Environ. Sci. Technol. 1983, 17, 57-58
did not occur for any values among the normal adult, child or elderly population groups. This is not surprising since few human studies of the effect of acute exposure to nitrogen dioxide have been performed, and these have usually tested respiratory function rather than clinical response,” I t has also been reported that the “World Health Organization Task Group on Environmental Health Criteria for Oxides of Nitrogen concurred on the 0.5 ppm adverse effects level and stated further that 0.1 to 0.17 ppm no more than once a month was consistent with protection of the public health” (25). An additional health aspect of photochemical smog is that not just O3 and NOz but also a spectrum of gaseous and particulate noncriteria pollutants are inhaled (9). These, though present in much lower concentrations, may have disproportionately large health impacts. The atmospheric levels of a number of these compounds are directly related to NO, emissions. Nitrous acid is a key example and, as noted above, on Aug 8,1980, we showed that its ambient concentrations near DTLA exceeded 6.5 ppb for the entire period 0200-0700, peaking at -8 ppb at 0500 (12). At present the health effects of inhaled nitrous acid vapor are not known. Also important is the fact that increased NO, emissions may also lead to higher levels of a spectrum of nitroarenes present on combustion-generated particulates. Certain of these nitropolycyclic aromatic hydrocarbons are strong direct mutagens in the Ames Salmonella typhimurium reversion assay. One of them, l-nitropyrene, not only is a major contributor to the strong mutagenicity of extracts of diesel particulates (26,27) but also has recently been reported to be a strong animal carcinogen (27). Finally, Innes’ comments on the ecological impacts of nitric acid are so contrary to contemporary thinking and evidence [including very recent acid fog measurements in the CSCAB (19)]that they do not warrant discussion. Spicer’s recent experimental data (17))on the other hand, are highly relevant to this issue. He states “There is an obvious linear relationship between the two variables, suggesting that strategies to control nitric acid formation must be based on NO, emissions reduction. Limited reduction of organic emissions, a procedure used to control 03,will have little affect on the ultimate nitric acid concentration. Strategies which allow NO, emissions to increase as a means of inhibiting O3 formation will be detrimental due to increased downwind concentrations of HN03.” In conclusion, on the basis of the best available scientific evidence, we remain convinced that continued strict control of both NO, and HC is essential to protect both public health and the environment from a broad spectrum of impacts of photochemical smog; relaxation of NO, controls would be a grave error. Literature Cited (1) Glasson, W. A. J. Air. Pollut. Control Assoc. 1981,31,1169. (2) Chock, D. P.; Dunker, A. M.; Kumar, S.; Sloane, C. S. Enuiron. Sci. Technol. 1981, 15, 933. (3) Innes, W. B. Environ. Sci. Technol. 1981, 15, 904. (4) Pitts, J. N., Jr.; Winer, A. M.; Darnall, K. R.; Lloyd, A. C.; Doyle, G. J. Final Report to California Air Resources Board Contract No. 3-107, University of California, Riverside, CA, 1975. (5) Pitts, J. N., Jr., presented at the EPA Scientific Seminar on Automotive Pollutants, Washington, D.C., 1975, SAPRC Report No. 2. (6) Winer, A. M.; Graham,R. A.; Doyle, G. J.; Bekowies, P. J.; McAfee, J. M.; Pitts, J. N., Jr. Adu. Enuiron. Sci. Technol. 1980, 10, 461. 0013-936X/83/0917-0057$01.50/0
Carter, W. P. L.; Lloyd, A. C.; Sprung, J. L.; Pitts, J. N., Jr. Znt. J. Chem. Kinet. 1979,11,45. Atkinson, R.; Carter, W. P. L.; Darnall, K. R.; Winer, A. M.; Pitts, J. N., Jr. Znt. J. Chem. Kinet. 1980, 12, 779. Tuazon, E. C.; Winer, A. M.; Pitts, J. N., Jr. Environ. Sci. Technol. 1981,15, 1232. Finlayson, B. J.; Pitts, J. N., Jr. Science (Washington,D.C.) 1976,192, 111.
Finlayson-Pitts, B. J.; Pitts, J. N., Jr. Adv. Environ. Sci. Technol. 1977, 7, 75. Harris, G. W.; Carter, W. P. L.; Winer, A. M.; Pitts, J. N., Jr.; Platt, U.; Perner, D. Enuiron. Sci. Technol. 1982,16, 414.
Platt, U.; Perner, D.; Harris, G. W.; Winer, A. M.; Pitts, J. N., Jr. Nature (London)1980,285, 312. Carter, W. P. L.; Atkinson, R.; Winer, A. M.; Pitts, J. N., Jr. Znt. J. Chem. Kinet. 1981, 13, 735. Carter, W. P. L.; Atkinson, R.; Winer, A. M.; Pitts, J. N., Jr. Znt. J. Chem. Kinet., in press. Carter, W. P. L., presented at EKMA Workshop, U.S. Environmental Protection Agency, Research Triangle Park, NC, 1981. Spicer, C. W., submitted for publication in Environ. Sci. Technol. Hendry, D. G.; Kenley, R. A. J. Am. Chem. SOC.1977,99, 3198.
Waldman, J. M.; Munger, J. W.; Jacob, D. J.; Flagan, R. C.; Morgan, J. J.; Hoffmann, M. R. Science (Washington, D.C.), in press. Kapiloff, L. “The Acid Deposition Act of 1982”;California Assembly Bill 2752, 1982. Lloyd, A. C.; Lurmann, F. W.; Godden, D. A.; Hutchins, J. F.; Eschenroeder, A. Q.; Nordsieck, R. A. “Development of the ELSTAR Photochemical Air Quality Simulation Model and Its Evaluation Relative to the LARPP Data Base”; Environmental Research and Technology Document P-5287-500, 1979.
Whitten, G. Z., paper presented at EKMA Workshop, U.S. Environmental Protection Agency, Research Triangle Park, NC, 1981. “Chemical Kinetic and Photochemical Data for Use in Stratospheric Modeling”; Evaluation No. 4, NASA Panel for Data Evaluation, Jet Propulsion Laboratory, Pasadena, CA, Publication 81-3, Jan 15, 1981. Leung, S.; Goldstein, E.; Dalkeg, N. “Human Health Damages from Mobile Source Air Pollution: A Delphi Study”; EPA-600/5-78-016a, 1978, Vol. 1. Goldsmith, J. R.; Friberg, L. T. In “Air Pollution”, 3rd ed.; Stern, A,, Ed.; Academic Press: New York, 1977; Vol. 11, pp 458-610.
Pitts, J. N., Jr.; Lokensgard, D. M.; Harger, W.; Fisher, T. S.; Mejia, V.; Schuler, J. J.; Scorziell, G. M.; Katzenstein, Y. A. Mutat. Res. 1982, 103, 241. Ohgaki, H.; Matsukura, N.; Morino, K.; Kawachi, T.; Sugimura, T.; Morita, K.; Tokima, H.; Hirota, T. Cancer Lett. 1982, 15, 1. James N. Pltts, Jr.,” Arthur M. Winer Roger Atkinson, William P. L. Carter Statewide Air Pollution Research Center University of California Riverside, California 92521
SIR. In response to the statements of Pitts et al. relative to my paper (Environ. Sci. Technol. 1981,15,904) I wish to make the following comments: Background effects due to glass wall chamber surfaces appear to increase photooxidation rather than decrease it as evidenced in general by excess NO photooxidation with a clean chamber vs. gas-phase predictions. Chamber ozone
0 1982 American Chemical Society
Envlron. Sci. Technol., Vol. 17, No. 1, 1983 57
Envlron. Sei. Technol. 1983, 17, 58-62
levels would be expected to be high rather than low. Such background effects in any case would not be expected to significantly alter relations between NO, and ozone levels. The effects of NO, emissions on PAN are covered in our ref 17, where it was shown on the basis of Pitts’ chamber work that PAN formation decreases with initial NO, levels at HC/NO, corresponding to Los Angeles emissions. More data showing this were recently reported by Glasson (American Chemical Society Meeting, April 1982). Pitts et al. admit that adverse effects from the very low levels of nitric and nitrous acids in the atmosphere have not been demonstrated. The 8 h HNO, work place standard per the Government Industrial Hygienists is 2 ppm vs. a peak value of a few ppb in the atmosphere per Pitts et al., while nitrous acid is not listed as a toxic pollutant (1981-1982 Handbook of Chemistry and Physics”; CRC Press). The biological effects of such acids (e.g., oxidation of cell wall lipids), whether present as gas or fog, depend on the buffering capacity of biological fluids, since they are strong oxidizing agents only at a low pH. Buffering capacity probably far exceeds inhaled acidity (-0.1 mg of HNO,/day) from these components under worst conditions. The ammonia content of expired air is equivalent to 0.26-19 mg/day HNO, (Larson, T. V.; et al. Science (Washington, D.C.) 117, 1977, 161) if breathing rate is taken as 10 m3/day. We are indebted to Pitts et al. for the update on ozone levels. The primary point I wished to make was that NO, controls had offset the benefits of HC controls, and this conclusion still seems justified. Decreased driving because of higher fuel costs in this period also needs consideration in analyzing recent trends. The rate constant used by us for the reaction HCHO + OH is higher than the reported literature value. Reasons for this are discussed in ref 7. The value is based on HCHO disappearance on irradiation and does not consider other HCHO reactions (e.g., HCHO photolysis). As indicated in our article, treatment of reactions involving NO2, O,, OH, NO,, and N205was not intended to be rigorous. Not enough information on rate constants and concentrations for the various reactants are available for this. However, the assumptions made do appear to lead to a fairly good data fit. The paper deals with metropolitan centers throughout the U S . so that it is more appropriate to consider national than state air standards. The California 1-h standard of 0.25 ppm NO2 was established 12 years ago on the basis of emphysema health risk inferred from studies on rats rather than any human effects. Later animal work showed emphysema effects only at much higher levels (-30 ppm). No formal review of the NO2 air standard appears to have been made even though extensive work has failed to show significant human health effects below 1-2 ppm. The 10/1 ratio (N02/0,) for equivalent health effects still seems valid based on much additional information. Industrial hygienists still have an 8-h work-place standard of 5 ppm for NO2 vs. a 0.1 ppm standard for 03. Harmful effects that have been found at high NO2 levels (oxidation of cell wall lipids) would not be expected at lower levels even on a proportional basis because of the extreme effect of pH on nitrate or nitrite oxidation potential (see above). With respect to multiday episodes, nighttime effects, etc., negating the conclusions that NO, controls are counterproductive, it is pertinent that Pitts’ studies substantially took this into account by using a surrogate organic composition that included a major formaldehyde fraction. Limited tracer studies do not appear to show that leftover products are a major organic component, while 58
Environ. Sci. Technol., Vol. 17,No. 1, 1983
initial ozone level is near zero for all days. Although total radiation involve in Pitts 6-h runs is about half the theoretical maximum for the summer solstice, several factors combine to make the effective average irradiation during the summer-fall smog season much less. These include the following: downwind emissions, which are exposed to less radiation than initial components; radiation absorption by smog, fog, and clouds; increased zenith angle after the summer solstice. The studies of Jeffries et al. and Stephens et al. analyzed in our ref 7 show that 6 h of irradiation under Pitts et al. chamber conditions has about the same effect on NO oxidation as the radiation from one typical “sunny” summer-fall day. In regard to ecological impacts of nitrates, it now seems very clear from several papers presented at the recent Las Vegas Spring American Chemical Society Meeting that such compounds have no long-term adverse effect on lake pH because they are rapidly assimilated by vegetation (ACS Division of Environmental Chemistry; Abstr 22,500, 530; American Chemical Society: Washington, D.C., 1982). Rather nitrates are beneficial because they act as important plant nutrients. This view is further supported by McLean (JAPCA, 1981,31,1184-1187). Sierra lakes show essentially no change from near neutral pH in the last 16 years (Calif. Agric., 1981 May-June). W. B. Innes Purad Inc. 724 Kilbourne Dr. Upland, California
SIR: Since we also are concerned about the environmental air quality and health in the Los Angeles (LA) Basin if a less than optimum pollution control strategy were pursued, we feel obligated to reply to the preceding comments of Pitts et al. ( I ) concerning our earlier article (2). The major conclusion we reported was simply this: a reduction of the vehicular NO, emission standard (from 1.0 to 0.4 g/mi) for the purpose of controlling ozone (0,) in the LA Basin would be counterproductive because it would likely lead to higher ozone both in LA and along the entire downwind corridor to San Bernardino. We feel that this central conclusion and the scientific evidence supporting it stand unshaken. In their comments, Pitts et al. ( I ) cite three separate articles. This reply, however, will be restricted to those comments pertinent to our work, which was independent of that reported by Glasson (3)and by Innes ( 4 ) . Pitts et al. (1) never challenge our basic conclusions. Instead, they raise the following issues: (1)adequacy of the ELSTAR model; (2) the interpretation of modeling and smog chamber results, in general; (3) acid precipitation; (4) health effects of pollutants. We shall address the first two issues in detail, and we shall comment on the last two issues, though these two issues are beyond our present fields of expertise (as well as those of Pitts et al. ( I ) ) . (1)The Adequacy of the ELSTAR Model. Pitts et al. ( I ) contend that we have applied a model of limited reliability to the California South Coast Air Basin (CSCAB). However, the procedure followed in developing the ELSTAR model gives us confidence that this model is applicable to and reliable for the CSCAB. Lloyd et al. (5) first developed and tested the ELSTAR chemical mechanism alone with smog chamber data from the
0013-936X/83/0917-0058$01.50/0
0 1982 American Chemical Society
