Document qm4kOrz4drbdpV7maEqbL9GXq

E. P. Wheeler Pholodeconiposition of Chlorinated Biphenyls and Dihcnzofiirans Donald G. Crosby and Kenneth W. Moilanen Department of Environmental Toxicology University of California Davis, Calif- 956J6 The polychlorinated biphenyls (PCB's) have been widely detected throughout the world's aquatic environments (DUKE et al. 1970, VIETH and LEE 1970, SCHMIDT e aK 1971, HARVEY et al. 1973). They are accumulated by aquatic organisms (DUKE al_. 1970, ZITKO 1970, R1SEBR0UCH and de LAPPE 1972, STALLINC and MAYER 1972) and so present concern not only for their acute and chronic toxic effects (DUKE al. 1970, ZITKO 1970, HANSEN et al. 1971, STALLING and MAYER 1972) but also because of the probability of their transmission in food chains. PCB's do not appear to be particularly toxic to higher animals (PANEL 1972). In fact, several effects including chloracne, hepatotoxicity, and prophyrla originally attributed to PCB exposure later were ascribed to contained chlorinated dlbenzofurans (PANEL 1972, KIMBROUGH 1972). Although toxicity measure* ments with pure PCB Isomers appear not to have been reported, limited data with Arochlors indicate that maximum acute toxicity resides in the di-, tri-, and perhaps tetrachloro compounds IMURCAN 1972, STALLING and MAYER 1972, MAYER 1973). The chlorinated biphenyls, like chlorinated hydrocarbon Insecticides, are highly hydrophobic and may be expected to occur in lipid phases such as the organic films sometimes found on the surface of natural waters (DUCE et_ al. 1972). However, the aqueous solubility of the lower chlorinated members Is surprising; water saturated with the commercial Arochlor 1221 was claimed (ZITKO 1970) to contain 5 tng/liter, although other data indicate lower values (PANEL 1972). Recent laboratory investigations (MOILANEN and CROSBY 1973) Show that DDT and DDF are eanurrted. in part, to ..di"- -tri-, and tetrachloroblphenvls under simulated atmospheric irradiation conditions; these biphenyls would be expected to precipitate in rainfall (TARRANT and TATT0N 1968) if they were to form in the atmosphere or be selectively volatilized from surfaces. Conse quently, the possible deeradative effects of the ultraviolet (UV) component of sunlight on the low-molecular w.eight PCB "isomers is of particular interest and was the subject of this investigation. 372 MONS 039798 I --3 Materials. Pura standards of chlorinated biphenyl Isomers vere purchased from Aldrich Chemical Co. (Milwaukee, Wise.) and Analabs, Inc. (North Haven, Conn.) and vere homogeneous upon gas chromatography (glc). 2-Chloro- and 2,8-dichlorodibenzofuran vara prepared by the method of GILMAN at a_l. (1934). Methanol was redistilled reagent-grade and acetone-free (Malllnckrodc Chemical Co.), and other reagents were pure grades used as received. Irradiation. The chlorinated biphenyl (1 or 10 mg/1) in a small volume (0.3-2 ml/1) of methanol was suspended in distilled water; one liter of suspension was held In the dark, while another was Irradiated for 15-26 summer days in Davis, Calif., or for 1-2 weeks In an aerated, sunlight-simulating, laboratory photoreactor (CROSBY and TANG 1969). The suspensions were extracted exhaust ively with benzene, the extracts dried and vacuum-evaporated to 0.5 ml, and aliquots subjected to glc after methylatlon with ethereal diazomethane. The chlorinated dlbenzofurans were dissolved in purified methanol (10-100 mg/1) and Irradiated In the photoreactor. Allquota were removed at Intervals and subjected directly to glc. Chromatography. The biphenyls were chromatographed on e 180 x 0.2 cm column of 2X Carbowax 20M on 60/80 Chromoaorb G, tamparatUTe-programmed 150-250'C at 10*C/mln, TC detector. Fractione were collected from the effluent ges in glasa capillary tubc3, purified by rechromatography, ard their spectra compared with those of authentic specimens where possible. For mete spectrometry, the collected fractions were rechrometographed on a 180 x 0.2 cm column of 2X 0V-1 on 60/80 Chromoaorb G, temperature-programmed 150-250*C at 10*C/min, and detected with a Flnnigan Model 3000 mass spectrometer detector (GC/KS). The dlbenzofurans wars chromatographed on a similar 5X SE-30 column at 19S*C (EC detector) or 5X XE-60 at 190* (FID detector). Previous work in this laboratory demonstrated Chat chlori nated aromatic compounds are reductively dechlorlnaced readily In organic solvents when irradiated with UV light at sunlight wave lengths (CROSBY end HAMADMAD 1971). Under similar conditions, irradiation In aqueous media results in replacement of the chlo rine by hydroxyl as well as by hydrogen (CROSBY and LEXTIS 1969, M0ILANEN and CROSBY 1972). Several authors (SAFE and HUTZINGER 1971, HERRING et si. 1972 HUSTERT snd KORTE 1972, HUTZINGER et al. 1972, RUZO et al. 1972) recently have reported that simple chlorinated biphenyls as well 373 HONS 039749 as che complex PCB mixtures of commerce likewise underwent photo reduction In hexane solution. In aqueous suspension^pur Ir radiation experiments also showed dechlorination (Table I); \ TABLE l Photolysis of Chloroblphenyls in Water Irradiation^(hrs) Raduced Product Chloroblphenyl* A B (m/e) Hydroxyated Product0 (a/e) 2,4-Cli 2,5-Clj 3,4-Cl2 4,4'-Cl2 2,4,5-CIj 2,2\3,3'-CU 2,2\4,4'-Cl4 2,2' ,5,5'-CU 312 135 189 180 192 135 168 135 240 135 216 235 264 235 168 200 none 188 none 188 none 257 none 257 218 218d none 218 none 287 none 287d *10 mg/1 suspension Indoors, 1 mg/1 outdoors. OF40BL lamp (A) or summer sunlight, Davla, Calif. ^Methylated. i-Chlorodlbenzofuran detected by GC/MS. (B). for example, 4,4'-dichloToblphenyl formed 4-chloroblphenyl and 4-chloro-4'-hydroxybiphenyl as expected, although at a relatively slow rate. The higher chlorinated. Isomers and polymers reported previously (HUSTERT and KORTE 1972, HUTZINGER et, al. 1972) were not observed, and In each Instance only a reduced product containing one less Cl and a single (unidentified) product with Cl replaced by OH were detected by GC/MS. Indoor and outdoor results were Identical. Treatment of 2,2'-dlchloro- or 2-chloro-2'-hydroxyblphenyl with aqueous base, or simply boiling 2,2'-dlhydroxyblphenyls with water, Is known to form dlbenzofurans (CULLINANE et al. 1934, 2AHN and SCH1MMELSCHM1DT 1940, CASE and SCHOCK 1943), and the photochemical formation of dihenzofurana from 2-chloroblphenyla represented a logical extension. Irradiation of chlorinated biphenyls disporsed In water (Table I), followed by CC/MS, 374 MQNS 039750 revealed identifiable traces of 2-chlorodlbenzofuren ae a photolysis product of 2,5-dichloro- and 2,2*,5,5'-tetrechloro- blphenyl In roughly a 0.2% steady-state yield. ci ci Cl Similar lrradletlon of 2,9-dlchlorodlbenzofuran elso resulted in slow dehalogenetlon, explaining the previous appear ance of 2-chlorodlbenzofuran. Irradiation in purified aethanol under conditions similar to those which resulted in the rapid photoreduction of 2,7-dichlorodibenzo--dioxin (CROSBY at al. 1971) likewise caused disappearance of the dlchlorodlbenxofuran (Flg.l); like the 4-chlorobiphenyl (RUZO et al. 1972), the 2chlorodlbensofuran remained alaoet unaffected by light. Decomposition in aqueous suspension was slow. v. Although the cnvlronaental conversion of Arochlor onstltuents to dlbenzofurans was predicted (RISEBROUGH and ERCER 1971), other investigators, (HUTZINCER rt al. 1972, MARTIN t al. 1972) have BieiPKauccessfui In detecting the conversion f chlorinated blphenvla to dlbenrofurans Tn~lf6htr^nerhaps due o the TgptTf~decompositlon under energetic "irradiation conditions ^r-^hl"pfesence of jensitisenT. The "addition of the photoseneltlxar'4,4r^dIchlorobeneophehone to a aethanol solution of 2,8-dlchlorodlbenzofuran during irradiation (Flg.l) resulted in a sharp Increase in the photolysis rate. Both natural and synthetic photosensitizers have been shown to affect other xenoblotlcs (LYKKEN 1972, ROSS and CROSBY 1973), and the environmental sensitization of dlbenzofuran photolysis seeas quite plausible. The photodecoaposltlon of the lower chlorinated PCB lsoaers in both polar and "nonpolax-jolvenits"reveals the operation of wuirftnmknral tteghinrime whiqh could effectively degrade these widespread contaminants"! The recent report (HARVEY at alT 1973) that POD ailziuees uctur dispersed in seawater at levels up to 150 ng/1 indicates appropriate conditions for hydroxylatlon and dlbenzofuran formation in addition to the probability of reductive dechlorination by organic matter in the sea. Indeed, the notable absence of the lower chlorinated biphenyls 'from most environmental samples ls~sup,geatlve oi an~15portnt role at phutudeeempoaltlon lhthe environmental fate of PCB7*, the iTTtsraxetacion of their suune anfl'Tfibyemeht, and prediction of toxic "effects on aquatic life. MGNS 039751 Irradiation, hrs Fig. 1. Photodecomposltlon rates of 2-chlorodibenzofuran (MCDF) and 2,8-dichlorodlbenzofuran (DCDF) in methanol at 3G*C. 4,4'-Dichlorobenrophenone added as sensitizer (arrow). tomt/vimm. , We are grateful to C.J. Soderqulst for technical assistance. This research was supported, in part, by NSF Grant CB-33723X and USDA Regional Research Project W-45. MONS 039752 376 Mxmm CASE, F.H. and SCHOCK, R.U..JR.; J. Ad. Chem. Soc. 65. 2066 (1943) CROSBY, D.G. and TANG, C.-S.: J. Agr. Food Chem. 7, 1041 (1969). CROSBY, D.G. and HAMADMAD, N.: J. Agr. Food Chen. 19, 1171 (1971). CROSBY, D.G. and LEIT1S, E.: J. Agr. Food Chem. _17, 1033 (1969). CROSBY, D.G., WONG, A.S., PLIMMER, J.R., and WOOISON, E.A.: Science 173, 740 (1971). CULLINANE, N.M., DAVEY, H.G., and PADFIELD, H.J.H.: J. Chen. Soc. 1934, 716. DUCE, R.A., QUINN, J.G., OLNEY, C.E., PI0TR0V1CZ, S.R., RAY, B.J., and WADE, T.L.: Science 176, 161 (1972). DUKE, T.W., LOWE, J.I., and WILSON, A.J..JR.: Bull. Environ. Concan. Toxicol. 171 (1970). GILMAN, K., BROWN, G.E., BYWATER, W.G., and KIRKPATRICK, W.H.: J. Am. Chen. Soc. 56, 2473 (1934). HANSEN, D.J., PARRISH, P.R., and LOWE, J.I. et al.: Bull. Environ. Concam. Toxicol. 6_, 113 (1971). HARVEY, G.R., STEINHAUER, W.G., and TEAL, J.M.: Science 180, 643 (1973). HERRING, J.L., HANNAN, E.J., and BILLS, D.D.: Bull. Environ. Concam. Toxicol. 8, 153 (1972). HUSTERT, K. and KORTE, F.: Chcmosphere 1, 7 (1972). HUTZINGER, O., SAFE, 5., and ZZTKO, V.t Environ. Health Perspectives 1, 15 (1972). KIMBROUGH, R.D.: Arch. Environ. Health 25, 125 (1972). LYKKEN, L.: Environmental Toxicology of Peatlcldea, F. Matsumura, G.M. Bouah, and T. Mlaato, ede. Nev York? Academic, 1972, p. 449. MARTIN, R.L., PORTER, M.L., and POMERANTZ, I.H.: Environ. Haalth Perapactlvas 6, In press (1973). MAYER, F.L.,JR.: Fiah-Peetlclda Laboratory, USDI, Columbia, Mo., Paraonal Communication, May 1973. M0XLANBN, K.W. and CROSBY, D.C.: 165th. Meeting. Amer. Chem. Soc., Dallas, Texss, April 10, 1973. M0ILANEN, K.W. and CROSBY, D.C.: J. Agr. Food Cham. 20, 950 (1972) MORGAN, J.R.: Bull. Environ. Contam. Toxicol. , 129 (1972). PANEL ON HAZARDOUS TRACE SUBSTANCES: Environ. Rea. 5. 249 (1972). RISEBROUCH, R.W. and da LAPPS, B.: Environ. Health Perspectives 1, 39 (1972). RISEBROUGH, R.W. and BERGER, D.D.: Can. Wlldl. Sarv., Peat. Sec. MS, Report No. 23, 1971. ROSS, R.D. and CROSBY, D.G.: J. Agr. Food Chem. 21, 000 (1973). RUZO, L.O., ZABIK, M.J., and SCHUETZ, R.D.: Bull. Environ. Contam. Toxicol. 8, 217 (1972). ' SAFE, S. and HUTZINCER, 0.: Nature 232, 641 (1971). SCHMIDT, T.T., RISEBROUCH, R.W., and CRESS, F.: Bull. Environ. Contam. Toxicol. 6, 235 (1971). STALL1NC, D.L. and MAYER, F.L.,JR.: Environ. Health Perspectives 1, 159 (1972). TARRANT, K.R. and TATT0N, J.O'G.: Nature 219, 725 (1968). VEITH, G.D. and LEE, G.F.: Water Research U, 265 (1970). ZAHN, K. and SCH1MMELSCHH1DT, K.: U.S. Pat. 2, 172, 572 (Sept. 12, 1940). ZITK0, V.j Bull. Environ. Contam. Toxicol. 279 (1970). 377 MQNS 039753