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\begin{document}

\title{\textbf{Disturbances by light at night: 
first results from Czechia and some new methods}
}

\author
{Martin Forejt, Jan Hollan}

\date{\small
Masaryk University in Brno, Dept. of Preventive Medicine, Tome�ova 12, 
602 00 Brno;\\ 
N. Copernicus and Planetarium in Brno, Krav� hora 2, 616 00 Brno,\\
 tel. +420 541 321 287, hollan(at)ped.muni.cz, 
 \wwws{http://www.astro.cz/darksky}
}

\maketitle

\thispagestyle{empty}

 A short grant by the \textbf{Czech Environment Ministry}
(VaV/740/3/03)  in autumn 2003 meant a start of scotobiology research 
by our group based at Masaryk University in Brno. Health-relevant
results are mentioned here, more details will be offered next month  (at
Cancer and Rhythm, Oct 14 - 16, 2004, Graz, Austria).  A detailed
research report is available in Czech only, at 
\wwws{http://amper.ped.muni.cz/noc},
just some bits are in English too.

\vfill

\bigskip
\centerline{\includegraphics[width=\textwidth]{pilz_vin}}

\centerline{
\emph{
Many people live in streets where windows are more illuminated than the road} 
}


\vfill


\newpage
\section*{Blood pressure}

has been suggested by \textbf{J. Siegelov�} as a quantity, which could be influenced by
inappropriate light at night.  A method of oscillometric measurement of blood
pressure by AD monitors  has been used to check the existence of the
effect.

Nine people were investigated, four men and five women, average 
age 37 (SD 15 years). They were monitored for 48 hours of  their
normal life. From 6 to 22, there were 3 measurements per hour; at night, 
just one per hour.
The experimental treatment consisted in  letting some light
into the bedroom for the second night 
(\textbf{illuminances of faces ranged from units to tens of lux}) . 


Within a period from midnight to 3 a.m., \textbf{an unusual rise of systolic
pressure was observed}, on average by 11~``mmHg'' (by 1.5~mmHg 
for a diastolic one). This rise was significant in both
systolic and diastolic pressures at the 0.05 level. 


Considering that 10~mmHg rise of systolic pressure corresponds to 
doubling the mortality on brain vascular accidents, the observed rise 
of 11~mmHg is by no means negligible.

 (J. Siegelov�'s further co-authors of the poster in Graz will be B. Fi�er,
Z. Br�zdov� and B. Fi\v{s}er)

\vfill


\newpage
\section*{Two queries about sleep disturbances etc.}

 One third of Czech population perceives to be disturbed by full
Moon in their bedrooms. Moon produces never more than 0.2 lx
illuminance of the window, half of that is typical -- 
\textbf{so white light
0.1 lx outdoors is surely a nuisance}. 
Even much lower values of  indoor illuminance
are reported as disturbing by some individuals.

 The introductory sample had three hundred respondents, the  main
query included then one thousand people, country-wide. Results:
\begin{itemize}
\item
\textbf{5~\% of Czech  population perceives
unwanted artificial light from outdoors as one of  the two main causes
of their sleep problems, 
}

\item
further 7~\% complains  about light amounts
which are not attenuated to tolerable levels, 

\item
further 20~\%
attenuates light pollution of their bedrooms to dark  levels perceived
as sufficient, 

\item
5~\% of Czech population is  unhappy to miss
the full natural morning light due to barriers  against the man-made
light they have to use. 

\end{itemize}

However, what  are the health
consequences of reduced morning light even for the remaining  20~\% of
population which uses barriers against light at night?

 No dependence of imissions to bedrooms on the size
of settlement has been found. Stationary outdoor lighting has been reported
as the source, street lighting at the first place.

Artificial
lighting intruding from outdoors disturbs one third of the population. 
This makes it a serious health problem regardless of its possible oncogenic
consequences, It should be avoided in any case.

 (More detailed results will be presented in Graz with
K. Sko�\v{c}ovsk� and R. Skotnica.)

\vfill



\newpage
\section*{Faint light and circadian-efficient radiation measurement}

For measuring very low light levels, novel approach is to be used. 
Solar cells and digital cameras are suitable tools. 

Standard light-meters (luxmeters) are meant for rather strong light,
over tenths of lux.
However, much 
lower light levels are perceived as disturbing, down to
\textbf{one millilux of the face illuminance}. This limit seems to be 
a safe one, if the light does not come from a small source (then it could be
still disturbing when the eyes are opened).

 A simple way of measuring illumination down to millilux level is using 
a \textbf{solar cell and a common multimeter}.  Just the type of the
light sources is to be guessed and appropriate calibration used (in
Graz, such methods will be shown  together with F. Kerschbaum, T. Posch
and M. Bleha from Vienna Uni). Example measurement during twilight
demonstrates drawback of two luxmetres against a solar panel for faint 
light, as the panel behaves proportionally for sure:

\medskip
\centerline{\includegraphics[width=\textwidth]{calib_faint}}


For circadian influences, standard luxmeters would need similar guesses
and calibrations,
as they are made to match the daytime eye
spectral sensitivity. In principle, luxmeters and solar cells may be
equipped with an additional or replacement filters to gain spectral
sensitivity matching the \textbf{``melanoptic curve''}
(Brainard \emph{et al.} 2001; 
Thapan \emph{et al.} 2001; 
Glickman \emph{et al.} 2002). Nobody offers such filters up to now, 
as far as we know.

What about blue pixels of modern digital cameras? For two camera types
which offer raw data this has been examined using a solar
spectrum for calibration. The images have been taken with  the
appropriate angular height of the Sun in the sky, so that its light went
through 1.5 times the thickness of the atmosphere. An author's CD-based
cardboard spectroscope  (with a slit from two razors) had been used,
after a series of attempts.

\bigskip
\centerline{\includegraphics[width=0.7\textwidth]{detail}}

\bigskip
The spectrum taken with Fuji S5000 camera:

\medskip
\centerline{\includegraphics[width=\textwidth]{16spIlan}}

\bigskip

Solar spectrum has a lower intensity at a handful of wavelengths, so-called
spectral lines. After processing the images with our software,
the solar spectrum graph
as recorded by the three types of camera pixels has been obtained:

\medskip
\centerline{\includegraphics[width=\textwidth]{16spL}}

\medskip
\centerline{\includegraphics[width=\textwidth]{15spL}}

A canonic solar spectrum as arriving through ``1.5 airmasses'' is shown
as well (ASTM, 2003). It helped to
match the wavelengths (most prominent absorption features are marked by
vertical lines). The three sensitivities of human eye are plotted for
comparison: photopic, scotopic, and, just by those several points from
one of the pioneer works 
(Brainard \emph{et al.} 2001), ``melanoptic'' (including the crude estimate of
the 420 nm point; in the other paper 
(Thapan \emph{et al.} 2001); 
 the sensitivity appeared several
times larger at 424 nm).

Apparently Fuji S5000 blue sensitivity
matches the assumed melanoptic eye sensitivity rather well. The blue peak
of Canon EOS D60 seems to be a bit too narrow in its violet wing.

Curves made by dividing the recorded spectra by the canonic solar
spectrum are given in a linear scale in the next graphs. They
are to be considered as preliminary (illumination of the diffraction
grating by different parts of the Sun has to be excluded and the
spectral influence of the aerosols as a difference from the ``standard
atmosphere'' has to be quantified). Present uncertainties down in
the left wing of the blue filter reach perhaps 30 per cent. 

\medskip
\centerline{\includegraphics[width=\textwidth]{16spT}}

\medskip
\centerline{\includegraphics[width=\textwidth]{15spT}}

So, at least some CCD cameras can measure melanopsin-affecting light
rather well. But how to express the amount of effective radiation?

This should be an analogy to expressing scotopic-effective radiation.
There are ``scotopic luxes'' (lumens, candelas) for this purpose. The 
definition is based on the demand that at 555 nm monochromatic radiation
there is always 683 lumens per watt. For a flat spectrum this means that
scotopic illumination is some 2.5 times the scotopic one, given the
sensitivities as shown in the graphs.

 For melatonin suppression, the sensitivity at blue-green maximum is
probably more than ten times  larger than at 555 nm.  We can crudely say
that \textbf{a flat spectrum light would give ten times more melanoptic lumens
than photopic lumens}. The number might hold well thanks to the fact,
that the violet part of the melanoptic sensitivity is influenced by a
shortwave opacity of the lens, and so the curve is probably narrower
than the photopic one.

 Sunlit white surfaces have not a really flat spectrum, but for 
the green and blue filters it works almost like that. 
\textbf{By setting 
their B luminance to ten times the photopic one} (measured by a luxmeter, 
or computed astronomically), \textbf{the camera is simply calibrated.}

All needed software is available at
\wwws{http://amper.ped.muni.cz/light/luminance}. It's not easy to use,
but what's important: by taking several images by a suitable camera, the
effective amount of radiation affecting melatonin secretion can be
documented for further use. 

\vfill

\newpage
\section*{Topics for further research}
 
\textbf{H. Hrstkov�} 
suggested recently some ways of investigating the light
and leukaemia link.  

 Patients might be asked about light in their bedrooms in the past times,
when the disease developed. In some cases we can even measure the
effective radiation levels. For children, the option of light left on in
their bedrooms (on purpose) should be registered. Is there any
difference from the healthy population?  

 National oncologic registers 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).


\section*{References}


 Brainard GC, Hanifin JP, Greeson JM, Byrne B, Glickman G, 
   Gerner G., et al., 2001,
Action spectrum for melatonin regulation in 
humans:
   evidence for a novel circadian photoreceptor. \emph{J. Neurosci.}
   \textbf{21}(16), 6405-6412.
      
Glickman G, Levin R, Brainard GC, 2002, Ocular input for human
     melatonin regulation: relevance to breast cancer. 
     \emph{Neuroendocrinol.
        Lett.}, \textbf{23, suppl. 2}, 17-22.
	
Thapan K, Arendt J, Skene DJ, 2001, An action spectrum for melatonin 
suppression: evidence for a novel non-rod, non-cone photoreceptor 
system in humans. \emph{J.Physiol}, \textbf{535}, 261-267.


American Society for Testing and Materials, 2003,
 Solar Spectral Irradiance: Air Mass 1.5.
\wwws{http://rredc.nrel.gov/solar/spectra/am1.5/}
	   

\end{document}
