Michael R. Flynn

Characterization of emissions from burning incense.

The primary objective of this study was to improve the characterization of particulate matter emissions from burning incense. Emissions of particulate matter were measured for 23 different types of incense using a cyclone/filter method. Emission rates for PM2.5 (particulate matter less than 2.5 microm in aerodynamic diameter) ranged from 7 to 202 mg/h, and PM2.5 emission factors ranged from 5 to 56 mg/g of incense burned. Emission rates were also determined using an electrical low pressure impactor (ELPI) and a small electrostatic precipitator (ESP), and emission rates were compared to those determined using the cyclone/filter method. Emission rates determined by the ELPI method were consistently lower than those determined by the cyclone/filter method, and a linear regression correlation was found between emission rates determined by the two methods. Emission rates determined by the ESP method were consistently higher than those determined by the cyclone/filter method, indicating that the ESP may be a more effective method for measuring semivolatile particle emissions. A linear regression correlation was also found between emission rates determined by the ESP and cyclone/filter methods. Particle size distributions were measured with the ELPI, and distributions were found to be similar for most types of incense that were tested. Size distributions by mass typically ranged from approximately 0.06 to 2.5 microm in aerodynamic diameter, with peak values between 0.26 and 0.65 microm. Results indicated that burning incense emits fine particulate matter in large quantities compared to other indoor sources. An indoor air quality model showed that indoor concentrations of PM25 can far exceed the outdoor concentrations specified by the US EPAs National Ambient Air Quality Standards (NAAQS), so incense smoke can pose a health risk to people due to inhalation exposure of particulate matter. Emissions of carbon monoxide (CO), nitric oxide (NO), and sulfur dioxide (SO2) were also measured for seven types of incense. Emission rates of the gaseous pollutants were sufficient to cause indoor concentrations, estimated using the indoor air quality model, to exceed the outdoor concentrations specified by the NAAQS under certain conditions. However, the incense samples that were tested would fill a room with thick smoke under these conditions.

Neurological risks associated with manganese exposure from welding operations – A literature review

Exposure to manganese dusts and fumes may cause a clinical neurological syndrome called manganism. Welders are frequently exposed to manganese-containing fumes generated by electric arcs and thermal torches. This paper reviews studies on the association between exposure to such welding fumes and neurological disease. Using the IRSST expert panel criteria, 78 cases of probable/possible, and 19 additional cases of possible occupational manganism were identified in the literature among manganese-exposed workers involved in welding processes. Epidemiological evidence linking welding exposures to Parkinsons disease is still controversial. Although more research is needed to clarify the risks of neurological impairment from welding, control measures including ventilation and adequate respiratory protection, should be implemented to minimize welding fume exposures. The significance of fume transport into the central nervous system via the olfactory nerve, which by-passes the blood-brain barrier, also needs to be assessed.

Manganese, iron, and total particulate exposures to welders.

Welders are exposed to a variety of metal fumes, including manganese, that may elevate the risk for neurological disease. This study examines several large data sets to characterize manganese, iron, and total particulate mass exposures resulting from welding operations. The data sets contained covariates for a variety of exposure modifiers, including the presence of ventilation, the degree of confinement, and the location of the personal sampler (i.e., behind or in front of the welding helmet). The analysis suggests that exposures to manganese are frequently at or above the current ACGIH® threshold limit value of 0.2 mg/m3. In addition, there is evidence that local exhaust ventilation can control the exposures to manganese and total fume but that mechanical ventilation may not. The data suggest that higher exposures are associated with a greater degree of enclosure, particularly when local exhaust ventilation is absent. Samples taken behind the helmet were, in general, lower than those measured outside of it. There were strong correlations among manganese, iron, and total particulate mass exposures, suggesting simple equations to estimate one fume component from any of the others.

Engineering Controls for Selected Silica and Dust Exposures in the Construction Industry -- A Review

This literature review summarizes engineering control technology research for dust and silica exposures associated with selected tasks in the construction industry. Exposure to crystalline silica can cause silicosis and lung fibrosis, and evidence now links it with lung cancer. Of over 30 references identified and reviewed, 16 were particularly significant in providing data and analyses capable of documenting the efficacy of various engineering controls. These reports include information on generation rates and worker exposures to silica and dust during four different tasks: cutting brick and concrete block, grinding mortar from between bricks, drilling, and grinding concrete surfaces. The major controls are wet methods and local exhaust ventilation. The studies suggest that while the methods provide substantial exposure reductions, they may not reduce levels below the current ACGIH threshold limit value (TLV) of 0.05 mg/m(3) for respirable quartz. Although further research on controls for these operations is indicated, it is clear that effective methods exist for significant exposure reduction.

Airflow pattern around a worker in a uniform freestream

The effect of boundary layer separation on worker exposure is an important factor in the design of local exhaust ventilation. Three-dimensional airflow around a mannequin is examined by using flow visualization techniques and hot-film anemometry. Above the chest, a downwash effect is noted; from the chest to the elbows, a combination of downwash and vortex shedding is observed; and from the waist to the hip, vortex shedding appears to be dominant. A coherent vertical flow structure is observed close to the body. Vortex shedding frequency is determined by using hot-film anemometry. The dimensions of the reverse flow region and the area of the vortices are estimated from flow visualization videos.

A review of wake effects on worker exposure

Boundary layer separation leads to the formation of a wake region downstream of a worker in an air flow field. This fundamental phenomenon is responsible in many cases for compromising the intended beneficial effect of ventilation designed to reduce worker exposure to toxic airborne substances. A review of some simple mathematical models to describe the impact of wakes on exposure is presented along with some field studies illustrating the effect. The importance of flow visualization to detect and correct the problem cannot be overstated. The research suggests that work practices in many cases are as important as the ventilation design in achieving successful control, and that a well designed local exhaust system must include an understanding of how the worker performs the job I N T R O D U C T I O N As air flows around the human body boundary layer separation produces a wake similar to that which exists behind a ship moving through the water. This is an important factor in determining a workers exposure to toxic airborne contaminants, particularly when the source of pollution and the breathing zone are within the wake region. The wake is a mixing zone characterized by eddies or vortices which entrain air into a reverse-flow region near the body. It is this entrained air flow and the contaminant generation rate that determine worker exposure. Unlike the wake behind a ship, a clearly visible phenomenon, vortices produced around people and objects in the work environment are not observed unless flow visualization techniques are employed. Control of worker exposure to airborne pollutants is the primary responsibility of the occupational hygienist. An understanding of how wakes impact on exposure is essential if successful control interventions are to be implemented. Exposure is typically defined as the time-weighted average concentration (CrWA) experienced by the worker over some specified period (T), where Q 2 is the breathing zone concentration. The period is often either 8 h or 15 min depending upon whether the occupational exposure level (OEL), selected as a target, is a short-term ceiling value or a full-shift level. The breathing zone concentration is a function of the contaminant generation rate (G) and the air velocity field (U). All ^Visiting Professor at the University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7400, U.S.A. 211 at Penylvania State U niersity on Sptem er 8, 2016 http://annhfordjournals.org/ D ow nladed from 212 M. R. Flynn and B. Ljungqvist human exposure problems to airborne contaminants may be cast within this framework: the difficulties lie in specifying G and U as functions of space and time. The purpose of this paper is to summarize basic theoretical, experimental and field studies which have been conducted by the authors and which examine the influence of wakes on human exposure. The emphasis is on formulating a basic conceptual and mathematical model for understanding wakes and contaminant transport within them, and examining real world exposure problems in the light of the models and their limitations.

In Vivo Imaging of T Cell Priming

The rules by which naïve T cells decide whether and how to respond to antigenic stimuli are incompletely understood. Using multiphoton intravital microscopy (MP-IVM) in lymph nodes (LNs), we have shown that CD8+ T cells are primed by antigen-presenting dendritic cells (DCs) in three consecutive phases. During phase one, T cells undergo brief serial contacts with many DCs for several hours after homing into the LNs. Subsequently, during phase two, T cells engage in prolonged stable interactions with DCs. Finally, in the third phase, T cells return to transient interactions with DCs as they begin to proliferate and eventually leave the LNs. We have examined the influence of antigen dose on the duration of phase one by systematically varying both the number of cognate peptide–major histocompatability (pMHC) complexes per DC and the density of cognate pMHC complex–presenting DCs per LN. The duration of phase one and the kinetics of CD8+ T cell activation were inversely correlated with both parameters. Very few pMHC complexes were needed for full T cell activation and effector differentiation. Furthermore, there was a sharp threshold of antigen dose below which T cells did not transition to phase two but continued to migrate until they exited the LN, unactivated. The stability of peptide binding to MHC was a critical determinant of this threshold antigen dose in vivo. Our results suggest an integrative mechanism that allows T cells to reach an informed decision about whether to respond, based on the overall antigen dose encountered.

Manganese and Welding Fume Exposure and Control in Construction

Overexposure to welding fume constituents, particularly manganese, is of concern in the construction industry due to the prevalence of welding and the scarcity of engineering controls. The control effectiveness of a commercially available portable local exhaust ventilation (LEV) unit was assessed. It consisted of a portable vacuum and a small bell-shaped hood connected by a flexible 2 inch (50.8 mm) diameter hose, in both experimental and field settings. The experimental testing was done in a semienclosed booth at a pipefitter training facility. Five paired trials of LEV control vs. no control, each approximately 1 hr in duration and conducted during two successive welds of 6 inch (152.4 mm) diameter carbon steel pipe were run in random order. Breathing zone samples were collected outside the welding hood during each trial. In the field scenario, full-shift breathing zone samples were collected from two pipefitters welding carbon steel pipe for a chiller installation on a commercial construction project. Eight days of full-shift sampling were conducted on both workers (n = 16), and the LEV was used by one of the two workers on an alternating basis for 7 of the days. All samples were collected with personal sample pumps calibrated at 2 L/min. Filter cassettes were analyzed for total particulate and manganese concentration by a certified laboratory. In the experimental setting, use of the portable LEV resulted in a 75% reduction in manganese exposure (mean 13 μg/m 3 vs. 51 μ g/m 3 ; p < 0.05) and a 60% reduction in total particulate (mean 0.74 mg/m 3 vs. 1.83 mg/m 3 ; p < 0.05). In the field setting, LEV use resulted in a 53% reduction in manganese exposure (geometric mean 46 μ g/m 3 vs. 97 μ g/m 3 ; p < 0.05) but only a 10% reduction in total particulate (geometric mean 4.5 mg/m 3 vs. 5.0 mg/m 3 ; p > 0.05). These results demonstrate that LEV use can reduce manganese exposure associated with welding tasks in construction.

The Impact of Boundary Layer Separation on Local Exhaust Design and Worker Exposure

Abstract The phenomenon of boundary layer separation is an important factor in determining a workers breathing zone concentration. This article presents the results of flow visualization and tracer gas studies, conducted in a wind tunnel with a mannequin, designed to examine this phenomenon. A simple conceptual model, based on mass transport by vortex shedding, provides a reasonable estimate of the mannequins breathing zone concentration. An empirical model is developed which relates the measured concentration to the distance from the source to the breathing zone for the situation when the contaminant is released downstream in a uniform flow. Applications of the results are discussed.

On the Use of Computational Fluid Dynamics in the Prediction and Control of Exposure to Airborne Contaminants—an Illustration Using Spray Painting

Computational fluid dynamics (CFD) is employed to simulate breathing-zone concentration for a simple representation of spray painting a flat plate in a cross-flow ventilated booth. The results demonstrate the capability of CFD to track correctly changes in breathing-zone concentration associated with work practices shown previously to be significant in determining exposure. Empirical data, and models verified through field studies, are used to examine the predictive capability of these simulations and to identify important issues in the conduct of such comparisons. A commercially available CFD package is used to solve a three-dimensional turbulent flow problem for the velocity field, and to subsequently generate particle trajectories for polydisperse aerosols. An in-house algorithm is developed to convert the trajectory data to breathing-zone concentrations, transfer efficiencies and aerosol size distributions. The mesh size, time step, duration of the simulation, and number of particles per size interval are all important variables in achieving convergent results.