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Noise Exposure for Local Governments and Contractors Disclaimer: This material is designed and intended for general informational purposes only, and is not intended, nor shall it be construed or relied upon, as specific legal advice. INTRODUCTION Loud sounds can damage sensitive structures in the inner ear and cause hearing loss. Noise-induced hearing loss can affect persons of any age and can be caused by a one-time exposure to intense noise or continued exposure to loud sounds, but it is preventable. Employee education is crucial for prevention, including noise exposure awareness, whether at work or during leisure activities. They need to understand how noise-induced hearing loss occurs, the equipment or operations that produce hazardous noise and the control measures in place to reduce or eliminate it. Many employees perform a wide range of tasks over a 12-month period and their noise exposures vary daily or seasonally. To promote health and safety for local governments and construction workers, EMC Insurance Companies has compiled noise data from a variety of noise sources commonly encountered. This document does not include the requirements of a hearing conservation program (HCP); however, that information can be found in EMC’s Hearing Conservation LPIM. The information provided in this document is designed to protect worker hearing by using the recommended guidelines established by the American Conference of Governmental Industrial Hygienists (ACGIH) and the National Institute for Occupational Safety and Health (NIOSH). NIOSH and ACGIH both utilize a 3-dB exchange rate (the rate at which the noise dose doubles) with an 8hour Time-Weighted Average (TWA) exposure threshold of 85 dBA. This approach is more conservative than the traditional 5-dB exchange rate utilized by OSHA and offers a greater opportunity to identify high noise exposures and prevent employee hearing loss. EMC’s Environmental Health Services and many other industrial hygiene organizations1 suggest implementing a Noise Control Program based on a noise exposure limit for an 8-hour TWA of 85 dBA (a dose of 100 percent) with a 3-dB exchange rate. Noise intensity (loudness) and duration (time) of exposure are the critical factors in evaluating the potential for employee hearing loss. Operations that produce “high noise levels” for a short duration may not be as harmful as a lower noise level task performed for hours daily. On the other hand, an extremely loud noise (such as gunshots or a jet engine) may only require a short duration to cause permanent hearing damage. This document addresses the precautions necessary to protect employees’ hearing when operating equipment typically used by local governments and construction companies. EMC has gathered noise level data from various types of equipment over several years from multiple government and construction jobsites. The actual noise levels on the job site will vary depending on several factors, including: the equipment age, the presence and condition of any 1 American Industrial Hygiene Association, www.aiha.org, NIOSH, www.cdc.gov/niosh, ACGIH, www.acgih.org Page 1 10-6-14 Noise Exposure for Local Governments and Contractors sound-reducing features (mufflers, etc.), the brand of equipment, the overall maintenance of the equipment and the operation being performed. MEASURING NOISE The two basic instruments used when measuring noise are a sound level meter (SLM) and a noise dosimeter. Both instruments measure noise, but provide different information about worker exposure. They are briefly defined below: A. Sound Level Meter – An SLM is a handheld unit that measures real-time noise levels. The benefit of this type of monitor is that it can measure the noise generated by a given piece of equipment (such as operating a concrete saw). The noise levels are expressed using the “A scale” in decibels (dBA). The dBA scale is used for compliance with OSHA regulations and guidelines from ACGIH and NIOSH. B. Noise Dosimeter – A noise dosimeter is generally the preferred method for measuring employee noise exposures. It is a portable unit worn by the worker throughout the workday, continually monitoring the employee’s noise exposure levels. The noise levels are then “averaged” over the work shift by the dosimeter to provide one noise level number, generally expressed using the “A scale” in decibels (dBA). The A Scale (dBA) is used when measuring noise in the work environment because it approximates how our ears respond to sound. Both the SLM and noise dosimeter should be set to use this scale. The noise dosimeter is the best way to determine a worker’s exposure on a particular day. However, workers who perform various jobs on an infrequent schedule would require multiple monitoring days throughout the year to determine their noise exposure level. Another approach is to use the SLM to measure the noise exposure of workers while they perform various tasks or operate various pieces of equipment. If the noise levels are greater than 85 dBA, the workers need hearing protection. SOUND LEVEL MEASUREMENTS The allowable exposure time to a particular noise level can be calculated using Equation 1, shown below. Table 1 uses Equation 1 to determine the allowable exposure time in hours or minutes for noise exposure levels between 80 and 110 dBA. Eq. 1 or NL is the measured noise level in dBA. Example: You are purchasing a new portable air compressor to operate a jackhammer. The manufacturer’s product information estimates that the noise level is 90 dBA at the operator’s location. Inserting 90 dBA into Equation 1 indicates the operator can be exposed to 90 dBA for 2.5 hours before exceeding the allowable exposure. Exceeding this time limit could result in noise-induced hearing loss if adequate personal protective equipment was not used. Page 2 10-6-14 Noise Exposure for Local Governments and Contractors Table 1 Noise Levels and Allowable Exposure Time Using ACGIH Calculations Decibel Reading from SLM ACGIH Time Allowable in Hours ACGIH Time Allowable in Minutes 80 25.398 1524 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 20.159 16.000 12.699 10.079 8.000 6.350 5.040 4.000 3.175 2.520 2.000 1.587 1.260 1.000 0.794 0.630 0.500 0.397 0.315 0.250 0.198 0.157 0.125 0.099 0.079 0.063 0.050 0.039 0.031 0.025 1210 960.0 762.0 604.8 480.0 381.0 302.4 240.0 190.5 151.2 120.0 95.2 75.6 60.0 47.6 37.8 30.0 23.8 18.9 15.0 11.9 9.4 7.5 6.0 4.7 3.8 3.0 2.4 1.9 1.5 Tables 2 and 3 list noise level readings for various types of equipment under normal operating conditions, as measured by EMC’s Environmental Health Services. In some cases, multiples of the same equipment type are listed to illustrate that similar equipment can generate different noise levels. The third column lists the maximum exposure time during a workday without requiring hearing protection, based on ACGIH and NIOSH criteria. Page 3 10-6-14 Noise Exposure for Local Governments and Contractors Table 2 Noise Levels for Equipment Recorded by EMC Environmental Health Services Noise Level Allowed Exposure Time Location or Equipment dBA Without Hearing Protection Power Plant Generator 105 4.75 minutes Offices 73 Unlimited Streets Jackhammer 98 23.75 minutes Dump Truck 80 Unlimited End Loader 93 76 minutes Road Grader 98 23.75 minutes Road Grader 91 120 minutes Tractor 100 15 minutes Backhoe 98 23.75 minutes Street Sweeper (new) 88 240 minutes Street Sweeper (older) 91 120 minutes Vac Hauler 93 76 minutes Wastewater Jet Vac 83 762 minutes Pump Room 90 151 minutes Clarifier 89 190 minutes Control Room/Lab 68 Unlimited Vac Tron Mini-Vac 93 76 minutes Large Vac 98 23.8 minutes Water Plant Pre-Treat 82 960 minutes Blower Room 93-101 76 minutes to 12 minutes Emergency Generator 108 2.37 minutes Emergency Generator 101 11.9 minutes Engine Room 99 19 minutes Applicator 87 302 minutes Lawn and Snow Riding Mower 91 120 minutes Push Mower 92 95 minutes Push Mower 91 120 minutes Large Commercial 3-Deck Mower – Open 94 60 minutes Mower with Cab 81-82 960 minutes to 1210 minutes Sharpening Mower Blades 97 30 minutes String Trimmer 95 47.6 minutes Hedge Trimmer 99 19 minutes Leaf Blower 96 37.8 minutes 27” Snow blower 94 60 minutes Data compiled from previous monitoring surveys conducted by EMC Insurance Companies. Page 4 10-6-14 Noise Exposure for Local Governments and Contractors Table 3 Noise Levels for Equipment Recorded by EMC Environmental Health Services Allowed Exposure Time Equipment Noise Level dBA Without Hearing Protection Wood Chipper 96 37.8 minutes Wood Chipper 101 11.9 minutes Portable Generator 90 151 minutes Newer Portable Generator 85 480 minutes Generator 94 60 minutes Newer Generator 80 Unlimited Approximately 8 Feet Away Chain Saw 94 60 minutes Chain Saw 100 15 minutes Hammer Drill 97 30 minutes DitchWitch RT70 Trencher 94 60 minutes 120 minutes DitchWitch Walk-Behind 1820 91 DitchWitch 350SX Knife Vibrator 99 19 minutes DitchWitch R40 Trencher 94 60 minutes New Backhoe in Cab 75-76 Unlimited New Backhoe Outside 78-83 Unlimited to 762 minutes Concrete Saw – Hand 102 9.5 minutes Target Pro 65 II Concrete Saw 96 37.8 minutes Target Pro 35 II Concrete Saw 98 23.8 minutes Tanaka Gas Drill 100 15 minutes Truck Outside Tamp 85 480 minutes Hydraulic Chain Saw on Bucket Truck 86 381 minutes Power Washer 86 381 minutes Jackhammer with Bobcat – Inside 101 11.9 minutes Jackhammer with Bobcat – Outside 101 11.9 minutes Tractor with Backhoe 89 190 minutes Bobcat 99 19 minutes Mosquito Fogger 101 11.9 minutes Portable Air Compressor 85 480 minutes Front-end Loader 86 381 minutes Air Impact Wrench 98 23.8 minutes Pneumatic Wrench – 1” 105 4.7 minutes Pneumatic Wrench – 1/2” 101 11.9 minutes Chop Saw 96 37.8 minutes Ground Tamper 94 60 minutes Drill with Ratchet Clutch 99 19 minutes Data compiled from previous monitoring surveys conducted by EMC Insurance Companies. Page 5 10-6-14 Noise Exposure for Local Governments and Contractors EVALUATING MULTIPLE NOISE EXPOSURES DURING A WORKDAY – SLM To evaluate employee noise exposure during a workday, first identify which tasks generate noise in excess of 85 dBA using a sound level meter (SLM). Position the microphone near and perpendicular to the worker’s ear while they perform a specific task. Tables 2 and 3 provide approximate noise exposures, but will not suffice for compliance noise exposure determinations. After collecting noise measurements for specific tasks or pieces of equipment, determine the length of employee exposure during a typical day. It may be helpful to use a “worst case” scenario when determining peak exposures. If an employee is exposed to the same decibel level for an entire 8-hour shift, the calculation is relatively easy. The exposure in dBA is simply the noise level of the equipment or task. For example, if an employee operated a large, commercial 3-deck mower (94 dBA from Table 2) for 8 hours, the TWA would be 94 dBA. However, few tasks on this list are performed for 8 hours or have an engine at full power for that length of time. To calculate an exposure for multiple tasks, add the individual exposures using the following formula: Eq. 2 Where: % Dose = Percentage of an 85 dBA 8-hour exposure (any number greater than 100 indicates an exposure over 85 dBA) C = Actual time spent exposed to a noise level T = Allowable time at that noise level using Eq. 1 or Table 1 For example: An employee spends 2 hours mowing while exposed to 94 dBA, then spends 10 minutes operating a string trimmer at 95 dBA and 5 hours operating the new backhoe (74-75 dBA exposure). All noise levels below 80 dBA are considered insignificant and not considered in the calculation. Therefore, the 5 hours spent on the backhoe is treated as zero. In this case: Note: The units (minutes or hours) for actual time and allowable time must be the same. Any number greater than 100 percent indicates a Time Weighted Average (TWA) above 85 dBA. This percentage result can be converted to an estimated decibel level, if necessary. Using the example above, the noise dose of 221 percent while mowing and trimming is equivalent to a TWA of 88.4 dBA and requires hearing protection. Contact your EMC Risk Improvement representative for additional information. Page 6 10-6-14 Noise Exposure for Local Governments and Contractors EVALUATING NOISE EXPOSURES – NOISE DOSIMETRY When using a noise dosimeter to measure an employee’s TWA noise exposure, record the various tasks performed and their duration. Consult with managers and employees to determine if the noise exposure during the monitoring period was that of a typical day. Additional noise monitoring may be necessary to determine a worker’s true average exposure. EMC’s Environmental Health Services recommends using ACGIH or NIOSH criteria when evaluating noise dosimeter data. Noise surveys performed by EMC will provide both ACGIH and OSHA criteria and recommendations. HEARING PROTECTION EMC’s Environmental Health Services recommends hearing protection for all employees performing tasks that exceed 85 dBA. This approach should protect workers from most hazardous noise exposures they encounter. Noise Reduction Rating (NRR) is a unit of measurement used to determine the effectiveness of hearing protection devices to decrease sound exposure within a given working environment. The calculation used by OSHA to determine the noise reduction provided by a given hearing protector is: Eq. 3 Where: NRR = Manufacturer-determined noise reduction rating The selection of hearing protection is determined by subtracting 85 dBA from the highest noise level exposure. This number represents the minimum sound level reduction in decibels (dBA) required of the hearing protection in order to achieve a noise level of 85 dBA in the ears. Example: The highest exposure experienced by an employee is 96 dBA while using a leaf blower. The NRR listed on the earplugs package is 31. 96 dBA – 85 dBA = 11 dBA noise reduction required (31 – 7) ÷ 2 = 12 dBA noise reduction, so the earplugs are adequate In this case, the earplugs, when properly fitted and worn, will reduce the wearer’s noise exposure by an estimated 12 dBA, reducing the noise at the ear to 84 dBA. Page 7 10-6-14 Noise Exposure for Local Governments and Contractors OSHA requires employers to provide a variety of hearing protection types (at least two) to employees at no cost to them. EMC also recommends this practice. Hearing protector types include: Rollable/foam plugs – Compressible foam that is rolled and inserted into ear. It expands to fill the ear canal and seal against the walls. Preformed/premolded – Reusable PVC or silicone plugs with1-5 flanges on a stem. Available as one-size-fits-most or in several sizes. Custom – Vinyl, acrylic or silicone that is molded by filling the ear canal to make a mold; specific for each ear. NRR depends on quality of the mold. Canal caps/banded – Generally, a foam cap or tip attached to a headband that caps off the ear canal entrance. They generally provide less protection than ear muffs or plugs. Muffs – Plastic cups that fit against the head and enclose the entire external ears and is sealed off with fluid or foam-filled padding. May be used in conjunction with ear plugs to protect against extremely loud noises. When a single type of hearing protection is inadequate, it may be necessary to wear double hearing protection consisting of earplugs and earmuffs. Earmuffs, when worn in conjunction with earplugs, will add an estimated 5 dBA to the OSHA-calculated NRR for the earplugs. Generally, the highest NRR for earplugs is 33, which will provide an estimated OSHA noise reduction of 13 dBA. Adding 5 dBA for the addition of earmuffs, increases the OSHA-calculated noise reduction to 18 dBA. This means that an employee wearing both earplugs (NRR 33) and earmuffs would have a maximum allowable noise exposure of 103 dBA (18 dBA + 85 dBA). As a general rule, wearing double hearing protection whenever the expected noise level is 100 dBA or greater is a good occupational health practice and will help protect employees from noiseinduced hearing loss. EDUCATION & INFORMATION EMC Environmental Health Services can assist in evaluating the workplace noise levels. To schedule a noise survey or to request additional information, contact your agent, Risk Improvement representative or send an email to [email protected]. FOR ADDITIONAL INFORMATION Occupational Safety & Health Administration: www.osha.gov • Occupational Noise Exposure American Industrial Hygiene Association: www.aiha.org • Protect Yourself from Noise-Induced Hearing Loss National Institute for Occupational Safety & Health: www.cdc.gov/niosh • Noise and Hearing Loss Prevention © Copyright Employers Mutual Casualty Company 2014. All rights reserved. Page 8 10-6-14