Twelve percent of the U.S. working population suffers from hearing loss (Am J Ind Med. 2018 Jun;61(6):477). A quarter of this hearing loss is attributable to exposures in the workplace (J Occup Environ Med. 2008 Jan;50(1):46). The National Institute for Occupational Safety and Health (NIOSH) initiated the Occupational Hearing Loss (OHL) Surveillance Project in 2009 to assess hearing loss trends among noise-exposed workers. In collaboration with audiometric service providers and others, the project has collected millions of de-identified worker audiograms from thousands of companies (NIOSH, 2018). While seven percent of workers not exposed to noise have hearing difficulty, the prevalence of hearing difficulty among noise-exposed workers increases to 23 percent (Am J Ind Med. 2016 Apr;59(4):290). Using the collected audiograms, the NIOSH OHL Surveillance Project has reported the prevalence, incidence, and adjusted risk of hearing loss among noise-exposed workers across industries.
Notably, one sector demonstrated a prevalence of hearing loss that was inconsistent with known or perceived noise exposures. A 2015 study conducted by NIOSH found that 18 percent of noise-exposed workers within the Health Care and Social Assistance (HSA) sector experienced hearing loss (Am J Ind Med. 2015 Apri;58(4):392). While this is similar to the overall prevalence of hearing loss among noise-exposed workers, only 13 percent of HSA workers reported exposures to hazardous noise, which is among the lowest of all industries (Am J Ind Med. 2018 Jun;61(6):477).
A recent study from the NIOSH OHL Surveillance Project looked deeper into the HSA industry, which includes establishments that provide a continuum of health care and social services to individuals (J Occup Environ Med. 2018 Apr;60(4):350). For example, industries range from Offices of Physicians (i.e., providing medical care exclusively), to Child Day Care Services (i.e., providing social assistance), with some industries providing a combination of the two (e.g., nursing and residential care facilities). Using the North American Industry Classification System (NAICS), this paper took a nuanced look at the sub-sectors within HSA. NAICS is an industrial classification system that groups workers into industries, with increasing specificity by digit. For example, Ambulatory Health Care Services is NAICS 621 (three-digit specificity) and Outpatient Care Centers, a sub-sector with more specific tasks within ambulatory health care services, is NAICS 6214 (four-digit specificity). This study analyzed the HSA industry at the two, three, and four-digit NAICS specificities to identify at-risk sub-sectors. The findings highlighted here are at the four-digit NAICS specificity.
HEARING LOSS IN HSA SUB-SECTORS
Audiograms from 8,702 noise-exposed HSA workers and 1.4 million other noise-exposed U.S. workers were analyzed in this study. Prevalence is the percentage or proportion of people with a condition, such as hearing loss. The overall prevalence of hearing loss for noise-exposed HSA workers was 19 percent. Three industries had a higher prevalence: Medical and Diagnostic Laboratories (NAICS 6215 at 32%), General Medical and Surgical Hospitals (NAICS 6221 at 26%), and Offices of Other Health Practitioners (NAICS 6213 at 24%; Fig. 1). Compared with a reference industry (Couriers and Messengers) with a hearing loss prevalence that most closely matched the prevalence of the non-noise-exposed working population, five of the 10 HSA sub-sectors had significantly greater risks of developing hearing loss. These sub-sectors were: Child Day Care Services (NAICS 6244), Community Food and Housing, and Emergency and Other Relief Services (NAICS 6242), Offices of Other Health Practitioners (NAICS 6213), Offices of Physicians (NAICS 6211), and Medical and Diagnostic Laboratories (NAICS 6215). The prevalence of hearing loss in each HSA sub-sector is depicted in Figure 1.
CAUSES OF HEARING LOSS
Many sources and levels of noise exposures within this sector are not known or have not been recently updated. For example, noise exposure assessments for Medical and Diagnostic Laboratories have not been updated since the 1980s. One older study found that background noise levels in these settings ranged from 60 to 75 dBA, generated by equipment such as analyzers, fume hoods, incubators, stirrer motors, refrigerators, and fans (Clin Biochem. 1981;14:157). These exposures over a work shift are likely below the NIOSH recommended exposure limit (REL) of an 85 dBA time-weighted average over eight hours. However, this level of background noise can lead workers to speak louder and increase the volume of phones, radios, and personal listening devices to potentially unsafe levels. HSA workers may also work longer than eight hours, which means noise exposures need to be of shorter durations to stay within the NIOSH REL. Updated studies are needed to identify current noise sources and exposure levels in this and other sub-sectors within HSA.
Despite the high prevalence of workers with hearing loss in some HSA sub-sectors, this sector has the highest percentage of workers who reported not wearing hearing protection when exposed to noise (74%; Am J Ind Med. 2009;52:358). This suggests a lack of awareness about the dangers of noise and hearing loss risk. The use of hearing protection and other behavioral changes (e.g., reducing the volume) could reduce exposures.
Chemicals that can damage hearing (i.e., ototoxic chemicals) can cause hearing loss or increase the harmful impact of noise on hearing. Antineoplastic (cancer-fighting) drugs can have ototoxic effects, and a study found that 17 percent of 1,339 oncology nurses had skin or eye exposures to these drugs within the past year (BMJ Qual Saf. 2012 Sep;21(9):753). Another study found that nurses and pharmacy workers who reported spills of antineoplastic drugs had poorer scores for “collegial relations with physicians,” suggesting that teamwork and workplace culture play a role in the risk of exposure (Cancer Nurs. 2015 Mar-Apr;38(2):111).
AWARENESS AND PREVENTION
Despite a low prevalence of noise-exposed workers and somewhat lower levels of noise exposure when compared with those of workers in other sectors, this study showed that many HSA workers are at risk of developing hearing loss. It should be noted that these documented “lower levels of noise exposure” are based on old estimates in limited situations—the only ones available and likely do not accurately capture the true levels of noise exposure in current environments with modern equipment. Noise sources in these settings need to be identified and characterized, in addition to sources of ototoxic chemical exposures. Reducing the level of noise at the source by using quieter equipment or engineering controls to encase/enclose the noise source is the most effective method for decreasing worker noise exposure. Documented interventions that can reduce noise exposures for HSA workers include modifying equipment to insulate/enclose noise sources, using acoustical treatment on laboratory walls and ceilings to dampen noise, limiting the number of visitors and visiting hours, and lowering the volume on phones and bells. Although not documented in this study, it can be assumed that lowering the volume on medical equipment alarms and televisions in patient rooms could also reduce noise exposures. For antineoplastic drugs, using closed-system transfer devices for administering drugs, using single-use gowns and double gloves, and fostering a blame-free environment for reporting spills can reduce chemical exposures.
Author's note: The findings and conclusions in this article have not been formally disseminated by NIOSH and should not be construed to represent any agency determination or policy. Go online for more information and publications on occupational hearing loss surveillance: https://www.cdc.gov/niosh/topics/ohl/default.html.
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