Epidemiological evidence quartz, silicosis and lung cancer (II): Chinese cohort study, re-analysis

Status:

completed 12/2005

Aims:

Questions remain open regarding the relationship between quartz dust exposure, silicosis and lung cancer. In Part I of the project (Project No. 0061, "Epidemiological evidence quartz, silica and lung cancer (I)"), the results of epidemiological studies were analysed and published in a comprehensive and systematic survey (Exposure to quartz at the workplace, BGIA-Report 8/2006e). Part II aims to quantify the risk of lung cancer mortality resulting from work-related exposure to respirable quartz dust. An extended re-analysis of a Chinese cohort study and a more exact estimation of the exposure on the basis of better measurement data are to enable the lung cancer risk to be quantified more precisely.

Activities/Methods:

In conjunction with the "Tongji Medical College" in Wuhan, China, the BG Institute for Occupational Safety and Health (BGIA) has carried out a nested case-control study on the subject. The purpose of the study was to quantify the risk of lung-cancer mortality arising from work-related exposure to respirable quartz dust. Particular consideration was given to the confounders polycyclic aromatic hydrocarbons (PAH), diesel engine emissions, asbestos and smoking. This is the first time anywhere in the world that it has been possible to analyse an epidemiological assessment on this scale. The results of the study provide important information relevant both to quartz-related occupational diseases, and to the definition of limit values for exposure to respirable quartz dust. Estimation of the exposures in this study enables a dose-response relationship between respirable quartz dust and lung cancer to be identified and a limit value for respirable quartz dust to be specified.

Results:

The study results indicate that the observed excess risk of lung cancer among silica exposed workers in China is probably due to exposure to other occupational hazards (such as arsenic and PAHs) rather than due to exposure to respirable silica. In future this result ought to be taken into consideration when classifying quartz.

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