American Industrial Hygiene Association journal最新文献

A survey of workplace exposures to 60-Hz magnetic fields was carried out at a large uranium enrichment facility to assign exposures for an updated mortality study. Stratified random selection was used to choose workers for measurement in all jobs and areas, to determine whether consistent distinctions could be made between job groups based on average magnetic field exposures. A total of 252 workdays was measured with a personal monitor, and individual average magnetic field exposures ranged from 0.20 to 82.6 mG. A priori job groups showed significant differences between geometric mean exposures, which ranged from 0.80 to 3.51 mG. Most of these groups showed widely ranging exposures, so they were subdivided based on location and job title to improve the precision of the exposure assignments for the mortality study. These final assignments were made up of 26 groups having arithmetic means ranging from 0.43 to 24.9 mG, with most groups defined by location in addition to job title. In general, electrical maintenance workers did not have elevated magnetic field exposures (> 3 mG), but the exposures of the electricians in switchyard (substation) jobs were elevated. Available employment records did not allow most electricians to be distinguished based on location, so they were assigned exposures based on their plantwide average (above 7 mG). An estimated 9% of the work time of this cohort was spent at daily average exposures above 3 mG, despite the very large electric power consumption at this plant.

The effects of keyswitch stiffness and key action on typing force, electromyography (EMG), and subjective preference were examined. Each subject's own keyboard (with an audible key click and key activation force of 0.72 N) and three keyboards with no key click that were identical in design but had different key activation forces (0.28 N, 0.56 N, and 0.83 N) were used. Subjects (24 female transcriptionists) typed on each keyboard for 15 min while typing force and left hand surface EMG of the finger flexor and extensor muscles were monitored. Subjects then used one of the keyboards at their workstations for 7 workdays and were monitored again. This procedure was repeated for all four keyboards. Typing force and finger flexor and extensor EMG activity were highest for the 0.83 N keyboard. Lowest EMG values were for the 0.28 N and the 0.72 N audible key click keyboards. Baseline (10th percentile) and median (50th percentile) extensor EMG values were significantly higher than flexor EMG values. Peak (90th percentile) EMG values were comparable for flexors and extensors. Mean subjective discomfort was significantly higher for the 0.83 N keyboard at the fingers (36% higher), lower arm (40% higher), and overall (39% higher). Seventeen of 24 subjects preferred the 0.72 N keyboard, 4 the 0.28 N keyboard, and 3 preferred the 0.56 N keyboard. Results suggest that increasing make force causes typing force and EMG to increase but that the ratio of 90th centile typing force to make force decreases as make force increases. Subjective discomfort was significantly higher for the keyboard with 0.83 N make force. Buckling spring keyboards have better feedback characteristics, which may be responsible for a decrease in the amount of typing force and EMG produced.

Man-made vitreous fibers (MMVF) have been used widely in commercial and residential buildings for over 50 years. Concerns have been expressed since the late 1960s that MMVF products may erode and contribute to fiber levels in the indoor environment. This cooperative investigation was undertaken to quantify indoor respirable fiber levels by phase contrast optical microscopy (PCOM) and to differentiate between fiber types using scanning electron microscopy with energy-dispersive X-ray microanalysis (SEM-EDX). A total of 205 stationary samples were collected using standard industrial hygiene methods in 51 residential and commercial buildings. Twenty-one simultaneous outdoor samples were collected at 19 buildings. All samples were analyzed by PCOM following the NIOSH 7400 Fiber method, "B" counting rules, and 50 randomly selected samples were analyzed by SEM-EDX. The PCOM mean value for all respirable fiber levels was 0.008 f/cc with a median value of 0.007 f/cc and a maximum value of 0.029 f/cc. Ninety-seven percent of the respirable fibers identified by SEM-EDX were determined to be organic. MMVF were detected on only two samples. Airborne fiber levels were very low and the respirable fibers present were primarily organic. The inorganic fiber levels determined by SEM-EDX which included MMVF were less than 0.0001 f/cc.

As part of a European Concerted Action on Male Reproduction Capability an exposure assessment survey was conducted among seasonal workers in the fruit growing sector in the Netherlands. Dermal exposure to the fungicides captan and tolylfluanid was measured using cotton gloves (12 persons) and skin pads on several body parts (12 persons). In addition, a set of exposure data was used from a study conducted recently among Dutch fruit growers. For harvesting activities, re-entry time appeared to be an important determinant of dermal exposure to captan and tolyfluanid. Explained variance of regression models was moderate to high (range 0.30-0.87). For captan, calculated half-life times from the most recent exposure survey were lower (glove data: 5 days; pad data: 6 days) compared with half-life times based on the previously conducted study (11 days). Possible explanations for the discrepancy are discussed. For tolylfluanid, estimated half-life times during harvesting were 2 and 3 days, based on pad and glove data, respectively. Prediction of captan exposure during other crop activities appeared to be far more difficult (explained variance equal to 0.06), although the estimated half-life time was comparable with that for harvesting. The data suggest that re-entry time gives useful information to group workers in broad exposure categories. Nonetheless, it was concluded that large studies are needed to evaluate the importance of re-entry time in more detail.

This study evaluated police officers' exposures to microwaves emitted by traffic radar units. Exposure measurements were taken at approximated ocular and testicular levels of officers seated in patrol vehicles. Comparisons were made of the radar manufacturers' published maximum power density specifications and actual measured power densities taken at the antenna faces of those units. Four speed-enforcement agencies and one transportation research institute provided 54 radar units for evaluation; 17 different models, encompassing 4 frequency bands and 3 antenna configurations, were included. Four of the 986 measurements taken exceeded the 5 mW/cm2 limit accepted by the International Radiation Protection Association and the National Council on Radiation Protection and Measurement, though none exceeded the American Conference of Governmental Industrial Hygienists, American National Standards Institute, Institute of Electrical and Electronic Engineers, or Occupational Safety and Health Administration standard of 10 mW/cm2. The four high measurements were maximum power density readings taken directly in front of the radar. Of the 812 measurements taken at the officers' seated ocular and testicular positions, none exceeded 0.04 mW/cm2; the highest of these (0.034 mW/cm2) was less than 1% of the most conservative current safety standards. High exposures in the limited region directly in front of the radar aperture are easily avoided with proper training. Results of this study indicate that police officer exposure to microwave radiation is apparently minimal. However, because of uncertainty in the medical and scientific communities concerning nonionizing radiation, it is recommended that law enforcement agencies implement a policy of prudent avoidance, including purchasing units with the lowest published maximum power densities, purchasing dash/rear deck-mounted units with antennae mounted outside the patrol vehicle, and training police officers to use the "stand-by" mode when not actually using radar.

An ergonomics program was developed in a Midwestern electric utility warehouse system. Tasks problematic with respect to work-related musculoskeletal disorders (WMSDs) affecting both the back and upper extremities were identified and engineering controls were implemented. Quantitative analysis was performed on each task before and after ergonomics intervention to evaluate exposure to the risk of WMSDs. Four methods were used to evaluate the risk of exposure to injury before and after ergonomics intervention: the 1991 National Institute for Occupational Safety and Health (NIOSH) lifting equation, the Static Strength Prediction Program, the Lumbar Motion Monitor, and the Borg psychophysical assessment of effort. Results from applying these four methods to the reengineered tasks showed that the probability of low-back disorder risk factors was reduced by as much as 29%, the percentage of people capable of performing tasks was increased by as much as 90%, the NIOSH Lifting Index was reduced from above 2.0 to less than 2.0, and the psychophysical assessment of effort was consistently reduced from the "heavy or strong" range to the "light or moderate" range.

To evaluate the efficacy of engineering controls in reducing worker exposure to metalworking fluids, an evaluation of an enclosure for a machining center during face milling was performed. The enclosure was built around a vertical metal machining center with an attached ventilation system consisting of a 25-cm diameter duct, a fan, and an air-cleaning filter. The evaluation method included using sulfur hexafluoride (SF6) tracer gas to determine the ventilation system's flow rate and capture efficiency, a respirable aerosol monitor (RAM) to identify aerosol leak locations around the enclosure, and smoke tubes and a velometer to evaluate air movement around the outside of the enclosure. Results of the tracer gas evaluation indicated that the control system was approximately 98% efficient at capturing tracer gas released near the spindle of the machining center. This result was not significantly different from 100% efficiency (p = 0.2). The measured SF6 concentration when released directly into the duct had a relative standard deviation of 2.2%; whereas, when releasing SF6 at the spindle, the concentration had a significantly higher relative standard deviation of 7.8% (p = 0.016). This increased variability could be due to a cyclic leakage at a small gap between the upper and lower portion of the enclosure or due to cyclic stagnation. Leakage also was observed with smoke tubes, a velometer, and an aerosol photometer. The tool and fluid motion combined to induce a periodic airflow in and out of the enclosure. These results suggest that tracer gas methods could be used to evaluate enclosure efficiency. However, smoke tubes and aerosol instrumentation such as optical particle counters or aerosol photometers also need to be used to locate leakage from enclosures.

The purpose of this study was to characterize worker exposure to azinphos-methyl (Guthion) over an entire 4-6 week apple-thinning season. Twenty workers from three work sites in the Chelan-Douglas County region of Washington state were recruited for the study. Exposure potential was estimated by dislodgeable foliar residue measurements, and individual exposures were estimated by biological monitoring through urinary metabolites. Measureable azinphos-methyl residues were found on apple foliage at all sites throughout the six-week sampling period, indicating continuous exposure potential (median residue level of 0.5 microgram/cm2). Measurable levels of the urinary dialkylphosphate metabolite, DMTP, were found in virtually all urine samples (limit of detection = 0.04 microgram/mL). Mean DMTP concentrations differed significantly across sites (0.53, 0.29, and 0.90 microgram/mL for Sites 1-3, respectively; analysis of variance, p < .002), and intraindividual variability was much greater than interindividual differences. Group mean DMTP concentrations at each site fluctuated according to foliar residue levels. Measurable DMTP concentrations were found in 9% of reference workers, ranging from 0.04-0.18 microgram/mL. Cholinesterase activity levels monitored with a field test kit were not considered reliable due to temperature changes of the instrument.

This study examined fluid intake, weight changes, and palatability of water and a carbohydrate-electrolyte (ECHO) beverage in two groups of eight subjects performing 4 hours of simulated industrial work while wearing impermeable protective clothing. Subjects also rated the palatability of a flavorless orange-colored water and four commercially available orange-flavored fluid-replacement drinks. Subjects worked 30 min at 300 Kcal/hour (moderate work rate), followed by 30 min of rest for a total of 4 hours in each of three environments: 18, 23, 27 degrees C wet bulb globe temperature (WBGT). Eight subjects drank water and eight drank an ECHO beverage (Drink 1). Mean sweat production was similar between groups at each WBGT, (p > 0.05). Mean weight changes expressed as percentage of total body weight for the water-drinking group were -0.25 (+/- 0.16) kg in 18 degrees C, -0.55 (+/- 0.09) kg in 23 degrees C, and -0.93 (+/- 0.13) kg in 27 degrees C. Mean weight changes for the ECHO-drinking group were 0.49 (+/- 0.12) kg in 18 degrees C, 0.13 (+/- 0.12) kg in 23 degrees C, and -0.02 (+/- 0.14) kg in 27 degrees C. Each change was significantly different from that of the water-drinking group at the same temperatures (p < 0.05). Mean pre- to post-trial palatability rating results for all temperatures revealed differences in taste perception with strong preferences for Drinks 1 and 2 (pre to post): Drink 1, 3.8 to 3.6; Drink 2, 3.8 to 3.7; Drink 3, 3.0 to 2.7, Drink 4 (water), 3.2 to 3.0, and Drink 5, 2.1 to 1.6. Drinks 1 and 2 were rated significantly more palatable (p < 0.05) than Drink 3. All drinks had a reduced flavor appeal from 3.18 (+0.96) preratings to 2.92 (+1.01) postratings (p < 0.05). Mean voluntary consumption during work across the three temperatures was 1561.5 mL (+/- 720.1) for ECHO versus 1062.7 mL (+/- 666.4) for water (p = 0.054). The water group experienced greater weight loss than the ECHO group, suggesting a greater rate of dehydration when water was used for fluid replacement.

Occupational exposure to 50-Hz magnetic fields was surveyed among electric utility workers to investigate (1) components of exposure variability, (2) patterns of autocorrelation between short-term measurements, and (3) imprecision and misclassification due to short-term measurements. Spot measurements every 10 seconds during 81 working days were analyzed for 42 electric utility workers from 10 occupational subgroups and during 8 working days for 4 office workers from the same company. For the 8-hour time-weighted average (TWA) magnetic fields, the variability was partitioned into its components: within workers, between workers, and between groups. For spot measurements of magnetic fields, the within-day variance component also was examined. Autocorrelation functions were determined and numbers of short-term measurements necessary for reliable estimates of 8-hour TWA magnetic fields were assessed. Spot measurements of magnetic fields, as well as 8-hour TWA magnetic fields, were approximately log normally distributed among workers. The mean exposure to magnetic fields was 0.47 microT (n = 81 days) in electric utility workers and 0.12 microT (n = 8 days) in office workers. A large fraction, 76% of the spot measurements total variance, could be attributed to variability within days. For the 8-hour TWA magnetic fields, between-group variability was small and of the same magnitude as between-worker variability. Significant autocorrelations between short-term averages of 7.5, 15, and 30 minutes were present, when taken within periods of 30 minutes. One-hour averages showed no autocorrelation. Simulations showed that, due to high within-day variability and autocorrelation, a limited number of short-term measurements of magnetic fields in electric utility workers are likely to result in imprecise estimates of 8-hour TWA magnetic fields. Measurement strategies relying on short-term (spot) measurements are therefore likely to result in misclassification of exposure and consequently absent or spurious exposure-response relations.