TLD occupational dose distribution study in nuclear medicine

The large and growing number of patients undergoing nuclear medicine procedures and workers involved in this practice requires continued efforts to improve the quality of diagnosis and to reduce the radiological risk associated. In Brazil, external individual monitoring with a dosemeter located on the thorax is compulsory for all workers in controlled areas. Extremity dosemeters are recommended in activities where hand dose can be much higher than on the thorax. This is typically the case for nuclear medicine procedures, but extremity dosemeters are not regularly used in Brazil. With the aim to study the occupational dose distribution in the nuclear medicine staff during their tasks of preparation and injection of radionuclides, Harshaw TLD chips of LiF:Mg,Cu,P (TLD-100H) were used for individual monitoring on different parts of the worker body. As expected, all doses measured on the thorax were much lower than on the hands. For both Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET), the dose to the fingers during preparation is about two orders of magnitude higher than in the thorax, and in the injection procedure, one order higher. The doses received by the workers' fingers varied widely depending on how they hold the syringe, but fingertips always received higher doses. The dose values measured in the eye lens were 200% higher than the one measured on the thorax.     

A suppressor for indoor shooting sites

Shootings at test shooting sites indoors can cause a risk of hearing loss for the workers at the site. The noise can also disturb other persons working in nearby rooms in the same building. A simple suppressor was constructed from a ventilation sound absorber. Sound level meters were installed near the shooter, to his side and in front of him, and in two nearby rooms. The suppressor solution attenuated the peak noise level to the side by 14–18 dB. Near the ear of the shooter, the amplification was 1–4 dB due to reflections. Therefore, a suppressor should have an adjustment mat between the muzzle of the weapon and the suppressor that would isolate sound from the muzzle backwards. In front of the shooter, the peak levels were attenuated by 0–3 dB due to the suppressor system. The suppressor system attenuated noise best to the side. The opening between the muzzle and the suppressor system caused the attenuation at the back of the weapon to be modest. In front, the bullet flight noise remained, and as a result there was no significant noise reduction in this direction. More noise control work is still needed, and one possibility for improvement would be a better enclosure of the imminent shooting area.     

Distribution of risk factors for hearing loss: implications for evaluating risk of occupational noise-induced hearing loss

This paper presents an analysis of hearing threshold levels among 2066 white male workers employed in various U.S. industries studied in the 1968-72 NIOSH Occupational Noise and Hearing Survey (ONHS). The distribution of hearing threshold levels (HTL) is examined in relation to various risk factors (age, prior occupational noise, medical conditions) for hearing loss among a population of noise exposed and control (low noise-exposed) industrial workers. Previous analyses of a subset of these data from the ONHS focused on 1172 highly "screened" workers. An additional 894 male workers (609 noise-exposed and 285 controls), who were excluded for various reasons (i.e., nonoccupational noise exposure, otologic or medical conditions affecting hearing, prior occupational noise exposure) have been added to examine hearing loss in an unscreened population. Data are analyzed by age, duration of exposure, and sound level (8-h TWA) by individual test frequency. Results indicate that hearing threshold levels are higher among unscreened noise-exposed and control workers relative to screened workers. Analysis of risk factors such as nonoccupational noise exposure, medical conditions, and type of industry among unscreened controls indicated that these factors were not significantly associated with increased mean HTLs or risk of material impairment over and above what is expected due to age. Age-specific mean hearing threshold levels (and percentiles of the distribution) among the unscreened ONHS control population may be used as a comparison population of low-noise exposed white male industrial workers for evaluating the effectiveness of hearing conservation programs for workers less than 55 years of age. To make valid inferences regarding occupational noise-induced hearing loss, it is important to use hearing data from reference (control) populations that are similar with respect to the degree of subject screening, type of work force (blue vs white collar), and the distribution of other risk factors for hearing loss.     

Block copolymers for the synthesis of pure and Bi-promoted nano-TiO2 as active photocatalysts

The aim of this study was to establish and identify the health effect markers of workers with potential exposure to nanoparticles (20?C100?nm) during manufacturing and/or application of nanomaterials. For this cross-sectional study, we recruited 227 workers who handled nanomaterials and 137 workers for comparison who did not from 14 plants in Taiwan. A questionnaire was used to collect data on exposure status, demographics, and potential confounders. The health effect markers were measured in the medical laboratory. Control banding from the Nanotool Risk Level Matrix was used to categorize the exposure risk levels of the workers. The results showed that the antioxidant enzyme, superoxide dismutase (SOD) in risk level 1 (RL1) and risk level 2 (RL2) workers was significantly (p?<?0.05) lower than in control workers. A significantly decreasing gradient was found for SOD (control?>?RL1?>?RL2). Another antioxidant, glutathione peroxidase (GPX), was significantly lower only in RL1 workers than in the control workers. The cardiovascular markers, fibrinogen and ICAM (intercellular adhesion molecule), were significantly higher in RL2 workers than in controls and a significant dose?Cresponse with an increasing trend was found for these two cardiovascular markers. Another cardiovascular marker, interleukin-6, was significantly increased among RL1 workers, but not among RL2 workers. The accuracy rate for remembering 7-digits and reciting them backwards was significantly lower in RL2 workers (OR?=?0.48) than in controls and a significantly reversed gradient was also found for the correct rate of backward memory (OR?=?0.90 for RL1, OR?=?0.48 for RL2, p?<?0.05 in test for trend). Depression of antioxidant enzymes and increased expression of cardiovascular markers were found among workers handling nanomaterials. Antioxidant enzymes, such as SOD and GPX, and cardiovascular markers, such as fibrinogen, ICAM, and interluekin-6, are possible biomarkers for medical surveillance of workers handling engineered nanomaterials.     

Radiation background due to radioactive sources in a luminescence dating laboratory

For practical reasons, usually, luminescence dating laboratories contain in the same room (or in adjacent rooms) the equipment and the radioactive sources, as well as the storage cabinet for the samples. It is generally assumed that the absorbed dose due to ambient radioactivity is null or at least negligible in terms of human health (below the dose limit).To test the actual dose rate inside our laboratory room, an investigation combining portable dose rate meter, portable NaI(Tl) gamma spectrometry, and blue-OSL dosimetry using Al₂O₃:C pellets was made. Although our measurements show the presence of X-rays as far as 3 m from the sources, the dose rates are below the safety regulation and does not affect the dating of the sample stored in the same room as the radioactive sources.     

Improving the acoustic working conditions for musicians in small spaces

In the acoustic consulting, testing, design and engineering work of the Fraunhofer-Institute of Building Physics (IBP) the low-frequency end of the noise spectra and the room acoustic conditioning has gained tremendous importance over the years. For solving the long-ranging noise pollution from e.g. exhaust stacks and chimneys, a series of low-frequency sound attenuators with minimum flow resistance were developed. Its first representative was a novel membrane absorber [10] [Ackermann U, et al., Sound absorbers of a novel membrane construction. Applied Acoustics 1998;25:197-215]. Thanks to its slenderness and ruggedness it could also be employed for noise control and reverberation adjustment purposes in relatively narrow enclosures and harsh environments [11] and [12] [Vér IL. Enclosures and wrappings. In: Harris CM, editor. Handbook of acoustical measurements and noise control. New York: McGraw-Hill, 1991; Fuchs HV, Hunecke J. The room plays its part at low frequencies. Das Musikinstrument 1993;42:40-6 (in German). Meanwhile a new type of panel absorber has been optimized for both kinds of application. Its absorption efficiency at frequencies far below 100 Hz could be demonstrated and quantified by a special measuring procedure based on the reverberation of a small rectangular room at its eigenfrequencies [3] (Zha X, et al. Measurements of an effective absorption coefficient below 100 Hz. Acoustics Bulletin 1999;24:5-10). With the aid of this novel tool it is now possible to qualify reverberation rooms and anechoic chambers for frequencies down to 63 and 31 Hz, respectively [9] (Fuchs HV, et al. Qualifying freefield and reverberation rooms for frequencies below 100 Hz. Applied Acoustics 2000;59:303-22). In a companion paper in this same journal [4] [Fuchs HV, et al.: Creating low-noise environments in communication rooms. Applied Acoustics (in print)] appropriate experience is reported in creating low-noise environments in multi-purpose rooms like offices, restaurants, foyers and seminars. A number of representative case studies [5] (Drotleff H, et al. : Attractive acoustic design of multi-purpose halls. 1. Chinese-German Platform Innovative Acoustics 2000, (October, 21-25. 2000)) show ample evidence that the low-frequency performance of the rooms has a strong influence on both the amplification of intruding external noise and the development of internally generated noise emanating from communication processes provoked by the users themselves. At work places where producing sound (by voices or/and instruments) is the main or only purpose for their existence, the acoustic qualification of the room at low frequencies turns out to be of the utmost importance, especially when musicians are forced to work in extremely narrow spaces like orchestra pits and rehearsal halls for many hours a day and often under extreme physical and mental pressure. The measures taken and described herein have proven to mitigate if not remove some of the acoustic burden put on musicians employed in states theatres.     

Binaural active noise control using parametric array loudspeakers

This paper reports the binaural active noise control (ANC) system developed to deal with factory noise. The control points are located in the vicinity of the left and right ears of a worker sitting along the production line. Due to the complicated safety requirements in the factory, secondary sources and error microphones are not allowed to be placed near the worker. Therefore, the proposed ANC system employs the feedforward structure and adopts the parametric array loudspeakers (PALs) as the secondary sources. The PAL is a type of directional loudspeaker that generates a much narrower sound field as compared to the conventional loudspeaker. Once the proposed ANC system has been trained offline, the error microphones can be removed. The performance of the binaural ANC system is successfully demonstrated based on a digital signal processor (DSP) implementation.     

Comparison of different experimental methods for the assessment of the room’s acoustics

The paper presents the acoustics analysis of three different enclosed spaces. These spaces (rooms) have different geometrical shapes and sizes and serve for different purposes. The early decay time, reverberation time, clarity and center time are evaluated with Dirac, WinMLS, Aurora and Caracad software using simple, low-cost equipment. The listed acoustic parameters were determined using linear sine sweep and impulsive sources. Comparisons between experimental measurements, simulations and analytic results were done. The room impulse response measurement proved to be the most reliable method to evaluate the properties of different rooms even if the measurements are perturbed by non-idealities of the low-cost equipment.     

Testing the accuracy of smartphones and sound level meter applications for measuring environmental noise

This paper reports on experimental tests undertaken to assess the capability of noise monitoring applications to be utilized as an alternative low cost solution to traditional noise monitoring using a sound level meter. The methodology consisted of testing 100 smartphones in a reverberation room. Broadband white noise was utilized to test the ability of smartphones to measure noise at background, 50, 70 and 90 dB(A) and these measurements were compared with true noise levels acquired via a calibrated sound level meter. Tests were conducted on phones using the Android and iOS platforms. For each smartphone, tests were completed separately for leading noise monitoring apps culminating in 1472 tests. The results suggest that apps written for the iOS platform are superior to those running on the Android platform. They show that one of the apps tested – SLA Lite – is within ±1 dB of true noise levels across four different reference conditions. The results also show that there is a significant relationship between phone age and its ability to measure noise accurately. The research has implications for the future use of smartphones as low cost monitoring and assessment devices for environmental noise.     

Determination of the sound energy level of a gunshot and its applications in room acoustics

In some cases an impulsive noise source such as a gunshot can be a preferred alternative when investigating building acoustics, including sound insulation measurements, when compared to conventional steady state noise sources. A gun equipped with blank cartridges is an impulsive noise source that is lightweight and small enough to be easily transported. The differences in the noise characteristics between individual cartridges for the same gun are usually small, so the impulsive source can be replicated to a high degree. This paper is focused on the practical application of the sound exposure levels produced by a gunshot with a known sound energy level in the rooms under investigation. In this way, the equipment and methods required by the conventional method are simplified significantly. Furthermore, reverberation times need not be measured, since the equivalent absorption area can be directly obtained from the measured sound exposure levels. Using Green’s theorem, the roles of the sound source and measuring microphone were exchanged, which simplified the determination of sound insulation as it was easier to change the position of the gun than the microphone. The results obtained using the impulsive noise source were in good agreement with those obtained using the conventional method. Above 100 Hz, their difference in any frequency band of interest was less than 1 dB.     

Industrial noise levels and annoyance in Egypt

Annoyance and increase of accident risk of workers from industrial noise levels in Egypt were studied. 683 workers from 15 Egyptian sites of industry, ranging from food to metal industry were evaluated. The goals of this study are to carry out measurements to evaluate industrial noise levels, are these levels exceeded the permissible levels set by Egyptian noise standard and policy to protect public health of workers?, to examine worker’s attitudes towards industrial noise, to know the relationship between industrial noise levels and degree of annoyance. Results showed that equivalent continuous noise levels ranged from 70 to 100 dB (A). Annoyance of respondents showed that 47.1% were highly annoyed, 5.8% their hearing were harmed. There was a strong relationship between industrial noise levels and percentage of highly annoyed respondents. By increasing industrial noise level possibility of workers to make accident was also increased. Respondents suggest less maximum daily exposure duration than those set by Egyptian law.     

Localization of distinct reflections in rooms using spherical microphone array eigenbeam processing

This paper presents an experimental and comparative study of several spherical microphone array eigenbeam (EB) processing techniques for localization of early reflections in room acoustic environments, which is a relevant research topic in both audio signal processing and room acoustics. This paper focuses on steered beamformer-based and subspace-based localization techniques implemented in the spherical EB domain, including the plane-wave decomposition, eigenbeam delay and sum, eigenbeam minimum variance distortionless response, eigenbeam multiple signal classification (EB-MUSIC), and eigenbeam estimation of signal parameters via rotational invariance techniques (EB-ESPRIT) methods. The directions of arrival of the original sound source and the associated reflection signals in acoustic environments are estimated from acoustic maps of the rooms, which are obtained using a spherical microphone array. The EB-domain-based frequency smoothing and white noise gain control techniques are derived and employed to improve the performance and robustness of reflection localization. The applicability of the presented methods in practice is confirmed by experiments carried out in real rooms.     

Household appliance noise

Noise spectra of eighteen commonly-used household appliances are given, up to ten models of each type being studied. Measurements were taken in acoustically-simulated average domestic rooms and in situ.The present paper is confined to a study of appliance noise levels over which the user can exercise little or no direct control. This excludes televisions, radios and record players, which are regulated by the user.The noisiest room in the house is normally the kitchen, with appliance noise levels ranging from about 40 to 90 dB(A). Living-room appliances are much quieter, heating devices ranging between about 35 and 50 dB(A). Appliances used in the bathroom are not generally as noisy as those used in the kitchen, but require some redesign to reduce the noise to more acceptable levels.     

Localization of sound in rooms. V. Binaural coherence and human sensitivity to interaural time differences in noise

Binaural recordings of noise in rooms were used to determine the relationship between binaural coherence and the effectiveness of the interaural time difference (ITD) as a cue for human sound localization. Experiments showed a strong, monotonic relationship between the coherence and a listener's ability to discriminate values of ITD. The relationship was found to be independent of other, widely varying acoustical properties of the rooms. However, the relationship varied dramatically with noise band center frequency. The ability to discriminate small ITD changes was greatest for a mid-frequency band. To achieve sensitivity comparable to mid-band, the binaural coherence had to be much larger at high frequency, where waveform ITD cues are imperceptible, and also at low frequency, where the binaural coherence in a room is necessarily large. Rivalry experiments with opposing interaural level differences (ILDs) found that the trading ratio between ITD and ILD increasingly favored the ILD as coherence decreased, suggesting that the perceptual weight of the ITD is decreased by increased reflections in rooms.     

Interior noise control with an active window system

An active window system to reduce the exterior noise sources, such as traffic noise and construction noise which enter rooms through open windows used for natural ventilation is proposed. The proposed system uses a feedforward control method for active noise control so as not to place the sensors and control sources inside the interior space of the building. For global noise reduction throughout the interior room, the control gains for feedforward control are calculated to minimize the total acoustic power of the new source, which is combined with the noise source corresponding to the open window and control sources on the window frame. The performance of the proposed system for directional exterior noise is confirmed with a scale-model experiment. The experimental results show that the proposed system can achieve a noise reduction of up to 10 dB for the entire room of the scale model regardless of the direction of the incident wave.     

Taking stock of the occupational safety and health challenges of nanotechnology: 2000–2015

Engineered nanomaterials significantly entered commerce at the beginning of the 21st century. Concerns about serious potential health effects of nanomaterials were widespread. Now, approximately 15 years later, it is worthwhile to take stock of research and efforts to protect nanomaterial workers from potential risks of adverse health effects. This article provides and examines timelines for major functional areas (toxicology, metrology, exposure assessment, engineering controls and personal protective equipment, risk assessment, risk management, medical surveillance, and epidemiology) to identify significant contributions to worker safety and health. The occupational safety and health field has responded effectively to identify gaps in knowledge and practice, but further research is warranted and is described. There is now a greater, if imperfect, understanding of the mechanisms underlying nanoparticle toxicology, hazards to workers, and appropriate controls for nanomaterials, but unified analytical standards and exposure characterization methods are still lacking. The development of control-banding and similar strategies has compensated for incomplete data on exposure and risk, but it is unknown how widely such approaches are being adopted. Although the importance of epidemiologic studies and medical surveillance is recognized, implementation has been slowed by logistical issues. Responsible development of nanotechnology requires protection of workers at all stages of the technological life cycle. In each of the functional areas assessed, progress has been made, but more is required.     

On the efficacy of spatial sampling using manual scanning paths to determine the spatial average sound pressure level in rooms

In architectural acoustics, noise control and environmental noise, there are often steady-state signals for which it is necessary to measure the spatial average, sound pressure level inside rooms. This requires using fixed microphone positions, mechanical scanning devices, or manual scanning. In comparison with mechanical scanning devices, the human body allows manual scanning to trace out complex geometrical paths in three-dimensional space. To determine the efficacy of manual scanning paths in terms of an equivalent number of uncorrelated samples, an analytical approach is solved numerically. The benchmark used to assess these paths is a minimum of five uncorrelated fixed microphone positions at frequencies above 200 Hz. For paths involving an operator walking across the room, potential problems exist with walking noise and non-uniform scanning speeds. Hence, paths are considered based on a fixed standing position or rotation of the body about a fixed point. In empty rooms, it is shown that a circle, helix, or cylindrical-type path satisfy the benchmark requirement with the latter two paths being highly efficient at generating large number of uncorrelated samples. In furnished rooms where there is limited space for the operator to move, an efficient path comprises three semicircles with 45°-60° separations.     

Dose assessment in the criticality accident at Tokai-mura

The present paper reviews a dose assessment carried out after the criticality accident that occurred on September 30, 1999 at JCO in Tokai-mura, Japan. In the accident, almost all doses were caused by external exposure to neutrons and γ-rays emitted upon the fission of uranium. By a joint effort of Japanese experts in radiation dosimetry, a dose assessment was performed for neighboring residents, JCO employees including 3 workers who were at the accident spot, and emergency response personnel. The dose assessment was carried out using records of dosimeters, radiation monitoring data in and around the site, analysis of biological specimens, and computer simulation techniques. It was concluded from the results of the dose assessment that deterministic effects are not expected, except for the 3 heavily exposed workers, and that the probability of stochastic effects is very small and will be undetectable.     

Risk factors for hearing loss at different frequencies in a population of 47,388 noise-exposed workers.

Weighted regression analysis was applied to determine the dependence of the hearing thresholds of 47,388 noise-exposed workers on age, sex, noise immission level, ear disease, head injury, tinnitus, hearing protector usage, and audiometric frequency in the range from 0.5 to 6 kHz. It could be shown that the hearing thresholds at any frequency are dominated by the age of the worker and that women, after equivalent exposure conditions, hear better than men. The relative effects of sex, noise immission level, ear diseases, tinnitus, and hearing protector usage are related to the audiometric frequency. Users of hearing protectors at the last audiometric investigation hear worse than nonusers. Hearing protector usage is strongly related with the hearing threshold in the low-frequency range. The noise immission level does not noticeably affect the hearing threshold below 3 kHz. The most important frequency of the noise immission level is as expected 4 kHz. For 4 kHz, it was shown that the variables age, noise immission level, tinnitus, head injuries, and ear diseases act in a good approximation additively on the pure-tone hearing threshold.