Unique challenges to working safely are present in research facilities, especially laboratories. This month, the Safety Guys alert you to potentially significant noise hazards in the workplace. What noise are we talking about, you ask? Most important, we mean conditions and situations that can lead to noise-induced hearing loss (NIHL). They are most commonly related to equipment noise that may hinder communication, disturb concentration, or reduce performance. Therefore, we hope you start thinking about such not-so-obvious hazards as high-noise areas.
Can you hear me now?
Many areas within laboratories and especially research facilities are inherently noisy. Excessive noise can result from the equipment in use, such as centrifuges, sonicators, high-pressure air cleaning and supply equipment, vacuum pumps, and wet vacuum systems. Exposure to loud noise for long enough periods can result in permanent loss of hearing. NIHL is forever and cannot be treated medically. However, prevention is usually easy. So how loud is too loud? A quick and useful method of checking areas for excessive noise is the “conversation test.” Standing one to three feet apart, attempt a normal conversation with another person in a noisy area. If conversation is difficult or impossible, then the noise might be excessive. Have all areas evaluated by a qualified person knowledgeable in occupational noise, measuring techniques, data analysis, and control alternatives.
What are the legal requirements?
Noise is measured as sound-pressure levels in units known as decibels (dB). In standard workplaces, OSHA limits employee noise exposure to 90dB averaged over an eight-hour work shift (measured on the A-scale with slow response using a standard sound-level meter/ SLM). This is referred to as the permissible exposure limit (PEL). According to OSHA regulations, employees must not be exposed to noise this loud without protection. The OSHA regulations must be followed and are contained in 29 CFR 1910.95.1
The American Conference of Governmental Industrial Hygienists highly recommends a more conservative threshold of 85dB, referred to as a threshold limit value (TLV), even though it is technically a guideline.2 This value also equates to the OSHA action level and triggers the need to implement a hearing conservation program (HCP). If noise levels exceed 85dB, then the employer must develop an HCP for exposed employees, which we will discuss in more detail below.
Assessing noise exposures
We mentioned measuring noise levels with an SLM. This is commonly the first step and is called a noise survey. Using a good SLM, you simply canvass all work areas and note their noise levels. Any areas showing more than 85dB should be targeted for additional assessment and personal noise-monitoring as appropriate. Both the PEL and TLV are measured as eight-hour time-weighted averages.1,2 Therefore, if your noise survey shows areas that exceed either the PEL or TLV, you should plan to conduct full-shift noise exposure monitoring for a representative number of exposed workers. This type of testing is called personal noise dosimetry. For an entire work shift, workers wear dosimeters that measure the average noise level and calculate a percentage of allowed dose, or exposure. The dose percentage is then compared to corresponding OSHA tables and all employees exceeding 100 percent will need to use hearing protection and be placed in your HCP.
The HCP details all the steps that must occur to protect exposed employees. All employees covered by the HCP must have baseline audiometric testing and annual tests thereafter. They must also be provided appropriate hearing protection and trained on its proper use. These measures and record keeping are all required under the OSHA standard.
Audiometric testing is used to assess NIHL for workers and to monitor trends over time. Usually NIHL is reflected in a reduced response to frequencies above 2,000 hertz (Hz) during audiometric testing. Since normal human speech is in the 2,000-4,000 Hz range, NIHL is debilitating at work and in daily life and can have far-reaching consequences. All confirmed and persistent NIHL must be recorded and reported to OSHA. Corrective actions are developed and applied by the occupational health professional running the HCP.
Noise also obeys laws of physics. Control of excessive noise falls into three categories: engineering controls, administrative controls, and personal protective equipment. Under the OSHA standard, engineering controls are used first against the hazard. They can include the purchase of newer, quieter equipment, shielding or installation of acoustical sound-deadening enclosures, and/or treatments on walls and ceilings. Administrative controls entail limiting the time an employee spends in a noise hazard area or assigning more than one employee to split the time to complete a task. The last line of defense for preventing excessive noise exposure is using personal protective equipment such as earplugs or earmuffs.
In this issue we have touched the surface of dealing with noise hazards. We hope that you consider potential noise hazards that may impact your facility’s safety. In coming issues, we will delve deeper into noise assessments and control alternatives, including the pros and cons of different hearing protection devices. Until next issue, remember: safety first!
1. Occupational Noise Exposure, 29 CFR 1910.95, US Department of Labor, Occupational Safety and Health Administration (Washington, DC, 2008), https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=standards&p_id=9735.
2. Threshold Limit Values and Biological Exposure Indices, American Conference of Governmental Industrial Hygienists (Cincinnati, OH, 2011), http://www.acgih.org/.