Am. J. Respir. Crit. Care Med., Vol 157, No. 1, Jan 1998, 69-75.
Environmental exposure to crocidolite and mesothelioma: exposure- response relationships [In Process Citation]
J Hansen, NH de Klerk, AW Musk and MS Hobbs
Department of Respiratory Medicine, Sir Charles Gairdner Hospital, University of Western Australia. janiceh@ichr.uwa.edu.au
This study aimed to estimate exposure-response relationships for
mesothelioma and environmental exposure to crocidolite. All 4,659 former
residents of Wittenoom, Western Australia (WA) who lived there between 1943
and 1993 for at least 1 mo and were not directly employed in the
crocidolite industry, were followed-up through the WA death, cancer and
mesothelioma registries, electoral rolls, and telephone books. In 1992, all
subjects who should be traced were sent a questionnaire. Exposure levels
were estimated from results of periodic environmental surveys and duration
of residence. Incidence rates were standardized to the World Population and
Cox Regression was used to estimate the effects of exposure on incidence.
To the end of 1993, 27 cases of mesothelioma were diagnosed. Mesothelioma
cases stayed longer at Wittenoom, had a higher average intensity of
exposure, and a higher cumulative exposure to crocidolite than control
subjects. The standardized incidence of mesothelioma was 260 per million
person- years, and was similar for males and females. The rate increased
significantly with time from first exposure, duration of exposure and
cumulative exposure. At these levels of crocidolite exposure, there is a
significantly increased risk of mesothelioma, which is dose-dependent.
