Donald J. Garvey, CIH, CSP, CET, of 3M Company, offered some startling statistics to lead off his presentation about hearing conservation in the construction industry at Safety 2015 in Dallas.
Citing a recent study, Garvey noted, “Depending on the trade, one study of more than 1,300 noise measurements indicated approximately 70 percent of the construction workers had a full-shift time-weighed average (TWA) exposure at or above the National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit (REL) of 85 dBA. About 10 percent of those workers had full-shift average exposures above the current OSHA construction permissible exposure limit (PEL) of 90 dBA.”
In addition, some 50 percent of construction workers doing structural work routinely are over-exposed to noise levels 20 percent to 40 percent higher than the NIOSH REL, and in calculations made by the Center for Construction Research and Training (CPWR) using data from the 2010 National Health Interview Survey, 21 percent of construction workers self-reported some type of hearing problem. In addition, exposure to noise has been associated with non-hearing-related health impacts, such as increased pulse rate, high blood pressure, muscle tension, sleeplessness and fatigue.
“Those workers start taking shortcuts...they start slipping up,” said Garvey, and incidents and injuries increase.
Garvey’s presentation examined five main areas of construction hearing conservation:
Exposure assessment – What are the options to determine worker exposure?
Occupational exposure limits – What are the current regulatory and good practice limits for noise and how do they affect the evaluation of a worker’s exposure?
Use of hearing protection devices (HPD) – While engineering controls are the preferred method to prevent occupational exposure, in construction HPD typically is the control method utilized. If that is the case, how can selection and wearing practices be improved to maximize use and more importantly actual effectiveness?
Training – What techniques and insights can be utilized to improve training to make it more impactful to the worker and encourage hearing healthy attitudes and behaviors in the workforce?
Engineering controls – How can engineering controls be used more in construction?
Construction sites constantly change, noted Garvey. From the types of trades on the site on any given day to the job tasks performed by the individual worker (power saw versus hand saw, pneumatic nailer versus hammer), noise levels can fluctuate by considerable amounts. So, it’s difficult to get a time-weighted average. In fact, Garvey noted that one NIOSH researcher speculated that in order to obtain an accurate “average” for exposure, a construction worker should be monitored continuously for 14 days. “No one is going to continuously monitor a worker for 14 days,” acknowledged Garvey.
There are alternatives to traditional noise dosimetry, he noted.
One is the task-based exposure assessment model (T-BEAM), in which individual tasks are identified, the duration of each task noted and sound levels related to the task determined. Then a modeling of any combination of tasks and durations can be done using the formula: % Dose = (C1/T1 + C2/T2 +…..Cn/Tn) x 100
% Dose – percentage of daily maximum allowable dose (e.g. 85 dBA 8-hour TWA = 100 percent)
Cn = duration (in hours) worker spends at a specific sound level
Tn = allowable duration (in hours) for the specified noise level (e.g. NIOSH Table 1-1) (NIOSH 1998)
Garvey used an example of repairing asphalt pavement where the task of jackhammering of the old pavement might be 2 hours in duration, the noise level is 102 dBA and the allowable exposure duration per NIOSH in hours is 0.16. Other tasks performed by that worker in a day might be driving a truck (2 hours at a dBA of 78 with an allowable exposure duration per NIOSH is 25 hours) and repairing potholes (4 hours at 86 dBA with an allowable exposure duration of 6.5 hours). This means the percentage dose = (2/0.16) + (2/25) + (4/6.5), so the percentage dose = (12.5 + 0.08 + 0.6) x 100, which equals 1319 percent of the allowable dose or an equivalent 8 hour TWA of 96.2 dBA.
Relating exposure to activity makes the risk more real to the exposed worker, said Garvey. Discussing a worker’s exposure in terms of specific tasks, sound levels and duration is more impactful than merely relaying the 8-hour average or full shift dose. While T-BEAM can be effective, there are drawbacks, he added. For example, is the worker’s task “building wall forms,” or is it sawing, hammering, material handling and transportation?
“The safety professional has to strike a balance of specificity of task, practicality of recognizing/differentiating between tasks and the determination of time on task,” said Garvey.
Another option is making the exposure limit a ceiling limit. A ceiling limit, unlike a TWA exposure limit, cannot be exceeded at any time during the work cycle. Because of the difficultly in establishing a worker’s TWA, the ANSI/ASSE A10.46-2013 Hearing Loss Prevention in Construction and Demolition Workers standard recommends a ceiling limit of 85 dBA. [ANSI 2013] Any exposure above 85 dBA (even instantaneously) would be considered an overexposure and require controls be implemented.
Any exposure above 85 dBA (even instantaneously) would be considered an overexposure and require controls be implemented. This provides several advantages, said Garvey, among them:
- Simplified rules for when HPD must be worn. With a ceiling exposure level, HPD should be worn whenever high noise exposures occur regardless of task exposure duration or full shift exposure. NIOSH notes that it is prudent to wear HPD during all high noise exposures regardless of the 8-hour TWA [NIOSH 1998].
- Less complicated exposure assessment since there is no need to determine the 8-hour TWA.
- A basic, relatively inexpensive sound level meter can be used to make noise level determinations.
Occupational Exposure Assessment
The criteria used to evaluate that exposure and determine what actions need to be taken varies. Currently, OSHA has an 8-hour time weighted average (TWA) permissible exposure limit of 90 dBA for the construction industry (29CFR1926.52). When determining the 8-hour TWA, a 90 dBA measurement threshold is applied, meaning that only noise 90 dBA and above is integrated into the calculation. All noise below the threshold (less than 90 dBA) is ignored. For a theoretical 8-hour work day at a continuous 89 dBA, the final dosimeter reading would be 0 percent of the allowable daily noise dose.
For noise above 90 dBA, OSHA uses a 5 dB exchange rate to account for the increased energy level of the noise as the decibel level increases. For every 5 dBA increase over 90 dBA, the allowable exposure duration is reduced by 50 percent. The worker can be exposed to 90 dBA for up to 8 hours. If the TWA exposure increases to 95, the allowable exposure would be halved to less than 4 hours. If the exposure level increases to 100 dBA, the allowable exposure duration is halved again to 2 hours.
NIOSH and the American Conference of Governmental Industrial Hygienists (ACGIH), recommend a different occupational exposure limit and different monitoring parameters when assessing worker exposure. Both groups recommend an 85 dBA exposure limit using an 80 dBA threshold level and 3-dB exchange rate. Depending on the sound levels encountered, variability during the work shift and occurrence of impulse noise, this can lead to significantly different findings compared to OSHA criteria. Under the NIOSH criteria, 8 hours of exposure at 85 dBA would yield 100 percent dose exposure.
Use of Hearing Protection Devices
Engineering controls is the preferred method of reducing noise exposure, and per OSHA, required to be used to the extent feasible, HPD is the most commonly used control on construction sites. The actual and effective use of HPD typically is poor, said Garvey. He said this can be attributed to the transient nature of the workforce; the abstract, gradual and painless nature of noise-induced hearing loss; the lack of an immediate cause/effect loop; and the annoyance and potential discomfort caused in some cases by wearing HPD has led to low usage rates of HPD in the construction industry.
Garvey noted that effective use depends on both duration of use and actual attenuation achieved. Several studies have reported that construction workers, on average, use HPD about 20 to 40 percent of the time that measured noise levels exceeded 85 dBA. Reasons for low use of HPD include:
- Lack of comfort
- Lack of availability on the job site
- Lack of training on proper use of HPD
- Over attenuation –HPD frequently is selected solely on the basis of high NRR. However, around 90 percent of TWA occupational noise exposures are 95 dBA or less. An HPD that delivers 10 dB of actual attenuation will cover the majority of exposures and reduce noise exposure below 85 dBA. The ANSI/ASSE A10.46 standard suggests attenuation below 70 dBA be considered overprotection, which can create its own hazards.
- Personal selection – In many cases, only one type of HPD is provided. Any single product can overprotect workers or be uncomfortable for some people to wear. Ear canal size and shape varies significantly from person to person.
- Safety climate and worker’s perception of safety’s priority in the workplace.
- Compatibility with other personal protective equipment.
- Style and ease of use.
Because of the unpredictability and intermittent exposure to noise, it is important that construction workers be able to recognize hazardous exposures and know how to protect themselves, said Garvey. Effective training particularly is important for workers who are just entering the construction trades. He noted that a 25-year-old construction carpenter who does not use hearing protection has the hearing acuity of a 50-year-old non-occupationally noise-exposed person.
“This group particularly has a critical need for effective HCP training to reduce exposure and increase use of HPD before hearing damage can start to occur,” Garvey said.
Most training discusses the effects of noise, the advantages and disadvantages of HPD and the care of HPD. Garvey suggests that training focus on helping employees master the insertion of HPD, address barriers to wearing HPD, discuss the benefits of wearing HPD and focus on the employee having a positive impact on his or health by wearing appropriate HPD.
While HPD is the most commonly used method of reducing noise exposure for workers on construction sites, Garvey noted that OSHA emphasizes engineering controls whenever possible. These engineering controls can include:
- Reduction of vibration from surfaces – e.g. sandbags on re-bar when cutting, securely clamping work piece as close to the work area as possible when grinding.
- Remote-operated equipment – e.g. rig-mounted hydraulic pavement breakers. This also potentially can reduce other health hazards such as ergonomic and silica exposures.
- Use of electrically powered equipment instead of diesel powered and hydraulic powered instead of pneumatic.
- Distance – moving workers away from noisy equipment (or vice versa). A 105 dBA noise source at a distance of 5 feet would be 102 dBA, at 20 feet would be 90 dBA and at 40 feet would be 84 dBA depending on other surrounding noise sources.
- Restricted or controlled access zones around high noise areas to limit the number of persons potentially exposed.
- Worker rotation to spread the noise energy out over several workers.
- Shutting down equipment when not in use.