Rodenticides are among the most toxic groups of pesticides widely in use in the UK. Public health pesticides accounted for £3.3 million of sales in 1997 and £3.4 million in 1998 and rodent control is an important public health issue(4). Local authorities use rodenticides to control rat populations in industrial/domestic and agricultural situations. Some 58% by weight of active ingredients and 69% of the amount of bait formulation were applied in industrial and or domestic situations in 1997 plus 28% of active ingredients by weight and 23% of the amount of bait formulation in agricultural situations(5).
Wildlife impacts
Rodenticides were implicated in 61 wildlife poisoning incidents during 1999 – affecting buzzards, red kites, dogs, cats, foxes, a tawny owl and house
sparrows(6). Red kites are a protected species and subject to an ongoing restoration programme but the population could be at risk from birds scavenging on rats killed by rat poison. Rodenticide residues were found in eight kites found in England during
1998/1999(7).
Mustelids (stoats and weasels) are also at risk from secondary poisoning. Traces of rodenticides were found in the livers of 23% of the stoats and 30% of the weasels collected from lowland England in a recent survey. Mustelid poisoning is of particular concern as almost all of their prey are not species targeted by
rodenticides(8).
Increase in UK rodent population
The Rodent Survey carried out by the National Pest Technicians Association (NPTA) in 2000 showed a significant increase in brown rat
(Rattus norvegicus) populations in the UK particularly in the Home Counties region. The data reflects incidents reported to local authorities and has been criticised for not surveying actual rodent
populations(9). Barrie Sheard, the author of the report, explained that the Association decided to conduct the survey in the absence of official scientific data to help members implement strategic rodent control across the
UK(10). The report suggests that the decay of and lack of maintenance funding for an ageing sewerage system, the use of plastic building products, the proliferation of fast food outlets, increasing urban litter, poor hygiene, reduction of local authority pest control funding, and resistance to second generation poisons may be contributing to the increase in
population(11).
Alternative approach
A degree of success in Boston (US) in controlling rat populations was achieved by implementing an integrated approach to control having monitored population numbers and studied animal behaviour. Techniques employed included: maintenance in sewer system in line with behavioural studies;
reduction in available nesting sites in park shrubberies; and laying baits before the breeding season. The general public were involved in the scheme and were encouraged to trim back shrubbery areas in private gardens and reduce the level of street rubbish. As a result of these measures street level rat populations were reduced by
98%(12).
Current data demonstrates the need for an integrated approach to rodent control throughout the UK. A survey needs to be undertaken to ascertain the true level and rate of increase in populations. The risk to public health, to wildlife and our environment needs to be addressed and a programme of integrated control implemented to reduce the impact of highly toxic
rodenticides. (AW)
| Concerns about rodent treatments used in the UK(1,2) | |
| Alphachloralose (NC, I)[M, B]
Harmful by inhalation and if swallowed, subject to Poisons Rules 1982 and Poisons Act 1972, to be used only by persons instructed or trained in use of
alphachloralose. Children, birds and other non-target wildlife are at risk from exposure to baits either directly or by secondary poisoning. Scavengers and predators are at risk of secondary poisoning from dead rodent bodies that have not been collected or have been disposed of in refuse bins or rubbish tips.
Aluminium phosphide (P)[R, M] Liberates very toxic, highly flammable gas fumigant, Subject to Poisons Rules 1982 and Poisons Act 1972, only to be used by operators instructed or trained in the use of aluminium phosphide and familiar with precautionary measures to be taken. Very toxic by inhalation, if swallowed and in contact with skin. Dangerous to fish or other aquatic life. Do not use within 3m of human or animal habitation. Animals protected under the Wildlife and Countryside Act such as, badgers, polecats, reptiles, natterjack toads and most birds are susceptible to gassing. Applications also pose a risk to livestock. Brodifacoum (CA, I)[R, M] Extremely hazardous (World Health Organisation (WHO) Ia). Ready to use bait, professional use only, inhibits vitamin K-dependent steps in the synthesis of clotting factors. Must be used in situations where baits are placed within a building or other enclosed structure, and target is living or feeding predominantly within that building or structure. Children, birds and other non-target wildlife are at risk from exposure to baits either directly or by secondary poisoning. Scavengers and predators are at risk of secondary poisoning from dead rodent bodies and bait containers that have not been collected or have been disposed of in refuse bins or rubbish tips. Poses a risk of contaminating food, feed and water. Bromadiolone (CA)[R, M] Extremely hazardous (WHO Ia) anticoagulant. Children, birds and animals, particularly cats, dogs, pigs and poultry, are at serious risk of poisoning. Scavengers and predators are at risk of secondary poisoning from dead rodent bodies that have not been collected or have been disposed of in refuse bins or rubbish tips. |
Calciferol/difenacoum [M] Mixture of rodenticides with different modes of action for mouse control. Difenacoum is extremely hazardous (WHO
Ia). Children and animals are at risk of poisoning if access to bait not prevented.
Chlorophacinone (IA)[R, M] Extremely hazardous (WHO Ia), harmful if in contact with skin and if swallowed, professional use only. Choice of product should take resistance into account. Prevent access to baits by children, domestic animals & birds. Harmful to game, wild birds & other wildlife. Cholecalciferol/Difenacoum See calciferol/difenacoum. Coumatetralyl (CA)[R] Highly hazardous (WHO Ib), inhibits blood coagulation. Children, birds and non-target animals, particularly dogs, cats, pigs are at risk of poisoning from bait and tracking powder. Risk of contaminating food, feed and water. Scavengers and predators are at risk of secondary poisoning from dead rodent bodies that have not been collected or have been disposed of in refuse bins or rubbish tips. Difenacoum (CA)[R, M] Extremely hazardous (WHO Ia) second generation indirect anticoagulant. Warfarin (CA)[R, M] Highly hazardous (WHO Ib), for use only by local authorities, professional operators providing a pest control service and persons occupying industrial, agricultural or horticultural premises. Evidence of resistance in rat populations. Children, birds and non-target animals, particularly dogs, cats, pigs, are at risk of poisoning. Scavengers and predators are at risk of secondary poisoning from dead rodent bodies that have not been collected or have been disposed of in refuse bins or rubbish tips. Subject to Grey Squirrels Order 1973(3) Use to kill grey squirrels for the purpose of tree protection is restricted or prohibited in parts of England, Scotland and Wales; it is prohibited in Northern Ireland*. CA=coumarin anticoagulant, IA=indandione anticoagulant, I=indoor use only, NC=narcotic
glucofuranose, P=phosphine generating compound. [R=Rats, M=Mice, B=Birds]. |
References
1. R Whitehead (Editor), The UK Pesticide Guide (2001), CABI Publishing, Wallingford, Oxon, 2001.
2. CDS Tomlin (Editor), The Pesticide Manual, (12th Edition), British Crop Protection Council, Farnham, Surrey, 2000.
3. Pine Marten Fact Sheet, The Mammal Society, http://www.abdn.ac.uk/mammal/pine.htm
4. World Non-agricultural Pesticide Markets, DS191, Agrow Reports, March 2000, PJB Publications, p87.
5. Rodenticide use by Local Authorities in Great Britain 1997 (Pesticide Usage Survey Group Report 155), Central Science Laboratory.
6. Pesticide Poisoning of Animals 1999, A Report of the Environmental Panel of the Advisory Committee on Pesticides, 2000, p17.
7. 10th Anniversary is record year for English kites, English Nature press release, Sept 1999, www.english-nature.org.uk
8. Pocket-sized pest controllers, Pest Control News, No. 54, September 2000, pp24-25.
9. National Rodent Survey Report 2000, Pest Control News, No. 55, December 2000, pp6-7.
10. Barrie Sheard, National Pest Technicians Association, Nottingham, personal communication.
11. National Rodent Survey Report, National Pest Technicians Association, Nottingham, p8.
12. D Martindale, The Rat Catcher, New Scientist, Vol 169, No. 2275, pp42-43.
[This article first appeared in
Pesticides News No. 52, June 2001, updated August 2001, page 18]