June, 2000 - Issue 9

June, 2000

Inhalation Newsletter

Dear Colleague,

This is the ninth issue of the http://www.inhalation.net newsletter for June, 2000.

In July and August, a single number will issue at the end of July. Notices and requests should reach the Editor before July 15.

 Articles/Issues of Current Interest in Inhalation Toxicology Tremolite "Asbestos" in Crayons Recent reports of Tremolite in children's crayons were big news over the Memorial Day weekend and thereafter. The source of this "contaminant" was said to be New York state talc that is used to fortify or otherwise strengthen the crayon as it is manufactured. The Editor (who is also an AHERA Asbestos Inspector for a local school) reports on an experiment he performed with a sample of commercially obtained "children's" crayons. One of the name brand of crayons identified in the news reports was purchased in Waitsfield, Vermont. Twelve were randomly chosen from a larger box, stripped of their paper wrappers, broken into bits (large and small) and agitated by oscillation for a total of 16 hours (4 four hour intervals with low frequency sound, 60 cps using a sound driven "dust" generator developed by Yves Alarie and his colleagues at the University of Pittsburgh). When operated, the generator chamber had an input air flow of 10 liters per minute. The outflow was directed to a closed glass tank with a polycarbonate cover (approx. 50 liter in volume and made from glass and plastic). This so called aquarium was used as a mixing chamber. All of its joints and edges were taped or otherwise sealed; the system was run at positive pressure. The closed "mixing" chamber was then sampled sequentially using a BGI respirable dust cyclone at 2.1 liters per minute (drawn by vacuum, controlled by a critical flow orifice, nominal flow rate of 2 liters per minute). The Millipore filters were of a type used for Asbestos sampling (37 mm, 0.8 micron); they were subsequently analyzed by TEM (Chatfield AHERA method). The final result from the laboratory reported that no Tremolite asbestos structures were detected in the filters examined. While others are invited to repeat this test, the Editor concludes from this one experiment that crayons ( at least this sample of this brand) does not pose a health risk. The tested crayons did not release respirable airborne Tremolite fibers. That is, under the conditions tested, there is no Tremolite exposure hazard from this product. However, we weren't surprised at the announcement that crayons would no longer be made with the suspected talc ingredient. Our readers and colleagues may wish to examine other consumer products outside this limited range to see if this kind of a hazard exists elsewhere.

 Note added in Proof: Professor Arthur Langer of the Brooklyn Polytechnic Institute reports to the editor (personal communication) that this same experiment was conducted by him at Mount Sinai School of Medicine, New York, some twenty-five years ago with similar negative findings. Sheldon Murphy would have termed this "Re-Search".

Aerosols and Size Changes with Drying Doug Cooper outlines the process of aerosol drying and its impact on particle size. He reports that aerosols for inhalation studies can be generated from gas - phase reactions, fragmentation of dust cakes or dispersal of powders, and atomization of liquids, our focus here. Except in an atmosphere that is super - saturated with its vapor, a droplet starts to evaporate as soon as it is formed. The process is not simple. As it evaporates, the droplet cools, losing heat energy to supply the latent heat of vaporization. Cooling slows evaporation, by lowering the vapor pressure, and evaporation may increase the concentration of solutes, also lowering the vapor pressure and slowing evaporation. For more, see the complete article about drying.

Dr. Susan Shami reviews a recent aerosol generation report. Dry submicron particles are important in the chemistry of atmospheric aerosols and climate conditions. Although there are data on the role of liquid particles in the atmosphere, the same is not true for dry particles such as soot, mineral aerosols and salts. The complete report and reference is: fluidized_bed_generator

Dr. Shami is in the process of building a useful glossary of terms. See the glossary

Some of these appeared in a bulletin from a toxicology lab while others are from textbooks in the field. Two of these are 1- Aerosol Measurement: Principles, Techniques and Applications. Edited by Klaus Willeke and Paul A. Baron. Van Nostrand Reinhold, New York, 1993. 2- Fundamentals of Aerosol Sampling. Gregory D. Wight. Lewis Publishers, CRC Press, 1994. While more texts will be added to the listing, these both are useful books for the well equipped inhalation toxicology library. Prior newsletters and reports

Earlier issues and discussion topics have been compiled. The newsletters may be found at http://www.inhalation.net/newsletters.htm