NOTES
An Experimental Evaluation of Atmospheric Nitrosamine Formation William A. Glasson Environmental Science Department, General Motors Research Laboratories, Warren, Mich. 48090
I t has been suggested that carcinogenic nitrosamines can be formed in the atmosphere from ambient NO, and amines. A long-path infrared study of the reaction of dimethylamine, NO, and NO2 has been carried out at various parts per million levels of the reactants to test this suggestion. I t was found that low concentrations of dimethylnitrosamine were formed a t rates independent of the amine concentration. Further experiments showed that the amine was adsorbed on the cell walls and that nitrosamine formation was probably proceeding heterogeneously. Using the data of this investigation and the results of a recent EPA study, it was shown that homogeneous nitrosamine formation in the atmosphere should not pose a significant health hazard, although further work will be required to establish whether nitrosamine formation on aerosol surfaces could result in a significant health risk.
Table 1. Reaction of Dimethylamine, NO, and NO2 in Air a [DMAlb loss, ppm
[DMAIo, ppm
[Nolo, PPm
4.8 13.5
2.0
1.2
1.99
0.15
2.0
1.9
3.91
0.23
2.1 2.0 2.1 2.0 2.0
2.0 2.0
5.90 2.91 1.75 5.45 2.70
0.38
7.2 3.7 5.1 7.5= 4.OC
[N0210. ppm
2.0 1.9
2.0
[NDMA), ppm
0.15 0.15 0.20
0.26
Reactions carried out in the dark at 35 O C and 760 Torr total pressure for 100 to 400 min in cylinder air. Refers to DMA that disappeared from the gas phase. ‘Experiments carried out in the presence of 2200 ppm of added a
H20.
The discovery of the suspected carcinogen ( I ) dimethylnitrosamine (NDMA) in the atmosphere in several areas of the U S . ( 2 ) has led to concern that the reaction of ambient NO, with amines to form nitrosamines could pose a health hazard. Although it was shown that airborne NDMA was due to local chemical manufactwing processes in some of these areas, it has been suggested that automotive NQ, emissions should be reduced to minimize this possible health hazard ( 3 ) . A recent survey of several areas of the U S . ( 4 ) found nitrosamine in only one location. The level found was about 0.1 ppb. The Environmental Protection Agency (EPA) has studied the reaction of NO, and dimethylamine in air ( 5 ) . They found that NDMA does form, but that the rate of the reaction based on amine disappearance was too slow to be of importance in the atmosphere, considering the fact that NDMA rapidly photolyzes in sunlight. The EPA study was repeated in the present work to verify their conclusions about atmospheric NDMA formation.
Experimental The study was carried out in a long-path infrared cell (6) (3-m base path, 614-L multiple-reflection stainless steel) a t a temperature of 35 “C and a total pressure of 760 Torr. Dimethylamine was an Eastman Kodak product, and dimethylnitrosamine was a product of Chemical Procurement Laboratories. Nitric oxide was a Matheson product, while nitrogen dioxide was prepared on the vacuum line by the thermal oxidation of nitric oxide. The concentrations of NDMA and dimethylamine were determined by measuring their infrared absorptions a t 9.9 and 8.7 pm, respectively. Results a n d Discussion Various mixtures of dimethylamine (DMA),NO, and NO2 were reacted in the dark. The disappearance of dimethylamine and the formation of dimethylnitrosamine were studied. The results are given in Table I. In every experiment, NDMA was observed in substantially smaller amounts than the amount of dimethylamine lost. The NDMA formed amounted to an average of 6.3% of the lost amine in dry air and 7.3% in the presence of 2200 ppm of added H20. Examination of the corresponding concentration vs. time plots provides further insight into the chemistry of 0013-936X/79/0913-1145$01.00/0 @ 1979 American Chemical Society
3.7 DDm Dimethylamine 2.0 wrn NO
2.0 porn NO2
0
.-a
.-.-.-.
2w
Irn
3m
I
TIME Imin.1
Figure 1. Reaction of dimethylamine with nitrogen oxides: (0)dimethylamine; ( 0 )dimethylnitrosamine
NDMA formation in these systems. A typical plot is given in Figure 1. After an induction period of about 40 min, NDMA formation proceeds at a constant rate for the remainder of the reaction period, while the amine concentration decreases by about 80%. This behavior is inconsistent with that of a homogeneous gas-phase reaction. Rather, the data in Figure 1 are consistent with a mechanism involving adsorption of the amine on the cell walls, followed by NDMA formation and subsequent desorption. It was verified that dimethylamine adsorbs on the cell surfaces by carrying out a control experiment. The amine (10.2 ppm) was added to the cell, and the same rate constant for amine disappearance was observed independent of the presence or absence of added NO,. Thus, the amine adsorbs on the cell wall and then probably reacts with nitrous acid, formed from NO and NO2 dissolved in the water layer a t the surface (adsorbed from trace amounts of H20 in the cylinder N2 and 0 2 ) , according to Reaction 1: HNOz
+ (CH3)2NH
+
(CH3)zNNO + HzO
(1)
The nitrosamine then desorbs from the wall into the gas phase where it is detected. The constant rate of NDMA formation would then correspond to the rate of desorption. The “missing” amine undoubtedly is adsorbed on the walls either as the Volume 13, Number 9, September 1979
1145
amine, NDMA, or other (unknown) products. Grossly, the results of this investigation agree with those of the recent EPA study ( 5 ) .In that study, dimethylamine disappeared from the system while NDMA was formed. The EPA investigators did not calibrate their system for NDMA, but merely assumed that one molecule of NDMA was formed for every molecule of amine that disappeared. They did not investigate the possibility of heterogeneous reactions. The conclusion of their study stated that the rate of homogerieous NDMA formatioh in the atmosphere was insignificant, based on their rate data. Since the results of the present study have shown that NDMA formation occurs at only 6 to 7% of the rate of amine disappearance, these results not only support this conclusion, but also strengthen it. It is possible that nitrosamine formation could occur on the surface of airborne particulate matter, since the heterogeneous nature of the reaction has been demonstrated in the present study. In general, the low levels of atmospheric amines would tend to militate against this possibility. In local areas of high atmospheric amine content (sewage disposal plants, stockyards, etc.), this possibility cannot be completely disregarded. However, the results of a recent study (7) have shown negligible quantities of NDMA in the atmosphere of a sewagetreatment plant near Baltimore, Md.
Acknowledgment The author gratefully acknowledges the assistance of Dr. D. J. McEwen in carrying out the nitrosamine calibrations. Literature Cited (1) Magee, P. N., Barnes, J. M., Br. J . Cancer, 10,114 (1956). (2) Fine, D. H., Rounbehler, D. P., Belcher, N. M., Epstein, S. S., Science, 192,1328 (1976). (3) “Assessment of Scientific Information on Nitrosamines”, A Report of an ad hoc Study Group of the Environmental Protection Agency, Science Advisory Board, Executive Committee, August 1976. (4) Pellizzari, E. D., “The Measurement of Carcinogenic Vapors in Ambient Atmospheres”, Research Triangle Institute Final Report EPA-60017-77-055, June 1977. ( 5 ) Hanst, P. L., Spence, J. W., Miller, M., Enoiron. Sci. Technol., 11,403 (1977). (6) Tuesday, C. S., in “Chemical Reactions in the Lower and Upper Atmosphere”, Cadle, R. D., Ed., Interscience, New York, 1961, p 15. (7) Fine, D. H., Rounbehler, D. P., Rounbehler, A,, Silvergleid, A,, Sawicki, E., Krost, K., DeMarrais, G. A., Enuiron. Sci. Technol., 11,581 (1977).
Received for revieui August 1 , 1977. Resubmitted M a y 7, 1978. A c cepted June 20, 1979.
Organochlorine Insecticide Residues in Deep Sea Fish from 2500 rn in the Atlantic Ocean Richard T. Barber* Duke University Marine Laboratory, Beaufort, N.C. 28516
Stanley M. Warlen National Oceanic and Atmospheric Administration. National Marine Fisheries Service, Southeast Fisheries Center, Beaufort, N.C. 28516 ~~
Eleven organochlorine insecticide residues were measured in the livers of Antimora rostrata, a deep sea fish collected from 2500 m in 1972,1973, and 1974 off the east coast of the United States. Compounds present were p,p’-DDE, p , p ’ DDD, p,p’-DDT, o,p’-DDT, and dieldrin, while six compounds were not detectable. The ratio of p,p’-DDT to p , p ’ DDE decreased from 2.17 in 1972 to 1.00 in 1974. The mean concentration of total DDT residues in the fish livers for the entire period was 7.06 mg/wet kg, similar in magnitude to the concentration of DDT residues found in lipid-rich livers of Atlantic cod (Gadus rnorhua j from shallow waters of the Atlantic coast of Canada. Organochlorine insecticide residues have spread over the face of the globe to the extent that they are detectable in the biota of both poles. Initial analyses of one deep ocean fish by Teal ( I j and a few by Meith-Avcin et al. ( 2 ) reveal that the lipid-rich deep sea fish have detectable concentrations of some organochlorine compounds. A 1971 National Academy of Sciences report entitled “Chlorinated Hydrocarbons in the Marine Environment” ( 3 )predicted that 25% of all the organochlorine material produced would eventually enter the ocean; in the same year, Woodwell et al. ( 4 ) presented a global flux model that predicted the organochlorine concentrations in the atmosphere, ocean, and sediments through the end of this century. The Woodwell model ( 4j is now recognized as having some incorrect assumptions because of the limited data available a t that time, and modified predictions have been 1146
Environmental Science & Technology
made by Bidleman et al. ( 5 )and others using recent data. One theme of the NAS report and the Woodwell model ( 4 ) is that the deep ocean sediment will be the major final accumulation site of the organochlorine compounds that enter the atmosphere. The proportion of the total material that will reach this reservoir and the rate of degradation in seawater and sediments remain in doubt, but the importance of the deep ocean sediments as the final reservoir seems undisputed (5-7). Species of bathydemersal fish such as Antirnora rostrata are permanent residents of great depths, and they feed by rooting in the sediment for infaunal animals (8) and cropping epifaunal animals. These fish are exceptionally rich in lipids; the livers of Antimot-a rostrata are 85%lipid on a dry weight basis (7). Organochlorine compounds in the prey and in the sediment ingested along with prey would be partitioned into the lipid fraction of these long-lived and slowly metabolizing fish. Antimora rostrata is found throughout the world’s oceans a t depths of 1000 to 3000 m ( 9 - I I ) , and a t greater depths other species with similar lipid content and feeding habits are present. The final accumulation of organochlorine residues in deep ocean sediments and the properties of the fish living there suggest that the lipids of deep sea fish may be a reservoir that should be specifically considered in organochlorine flux models. This note reports the concentration of organochlorine insecticide residues in Antirnora rostrata collected from a single location on 3 successive years to document the insecticide levels present in this species of deep sea fish.
0013-936X/79/0913-1146$01.00/0 @ 1979 American Chemical Society
