Evaluation and Control of Employee Exposure to Diesel Exhaust Emissions in Underground Coal Mines

BHP Steel Collieries conducted research into employee exposure to diesel exhaust emissions at Tower Colliery, Douglas Park, NSW Australia between 1990 1993 (Pratt 1993). As a result of that preliminary research, the current research project was developed to evaluate four possible control measures evaluated for effectiveness, suitability and practicality over a period of twelve months. In addition to this project, exposure data was collected at eight other New South Wales (NSW) underground coal mines to determine if the extensive database developed at Tower Colliery was indicative of employee exposure throughout the industry.

Sampling techniques developed by the University of Minnesota and the US Bureau of Mines were used to collect personal samples for diesel aerosol particulate with confirmatory Scanning Electron Microscopy techniques. All sampling for the four control technologies evaluated (ie chemical decoking of engines, scrubber tank and intake air filter maintenance, disposable exhaust filters and ventilation) was conducted in a special section of mine roadway where conditions such as ventilation and work rate could be controlled yet activities were still representative of underground operations. Sampling at the other underground coal mines took place over a six month period and covered all mining districts within the State, including large and small operations.

As a result of extensive testing it can be concluded that:

• Chemical decoking of engines does reduce employee exposure to diesel aerosol particulates.
  
• Cleanliness of water filled scrubber tanks does not in general relate to their efficiency in reducing diesel aerosol particulates.
  
• Cleanliness of air intake filters does not affect diesel aerosol particulate emissions unless they are completely blocked.
  
• Disposable exhaust filter systems are highly effective in reducing diesel aerosol particulate emissions.
  
• Reasonable relationships between diesel aerosol particulates and increasing airflow exist for two vehicles currently used in NSW coal mines, however the existence of a uniform relationship to cover all vehicles is unclear.
  
• The use of multiple vehicles in the one heading can have a significant affect on the ventilation pattern in that heading.
  
• Sampling at eight NSW underground coal mines confirmed the extensive employee exposure database previously collected at Tower Colliery. In all cases the highest levels were experienced during long wall change outs.