A short grant by the Czech Environment Ministry in autumn 2003 enabled us to start investigating various aspects of missing darkness. Four posters are being prepared for the November conference in Graz (Cancer and Rhythm), their abstracts are available at http://amper.ped.muni.cz/noc/english. At the present conference, a summary of the results will appear, together with some hints what could be investigated further.
Three topics have been covered.
One of them concerns a measurable quantity, blood pressure. It is suspected, that lack of darkness may cause its rise during sleep, and the first results offered a hint of that. A team led by J. Siegelová will present them in Graz.
Two queries concerned sleep problems as reported by Czech population. One third of it uses some measures to diminish the amount of artificially produced light going through the windows into the bedrooms. Five per cent report lack of darkness due to outdoor lighting as a major cause of sleep disturbances.
Just introductory results have been obtained as to which light levels are disturbing to those for who wish to sleep. One third of population perceives to be disturbed by full Moon in their bedrooms. Moon produces never more than 0.2 lx illuminance of the window. Much lower values of indoor illuminance are reported as disturbing. One millilux of face illuminance can be guessed as non-disturbing, if the source is not point-like and annoyingly bright when perceived by unclosed eyes (for closed eyes, the its direct physiologic influence ceases).
For measuring very low light levels, novel approach is to be used. Solar cells and digital cameras are suitable tools. In the case of the latter, their red, green and blue pixels enable to quantify the probable ``melanoptic'' impact of radiation, according to the Brainard's sensitivity curve. The first examples of such melanoptic luxes and lumens measurement will be shown and the methods discussed.
All the above results don't concern leukaemia directly, they are just hints that people are offended by improper light. The methods of measuring blue-green radiation may be immediately applied in further research.
Some future tasks have been suggested by H. Hrstková recently. Her patients might be asked about light in their bedrooms in the past times, when the disease developed, and in some cases we can measure the true effective light levels. For children, the option of light left on in their bedrooms (on purpose) should be investigated. Is there any difference from the healthy population? The national register may be used to search for seasonal trends - are there more cancers found in the autumn, after the period of less natural darkness (and possibly lower melatonin levels)? Of course, sunshine-caused ones are to be handled separately, and the natural variation of darkness at night can be much reduced by artificial light for population in rich countries (absence of seasonal change in melatonin levels is a consequence).