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Risk Assessment – Airborne Emissions

Risk Assessment – Airborne Emissions. Asphalt fumes. 4 3 2 1 0. log B(a)P exposure ( ng /m3). 0 1 2 3 4 log B(a)P binder content (mg/kg). Modified from Burstyn and Kromhout . Risk Analysis 2000. Variable and complex exposure

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Risk Assessment – Airborne Emissions

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  1. Risk Assessment – Airborne Emissions

  2. Asphaltfumes 4 3 2 1 0 log B(a)P exposure (ng/m3) 0 1 2 3 4 log B(a)P binder content (mg/kg) Modified from Burstyn and Kromhout. Risk Analysis 2000 Variable and complex exposure • Climate, (wind speed and direction, temp etc) • Work tasks (pavers, screedmen, rakers, rollers etc) • Ambient environment (tunnel paving, open paving etc) • Asphalt application (type, temp, protective measures etc)

  3. Asphaltfumes 4 3 2 1 0 log B(a)P exposure (ng/m3) 0 1 2 3 4 log B(a)P binder content (mg/kg) Modified from Burstyn and Kromhout. Risk Analysis 2000 Variable and complex exposure • Climate, (wind speed and direction, temp etc) • Work tasks (pavers, screedmen, rakers, rollers etc) • Ambient environment (tunnel paving, open paving etc) • Asphalt application (type, temp, protective measures etc) Large occupational exposure datasets necessary to enable identification of bitumen fume quantity and quality in relation to asphalt constituents

  4. Asphaltfumes Variable and complex exposure • Climate, (wind speed and direction, temp etc) • Work tasks (pavers, screedmen, rakers, rollers etc) • Ambient environment (tunnel paving, open paving etc) • Asphalt application (type, temp, protective measures etc) Variable and complex chemical composition • Asphalt constituents (type, temp, RA, additives) • Metric under examination (TPM, BSM, TOC, SVOC, PAH etc) • Sampling device (type, rate, duration etc), • Analytical method (extraction, calibration etc) Variability in occupational exposure makes it difficult to relate fume emission and exposure to asphalt constituents

  5. Asphalt fume generator • Total emissions - TOC • Quantity of fumes is influenced by depletion • 1 mix Plant dryer/mixer • 1 nonmix Silo storage • 2 mix Transfer to truck • 2 nonmix Truck transport • 3 mix Transfer to paver • 3 nonmix Paver hopper • 4 mix Paver screed • 4 nonmix Pavement surface

  6. Asphalt fumes - Emissions • Quality and quantity of fumes related to extent of depletion • Non-plant dryer/mixer related emission can be substantial • Lab. fume generator underestimates asphalt fume emission - and depletion

  7. Asphalt fumes - Emissions • Non-plant dryer/mixer related emission can be substantial • Laboratory fume generator underestimates asphalt fume emission • Lab. fume generator underestimates asphalt fume emission - and depletion • Health hazard for paving crews

  8. Asphalt fumes - Hazards • Benzene-Soluble particulate Matter (BSM) – frequent OEL at 0.5 mg/m3 (TWA) • Lab fume generator concentration overstates exposure by a factor of 3 • SBS modified binder increases the BSM emission by a factor of 8 -increasing the risk of exceeding BSM OEL

  9. Asphalt fumes - Hazards • Tar RA occupational exposure measurements extremely variable • Estimated paving fume generator concentrations for Tar RA fairly stable and dependent on degree of contamination • Estimated Tar RA paving laboratory fume concentration overstates exposure (by a factor of ?) • Tar contaminated RA exceeds frequent BSM OEL

  10. Conclusions Bitumen fumes • Fume generator enables identification of bitumen fume quantity and quality in relation to asphalt constituents - Input to LCA and Risk assessment. • RA does not change total emission of bitumen fumes but quality of fumes • SBS modified bitumen increases occupational hazard • Tar contaminated RA exceeds occupational exposure limit • Modify sequential mixing protocol to improve consistency with field data (higher emission per kg asphalt) • More calibrations of lab fume generator vs. field needed

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