Collection of BURA fume condensates was more complicated
because there were significant differences in temperature between
the kettle used to heat the asphalt (271 C, sd = 15) and the roof top
mop buckets used to apply asphalt to the roof (231 C, sd = 40).
This difference is common in the BURA industry due to cooling
during transport from the kettle to the roof top buckets. For each
of the four roofing asphalts studied, an equal mass aliquot of extract
from 13 rooftop IH samples and 3 kettle IH samples were
combined for analysis. This was done to reflect the approximate ratio
of kettle workers to workers on the roof (approximately (1:4).
The chemical characteristics of this combined sample were then
used to guide collection of the bioassay sample above the asphalt
tank, and for validating the bioassay sample. To provide a condensate
that chemically matched that of the average roofing worker
for the BURA sample, collection of fume condensates above the asphalt
tank occurred at an average temperature of 199oC (sd = 4.9).
The lab-generated BURA sample was generated at a temperature
of 232 C. This was well below the temperature of the asphalt
in the kettle that workers were exposed to, comparable to the temperature
of the mop bucket on the roof, but above the temperature
in the tank that was needed to match the chemistry of the fumes
emitted from the kettle and mop bucket. It matched the lower temperature
used by NIOSH for their lab generation of asphalt fumes
(Niemeier et al., 1988). Some of the analytical results for the test
materials used in this study are provided in Table 1; more detail
on the generation methods, characterization of the samples and
selection criteria are described in Kriech et al., 2007.