Larry T. Cupitt

MS/MS analysis of the products of toluene photooxidation and measurement of their mutagenic activity

Products of the photooxidation of toluene from an irradiated 5.1 ppm toluene/0.9 ppm NO/sub x/ mixture were identified by use of a triple-quadrupole MS/MS operated in an atmospheric pressure ionization mode. The reaction was carried out in a flow-mode 22.7-m/sup 3/ Telfon smog chamber. The steady-state reactant and product mixture was continuously transferred to the mass spectrometer inlet at 144 L/min. By using structurally similar standards, semiquantitative MS/MS analyses for many of the ring fragmentation products were conducted. Quantitative analyses by chromatographic methods and semiquantitative analyses by MS/MS were conducted for a variety of ring fragmentation products. The following products were found with yields of 1% (C/C) or greater: methylglyoxal, glyoxal, benzaldehyde, methylbutenedial, hydroxy-methylbutenedial, peroxyacetyl nitrate, oxoheptadienal, CH/sub 3/COOH, HCHO, hexadienal, and hydroxyoxo-heptadienal. The mutagenic activity of the steady-state product mixture was measured by using the Ames assay Salmonella typhimurium strain TA 100. The mutagenic activity data are discussed relative to our earlier findings that resulted from different reaction conditions.

Acetaldehyde: the mutagenic activity of its photooxidation products

The authors exposed Salmonella typhimurium strain TA100 to the gas-phase products of the photooxidation of acetyldehyde by using the effluent from a flow-mode smog chamber. The total mutagenic activity of the photooxidation products under simulated atmospheric reaction conditions was measured. Significant mutagenic activity was observed when the reaction time was long and considerable concentrations of ozone and organic peroxy-type products were present and when the reaction time was short and the major products were formaldehyde and peroxyacetyl nitrate (PAN). The photoxidation of acetaldehyde is shown to account for a significant fraction of the mutagenic activity observed from the photooxidation of propylene. It was found that most of the observed response can be accounted for by the presence of PAN in the reaction chamber. The apparent mutagenic activity of PAN in the reaction chamber. The apparent mutagenic activity of PAN in these experiments was found to be considerably larger than in previous laboratory measurements. 12 references, 4 tables, 2 tables.

Wood smoke: measurement of the mutagenic activities of its gas- and particulate-phase photooxidation products

Dilute mixtures of wood-combustion emissions (with and without additional NOx) were irradiated in a 22.7-m3 Teflon smog chamber. The effluent was tested for mutagenic activity by exposing Salmonella typhimurium, strains TA100 and TA98, to the filtered gas-phase components. The particulate matter was tested by using the plate incorporation procedure. Without added NOx, irradiated dilute wood smoke showed a measurable increase in mutagenic activity for gas-phase products only. Additional NOx was added in other irradiations to enhance the formation of gas- and particulate-phase products.

Mutagenic activity of irradiated toluene nitrogen oxide (NOx)/water/air mixtures.

Irradiated mixtures of toluene/NO/sub x//H/sub 2/O/air were brought to a steady-state distribution of reactants and products in a 22.7 m/sup 3/ flow-mode smog chamber, and the effluent was tested for mutagenic activity by exposing Salmonella typhimurium strains TA100 and TA98 to it. Two different product distributions were examined, with that corresponding to a longer extent of reaction yielding a greater mutagenic response. Vapor-phase concentrations for several aldehydes, cresols, peroxyacetyl nitrate, toluene, nitrogen oxides, ozone, and particulate matter were obtained for the reaction chamber and exposure chamber air masses. Calculations were made as to the total quantity of each product species that deposited into the biotesting medium. This information was used to speculate on what may have caused the mutagenic response.

Mutagenic activity of the products of propylene photooxidation

The reactants and products in irradiated propylene/NO/sub x/ mixtures were brought to a steady-state distribution in a Teflon smog chamber operated in a dynamic mode. The effluent from the chamber was then tested for total mutagenic activity by exposing Salmonella typhimurium strain TA100 to it. The data show an increased mutagenic activity for the products when compared with the reactants and controls. In addition, the mutagenic activity at long reaction times is substantially greater than at short reaction times. To examine a subset of the propylene/NO/sub x/ photooxidation products, an exposure of strain TA100 to the products of the propylene/N/sub 2/O/sub 5/ dark reaction was conducted. Although a small mutagenic activity was observed for this mixture, a number of mutagenic organic nitrates were identified. The results for the irradiated propylene/NO/sub x/ mixture were analyzed in terms of the mutagenic activities of the individual products. The major products (carbon monoxide, ozone, formaldehyde, acetaldehyde, nitric acid, and peroxyacetyl nitrate) account for no more than 20% of the observed mutagenic response, assuming additivity.

The mutagenic activity of the products of ozone reaction with propylene in the presence and absence of nitrogen dioxide

This study was performed to determine if propylene reaction with ozone could account for the large mutagenic activity we have observed in irradiated propylene/NO/sub x/ mixtures. In a 22.7-m/sup 3/ flow mode smog chamber, 5.4 ppm of propylene was allowed to react with 0.9 ppm of ozone either in the presence or in the absence of 0.2 ppm of nitrogen dioxide (at 25 /sup 0/C in the dark). The steady-state reactant and product distribution was then tested for total mutagenic activity by exposing Salmonella typhimurium strain TA100 to the gas-phase chamber effluent. The total product dosage in the test plates was varied by exposing them for 0, 5, 10, 15, and 20 h. Salmonella typhimurium survivor levels were obtained at each length of exposure. The number of revertants per plate increased at a rate of approx. 4-5 per hour, while the survivor level decreased throughout the exposure. Most of the total mutagenic activity can be accounted for by the presence of formaldehyde. The total mutagenic activity observed was, however, much smaller than that observed in the irradiated propylene/NO/sub x/ system, for comparable amounts of propylene consumed.