es060547z_si_001.pdf (117.44 kB)
Status of Worker Exposure to Asphalt Paving Fumes with the Use of Engineering Controls
journal contribution
posted on 2006-09-15, 00:00 authored by R. Leroy Mickelsen, Stanley A. Shulman, Anthony J. Kriech, Linda V. Osborn, Adam P. RedmanSince 1996, industry, labor, and government have partnered
to minimize workers' exposure to asphalt fumes using
engineering controls. The objective of this study was to
determine the use after some years of experience and to
benchmark the effectiveness of the engineering controls
as compared to the current exposure limits. To accomplish
this objective, the current highway class pavers equipped
with controls to reduce asphalt fumes, occupational
exposure levels, and ventilation flow rates were monitored,
and a user acceptance survey was conducted. Personal
breathing-zone sampling was administered to determine
concentrations of total particulate matter (TPM) and benzene
soluble matter (BSM). Personal monitoring of workers
yielded a BSM arithmetic mean of 0.13 mg/m3 (95% confidence
limits (0.07, 0.43) mg/m3). All site average worker BSM
values are below the American Conference of Governmental
Industrial Hygienists (ACGIH) adopted threshold limit
value (TLV) time weighted average (TWA) of 0.5 mg/m3 as
benzene soluble inhalable particulate, although five sites
contained 95% confidence limits slightly above the ACGIH
TLV. The TPM arithmetic mean was 0.35 mg/m3 (95%
confidence limits (0.27, 0.69) mg/m3). All sites showed
average worker and area TPM values below NIOSH's
recommended exposure limit for asphalt fumes (5 mg/m3,
15 min). One screed area sample and one operator area
sample were also taken each day. Area samples followed
a similar pattern to the worker breathing zone samples, but
were generally slightly higher in TPM and BSM concentration. The effect of work practices and application
temperatures appears to have an impact on the ability of
the engineering controls to keep exposure below the
TLV for BSM. To gain a better understanding of the
aerodynamic properties of asphalt fumes, particle size
and airborne concentrations were also monitored using a
TSI model 3320 aerodynamic particle sizer spectrometer.
The geometric mean particle size was between 0.64 and 0.98
micrometers for the worker breathing zone samples,
with a geometric mean of 0.73 micrometers for all sites.
Total airborne concentrations were typically higher for the
asphalt fume exposed groups than for the background
samples. During high fume events, four 15-minute samples
were taken each day. Only one 15-minute sample was
above the limit of quantification. Stack flow rates were
measured, and results are discussed and compared to the
manufacturers' nominal values. Survey results were
generally positive, with recommendations discussed for
continuous improvement.
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engineering controlsworker breathing zone samplesTSI model 3320stack flow ratesACGIHNIOSHconfidencescreed area sampleventilation flow ratesuser acceptance surveyAsphalt Paving Fumesthreshold limit valueworker BSM valuesarea TPM valuesTLVparticle sizemghighway class paversTWAsiteconcentrationasphalt fumesparticle sizer spectrometeroperator area sampleGovernmental Industrial Hygienistsexposure
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