestion of Lead from Spent Ammunition: Implications for Wildlife and Humans: 71–98. (eds. Watson, R.T., Fuller, M., Pokras, M. & Hunt, G.) The Peregrine Fund. Boise. doi:10.4080/ilsa.2009.0107
- Newth, J.L., Cromie, R.L., Brown, M.J., Delahay, R.J., Meharg, A.A., Deacon, C., Norton, G.J., O’Brien, M.F. & Pain, D.J. (2012). Poisoning from lead gunshot: Still a threat to wild waterbirds in Britain. European Journal of Wildlife Research, 59:195–204.
- Mudge, G.P. (1983). The Incidence and Significance of Ingested Lead Pellet Poisoning in British Wildfowl. Biological Conservation, 27:333–372.
- Edwards, J.R., Fossum, T.W., Nichols, K.J., Noah, D.L., Tarpley, R.J. & Prozialeck, W.C. (2017). One health: Children, waterfowl, and lead exposure in Northwestern Nigeria. Journal of the American Osteopathic Association, 117:370–376.
- Friend, M. (1999). Lead. In: Field Manual of Wildlife Diseases: General Field Procedures and Diseases of Birds: 317–334. (eds. Friend, M., Franson, J.C. & Ciganovich, E.A.) U.S. Geological Survey. Washington, D.C.
- Newth, J.L., Rees, E.C., Cromie, R.L., McDonald, R.A., Bearhop, S., Pain, D.J., Norton, G.J., Deacon, C. & Hilton, G.M. (2016). Widespread exposure to lead affects the body condition of free-living whooper swans Cygnus cygnus wintering in Britain. Environmental Pollution, 209:60–67.
- Green, R.E. & Pain, D.J. (2016). Possible effects of ingested lead gunshot on populations of ducks wintering in the UK. International Journal of Avian Science, 158:699–710.
- Lead Ammunition Group 2. (2015). Lead Ammunition, Wildlife and Human Health.
- Wildfowl & Wetlands Trust. Tackling lead ammunition poisoning. Available at: https://www.wwt.org.uk/our-work/projects/tackling-lead-ammunition-poisoning/ (Accessed: 7 July 2021)
- Tavecchia, G., Pradel, R., Lebreton, J.-D., Johnson, A.R. & Mondain-Monval, J.-Y. (2001). The effect of lead exposure on survival of adult mallards in the Camargue, southern France. Journal of Applied Ecology, 38:1197–1207.
- Franson, J.C. & Pain, D.J. (2011). Lead in Birds. In: Environmental Contaminants in Biota: Interpreting Tissue Concentrations: 563–593. (eds. Beyer, W.N. & Meador, J.P.) Taylor and Francis. Boca Raton.
- Finley, M.T. & Dieter, M.P. (1978). Influence of laying on lead accumulation in bone of mallard ducks. Journal of Toxicology and Environmental Health, 4:123–129.
- Pain, D.J., Dickie, I., Green, R.E., Kanstrup, N. & Cromie, R.L. (2019). Wildlife, human and environmental costs of using lead ammunition: An economic review and analysis. Ambio, 48:969–988.
- Quy, R. (2010). Review of evidence concerning the contamination of wildlife and the environment arising from the use of lead ammunition: A report to DEFRA. York, UK.
- Pecsics, T., Laczi, M., Nagy, G. & Csörgő, T. (2017). The cranial morphometrics of the wildfowl (Anatidae). Ornis Hungarica, 25:44–57.
- Harradine, J. & Leake, A. (2013). Lead Ammunition and Wildlife in England (UK). Lead Ammunition, Wildlife and Human Health: Appendix 3. Department for Environment, Food and Rural Affairs and the Food Standards Agency. UK.
- Aebischer, N.J. (2019). Fifty-year trends in UK hunting bags of birds and mammals, and calibrated estimation of national bag size, using GWCT’s National Gamebag Census. European Journal of Wildlife Research, 65.
- Cromie, R.L., Loram, A., Hurst, L., O’Brien, M.F., Newth, J.L., Brown, M.J. & Harradine, J. (2010). Compliance With the Environmental Protection (Restriction on Use of Lead Shot)(England) Regulations 1999. Bristol.
- Bellrose, F.C. (1959). Lead Poisoning as a Mortality Factor in Waterfowl Populations. Illinois Natural History Survey Bulletin, 27:235–288.
- Pain, D.J. (1991). Why are lead-poisoned waterfowl rarely seen?: the disappearance of waterfowl carcasses in the Camargue, France. Wildfowl, 42:118–122.
- Kanstrup, N. (2019). Lessons learned from 33 years of lead shot regulation in Denmark. Ambio, 48:999–1008.
- Envirochem Analytical Laboratories. Where is Lead Found? Available at: https://envirochem.co.uk/news/where-is-lead-found.html (Accessed: 25 August 2021)
- Department for Environment Food and Rural Affairs. (2009). Code of Good Agricultural Practice for farmers, growers and land managers.
- European Chemicals Agency. Lead in shot, bullets and fishing weights. Available at: https://echa.europa.eu/hot-topics/lead-in-shot-bullets-and-fishing-weights (Accessed: 24 August 2021)
- European Federation for Hunting and Conservation. (2020). What does the new regulation on banning lead shot over wetlands mean for Europe’s hunters? Available at: https://www.face.eu/2020/12/what-does-the-new-regulation-on-banning-lead-shot-over-wetlands-mean-for-europes-hunters/ (Accessed: 24 August 2021)
- The Environmental Protection (Restriction on Use of Lead Shot) (England) Regulations 1999.
- Stroud, D.A., Pain, D.J. & Green, R.E. (2021). Evidence of widespread illegal hunting of waterfowl in England despite partial regulation of the use of lead shotgun ammunition. Conservation Evidence, 18:18–24.
- The Environmental Protection (Restriction on Use of Lead Shot) (Wales) Regulations 2001.
- The Environmental Protection (Restriction on Use of Lead Shot) (Scotland) Regulations 2004.
- The Environmental Protection (Restriction on Use of Lead Shot) Regulations (Northern Ireland) 2009.
- Cromie, R.L., Newth, J.L., Reeves, J., O’Brien, M.F., Beckmann, K. & Brown, M.J. (2015). The sociological and political aspects of reducing lead poisoning from ammunition in the UK: why the apparently simple solution is so difficult. In: Proceedings of the Oxford Lead Symposium. Lead ammunition: understanding and minimising the risks to human and environmental health: 104–124. (eds. Delahay, R.J. & Spray, C.J.) Edward Grey Institute, University of Oxford. Oxford.
- Tukker, A., Buist, H., van Oers, L. & van der Voet, E. (2006). Risks to health and environment of the use of lead in products in the EU. Resources, Conservation and Recycling, 49:89–109.
- The British Association for Shooting & Conservation. (2021). BASC guide to using non-lead shot for live quarry shooting. Available at: https://basc.org.uk/lead/guide-to-using-non-lead-shot/ (Accessed: 7 July 2021)
- Game & Wildlife Conservation Trust. (2020). A joint statement on the future of shotgun ammunition for live quarry shooting. Available at: https://www.gwct.org.uk/news/news/2020/february/a-joint-statement-on-the-future-of-shotgun-ammunition-for-live-quarry-shooting/ (Accessed: 8 July 2021)
- Game and Wildlife Conservation Trust. (2021). Lead Ammunition Survey – what you’ve told us so far. Available at: https://www.gwct.org.uk/blogs/news/2021/march/lead-ammunition-survey-–-what-you’ve-told-us-so-far/ (Accessed: 31 August 2021)
- Hadoke, D. (2020). Lead shot ban - how have European countries coped? Shooting UK:
- Anderson, W.L., Havera, S.P. & Zercher, B.W. (2000). Ingestion of Lead and Nontoxic Shotgun Pellets by Ducks in the Mississippi Flyway. The Journal of Wildlife Management, 64:848–857.
- Newth, J.L., Lawrence, A., Cromie, R.L., Swift, J.A., Rees, E.C., Wood, K.A., Strong, E.A., Reeves, J. & McDonald, R.A. (2019). Perspectives of ammunition users on the use of lead ammunition and its potential impacts on wildlife and humans. People and Nature, 1:347–361.