Use of Lead Fishing Sinkers and Lead Shot in Canada
Position
“The Canadian Veterinary Medical Association (CVMA) opposes the use of lead fishing weights and lead shot due to their direct and indirect toxicity to wild animals. The CVMA strongly supports the use of non-toxic materials for hunting and angling purposes.”
Background
Lead toxicity has been well described in wildlife species, particularly swans and other waterfowl with respect to lead shot; and loons with respect to lead fishing weights or jigs. Waterfowl mistake spent lead shot for food or grit and ingest it when they feed at the bottom of lakes or ponds or in agricultural fields. Raptors such as eagles can be secondarily poisoned after eating an animal containing embedded lead ammunition fragments. Secondary lead poisoning from the ingestion of bullet fragments represents a major threat to the successful re-introduction of endangered California condors into the wild (Church et al. 2006).
The clinical effects of lead poisoning are well documented. Birds with lead poisoning often have physical and behavioural changes, including loss of balance and inability to fly. Even when signs of lead poisoning are not obvious, birds may still have trouble feeding, mating, nesting, and caring for young. Acute toxicity can occur after the ingestion of a single lead sinker and can result in the death of a bird within a few days. The ingestion of a single lead sinker or lead-headed jig is sufficient to expose a loon or other bird to a lethal dose of lead.
In eastern North America, lead poisoning from sinker and jig ingestion is a leading cause of death reported in adult Common Loons during the breeding season in environments where sport angling is popular, exceeding observed mortality associated with trauma, disease, entanglement in fishing line, and gunshot wounds (Scheuhammer et al. 2003). Between 100 and 500 Trumpeter and Tundra Swans have died each year in north-western Washington and south-western British Columbia since 1999 (total exceeding 2,350). The major cause of these deaths is poisoning from ingesting lead shot. The actual losses from lead poisoning cannot be accurately determined as many carcasses are scavenged or never found. A 1995 report (1), estimated the annual loss of waterfowl in Canada from the ingestion of lead was 2 – 3 % or 240,000 to 360,000 birds.
Lead shot is stable in most soils (Pattee & Pain, 2003). Inorganic lead (used in lead shot) in soils and sediment is not readily available to plants (Henny, 2003). Although lead shot pellets are broken down (oxidized) in the environment, the transformation occurs very slowly in most (non-acidic) soils or sediments, and pellets will likely be relatively intact for many tens, or even hundreds, of years. Some of these transformation compounds may be bioavailable and absorbed from the soil by plants (Hui, 2002) and soil invertebrates. Although millions of waterfowl have been killed by lead, the source has generally been lead shot and fishing sinkers rather than contaminated biota or sediments (Henny, 2003). In some areas, the amount of lead deposited in the environment from hunting and target shooting have exceeded the requirements for the soil to be classified as hazardous waste.
Lead is identified as toxic under the Canadian Environmental Protection Act (CEPA) and fishing gear now accounts for about 18 per cent of the uncontrolled release of lead entering and polluting the environment. Canada has required non-toxic shot in national wildlife areas since 1995, in wetlands since 1997, and for hunting most migratory game birds across the nation since 1999. Lead exposure in ducks in Canada has declined dramatically since non-toxic shot regulations were established (Stevenson et al. 2005). In 1997, Canada also banned lead fishing sinkers and jigs weighing less than 50 grams in national parks and wildlife areas. Enforcement is difficult but government agencies and interest groups are using educational programs to inform the public about the hazards of lead. Despite such efforts, anglers still purchase over 500 tons of lead tackle annually and hunters purchase approximately 1,600 tons of lead shot. The use of lead shot is still legal for most upland hunting, and for target shooting. Environment Canada is currently consulting with stakeholders under the CEPA process to develop further controls aimed at eliminating the use of lead for making small fishing sinkers and jigs.
Partial bans are not as effective as full bans due to problems with enforcement and reduced incentive to produce non-toxic alternatives. As long as lead is legal it remains the most readily available product because of the relative ease of manufacture and slightly lower price. Less toxic alternatives such as bismuth, steel, tin or clay are produced and are not poisonous to birds.
References
1. Canadian Wildlife Service. Fish Lead Free – from http://www.cws-scf.ec.gc.ca/publications/fishing/fish_e.cfm
2. Scheuhammer, A.M. Norris, S.L. (1995). A Review of the Environmental Impacts of Lead Shotshell Ammunition and Lead Fishing Weights in Canada. Canadian Wildlife Service Occasional Paper No. 88, Environment Canada, Ottawa, 54pp.
3. Pattee, O.H. and D.J. Pain. 2003. Lead in the Environment. In: Handbook of Ecotoxicology. 2nd Edition. D.J. Hoffman, B.A. Rattner, G.A. Burton Jr., J. Cairns Jr., Lewis Publishers. CRC Press LLC, Boco Raton, Florida, USA, pp. 373-408.
4. Henny, C.J. 2003. Effects of mining lead on birds: A case history of Coeur d’Alene Basin, Idaho. In: Handbook of Ecotoxicology. 2nd Edition. D.J. Hoffman, B.A. Rattner, G.A. Burton Jr., J. Cairns Jr., Lewis Publishers. CRC Press LLC, Boco Raton, Florida, USA, pp. 755-766.
5. Hui, C.A. 2002. Lead distribution throughout soil, flora, and an invertebrate at a wetland skeet range. Journal of Toxicology and Environmental Health, Part A. 65:1093-1107.
Further references
Church, M.E., Gwiazda, R., Risebrough, R.W., Sorenson, K., Chamberlain, C.P., Ferry, S., Heinrich, W., Rideout, B.A., and Smith, D.R. 2006. Ammunition is the principal source of lead accumulated by California Condors re-introduced to the wild. Environ. Sci. Technol. 40: 6143-6150.
Scheuhammer, A.M, Money, S.L., Kirk, D.A., and Donaldson, G. (2003). Lead fishing sinkers and jigs in Canada: review of their use patterns and toxic impacts on wildlife. Canadian Wildlife Service Occasional Paper no. 108, Environment Canada, Ottawa. 48 pp.
Stevenson, A.L., Scheuhammer, A.M., and Chan, H.M. (2005). Effects of lead shot regulations on lead accumulation in ducks in Canada. Archives of Environmental Contamination and Toxicology 48, 405-413.
(Revised July 2007)