Breathing Zone Concentrations Research Articles

Ventilatory function and personal breathing zone dust concentrations in Lancashire textile weavers.

BACKGROUND: To report findings on ventilatory function and estimations of concentrations of personal breathing zone dust in Lancashire textile weavers. Weaving room dust is considered to be less harmful than...

Exposures from thorium contained in thoriated tungsten welding electrodes.

Information provided in this article can be used for estimating the radiation dose associated with the use of thoriated tungsten electrodes in tungsten inert gas welding. Area and breathing zone concentrations of 232Th generated by welding and electrode sharpening along with particle size information; isotopic composition of electrodes from two domestic manufacturers and one European manufacturer; and process variables and estimates on the number of thoriated tungsten electrodes manufactured are presented. Past literature is reviewed and compared with the results of this study. Isotopic analysis of a nominal 2% thoriated electrode found 0.6 ppm +/- 0.4 ppm 230Th and less than 0.1 ppm 228Th. Analysis of a ceriated tungsten electrode and a lanthanated tungsten electrode for 232Th found 124 ppm and 177 ppm, respectively. Electrode consumption during welding was primarily the result of tip sharpening. Less than 3% of the weight loss was attributable to the welding process. The in-mask concentration of respirable thorium particulate in the welder's breathing zone was 0.002 x 10(-12) microCi 232Th/mL. The concentration of respirable thorium particulate from electrode sharpening was 1.3 x 10(-12) microCi 232Th/mL. The measured sharpening time was 20 sec per electrode. Estimates of the activity median aerodynamic diameters for the respirable fraction of the welding and electrode sharpening aerosols were 3.5 and 5 microns, respectively, when measured in the breathing zone at 0.3 m (12 inches) from the point of operation. The respirable fraction of the total welding and sharpening aerosols was 45 and 60%.

Meeting report

Meeting report

Modeling Breathing-Zone Concentrations of Airborne Contaminants Generated During Compressed Air Spray Painting

This paper presents a mathematical model to predict breathing-zone concentrations of airborne contaminants generated during compressed air spray painting in cross-flow ventilated booths. The model focuses on characterizing the generation and transport of overspray mist. It extends previous work on conventional spray guns to include exposures generated by HVLP guns. Dimensional analysis and scale model wind-tunnel studies are employed using non-volatile oils, instead of paint, to produce empirical equations for estimating exposure to total mass. Results indicate that a dimensionless breathing zone concentration is a nonlinear function of the ratio of momentum flux of air from the spray gun to the momentum flux of air passing through the projected area of the workers body. The orientation of the spraying operation within the booth is also very significant. The exposure model requires an estimate of the contaminant generation rate, which is approximated by a simple impactor model. The results represent an initial step in the construction of more realistic models capable of predicting exposure as a mathematical function of the governing parameters.

Assessment of workers' exposure to aromatic hydrocarbons in a paint industry.

A factory survey was conducted in a paint industry in Tehran-Iran. The time-weighted average of toluene and xylene concentration in breathing zone and environmental air were monitored by charcoal tube samplers and GC-FID. The results showed that the tank cleaners had the highest exposure to toluene and xylene (1.5-5.4 times of TLV), while the workers in packaging workshops had the lowest. However, environmental concentration did not show significant differences in workshops and their levels were all lower than the TLV.

Modeling Breathing-Zone Concentrations of Airborne Contaminants Generated During Compressed Air Spray Painting

This paper presents a mathematical model to predict breathing-zone concentrations of airborne contaminants generated during compressed air spray painting in cross-flow ventilated booths. The model focuses on characterizing the generation and transport of overspray mist. It extends previous work on conventional spray guns to include exposures generated by HVLP guns. Dimensional analysis and scale model wind-tunnel studies are employed using non-volatile oils, instead of paint, to produce empirical equations for estimating exposure to total mass. Results indicate that a dimensionless breathing zone concentration is a nonlinear function of the ratio of momentum flux of air from the spray gun to the momentum flux of air passing through the projected area of the worker's body. The orientation of the spraying operation within the booth is also very significant. The exposure model requires an estimate of the contaminant generation rate, which is approximated by a simple impactor model. The results represent an initial step in the construction of more realistic models capable of predicting exposure as a mathematical function of the governing parameters.

Breathing zone concentration variations in the reinforced plastic industry; field measurements in a boat manufacturing plant.

Breathing zone samples are used to estimate worker exposure to airborne contaminants by collecting air from a vaguely defined zone surrounding the head. This zone is considered to have an airborne chemical concentration equivalent to the concentration breathed by the worker. It has been generally assumed that vapor is uniformly mixed in the breathing zone; therefore, samplers are placed on either lapel or on the chest of the worker. An extensive field investigation in a boat manufacturing plant was conducted where styrene air concentrations were measured by mounting four 3M one-stage diffusion samplers around the worker's breathing zone. Two job classes were studied: the spray gun operators and the rolling and tucking operators. Styrene air concentrations detected at the nose were significantly different than those concentrations detected at the other three locations and represented 90 percent, 84 percent, and 76 percent of the left lapel, right lapel, and chest samplers, respectively. This research revealed that the chest sampler provides a consistent relationship to the concentrations measured at the nose for a given job category. Additionally, this research identified the possible factors which could contribute to breathing zone concentration variations.

Control of Exposure Caused by a Contaminant Source in the near Wake Region

Abstract A person in a unidirectional air flow may be exposed to considerable amounts of airborne contaminants if the contaminant source is within the wake region downstream of the body. This study examined how a local vertical air supply and a local exhaust can reduce the transport of contaminants from the near wake region to a mannequin's breathing zone in a unidirectional air flow. This transportation was studied by releasing a tracer gas from several points within the wake region, one point at a time, and measuring the breathing zone concentration with different local air supply and exhaust flow rates. Numerical simulations were also done in the case of a local air supply using the standard k-ε model for turbulence closure. By focusing the control measures on the wake region, improved contaminant control with relatively small air flow rates can be achieved. Although both ventilation methods studied reduced the breathing zone concentration, the arrangement that involved the use of the local air supply was more efficient than the local exhaust method in controlling the exposure. The relative changes in the mean exposure could be satisfactorily predicted with numerical simulations and a particle tracking method.

Kiln emissions and potters' exposures.

Some ten thousand British Columbia potters work in small private studios, cooperative facilities, educational institutions, or recreation centers. There has been considerable concern that this diffuse, largely unregulated activity may involve exposures to unacceptable levels of kiln emissions. Pottery kiln emissions were measured at 50 sites--10 from each of 5 categories: professional studios, recreation centers, elementary schools, secondary schools, and colleges. Area monitoring was done 76 cm from firing kilns and 1.6 m above the floor to assess breathing zone concentrations of nitrogen dioxide, carbon monoxide, sulfur dioxide, fluorides, aldehydes, aluminum, antimony, arsenic, barium, beryllium, boron, cadmium, chromium, cobalt, copper, gold, iron, lead, lithium, magnesium, manganese, mercury, nickel, selenium, silver, vanadium, and zinc. Personal exposures to the same metals were measured at 24 sites. Almost all measured values were well below permissible concentrations for British Columbia work sites and American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit values (TLVs) with the following two exceptions. A single firing duration (495 minute) acrolein measurement adjacent to an electric kiln (0.109 ppm) exceeded these guidelines. One 15-minute sulfur dioxide measurement collected adjacent to a gas kiln (5.7 ppm) exceeded the ACGIH short-term exposure limit. The fact that concentrations in small, ventilated kiln rooms ranked among the highest measured gives rise to concern that unacceptable levels of contamination may exist where small kiln rooms remain unventilated. Custom designed exhaust hoods and industrial heating, ventilating, and air-conditioning systems were the most effective ventilation strategies. Passive diffusion and wall/window fans were least effective.

Exposure to methyl tert-butyl ether and tert-amyl methyl ether from gasoline during tank lorry loading and its measurement using biological monitoring.

The exposure of Finnish tank lorry drivers to methyl tert-butyl ether (MTBE) and tert-amyl methyl ether (TAME) during loading of gasoline was studied using biological and breathing-zone sampling. During the field measurements in October 1994 and August 1995 the gasolines (95, 98, 99 RON) contained MTBE to 5.2-11.8% and TAME to 0-6%. The geometric mean (GM) breathing-zone concentration of MTBE was 4.3 mg/m3 (n = 15) in October and 6.4 mg/m3 (n = 20) in August. The GM concentration of TAME, measured only in August, was 0.98 mg/m3. The mean loading/sampling times were 37 and 35 min, the mean wind speeds were 0.8 and 0.6 m/s, and the mean air temperatures were -4.9 degrees and + 14.1 degrees C, respectively. Blood samples collected on average at 20 min after gasoline loading/exposure showed an MTBE concentration of 143 nmol/l (GM, n = 14) in October and 213 nmol/l (GM, n = 20) in August. Pearson's coefficient of correlation (r) between the MTBE breathing-zone concentrations and MTBE in blood was 0.86 (P = 0.0001) in October and 0.81 (P = 0.00001) in August. No correlation was found between MTBE in air and the metabolite tert-butanol (TBA) in blood. MTBE, but not TBA, in urine samples collected on average at 2.5 h after exposure showed a correlation with MTBE in air. The concentrations of TAME and its metabolite tert-amyl alcohol were below the quantitation limits ( < 7 and < 100 nmol/l, respectively) in most blood and urine samples. The breathing-zone measurements showed low levels of exposure to the two oxygenates, the concentrations being well below the current hygienic standards for MTBE (250-360 mg/m3 for 15 min and 90-180 mg/m3 for 8 h). The linear correlations obtained for MTBE suggest that MTBE in blood or urine can be adopted as a valid biological exposure index.

Reconstruction of Inhalation Exposure and Uptake for Asbestos Fibres

In epidemiological studies and risk assessments involving inhalation of hazardous substances, it is conventional to estimate cumulative exposure as the product of exposure level (i.e. concentration in the worker's breathing zone) and exposure duration. In some cases the time component is implicit, e.g. where exposure levels are expressed as 8 h or 15 min time-weighted averages. However, a third variable is required if we wish to estimate the quantity of material inhaled into the body: the worker's breathing rate. The importance of breathing ventilation rate has long been recognised. Oldham and Roach (1952) discussed their particle concentrations in coal mines in relation to cumulative exposure and the product of concentration and ventilation rate, which they termed dose. Similarly, in laboratory studies of people exposed to solvent vapours the impact of work rate and hence ventilation rate, is well known (Opdam, 1989; Wallen et al, 1985; Fiserova-Bergerova, 1985; Bowes et al., 1995); with increasing breathing rate leading to increased concentrations of the substance or its metabolites in the body. Jones et al. (1981) have also published a field study of the differences in ventilation rate among coalminers underground. In this study the cumulative exposure of a group of workers is compared with an alternative exposure variable: the uptake, which is defined as the product of exposure level (e.g. measured in fibres m~), exposure duration (e.g. in hours) and breathing rate (e.g. in m h). For asbestos, uptake is expressed as the number of fibres inhaled, while cumulative exposure is presented as fibre ml.years.

Simulated Exposure of Hospital Emergency Personnel to Solvent Vapors and Respirable Dust During Decontamination of Chemically Exposed Patients

Study objective: To ascertain the breathing-zone level of organic solvents and respirable particulates in a simulated hospital patient decontamination. Design: An adult-sized, clothed plastic mannequin was contaminated with a solvent or particulate, then decontaminated. Rescuers were exposed to acetone, p-xylene, iron oxide, or zinc oxide during decontamination. We performed breathing-zone air sampling on the two rescuers. Five trials were run with each chemical. Participants: Two physicians performed the decontamination. Results: Measured breathing-zone concentrations for the chemicals tested were significantly lower than their respective short-term breathing-zone limits (P =.042, .043, .001, and .001 for acetone, p-xylene, iron, and zinc oxide, respectively). Conclusion: The chemicals tested during simulated hospital decontamination did not pose a respiratory health risk to rescuers. This model may be useful in the extrapolation of breathing-zone exposure to more toxic chemicals. Because ours are preliminary data, the use of respiratory protective equipment during decontamination must be recommended. [Schultz M, Cisek J, Wabeke R: Simulated exposure of hospital emergency personnel to solvent vapors and respirable dust during decontamination of chemically exposed patients. Ann Emerg Med September 1995;26:324-329.]

Low flow anaesthesia reduces occupational exposure to inhalation anaesthetics Environmental and biological measurements in operating room personnel

In the present study we evaluated the occupational exposure to N2O and isoflurane during open circuit (OC) (fresh gas flow > or = minute volume) and low flow (LF) (fresh gas flow = 1.5 l/min) anaesthesia. The effects of active scavenging and of a charcoal filter positioned on the exhausting branch of the ventilator on environmental and urinary concentrations of inhalation anaesthetics were also investigated. The study was carried out in the same operating room provided with non-recirculating air changes (10 per hour). It involved anaesthetists and nurses during routine activity. N2O and isoflurane concentrations (time-weighted average) were measured after 3-hour continuous exposure: 1) in the environment at the level of the personnel's breathing zone (Ci); 2) in the environment at the ventilator zone (C); 3) in urine (Cu). During OC anaesthesia without active scavenging the breathing zone concentration of both N2O and isoflurane was very high (194.6 +/- 15.2 and 5.0 +/- 0.4 ppm, respectively). The activation of the scavenging greatly reduced the breathing zone concentration of N2O (31.6 +/- 4.1 ppm) and isoflurane (1.7 +/- 0.2 ppm). LF anaesthesia (with active scavenging) significantly reduced the environmental concentration of both anaesthetics (Ci N2O and isoflurane 22.7 +/- 1.8 and 0.6 +/- 0.04 ppm, respectively). During LF anaesthesia the breathing zone concentration of N2O remained low, even without scavenging (22.7 +/- 1.8 ppm). Similar results were obtained by measuring N2O and isoflurane concentrations at the ventilator zone and in urine.(ABSTRACT TRUNCATED AT 250 WORDS)

COMPUTATIONAL SIMULATION OF WORKER EXPOSURE USING A PARTICLE TRAJECTORY METHOD

The velocity field downstream of a worker is approximated with a discrete vortex algorithm. This information is used to calculate trajectories of massless tracer ‘particles’ released from a point-source of contaminant. Concentrations in the plane of this source are estimated by averaging over a number of such trajectories. Approximations include: (1) representing the worker by a two-dimensional elliptical cylinder; and (2) representing tracer gas contaminant by massless particles generated without momentum. These particles are transported by both vortex shedding and turbulent diffusion. Computer-predicted mean concentrations in the near-wake region downstream of the worker compare well with results from wind-tunnel tracer gas experiments employing a mannequin. Subsequently, the concept of a computational breathing zone is introduced, and predictions of worker exposure are made. These simulations of time-integrated breathing zone concentration also compare well with measured values.

Computational simulation of worker exposure using a particle trajectory method

The velocity field downstream of a worker is approximated with a discrete vortex algorithm. This information is used to calculate trajectories of massless tracer ‘particles’ released from a point-source of contaminant. Concentrations in the plane of this source are estimated by averaging over a number of such trajectories. Approximations include: (1) representing the worker by a two-dimensional elliptical cylinder; and (2) representing tracer gas contaminant by massless particles generated without momentum. These particles are transported by both vortex shedding and turbulent diffusion. Computer-predicted mean concentrations in the near-wake region downstream of the worker compare well with results from wind-tunnel tracer gas experiments employing a mannequin. Subsequently, the concept of a computational breathing zone is introduced, and predictions of worker exposure are made. These simulations of time-integrated breathing zone concentration also compare well with measured values.

Ribavirin Aerosol

1. Two new exhaust control methods for scavenging and removing excess ribavirin aerosol were evaluated. Air samples were collected from pediatric intensive care rooms to determine the concentration of ribavirin. 2. Both control methods produced a 99.9% reduction between patient breathing zone concentrations and general room air concentrations. The average room air concentrations of ribavirin were 64 and 37 micrograms/m3 with the control methods in place, compared to average patient breathing zone concentrations of 45,000 and 58,000 micrograms/m3. 3. Additional control methods are reviewed, and published ribavirin environmental monitoring data is summarized. 4. Though the effect on fetal development in humans is not known, it is recommended that occupational exposure to ribavirin aerosol be minimized. A safe level for occupational exposure was calculated to be 91 micrograms/m3 for an 8-hour time weighted average.

A model for correcting Workplace Protection Factors for lung deposition and other effects.

The Workplace Protection Factor (WPF) is a measure of the protection provided by an industrial respirator against a challenge agent. It is traditionally defined as the ratio of the ambient contaminant concentration (Co) in a worker's breathing zone to the in-facepiece contaminant concentration (Ci) that occurs during inhalation, and is determined by simultaneous concentration measurements during the time the respirator is worn. There are several sources of particulate loss that result in the overestimation of the true WPF. A model is presented to "estimate" these losses so that an adjusted or "unbiased" WPF can be calculated. This model requires three measurements: Co, Ci, and the ambient aerodynamic mass frequency particle size distribution (PSD). Both Co and Ci are expressed in units of "mass per unit volume." There are four steps to the calculation of the unbiased WPF. First, the in-facepiece PSD is estimated using the ambient PSD and a particle leak penetration curve. Second, the fraction of the in-facepiece PSD that will deposit in the lung is estimated using the in-facepiece PSD and a "reference worker" total lung deposition curve. Third, the fraction of the in-facepiece PSD that will deposit at the inlet of the sampling probe during both inhalation and exhalation is estimated using the in-facepiece PSD, the exhaled in-facepiece PSD, and published inlet deposition data. Last, the adjusted in-facepiece concentration is calculated using the estimates from steps two and three. The adjusted WPF, WPFa, is then calculated as the ratio of the measured ambient contaminant concentration and the adjusted in-facepiece concentration.

METHYLENE CHLORIDE EXPOSURE IN INDUSTRIAL WORKERS

Methods of environmental and biological monitoring were applied in order to evaluate exposure to methylene chloride in workers operating in a factory where this substance was used as a solvent. For the measurement of methylene chloride in environmental concentration, the ambient air was sampled by using personal passive dosimeters. The activated charcoal was desorbed with CS2 and injected into a gas chromatograph connected with a mass spectrometer. The biological monitoring of exposed workers was performed by determining the concentration of CO in alveolar air (CA, ppm) and methylene chloride in urine (Cu, mu/L). Immediately after the end of the exposure, a urine sample was collected avoiding solvent loss and using gas-tight samplers. Excretion level in urine was determined by using headspace gas chromatography linked to a mass spectrometer. The CO was determined at the end of the shift by using a portable instrument. A group of 20 workers (12 smokers and 8 nonsmokers) in the manufacturing plant were monitored. No significant correlation was observed among the CO of all subjects and the concentration of methylene chloride in ambient air. When those workers who smoked were removed from the analysis, a correlation between the methylene chloride concentration in air and the CO concentration in alveolar air was found. Significant linear correlation was found between the environmental concentration of methylene chloride in the breathing zone and methylene chloride concentration in urine.

The effect of contaminant source momentum on a worker's breathing zone concentration in a uniform freestream.

Several factors affecting breathing zone concentration were examined in a paint spray booth by using a tracer gas method. The variables in the study include contaminant momentum, the presence of a flat plate downstream of the worker, the distance between the contaminant source and the body, and the worker's motion. A dramatic reduction in breathing zone concentration was observed when the spray gun emitted contaminants with high momentum. Reductions of 30-50% were observed because of the other variables. The source momentum effect was studied, subsequently, in a wind tunnel by measuring the breathing zone concentration of a mannequin with various flows through jets of different diameter, at varying freestream velocities. A functional relationship was determined between nondimensional breathing zone concentration and contaminant source momentum. This relationship is supported by numerical simulations. The effect of contaminant momentum on the near-wake flow field is discussed in conjunction with results from the numerical simulations.

The Effect of Contaminant Source Momentum on a Workerʼs Breathing Zone Concentration in a Uniform Freestream

The Effect of Contaminant Source Momentum on a Workerʼs Breathing Zone Concentration in a Uniform Freestream