American Industrial Hygiene Association journal最新文献

The adsorptive capacity of activated charcoal was determined experimentally for the vapors of 2-ethoxyethanol, pyridine, acetic acid, and piperidine from dry air and from air saturated with water vapor. Vapor concentrations ranged from 100 mg/m3 to at least 1000 mg/m3; the temperature was kept constant at 25 degrees C. The reduction in the adsorptive capacity of the activated charcoal by the relative humidity over the entire range of experimental conditions was accounted for by the Hansen-Fackler modification of the Dubinin-Radushkevich equation. This procedure allows the use of the activity coefficients, which are basic thermodynamic factors often available in the literature, to estimate the effect of adsorbed moisture on the adsorption of these organic compounds from a humidified atmosphere.

Three hundred thirty-eight noise exposure samples were collected from 133 construction workers employed in 4 construction trades: carpenters, laborers, ironworkers, and operating engineers. Four sites using a variety of construction techniques were sampled at least 12 times on a randomly chosen date over a 22-week period. Up to 10 volunteer workers were sampled for an entire work shift on each sampling day using datalogging noise dosimeters, which recorded both daily time-weighted averages (TWAs) and 1-min averages. Workers also completed a questionnaire throughout the workday detailing the tasks performed and tools used throughout the day. Regression models identified work characteristics associated with elevated exposure levels. Comparisons were made between exposures measured using the Occupational Safety and Health Administration (OSHA) exposure metric and the 1996 draft National Institute for Occupational Safety and Health/International Organization for Standardization (NIOSH/ISO) metric to examine the effects of differing exchange rates and instrument response times on construction noise exposures. The mean OSHA TWA for 338 samples was 82.8 dBA +/- 6.8 dBA, whereas the mean NIOSH/ISO TWA for 174 samples was 89.7 dBA +/- 6.0 dBA. Forty percent of OSHA TWAs exceeded 85 dBA, and 13% exceeded 90 dBA, the OSHA permissible exposure limit. The tasks and tools associated with the highest exposure levels were those involving pneumatically operated tools and heavy equipment. Trade was a poor predictor of noise exposure; construction method, stage of construction, and work tasks and tools used were found to be better exposure predictors. An internal validation substudy indicated excellent agreement between worker self-reporting and researcher observation. These data provide substantial documentation that construction workers in several key trades are frequently exposed to noise levels that have been associated with hearing loss, and demonstrate the need for targeted noise reduction efforts and comprehensive hearing conservation programs in the industry.

This study assessed the use of aural canal temperature measured with the Questemp II personal heat strain monitor (Tq) relative to rectal temperature (Tre) during simulated industrial work in three different wet bulb globe temperatures (WBGT). Sixteen subjects performed walking and arm curl exercise at a rate of 300 kcal/hour for 4 hours while wearing Saranex protective coveralls in 18, 23, and 27 degrees C WBGT environments and wearing the Questemp II. Correlations were determined between Tre and Tq for the three conditions and for all conditions combined. Pearson r values were 0.48 (18 degrees C WBGT), 0.42 (23 degrees C WBGT), 0.38 (27 degrees WBGT), and 0.50 (all trials). Because a major concern is safe maximum core body temperature, means and standard deviations for differences between Tre and Tq were assessed at peak temperatures to determine the predictability of Tre from Tq solely at these points. Large standard deviations in delta values relative to a small overall tolerable temperature range ruled out the use of Tq in this manner. Based on the current data, aural canal temperature as measured with the Questemp II did not provide an accurate reflection of Tre across time nor at peak core temperatures during low to moderate heat strain.

A dichotomous vapor/aerosol sampler was developed for measurement of HDI (1,6-hexamethylene diisocyanate)-derived total reactive isocyanate group (TRIG). The sampler consisted of an impactor or cyclone inlet, followed by an annular diffusional denuder, and a glass-fiber filter backup. The denuder walls and backup filter were each coated with 20 mg tributylphosphate and 1 mg MAMA reagent (9-N-methylamino-methylanthracene). After collection, MAMA-derivatized isocyanates were desorbed from the sampler and determined by high-performance liquid chromatography with dual-wavelength ultraviolet absorbance and fluorescence detection. Test atmospheres of HDI vapor and of HDI/HDI-biuret aerosols were generated in the laboratory and sampled with the optimized dichotomous sampler. Vapor phase HDI was completely collected by the diffusional denuder. When a mixture of HDI-biuret and HDI (approximately 30 ppb) was nebulized and collected with the dichotomous sampler, approximately 78% of the HDI was in the vapor phase, whereas about 22% was associated with the aerosol fraction. The dichotomous sampler was then used to measure vapor and condensed phase TRIG in a paint spray booth during application of a polyurethane paint. Measured levels of TRIG during the spraying operation averaged 391 +/- 154 micrograms/m3. Concentrations of HDI monomer averaged only 14 +/- 6.5 micrograms/m3. HDI-biuret was the largest component of TRIG found in these samples and was completely in the condensed aerosol phase. In contrast, the majority of the HDI was in the vapor phase, but significant (15-26%) amounts were measured in the aerosol fraction of the paint overspray. Thus, significant partitioning of HDI between vapor and condensed phases was demonstrated in both the laboratory and field, even when its concentration was well below the vapor saturation point.

Studies of worker heat stress and strain in aluminum smelters have found that heat exposure likely to exceed the American Conference of Governmental Industrial Hygienists' threshold limit value (TLV) and that the dose-response relationship between heat stress and strain was weak. A heat stress model based on climatic data and a task analysis indicated exposures to heat stress in excess of the TLV during the July/August study period. To study the impact of working above the TLV, heat strain data (i.e., oral temperature, recovery heart rate, average heart rate) were collected. Recovery heart rates indicated high strain most of the time, and oral temperatures after peak demands were above the no-strain threshold of 37.5 degrees C about a quarter of the time, indicating that heat stress had an effect. About 95% of the readings were below 38.0 degrees C, the acute oral temperature threshold for a safe exposure. Average heart rates over 6- and 12-hour intervals were generally below acceptable limits of 120 and 110 bpm, respectively. Oral temperature and average heart rates indicated good control of heat stress exposures. Because recovery heart rates were high, some employees were working near their individual limits. The dose-response relationship for recovery heart rate and oral temperature were examined against the level of heat stress above the TLV. There was no relationship between oral temperature and heat stress level. There was an apparent trend toward higher recovery heart rates with heat stress. The lack of a dose-response relationship may be explained by brief periods of very high wet bulb globe temperatures that drove the time-weighted average up out of proportion to the physiological response.

Workers at four different woodworking processes--two logging sites, four sawmills, one major woodchipping operation, and five joineries situated in the state of New South Wales in Australia--were studied for personal inhalable dust exposures (N = 182). The geometric mean exposure at logging sites was 0.6 mg/m3 (N = 7), sawmills 1.6 mg/m3 (N = 93), woodchipping 1.9 mg/m3 (N = 9), and joineries 3.7 mg/m3 (N = 66). Overall, 62% of the exposures exceeded the current standards. Among joineries, 95% of the hardwood exposures and 35% of the softwood exposures were above the relevant standards. A majority of workers (approximately 90%) did not wear appropriate respirators approved for wood dust, while the ones who did wear them, used them on average less than 50% of the time. The significant determinants of personal wood dust exposures (n = 163) were found to be local exhaust ventilation, job title, use of handheld tools, cleaning method used, use of compressed air, and green or dry wood processed. Type of wood processed (softwood or hardwood) was not found to be statistically significant.

Published reports to assess incidents in hazardous waste operations are scarce. This study was designed to evaluate incident trends in a relatively large hazardous waste cleanup company. The data for 6.5 years, winter 1990 through spring 1996, provided 1848 incident reports with 87% involving injury/illness cases. Over 75% of injury/illness incidents were due to mechanical agents, 10% occurred because of chemical exposure, 5% involved poisonous plants and insect bites, 2% resulted from temperature extremes, 1% were from cumulative injuries/illnesses, and in 7% the agent was not recorded. Almost 31% of injuries were related to the upper extremities, with the fingers most often injured, followed by the hands. Lower back strain cases constituted 11% of injuries, ankle/foot/toe cases 9%, and knee cases 5%. Recovery technicians (laborers) had the highest frequency of injury/illness incidents (52%), followed by supervisors (15%) and heavy machinery operators (10%). The incidence rates (IRs) for all recordable incidents ranged from 11.9 for the second quarter of 1990 down to 1.2 for the fourth quarter of 1995 with a mean (SD) and median of 6.3 (3.0) and 6.1, respectively. For the time period studied, IRs decreased significantly (p < 0.01). It was concluded that hands-on experience in the field and improvements in the health and safety program of the company--including expanding its focus (originally the prevention of chemical exposure) to include construction safety--reduced the incidents considerably. Introduction of new regulations has also contributed to this trend.

During July 1995 the National Institute for Occupational Safety and Health (NIOSH) began to certify nine new classes of particulate respirators. To determine the level of performance of these respirators, NIOSH researchers conducted a study to (1) measure the simulated workplace performance of 21 N95 respirator models, (2) determine whether fit-testing affected the performance, and (3) investigate the effect of varying fit-test pass/fail criteria on respirator performance. The performance of each respirator model was measured by conducting 100 total penetration tests. The performance of each respirator model was then estimated by determining the 95th percentile of the total penetration through the respirator (i.e., 95% of wearers of that respirator can expect to have a total penetration value below the 95th percentile penetration value). The 95th percentile of total penetrations for each respirator without fit-testing ranged from 6 to 88%. The 95th percentile of total penetrations for all the respirators combined was 33%, which exceeds the amount of total penetration (10%) normally expected of a half-mask respirator. When a surrogate fit test (1% criterion) was applied to the data, the 95th percentile of total penetrations for each respirator decreased to 1 to 16%. The 95th percentile of total penetrations for all the respirators combined was only 4%. Therefore, fit-testing of N95 respirators is necessary to ensure that the user receives the expected level of protection. The study also found that respirator performance was dependent on the value of the pass/fail criterion used in the surrogate fit-test.

Following the diagnosis of two cases of occupational asthma among dental technicians, an industrial hygiene survey was conducted in two dental laboratories to determine time-weighted average and peak concentrations of methyl methacrylate vapor and time-weighted average concentration of acrylic dust. The time-weighted average concentrations of methyl methacrylate vapor were 0.7 ppm and 1.6 ppm and average peak concentrations were 9.3 ppm and 9.7 ppm for the first and second laboratory, respectively. The use of a local exhaust ventilation system was significant in reducing the peak concentration of methyl methacrylate vapor in the breathing zone of dental technicians. However, the local exhaust ventilation was not efficient in reducing the concentration of airborne acrylic dusts. Occupational exposure of dental technicians to dental materials, in particular to methyl methacrylate, requires further investigation. Local exhaust ventilation systems can reduce the concentration of methyl methacrylate in the dental laboratories to a significant extent if installed and used properly.

This article compares extremely low frequency (ELF) magnetic field exposures measured by placing EMDEX Lite personal exposure meters (PEMs) at the head, chest, and waist level for a group of office workers. Twenty-three volunteers were solicited to wear three PEMs simultaneously; one was attached to a baseball cap worn on the head, one was attached to a band and worn around the neck (positioned on the chest), and one was worn in a belted pouch around the waist (positioned on the right side of the hip). The effect of PEM placement was evaluated by comparing full-shift average exposures and daily maximum or peak exposure. The results of this investigation indicate that time-weighted average magnetic field exposures determined at the hip provide the highest mean exposure estimates. Averages of the full-shift mean magnetic field measurements taken at hip and head levels were statistically greater than measurements taken at the chest level by 33 and 22%, respectively. Comparisons of the maximum or peak magnetic field exposures by body position indicate that the hip position produced an average exposure estimate that was 136% greater than the average head-level measurement. Results suggest that for office workers PEM meter placement on the body does not produce large differences in full-shift average ELF magnetic flux density exposures. However, the hip position produced the largest daily maximum or peak exposures. It is recommended that PEMs be placed on the hip for exposure assessments in office environments, because this placement is the most commonly used, the most convenient, and resulted in the highest magnetic field exposures.