The effect of mercury emissions from contaminated soil at natural gas distribution stations is presented. The effects were estimated as part of a risk assessment that included inhalation and multimedia exposure pathways. The purpose of the paper is to illustrate the importance of dispersion modeling in the risk assessment process.

Results of the assessment indicate that inhalation dose intake driven by dispersion calculations and mercury vapor emissions could be an important part of the total risk, ranging from about 8% to 50% depending on whether the vapor emissions are based on measurements or calculations.

The calculated inhalation exposure levels were refined based on measured mercury flux levels that were consistently lower than the calculated values (e.g., the 50th and 90th percentile mercury flux values derived from field measurements were lower than the corresponding calculated values by a factor of 16 and 3.9. respectively). Such refinements affected the inhalation risk levels and, subsequently, the multimedia risk to workers and the public showing the importance of obtaining reliable emission estimates of mercury flux for use in the dispersion modeling.

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