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Asbestos Exposure during Gasket Removal from Aircraft Engine

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Occupational Diseases and Environmental Medicine 2024年第2期12卷 59-67页

作者： Charles L. Blake Kevin M. guth Raymond D. Harbison Apex Companies Marietta USA Center for Environmental and Occupational Risk Analysis and Management College of Public Health University of South Florida Tampa USA

We have previously evaluated asbestos exposure associated with various maintenance procedures on light aircraft. The purpose of this study was to evaluate asbestos exposure during engine maintenance on light aircraft. This test was designed to evaluate the potential for asbestos exposure to mechanics and others who remove asbestos-containing engine gaskets from reciprocating style aircraft engines. Utilized in this test was an air cooled, horizontally opposed, aviation gasoline burning engine, assembled during 1986 and operated intermittently up into 2015, having accumulated 1680 hours run time. Nearly 75% of the asbestos-containing gaskets installed during 1986 were still in place at the time of testing. Chrysotile asbestos contents of such gaskets ranged from 55% to 60% by area, for those of sheet style and 5% by area, for the spiral wound metal/asbestos style. Despite the levels of effort required to effect gasket removals, the professional aircraft mechanic was not exposed to airborne asbestos fibers at the lower limits of sampling and analytical detection achieved;all of which were substantially less than the current Occupational Safety and Health Administration Permissible Exposure Limits for asbestos. The results of this testing indicate an absence of gasket related asbestos exposure risk to mechanics who work with light aircraft engines, including those having asbestos-containing gaskets. These results are consistent with the findings of Mlyarek and Van Orden who studied the asbestos exposure risk occasioned during overhaul of larger radial style reciprocating aircraft engines [1].

关键词： Asbestos Exposure Gaskets Aircraft Engine Friction Materials

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摆脱微软，是时候了吗？

财经 2006年第E3期 79-79页

作者： Robert a.guth 《华尔街日报》

使用更便宜的工具来代替Office仍然是人们的目标，“现实一点来说，我们期待那一天的来临”

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Assessment of Lead Exposures during Abrasive Blasting and Vacuuming in Ventilated Field Containments: A Case Study

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Occupational Diseases and Environmental Medicine 2022年第2期10卷 116-131页

作者： Kevin guth Marie Bourgeois Raymond Harbison Center for Environmental and Occupational Risk Analysis and Management College of Public Health University of South Florida Tampa FL USA

Painting contractors have struggled with implementation and assessment of lead exposure controls leading to persistently elevated blood lead levels in this high-risk group of workers. The objective of this study was to assess the intensity of lead exposures based on commonly used air velocities inside field containment structures during abrasive blasting and vacuuming. Exposures were assessed over 14 days from April to July 2021 at a tainter gate and bridge lead paint removal project. Personal air samples, skin wipes, air velocity readings, and blood lead samples were collected. The geometric mean (GM) lead exposure for abrasive blasters and vacuumers was ≥4 × the OSHA Lead Permissible Exposure Limit (PEL) of 50 μg/m3. There was high variability in the personal lead exposures (Geometric standard deviation (GSD) 4.0 - 5.0). The GM hand wipe exposures exceeded a Dermal PEL of 500 μg/wipe (abrasive blaster 564 μg/wipe and vacuumer 754 μg/wipe). Residual lead was measured on workers’ hands in 67% of the post hand washing samples. Air velocities measured inside of the field containments ranged from 107 feet per minute to 229 feet per minute. The effect of air velocity on the concentration of lead on workers’ hands after work (F = 0.58, p = 0.35) and airborne lead concentration was not significant (F = 0.36, p = 0.48). Six of the eight workers’ blood lead levels increased after exposure to lead. There was a non-statistically significant relationship between lead remaining on workers’ hands after handwashing and an increase in blood lead level. This is the first study that assessed both ventilation flow rates used in the industrial painting industry and measurements of airborne and dermal (hands) lead exposures. For the projects evaluated, the collected exposure data indicate that air velocities frequently used in the industrial painting industry to ventilate field containment structures did not tend to prevent an increase in worker blood lead and were ineffective for adequately controlling elevated concentra

关键词： Occupational Lead Exposure Blood Lead Engineering/Work Practice Controls

Inhibiting WNT secretion reduces high bone mass caused by Sost loss-of-function or gain-of-function mutations in Lrp5

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骨研究:英文版 2023年第3期11卷 595-606页

作者： Cassandra R.Diegel Ina Kramer Charles Moes Gabrielle E.Foxa Mitchell J.McDonald Zachary B.Madaj Sabine guth Jun Liu Jennifer L.Harris Michaela Kneissel Bart O.Williams Department of Cell Biology Van Andel Institute333 Bostwick Ave.NEGrand RapidsMI 49503USA Diseases of Aging and Regenerative Medicine Novartis Institutes for Biomedical ResearchCH-4002 BaselSwitzerland Bioinformatics and Biostatistics Core Van Andel Institute333 Bostwick Ave.NEGrand RapidsMI 49503USA Oncology Novartis Institutes for Biomedical ResearchSan DiegoCA 92121USA

Proper regulation of Wnt signaling is critical for normal bone development and homeostasis.Mutations in several Wnt signaling components,which increase the activity of the pathway in the skeleton,cause high bone mass in human subjects and mouse models.Increased bone mass is often accompanied by severe headaches from increased intracranial pressure,which can lead to fatality and loss of vision or hearing due to the entrapment of cranial nerves.In addition,progressive forehead bossing and mandibular overgrowth occur in almost all subjects.Treatments that would provide symptomatic relief in these subjects are limited.Porcupine-mediated palmitoylation is necessary for Wnt secretion and binding to the frizzled receptor.Chemical inhibition of porcupine is a highly selective method of Wnt signaling inhibition.We treated three different mouse models of high bone mass caused by aberrant Wnt signaling,including homozygosity for loss-of-function in Sost,which models sclerosteosis,and two strains of mice carrying different point mutations in Lrp5(equivalent to human G171V and A214V),at 3 months of age with porcupine inhibitors for 5–6 weeks.Treatment significantly reduced both trabecular and cortical bone mass in all three models.This demonstrates that porcupine inhibition is potentially therapeutic for symptomatic relief in subjects who suffer from these disorders and further establishes that the continued production of Wnts is necessary for sustaining high bone mass in these models.

关键词： homeostasis function mass

Assessment of Asbestos Exposure Associated with a Brake Grinder

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Occupational Diseases and Environmental Medicine 2023年第3期11卷 137-142页

作者： Charles L. Blake Kevin M. guth Raymond D. Harbison Apex Companies Marietta GA USA College of Public Health University of South Florida Center for Environmental and Occupational Risk Analysis and Management Tampa Florida USA

The wear patterns for drum-style automotive brakes tend to enlarge internal drum diameters. Such enlargement is most profound when used brake drums are machined to restore the metal friction surfaces. Specialized arc grinding machinery has been used to match replacement shoe-style brake friction materials to enlarged drums. The process of arc grinding removes friction material, thereby producing dust. When organic-style friction materials contained asbestos, use of arc grinding machinery posed an asbestos fiber exposure risk to operators and proximate personnel. The manufacturers of arc grinding machinery have incorporated local exhaust ventilation systems designed to capture and remove this dust at the point of grinding contact and propel this dust into collection bags or other systems. This research was designed to evaluate the dust capture and retention characteristics of a specific arc grinder product, when used to custom grind asbestos-containing brake friction materials. A Bear Model 1420 automotive brake shoe arc grinder was the subject of this study. During two separate but consecutive test sessions, newly relined sets of shoe-style automobile brake friction materials were precision ground. Both area and personal air samples were collected throughout each testing session. This work took place within a closed and unventilated metal building, with total interior volume of 2500 m3. Collected air samples were analyzed using phase contrast microscopy (PCM) and transmission electron microscopy (TEM). The results of analysis using PCM for personal samples (n = 6) ranged from <0.044 to 0.055 fibers per cc (f/cc) (mean 0.05). Follow-up analysis of these personal samples using TEM indicated asbestos-adjusted PCM exposures ranging from <0.0074 to 0.055 f/cc (mean ≤ 0.041). Area air samples, taken at distances ranging from 1.5 to 9 meters from the arc grinder (n = 12), showed asbestos-adjusted PCM concentrations ranging from <0.0075 to 0.041 f/cc (mean ≤ 0.017). The process of custom arc grinding shoe-styl

关键词： Asbestos Exposure Brakes Arc Grinder Friction Materials

Chemical diffusion and oxygen exchange of LaNi_(0.4)Fe_(0.6)O_(3-δ)ceramics

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Journal of Advanced Ceramics 2014年第3期3卷 240-249页

作者： Jianying CHEN Vladimir VASHOOK Dmytro M.TROTS Shaorong WANG Ulrich guth Chinese Academy of Sciences 1295 Dingxi RoadShanghai 200050China Dresden University of Technology D-01062 DresdenGermany Bayerisches Geoinstitut Universität BayreuthD-95440 BayreuthGermany Meinsberg Kurt-Schwabe Research Institute Kurt-Schwabe-Straße 4D-04720 Ziegra-KnobelsdorfGermany Shanghai Nanotechnology Promotion Center ShanghaiChina

Oxygen surface exchange and oxygen chemical diffusion coefficients of LaNi_(0.4)Fe_(0.6)O_(3-δ)ceramics are determined via conductivity relaxation method after stepwise change of temperature in the range of 700-950℃in air and Ar/O2 gas flow at oxygen partial pressures(p_(o2))of 4 Pa,18 Pa,37 Pa,47 Pa and 59 Pa.The highest conductivity(about 160 S·cm^(-1))is found at 950℃in air.No oxygen exchange(δ=0)below 700℃is observed in the investigated p_(o2) range.The oxygen exchange coefficients determined in reduction mode are higher than those determined in oxidation mode.This is explained by clusterization of oxygen vacancies on the surface of the sample investigated in oxidation mode.The opposite tendency is found for chemical diffusion coefficients.Unlike surface,the oxygen vacancies of the volume region are probably not clustered and have predetermined the higher oxygen diffusion mobility of the sample treated in oxidation mode.

关键词： oxygen non-stoichiometry conductivity chemical diffusion coefficient surface exchange coefficient

Aircraft Brake Dust Dispersion (Airwash) Testing

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Occupational Diseases and Environmental Medicine 2022年第4期10卷 255-261页

作者： Charles L. Blake Robert E. Bailey Kevin M. guth Raymond D. Harbison Apex Companies Marietta GA USA ESi Colorado Springs CO USA Center for Environmental and Occupational Risk Analysis and Management College of Public Health University of South Florida Tampa FL USA

Prior industrial hygiene research involving wheel brake changing on a light general aviation aircraft has shown negligible potential for asbestos fiber exposure to mechanics that perform such work. This is despite the use of organic-style brake friction pads that contained asbestos. It has been otherwise established that chrysotile asbestos is largely degraded to a non-crystalline, amorphous substance by the heat and mechanical shear forces inherent to the braking process. However, trace (<1.0%) quantities of chrysotile have been found in brake wear dust. Disc-style brakes, the types used on aircraft, are of open design, such that wear dust is typically dispersed into the ambient air during and after brake application. For fixed-gear aircraft, the brake assemblies are also subject to substantial air velocities while the aircraft is in flight. This research was undertaken to measure and characterize the airflows experienced by aircraft wheel assemblies during takeoff, cruise, and landing maneuvers. No wear (brake) dust was observed at any point during the study.

关键词： Aircraft Brakes Asbestos Airwash

Evaluation of the Effectiveness of Hygenall<sup>©</sup>Leadoff<sup>TM</sup>Foaming Soap in Reducing Lead on Workers’ Hands and the Uptake of Lead on Bridge Painting Projects

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Occupational Diseases and Environmental Medicine 2020年第4期8卷 123-134页

作者： Kevin guth Marie Bourgeois Giffe Johnson Raymond Harbison Center for Environmental and Occupational Risk Analysis and Management College of Public Health University of South Florida Tampa FL USA

Although considerable research has been conducted regarding airborne lead exposures during lead paint removal, little data has been collected measuring the lead concentration on workers’ hands in the construction industry. As a result, there are gaps in our understanding of the effectiveness of a standard work practice control (handwashing) in the prevention and control of elevated blood lead levels (BLLs) in the workplace. The primary objective of this study was to assess if a National Institute for Occupational Safety and Health (NIOSH) formulation intended to remove lead from skin (Hygenall© LeadoffTM Foaming Soap) is more effective than a commonly used soap in the industrial painting industry (Zep Cherry Bomb Soap) in reducing the concentration of lead on workers’ hands after exposure. A secondary aim was to assess if using LeadoffTM Foaming Soap during handwashing reduces worker uptake of lead on bridge painting projects. We evaluated hand wipe, air sample and blood lead level data collected by two industrial bridge painting contractors. Airborne exposures ranged from 350 μg/m3 to 19,700 μg/m3. The geometric mean lead concentration remaining on workers’ hands after using Zep Cherry Bomb Soap was 77 μg per hand wipe compared with 61 μg per hand wipe after use of LeadoffTM Foaming Soap for all work classifications. The geometric lead concentration on workers’ hands decreased by 16 μg/hand wipe for all work classifications combined after using LeadoffTM Foaming Soap—a decrease of 21%. The use of Hygenall LeadoffTM Foaming Soap reduced the maximum lead concentration on workers’ hands by 85%. The geometric mean BLL for all work classifications was 12.1 μg/dl before the use of LeadoffTM. After two months of airborne exposure and use of LeadoffTM Foaming Soap at breaks and at the end of the workday, the geometric mean BLL for all work classifications increased t

关键词： Dermal Exposure Blood Lead Level Bridge Painting Handwashing

Evaluation of Lead Exposure by Hand Wipes: A Review of the Effectiveness of Personal Hygiene on Industrial Sites

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Occupational Diseases and Environmental Medicine 2019年第4期7卷 135-143页

To evaluate the effectiveness of personal hygiene (handwashing) amongst workers at industrial sites to remove lead from their hands, a retrospective analysis of hand wipe samples was conducted using data collected by two contractors from two bridge painting projects for total lead using method ASTM E-1979-17/EPA SW846 7000B. Exposures resulted from the removal of lead-based paint from the structure and trace elements of lead found in the abrasive blast media. In total, six work tasks were evaluated and sixty unique hand wipe samples were evaluated. Thirty samples were collected during the worker’s lunch break, after they had reportedly washed their hands with a further 30 collected at the end of the workday following the same protocol. To be included in this evaluation, the contractors were required to follow NIOSH Method 9105 (Lead in Dust Wipes-Dermal Surfaces) with subsequent analysis of samples for total lead by an American Industrial Hygiene Association (AIHA) accredited laboratory. All 60 samples contained detectable lead. The lead exposures ranged from 19.5 μg to 3420 μg. The geometric mean for the samples collected was 337 μg. These results indicate that current personal hygiene practices at the evaluated sites are not effective at removing lead from worker’s hands during and after the workday. They also suggest that the residual lead measured on the workers’ hands, at the end of the shift, is likely contributing to the elevated blood lead levels in this population.

关键词： OSHA Lead Exposure Assessment Painter Blood Lead Level Prevention and Control Industrial Contractor