Environ. Sci. Technol. 1987,21, 568-573
Hesselink, F. Th. In Adsorption from Solution at the SolidlLiquid Interface; Parfitt, G. D.; Rochester, C. H., Eds.; Academic: New York, 1983; pp 377-412. Fleer, G. J.; Lyklema, J. In Adsorption from Solution at the SolidlLiquid Interface; Parfitt, G. D.; Rochester, C. H., Eds.; Academic: New York, 1983; pp 153-220. Bresinger, K. E.; Lemke, A. E.; Smith, W. E.; Tyo, R. M. J. Water Pollut. Control Fed. 1976, 48, 183-187. Letter and data submitted to US. Environmental Protection Agency; Petrolite Corp., Tretolite Division; 1982, St. Louis, MO (Fed. Reg. 1982,47, 33924-33948, August 4).
(8) Karickhoff, S. W.; Brown, D. S.; Scott, T. A. Water Res. 1979,13, 241-248. (9) Chiou, C. T.; Peters, L. J.; Freed, V. H. Science (Wash-
ington, D.C.) 1979, 206, 831-832. (10) Cohen Stuart, M. A.; Scheutjens,J. M. H. M.; Fleer, G. J. J. Polym. Sci., Polym. Phys. Ed. 1980, 18, 559-573. (11) Perrine, T. D.; Landis, W. R. J.Polym. Sci., Part A-1 1967,
5 , 1993-2003.
Received for review March 7,1986. Accepted December 4,1986. This work was supported by the U S . Environmental Protection Agency, Contract 68-02-3968.
Allyl Chloride: The Mutagenic Activity of Its Photooxidation Products Paul B. Shepson," Tadeusz E. Kleindlenst, Chris M. Nero, and Dennis N. Hodges Northrop Services, 1nc.-Environmental
Sciences, Research Triangle Park, North Carolina 27709
Larry T. Cupitt Atmospheric Sciences Research Laboratory, US. Environmental Protection Agency, Research Triangle Park, North Carolina 2771 1
Larry D. Claxton Health Effects Research Laboratory, US. Environmental Protection Agency, Research Triangle Park, North Carolina 277 11
Irradiations of C3H5Cl/N0,, C3H5CI/C2H6/N0,, and C2H6/N0, mixtures were conducted in a 22.7-m3Teflon smog chamber, operated in a static mode. The irradiated mixtures were tested for mutagenic activity by periodically exposing Salmonella typhimurium strain TAlOO to the smog chamber effluent during the irradiation. The allyl chloride photooxidation products' total mutagenic activity was found to be dramatically dependent on the presence of C1 atom reaction products. In the absence of C2H6, which is used as a CI atom scavenger, the observed mutagenic activity of the irradiated C3H5C1/N0, mixture at long extent of reaction was 13 revertants.plate-'.h-l.(ppb C3H6CIconsumed)-'. However, when sufficient C&&was present to remove all C1 atoms, the observed mutagenic activity for C3H&1 photooxidation products was 1.4 revertants.plate-l.h-'.(ppb C3H5Cl consumed)-'. Under conditions of excess CzHs, the mixture is approximately 30 times more mutagenic than that previously observed for the mutagenic activity of the photooxidation products of propylene, the nonchlorinated analogue of allyl chloride. The observed mutagenic activity in the presence of excess C2H6 is consistent with the total response caused by chloroacetaldehyde, a primary C3H5Cl photooxidation product I
Introduction
As part of a long-term research effort aimed a t identifying mechanisms for the production of hazardous species in the atmosphere through reactions of OH, 03,and NO3 with reactive pollutants, we have reported that simple atmospheric hydrocarbons can be converted into mutagenic products through atmospheric photochemistry (1-3). In these studies we demonstrated that through reaction with the hydroxyl radical and in the presence of oxides of nitrogen (NO,), nonmutagenic hydrocarbons, such as acetaldehyde, can be converted into mutagenic products ( 4 ) , such as peroxyacetyl nitrate (PAN), as determined with the Ames test. Although most of the reactive hydrocarbon concentration in urban atmospheres is represented by carbon- and 568
Environ. Sci. Technol., Vol. 21, No. 6, 1987
hydrogen-containing (only) organic compounds, there are
a variety of chlorinated solvents present as well that can play a role in urban photochemistry. Many of these chlorinated hydrocarbons (including allyl chloride) are considered hazardous air pollutants (HAPs) and are currently being considered for regulatory action (5) because of their potential human health effects. Although HAPs, by definition, are considered to have some potential human health effects, it is possible that many of the chlorinated HAPs can be converted to products that are more (or less) mutagenic than the reactant HAP. For some oxygenated species, the chlorine-substituted analogues are more mutagenic. For example, chloroethylene oxide (a possible oxidation product of vinyl chloride) is 10000-15 000 times more mutagenic than is ethylene oxide (6). As a first step in investigating the potential for production of mutagenic products as a result of the photooxidation of chlorinated hydrocarbons, we report the results of a series of exposures of the bacteria Salmonella typhimurium, strain T A W (without metabolic activation), to the photooxidation products of allyl chloride (3chloropropene). This particular HAP was chosen in large part due to the fact that it is the chlorinated analogue of propylene, a hydrocarbon that we previously studied in detail regarding its mutagenic photooxidation products (2). Our previous experience with propylene, along with the fact that the chemical mechanism and reaction kinetics for allyl chloride are now fairly well understood (7), should facilitate the identification of individual mutagenic products for this HAP. In this paper we report the results of four static-mode smog chamber irradiations of C3H5Cl/ NO, and C3H5C1/C2H6/N0, mixtures, in which S. typhimurium was periodically exposed to the chamber effluent during the reaction profiles. Since the photooxidation of allyl chloride proceeds through OH and C1 atom chain reactions (7), the experiments with ethane were conducted to enable measurement of the mutagenic activity of the allyl chloride photooxidation products in the presence and absence of C1 atom reaction products. The results of these experiments will be interpreted in terms of the dependence of the observed mutagenic activities on the reaction con-
0013-936X/87/0921-0568$01.50/0
@ 1987 American Chemical Society
ditions, particularly in terms of the extent of C1 atom reactions.
Experimental Methods The photochemical reaction chamber and exposure system used for measuring the mutagenic activity of photochemical reaction products have been described in detail previously ( 1 , 2 )and are only briefly described here. Because of the magnitude of the observed mutagenic activity, it was possible to conduct these experiments with the chamber operated in a static mode, i.e., as a conventional smog chamber, rather than in a dynamic mode, which was used in our previous studies with propylene (2). This enabled the determination of mutagenicity profiles as the reaction proceeded. In these experiments, clean dilution air was continuously added to the reaction chamber at -18 L/min (-4.8% dilution per hour). The chamber effluent was then allowed to flow at 14 L/min through a 190-L exposure chamber, as described previously (1-3). The experiments were conducted by first adding the appropriate volumes of mixtures of 1% allyl chloride in Nz and of 1% NO in Nz and pure CzH6(all from MG Scientific) to a 22.7-m3Teflon smog chamber. The reaction chamber is surrounded longitudinally with a combination of sunlamps and black lights. Once the reactant concentrations were brought to the desired initial levels, the reaction chamber air was made to flow through the effluent exposure chamber at 14 L/min. The exposure chamber was loaded with 10 test plates (and one survivor plate) that contained 5'. typhimurium strain TA100. Once the exposure chamber was adequately flushed, an initial reactants mixture exposure was conducted by uncovering seven of the test plates for either 15 or 30 min (with the chamber dark). Three of the test plates remained covered as controls during each exposure period. After the reactants exposure period, the plates were removed, and the exposure chamber was reloaded with ten test plates and one survivor plate. At this point, the reaction chamber lights were turned on, initiating the reaction. The experiments were conducted at 25 f 2 "C, and the chamber air relative humidity was 110%. For each of the four experiments (A--D), there were five exposure periods of 5-30-min duration (i.e., the plate covers were removed for 5-30 min) during the irradiation. For two of the experiments (A and B), the plate exposure duration was decreased as the reaction proceeded to avoid toxicity effects. For each exposure period, there were ten test plates and one survivor plate, which was used to indicate the possible presence of toxicity effects (3,8).Between each exposure period, the exposed plates were removed, and the exposure chamber was reloaded with unexposed test plates, followed by a period of time sufficient for the exposure chamber to be adequately flushed. As described elsewhere (2, 8), the exposure of the bacteria to the products relies on the deposition of the soluble product species into the test medium as the product mixture flows through the exposure chambers. A clean air exposure chamber was used as a control for these experiments. This exposure chamber contained 35 test plates and 5 survivor plates, all of which were exposed throughout the irradiation period (-6-12 h). At the end of the reactiqn chamber irradiation, the covered plates were removed from the exposure chambers and incubated at 37 "C for -60 h to enable colony growth. At this point the final revertant and survivor colonies were counted. The bioassay test procedures employed were essentially those of Ames et al. (9). The test plates were prepared by adding 0.1 mL of the S . typhimurium culture to 3 mL of an agar overlay a t 45 "C. This mixture was then poured
onto 45 mL of minimal histidine concentration agar in a Pyrex Petri plate. Colony counting was done with an Artec 880 automatic colony counter with previously published guidelines (10). During the irradiations, we periodically measured the reactant and product concentrations in the smog chamber. The sampling and analysis procedures for measuring NO, NO,, and O3 have been described previously (1). Allyl chloride and its photooxidation products 1,3-dichloroacetone and chloroacetaldehyde were also measured chromatographically as described previously (7). Ethane was separated and detected in a Gow Mac Series 750 gas chromatography(FID) containing a 2 m X 3.2 mm stainless steel column packed with 60/80 Carbosieve G, operated isothermally at 175 "C. Sample injection for allyl chloride and ethane was achieved with Seizcor gas-samplingvalves with 5-cm3sample loops. Formaldehyde, acetaldehyde, glyoxal, and acrolein were measured by a 2,4-dinitrophenylhydrazine (DNPH) technique as described by Edney et al. (7). Peroxyacetyl nitrate (PAN) and chloroperoxyacetyl nitrate (CPAN) were measured by bubbling 30-L chamber samples through 5 cm3 of pH 12 deionized water, which converts these species to acetate or chloroacetate ions, respectively. The basis for this procedure for PAN determination has been described by Grosjean et al. (11). The ions were then separated and detected in a Dionex System 10 ion chromatograph containing a Dionex HPICE AS2 column and using M HC1 eluent. In this paper we present the results of four irradiations and associated exposures (experiments A-D). For all experiments, the initial NO and NO2 concentrations were -350 and 115 ppb, respectively. For the first two experiments (A and B), the initial allyl chloride concentrations were -725 ppb. In experiment B, we also added -11 ppm CzH6,which had no significant effect on the overall reaction rate (see Results). The light intensity was identical for experiments A and B (we estimate the rate constant for NOz photolysis to be -0.2 min-l). For experiments C and D the initial ethane concentration was 150 ppm, and the overall reaction rate was therefore dominated by OH reaction with ethane. Experiment C contained no allyl chloride, and in experiment Il the initial allyl chloride concentration was 850 ppb. The irght intensity was identical for experiments C and I)but was 0.4 times that used for experiments A and B (we estimate the From NOz photolysis rate constant to be -0.08 min the results of these experimentswe attempted to determine the mutagenic activity of the products of OH (and 03) reaction with allyl chloride as compared with the mutagenic activity of the C1 atom reaction products The results of these experiments are then discussed in terms of those products that may have caused the observed mutagenic activity.
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Results The results for experiments A D are presented in Figures 1-4, respectively, which include concentration data for the reactants and some of the major products (e.g., PAN) for each exposure. The Ames assay data ( f l SD) are also included in these plots for the effluent exposure chamber as revertants per plate per 15-min exposure (Figures 1 and 2) or revertants per plate per 30-min exposure (Figures 3 and 4). The clean air exposures (which lasted the duration of the irradiations) yielded 180 f 21, 212 f 14, 220 f 10, and 194 f 17 revertants per plate for experiments A-D, respectively. For experiment A (irradiated allyl chloride/NO,), the first three exposure periods lasted 15 min. However, experiments we performed previously under essentially identical reaction conditions inEnviron. Sci. Technol., Vol. 2 1 , No. 6, 1987
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