Slaked lime and betel nut cancer in Papua New Guinea.

Oral squamous cell cancer is the most common malignant tumour in Papua New Guinea. We have found that oral cancer in this region is concentrated at the corner of the mouth and cheek, by striking contrast with western populations, and corresponds precisely with the site of application of lime in 77% of 169 cases. Powdered slaked lime applied to the chewed Areca nut with Piper betle inflorescence at the corner of the mouth causes the mean pH to rise to 10, at which reactive oxygen species are generated from betel quid ingredients in vitro. Reactive oxygen species, together with sustained lime-induced cell proliferation, suggest a possible mechanism of carcinogenesis for this tumour.