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M Corn

Publications and source records attributed to M Corn.

At least 37 records · Page 2Linked to original sources
PubMed1992

Historical perspective on approaches to estimation of inhalation risk by air sampling.

Epidemiological investigation involving historical cohorts requires reconstruction of individual cohort member exposures during the period of study. However, past approaches to exposure assessment by industrial hygienists were characterized by different professional expectations for air sampling, and different orientations for evaluation of air sampling results. The activity designated as "exposure assessment" today was not seriously undertaken prior to the late 1970s. It is important to understand the methodologies utilized in earlier years to assess the quality of workplace air because assumptions of exposure during those years are critically dependent on the utilization of shortterm air sampling results obtained by methods which differ from those employed today. This paper reviews the approaches and methodologies utilized in the United States during the 1930-1980 period to measure airborne concentrations of suspended particulate matter and gaseous contaminants. Specific examples are used to illustrate the obstacles encountered when translating these usually limited data into cumulative exposure indices utilized in testing the hypothesis of a dose-response relationship in epidemiological investigations. The misuse of these data results in exposure misclassification and obscuration of any dose-response relationship(s). Selected options for validation of earlier exposures and for increasing or decreasing confidence in recognized incomplete earlier exposure information are discussed. The problems identified and explored in this presentation are inevitable in dealing with available historical occupational exposure data. They will persist for years and demand attention if the information associated with these incomplete data sets is to be defensibly utilized.

Air Pollutants, Occupational↗
PubMed1992

Exposure to airborne asbestos in buildings.

The concentration of airborne asbestos in buildings and its implication for the health of building occupants is a major public health issue. A total of 2892 air samples from 315 public, commercial, residential, school, and university buildings has been analyzed by transmission electron microscopy. The buildings that were surveyed were the subject of litigation related to suits alleging the general building occupants were exposed to a potential health hazard as a result of exposure to the presence of asbestos containing materials (ACM). The average concentration of all asbestos structures was 0.02 structures/ml (s/ml) and the average concentration of asbestos greater than or equal to 5 microns long was 0.00013 fibers/ml (f/ml). The concentration of asbestos was higher in schools than in other buildings. In 48% of indoor samples and 75% of outdoor samples, no asbestos fibers were detected. The observed airborne concentration in 74% of the indoor samples and 96% of the outdoor samples is below the Asbestos Hazard Emergency Response Act clearance level of 0.01 s/ml. Finally, using those fibers which could be seen optically, all indoor samples and all outdoor samples are below the Occupational Safety and Health Administration permissible exposure level of 0.1 f/ml for fibers greater than or equal to 5 microns in length. These results provide substantive verification of the findings of the U.S. Environmental Protection Agency public building study which found very low ambient concentrations of asbestos fibers in buildings with ACM, irrespective of the condition of the material in the buildings.

Air Pollutants↗
PubMed1992

The effectiveness of the Duo-Flo BioClean unit for controlling airborne antigen levels.

The Duo-Flo BioClean unit, consisting of a chamber unit with an animal rack, a HEPA filtration system, an air plenum, and a blower, was evaluated as a control unit for airborne rat antigen levels in the room housing the unit. The unit was evaluated in negative and positive pressure operating modes. In the negative mode, room air is drawn into the unit, passes over the animal cages, and is then exhausted into the room through the filters. In the positive mode, air passes through the filters, traverses the animals, and then is discharged into the room. Airborne antigen concentrations (ng/m3) and particle size distributions associated with antigen were measured during the two operating modes and prior to operation (background mode). Airborne antigen concentrations during the positive pressure operating mode were higher than during the negative pressure mode or background. Approximately 70% of airborne antigen was associated with respirable particles during background and positive pressure operating modes. A total of 36% of airborne antigen mass was associated with respirable particles during negative pressure operation. The unit is usually operated in the positive mode to protect experimental animals. This study clearly indicates that negative pressure operation would reduce the dispersion of dust-containing antigen, the exposure of room occupants to airborne antigen, and the risk to many workers of contracting animal allergy.

Air Pollutants, Occupational↗
PubMed1991

Airborne concentrations of asbestos in 71 school buildings.

A total of 473 air samples from 71 schools scheduled for abatement (328 indoor static samples, 51 personal samples, and 94 outdoor samples) were analyzed by transmission electron microscopy techniques. Six measures of asbestos-in-air concentration were considered: (1) total asbestos structures per cubic centimeter: (2) chrysotile structures per cubic centimeter; (3) amphibole structures per cubic centimeter; (4) structures per cubic centimeter at least 0.5 micron long and at least five times wide; (5) structures per cubic centimeter at least 5 microns long; and (6) structures per cubic centimeter at least 5 microns long and at least 0.2 micron wide. The average concentration of chrysotile structures in indoor air samples was 0.017 structures/cm3; the average concentration of amphibole structures was 0.0015 structure/cm3. Ninety-five percent of structures found were chrysotile. The average concentrations of all structures were significantly higher indoors than outdoors (P less than 0.001). The average concentration of structures more than 5 microns long indoors was 0.00023 structure/cm3. None of the following factors were significantly correlated with asbestos concentrations in air: type of asbestos-containing materials (ACM) present, condition of ACM, accessibility of ACM to students, whether ACM were covered, air flow, or whether sweeping was noted during sample collection. In addition, asbestos-in-air concentrations were not significantly different in different types of schools (high, intermediate or elementary) or in schools constructed in different time periods. Lastly, there was no correlation between the mineral type of asbestos found in the air and the type found in samples of bulk material.

Air↗
PubMed1991

Regulatory implications of airborne respirable free silica variability in underground coal mines.

The respirable dust standard for respirable free crystalline silica in underground coal mines is expressed as milligrams per cubic meter (mg/m3) of respirable dust and is determined by the silica content of the dust. The Mine Safety and Health Administration (MSHA) regulates silica exposure by determining and enforcing compliance with the respirable dust standard for each active mine section. The MSHA strategy for regulation is examined in the context of respirable free crystalline silica and dust data. Deficiencies of the strategy include the same enforcement efforts regardless of compliance history, inappropriate treatment of data, and emphasis on short-term variability of silica content. These deficiencies result in inadequate enforcement in chronically dusty mines, "game playing" with optional samples, and an overall approach that does not focus on the long-term impact of silica exposure on lung health. Alternative approaches include enforcement efforts proportional to compliance history, use of a moving average silica content, and more statistically sound approaches to data interpretation.

Air Pollutants, Occupational↗
PubMed1990

Asbestos: scientific developments and implications for public policy.

Asbestos is a commercial term for a group of fibrous minerals often associated with the development of pulmonary interstitial fibrosis (asbestosis), lung cancer, and malignant mesothelioma in occupationally exposed individuals. The pathogenicity of different forms of asbestos varies--long, thin amphibole fibers are most pathogenic, particularly in the induction of mesothelioma. Available data do not support the concept that low-level exposure to asbestos is a health hazard in buildings and schools. The concentration of asbestos fibers in air, type of asbestos, and size of fibers must be considered in evaluation of potential health risks.

Animals↗
PubMed1990

Occupational challenge studies with laboratory workers allergic to rats.

To relate airborne Rat N I concentrations to airway responses in allergic laboratory workers, we collected allergen on personal monitors while workers and control subjects were exposed in a rat vivarium for 1 hour. Allergen concentrations ranged from less than 1.5 to 310 ng/m3 and were significantly (p less than 0.001) higher during cage cleaning (19 to 310 ng/m3) than during quiet activity (less than 1.5 to 9.7 ng/m3). Among 12 rat-allergic volunteers, all had a nasal response during the exposure with an increase in nasal lavage histamine concentrations or TAME-esterase activity, but only five volunteers had a lower respiratory tract response (fall in FEV1 greater than 10%). Two of five allergic control subjects had a small change in nasal TAME-esterase activity, and none had a 10% fall in FEV1. A dose response was demonstrated between the allergen concentrations and the intensity of the nasal allergic response. This occupational challenge procedure thus was able to measure the nasal and lower respiratory tract response to airborne allergen exposure in a work environment. It can be used to define further the determinants of this response.

Adolescent↗
PubMed1990

Noise exposure reduction aboard an oceangoing hopper dredge.

Reported industrial hygiene surveys aboard seagoing vessels are few, despite the presence of many potentially hazardous chemical and physical agents aboard ships. This investigation focused on crew noise exposure aboard an oceangoing hopper dredge. Noise exposure criteria were adopted based on the 24-hr equivalent continuous sound level (Leq(24)) because of the absence of standards for U.S. shipboard noise exposure. Personal noise dosimeters were used to measure the noise exposure of watchstanders, whose duties were predictable and repetitive. Watchstanders with high noise doses were asked to estimate their duration of exposure in specific areas of the vessel to enable calculation of noise dose per space. Noise sources within spaces associated with high noise dose were identified by sound pressure and surface vibration analysis in octave bands. Almost all accommodation spaces (cabins, recreation rooms, dining rooms, and hospital) were sufficiently quiet (sound pressure levels [SPLs] less than 65 dBA) to permit hearing threshold recovery. Machinery space SPLs ranged from 85 to 108 dBA, and engineering personnel noise exposure exceeded the selected criterion of Leq(24) = 80 dBA. Selective noise abatement and use of an enclosed operating station in the engine room were recommended to control engineering personnel noise exposure. This approach to noise exposure assessment and reduction should be applicable to other oceangoing ships where personnel may be exposed to noise 24 hr per day for weeks at a time.

Engineering↗
PubMed1990

First year's experience of the MAClinical Computer Workstations Project.

We have an installed base of MAClinical workstations available on hospital wards, which have been used for patient care, education, and research 24 hours a day for the past year. We began with eight machines in the hospital but now have distributed ten more machines to faculty. We have recently increased the programming staff so we can develop more software. The machines and their installation were costly, but have already proven useful for teaching and patient care. Plans for the second and third years of the MAClinical project include workstations for the faculty coordinators of clinical clerkships and expansion of workstations to affiliated hospitals where our students and residents rotate. Software will be expanded to include patient simulations and expert consultations. Medical practice, research, and teaching in the future will need to make more use of information technology. It is not yet clear exactly how and where computers will best serve clinical medicine, but the teaching hospital can be both a laboratory for developing applications and a school for training physicians to use them.

Clinical Clerkship↗
PubMed1989

Task-related variation in airborne concentrations of laboratory animal allergens: studies with Rat n I.

To define airborne allergen exposure during various tasks with rats in a laboratory, concentrations of allergen Rat n I were measured by radioimmunoassay in extracts from filters in personal air sampling devices that were worn by laboratory workers while they were performing these tasks. The tasks included feeding, cage cleaning, handling, injection, surgery, and sacrifice. Median concentrations encountered during feeding or cleaning (21 ng/m3) and injection or handling (13 ng/m3) were higher than those associated with surgery or sacrifice (3.1 ng/m3; p less than 0.01). Area samples in animal-holding rooms contained 3.4 ng/m3 during animal handling and 2.3 ng/m3 at other times. Very low concentrations were found in air outside the handling room, in unused laboratories, or outside air. We concluded that certain tasks incur a higher risk of allergen exposure but that exposure may occur anywhere within an animal laboratory environment.

Air Pollutants, Occupational↗
PubMed1989

The role of the worksite inspection under the Occupational Safety and Health Act. Reflections on 17 years of OSHA experience.

The inspection process has its counterpart in other areas of safety, namely, automobile safety, airplane safety, truck safety, structural safety, and the like. That we are less than pleased with the results in measures of workplace safety performance during the last decade and a half is not a reason to forsake the inspection process. There are ways to greatly improve the inspection process. The current dialogue should focus on extensions and improvements of inspections rather than relieving regulates of the inspection experience. The inspection process has demonstrated its value as a safety management tool.

Environmental Exposure↗
PubMed1988

Effects of adsorbed water vapor on the adsorption rate constant and the kinetic adsorption capacity of the Wheeler kinetic model.

A recent trend in occupational safety and health has focused on the use of respiratory protective equipment to supplant engineering controls as the primary means of protecting workers from toxic substances. Respirator adsorbent cartridges have been demonstrated to have a finite capacity to adsorb toxic vapors. The knowledge of when this limit is approached or has been exceeded is crucial to the user. The Wheeler kinetic breakthrough model has been shown to describe accurately organic vapor penetration through beds of activated carbon. The model, however, does not account for competitive adsorption of water vapor or other organic vapors. The investigations reported here demonstrate the effect of adsorbed water vapor on the kinetic adsorption parameters (kinetic rate constant and kinetic saturation capacity) of the Wheeler equation. Adsorbent beds were equilibrated at varying concentrations of water vapor and then challenged with carbon tetrachloride vapor-laden air. Dry carbon had an initial rate constant of 62.5 s-1 and a kinetic adsorption capacity of 0.36 g of adsorbed CCl4/gram (g/g) of adsorbent. These parameters decreased in proportion to the amount of water vapor adsorbed, with the minimum predicted values occurring at 100% relative humidity. The minimum experimental value for the kinetic rate constant was 17.6 s-1, a decrease of 73% from the dry carbon values. The minimum predicted value for the kinetic adsorption capacity was 0.16 g/g, a decrease of 45%.

Adsorption↗
PubMed1988

Implementing RECONSIDER, a diagnostic prompting computer system, at the Georgetown University Medical Center.

RECONSIDER, a computer program for diagnostic prompting developed at the University of California, San Francisco, has been implemented at the Georgetown University Medical Center as part of the Integrated Academic Information Management System Model Development grant project supported by the National Library of Medicine. The system is available for student use in the Biomedical Information Resources Center of the Dahlgren Memorial Library. Instruction on use of the computer system is provided by the library and instruction on medical use of the knowledge base is directed by the faculty. The implementation, capabilities, enhancements such as the addition of Current Medical Information and Terminology (5th ed.), and evaluation of the system are reported.

Computer User Training↗
PubMed1987

Methods to assess airborne concentrations of cotton dust.

Assessment of concentrations of airborne cotton dust in the factory is necessary to determine adherence to applicable Permissible Exposure Limits (PELs) on a day-to-day basis, as well as for investigatory studies of an epidemiological nature. The latter are required on an ongoing basis to determine the adequacy of PELs to prevent disease in the exposed population. A strategy of sampling includes considerations of the numbers of samples to be obtained for statistical validity and the locations of samples. Current practice is to obtain more "personal samples" of exposure wherever possible, but with regard to cotton dust, instrumentation is not available for such sampling. In the U.S., the vertical elutriator is the instrument of choice for determining the concentrations of cotton dust in air. Results are expressed as milligrams of airborne particulate (cotton dust) per cubic meter.

Air Pollutants, Occupational↗
PubMed1987

Evidence for dermal absorption as the major route of body entry during exposure of transformer maintenance and repairmen to PCBs.

Traditional industrial hygiene assessment of exposure to polychlorinated biphenyls (PCBs) has long focused on air concentrations as a surrogate measure of worker dose. Evidence is presented to support the hypothesis that the dermal and dermal/oral routes of worker PCB exposure are major contributors to total PCB body burden in the group of transformer maintenance and repair personnel studied. Additional evidence is presented to demonstrate the critical role of work practices in determining PCB exposure. These hypotheses challenge the long-held notion of the pre-eminent importance of respiratory exposure to PCBs.

Humans↗
PubMed1986

UNRWA and the health of Palestinian refugees. United Nations Relief and Works Agency.

The United Nations Relief and Works Agency for Palestine refugees (UNRWA) has provided health, education, and welfare services since 1949. A team of physicians from Georgetown University visited UNRWA Health Centers and refugee camps in Jordan, Lebanon, the West Bank, and the Gaza Strip, as well as some affiliated hospitals. Living conditions of refugees vary widely. In Jordan and the West Bank, fewer than one third live in camps, whereas in the Gaza Strip and Lebanon, conditions are more crowded. Effective programs for health education, maternal and child health, and immunization have markedly improved the health of the refugees over the years of UNRWA's operation. The general health of the population is good, primarily as a result of wise emphasis on public health and preventive medicine measures.

Child↗
PubMed1986

Determination of organic vapor respirator cartridge variability in terms of degree of activation of the carbon and cartridge packing density.

The protection provided by carbon-containing organic vapor respirator cartridges depends in part on the packing density of the carbon in the cartridges and its degree of activation. Large variations in these parameters could have significant effects on the service-life of respirator cartridges. Variability among commercially available organic vapor respirator cartridges was examined with regard to the following characteristics: the particle size distribution, amount of carbon and packing density of the carbon in the cartridges and the degree of activation of the carbon. The degree of activation was determined by measuring the maximum adsorption space and the structural constant of the carbon. These two parameters--Wo (cm3/g) and k (cal/M)-2--are constants in the Dubinin/Radushkevich (D/R) model from which physical absorption onto microporous adsorbents, such as activated carbon, are described. Respirator cartridges from three different suppliers were examined. Significant variability (11-40%) in the amount and the degree of activation of the carbon occurred between cartridges of different manufacturers, as well as among cartridges of an individual manufacturer.

Carbon↗