Research in China provides further evidence that exposure to silica dust raises the risk of cancer of the esophagus, the organ that connects the mouth with the stomach.

The association was first noted in 1968, when a high rate of esophagus cancer was observed among residents of a South African village, which seemed to result, in part, from silica contamination of their diet. Since then, numerous other reports have verified this association.

In the present study, Dr. Ignatius Tak Sun Yu, of The Chinese University of Hong Kong, and colleagues evaluated death from esophagus cancer among nearly 3000 caisson workers and non-caisson workers exposed to silica.

Caisson workers were defined as subjects who worked underground in settings with high levels of silica dust.

The researchers’ findings appear in the International Journal of Cancer.

Compared with the general population, the workers were 2.2-times more likely to die from esophageal cancer. The elevated risk was 4.21-fold for the caisson subset of workers.

After accounting for Smoking and alcohol drinking, non-caisson workers were no longer at increased risk for death from esophagus cancer. By contrast, caisson workers continued to have a 2.34-fold elevated risk.

“We believe,” the researchers conclude, “that the excess risk of esophageal cancer (death) among caisson workers with silicosis could best be explained by the very heavy exposure to free silica dust in their working environment.”

SOURCE: International Journal of Cancer, April 10, 2005.