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A diffusion ame system was used to generate an aerosol of soot and iron oxide. The primary fuel was ethylene. Iron was introduced by passing ethylene over liquid iron pentacarbonyl. The aerosol emission from the ame was diluted by secondary air to a level that could be used in animal exposure studies. The system was designed to operate at a constant soot production rate while the iron loading was varied from 0 to 50 ¹g m 3 in the diluted post ame gases. The impact of the iron on soot production was counteracted by the addition of acetylene to the fuel. Particles were collected on carbon grids and were examined via transmission electron microscopy. Electron energy loss spectroscopy was employed to characterize the aerosol. A differential mobility analyzer was used to measure the size distribution of the aerosol. The iron particles were typically 40 nm in diameter and often appeared in isolation from the soot aerosol, suggesting that either they were not formed concurrently with the soot or they remained after oxidation of the surrounding soot. Samples collected from within the ame, and downstream of the ame, indicated that the iron may have been present as very small particles comingled with the soot. The iron particles apparently melted and coalesced as they passed through the high temperature ame tip. Crystallization of the iron proceeded as the post ame gases cooled by mixing with external air. The ame system was shown to be capable of consistently producing steady concentrations of soot and iron for delivery to animals, without the confounding presence of toxic gaseous compounds.

Conventional chemical analyses of incineration by-products identify compounds of known toxicity but often fail to indicate the presence of other chemicals that may pose health risks. In a previous report, extracts from soot aerosols formed during incomplete combustion of trichloroethylene (TCE) and pyrolysis of plastics exhibited a dioxinlike response when subjected to a keratinocyte assay. To verify this dioxinlike effect, the complete extract, its polar and nonpolar fractions, some containing primarily halogenated aromatic hydrocarbons, were evaluated for toxicity using an embryo assay, for antiestrogenicity using primary liver cell cultures, and for the ability to transform the aryl hydrocarbon receptor into its DNA binding form using liver cytosol in a gel retardation assay. Each of these assays detect dioxinlike effects. Medaka (Oryzias latipes) embryos and primary liver cell cultures of rainbow trout (Oncorhynchus mykiss) were exposed to concentrations of extract ranging from 0.05 to 45 micrograms/l. Cardiotoxicity with pericardial, yolk sac, and adjacent peritoneal edema occurred after exposure of embryos to concentrations of 7 micrograms/l or greater. These same exposure levels were associated with abnormal embryo development and, at the higher concentrations, death. Some of the fractions were toxic but none was as toxic as the whole extract. In liver cells, total cellular protein and cellular lactate dehydrogenase activity were not altered by in vitro exposure to whole extract (0.05-25 micrograms/l). However, induction of cytochrome P4501A1 protein and ethoxyresorufin O-deethylase activity occurred. In the presence of whole extract, estradiol-dependent vitellogenin synthesis was reduced. Of the fractions, only fraction 1 (nonpolar) showed a similar trend, although vitellogenin synthesis inhibition was not significant. The soot extract and fractions bound to the Ah receptor and showed a significantly positive result in the gel retardation/DNA binding test. Chemical analyses using GC-MS with detection limits for 2,3,7,8-tetrachlorodibenzo-p-dioxin and dibenzofuran in the picomole range did not show presence of these compounds. Our results indicate that other chemicals associated with TCE combustion and not originally targeted for analysis may also pose health risks through dioxinlike mechanisms.ImagesFigure 1.Figure 2.Figure 3. AFigure 3. BFigure 4. AFigure 4. BFigure 4. CFigure 4. DFigure 5.Figure 6.Figure 7.

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A microwave-induced, steam/Ar/O 2 , plasma "torch" was operated at atmospheric pressure to determine the feasibility of destroying volatile organic compounds (VOCs) of concern. The plasma process can be coupled with adsorbent technology by providing steam as the fluid carrier for desorbing the VOCs from an adsorbent. Hence, N 2 can be excluded by using a relatively inexpensive carrier gas, and thermal formation of oxides of nitrogen (NO x ) is avoided in the plasma.