Invasive rodent eradication on islands: assessment and mitigation of human exposure to rodenticides

Use of rodenticides is a common method for eradication of invasive rodents from islands, with eradication projects increasingly being undertaken on inhabited islands or islands used by people for harvesting food. The expansion of eradication projects to inhabited islands will require that all real and perceived human health risks from the projects are socially acceptable, or effectively mitigated. When broad-scale use of rodenticide for eradication is proposed on inhabited islands, it is usual for concerns to be raised about the risks of rodenticide exposure to people, livestock, pets, game animals, and marine food sources. Although risks to humans have been assessed prior to some individual island eradications, there are currently no established frameworks for consistent and formal approaches to such assessments. To inform the focus of future assessments, we synthesized current understanding of the potential pathways of human exposure to rodenticides and risk mitigation measures associated with island rodent eradication projects. We sought to develop this through a literature and database review that identified 153 inhabited islands where rodent eradication projects had been undertaken, of which 95 documented a priori assessments of human risks and mitigation measures. We found no reports of adverse effects from human exposure resulting from any source during discrete rodent eradication programs on inhabited islands, including direct rodenticide bait consumption, inhalation, dermal absorption, secondary or tertiary exposure. To continue advancing eradications on inhabited islands of increasing scale and proactively manage risks and perceptions, we recommend engagement processes that integrate island communities into a priori risk assessments and mitigation measure selection.