Variability in Fit Test Result for Earplugs and the Fraction of Noise Exposure Dose of Coal Miners due to Failure to Wear

Researchers suggested that the individual fit test be conducted to estimate the protection effectiveness of workers’ hearing protection device (HPD) while working. Practically, it is convenient to conduct single, instead of multiple, fit test measurement. This study examined if a single trial of earplug fit test can represent multiple performances. Additionally, it investigated how much noise exposure was due to the miners’ failure to wear earplugs at work. A total of 11 subjects from 3 coal mines in West Virginia in 2009 were each repeatedly fit tested using the microphone-in-real-ear technique on their earplugs. For each miner values of noise reduction (NR) were determined. The same fit tested miners each wore the earplugs doing his normal full-shift work. The real-time noise doses were determined continuously using the two dosimeters, one at the shoulder and the other under the earplug for determining potential exposure dose and the dose the ear actually received. Most subjects’ noise reduction values varied over a range of more than 10 dBA, suggesting that subjects should be fit tested with multiple donnings. Failure to wear the earplug was an important factor in determining the miners’ noise exposure, accounting for 64.6% of their doses at ear on average and ranging from 33.3 to 93.4% across these subjects. Nearly half (45.5%) of the coal miners might not receive adequate protection with their earplugs. 35.2% of miners never wore any hearing protectors in the high noise environment and were in very high risk of hearing loss. Thus, an important portion of miners were exposed to excessive noise although the earplugs were provided.