Epidemiological evidence quartz, silicosis and lung cancer (III), "extended follow-up" of the Chinese quartz cohort through to 2003

Status:

completed 05/2011

Aims:

A meta-analysis of epidemiological study results was produced and published in Sub-project I (Project 0061, "Epidemiological evidence quartz, silicosis and lung cancer (I)" of the (then) BG Institute for Occupational Safety and Health (BGIA). The studies showed the risk of lung cancer to be elevated only among silicotic workers exposed to quartz dust. Smoking was a significant risk factor. In Sub-project II (Project 1074, "Epidemiological evidence quartz, silicosis and lung cancer (II): Chinese cohort study, re-analysis"), the lung-cancer risk presented by occupational exposure to respirable quartz dust was quantified by re-analysis of the Chinese cohort study. The results indicate that the elevated lung-cancer risk can be explained with a high degree of probability by other work-related hazardous substances (e.g. arsenic, radon, polycyclid aromatic hydrocarbons). In Part III of the project, the lifetime risk of silicosis was quantified in relation to respirable quartz dust exposure.

Activities/Methods:

The basic data of this cohort for the follow-up period of 1969-1994 were recorded within a joint project conducted by the National Cancer Institute (NCI), the National Institut for Occupational Safety and Health (NIOSH) and the Tongji Medical College, and financed by the NCI. The extended follow-up through to 2003 was conducted by the IFA in conjunction with the Tongji Medical College. The dose-response relationship between quartz and silicosis was determined again with reference to improved exposure data by validation of the exposure to respirable quartz dust and relevant lifestyle factors.

Results:

During this project, a change over time in the dose-response relationship between exposure to respirable quartz dust and the incidence of silicosis has been determined for the first time. The study shows that the effects of quartz are dependent not only upon the dose, but also upon various combinations of the long-term average and maximum exposures. An interpretation of the risk dimensions must give consideration to the fact that different countries use different dust measurement strategies which are not always comparable. The dose-response relationship exhibits an additional lifetime risk of silicosis of one additional case per 1,000 exposed individuals at a maximum exposure to respirable quartz dust up to 0.1 mg/m³ (both long-time average and short-time exposure in accordance with the German measurement strategy).

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