Preventing Hazardous Noise and Hearing Loss during Project Design and Operation Prevention through Design (PtD) Prevention through Design (PtD) Why is PtD Needed? Description of can be defined as designing out Integrating PtD concepts into busi- Exposure or eliminating safety and health ness processes helps reduce injury and hazards associated with processes, Prolonged exposure to high noise levels structures, equipment, tools, or illness in the workplace, as well as costs can cause hearing loss and tinnitus. work organization. The National associated with injuries. PtD lays the Other health effects include headaches, Institute for Occupational Safety foundation for a sustainable culture of fatigue, stress, and cardiovascular and Health (NIOSH) launched a safety with lower workers’ compensation problems [Yueh et al. 2003]. High noise PtD initiative in 2007. The mission expenses, fewer retrofits, and improved levels can also cause workers to be dis- tracted and interfere with communica- is to reduce or prevent occupational productivity. When PtD concepts are in- injuries, illnesses, and fatalities by tion and warning signals. If workers do troduced early in the design process, re- considering hazard prevention in not hear warning signals, they may not the design, re-design, and retrofit of sources can be allocated more efficiently. take precautions to prevent hazards or new and existing workplaces, tools, injuries [NIOSH 1996, 1998; Yoon et al. equipment, and work processes Summary 2015; Cantley et al. 2015]. [NIOSH 2008a,b]. Exposure to high noise levels in the workplace can cause hearing loss and Workers at Risk Contents affect worker productivity and compen- An estimated twenty-two million work- ▶ Why is PtD Needed sation costs. This document describes ers are exposed to potentially damag- ing noise each year [NIOSH 2014a]. ▶ Summary case studies in which noise controls Although any worker can be at risk ▶ Description of Exposure were implemented that reduced worker for noise-induced hearing loss in the noise exposure. NIOSH recommends ▶ Workers at Risk workplace, workers in agriculture, min- ▶ Exposure Limits considering PtD concepts and incorpo- ing, construction, manufacturing and ▶ Protecting Workers from rating engineering noise controls during utilities, transportation, and the military Hearing Loss the project design phase of processes are at greater risk [Masterson et al. 2013; ▶ Case Studies and operations. NIOSH 2001]. ▶ Recommendations ▶ Acknowledgments ▶ References DEPARTMENT OF HEALTH AND HUMAN SERVICES Centers for Disease Control and Prevention National Institute for Occupational Safety and Health Exposure Limits exposure should be cut in half (these are is the most effective way to reduce noise referred to as exchange rates in standards). levels in the workplace [NIOSH 2001]. In the United States, occupational regu- Table 1 illustrates the relationship between According to the hierarchy of controls lations and standards were established sound exposure levels and durations for (http://www.cdc.gov/niosh/topics/hierar- to protect workers against the health both NIOSH and OSHA. chy/), such measures take precedence over effects of exposure to hazardous sub- The Mine Safety and Health Administra- using personal protective equipment such stances and agents when certain values, tion (MSHA) PEL for miners is 90 dBA. as earplugs [NIOSH 2015]. or limits, are reached. NIOSH establishes If a miner’s noise exposure continues to recommended exposure limits (RELs) exceed the PEL despite the use of engi- These noise reduction measures can lower for various hazards, but those limits are neering and administrative controls, the costs associated with workers’ compen- not enforceable by law; they are based mine operator must continue to use the sation for hearing loss, protect workers’ on best available science and practices. engineering and administrative controls to hearing, and improve productivity. Costs The REL for noise is 85 decibels, using reduce the miner’s noise exposure to as low associated with retrofitting noisy equip- the A-weighting frequency response over a level as is feasible [30 CFR § 62.130]. ment are also no longer necessary. an 8-hour average, usually referred to as time-weighted average (TWA); expo- sures at or above this level are considered Protecting Workers Case Studies hazardous [NIOSH 1998]. The Occupa- from Hearing Loss The following case studies demonstrate tional Safety and Health Administration how small design and operational changes Noise-induced hearing loss (NIHL) (OSHA) sets legally-enforceable permis- can reduce noise levels and reduce is 100% preventable; however, once sible exposure limits (PELs) that require associated costs. acquired, it is permanent and irrevers- employers to take actions to reduce worker ible [NIOSH 1998]. Understanding and exposures. The OSHA PEL for noise is 90 minimizing the risks are the keys to Case Study 1 dBA as an 8-hr TWA [29 CFR* 1910.95]. preventing noise-related injuries and Compressed air is often the most com- hearing loss. Eliminating or lowering Occupational standards specify a maxi- mon noise source in manufacturing plants facility and equipment-related noise at the mum allowable daily noise dose, expressed and other industries. It is used to operate source reduces the risks related to NIHL in percentages. For example, a person ex- equipment, such as air cylinders, air valves, and results in improved safety, produc- posed to 85 dBA per NIOSH or 90 dBA per solenoids, etc., or move parts/product, tivity, and comfort [Tak et al. 2009]. blow off debris, close flaps on corrugated OSHA over an 8-hour work shift, will reach containers (boxes/cases), or perform simi- 100% of their daily noise dose. The noise The best way to reduce noise exposure and lar service-type actions. The noise generat- dose is based on both the sound exposure reduce resulting hearing loss is to address ed by compressed air is caused by turbu- level and how long it lasts (duration) so for noise at the source by considering PtD lence from the mixing of gases with widely each increase of 3-dB (NIOSH) or 5-dB principles. “Engineering out” hazardous different velocities, particularly when the (OSHA) in noise levels, the duration of the noise found in the workplace before the high-velocity air stream flows into the *Code of Federal Regulations. See CFR in exposure occurs (e.g., by installing quieter relatively still surrounding air. Additional References. equipment or building an acoustic barrier) turbulence is created as the compressed air blows against objects, such as parts or sec- tions of the machinery. Table 1. The average sound exposure levels needed to reach the maximum allowable daily dose of 100% Compressed air noise can be controlled by reducing the air velocity to as low as practical while maintaining performance Time to reach Exposure level Exposure level requirements and by treating all open- 100% noise dose per NIOSH REL per OSHA PEL ended discharge lines and ports, including 8 hours 85 dBA 90 dBA standard air jets and nozzles with com- mercially-available quiet-design nozzles or 4 hours 88 dBA 95 dBA pneumatic silencers [IRSST 2015]. Addressing the noise produced by com- 2 hours 91 dBA 100 dBA pressed air provides the greatest noise 1 hour 94 dBA 105 dBA reduction per dollar invested, and can even have a payback in dollars through energy 30 minutes 97 dBA 110 dBA savings and life expectancy of equipment. 15 minutes 100 dBA 115 dBA Blowing compressed air through a 3/8-inch open pipe at a pressure of 71.5 pounds per square inch (psi) uses 109 standard feet per cubic minute (scfm). At an average cost of $0.015 per 35.3 standard cubic feet (scf), and an estimated use time of 40%, this equates to 704 hours of consumption per year. Therefore, the annual cost for the open pipe is: 109 ft3/min x $0.015/35.3 ft3 × 60 min /hr × 704 hours = $1956.44. By us- ing a quiet-design nozzle that provides the same air-flow service, but only uses 55.9 scfm, the resulting annual cost would be $1003.35, a savings of $953.09 per nozzle while reducing noise levels by 20 dBA [Driscoll 2011]. This approach was successfully demon- strated by two of the Safe-in-Sound Excel- lence in Hearing Loss Prevention Award™ (www.safeinsound.us) recipients. One of the recipients (Colgate-Palmolive Compa- ny) created a guidance document to opti- mize system operation, minimize air leaks and provide guidance on appropriate use of air tools. (http://www.safeinsound.us/swf/ Figure 1. Track mounted, air rotary drill rig colgate/). This effort involved (1) measur- ing, documenting, and optimizing air pressure settings for all pneumatic devices, dominant spike in the sound level spec- working near these machines are at greater (2) maintaining the pneumatic equipment trum. The researchers also conducted field risk of developing NIHL. The flight bars and monitoring the optimized settings tests to evaluate noise controls to reduce and the conveyor belt tail rotor were coated over time, and (3) locating and repairing in-cab sound levels. Hydraulic noise sup- with a thick, durable urethane coating to compressed air leaks from cracked hoses, pressors were successfully used to reduce reduce noise and improve the lifespan of failed seals, etc. At the beginning of the the structure-borne noise that is transmit- the equipment. The redesigned chain and implementation phase, worker doses were ted from the structure to the control panel. flight bars reduced sound levels by 6-7dBA reduced from 113 to 90 dBA 8-hr TWA, Further, the hydraulic noise suppressors at the operator ear. The reduction in noise and energy consumption was also reduced. and enhanced soundproofing lessened the allowed the noise exposure to remain This was also one of the approaches taken risk of hearing loss for workers by reduc- within the MSHA PEL [NIOSH 2009]. by another Safe-in-Sound recipient (United ing the in-cab exposure levels by as much Technologies) (http://www.safeinsound.us/ as 4 dBA at high idle and by 1 dBA when Recommendations swf/UTC/index.html) who reduced worker the rig was hammer drilling.