does not occur naturally. It is used as a rodenticide in urban and farm
rodent control and acts by disrupting the normal blood clotting mechanisms
causing an increased tendency to bleed. The rodenticidal properties of bromadiolone
were reported in 1976. It is a second generation anticoagulant that is effective
against rats and mice, including those resistant to first generation anticoagulants.
It is used in the form of ready-to-use baits of low concentration containing
0.005% bromadiolone. Bromadiolone is a white to off-white powder. Its solubility
in water is very low (less than 20 mg/litre at 20°C). It is slightly soluble
in ethanol and ethyl acetate, and soluble in dimethylformamide. The flash-point
temperature is 218°C.
Bromadiolone is absorbed through the gastrointestinal tract,
skin, and respiratory system. The major route of elimination in different
species after oral administration is via the faeces. The liver is the main
organ of accumulation and storage. Bromadiolone has been found in the liver
as the unchanged parent compound. Elimination from the liver is biphasic
with an initial rapid phase of 2-8 days and a slower phase with a half-life
of 170 days. No data are available on the kinetics and metabolism of bromadiolone
Chemical Name: 3-[3-(4′-bromobiphenyl-4-yl)-3-hydroxy-1-phenylpropyl]-4-hydroxycoumarin
Chemical Formula: C30H23BrO4
Bromadiolone has a high, acute
oral toxicity (LD50 of 1-3 mg/kg) for various species including
rodents and non-rodents. The dermal toxicity is also high (LD50
of 9.4 mg/kg in rabbits). Signs of poisoning are those associated with an
increased tendency to bleed. Bromadiolone is non-irritant to the skin. It
is a slight irritant for the eye. In feeding studies on rats, the only effect
found has been that associated with anticoagulant action. In a 12-week feeding
study on rats, the maximum tolerated dose was 10 µg/kg body weight per day.
Mutagenicity and teratogenicity studies have not shown any mutagenic, embryotoxic,
or teratogenic effects.
Effects on Other Organisms
in the Laboratory and Field: Bromadiolone has shown toxicity
for aquatic organisms. The LC50 (96-h) for various fish species
ranged from 1.4 to more than 3 mg/litre. Bird species appear to be less
susceptible to bromadiolone than mammals with a reported acute, oral LD50
of at 138 mg/kg. Secondary poisoning through the consumption of rats and
mice killed with bromadiolone may occur in dogs and cats in urban situations,
but more likely in farm situations. As a technical material, bromadiolone
is extremely toxic for many mammalian species. Signs of poisoning in all
species, including humans, are associated with an increased tendency to
Evaluation of effects
on the environment: Bromadiolone
is applied to discrete sites in the form of low-concentration baits and
is stable under normal conditions. Bromadiolone is poorly soluble in water
and, in a bait formulation, it is is unlikely to be a source of water pollution.
As a technical material, it is toxic for aquatic organisms.
Bromadiolone is readily adsorbed on soil, rich
in clay and organic compounds, with no leaching; degradation in soil is
significant. Non-target organisms are potentially at risk from direct consumption
of baits (primary hazard) and through eating poisoned rodents (secondary
hazard). Whole-grain baits are highly attractive to birds. Bird species
appear to be less susceptible to bromadiolone than rodents.
The primary hazard is usually expressed by
the amount of finished bait that must be consumed to approach the lethal
dose. To reach the toxic or lethal dose, the non-target species must consume
comparatively large amounts of bait with a concentration of 0.005% active
ingredient. Some secondary toxicity laboratory studies on wildlife have
shown that captive predators could be intoxicated by no-choice feeding of
bromadiolone-poisoned or dosed prey. The significance of these results in
terms of hazards under field conditions is difficult to assess, because
the predators would not be expected to eat only poisoned animals. However,
predators may take poisoned small mammals that are still alive, preferentially.
In areas close to baiting, poisoned rodents may represent a high proportion
of the diet for individual birds. However, only few individuals will
be affected, unless there is very widespread and constant use of the baits.
Therefore, some kills of owls can be expected, but there will be no severe
population effects. This ties in with small numbers of poisoned owls observed
in the field.
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