Brodifacoum

The formulas of some ARs are given in Figure 11.1, where it can be seen that they have some structural resemblance to both dicoumarol and vitamin K in its quinone form. All possess quinone rings linked to unsubstituted phenyl rings. The phenyl rings of the rodenticides confer hydrophobicity, especially in the relatively large and complex molecules of brodifacoum and flocoumafen. The chemical properties of some ARs are given in Table 11.1... 

All the compounds listed in Table 11.1 are solids. Flocoumafen and brodifacoum have particularly low vapor pressures. The hydrophobicity of brodifacoum and flocoumafen is reflected in their low water solubility. It should be remembered,... 

A number of reports have established the presence of rodenticides in predators and scavengers found dead in the field (see, for example, reports of U.K. Wildlife Incident Investigation Scheme [WHS]). Brodifacoum, difenacoum, bromodiolone, and flo-coumafen have all been found, albeit at low levels in most cases (<1 ppm in liver). Sometimes, more than one type of rodenticide has been found in one individual. The toxicological significance of these residues will be discussed in Section 11.5. 

One study conducted in Britain between 1983 and 1989 was of barn owls found dead in the field 10% of the sample of 145 birds contained anticoagulant rodenticide residues in their livers, and difenacoum and brodifacoum were prominent among them (Newton et al. 1990). In another study, barn owls were fed rats that had been dosed with flocoumafen. It was found that a substantial proportion of the rodenticide ingested by owls was eliminated in pellets (Eadsforth et al. 1991). The authors suggest that exposure of owls to rodenticides in the field may be monitored by analysis of pellets dropped at roosts or regular perching places. 

Newton et al. (1990) fed mice containing brodifacoum to bam owls, and estimated that birds lethaUy poisoned by the rodenticide n = 4) had consumed 0.150-0.182 mg/kg of the compound. The birds died within 6-17 days of receiving a single dose... 

When ARs have been used to control rodents and vertebrate predators in conserved areas, there have been instances of both primary and secondary poisoning. In New Zealand, such incidents have been observed on islands where bait treated with brodifacoum has been used. Casualties have included native raptors, such as the Australasian harrier (Circus approximans) and morepork (Ninox novaeseelaniae), as well as other species, such as the pukeko. Western weka (Galliralus australis), and... 

Brodifacoum, difenacoum, flocoumafen, and other superwarfarins bind strongly to proteins of the hepatic endoplasmic reticulum and consequently have long half-lives in vertebrates, often exceeding 100 days. Thus, they present a hazard to predators and scavengers that feed on rodents which have been exposed to superwarfarins. A number of species of predatory and scavenging birds have died as a consequence... 

Eason, C.T. and Spurr, E.B. (1995). Review of toxicity and impacts of brodifacoum on non target wildlife in New Zealand New Zealand Journal of Zoology 22, 371-379. 

Hegdal, P.L. and Colvin, B.A. (1988). Potential hazard to Eastern Screech owls and other raptors of brodifacoum bait used for vole control in orchards. Environmental Toxicology and Chemistry 7, 245-260. 

Howald, G.R., Minean, R, Elhott, J.E., and Cheng, K.M. (1999). Brodifacoum poisoning of avian scavengers during rat control at a seabird colony. Ecotoxicology 8, 431 37. 

Brodifacoum [56073-10-0] is a substituted 4-hydroxywarfarin with a strikingly prolonged half-life in the human body (50,51). Although used as a rodenticide, it has been ingested by some humans and observed to persist from 50 days to eight months. Its use in humans may be prohibitive because of the excessively prolonged half-life in the body. 

SEE BRODIFACOUM. First reaction is with diphenyl of p-diphenyl bromide )... 

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