Predictors of Dairy Worker Pre-Test and Post-Test Performance on a Dairy Safety Knowledge Test: Impact of Education Level and Native Language.

BACKGROUND: Efficacy-driven assessments of linguistically appropriate occupational health and safety training (OHS) for dairy workers remain uncommon. This study analyzes predictors of performance on a dairy safety knowledge test using pre-and-post knowledge assessments. The safety training course was delivered by iPad™ to Idahoan dairy workers, managers, and owners. OBJECTIVE: To determine the predictors of safety knowledge scores among dairy worker course participants. METHODS: Predictors of pre-test (baseline) scores and change in test scores of n = 1,336 participants were compared, and multivariate iterative linear regressions were used to predict test performance, adjusting for variables such as occupation, years of formal education, native language, and years in dairy work. RESULTS: Test scores for Spanish and English speakers improved between pre-test and post-test. Years of formal education was the most predictive variable of higher baseline scores and change in test scores among dairy safety course participants, regardless of language. CONCLUSION: Dairy worker safety training course results showed improvements in safety knowledge and test scores. Years of formal education of participants appears to be a key determinant of increases in safety knowledge, and therefore safety training programs need to address the learning needs of less educated workers.

The effect of surface charge, negative and bipolar ionization on the deposition of airborne bacteria.

AIMS: A series of experiments were conducted to evaluate the effect of surface charge and air ionization on the deposition of airborne bacteria. METHODS AND RESULTS: The interaction between surface electrostatic potential and the deposition of airborne bacteria in an indoor environment was investigated using settle plates charged with electric potentials of 0, +/-2.5kV and +/-5kV. Results showed that bacterial deposition on the plates increased proportionally with increased potential to over twice the gravitational sedimentation rate at +5kV. Experiments were repeated under similar conditions in the presence of either negative or bipolar air ionization. Bipolar air ionization resulted in reduction of bacterial deposition onto the charged surfaces to levels nearly equal to gravitational sedimentation. In contrast, diffusion charging appears to have occurred during negative air ionization, resulting in an even greater deposition onto the oppositely charged surface than observed without ionization. CONCLUSIONS: Static charges on fomitic surfaces may attract bacteria resulting in deposition in excess of that expected by gravitational sedimentation or simple diffusion. Implementation of bipolar ionization may result in reduction of bacterial deposition. SIGNIFICANCE AND IMPACT OF STUDY: Fomitic surfaces are important vehicles for the transmission of infectious organisms. This study has demonstrated a simple strategy for minimizing charge related deposition of bacteria on surfaces.

Strain field measurements on mouse carotid arteries using microscopic three-dimensional digital image correlation.

A stereomicroscope system is adapted to make accurate, quantitative displacement, and strain field measurements with microscale spatial resolution and nanoscale displacement resolution on mouse carotid arteries. To perform accurate and reliable calibration for these systems, a two-step calibration process is proposed and demonstrated using a modification to recently published procedures. Experimental results demonstrate that the microscope system with three-dimensional digital image correlation (3D-DIC) successfully measures the full 3D displacement and surface strain fields at the microscale during pressure cycling of 0.40-mm-diameter mouse arteries, confirming that the technique can be used to quantify changes in local biomechanical response which may result from variations in extracellular matrix composition, with the goal of quantifying properties of the vessel.

Occupational exposure to power frequency magnetic fields and risk of non-Hodgkin lymphoma.

OBJECTIVES: To investigate the risk of non-Hodgkin lymphoma (NHL) using a job-exposure matrix (JEM) to assess exposure to occupational magnetic fields at the power frequencies of 50/60 Hz. METHODS: The study population consisted of 694 cases of NHL, first diagnosed between 1 January 2000 and 31 August 2001, and 694 controls from two regions in Australia, matched by age, sex and region of residence. A detailed occupational history was given by each subject. Exposure to power frequency magnetic fields was estimated using a population-based JEM which was specifically developed in the United States to assess occupational magnetic field exposure. The cumulative exposure distribution was divided into quartiles and adjusted odds ratios were calculated using the lowest quartile as the referent group. RESULTS: For the total work history, the odds ratio (OR) for workers in the upper quartile of exposure was 1.48 (95% CI 1.02 to 2.16) compared to the referent (p value for trend was 0.006). When the exposure was lagged by 5 years the OR was 1.59 (95% CI 1.07 to 2.36) (p value for trend was 0.003). Adjusting for other occupational exposures did not significantly alter the results. CONCLUSIONS: These findings provide weak support for the hypothesis that occupational exposure to 50/60 Hz magnetic fields increases the risk of NHL.

Reconstruction of parasacral hernia with acellular human dermis graft.

Parasacral hernias are defects through the pelvic floor which occur as the result of sacral resection. These defects are often large, and are frequently the result of treatment for sacral malignancies. This report documents the case of a 71-year-old woman who underwent radical coccygectomy and partial sacrectomy for a chordoma and subsequently presented 1 year later with a large parasacral hernia. The defect was repaired using an acellular human dermis graft with a gluteus maximus muscle-advancement flap overlay. This article summarizes the current literature of this challenging clinical problem, and examines the use of acellular human dermis in the repair of complex hernias.

The use of biomedical sensors to monitor capsule formation around soft tissue implants.

Piezoelectric sensors have been shown to respond reproducibly to changes in tissue mechanical properties surrounding an implant over a 4-month period. The vibrational amplitude at a frequency corresponding to the radial resonance shows a statistically significant change over time. The initial period of inflammation is marked by a significant reduction in amplitude, which is indicative of an increase in viscous dissipation of the tissue. As collagen displaces the cellular response, the amplitude continues to decrease. Finally, as the tissue matures, the capsule becomes stiffer, and the viscous dissipation lessens. These results are consistent with qualitative assessments of explanted capsules. Strain gauges encased in a monolithic block of silicone exhibited a greater degree of variability, yet show similar trends over time. The strain increases in the initial 4-week period and remains relatively steady over the following 4 weeks. Beyond 8 weeks, the gauges begin to extrude from the animal or suffer a loss of electrical continuity. Steps are being taken to improve the strain sensor longevity in the animals.

The effect of seprafilm and interceed on capsule formation around silicone discs in a rat model.

The insertion of a foreign substance, such as a breast implant into mammalian soft tissues, evokes a wound healing response that culminates in a dense connective-tissue envelope or capsule surrounding the implant. Several biodegradable products, such as Seprafilm (carboxymethylcellulose and hyaluronic acid) and Interceed (oxidized regenerated cellulose), have been demonstrated to inhibit adhesions in abdominal and gynecologic surgery. The ability of these cellulose compounds to inhibit capsule formation was addressed in this investigation. Twenty-eight rats were implanted intermuscularly with either plain silicone discs (10 animals), discs wrapped in Seprafilm (10 animals), or discs covered with Interceed (8 animals). Additional control animals (6 animals) consisted of two that had sham operations, two animals implanted with Seprafilm only, and two more implanted with Interceed only. Animals were sacrificed in pairs at varying time intervals after implantation (2, 4, 8, 12, and 16 wk), and the tissues around the silicone discs were analyzed with light microscopy. Control animals were sacrificed at 8 wk. Both Interceed and Seprafilm slowed the formation of a capsule around the implanted silicone discs as both products were degraded. Evidence of residual material, presumably Seprafilm and Interceed, was seen intracellularly in animals 3 to 4 mo, respectively, after implantation. However, neither material prevented the eventual formation of a fibrous capsule around the silicone discs. The results of this study suggest that encapsulating foreign substances with these types of biodegradable materials will not significantly hinder capsule formation. A more direct attack on the wound healing mechanism may provide a definitive solution for capsule problems with implanted materials.

Chloride/phosphate ratio in primary hyperparathyroidism.

The chloride/phosphate (Cl:PO4) ratio is known to help distinguish between the hypercalcemia of primary hyperparathyroidism (HPT) and hypercalcemia from other causes. The Cl:PO4 ratio of 106 patients with surgically proven primary HPT was compared with that of 126 normocalcemic healthy outpatients to examine its usefulness as a confirmatory test for primary HPT. The Cl:PO4 ratio was significantly higher in patients with HPT (42.5 +/- 7.0) compared with healthy controls (28.7 +/- 4.6). Patients with HPT and mild renal insufficiency (serum creatinine, 1.5-2.4 mg/dL) also showed a significant increase in the Cl:PO4 ratio (37.3 +/- 6.6) as did those with HPT with borderline elevations in serum calcium (calcium < 11; Cl:PO4, 40.3 +/- 5.6). A Cl:PO4 ratio > or = 33 is a reliable diagnostic test for primary HPT when compared with a normal population. The Cl:PO4 ratio is also of value in the evaluation of the patient with suspected HPT and borderline calcium elevation and those with mild renal impairment. These data suggest that an inexpensive Cl:PO4 ratio might replace serum parathormone assay as a confirmatory test in the evaluation of suspected primary HPT, especially for those patients in whom a localizing study (sestamibi scan) is obtained before neck exploration.

Melatonin metabolite excretion among cellular telephone users.

PURPOSE: The relationship between cellular telephone use and excretion of the melatonin metabolite 6-hydroxymelatonin sulfate (6-OHMS) was evaluated in two populations of male electric utility workers (Study 1, n=149; Study 2, n=77). MATERIALS AND METHODS: Participants collected urine samples and recorded cellular telephone use over 3 consecutive workdays. Personal 60-Hz magnetic field (MF) and ambient light exposures were characterized on the same days using EMDEX II meters. A repeated measures analysis was used to assess the effects of cellular telephone use, alone and combined with MF exposures, after adjustment for age, participation month and light exposure. RESULTS: No change in 6-OHMS excretion was observed among those with daily cellular telephone use >25 min in Study 1 (5 worker-days). Study 2 workers with >25 min cellular telephone use per day (13 worker-days) had lower creatinine-adjusted mean nocturnal 6-OHMS concentrations (p=0.05) and overnight 6-OHMS excretion (p=0.03) compared with those without cellular telephone use. There was also a linear trend of decreasing mean nocturnal 6-OHMS/creatinine concentrations (p=0.02) and overnight 6-OHMS excretion (p=0.08) across categories of increasing cellular telephone use. A combined effect of cellular telephone use and occupational 60-Hz MF exposure in reducing 6-OHMS excretion was also observed in Study 2. CONCLUSIONS: Exposure-related reductions in 6-OHMS excretion were observed in Study 2, where daily cellular telephone use of >25 min was more prevalent. Prolonged use of cellular telephones may lead to reduced melatonin production, and elevated 60-Hz MF exposures may potentiate the effect.

Noise exposure among construction electricians.

Data-logging noise dosimetry was used to assess the exposure levels of electricians working for a major electrical subcontractor in Washington State at five sites using four types of construction methods. Subjects documented activities and work environment information throughout their work shift, resulting in an activity/exposure record for each of the 174 full-shift samples collected over the 4-month duration of the study. Over 24% of the TWA samples exceeded 85 dBA; 5.2% exceeded the federal Occupational Safety and Health Administration permissible exposure limit of 90 dBA. The National Institute for Occupational Safety and Health exposure metric, which specifies a 3-dB ER, was also utilized; using this metric, 67.8% of the samples exceeded 85 dBA and 27% exceeded 90 dBA. Subjects were directly observed for a subset of 4469 min during which more detailed activity and environmental information was recorded. Linear and logistic regression models using this subset were used to identify the determinants of average exposure, and exposure exceedences, respectively. These models demonstrated the importance of multiple variable modeling in interpreting exposure assessments, and the feasibility and utility of modeling exposure exceedences using logistic regression. The results further showed that presumably quiet trades such as electrician are at risk of exposure to potentially harmful noise exposures, and that other workers' activities and the general environment contribute substantially to that risk. These results indicate that noise control strategies will have to address the construction work environment as an integrated system.

Field evaluation of a method for estimating gaseous fluxes from area sources using open-path Fourier transform infrared.

This paper describes results from the first field experiment designed to evaluate a new approach for quantifying gaseous fugitive emissions of area air pollution sources. The approach combines path-integrated concentration data acquired with any path-integrated optical remote sensing (PI-ORS) technique and computed tomography (CT) technique. In this study, an open-path Fourier transform infrared (OP-FTIR) instrument sampled path-integrated concentrations along five radial beam paths in a vertical plane downwind from the source. A meteorological station collected measurements of wind direction and wind speed. Nitrous oxide (N2O) was released from a controlled area source simulator. The innovative CT technique, which applies the smooth basis function minimization method to the beam data in conjunction with measured wind data, was used to estimate the total flux from the simulated area source. The new approach estimates consistently underestimated the true emission rates in unstable atmospheric conditions and agreed with the true emission rate in neutral atmospheric conditions. This approach is applicable to many types of industrial areas or volume sources, given the use of an adequate PI-ORS system.

Occupation and adult gliomas.

Lifetime job histories from a population-based, case-control study of gliomas diagnosed among adults in the San Francisco Bay area between August 1991 and April 1994 were evaluated to assess occupational risk factors. Occupational data for 476 cases and 462 controls were analyzed, with adjustment for age, gender, education, and race. Imprecise increased risks were observed for physicians and surgeons (odds ratio (OR) = 3.5, 95% confidence interval (CI): 0.7, 17.6), artists (OR = 1.9, 95% CI: 0.5, 6.5), foundry and smelter workers (OR = 2.6, 95% CI: 0.5, 13.1), petroleum and gas workers (OR = 4.9, 95% CI: 0.6, 42.2), and painters (OR = 1.6, 95% CI: 0.5, 4.9). Legal and social service workers, shippers, janitors, motor vehicle operators, and aircraft operators had increased odds ratios only with longer duration of employment. Physicians and surgeons, foundry and smelter workers, petroleum and gas workers, and painters showed increased risk for both astrocytic and nonastrocytic tumors. Artists and firemen had increased risk for astrocytic tumors only, while messengers, textile workers, aircraft operators, and vehicle manufacturing workers showed increased risk only for nonastrocytic tumors. Despite study limitations, including small numbers for many of the occupational groups, a high percentage of proxy respondents among cases, and lack of specific exposure information, associations were observed for several occupations previously reported to be at higher risk for brain tumors generally and gliomas specifically.

Design and construction of a uniaxial cell stretcher.

In vitro mechanical cell stimulators are used for the study of the effect of mechanical stimulation on anchorage-dependent cells. We developed a new mechanical cell stimulator, which uses stepper motor technology and computer control to achieve a high degree of accuracy and repeatability. This device also uses high-performance plastic components that have been shown to be noncytotoxic, dimensionally stable, and resistant to chemical degradation from common culture laboratory chemicals. We show that treatment with glow discharge for 25 s at 20 mA is sufficient to modify the surface of the rubber to allow proper adhesion for polymerization of aligned collagen. We show through finite element analysis that the middle area of the membrane, away from the clamped ends, is predictable, homogeneous, and has negligible shear strain. To test the efficacy of the mechanical stretch, we examined the effect of mechanical stimulation on the production of beta(1)-integrin by neonatal rat cardiac fibroblasts. Mechanical stimulation was tested in the range of 0-12% stretch and 0-10-cycles/min stretch frequency. The fibroblasts respond with an increase in beta(1)-integrin at 3% stretch and a decrease at 6 and 12% stretch. Stretch frequency was found to not significantly effect the concentration of beta(1)-integrin. These studies yield a new and improved mechanical cell stimulator and demonstrate that mechanical stimulation has an effect on the expression of beta(1)-integrin.

Identification of discrete domains within gonococcal transferrin-binding protein A that are necessary for ligand binding and iron uptake functions.

The availability of free iron in vivo is strictly limited, in part by the iron-binding protein transferrin. The pathogenic Neisseria spp. can sequester iron from this protein, dependent upon two iron-repressible, transferrin-binding proteins (TbpA and TbpB). TbpA is a TonB-dependent, integral, outer membrane protein that may form a beta-barrel exposing multiple surface loops, some of which are likely to contain ligand-binding motifs. In this study we propose a topological model of gonococcal TbpA and then test some of the hypotheses set forth by the model by individually deleting three putative loops (designated loops 4, 5, and 8). Each mutant TbpA could be expressed without toxicity and was surface exposed as assessed by immunoblotting, transferrin binding, and protease accessibility. Deletion of loop 4 or loop 5 abolished transferrin binding to whole cells in solid- and liquid-phase assays, while deletion of loop 8 decreased the affinity of the receptor for transferrin without affecting the copy number. Strains expressing any of the three mutated TbpAs were incapable of growth on transferrin as a sole iron source. These data implicate putative loops 4 and 5 as critical determinants for receptor function and transferrin-iron uptake by gonococcal TbpA. The phenotype of the DeltaL8TbpA mutant suggests that high-affinity ligand interaction is required for transferrin-iron internalization.

The use of electric bed heaters and the risk of clinically recognized spontaneous abortion.

We conducted a prospective cohort study to evaluate the relation of spontaneous abortion and electric bed heater use during the first trimester of pregnancy. Compared with non-users, rates of spontaneous abortion were lower for women who used electric bed heaters. The adjusted odds ratio and 95% confidence interval (CI) for the two major devices used, electric blankets (N = 524) and waterbeds (N = 796), were, respectively, 0.8 (95% CI = 0.5-1.1) and 0.9 (95% CI = 0.7-1.2). An increase of risk with increasing intensity (setting-duration combination) of use was not observed. Users of electric blankets at low settings for most of the night (N = 171) had lower risks of spontaneous abortion than non-users (adjusted odds ratio = 0.5; 95% CI = 0.3-1.0). Twenty women who used electric blankets at a high setting for 1 hour or less had an adjusted odds ratio of 3.0 (95% CI = 1.1-8.3), but we found no spontaneous abortions among the few women (N = 13) who used a high setting for 2 or more hours. We found that exposure rankings of the magnetic field time-weighted average and a rate of change metric did not correspond monotonically to the pattern of spontaneous abortion risks and that electric blankets contribute less to overnight time-weighted average magnetic fields than has been thought.

Tomographic reconstruction of tracer gas concentration profiles in a room with the use of a single OP-FTIR and two iterative algorithms: ART and PWLS.

Computed tomographic (CT) reconstructions of air contaminant concentration fields were conducted in a room-sized chamber employing a single open-path Fourier transform infrared (OP-FTIR) instrument and a combination of 52 flat mirrors and 4 retroreflectors. A total of 56 beam path data were repeatedly collected for around 1 hr while maintaining a stable concentration gradient. The plane of the room was divided into 195 pixels (13 x 15) for reconstruction. The algebraic reconstruction technique (ART) failed to reconstruct the original concentration gradient patterns for most cases. These poor results were caused by the "highly underdetermined condition" in which the number of unknown values (156 pixels) exceeds that of known data (56 path integral concentrations) in the experimental setting. A new CT algorithm, called the penalized weighted least-squares (PWLS), was applied to remedy this condition. The peak locations were correctly positioned in the PWLS-CT reconstructions. A notable feature of the PWLS-CT reconstructions was a significant reduction of highly irregular noise peaks found in the ART-CT reconstructions. However, the peak heights were slightly reduced in the PWLS-CT reconstructions due to the nature of the PWLS algorithm. PWLS could converge on the original concentration gradient even when a fairly high error was embedded into some experimentally measured path integral concentrations. It was also found in the simulation tests that the PWLS algorithm was very robust with respect to random errors in the path integral concentrations. This beam geometry and the use of a single OP-FTIR scanning system, in combination with the PWLS algorithm, is a system applicable to both environmental and industrial settings.

Exposure to 60-Hz magnetic fields and proliferation of human astrocytoma cells in vitro.

Epidemiological studies have suggested that exposure to electric and magnetic fields (EMF) may be associated with an increased incidence of brain tumors, most notably astrocytomas. However, potential cellular or molecular mechanisms involved in these effects of EMF are not known. In this study we investigated whether exposure to 60-Hz sinusoidal magnetic fields (0.3-1.2 G for 3-72 h) would cause proliferation of human astrocytoma cells. Sixty-Hertz magnetic fields (MF) caused a time- and dose-dependent increase in proliferation of astrocytoma cells, measured by (3)H-thymidine incorporation and by flow cytometry, and strongly potentiated the effect of two agonists (the muscarinic agonist carbachol and the phorbol ester PMA). However, MF had no effect on DNA synthesis of rat cortical astrocytes, i.e., of similar, nontransformed cells. To determine the amount of heating induced by MF, temperatures were also recorded in the medium. Both 1.2 G MF and a sham exposure caused a 0.7 degrees C temperature increase in the medium; however, (3)H-thymidine incorporation induced by sham exposure was significantly less than that caused by MF. GF 109203X, a rather specific protein kinase C (PKC) inhibitor, and down-regulation of PKC inhibited the effect of MF on basal and on agonist-stimulated (3)H-thymidine incorporation. These data indicate that MF can increase the proliferation of human astrocytoma cells and strongly potentiate the effects of two agonists. These findings may provide a biological basis for the observed epidemiological associations between MF exposure and brain tumors.

Melatonin metabolite levels in workers exposed to 60-Hz magnetic fields: work in substations and with 3-phase conductors.

Melatonin suppression by 50/60-Hz magnetic fields represents a plausible biological mechanism for explaining increased health risks in workers. Personal exposure to magnetic fields and ambient light, and excretion of the melatonin metabolite 6-hydroxymelatonin sulfate (6-OHMS), were measured over 3 consecutive workdays in electric utility workers. There was a magnetic field-dependent reduction in adjusted mean nocturnal and post-work 6-OHMS levels among men working more than 2 hours per day in substation and 3-phase environments and no effect among those working 2 hours or less. No changes were observed among men working in 1-phase environments. The results suggest that circular or elliptical magnetic field polarization, or another factor linked to substations and 3-phase electricity, is associated with magnetic field induced melatonin suppression in humans.

Localizing gaseous fugitive emission sources by combining real-time optical remote sensing and wind data.

This paper presents a new approach to localize point emissions from ground-level fugitive gaseous air pollution sources. We estimate the crosswind plume's ground-level peak location downwind from the source by combining smooth basis functions minimization (SBFM) with pathintegrated optical remote sensing concentration data acquired along the crosswind direction in alternating beam path lengths. Peak location estimates, in conjunction with real-time measured wind direction data, are used to reconstruct the fugitive source location. We conducted a synthetic data study to evaluate the proposed peak location SBFM reconstruction. Furthermore, the methodology was validated with open-path Fourier transform infrared concentration data collected with wind direction data downwind from a controlled point source. This approach was found to provide reasonable estimates of point source location. The field study reconstructed source location was within several meters of the real source location.