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| NIOSH research showed area sampling was not indicative of worker dust exposures |
Description of Problem
In the mid-1980s, the Mine Safety and Health Administration (MSHA) initiated the development of a new kind of sampling instrument for measuring dust levels in coal mines - a machine-mounted respirable dust monitor (MMRDM). However, the MMRDM was more than a new sampling instrument. It also changed the location where samples are collected. The usual method of sampling for coal mine dust uses "personal sampling," i.e., equipment worn by the workers. The MMRDM, housed in a 160-pound box, had to be mounted in a fixed location. The general location being considered was on the mining equipment, such as fixed locations on continuous mining machines or on longwall shearers or longwall shields. Thus, it could only be used for sampling in a particular area. However, area sampling equipment does offer the benefits of providing more functionality and being less subject to possible tampering.
Developing the MMRDM was very controversial within the coal industry. The industry believed that it was likely to measure higher dust concentrations than the personal sampler. There were also serious questions about its accuracy.
Research and Development Activities
During 1998-1999, NIOSH did a number of underground studies to assess the viability of the MMRDM. Clusters of current conventional personal dust samplers were placed at locations typical of where MMRDMs might be mounted on mining equipment. Their dust concentration readings were compared with those from identical samplers worn by miners in the working face area of the mine. Results showed that there was no consistent relationship between personal sampling equipment worn by workers and area samples taken by the MMRDM on the mining machine. These data proved that the MMRDM would be inadequate for compliance sampling of operator dust exposure and gave little meaningful information about the actual dust exposure of workers.
R&D Outputs and Transfer Activities
A NIOSH report on this study was written, and the findings were first presented at MSHA headquarters. The findings were then provided to both industry and labor at a number of meetings to discuss the overall issue of improved coal dust sampling in underground coal mines. The results were also presented at national and international conferences, and published in a peer-reviewed journal.
Description of Intermediate Outcome
These findings were instrumental in getting MSHA, in the fall of 2000, to drop its 15-year long initiative to develop an MMRDM. Then, through an industry-labor-NIOSH partnership, a decision was made to turn all of the MMRDM resources toward developing a person-wearable real-time continuous dust monitor. This has resulted in the evolution of the personal dust monitor (PDM) over the past 5 years, a device that is showing great promise.