Morton Corn

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.

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.

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.

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.

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.

End User Exposures to Man-Made Vitreous Fibers: I. Installation of Residential Insulation Products

Abstract An investigation was undertaken to develop a comprehensive characterization of end user exposures to residential man-made vitreous fiber insulation products in terms useful for future study of potential health outcomes. Nearly 1200 air samples were collected and analyzed gravimetrically or by phase contrast microscopy or scanning electron microscopy to describe worker exposure in eight homogeneous exposure groups defined by man-made vitreous fiber product and occupation. These samples represent the exposure of 99 different workers insulating 107 different houses in 11 states in the eastern and central United States. Gravimetric and fiber count exposure concentrations are reported in terms of task length and full shift time-weighted averages (TWAs). Results of this study indicate mean task length airborne fiber concentrations determined by phase contrast microscopy (PCM) using the National Institute for Occupational Safety and Health (NIOSH) Method 7400 “B” rules to be less than 1.0 fibers/cm3 for...

Asbestos and disease: an industrial hygienist's perspective

I have traced a personal thirty year journey of involvement with asbestos in the workplace and the nonoccupational environment, one still in progress, in an attempt to extract selected lessons for the industrial hygienist. Lessons for other professions, namely medicine, law and management have been studiously avoided in the interests of the scope of this presentation and permissible time. There are certainly numerous other lessons to contemplate. The movement of asbestos from the occupational to the nonoccupational environment is a case study that will undoubtedly be followed in the future by other potentially toxic materials. We must determine our position as a profession with regard to the tools we utilize, the procedures we follow, and our understanding of our moral and legal obligations to prepare for the often scientifically and technically unsupportable positions assumed by others, including governmental agencies, in their zeal to bring about change. We must discourage the opportunistic distortion of professional practices in these matters, and must issue well considered statements as a profession, statements relevant to the way these matters are addressed by society. We have a responsibility to lend perspective to these issues, to not permit understandably emotional responses to documented past severe health effects in other areas, such as the case of asbestos in the workplace, to carry over into conditions of very low exposures in the public domain. We must remind people of the relevance of dose-response and toxicological principles to assessment of risk.(ABSTRACT TRUNCATED AT 250 WORDS)

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%.

AIRBORNE FIBER CONCENTRATIONS DURING SPLITTING OPEN AND BOXING BAGS OF ASBESTOS

Measured airborne concentrations of asbestos are often unavailable to assess different epidemiologic estimates of past personal exposure levels or concentrations near specific operations involving handling asbestos. The purpose of this study was to assess the potential use of a laboratory study in estimating exposure to asbestos in operations that ceased for many years. The asbestos transfer operations were simulated by splitting and boxing 4.5-kg paper bags of chrysotile asbestos in an enclosed chamber ventilated at 28.2 air changes per hour (ACH). Two recirculation fans achieved chamber air mixing. The airborne concentration of asbestos fibers was determined by sampling air through membrane filters at a rate of 10 l/min and by analysing fibers by phase contrast optical microscopy to determine 15-min average airborne concentrations. Samplers were located at four equidistant locations from the operation. Opening a maximum of seven bags in 15 min was associated with an asbestos-in-air concentration of less than 2 × 10-6 fibers/m3 (f/m3) in splitting open and boxing and less than 0.85 × 10-6 f/m3 in boxing of pre-split bags. The measured airborne asbestos concentration exhibited a linear trend with the number of bags opened per 15 min. The empirical results were utilised to model fiber concentrations for various ventilation rates. It was concluded that the distribution of the operation within the workday and the ventilation rate are the two most important variables in the determination of the estimated time-weighted average concentration. Splitting open and boxing 32 bags of asbestos over an 8-h period at a rate of 4 bags / h over an 8-h period results in a calculated time-weighted average exposure of about 1 × 10-6 f / m3 in a work space with 20 ACH and approximately 7 × 10-6 f / m3 in a work space with 2 ACH. Splitting open and boxing at a rate of 12 bags / h for 2 h and 45 min yielded calculated concentrations less than one-half of the abovementioned values. These results should serve as a useful benchmark for epidemiologists concerned with the magnitude of exposure in historically dusty industrial tasks.

Asbestos Exposures of Building Maintenance Personnel

Abstract We have analyzed the maintenance logs maintained by owners of buildings containing asbestos fireproofing and subject to operations and maintenance (OM filter analyses were by phase contrast microscopy in certified laboratories. OM negative pressure containment was not used. A total of approximately 50...