PAC Exposure among Asphalt Workers

PI: Robert Herrick, ScD, Harvard School of Public Health
Co-Investigators: Michael McClean, ScD, BUSPH; Jennifer Cavallari, ScD, Harvard School of Public Health

ebrg_6This study investigates the relative contribution of inhalation and dermal exposure to the levels of Polycyclic Aromatic Compounds (PAC) and PAC metabolites in the urine of hot-mix asphalt paving workers. The need for such research was emphasized at the June 2006 International Health Symposium in Dresden Germany, where the true extent of dermal absorption and the relevant biomarkers of exposure were identified as data gaps. To fill this gap, a partnership was formed by researchers from a variety of disciplines, resulting in a study designed to determine the source, nature, pathway, and biological relevance of PAC exposure in hot-mix asphalt paving workers.

Because asphalt emissions occur during paving operations, the workers associated with this process can be exposed to PACs in a variety of ways; this study focuses on inhalation and dermal exposures, where the exposure route could be through the lungs, skin or consumption from sources found in food. We use a repeated measures panel study design to monitor each participant for three days over four different scenarios. Exposures are measured: 1) at baseline under routine paving conditions, 2) without the use of diesel oil (using a PAC-free biofuel substitute), 3) with the addition of respirators to control inhalation exposure, and 4) with the addition of protective clothing to control dermal exposure. Additionally, a control group of non-asphalt exposed construction workers (members of a concrete crew) is included for comparison to the asphalt exposed workers. Since smoking-related PACs are a confounder, smoking is accounted for in the analyses by measuring cotinine levels in each urine sample. Urine cotinine measurements capture both direct and second hand cigarette smoke exposures.

We are investigating the sources of PACs present in the work environment, and the biological relevance (absorbed dose) of these PACs by studying the metabolites present in workers’ urine. Both inhalation and dermal exposure to PACs are determined through detailed chemical, biological and physical analyses (gas, aerosol, particulate). By investigating the chemical make-up of inhalation and dermal exposure analytes and their resulting urinary metabolites, we will assess whether their source can be ascertained.

Publications

  • Cavallari JM, Osborn LV, Snawder JE, Kriech AJ, Olsen LD, Herrick RF, McClean MD. 2012. Predictors of airborne exposures to polycyclic aromatic compounds and total organic matter among hot-mix asphalt paving workers and influence of work conditions and practices. Ann Occup Hyg. 56(2): 138-47.
  • Cavallari JM, Osborn LV, Snawder JE, Olsen LD, Kriech AJ, Herrick RF, McClean MD. 2011. Predictors of dermal exposures to polycyclic aromatic compounds among hot-mix asphalt paving workers. Ann Occup Hyg. Published on-line December 8, 2011.
  • Cavallari JM, Zwack LM, Lange CR, Herrick RF, McClean MD. 2012. Temperature-dependent emission concentrations of polycyclic aromatic hydrocarbons in paving and built-up roofing asphalts. Ann Occup Hyg. Published on-line January 20, 2012.
  • Cavallari JM, Osborn LV, Snawder JE, Kriech AJ, Olsen LD, Herrick RF, McClean MD. 2011. Predictors of dermal exposures to polycyclic aromatic compounds among asphalt paving workers. 5th International Conference on Occupational & Environmental Exposure of Skin to Chemicals. June 5-8. Toronto, Canada.
  • Kriech AJ, Osborn LV, Snawder JE, Olsen LD, Herrick RF, Cavallari J, McClean MD, Blackburn GR. 2011. Study design and methods to investigate inhalation and dermal exposure to polycyclic aromatic compounds and urinary metabolites from asphalt paving workers: Research conducted through partnership. Polycyclic Aromatic Compounds. 31(4): 243-269.
  • McClean MD, Kelsey KT, Sison JD, Quesenberry CP, Wrensch MR, Wiencke JK. 2011. A case-control study of asphalt and tar exposure and lung cancer in minorities. Am J Ind Med. 54: 811-18. PMCID: PMC3196745
  • Osborn LV, Snawder JE, Olsen LD, Kriech AJ, Cavallari J, Herrick RF, McClean MD, Blackburn GR. 2011. Pilot study for the investigation of personal breathing zone and dermal exposure using levels of polycyclic aromatic compounds (PAC) and PAC metabolites in the urine of hot-mix asphalt paving workers. Polycyclic Aromatic Compounds. 31(4): 173-200.
  • Sobus JR, Pleil JD, McClean MD, Herrick RH, Rappaport SM. 2010. Biomarker variance component estimation for exposure surrogate selection and toxicokinetic inference. Toxicol Lett. 199: 247-253. PMCID: PMC2998189.