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/NOx mixtures. In a 22.7-m3 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 °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 <~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/NOx system, for comparable amounts of propylene consumed.