7. Conclusion on UV radiation and sunbeds
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Question 1: What are the general health and safety implications (negative and positive) relating to the exposure of persons to ultraviolet radiation (UVR) 7?
- Clinically relevant UV-radiation is UVB (280 – 315 nm) and UVA (315-400 nm)
- Solar UVB (~295 – 315nm) is primarily responsible for inducing erythema (sunburn) and tanning
- UVA has similar acute clinical effects to UVB if the physical doses (J/cm²) given are approximately 1000 times greater
- Human skin may be phenotypically classified into phototypes I – VI which are determined by acute sensitivity to sunlight, melanin content and tanning ability
- Solar exposure is associated with basal cell carcinoma, squamous cell carcinoma and malignant melanoma.
- The risk of a given type of skin cancer is influenced by patterns of UVR exposure
- Phototype is a good indicator of skin cancer risk which reflects acute sensitivity to sunlight with phototype I being the most sensitive and phototype VI being the most resistant
- Moles and freckles are good indicators of susceptibility to malignant melanoma
- Moles and freckles are independent risk factors for skin cancer
- UVR is immunosuppressive in humans, the consequences of which are unknown but may be important in skin cancer and infectious diseases
- Public health messages should be directed to those people at greatest risk of skin cancer in order to promote behaviour which is appropriate to the balance of risk
- Solar UVR, especially UVB, causes photokeratitis (snow blindness) of the eye and increases a cataract formation.
- There is evidence that solar UVR exposure is associated with ocular melanoma
7 The International Commission on Illumination (CIE) defines ultraviolet radiation (UVR) as optical radiation between 100 and 400 nm. The spectral region is divided into three photo-biological spectral regions: UVC (l00-280 nm), UVB (280-315 nm) and UVA (315-400 nm).
Question 2: What are the differences between risks associated with exposure of persons to natural UVR and those risks from artificial UVR? What are the differences regarding the health and safety risks with respect to exposure of persons to UVA, UVB and UVC radiation respectively?
- There are no intrinsic differences between the physical and biological properties of natural and artificial UVR but there are differences in spectral profile that may have biological consequences
- It is relatively easy to compare the acute effects of natural and artificial UVR but much more difficult to compare the long-term effects.
- UVR, with and without photosensitizers, is used in the phototherapy of skin diseases and skin cancer is an accepted risk in such treatment
- Wavelength dependency (action spectrum) studies show that UVB is the most harmful part of the solar UVR spectrum for both acute and long term term-effects but wavelength dependency data on UVA are more limited than for UVB
- We lack data to make conclusive statements on the wavelength dependency of melanoma
Question 3: Is the total dose value of UVR the only effective health and safety parameter with regard to the risks associated with exposure of persons to both natural and artificial UVR? What is the validity of the Bunsen-Roscoe law8 over the range of irradiances and wavelengths associated with exposure of persons to both natural and artificial UVR?
- The reciprocity law applies for human erythema
- There are no quantitative human data for long-term effects but patterns of exposure may be important, especially for melanoma (see Question 1) that suggests a failure of the reciprocity law
8 The Bunsen-Roscoe law (law of reciprocity) states that a certain biological effect is directly proportional to the total energy dose irrespective of the administered regime. Dose is the product of intensity and the duration of exposure. (Bunsen R, Roscoe HE, Photochemische Untersuchungen, Poggendorff´s Annalen 1855: 96: 373-394, 1857: 100: 43-88 and 481-516, 1857: 101:235-263, 1859: 108: 193-273.).
Question 4: What are the specific health and safety implications (negative and positive) relating to the exposure of persons to UVR from tanning devices for cosmetic purposes?
- There are some case reports for adverse clinical effects (other than skin cancer) from sunbed use but it is not possible to estimate the frequency of these
- Several studies, and a meta-analysis, have shown a significant association between sunbed use and malignant melanoma. Typically, the risk for developing melanoma in relation to the use of sunbeds is around 1.5.
- Sunbed use can result in the desired cosmetic outcome which is tanning
- There is no evidence to support a pharmacological basis for the “feel good” factor of sunbed use
- Use of sunbeds that contain UVB may enhance vitamin D status but there are few data available on this relationship. The emission spectrum of the source is likely to be important
- There is some evidence that sunbed use is associated with ocular melanoma
Question 5: Are limit values necessary for the irradiance of UVR from artificial sources, in particular from tanning devices for cosmetic purposes, with respect to health and safety? Is it necessary to give different values for the irradiance of UV-A, UV-B and UV-C radiation respectively? If so, please specify the limit values for the irradiance of artificial UVR above which adverse health effects will occur. What are the uncertainties of these limit values?
- The biological consequences of a given sunbed emission spectrum are much more relevant than its specific irradiances within different wavebands which were originally defined by physical rather than biological parameters
- A biologically effective dose can be obtained by weighting a given emission spectrum with a relevant action spectrum
- This weighting should be done with the human erythema action spectrum, which is similar to the tanning action spectrum and the estimated human action spectrum for squamous cell carcinoma. This gives an erythemally weighted irradiance of the emission spectrum of the sunbed as demonstrated in Appendix A
- The maximum erythemally weighted irradiance should not exceed 0.3W/m2, or 11 standard erythema doses (SED) per hour. This is equivalent to tropical sun, which the WHO terms extreme.
- Certainty can only be reasonably assumed for acute effects
Question 6: Please specify the limit values of total dose of artificial UV-A, UV-B and UV-C radiation above which adverse health effects will occur, taking into account skin phototype, intensity of exposure, duration of exposure and associated uncertainties.
- There is no need to specify different dose limits for UVB and UVA for the same reasons given in Question 5. However, there is no justification for the presence of UVC in tanning devices.
- The dose limits for adverse acute effects are dealt with in Question 5. In the context of risk assessment, it is not possible to give dose limits for skin cancer because of lack of human dose-response data. However, SCC is a stochastic effect for which there is no assumed threshold dose. Any annual dose limits given are arbitrary
- The human erythema action spectrum is similar to the estimated human SCC action spectrum based on mouse data. This may also represent the wavelength dependency for human BCC. However, we lack mammalian data on the wavelength dependency of malignant melanoma. Broad spectrum studies in mice indicate that as with non melanoma skin cancer, UVB is much more important than UVA
- The important biological risk factors for malignant melanoma are age, sex (in some populations), skin phenotype (in particular types I and II), moles, freckles and family history. Behavioural/environmental risk factors include intermittent sunburning UVR exposure, especially in youth.
UVR tanning devices were not in widespread use before the 1990-s and the full health effects of their use are not yet known. It will take several years before the real picture of the role of the UVR tanning devices in inducing skin cancer becomes fully apparent. This is due to the long induction period of the cancer.
The SCCP is of the opinion that the use of UVR tanning devices to achieve and maintain cosmetic tanning, whether by UVB and/or UVA, is likely to increase the risk of malignant melanoma of the skin and possibly ocular melanoma. People with known risk factors for skin cancer, especially malignant melanoma, should be advised not to use UVR tanning devices. Specifically, these are (i) skin phototypes I and II and the presence of freckles, (ii) atypical and/or multiple moles and (iii) a family history of melanoma. Eye protection from UVB and UVA should be worn if sunbeds are used.
Risk of melanoma seems to be particularly high when using sunbeds at a young age. Thus UVR tanning devices should not be used by individuals under the age of 18 years.