Rodenticides
Authors: Semino Giovanna 
Published: September 2023

Rodenticides are chemicals used for the control of mammal pests, particularly commensal rats and mice but also a variety of field rodents. There are many differentactive ingredients (AIs) used as rodenticides and they vary widely in the hazard they present. They are mainly used in baits and to limited extent applied as fumigant. Rodenticides used in baits are broadly classified into two categories: anticoagulants and nonanticoagulant acute poisons. Rodent pest control worldwide relies largely on the use of anti‐vitamin K (AVK) anticoagulants. They interfere with the activation of vitamin K, a critical component in the production of blood clotting factors in the liver. The anticoagulants are themselves separated into first‐generation (much more toxic when feeding occurs on several successive days rather than on 1 day only) and second‐generation chemicals (which can kill after a single night feeding and tend to remain in animal tissues longer than do first‐generation ones).

Nonanticoagulant rodenticides act through various mechanism of action. Bromethalin poisons the central nervous system (CNS) and ultimately causes respiratory distress following ingestion of a single dose. Cholecalciferol, the biologically active form of vitamin D, induces hypercalcemia (elevated blood calcium levels), which ultimately results in heart problems and kidney failure. Zinc phosphide liberates toxic phosphine gas upon interaction with stomach acid, leading to rodent mortality within few hours from ingestion. Except for Alphachloralose for mice control, the other rodenticides, formally referred to as the acute toxicants (e.g., arsenic, red squill, and phosphorus) are either no longer registered or of little importance in commensal rodent control.

Products containing substances applied by fumigation (like carbon dioxide, hydrogen cyanide, and aluminum phosphide) are strictly reserved for rodent control professionals. As rodenticides are generally nonselective animal poisons, they carry a few serious risks to other vertebrate species and are frequently the cause of unintended consequences, from the stench of rodents decomposing in the walls to poisonings of nontarget organisms. Primary poisoning can result from wild birds and pets, while secondary poisoning of birds and mammals (including dogs and cats) can accompany the ingestion of poisoned rodents. Human incident data sources report numerous incidents, especially involving children less than 6 years old, so that human exposure to rodenticides may result in severe outcomes and/or medical care. Therefore in the last two decades,risk mitigation measures(RMM) andintegrated pest management(IPM) strategies have been adopted worldwide. These measures require rodenticide products used in homes and marketed to general residential consumers to be sold only with bait stations that contain and/or are packaged with a rodenticide bait that is in block or paste form and accredited training programs are carried out for professional use rodenticides. Moreover, regulatory authorities conduct periodical re‐evaluations of registered rodenticides to ensure they meet modern health and safety standards to remain in the market.