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| Certification of PDM accuracy in the PRL Laboratory Marple Dust Chamber |
Description of Problem
In 1996, the Secretary of Labor asked NIOSH to develop a better dust monitoring instrument for coal mining. At that time, the coal mine "personal sampler" had been in use for 30 years. It is a rugged and reasonably accurate instrument. However, because the inside filter must be weighed in a lab, there was always a delay of a week or more in getting results back to the mine operator. The miners themselves seldom had any knowledge of their dust exposure. This delay meant that miners could be exposed to excessive dust levels without having the chance to immediately correct the problem and avoid overexposures for the entire shift.
Research and Development Activities
Initial work to develop a better dust monitoring instrument focused on a machine-mounted area-sampling monitor. However, NIOSH found that this area-sampling instrument was inadequate for compliance sampling of operator dust exposure. NIOSH findings showed that there was no consistent relationship between personal sampling equipment worn by workers and area samples. (See the Intermediate Outcome entitled "NIOSH Establishes the Ineffectiveness of Area Dust Sampling as a Measure of Worker Exposure.")
The work was then redirected to develop a monitor that was small and light enough to be worn by the workers (called a personal dust monitor, or PDM), but which kept most of the functionality features of the area monitor. One of the most important of these features was the ability to read out the gravimetric dust level during the work shift and to predict the full-shift dust level if nothing changed in the mining situation. This allowed workers and mine management to immediately correct engineering dust controls to remedy high dust levels, thereby avoiding overexposure of the workers. At the end of the shift, the PDM data are downloaded into a computer and stored for future reference. The concept was to empower miners and mine management to do something about possible dust overexposures in real time. The dust monitor was built into a miner's cap lamp unit so that miners are putting on their dust monitors when they put on their cap lamps. This makes the PDM more user-friendly for the miners.
R&D Outputs and Transfer Activities
The PDM has undergone a great deal of technology transfer. It has been discussed in numerous papers, presentations, and workshops, both national and international. It has been demonstrated at recent Mine Safety and Health Administration (MSHA) dust hearings. Mockups have been provided for industry and United Mine Workers of America meetings. International PDM partnerships have been established with Australia and the Republic of South Africa. The PDM was recently given an R&D100 award as one of the nation's top 100 technical developments of the year. A PDM Coal Partnership has been established with members from industry, labor, and NIOSH to promote the PDM and to exchange information on the technology.
Description of Intermediate Outcome
In March 2003, MSHA proposed new rules on how coal dust is to be measured. These proposed rules incorporated the new PDM instrument under development by NIOSH (Federal Register, Vol. 68, No. 4, pages 10805, 10807, 10809, 10826, 10827, 10874, 10875, and 10879). However, in 2003, the instrument had not been fully tested. Because of this and for other reasons, MSHA announced a postponement of the proposed dust rule (Federal Register, Vol. 68, No. 128, July 3, 2003, Proposed Rules, pages 39881-39882). Since then, additional underground testing of the latest version of the PDM has been ongoing. Findings have been highly encouraging.
The PDM is now available as a commercial product (http://www.rpco.com). Orders from mines to purchase the device have been received by the manufacturer.