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A STUDY OF AIR POLLUTION CARCINOGENESIS II.

The Isolation and Identification of Polynuclear Aromatic Hydrocarbons from Gasoline Engine Exhaust Condensate DIETRICH HOFFMANN, PH.D., AND ERNEST L. WYNDER, M.D. s PART OF A research program to investi- Agate possible carcinogenic activity of air pollutants and the contribution that automo- bile exhaust may make in this respect, we are undertaking chemical analyses of established and suspected carcinogenic and cocarcinogenic substances. The present report represents the analytic results of the isolation and identifi- cation of polynuclear aromatic hydrocarbons present in the exhaust from a gasoline engine. REVIEW OF LITERATURE Kotin and co-workers899 identified, in the particulate phase of exhausts from both gaso- line (Ford V-8) and diesel engines,

6 known polynuclear hydrocarbons and have shown their differential formation with respect to engine speed and load. In addition, an un- known compound was detected. The isolation and identification of these hydrocarbons was accomplished by collecting on filter paper par- ticulates from the engine exhaust and extract- ing the filter with benzene. The extract was then chromatographed on activated alumina;

the same known hydrocarbons and benzo[k]- fluoranthene were also isolated by Reuter et aL13 from diesel exhaust using an analytic technique similar to that just mentioned. Lyons10 and Lyons and Johnstonell reported an additional

8 aromatic hydrocarbons in gaso- line exhaust, as well as in diesel exhaust. These particulates from the engine exhaust were collected in hemp sacks, the sacks and From the Section of Epidemiology, Division of Pre- ventive hledicine, Sloan-Kettering Institute for Cancer Research,

444 E. 68th St., New York 21, N.Y. The authors are most grateful and appreciative of the excellent assistance in the preparation of the ultra- violet absorption and fluorescence spectra given by Mr. E. Theisz. The authors are indebted to the General Motors Corporation and to the Research Laboratories of the General Motors Corporation for assistance in providing samples of hydrocarbon condensate extracted from auto- mobile engine exhaust. The ben~o[u]pyrene-6-C~~ used in the tracer study was a gift from Dr. C. Heidelberger, Madison. Wis. Received for publication Jan. 10, 1%1. their contents extracted with acetone, and the residue from this extracted with petroleum ether. The concentrate of the second extrac- tion was chromatographed on alumina and the fractions chromatographed individually on alumina and then on silica gel. The ultra- violet absorption and fluorescence spectra of the end fractions served for the identification of the isolated hydrocarbons. MATERIALS AND METHODS The condensate was obtained from exhaust gas emitted by a late model V-8engine o p erating on a city driving schedule in a dy- namometer set-up. Operation of the engine and the collection and extraction of par- ticulate matter were carried out at the General Motors Corporation Research Laboratories, Warren, Mich. (Details of engine operation and recovery of condensate will be published elsewhere.12)Briefly, the procedure for collect- ing tar consisted of passing all the engine exhaust first through a stainless steel water- cooled condensing system, where most of the water of combustion as well as some of the solid and oily particulate matter was removed, then through a filter consistingof a glass-down blanket, 0.5 in. in thickness. We are using the word tar here as a descriptive term, realizing that it is not strictly accurate from a chemical point of view. In approximately