gene, generated from arcing PVC-clad electrodes, can be assessed from these experiments. The maximum levels of phosgene ranged from 11 to 70 ppm and averaged 29 ppm for the eight runs reported (3). The arc conditions of the previous study (10 kV, 180 s, 0.5-1.0-cm gap) were never exactly duplicated in this study, because the amount of NO2 generated would have greatly exceeded the largest calibra tion standard available. However, the data in Table II indicate that the amount of N 0 2 expected can be esti mated with reasonable confidence from an extrapolation of this study. The expected N 0 2 concentration would be between 15,000 and 30,000 ppm, depending on the actual arc gap. This is 500 to 1000 times greater than the average phosgene concentration reported. In comparing these concentrations, the relative toxicities of NO2 and phosgene must be considered. Table III lists published animal mortality data for both NO2 and phosgene (10). Although none of the animal mortality studies were carried out under identi cal conditions, it is still obvious that phosgene is no more than five times more toxic than NO2· Therefore, even taking into account the higher relative toxicity of phosgene, the toxic expo sure to NO2 that would be generated
Table III. Animal mortality data for N0 2 and phosgene ( 10) Substance
Concentration
Time
75 ppm Rat LC 5 0 30 min 110 ppm Mouse LC 5 0 30 min 79 ppm Dog LC,_0 30 min 141 ppm Guinea pig LC5o 30 min N02 250 ppm Mouse LC L o 30 min 315 ppm Rabbit LC 5 0 15 min a LC50 = the concentration required to kill 50% of the animal population in the given time. " LCLo = the lowest published concentration causing death in the given time.
under these arc conditions is 100 to 200 times greater than that due to phosgene. This study shows that NO2 concen trations far in excess of the lethal lev els shown in Table III can easily be generated in a 1-L flask. In a realworld situation, where volumes are much larger, the actual NO2 concen-
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t r a t i o n will p r o b a b l y be lower, al t h o u g h localized areas in t h e vicinity of t h e arc could still be dangerous. Similarly, t h e same dilution factor could be expected t o yield significant ly lower c o n c e n t r a t i o n s of any p h o s gene g e n e r a t e d from t h e arc of a P V C - c l a d wire. Scale-up e x p e r i m e n t s , relating NO2 c o n c e n t r a t i o n t o o t h e r toxic species, a r e necessary t o assess t h e toxicological implication of t h e s e variables. However, t h i s s t u d y does show t h a t t h e levels of NO2 g e n e r a t e d from an arc are 500-1000 t i m e s higher t h a n any p h o s g e n e g e n e r a t e d from arcing a P V C - c l a d wire. T h e s e results strongly suggest t h a t t h e toxic expo sure from phosgene g e n e r a t e d b y t h e electrical arcing of P V C - c l a d wires is insignificant w h e n c o m p a r e d t o t h a t of t h e NO2 g e n e r a t e d in t h e s a m e arc.
References (1) Task Force on Flammability, Smoke, Toxicity, and Corrosive Gases of Electric Cable Materials. NRC Publ. Ν or AB342; National Academy of Sciences: Washington, D.C., 1978; p. 4. (2) Hinderer, R. K. J. Fire Sci. 1984,2 (1), 82. (3) Brown, J. E.; Birky, M. M. J. Anal. Toxicol. 1980,4 (4), 166-74. (4) Patty, F. Α., Ed. "Industrial Hygiene and Toxicology"; Interscience Publish ers: New York, N.Y., 1962; Vol. 2, pp. 919-23. (5) Riegel, E. R. "Industrial Chemistry"; Reinhold: New York, N.Y., 1949; p. 113. (6) Matthews, R. D. J. Comb. Toxicol. 1980, 7, 99-118. (7) Arakawa, E. T.; Nielsen, A. H. J. Mol. Spectrosc. 1958,2, 413-27. (8) Nyquist, R Α.; Kagel, R. O. "Infrared Spectra of Inorganic Compounds"; Aca demic Press: New York, N.Y., 1971. (9) Verhoek, F. H.; Daniels, F. J. Am. Chem. Soc. 1930,53,1250-63. (10) Christensen, H. E.; Luginbyhl, T. T., Eds. "The Toxic Substances List 1974 Edition"; U.S. Department of Health, Education, and Welfare: Rockville, Md., June 1974.
