Appraisal of medical and exposure data to estimate the occupational carcinogenic risk in coal mines : a pilot study

Abstract

Background: The coal mining environment presents the occupational hygienist with numerous challenges which need to be overcome on a daily basis. Workers employed in either underground or opencast coal mines run the risk of being exposed to countless hazards. Accidents, explosions, poor underground ventilation, and the development of respiratory diseases are a few of the risks and hazards workers can be exposed to. Exposure to occupational carcinogens adds to the list of hazards present in a coal mine, and exposure can occur through inhalation, ingestion or even skin contact. Aims and objectives: The study aimed to provide an improved understanding of the various occupational carcinogens, as well as the carcinogenic risk present in the South African coal mining environment through the appraisal of historical medical and exposure monitoring data. This study also aimed to establish if a relationship exists between occupational exposure to carcinogens and the development of cancer among coal mine workers. Cancer incidence, in this study, refers to the proportion of coal mine workers who developed cancer during a particular time period (i.e. 2009-2015) and not to the number of new cancer cases occurring in the coal mine worker population during a specific time period (CDC, 2012). Methods: Published literature was evaluated to identify occupational carcinogens present in a coal mine, as well as the cancer types linked to the occupational exposure to these carcinogens. Historical medical data was assessed to determine the cancer types and the frequency at which they occurred among the coal miners from ten coal mines. Historical exposure monitoring data and risk assessments were used to determine the highest exposed groups in specifically an underground coal mining environment due to the higher risk involved when compared to an opencast coal mine. Lastly, the relationship between the diagnosed cancer incidences and the exposure of coal mine workers to the identified occupational carcinogens were established. Effect size, including odds ratios (OR) and relative risk (RR), were used to describe the relationships between the various factors involved in occupational carcinogen exposure as well as the development of cancer. Ethical approval from the Health Research Ethics Committee (HREC) of the North-West University was obtained (NWU-00069-16-A1). Results: Various occupational carcinogen exposures, such as respirable dust (coal mine dust and crystalline silica dust) liberated during day-to-day coal mining processes, were identified and retrieved from the results. The historical medical data showed the diagnosis of various cancer types in numerous occupations in the ten coal mines. Prostate cancer had the highest incidence rate (40.7%) of the 32 total cancer incidences and respiratory cancers had the second highest incidence rate (37.5%). The multi-task worker, mostly responsible for production activities, had the highest exposure to occupational carcinogens of all the occupations, as well as the highest cancer incidence rate (25%) of the 32 total cancer incidences. The risk of developing cancer was similar at all mine types with ratios indicated as 1.02 in 1 000 workers (underground (UG)), 1.25 in 1 000 workers (opencast (OC)), and 1.24 in 1 000 workers (combination mine (OC + UG). Conclusions: Historical data confirmed the presence of various occupational carcinogens (coal mine dust and silica dust) in a coal mining environment, as well as the risk of developing occupational cancer among coal mine workers. The occupations presenting the highest risk to workers for the development of cancer, as well as the exposure to occupational carcinogens were the multi-task worker and the maintenance occupations.