Personal Exposure Meters Research Articles

No association between occupational exposure to ELF magnetic field and urinary 6‐sulfatoximelatonin in workers

A suppression in melatonin secretion is one of the mechanisms proposed to explain the possible adverse effects of extremely low frequency magnetic fields (ELF-MF), but the results of research are inconclusive. This study investigated the effect of occupational ELF-MF exposure on 6-sulfatoximelatonin (6-OHMS). Exposure was monitored for three complete work shifts in 59 workers using personal exposure meters. Environmental exposure was also evaluated. Urinary 6-OHMS in morning samples, an indicator of night-time melatonin production, was measured. Urine was collected twice on Friday and the following Monday. Workers were classified according to ELF exposure as low exposed (<or=0.2 microT) or higher exposed (>0.2 microT): 6-OHMS did not differ between groups (P > .05) in either Friday or Monday urine samples. In addition, 6-OHMS was not related to exposure under multivariate analysis. The ratio between 6-OHMS in Monday versus Friday samples was also calculated to test the hypothesis of a possible variation in pineal function after 2 days, interruption of occupational ELF-MF exposure: again no exposure-related difference was observed. Our results do not support the hypothesis that occupational exposure to ELF-MF significantly influences melatonin secretion.

Issues concerning international comparison of free-field calibrations of acoustical standards

Primary free-field calibrations of laboratory standard microphones by the reciprocity method establish these microphones as reference standard devices for calibrating working standard microphones, other measuring microphones, and practical instruments such as sound level meters and personal sound exposure meters (noise dosimeters). These primary, secondary, and other calibrations are indispensable to the support of regulatory requirements, standards, and product characterization and quality control procedures important for industry, commerce, health, and safety. International Electrotechnical Commission (IEC) Technical Committee 29 Electroacoustics produces international documentary standards, including standards for primary and secondary free-field calibration and measurement procedures and their critically important application to practical instruments. This paper addresses some issues concerning calibrations, standards activities, and the international key comparison of primary free-field calibrations of IEC-type LS2 laboratory standard microphones that is being planned by the Consultative Committee for Acoustics, Ultrasound, and Vibration (CCAUV) of the International Committee for Weights and Measures (CIPM). This comparison will include free-field calibrations by the reciprocity method at participating major national metrology laboratories throughout the world.

Relative contribution of residential and occupational magnetic field exposure over twenty‐four hours among people living close to and far from a power line

This study sought to estimate the relative contribution of exposure to 50 Hz magnetic fields experienced at home, at work/school, or elsewhere to the total exposure over 24 hr. Personal exposure meters were carried by 97 adults and children in the Stockholm area. About half of the subjects lived close (<50 m) to a transmission line and half far (>100 m) away. Spot measurements and calculations for the residential exposure were also made. For subjects living<50 m from the line, the exposure at home contributed about 80% of the total magnetic field exposure, measured in mT-hours. Adults living far away experienced only 38% of the total exposure at home, but children still received 55%. Subjects with low time-weighted average (TWA) exposure both at home and at work spent 84% of their time in fields <0.1 microT, and those with high TWA at both locations spent 69% of their time in fields > or = 0.2 microT. This contrast was diluted if only exposure at one location was considered. For spot measurements and calculations of the residential exposure, both sensitivity and specificity was good. However, the intermediate field exposure category (0.1-0.19 microT) showed poor correlation to the 24 hr personal measurements.

Exposure to extremely low frequency magnetic fields among working women and homemakers

Given concerns with potential health effects of exposure to magnetic fields, the goal of this study was to examine the magnitude and sources of occupational and residential exposure to extremely low frequency (primarily 60 Hz) magnetic fields among women. Exposure to 60 Hz magnetic fields was surveyed among cases and controls recruited for a study of breast cancer in 25 counties in North Carolina. The 273 women who participated wore an integrating personal magnetic-field exposure meter (AMEX 3-D) that measured their time-weighted average (TWA) exposure. A questionnaire was administered to determine the duration and frequency of electric appliance and machinery use. The geometric mean (GM) of the TWA exposure for employed women was 0.138 μT (range 0.022–3.636 μT) and for homemakers 0.113 μT (range 0.022–0.403 μT). Women working in manufacturing and industrial facilities had the highest exposure (GM 0.265 μT, range 0.054–3.436 μT), while nurses and health technicians (GM 0.134 μT, range 0.032–0.285 μT) and teachers and school administrators (GM 0.099 μT, range 0.035–0.673 μT) had the lowest exposures. Job titles, unless very limited in scope and/or environment, self-reported information about equipment use, potential exposure sources, time, and distance were not good predictors of magnetic-field exposure. Furthermore, the results show that occupations previously observed to have increased risk of breast cancer, such as teachers, nurses, administrative support, and housewives, did not have elevated average magnetic field exposures. Therefore, it is questionable whether exposure to power frequency magnetic fields is the cause of the increased breast cancer risk seen in these occupations.

Importance of the free-field calibration of microphones

Numerous regulatory requirements, standards, and product characterization and quality control procedures important for industry, commerce, health, and safety rely on practical measuring instruments including sound level meters, personal sound exposure meters (noise dosimeters), and standardized measuring microphones. Such instruments are usually large enough that the effects of diffraction must be considered throughout a significant portion of the operating frequency range. These effects cause differences between the free-field, the pressure, and the diffuse-field sensitivities of instruments, particularly at high frequencies. Differences can also result from other phenomena, such as the effects of a microphone’s static (barometric) pressure equalization vent, especially at low frequencies. Different calibration procedures have evolved, so that an appropriate calibration is available for each of the field types: free, pressure, and diffuse. Critically important free-field procedures and some of the most accurate and widely used diffuse-field procedures should be, but are not always, traceable to primary free-field calibrations of microphones by the reciprocity method. Future international key comparisons at the highest level of accuracy should include determinations of the free-field sensitivities of laboratory standard microphones such as IEC type LS2 by the reciprocity method.

Comparison of Personal Exposure Meter Placement for the Determination of Office Worker ELF Magnetic Field Exposures

Comparison of Personal Exposure Meter Placement for the Determination of Office Worker ELF Magnetic Field Exposures

Extremely low frequency magnetic fields and fertility: a follow up study of couples planning first pregnancies. The Danish First Pregnancy Planner Study Team.

OBJECTIVES: To evaluate the impact of extremely low frequency (ELF) magnetic fields on markers of human fertility. METHODS: A follow up study of time to pregnancy, semen quality, and reproductive...

A DECADE OF IMPROVEMENT IN WHOLE-BODY VIBRATION AND LOW BACK PAIN FOR FREIGHT CONTAINER TRACTOR DRIVERS

The authors' study in 1983 revealed that the whole-body vibration of the tractor units of freight containers was most hazardous in the back-to-chest directions (x-axis). The allowable exposure time was considerably shorter than that for heavy duty trucks. The low back pain (LBP) among the drivers seemed to be due to the long working hours and the ergonomically unsound tractor design, as well as the vibration. A preventative measure was the introduction of a tractor cab suspended by an air spring instead of a steel spring. In 1992, a follow-up field study was conducted. A personal vibration exposure meter developed by us measured the whole-body vibration on eight tractors. Eighty-nine triplets matched with the age and the years of driving tractors answered a questionnaire evaluation of the ergonomics of their tractor units.The comparison of the newest steel suspension vehicles to the old ones produced by the same motor company revealed that in thex-axis the vibration level had decreased by as much as 4 to 9 dB. Some tractors showed an increase in vibration in the buttocks-to-head direction (z-axis). However, such adverse changes seemed not to affect evaluations according to the fatigue-decreased proficiency boundary (FDP) and the exposure limit (EL) recommended in ISO 2631–1978. The present models, regardless of the type of suspension, changed the direction of the most hazardous vibration from thex-axis to thez-axis. However, the effect of the air-suspension was not so remarkable as expected. Among 40% of drivers seemed to exceed the FDP boundary during a day.The questionnaire study showed an improvement in the ergonomic evaluation of the tractors. The air suspension models seemed to induce less LBP than the steel suspension models.

Sampling Design and Field Methods of a Large, Randomized, Multisite Survey of Occupational Magnetic Field Exposure

Abstract Large, randomized assessments of occupational exposure remain unusual in epidemiologic studies because of logistical barriers. Our study of workers in five U.S. electric companies requires estimates of full-shift time-weighted average (TWA) magnetic field exposure for 28 job groups, with the ability to separate within-worker and between-worker variability. Valid exposure assessment for this study is challenging because workers are dispersed over wide geographic areas. We used an innovative random monitoring strategy that may be useful in future studies. A target sample size of 4000 measurements was chosen based on considerations of precision and feasibility. Jobs were aggregated into three levels of presumed exposure. The number of measurements for each job was weighted such that the presumed medium-exposure and high-exposure groups were respectively sampled with three and five times the frequency of the low-exposure group, and measurements were distributed within these levels in proportion to the relative sizes of the five companies. Workers were selected randomly for monitoring: those in the two highest exposure levels were measured twice on random days. An easy-to-use integrating personal exposure meter was mailed to the selected workers, who wore it unsupervised for a full shift and then returned it. An employee at each company coordinated distribution of the meters and recorded data. After 11 months of full operation, 4259 monitoring attempts had been made on eligible workers, yielding 2885 usable measurements of 2196 workers. The low-exposure, medium-exposure, and high-exposure sampling groups had mean TWAs of 0.26, 0.53, and 1.02 μT, respectively. Appropriate instrumentation and assistance from workers and management facilitated this large randomized survey, despite substantial challenges. Loomis, D.P.; Kromhout, H.; Peipins, L.A.; Kleckner, R.C.; Iriye, R.; Savitz, D.A.: Sampling Design and Field Methods of a Large, Randomized, Multisite Survey of Occupational Magnetic Field Exposure. Appl. Occup. Environ. Med. 9(1):49–52; 1994.

Testing the response of personal noise exposure meters (noise dosimeters) to impulse-like signals using a laboratory reference noise dosimeter and a theoretical model (after ANSI S1.25-1978)

A laboratory reference noise dosimeter consisting of a measuring amplifier and instrument controller was assembled and characterized. A theoretical expression was obtained for the A-weighted, rms-detected output of a noise dosimeter assuming an input signal equal to that of a tone-burst sequence containing bursts comprised of an integral number of cycles of a sine wave. The output of the theoretical detector was numerically integrated to obtain percentage criterion exposure or time-weighted equivalent level. Equivalent levels were measured and calculated for each sequence in a set of tone-burst sequences with burst durations of 1 to 1000 cycles and crest factors of 4.8 to 30 dB. The agreement between equivalent levels obtained using the reference dosimeter and theoretical calculations was typically +0.1 dB. The results of these measurements and calculations were then used as a basis of comparison for testing the response of commercially available noise dosimeters to a subset of the tone-burst sequences. [Work supported by OSHA.]

Comparison of ANSI noise dosimeters and IEC personal sound exposure meters

ANSI and IEC have prepared draft standards on meters to measure workers sound exposure. The standards have a number of similarities. Both are based on IEC 804, integrating‐averaging sound level meters, and both are intended to specify meters worn on a worker and to measure noise throughout a work day. The ANSI draft specifies meters with exchange rates of 3, 4, or 5 dB, with a fast or slow time constant and a threshold. The IEC draft specifies only a 3‐dB exchange rate with no time constant or threshold. The ANSI draft specifies a read out in percent dose while the IEC draft is developed around Pascal squared hours. For continuous noise above the threshold, the reading can be converted from one set of units to the other. For intermittent and impulsive, a noise significant difference will occur.

ディスコ音楽聴取後の一過性聴力域値変動

The purposes of this experiment were to measure the sound intensity level in several discotheques and to compare the temporary threshold shift of subjects exposed to 60 minutes of discotheque sound at several intensity levels. We measured the sound intensity level with our own personal noise exposure meter.1. Sound intensity levels in 4 discotheques were ranged from 95dB (A) to 105.9dB (A).2. The largest TTS were 44dB at 4kHz for TTS2 and was found in the subjects, who were exposed to the intensity level of 107.0dB (A).3. It appears that the intensity level of 105dB is too high from the standpoint of the risk for hearing damage and that the level of 90dB does not satisfy audience.