Chinese miners at increased risk of cancer

Abstract

A study led by researchers in China has confi rmed the association between inhalation of silica dust and a height ened risk of lung cancer. The study observed 74 040 people working at metal mines and pottery factories in the country. Average follow-up was 33 years. Mortality from all causes was higher in workers exposed to silica dust (993 vs 551 per 100 000 person-years in nonexposed workers). “We saw elevated mortality from lung cancer among exposed workers compared to nonexposed workers”, Weihong Chen (Huazhong University of Science and Technology, Hubei Province, China), co-author of the study, told The Lancet Oncology. He added that the association held true even after adjustment for cigarette smoking (many people in the cohort were smokers). Depending on level of exposure to silica dust, the risk ratio ranged from 1·45 to 1·53. “It is a huge study—this kind of data is not available anywhere else”, noted Qingyi Wei (MD Anderson Cancer Centre, University of Texas, TX, USA). “It provides the basis of experimental studies in the future [into] how silica may cause lung cancer”. Classifi ed by the International Agency for Research on Cancer as a group 1 carcinogen, silica dust is thrown up whenever one drills into rock. It is associated with various diseases— silicosis, cardiovascular disease, and tuberculosis, for example. People who work in construction, mining, pottery, and stone crushing are vulnerable. In China, this group includes more than 23 million workers. Occupational health expert Perry Gottesfeld (Occupational Knowledge International, CA, USA) believes that respirable silica is the developing world’s largest work-related health problem. The USA currently mandates a limit roughly similar to that of China’s, but the US Occupational Safety and Health Administration has proposed for this to be further reduced. “It is a very out-of-date standard, which everyone agrees is not protective for lung cancer”, said Gottesfeld. Moreover, Chinese safety standard enforcement is poor. Aside from strengthening such capacity, there are simple measures that have a proven ability to alleviate the problem, such as proper ventilation for underground mines and respirators for dust-exposed workers. But perhaps foremost is the use of equipment that sprays a fi ne mist of water. Gottesfeld co-authored a study showing that this approach can cut respirable silica by up to 82%. “These exposures can be reduced considerably at little cost; we’ve been able to demonstrate this in India, and it should all be doable in China”, he concluded.