The Wavelengths in Sunlight Effective in Producing Skin Cancer:

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ABSTRACT. DNA is taken as thetarget for skin cancer induced by ultraviolet light, and the known data on the sensitivity of DNA as a function of wavelength are ...
Proc. Nat. Acad. Sci. USA Vol. 71, No. 9, pp. 3363-3366, September 1974

The Wavelengths in Sunlight Effective in Producing Skin Cancer: A Theoretical Analysis (DNA damage/action spectra/ozone)

R. B. SETLOW* Carcinogenesis Program and The University of Tennessee-Oak Ridge Graduate School of Biomedical Sciences, Biology Division, Oak Ridge National Laboratory, Oak Ridge, Tenn. 37830

Contributed by R. B. Setlow, June £1, 1974 DNA is taken as the target for skin cancer ABSTRACT induced by ultraviolet light, and the known data on the sensitivity of DNA as a function of wavelength are summarized. The sun's spectrum at the surface of the earth and the DNA action spectrum are used to calculate the carcinogenic effectiveness as a function of wavelength. The most effective wavelengths at 30'N latitude are 320 nm and short wavelengths will change only as a result of changes in the short-wavelength component.

Sunlight and Skin Cancer

Proc. Nat. Acad. Sci. USA 71 (1974) TABLE 1. Dosimetric parameters for different calculated sun spectra at the earth's surface

60 I-

Calculated by c= For 9 =

ref. 28 2.3 mm

ref. 37 3.2mm

ref. 38 3.4mm

ref. 37 3.2 mm

250

300

300

500

b

50 6

0

cbw

A. For DNA

3365

I'

I

40 II

30

n

(1/P)(dP/dc) 0. 88 mm-' 0. 68 mm-' 0. 69 mm-' 0. 71 mm-' (dP/P)/(dc/c) 2.0 2.2 2.3 2.3 B. For erythema (dP/P)/(dc/c) 1.7 1.7 1.8 1.9

.

-

20

I/I~

10* 0

Such synergistic effects will not alter the biological dose, P, in Eq. 3 but would change the form of f. The precise data to use for the transmission through skin are not important. Recent measurements using somewhat improved techniques (36) give higher transmissions than shown in Fig. 2 but the shapes of the T versus X curves are similar. Even if the transmission were 100%, there would be little effect on our conclusions (see below) because at short wavelengths the dominating effect is the fall-off of the sun's spectrum. RESULTS AND DISCUSSION

Plots of Eqs. 5 and 6 are shown in Fig. 3. It is clear that wavelengths