Particle Size Determination of Tire-Tread Rubber in Atmospheric Dusts

Abstract

Abstract Ambient dust was sampled with an Andersen high volume sizing impactor within twenty feet of heavy traffic on the Akron expressway and analyzed for tread rubber by pyrolysis gas chromatography. Methods were developed for removing dust particles from the collection surface and preparing them for pyrolysis. Those particles which lie in the respirable range 1.1 to 7.0 microns constitute 25 to 40 per cent of the total by weight. The remainder is divided about equally between the size range above 7.0 microns (not respirable) and those below 1.1 microns, i.e., about one-third of the dust lies in each size category. The amount of tread rubber in these respirable dusts as determined by styrene, dipentene, and vinylcyclohexene in their pyrolyzates varied from 1.5 to 9.2 per cent with an overall average of 4.3 per cent. In the size range above 7.0 microns a high value of 13.1 per cent rubber was found with an average of 6.3 per cent. In terms of micrograms per cubic meter of suspended particulates in the respirable range 1.1 to 7.0 microns, the values for tread rubber ranged from 1.0 to 4.9 with an average of 2.6. The low potential for health hazards from this respirable dust can be appreciated from a comparison with safe levels (TLV's) for certain pollutants known to be highly toxic as follows: Beryllium—2, lead compounds—150, mercury alkyls—10, cristobalite—50.