American Industrial Hygiene Association journal最新文献

Measurements of extremely low frequency electromagnetic fields and low frequency magnetic fields emitted by a set of video display terminal (VDT) units are reported. The field values measured at the position normally occupied by the user are below the safety limits. This is because the field amplitudes decrease rapidly (following a 1/R3 law) with the distance from the source, as has been verified in this work. Measurements with a commercial shielding device consisting of small plastic balls filled with a water solution of rare earth elements were also performed. The only physical mechanism that could be hypothesized to produce an active suppression of the VDT field is that rare earth atoms, which probably were chosen due to their large magnetic moment, behave as oscillating magnetic dipoles capable of emitting a secondary magnetic field that, along some particular directions, has a phase that is opposite to that of the exciting field. Unfortunately, if one analyzes this mechanism quantitatively, it is easy to show that the secondary magnetic field is absolutely negligible, as was confirmed by experimental measurements performed in this study.

Health-related monitoring of bioaerosol exposures in the workplace should ideally be carried out using size-selective personal samplers that separate the aerosol into biologically relevant size fractions and allow both quantification and identification of the microorganisms present in each fraction. As a first stage in the development of personal bioaerosol samplers a number of collection substrates were assessed for their ability to maintain the viability of the collected microorganisms, so that subsequent culturing and species identification may be carried out. The substrates were tested with bioaerosols of varying robustness, consisting of Saccharomyces cerevisiae cells, Escherichia coli cells, and Penicillium expansum spores, aerosolized under controlled environmental conditions. The survival of microorganisms on each test substrate, assessed on the basis of the culturable fractions of cells recovered, was compared with that of microorganisms collected in a reference glass cyclone sampler. These bioefficiency tests identified the substrate combinations with the potential to fulfill personal sampler design criteria. The substrates were then subjected to further development to evaluate and optimize their particle size selection characteristics. The outcome of this work is two prototype personal bioaerosol samplers in which size-selective substrates are adapted for use in existing designs of personal inhalable sampler. This offers an effective and low-cost solution to personal monitoring of bioaerosol exposures in the workplace.

Exposure to rosin during a variety of uses has been associated with dermal and pulmonary sensitization. Oxidized resin acids are present in many rosin products, and have been regarded as the main sensitizing rosin compounds in cases of dermal sensitization. This research describes oxidized resin acids identified in aerosol produced during soldering with rosin core solder. Oxidized resin acids found were 7-oxodehydroabietic acid, 15-hydroxydehydroabietic acid, and 7-hydroxydehydroabietic acid. The presence of oxidized compounds known to be dermal sensitizers in aerosol from rosin flux soldering supports the hypothesis that resin acid compounds are pulmonary sensitizers as previously proposed. Changes in the composition of resin acid aerosol derived from heated rosin core solder (compared with the parent material) are described.

The health and safety programs that support academic and research institutions face many challenges because of the wide variety of potential hazards present and the possibility of simultaneous exposures to several agents. This study investigated whether differences in health and safety programs exist between minority and nonminority state-funded academic and research institutions. A cross-sectional mail survey was conducted that included 24 minority and 51 nonminority schools. Questionnaires solicited information on descriptive institutional parameters, health and safety staffing, the hazards present, programs in place to address hazards, and medical surveillance services. The hazard types identified as present on both campus types were found to be very similar. The mean number of health and safety staff serving minority institutions was lower (1.14 versus 3.12), with the difference reliably predicted by the number of institutional employees, not minority status or regulatory environment. Other targeted parameters were found to be similar, with a consistent lack of awareness of specific medical evaluations noted for both groups. Since on average a single person is charged with controlling a diverse set of potential hazards on the minority campuses studied, the need for a comprehensive awareness of a variety of health and safety issues is discussed.

Quantitative fit tests (QNFT) have been assumed to be predictive of the protection respirators would provide to a wearer in the workplace. Workplace studies have consistently found no correlation between quantitative fit factors and workplace protection factors. This article is the first in a series of three describing a study designed to compare the fit factors from six QNFT methods against the actual dose of 1,1,2 trichloro-1,2,2 trifluoroethane (Freon-113) received under the same laboratory conditions. Five preliminary studies conducted to develop the protocol to assess the respirator wearer's dose through end-exhaled air analysis are described in this article: (1) chamber characterization, (2) end-exhaled air sampling, (3) skin absorption testing, (4) pharmacokinetic modeling, and (5) subject characterization. It was established that the concentration of corn oil aerosol and Freon-113 could be generated simultaneously in the chamber. It was ascertained that the optimum time to sample the exhaled breath was 30 minutes after the subject exited the chamber. It was also found that in a chamber concentration of 500 ppm, without any respiratory exposure, Freon-113 was still present in the end-exhaled air. This was attributed to skin absorption. The end-exhaled air of subjects exposed to 0.5, 3, 5, 25, 50, and 100 ppm (30 minute time-weighted average) of Freon-113 was evaluated at 30 minutes postexposure. This characterization was then used to predict the actual dose of Freon-113 received during the method comparison and validation testing to be described in subsequent articles.

Assessment of the physical demands of potentially hazardous manual material handling (MMH) activities is fundamental to the prevention of disabilities from occupationally related low back pain, a problem costing the nation billions of dollars annually. Although there is a variety of ergonomic assessment methods available for assessing MMH activities, there is a lack of practical information to assist users in choosing the most appropriate assessment methods of a particular job. This article reviews currently available assessment methods and presents case study results of a physically demanding repetitive manual lifting job in two grocery warehouses. The case study will provide a framework for a comparison of the methods and a discussion of relevant application issues designed to assist users in selecting appropriate methods for assessing MMH jobs. Based on the results of the study, it is concluded that all of the ergonomic methods were in agreement that the job of grocery selector has a high level of risk for low back pain. Differences between the methods were noted, however, that should be considered when choosing a specific method for a specific application.

This article, the second in a series of three, describes the method comparison testing portion of a study conducted to compare the fit factors from six quantitative fit-tests (QNFT) with a measure of a respirator wearer's actual exposure assessed by end-exhaled air analysis for 1,1,2-trichloro-1,2,2-trifluoroethane (Freon-113) under the same conditions. The six QNFT methods were (1) continuous low flow, flush probe; (2) continuous high flow, deep probe (CHD); (3) exhalation valve discharge (EVD); (4) controlled negative pressure; (5) 10-minute Ambient Aerosol 1 (AA1); and (6) 30-minute Ambient Aerosol 2. The first three methods utilized corn oil and a forward light scattering photometer. The last two methods used the TSI Portacount. Respirators used in the study were both disposable and elastomeric organic vapor/high efficiency half-masks. The characterization equations from the preliminary research (described previously) were used to determine the actual exposure to Freon-113 during the method comparison testing. The fit factors resulting from the QNFT methods were then individually correlated with the Freon-113 exposures using the coefficient of determination, R2. The lowest R2 value, 0.20, was found with the EVD method. The highest R2 values, 0.81 and 0.78, were associated, respectively, with the CHD and AA1 methods. This study suggests that some QNFT methods may be used to estimate actual respirator performance under laboratory conditions.

It is very important to provide an accurate estimate for the mean value of lognormal distributed occupational exposures. Four commonly used methods for estimating a lognormal mean are the sample mean, the maximum likelihood estimate (MLE), a bias-corrected MLE, and the minimum variance unbiased estimator (MVUE). In this article the explicit expressions are given for the mean square errors of these four estimators, and performances of these four estimators are compared in terms of their mean square errors. This article reaffirms the conclusion of earlier researchers that the MVUE is uniformly superior to the other three estimators.

Workplace aerosols must be sampled to assess the degree of health hazard caused by the particulate matter. By adjusting the sampling flow rate, most of the samplers can match the 50% cutoff size, but not the slope of the respirable convention defined by the American Conference of Governmental Industrial Hygienists, the International Organization for Standardization, and the European Committee for Standardization (CEN). Combinations of foams (or other porous material) of different nominal sizes (10-100 ppi) and thicknesses (5-35 mm) were employed to overcome this bias. A foam disk 25 mm in diameter was placed in an asbestos sampling cowl. Dioctylphthalate was the liquid test agent. An aerodynamic particle sizer and an Aerosizer were calibrated against a settling chamber and were employed to measure the aerosol number concentrations and size distributions upstream and downstream of the foams. The sampling efficiency data showed that the 50% cutoff size could be met for foams in series, but that the slope remained sharper than the new definition. Foams in parallel showed great flexibility and many of the parallel combinations flattened the slope, closer to that of the new international respirable convention. For instance, when the total flow rate is set at 10.1 L/min the aerosol penetration through foams in parallel (100 ppi, 20 mm thick, diameter 25 mm + 10 ppi, 20 mm thick, diameter 13 mm) nearly matched the new international standard for respirable fraction. This sampler can be further miniaturized for smaller sampling flow rates to fit the capacity of personal sampling pumps.

This study, conducted in 1987 and 1988, has made it possible to quantify exposure to noise among heavy equipment operators, associated laborers, and crane operators. The average daily noise exposure was 84 to 99 dBA for heavy equipment, 90 dBA for the laborer, and 74 to 97 dBA for the crane operator. The main sources of noise to which heavy equipment operators are exposed are vehicle engines and the muffler exhaust system, usually located near the operator. The presence of insulated cabs such as those found on power shovels, backhoes, wheel loaders, and graders help reduce noise exposure. The type of tasks carried out by the laborers, the sources of noise from heavy equipment around which they work, and the manual equipment they use determine the noise levels to which such workers are exposed. In the case of crane operators, an insulated cab significantly reduces the operator's exposure to engine noise.