Snapshot of noise and worker exposures in sand and gravel operations

Previous studies and research efforts have shown that noise-induced hearing loss (NIHL) is a problem in the U.S. mining industry. In response, researchers at the National Institute for Occupational Safety and Health (NIOSH) have been conducting a cross-sectional survey of equip­ ment noise and worker noise exposures in the mining industry to estimate the potential for NIHL within the mining community. One commodity recently surveyed was the extraction of sand and gravel from surface pits and by dredging. To address the potential for NIHL in the sand and gravel industry, sound levels on and around the dredges and processing equipment were recorded to iden­ tify areas of high noise levels. Full-shift worker dosimetry, in conjunction with task observations, was documented to determine the relationship between exposure and source. This paper presents research examining noise on dredges used in several surface mine sand and gravel operations and in the processing facilities. Results indicate that there are areas on the dredges (crane, suction pumps and diesel engines) where sound levels greater than 90 dB(A) are pres­ ent. In addition, crushers and screens used in the processing of the sand and gravel also generate sound levels greater than 90 dB(A). Although no surveyed worker exceeded the Mine Safety and Health Administration’s (MSHA’s) permissible exposure level (PEL) of 90 dB(A) eight-hour time-weighted average (TWA8), laborers, mechanics, oilers, helpers, pickers and greasers are the workers most likely to be exposed to hazardous sound levels and to thus develop NIHL over time. Introduction Exposure to noise and noiseinduced hearing loss (NIHL) continues to be problematic for the U.S. mining industry. The problem is particularly severe because large, noisy equipment is found through­ out the industry. A National Institute for Occupational Safety and Health (NIOSH) analysis of NIHL among miners illustrates the extent of NIHL audiograms indicates the number of miners with hear­ ing impairments (defi ned as an average hearing thresh­ old level of 25 dB or greater for the frequencies 1,000, 2,000, 3,000 and 4,000 Hz) increased with age until age 50, at which time 49 percent of the metal/nonmetal and 90 percent of the coal miners had a hearing impairment (NIOSH, 1996, 1997). Another NIOSH study looked specifically at noise exposure and hearing loss among sand and gravel miners (Landen et al., 2004). These studies were conducted at 24 surface and nine dredge operations. The results revealed that 69 percent of the miners’ noise exposures exceeded the NIOSH rec­ ommended exposure limit (REL) of (85 dB, A-weighted, as an eight-hour time-weighted average (TWA8)). In addition, 41 percent exceeded MSHA’s action level for enrollment in the mining industry. This analysis of several thousand in a hearing conservation program. Landen also reported that hearing protection use was low, with 48 percent of the subjects reporting that they never used hearing pro­ tection. To address NIHL issues in all mining, MSHA has published Health Standards for Occupational Noise Exposure (Federal Register, 1999). Requirements of the new standard include: • the adoption of an Occupational Safety and Health Administration (OSHA)-like Hearing Conserva­ tion Program (HCP), • enrollment in the HCP for workers exposed above an action level of 85 dB(A) eight-hour time weight­ ed average (TWA8), • reduction of worker exposures to or below a per­ missible exposure level (PEL) of 90 dB(A) TWA8 or equivalently a dose of 100 percent, • no reduction in noise exposure being allowed due to the use of personal hearing protection and • a requirement that mine operators use all feasible engineering and administrative controls to reduce noise exposures. NIOSH responded to the problem of noise overex­ posure in the mining industry by conducting an extensive cross-sectional survey of noise sources and worker noise exposures. Initially, these surveys were conducted in sur­ face and underground (room and pillar and longwall) coal mines, coal preparation plants, stone (aggregate) mines and crushing and processing facilities. Recently, these surveys have expanded to sand and gravel mines, including dredging and their associated crushing, sizing and processing facilities. According to MSHA, in 2005 there were more than 7,000 sand and gravel operations (approximately 6,200 surface and 800 dredges) in the United States disbursed as shown in Fig. 1. Employment in the sand and gravel industry exceeded 45,000 workers, with an average of six employees per mine. These sur­ veys are designed to monitor worker noise dose, measure equipment sound levels and understand the noise source/