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22-05-2012 | General practice | Article

Cristobalite implicated in industry lung cancer


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MedWire News: The increased risk for lung cancer seen in silicon carbide industry workers is primarily due to cristobalite and silicon carbide fiber exposure, show study findings.

Previous research has shown that workers in the silicon carbide industry have an increased risk for lung cancer, but the contribution of individual particulate factors to this risk has not been assessed.

Merete Drevvatne Bugge (National Institute of Occupational Health, Norway) and colleagues therefore investigated the effect of cumulative exposure to total and respirable silicon dust, respirable quartz, cristobalite, and silicon carbide particles and fibers on lung cancer risk in 1687 workers in the Norwegian silicon carbide industry.

The workers had been employed in the industry for at least 3 years between 1913 and 2003 and incidence of lung cancer was assessed from 1953 to 2008.

Writing in Occupational & Environmental Medicine, Bugge and team report that the overall incidence of lung cancer was higher in the silicon carbide workers than the general male population (standardized incidence ratio [SIR]=1.6).

The highest overall risks were seen in those working in the furnace department (SIR=2.3) and in those working in more than one department (SIR=1.9).

Regarding exposure to specific particulate factors, the researchers found that workers in the highest versus the lowest exposure categories for each of the factors had a 1.9‑2.3-fold increased risk for lung cancer.

However, significant associations between exposure and lung cancer incidence were seen only for total silicon dust and cristobalite.

In a multivariate model, exposure to cristobalite showed the strongest associations with lung cancer followed by exposure to silicon carbide fibers.

"Control of the dust exposure in the silicon carbide industry, especially in the furnace hall, is essential," write the authors.

They say that knowledge about the men's exposure to other carcinogenic factors such as asbestos and their use of protective equipment was limited, which may have influenced the results.

But the results indicate that exposure to cristobalite and silicon carbide fibers seems to carry the highest risk for lung cancer of all the components of silicon dust produced by the silicon carbide industry.

By Helen Albert

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