Ambient air quality at the site of a former manufactured gas plant

Prior to the 1950's, manufactured gas was commercially produced from the py rolysis of coal, coke, and oil at facilities that are termed manufactured g as plants (MGPs). The constituents of residual coal tar present on many MGP sites are an environmental health concern because of their toxicity and th e possibility for their off-site migration via water and air. Atmospheric c oncentrations of five volatile organic compounds (VOCs, e.g., benzene), six teen polycyclic aromatic hydrocarbons (PAHs, e.g., naphthalene), and partic ulate matter less than 10 microns in aerodynamic diameter (PM10) were measu red at the site of a former MGP. Air samples were obtained before, during, and after excavation of subterranean coal tar at the site. The results of t his investigation indicate that subterranean coal tar was not a primary sou rce of VOCs and PAHs in the local atmosphere before or after remediation of the site. However, excavation, treatment, blending, and transfer of the co al tar during remediation generated concentrations of selected aromatic and semi-volatile organic compounds that were substantially greater than typic al ambient levels. In addition, these data suggest that blending and mixing of coal tars could lead to exceedance of the U.S. National Ambient Air Qua lity Standard for PM10, although additional research is required to fully e valuate this possibility. Nuisance odors associated with the site remediati on were likely the result of naphthalene and possibly isomers of xylene. Ai r pollutant concentrations measured adjacent to the excavation area and at the site perimeter during remediation activities were less than the relevan t occupational and environmental exposure limits.