C. Keil, Bowling Green State University, Bowling Green, OH; S. Yimer, Ministry of Labor and Social Affairs, Addis Ababa, Ethiopia; A. Kumie, Addis Ababa University, Addis Ababa, Ethiopia.
In Ethiopia, as in all developing countries, tension exists between the need for economic growth and the protection of worker health. Occupational exposures are poorly characterized, but often assumed to be high. Textile industries are a traditional part of the Ethiopian economy and are a potential growth sector. Noise exposures in an integrated textile mill were measured on three days as a preliminary assessment of the risk of hearing loss to the 2,200 mill workers. The mill receives raw cotton that is processed into yarn, woven into fabric, dyed, and sewn into clothing. The facility also includes a blanket mill. Noise exposure data were collected using data-logging dosimeters. Initially, three inspectors wore dosimeters during a walk-through evaluation. A time log of location and activity was also kept. Average exposures during the walkthrough were 83, 84, and 86 dBA. Analysis of logged sound levels and the time log revealed areas of highest exposures. Personal monitoring was conducted in areas with both excessive noise and multiple workers. Four partial-shift measurements in the spinning department indicated average personal exposures ranging from 84 to 89 dBA. Six partial-shift measurements were made in the blanket mill. Personal exposures ranged from 86 to 93 dBA. Area samples in the blanket mill were approximately 86 dBA. Workers did not use hearing protection. The degree of overexposure depends on the criteria used. ACGIH criteria values indicate large overexposures. Only one potential overexposure was identified using OSHA PEL criteria. However, many exposures exceeded the action level. Policy for selecting and enforcing noise exposure standards in Ethiopia must be guided by a balance of the risk of worker hearing loss and the need those workers have for jobs and other benefits of a developed economy. Nevertheless, low cost noise control options are available for addressing the high noise exposures identified.
L. Hager, Sonomax Great Lakes, Portland, MI.
Hearing protection device (HPD) performance measures have been historically driven by various means of discounting the laboratory developed, population-based, statistically derived noise reduction rating (NRR) as dictated in ANSI S3.19-1974 or ANSI S12.6-1996, and attempting to apply those adjusted values to individual users. New technologies permit the assessment of HPD performance directly on individual users, enabling the assessment of longitudinal intrasubject (single person) performance measures to validate both the protection offered by the HPD and the validation process. The technology described here (SonoPassTM) uses a modified microphone-in-real-ear (MIRE) technique to test the performance of specific custom hearing protectors on individuals in populations at various time intervals, measuring intrasubject attenuation consistency/variability over short term (2 minute), mid-term (2 hour), and long term (3 year) intervals to assess protected noise exposure values.
M. Witherspoon, S. Milz, Medical University of Ohio, Toledo, OH.
An ongoing pilot project is being conducted in Northwest Ohio to assess both the occupational and nonoccupational noise exposures of farm families. The study was designed to monitor three to five family members from three families living and working on the farm for one week each during planting, growing, and harvesting season. Dosimeters were programmed to record 24 hours a day, using both the OSHA and the NIOSH parameters. The participating family members completed daily time activity logs to record all on-farm and off-farm activities. Members of the research team also conducted time activity recording. Maximum occupational exposures exceeded the NIOSH guidelines, but not the OSHA standards for the full-time farmer.The season with the most farming time monitored was harvest (40.32 hours), and the longest working day for the farmer consisted of 11.25 hours during planting season. The average hours per day the dosimeter was worn by the farmer was 11.51 (growing), 7.34 (planting), and 11.42 (harvesting). The farming activity with the lowest minute-time-weighted-average (Leq dBA) was operation of a nontractor vehicle for 2 hours during growing season (average Leq of 46.2 dBA). The farming activity event with the highest average Leq was planting (0.77 hour at an average Leq of 90.2 dBA). Repair and maintenance of equipment events ranged from 60.9 to 75.1 Leq dBA during growing and planting seasons. Planting was monitored for a total of 6.31 hours with event averages ranging from 81.1 to 90.2 Leq dBA. Harvesting was monitored for 12.27 hours with event averages ranging from 82.7 to 84.8 Leq dBA. Tilling and plowing by the farmer were monitored for 20.53 hours with average Leq ranging from 78.0 to 89.5 dBA during events. Noise hazardous activities (Leq > 85 dBA), including planting, plowing, and tilling, all occurred during tractor operation.
E. Berger, E-A-R/Aearo, Indianapolis, IN.
Since World War II, the human and financial costs associated with hearing loss among military veterans have repeatedly drawn attention to noise and the need for hearing conservation in military settings. In recent years, tinnitus has also emerged as a significant noise-related concern. In the Veterans Benefits Act of 2002, Congress directed the Department of Veterans Affairs to contract with the National Academies for a study of noise-induced hearing loss and tinnitus associated with military service from World War II to the present. In May 2004, the Institute of Medicine of the National Academies convened a 13-member committee with expertise in noise and hearing loss to conduct this study. We were charged with reviewing the following topics: (1) the available data on hearing loss that could be expected in the armed forces; (2) sources of hazardous noise exposure during military service; (3) the levels of noise exposure necessary to cause hearing loss or tinnitus; (4) the time course of hearing loss following noise exposure, including whether onset can be delayed; (5) risk factors for noise-induced hearing loss and tinnitus; and (6) compliance by the military services with requirements for audiometric testing and the adequacy of the services’ hearing conservation programs to protect the hearing of service members. Our final report was issued in September 2005. The findings, summarized in this paper, include evidence suggesting that the use of hearing protection was, and still is, inadequate; that incomplete reporting or unsatisfactory compliance with audiometric testing requirements has impaired the usefulness of the military audiometric databases; and that military hearing conservation programs have not been adequate to protect the hearing of military service members since World War II. The report cites efforts to address noise exposure among military personnel, but observes that more must be done to make the programs effective.
A. Butler, Butler Health and Safety Inc., San Pedro, CA.
This study reports noise measurements made at the annual AIHCe convention, specifically at the MSA Cocktail Party. The object was to measure the noise exposure to participants in a large party. (Attendance, estimated by the sponsor, was approximately 2,500.) In addition, we measured the ability of professionals who routinely conduct noise measurements to estimate their own exposures.Existing noise data available for nonoccupational studies is almost entirely done with sound level meters and not dosimeters. In addition, literature searches on crowd noise yields almost entirely numbers concerning exposure to community noise (from a distance) or loud music. In the instant case there was no source of noise other than that of people partying: no band, no announcements over the PA system, etc. The results of the noise survey ranged from 83 to 92 dBA. The highest noise levels were reached quickly, generally within 20 minutes of entering the party, and did not decline until the subject left the party.There were a total of 69 noise estimates, all made either before or during the actual exposure. The estimates ranged from 70 dB to 98 dB. 40 estimates fell in the actual measured range and 26 estimates fell outside the range. The data show that noise exposures from combined human voices in such a party can be at hazardous levels. This has implications for occupational exposures to hotel and restaurant staff in such parties as well as other occupational and nonoccupational settings involving human voice noise. Fortunately, many IHs are capable of accurately estimating noise levels in such a setting and should be using their knowledge to promote quieter parties and/or more party friendly hearing protection. A protocol for identifying and measuring similar nontraditional noise exposures is presented.
J. Slagley, U.S. Air Force, Morgantown, WV; S. Guffey, West Virginia University, Morgantown, WV.
Active noise control (ANC) is particularly useful in HVAC ducts and exhaust stacks. Practical applications are limited to the 40–400 Hz frequency range, mostly due to the need for ANC systems to sample sound waves and predict them at a later point of propagation to determine and deliver the canceling signal. Plane waves are the most easily predictable waves and are the dominant source of acoustical energy in ducts from very low frequencies up to the first higher order mode (HOM) “cut-on frequency,” where HOM waves begin. HOMs from wave reflections are more difficult to predict and, therefore, control via ANC than plane waves. Acoustic equations indicate that the cut-on frequency for the first HOM in ducts varies inversely with diameter. The result is that somewhat higher frequencies can be controlled with ANC for smaller diameters. To test the diameter effects on ANC, a commercially available ANC system was used to reduce random noise in round ducts having four different diameters (4, 6, 8, and 12 inches). The results were broken into two frequency ranges. The lower range (40–500 Hz) was dominated by plane waves for all diameters. HOMs began in the higher range (630–3,150 Hz), starting with the 12-inch cut-on frequency at 565 Hz. Insertion loss (IL) ranged from 26–36 dB (40–500 Hz), and from 13–28 dB (630–3,150 Hz). IL increase with decreasing diameter was less in the plane wave region (0.7–2.9 dB) than the HOM (1.1–7.4 dB). There was no statistically significant difference (p = 0.1173) between IL for different diameters in the plane wave region (40–500 Hz). There was a statistically significant difference (p = 0.0009) between IL for diameters in the HOM region (630–3,150 Hz). The understanding of diameter effects on ANC in ducts aids in engineering control selection for noise, and may widen the applicability of ANC technology.
A. Ames, F. Akbar-Khanzadeh, Medical University of Ohio, Toledo, OH.
Athletes, employees, and bystanders may be exposed to unacceptable levels of noise at indoor sporting events. In general, these facilities are confined structurally without noise control devices in place. In this study, real-time sound level meters (Quest Models 400 and 500) were used to determine the levels of noise at the field-boundaries of six indoor children’s sporting events. Noise sources were the sport itself and loud voices. In karate classes, the minute-time-weighted average exposure (Leq dBA) ranged from 70 to 112 dBA (n = 68, mean ± SD of 83 ± 10 dBA) with peaks ranging from 100 to 147 dB (119 ± 12 dB). During soccer games, Leq dBA ranged from 70 to 86 dBA (n = 46, 74 ± 4 dBA) with peaks ranging from 92 to 132 dB (107 ± 8 dB). In basketball games, Leq dBA ranged from 71 to 77 dBA (n = 14, 74 ± 1 dBA) with peak noise levels ranging from 93 to108 dB (101 ± 4 dB). During hockey games, Leq dBA ranged from 70 to 86 dBA (n = 53, 75 ± 4 dBA) with peaks ranging from 92 to 142 dB (107 ± 9 dB). At swim meets, Leq dBA ranged from 80 to 94 dBA (n = 49, 88 ± 3 dBA) with peaks ranging from 92 to 118 dB (106 ± 7 dB). During volleyball matches, Leq dBA ranged from 74 to 83 dBA (n = 49, 78 ± 3 dBA) with peaks ranging from 102 to 121 dB (n = 9, 109 ± 6 dB). According to the recommendations of the World Health Organization, the peak impulse noise attributed to hearing impairment in children is limited to 120 dB, and for adults is 140 dB. The results of this study suggest that the noise levels in some sporting events exceeded recommended limits and the exposure should be controlled.
M. Shum, M. Kelsh, M. McNeely, Exponent Inc., Menlo Park, CA; C. Sulser,
Schmid & Partner Engineering AG, Zurich, Switzerland;
N. Kuster, Foundation of Research on Information Technologies in Society (IT’IS),
Zurich, Switzerland; A. Sheppard, Asher Sheppard Consulting, Redlands, CA.
Information in most epidemiologic studies on mobile phone exposure is derived from estimation of cumulative duration of use or the total/average number of calls, with relatively little attention to date on the actual radiofrequency (RF) energy or specific absorption rate (SAR) values involved. Recent International Agency for Research on Cancer (IARC) studies have incorporated RF energy estimates specifically for GSM technologies. Our objective was to observe inherent differences between mobile phones of various technologies (i.e., CDMA, TDMA, Analogue, and GSM), manufacturers, and styles under different environmental conditions in the San Francisco Bay area. The development of a mobile phantom SAR measurement system that allows real time estimates of energy output, which is then linked to device-specific SAR distributional data, allows for more precise exposure evaluation. Two phantom heads, each containing two dipole field probes placed near each ear canal, were used to simultaneously evaluate radiated power absorbed in the dielectric medium (i.e., SAR). The phantom field system was installed in a van to conduct tests while driving, which permitted evaluation of the effects of changing distances to base stations and different environments. Stationary measurements were also collected at predetermined locations for each route. A global positioning system receiver synchronously recorded location during the measurement period. Our results indicated that GSM data were dominated by handovers as evidenced by peaks in the time series data, whereas TDMA, CDMA, and analogue were not. Mobile phones using the CDMA technology produced the lowest peak power levels and analogue technology produced the highest of all four technologies. Mobile phone output power and SAR levels will be controlled over a wide dynamic range by the base station in a manner that differs greatly among technologies and may be an important factor in estimating exposure to individuals.
G. Sturchio, Mayo Clinic, Rochester, MN; C. Lungu, University of Alabama-Birmingham, Birmingham, AL.
This presentation investigates the uncertainties in calculating the radiation dose to occupationally exposed nonradiation workers and to members of the public from exposure to patients who have received diagnostic or therapeutic nuclear medicine procedures. Hospitals and clinics performed approximately 18.4 million nuclear medicine procedures in the United States in 2002, a 9% increase from 2001. The current methodology recommended by the Nuclear Regulatory Commission assumes that the patient is an unattenuated point source, and the absorbed dose to the exposed individual is calculated using an inverse square relationship to a point in space. The NRC model is an oversimplification since it does not account for radiopharmaceutical distribution or self-absorption in the patient, it does not account for the actual source to receptor geometry, and it does not account for energy deposition in the exposed individual. Monte Carlo techniques, utilizing mathematical anthropomorphic phantoms, are used to examine the impact of the NRC model simplifications. These techniques have demonstrated that the measured dose rate at 1 meter from a patient administered 131I will overestimate the radiation dose to an exposed individual by 61%.
Posted May 30, 2006