Air carrier Captain reported refusing an aircraft that had an expired Residual Disinsection Certificate. If operated; the aircraft would require fumigation procedures using permethrin (PER) at an international destination with crew and passengers aboard. Captain also reported the use of PER is not allowed in the United States as evidence suggests use may have a variety of toxic effects.

Narrative

During preflight briefing preparation; I was adjacent to another crew (including an LCP (Line Check Pilot) that was conducting a line check) that their aircraft had an expired Residual Disinsection Certificate" and that upon arrival in AKL the aircraft -- with passengers and crew still boarded -- would be subject to disinsection (fumigation) procedures by local authorities. As the crew began to investigate these procedures; and the methods and chemicals involved in these procedures; all involved became concerned for the safety of the passengers and crew. Indeed; a cursory internet search on the toxicity effects of the primary chemical used -- Permethrin -- reveals that there is an increasing body of evidence that indicates this process is not suitable nor safe for exposure to passengers or crew members. Indeed; when inquiries were made as to why this aircraft hadn't been treated; it was revealed that the use of Permethrin in this application is NOT ALLOWED in the U.S.; and that these treatments are in use in Brazil! Upon learning this; the captain notified the Chief Pilot that the aircraft was being refused.Soon after; a company representative approached myself as to whether I would be willing to operate my segment with that aircraft. I advised that person I would not accept a dispatch with that aircraft. Not long after; another Captain (flying elsewhere) was contacted with the same proposal; who also refused. At that time; each flight was operated with different aircraft with current Residual Disinsection Certificates.To be noted; here is an excerpt from one of many on-line resources that highlights the threats posed by this process: "Permethrin (PER); the most frequently used synthetic Type I pyrethroid insecticide; is widely used in the world because of its high activity as an insecticide and its low mammalian toxicity. It was originally believed that PER exhibited low toxicity on untargeted animals. However; as its use became more extensive worldwide; increasing evidence suggested that PER might have a variety of toxic effects on animals and humans alike; such as neurotoxicity; immunotoxicity; cardiotoxicity; hepatotoxicity; reproductive; genotoxic; and haematotoxic effects; digestive system toxicity; and cytotoxicity. A growing number of studies indicate that oxidative stress played critical roles in the various toxicities associated with PER. To date; almost no review has addressed the toxicity of PER correlated with oxidative stress.""