All pesticides are designed to harm living things such as weeds, unwanted insects, fungal infections and rodents and most pesticides will also harm non-target organisms to some degree. Pesticides that have been found to be most harmful to human health, biodiversity and the environment have been designated as highly hazardous pesticides (HHPs). HHPs make up a relatively small proportion of all pesticides in use but they are disproportionately used in lower- and middle-income countries where the majority of harm from pesticides occurs. Taking action on HHPs has been shown to significantly reduce harm to people and the environment.