David A. Fraser

A model for deposition of fibers in the human respiratory system

A mathematical model for estimating lung deposition of fibers is described. It is based on the aerodynamic behavior of thin straight rods. Predicted deposition values for rods of various equivalent aerodynamic diameters and lengths, for each of three tidal volumes and for each of three respiratory system compartments are reported.

Air sampling and analysis in a rubber vulcanization area.

Results of sampling and analysis of air in a rubber vulcanization area are described. Organic compounds were collected on activated charcoal, desorbed with carbon disulfide and analyzed by gas chromatography. Several previously identified substances were quantitated, including styrene, toluene, ethylbenzene, and several oligomers of 1,3-butadiene. Concentrations ranged from 0.007 to 1.1 ppm.

Long-Term Effects of Sulfur Dioxide and Graphite Dust on Rats

Exposure of rats to graphite dust (1 mg/m/sup 3/) or 1 ppM SO/sub 2/ plus dust for 12 hr/day, 7 days/wk, for 4 mo did not retard growth or alter microbiological properties of the respiratory tract. Histology indicated chronic viral pneumonia in many rats but no effect of treatment.

Ciliary Activity and Pulmonary Retention of Inhaled Dust In Rats Exposed to Sulfur Dioxide

While the ciliary activity in the airways of rats exposed to sulfur dioxide at low concentration has been studied repeatedly, the effects of chronic exposure to realistic levels of sulfur dioxide and particulates has not been determined. This paper describes the response of white albino rats to the inhalation of low concentrations of sulfur dioxide while exposed to relatively high concentrations of an inert dust. Test results indicate that no change is found in the ciliary activity or the relative number of dust cells in the alveolar structure of rats exposed to 1 ppm of sulfur dioxide and 1 mg/m3 of a graphite dust.

A laboratory evaluation of long term detector tubes: Benzene, Toluene, Trichloroethylene

In the early 70s evaluations were published about the accuracy and calibration of short term detector tubes for vapors. The results still provide the basis for approval criterion. More recently, tubes designed for long term sampling have become available. These have been evaluated in the laboratory using a sensitive dynamic system capable of generating a relative humidity from 10 to 100% and vapor concentrations from 5 to 2000 ppm. The detector tubes were exposed to known concentrations under specified test conditions. Charcoal tubes were also tested simultaneously under the same conditions. The results indicate that the color development of the long term detector tubes is more affected by humidity and sampling volume than the short term tubes. Different approval criteria and test methods may be required for these tubes. The long term detector tubes may well compete with charcoal tubes if certain improvements can be made by the manufacturers to increase reliability. The precision and accuracy of long ter...

Passive dosimetry using detector tubes

Detector tubes for toluene were cut to produce a nominal 0.5 cm orifice above the indicator material, and exposed to known vapor concentrations. The time needed to reach a pre-determined stain length by simple diffusion was measured. Calibration charts were prepared for time versus concentration for a 1 mm stain, as well as for various stain lengths. Tests were performed to determine the effect of increasing the orifice length and of diffusion through the glass wool plug. Each of these parameters resulted in less reliable concentration measurements than tubes of relatively shorter orifice length having no glass wool plug. Diffusion theory was used to develop theoretical calibration charts for comparison with experimental results, with the former underestimating necessary for appearance of the experimentally observed stains. The use of detector tubes having an orifice length of 0.5 cm as passive dosimeters is shown to be highly feasible based on experimental results.

Exhaust Ventilation for Hot Processes

Furnaces, forges, ovens, melting pots, and other industrial processes requiring heat present different ventilation problems than cold processes. Exhaust ventilation requirements for a hot process are examined. Hemeons empirical equation for predicting the minimum exhaust flow required by a heated source was investigated experimentally and correlated with data.

A Continuously Recording Instrument to Measure Air-Borne Ion Concentration

Abstract A vacuum tube electrometer was developed and used in conjunction with portable, shortened concentric cylinder ion collectors which is capable of monitoring ion concentrations in air. The electrometer can operate high impedance recorders which produce a continuous recording of ion levels in ambient air with a time constant of approximately 30 seconds, with proportionally faster response for higher levels of concentration.

The Assessment of the Total Toxicant Exposure of Man

Abstract Because of the increase in the opportunities for non-occupational exposures to biologically active substances in the community environment it is becoming necessary for the industrial hygienist to consider the 24 hour environment of the worker in evaluating the stress imposed by occupational exposures to toxic substances. The evaluation of the total exposure to toxicants will require the development of new tools and concepts.

An Innocuous Tracer Technique for Testing the Performance of Ventilation Systems

Abstract An aerosol of uniformly sized sodium chloride particles has been used as a tracer to evaluate air flow patterns in a hospital operating room. A portable flame photometer was used to determine the concentration of the aerosol and chloride sensitive gelatin strips showed the deposition of the particles by settling at various locations in the room.