Rodenticides: Background & Hazards

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Rodenticides: Background & Hazards Rats and mice have been living with humans for centuries, and humans have been working for just as long to keep them at bay. Rodents such as gophers, moles, voles, and squirrels are also viewed as pests in some settings. Poisons have been used as rodent -control measures for many years. Before the 1940s, rodenticides contained heavy metals such as arsenic and thallium or poisons such as strychnine and red squill. Most of these chemicals are no longer used as rodenticides with the exception of strychnine, which is currently registered for use only below -ground as a bait application to control pocket gophers. For more details, see US EPA's RED Facts on Strychnine. In the 1940s and 1950s, the first kind of anticoagulant rodenticides known as first -generation rodenticides were developed. This class of rodenticides work by disrupting the normal blood clotting or coagulation process so that dosed individuals or animals suffer from uncontrolled bleeding or hemorrhaging. Anticoagulant rodenticides that are in wide use today are members of a more potent class of anticoagulants known as second -generation rodenticides. The following section provides a more detailed comparison between first and second generation rodenticides. Other rodenticides are non -anticoagulants and work in different ways. Non -anticoagulant rodenticides in use include bromethalin, cholecalciferol, and zinc phosphide. Using rodenticides for control is frequently the cause of unintended consequences, from the stench of rodents decomposing in the walls to poisonings of non -target organisms. Primary poisoning can result from wild birds, pets, or even children eating baited rodenticides, while secondary poisoning of birds and mammals (including dogs and cats) can accompany the ingestion of poisoned rodents. nticoagulant Rodenticides First -Generation Anticoagulants First -generation anticoagulant rodenticides listed in the table below require rodents to consume the bait for several consecutive feedings for delivery of a lethal dose. There are three US EPA - registered first -generation rodenticides, including warfarin (also used as an anti -clotting drug for coronary artery disease), chlorophacinone, and diphacinone. The first -generation compounds are excreted fairly rapidly by mammals, usually within a week. However, the use of any rodenticides pose a poisoning risk to children, pets and wildlife. First -Generation Rodenticides Chlorophacinone Diphacinone Anticoagulant, multiple dose treatment Acute Oral Toxicity Primary Poisoning Risk High Low (birds and mammals) Anticoagulant, High Low (birds and mammals) multiple dose treatment Secondary Poisoning Risk L,ow (birds), High (mammals) Moderate (birds), l-ligh (mammals)