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Radiation (1979)] for radiation dose response, the ionizing radiation exposure required to produce a number of cancers equal to this spontaneous incidence was estimated to lie between 450 and 2100 rads (1 rad = 0.01 J/kg). From these "cancer equivalent" doses the number of singlestrand DNA breaks required to produce the spontaneous cancers is estimated to be 0.26-1.3 per cell DNA per day. It is suggested that the univalent reduction of oxygen in normal metabolism to 02 and subsequent production of more harmful radicals is the source of the pNA defects that, in cases where the defense mechanisms fail, lead to spontaneous cancer in the individual.In this paper I review the relationship between cancer mortality rates and energy consumption in order to ascertain whether a small or large proportion of the rate may be attributable to injury from intake of carcinogens because of industrialization. My conclusion is in accord with that of others-that only a small proportion of cancer deaths can arise from general pollution (1). If we assume the initiating event in cancer is a DNA injury, we can calculate the rate of internal (i.e., endogenous) injury that must be steadily sustained by individuals to account for the observed spontaneous cancer mortality. I suggest that this endogenous injury is caused by the small, but probably steady, rate of univalent oxygen reduction and subsequent production of harmful radicals.Advances in molecular biology in the last three decades have provided strong support for the idea that the mechanisms leading to mutation are similar or identical to those which, when applied to somatic cells, may produce cancers. Mutation (in genetic material) at a low but finite rate provides the flexibility to adapt. One can speculate that the price paid by the species for its ability to adapt is the necessity to deal with somatic mutations that may lead to cancer when the organism's defense mechanisms fail, in short, that cancer is the price the individual pays for the evolutionary survival of the species. Spontaneous cancer In order to estimate the spontaneous cancer mortality, I compared the crude and "corrected" mortality rates for 32 countries (identified later) and the energy consumption per unit area of each country. To anticipate the findings, because there was little correlation between corrected cancer rates and industrialization, I conclude that most cancer is spontaneous rather than being the result of man-made environmental agents. The choice of energy consumption per unit area as a crude "pollution"The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "ad-

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Quantum yields for dimethyibiacridyliuni ion chemiluminesceiice based 011 the amount of methyl acridone formed by treatment with either H,O, or with xanthine oxidasehypoxanthine in 0.01 M Na,CO, at pH 10.4 and at 25°C were found to lie between 0.01 I and 0.020 with an average of about 0.016. In mixed solvents containing pyridine and water or alcohol and water the emission spectrum of chemiluminescence of dimethylbiacridylium ions as well as those of diniethylbiacridene and its oxide were found to be identical with or very similar to the fluorescence of methyl acridone in the same solvent. A mechanism involving two successive two equivalent reductions of the diniethylbiacridylium ion to dimethylbiacridan followed by a radical attack and auto-oxidation leading to a compound which can undergo a reverse aldol type reaction to yield one (or two) molecule of methylacridone and one of a somewhat more reduced form is suggested. The kinetic equation relating maximum intensity of chemiluminescence tr) dimethylbiacridylium ion, hypoxanthine, xanthine oxidase, H+ and o2 concentrations was derived from the scheme suggested and found to fit satisfactorily the data obtained from a series of experiments in which the quantum yield was also obtained. INTRODUCTlONTHERE have been many studies on the chemiluminescence of dimethylbiacridylium ions (D") and related compounds and numerous iiivestigators have published spectra of the chemiluminescence as well as chemiluminescence and fluorescence spectra of certain related acridine derivatives.(** 149 15* 'O, ")SO far as can be determined none ofthe chemiluminescence spectra reported have been "correct" in the sense that they were free of appreciable self absorption or of fluorescence due to energy transfer to molecules not themselves involved in the chemiluminescence. The investigators were in nearly every case aware of this difficulty but instrumentation did not permit the use of sufficiently dilute solutions to obviate it.The availability of highly sensitive Iight measuring devices and of spectrofluorimeters equipped with sensitive photomultipliers made possible useful reinvestigations of the probable intermediates and end-products of 10, lO' dimethyl 9,9' biacridylium nitrate *