How Lung Cancer Exposures to Crystalline Silica and Radon

The underground coal mining industry plays an important role in contributing energy supplies, increased prevalence and severity of the chronic lung diseases raised concerns of occupational health. Silica and radon exposure in coal mining industry has been extensively documented1“4. A substantial body of evidence has identified crystalline silica dust and radon gas as major causes of lung cancer5“8. However, the inconsistent and controversial results from epidemiological studies9“11 made the evidence of silica and radon associated with lung cancer being less convincing. It can possibly be explained by the fact that non-occupational exposures such as cigarette smoking was not investigated sufficiently in many studies, and cigarette smoking ranks number one cause lung cancer (https://www.cdc.gov/cancer/lung/basic_info/). Therefore, with potentially substantial exposures to multiple carcinogens including crystalline silica dust, radon, and cigarette smoke, the further study of the risks of lung cancer and systematically measurements in the coal mining industry are needed.

Our long-term goal is to improve our understanding of exposures to, and lung cancer risks associated with, exposures to crystalline silica, radon, and cigarette smoke in the underground coal mining industry. The objectives in this proposal are: 1) improve understanding of coal miners exposures to crystalline silica, radon in the underground coal mining facilities in Webster County, Kentucky; 2) investigate the association between lung cancer and miner's exposures to silica, radon and cigarette smoke. These two objectives will allow us to fill the gap of current studies. We hypothesize that the concentrations of silica and radon will be significant high in the underground coal mining workplace. We hypothesize that crystalline silica, radon, and non-occupational cigarette smoke increase the joint risk of lung cancer.

The rationale of this proposed study is that lung cancer is the most common cancer worldwide, and it is the leading cause of mortality in the United States per year (https://www.cdc.gov/cancer/lung/statistics/). It is crucial to determine if miner's exposure is associated with increased lung cancer risk so that appropriate protective measurement may be taken. The proposed study objectives are also included in the National Occupational Research Agenda (https://www.cdc.gov/niosh/nora/crosssectors/crc/researchagenda.html).

Specific Aim1. Determine worker's exposures to silica dust and radon in the underground coal mining industry. To better understand the underground coal mining environment and worker's exposures to crystalline silica dust and radon, we will systemically monitor three large underground coal mining facilities in Webster County, Kentucky. The real-time measurements will be conducted to determine the size, concentration, and chemical compositions. Air samples will also be collected for quantification of crystalline silica by using laboratory analysis.

Specific Aim2. Determine association between lung cancer and exposures to crystalline silica, radon, considering cigarette smoking. A case-control study will be conducted to evaluate individual and joint risk of lung cancer associated with miner's exposures including crystalline silica, radon, and non-occupational cigarette smoke. We will recruit 600 lung cancer cases and 600 matched controls. Personal sampling will be conducted to monitor individual exposures to silica, radon. The statistics will be applied to determine the association between lung cancer and miner's exposures.

Anticipated Project Outcomes: This proposal will results in: 1) Defined size distribution, concentration, and chemical compositions of air samples in the underground coal mining facilities, characterization of crystalline silica dust and radon. 2) Identification of association between lung cancer and silica, radon, and cigarette smoke exposures.

Through these two fundamental aims, we will we will improve our understanding of worker exposure to crystalline silica, radon and cigarette smoke. This will allow federal agencies to develop surveillance system and restrain policies to prevent worker's health from developing lung cancer. Based on the study results, we will be able to evaluate industry health and safety mitigations to ensure that coal mining industry efforts to reduce hazards are effective.

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