Toxicity of wide-range polarity fractions from wood smoke and diesel exhaust particulate obtained using hot pressurized water.

Epidemiological and toxicological studies correlate the adverse health effects of particulate matter (PM) with the available information regarding their chemical characterization, which has focused on nonpolar organics (e.g., polycyclic aromatic hydrocarbons [PAHs]), which are limited to 15 to 50% of total organic carbon. To study both polar and nonpolar species, we have employed hot pressurized (liquid) water for the fractionation of diesel exhaust and wood smoke PM. In agreement with the results of previous studies, nonpolar fractions from both PM samples showed strong cytotoxicity (cell viability decreased to 50-60%) corresponding to the presence of PAHs. Surprisingly, similar decreases in cell viability were also found in polar fractions (50 degrees C) from both diesel exhaust and wood smoke PM. The midpolarity fractions (100-150 degrees C) from wood smoke PM also displayed high cytotoxicity corresponding to methoxyphenols and oxy-PAHs. Although the midpolarity fractions from diesel exhaust PM showed no cytotoxicity, genotoxicity was found in the 150 degrees C fraction, possibly corresponding to nitroaromatics. The present study demonstrates the suitability of hot pressurized water (as a single, nontoxic solvent) for the fractionation and toxicological characterization of wide-range polarity constituents of PM and, possibly, other environmental matrices.

Subcritical (hot/liquid) water dechlorination of PCBs (Aroclor 1254) with metal additives and in waste paint.

No disposal option exists for "mixed wastes" such as paint scrapings that are co-contaminated with polychlorinated biphenyls (PCBs) and radioactive metals. Either removal or destruction of the PCBs is required prior to disposal. Comparison of subcritical water dechlorination (350 degrees C, 1 h) of Aroclor 1254 in paint scrapings (180 ppm) and of standard Aroclor 1254 showed significantly enhanced dechlorination in the presence of paint. While no significant degradation was observed for standard Aroclor (no paint), the dechlorination of PCBs in paint was 99, 99, and 80% for the hepta-, hexa-, and pentachlorinated congeners, respectively, indicating that metals in the paint enhanced the dechlorination reactions. Adding metals to the standard Aroclor (no paint) reactions enhanced PCB dechlorination in subcritical water in descending order of activity: Pb approximately = Cu > Al > Zn > Fe. In the presence of both zerovalent and divalent lead and zerovalent copper in subcritical water (350 degrees C, 1 h), 99% of the Aroclor 1254 mixture (tetra- to heptachlorinated biphenyls) was dechlorinated. High dechlorination (ca. 95%) was also achieved with zerovalent aluminum. In contrast to other metals, lead retained its degradation ability at a lower temperature of 250 degrees C after 18 h. The high degradation efficiency achieved using metal additives in water at reasonable temperatures and pressures demonstrates the potential for subcritical water dechlorination of PCBs in paint scrapings and, potentially, in other solid and liquid wastes.