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Surprising Science

Canada To Restrict Certain Rodent Poisons; US May Follow

Residue of second-generation blood thinner-type poisons are increasingly being found in the livers of dead birds and other predator animals.

What’s the Latest Development?

In response to studies showing that current varieties of anticoagulant rodenticides (ARs) build up in, and eventually kill, birds and other animals that feed on rodents, Canada will restrict outdoor household use of ARs to less-toxic versions starting January 1. In the US, the Environmental Protection Agency is looking at banning second-generation ARs from the consumer market and increasing the use of bromethalin, a neurotoxin.

What’s the Big Idea?

The human blood thinner warfarin was originally developed as a rodenticide, but as a first-generation AR still in use today, it is considered less toxic because it doesn’t accumulate in the bodies of predator animals. Second-generation ARs, on the other hand, were present in almost all of the dead owls and most of the dead hawks studied in and around Vancouver. Most users of these ARs are pest control professionals, who leave their products outside in permanent bait stations. One expert suggests that these be banned instead, that operators should use ARs only when necessary, and that customers should be warned of their environmental effects.

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