The dose-response relationship for tumourigenesis by UV radiation in the region 311-312 nm

Groups of hairless mice were irradiated daily with Philips TL01 UVB sources. This type of lamp has become available recently and was developed for UVB phototherapy of psoriasis. The TL01 emits radiation in a narrow band around 311-312 nm. Tumours developed on all animals. The dose-response relationship had practically the same shape as that found in a similar experiment with Westinghouse FS40 sunlamps; the tumour induction time appeared to be proportional to the daily dose to a power of -0.58. An additional experiment was performed with a TL01 from which the shorter wavelengths were filtered away. This reduced the carcinogenic effectiveness by a factor of 2.3. The potential of the filtered lamp for phototherapy of psoriasis is discussed.     

THE USE OF DIFFUSERS IN THE MEASUREMENT OF TRANSMISSION OF HUMAN EPIDERMAL LAYERS

Abstract— The transmission of the outermost layers of human skin is measured, by use of a diffuser. The sample is transferred to the diffuser and inserted into the measuring beam. The reference beam is also measured after passing through the diffuser. The diffuser transforms the light in both the sample and reference beams into a completely diffuse flux. The radiant flux of light emerging from the diffuser is directly proportional to the radiant flux of the light impinging on the diffuser, but does not depend on the angular distribution of the impinging light. Because of this particular property, a diffuser may be used to measure the transmission of scattering specimens. The analogy between a diffuser and an integrating sphere is pointed out.
Deviations of commercially available diffusers from the perfect behaviour lead to deviations in the measured transmissions that are negligible (< 3%) for epidermal and corneal samples. Spectral transmission data from representative skin samples are presented. It is found that correction for fluorescence is necessary. Due to this correction the epidermal UV-C transmission is lower by a factor of 10–100 than without correction, and the epidermal absorption maximum is shifted from 275 towards 265 nm.     

Transmission of UV-radiation through human epidermal layers as a factor influencing the minimal erythema dose

Abstract— The extent to which transmission of human Caucasian epidermis and stratum corneum influences the Minimal Erythema Dose (MED) was examined for UV-B and UV-C.
Transmission correlated well with variations in MED for UV-B and UV-C that exist between individuals, as measured on the skin of the lower back and anterior upper leg.
Regional differences of the MED that occur within the same individual between different parts of the body, were related less well to differences in transmission. For UV-B, the difference in transmission of stratum corneum and epidermis between upper leg and lower back was on the average too small to completely account for the difference in MED UV-B. Other parameters, therefore, have to be involved in determining such regional variations in MED UV-B. For UV-C, on average, the difference in transmission of stratum corneum was smaller and of epidermis larger than the difference in MED UV-C between upper leg and lower back, though the deviations were not significant.
A series of UV-B irradiations of the lower back resulted in an increase in MED UV-B and MED UV-C, which was paralleled by a decrease in transmission of stratum corneum and epidermis. The average decrease in UV-B transmission of stratum corneum was too small and that of epidermis somewhat too large to account for the average increase in MED UV-B. The average decrease in UV-C transmission of stratum corneum was about as large as the average increase in MED UV-C. Consequences of these observations for the location of the primary reactions leading to erythema are discussed.
The relationship between log MED UV-C and log MED UV-B was confirmed to be approximately linear.     

OZONE DEPLETION AND INCREASE IN ANNUAL CARCINOGENIC ULTRAVIOLET DOSE

An increase in skin cancer incidence due to an increase of solar ultraviolet (UV) radiation is one of the best quantitated effects of stratospheric ozone depletion. Until now, estimates of effective UV dosages could not be based on spectral data on carcinogenicity. Instead the spectral dependence of sunburn or mutations was used. These data contained little information on longwave ultraviolet radiation (UVA: 315-380 nm). Recently, in hairless mice, experimental data have become available on the carcinogenic effectiveness of the ultraviolet, including UVA. From these new data we can estimate the effect of ozone depletion on the ambient annual carcinogenic UV dose. We find that a 1% decrease in ozone yields a 1.56% increase in annual carcinogenic UV; this value is not strongly dependent on geographical latitude. From this result, combined with the dose-response relationship for UV carcinogenesis, we conclude that for a 1% decrease in total column atmospheric ozone an increase of 2.7% in non-melanoma skin cancer is to be expected.     

EVALUATION OF SKIN CANCER RISK RESULTING FROM LONG TERM OCCUPATIONAL EXPOSURE TO RADIATION FROM ULTRAVIOLET LASERS IN THE RANGE FROM 190 TO 400 nm

The relative risk of occupational exposure to radiation from UV lasers was estimated using a mathematical model based on both epidemiological data and animal experiments. Calculations were performed for the 193 nm ArF excimer laser cornea shaping, the 308 nm XeCl excimer laser for coronary angioplasty, and other UV lasers in a laboratory environment. The model included the effects of direct exposure and exposure to scattered radiation. The results show that for the two medical applications the increase in the relative risk is comparable to that of one additional day of sunbathing per year. For subjects exposed to UV lasers in a laboratory setting, the relative risk may increase to a value comparable to that of people with an outdoor profession.     

FORWARD SCATTERING PROPERTIES OF HUMAN EPIDERMAL LAYERS

Abstract From an optical point of view the outermost skin layers contain numerous structures by which penetrating radiation may be scattered as well as absorbed. The nature and strength of this scattering may strongly influence the extent of penetration. We illuminated samples of stratum corneum and full-thickness epidermis with collimated radiation and measured the angular intensity distribution of the transmitted radiation; we did this in the ultraviolet for several angles of incidence, and in the visible for perpendicular incidence only. Skin samples were obtained from the skin of the lower back and upper leg of Caucasian volunteers. Epidermis and subsequently stratum corneum were separated by chemical methods. In the case of stratum corneum, the angular intensity distribution of the transmitted radiation peaks strongly at all wavelengths, in approximately the direction of the incident radiation, that has been refracted at the surface of the sample. With full-thickness epidermis, the distribution of the transmitted radiation also peaks, though less strongly than with stratum corneum. These features suggest a forward oriented scattering mechanism. Both in the case of stratum corneum and full-thickness epidermis, the angular distribution flattens towards the shorter wavelengths and with increasing thickness. The wavelength dependence suggests that both scattering and absorption increase towards the shorter wavelengths. The existence of a thickness dependence indicates that volume scattering occurs. Hydration of stratum corneum is found to influence its scattering properties. Dry samples scatter less than hydrated samples. The consequences of our findings for modelling skin optics are briefly discussed.     

Investigation of 38Ar levels by 37Cl+p reactions: (I). Yield curves,excitation energies and branching ratios

Yield measurements have been performed on the reactions ³⁷Cl(p, p₀)³⁷Cl, ³⁷Cl(p, α₀)³⁴S (E_p = 1.17–1.70 MeV) and ³⁷Cl(p, n₀)³⁷Ar, ³⁷Cl(p.γ)³⁸Ar (E_p = 0.64–2.92 MeV); detailed investigations are restricted to resonances below E_p = 1.79 MeV. Resonance energies, strengths and (some) widths are reported for 12, 26 and 247 resonances in the reactions (p, p₀), (p, n₀) and (p, γ), respectively.Simultaneous (p, α₀) and (p, γ) yield measurements over selected E_p intervals in the E_p = 0.88–1.64 MeV range established the existence of 42 resonances decaying by both γ and α₀ emission. Analysis of the γ-ray spectra of 100 ³⁷Cl(p, γ)³⁸Ar resonances leads to precision excitation energies (ΔE_x = 0.1–2 keV) of 57 bound states (E_x < 8 MeV) and branching ratios of the resonances and of 50 bound states.     

EFFECT OF CHRONIC UV EXPOSURE ON EPIDERMAL TRANSMISSION IN MICE*

In connection with an investigation on UV-tumorigenesis in hairless mice, the question arose in what way the epidermal transmission changes under chronic UV exposure. At regular time intervals, epidermal sheets of these mice were optically probed, i.e. the specimen was irradiated perpendicularly to its surface with a collimated monochromatic beam of 313, 302 or 297 nm and the transmission was measured in forward direction and a small angle around it. The optical probe measurement was sensitive to epidermal changes and easy to perform; it correlated well with thickness and total transmission of the epidermal sheet. As a result it was found that over the dose range investigated the logarithm of the epidermal transmission at 297 nm was a simple linear function of the daily UV dose and the time of treatment. Calculations, in which this result is combined with data on UV-tumorigenesis over the same dose range, show that the change in epidermal transmission is sufficiently large to have an important bearing on the dose-response relationship for tumorigenesis by chronic UV exposure.