What can 35 years and over 700,000 measurements tell us about noise exposure in the mining industry?
Benjamin Roberts, Kan Sun, Richard L Neitzel
PMID 27871188WHAT IT FOUND
US mine noise measurements fell after the 2000 MSHA rule, by 4.5 dBA on average.
Reductions were uneven, and underground coal and metal mines still had many measurements above limits.
Key findings
01Mean measurements made using the permissible exposure limit fell from 84.4 dBA before 2000 to 79.9 dBA after 2000, and the paper reports an average decrease of 4.5 dBA.
02Underground coal mines had only a 0.8 dBA decrease in measurements against the permissible exposure limit, and 48.4% of underground coal measurements exceeded the action level after 2000.
03The job-title model predicted a decline of about 0.3 dBA per year for measurements against the permissible exposure limit and 0.2 dBA per year for measurements against the action level.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The analysis used existing workplace noise measurements, not patient hearing outcomes, so it cannot show whether hearing loss changed. The paper says reductions are likely partly due to regulation and technology, but it cannot separate those causes. Measurements were excluded when material mined was missing or when levels were implausibly low, and missing material could bias estimates if it was not missing at random. Job titles were grouped to estimate exposure, but job title alone may not capture similar exposures or day-to-day variability. The predictive model had low fit and should not replace personal noise monitoring. Reductions were not uniform; underground coal mines showed smaller decreases and some high-exposure categories increased.
Declared interests
The supplied text does not give an author conflict-of-interest statement. The article is labelled as supported by U.S. Government Public Health Service research.
The easy way to misread this
Do not treat the job-title model as a substitute for personal noise monitoring. The authors state that individual exposure varies day to day and model predictions should not be used in place of monitoring.