RECOMMENDATIONS ON MINIMUM LEVELS OF SOLAR UV EXPOSURE
|Publication Date:||1 January 2011|
Popular attitudes towards sun light exposure have been ambivalent. Ancient men worshipped the sun as the source of life (Randle 1997). In the beginning of the 20th century Finsen was rewarded with a Nobel prize for his work on (sun)light (Randle 1997). Lack of sunshine was found to be a factor in the occurrence of rickets. In the second half of the 20th century a sun tan became a sign of good health but the attention of the medical and public health community focussed on the negative side of sun exposure, more specifically on skin cancer and on keratitis and cataract (Albert and Ostheimer 2002, 2003a,b).
For both the positive and negative (physical) effects of solar exposure the ultraviolet (UV) component of sunlight is commonly seen as the causal factor (Gezondheidsraad: Commissie UV-straling 1986, Advisory Group on Non-ionising Radiation 2002). Although the positive effects of UV exposure were acknowledged, especially with respect to vitamin D synthesis in the skin and the prevention of bone disease, public health guidance stressed the carcinogenic effects of excessive UV exposure and advised avoiding exposing bare skin to sunlight (WHO 1994, 2002). In recent decades data have become available that might lead to a reconsideration of the emphasis on the harmful effects of UV exposure in general and solar exposure in particular (Lucas et al. 2006b, Grant 2007, Lucas 2007). Technical Committee 6-58 of the CIE has further studied this issue.
Terms of Reference
The terms of reference of Technical Committee (TC) 6-58 (hereafter denoted as 'the committee') that compiled the present report were specified by the International Commission on Illumination (CIE) as
The fact that man cannot do entirely without UV is accepted by most scientists active in this field, but is not as well known as the widely accepted view that UV exposure should be limited to a sensible level thus avoiding or minimizing risks. The TC will formulate recommendations for a lower limit of UV exposure commensurate with good health.
The committee soon realized that defining a minimum exposure limit of a similar status as UV exposure limits for protection of workers and the general public (International Non-Ionizing Radiation Committee of the International Radiation Protection Association 1989, 1996, International Commission on Non-Ionizing Radiation Protection 2004) would probably not be feasible. As will be further detailed below this is due to the dependence of the (beneficial) effects of UV exposure on constitution, nutrition, behaviour and location. The committee therefore focussed on compiling input for scientifically underpinned public health guidance for solar exposure.
This report considers only exposure to solar UV radiation, the single UV source to which we are naturally exposed. The radiation from artificial sources varies greatly between sources, but is always different to the spectrum of sunlight. Thus the effects, and balance of positive and negative effects, will be different for artificial sources than they are for solar radiation.
The present report was developed in three meetings of the committee in 2005, 2006 and 2007. Furthermore the committee members prepared reviews of the literature that are reproduced in the second part of this report (the reviews cover the literature until 2006-2007). The guidance in Part I is based on an assessment by the committee of the scientific evidence for the various effects of solar (UV) exposure. In Annex A to Part I recommendations of other organizations are presented. Annex B to Part I reproduces recommendations from a working group of the International Agency for Research on Cancer (IARC).