Suspected nasopharyngeal carcinoma in three workers with long term exposure to sulphuric acid vapour

Sulphuric acid vapour has been suspected of being an industrial carcinogen. In this study a cluster is presented of three patients with nasopharyngeal carcinoma (NPC) who worked in the same building of a telecommunications co nveyance station in southern Taiwan with long term exposure to sulphuric ac id vapour concentrations as high as 0.18 mg/m(3). All three workers were di agnosed with NPC within a 5 month period between September 1992, and March 1993. Compared with 19 other healthy workers from the same building, these three workers with NPC had worked significantly longer in this building tha n had the others (mean (SD) (years): 12.7 (0.6) v 7.4 (4.4); p=0.01). With an in situ nucleic acid hybridisation and immunostaining method for colocal ised Epstein-Barr virus (EBV) and secretory component (SC) protein among bi opsy specimens of these three patiente with NPCs, it was found that some tu mour cells did not contain EBV and SC protein staining signals. These resul ts indicate that EBV infection is not the only risk factor for NPC and long term exposure to relatively low concentrations of sulphuric acid vapour ma y be associated with the development of NPC.