This is what I got from the web.
Carl.
The Affects of Light at Night
Human health:
Melatonin (MLT) is a protective hormone and strong antioxidant having evolved in all plants and animals over the millennia. In vertebrates, MLT is normally produced by the pineal gland during the early morning hours of darkness, even in nocturnal animals, and is suppressed by exposure to light at night (LAN).
Medical research shows that the suppression of MLT by exposure to light at night LAN appears to be one reason for the higher cancers rates in the developed world.
New street lighting is being installed on taller stanchions, so that the light, although angled downwards is now above bedroom window level, so that light is increasingly entering bedroom windows at night. This problem is compounded due to the use of whiter light bulbs as the human eye is more sensitive to this part of the spectrum at these light levels. Moreover, the problems caused by new street lights shining into windows is made worse as unlike the yellow low pressure sodium lights, the spectrum of the new lights cuts melatonin production in the human brain. The result is that whilst the new street lighting is good for the problem of skyglow, it is not good for the problems of light nuisance and human health
Light at night disturbs sleep, resulting in a general loss of quality of life, reducing functionality at work or people taking time off, contributing to a loss of economic competitiveness of the nation. It may also lead to an increase in road accidents due to tiredness. . In a recent survey 35% of people stated that lighting hindered sleep.
Crime
There are no independent studies which categorically show that crime is reduced by lighting and several government sponsored research projects in the United Kingdom and the United States of America have failed to demonstrate any benefit from lighting in the fight against crime.
School districts across the United States have reduced the cost of vandalism by adopting a “Dark Campus” policy. All lights are turned off between 11pm and 6am. As well as reducing crime against school property they have achieved significant savings in their electricity bills.
Graffiti “artists” prefer their work to be seen by the public and given a choice between a dark unlit wall and a well lit wall, they will chose the latter.
Perpetrators of crime need to see what they are doing, just like the rest of us and prefer to operate in well lit areas where they can also easily see if there is anyone watching them. A criminal using a torch in an unlit area is more likely to arouse suspicion than someone wandering around brazenly in an over lit area.
Energy, climate change issues
On a global scale, approximately 19% of all electricity used produces light at night.
If we take security light as an example of how small changes can have a big impact.
In Ireland there are approximately 1.5 million households. If one in ten have a 500 watt security light there will be 150 000 lights
(150 000 x 500 w) x 0.50hr/night = 37,500 kW-hr/night. Per year this must be multiplied by 365 = 13.7M kW-hr/year. If 1 kW-hr produces 0.43kg of carbon dioxide, then some 5.9M kg/yr of carbon dioxide is produced as a by product from producing the electricity needed to power domestic floodlights alone within Ireland.
If a new diesel car produces 150g of carbon dioxide per kilometre travelled, 3,933 cars would have to travel 10,000 km per year to produce this figure (5.9 M kg Carbon per year This means that the carbon dioxide produced by domestic floodlights alone on for an average of 30 minutes per night is statistically similar to that produced by the average car usage of a town of c. 4000 persons – around the size of for example Tipperary town or Cavan.
The implications are clear if this figure is extrapolated to commercial artificial lighting; it must be a sufficiently significant form of waste to deserve regulation at planning stage. Indeed, major infrastructure projects are generally the worst sources of light pollution, due to their scale and 24/7 nature.
Street lighting
Street lights are a major source of light pollution. New ways of designing and providing street lighting have been developed in the last several years which:
* Reduce excessive lighting and light pollution
* Reduce greenhouse gas emissions and saves energy and money by using less electricity.
* Reducing glare to increase visibility. by directing light onto the roadway and preventing it from shining into the eyes of motorists.
The two lens illustrated
In 2003 The North American Town of Calgary committed to retrofitting ‘Envirosmart’ flat lens street lights. By changing to ‘Envirosmart’ fixtures Calgary's Program will more than cover the cost of replacing old glare-scattering street lamps by saving $1.7 million dollars CDN annually and reducing carbon dioxide emissions from gas and coal burning generators by 16,000 tons.
In the picture the light on the left is the usual dropped lens style; the one on the right has the flat lens feature. The difference is significant.
Legislation.
Unlike noise there is little mention of unwanted light as a nuisance or health hazard. However in Europe on 30 August, 2007the Republic of Slovenia adopted a Light Pollution Law. Over the past 15 years Slovenia has seen a rapid increase in light pollution, which makes the arguments of nature protection organisations striving for the adoption of a suitable Law for over 12 years essential.
The new Law prohibits lighting above the horizon into space for most luminaries and demands the use of totally shielded ones. Shielded lights produce less glare, which improves road safety and increases visibility. Less glare will also be welcome to the older population who is greatly disturbed and impeded by it. Health reasons mentioned above were cited as one of the reasons for the new law along with preservation of the night sky and of biodiversity.
Affect on Biodiversity
Birds:
The negative effect on birds is well documented. Birds may become confused by artificial lighting and it disturbs both day & night and seasonal biological rhythms.
Lighting in high rise glass office blocks are particularly harmful. It has been reported that between100-900 million birds die each year by being attracted to the light from office block windows, “Dr. Daniel Klem of Muhlenberg College has done studies over a period of 20 years, looking at bird collisions with windows. His conclusion: glass kills more birds than any other human related factor.
Bats
Bats, which are of course nocturnal, may be affected by deserting their roost if it is illuminated, or leaving the roost later, and so having less time to feed.
Insects
Insects may also be adversely affected. Many may simply fly around above light sources until they drop of exhaustion, and so fail to breed. This in turn may mean that animals further up the food chain (such as birds) suffer due to reduced prey numbers.
Plants
Plants measure and react to night length which means the duration of darkness. Therefore light at night can affect plants delayed loss of foliage, accelerated branch growth and the production of a second bloom in the autumn.
References:
data.nextrionet.com/site/idsa/RCEP%20Cos...he%20Environment.pdf
www.ncbi.nlm.nih.gov/pubmed/15325001?ord....Pubmed_Discovery_RA
www.bats.org.uk/helpline/helpline_threats_lighting.asp
content.calgary.ca/CCA/City+Living/Commu...Retrofit+Program.htm
www.obs-sbo.ca/?section=12&subsection=74&gid=6&id=16
www.ilpac.eu/index2.php?option=com_content&do_pdf=1&id=28
books.google.ie/books?id=61B_RV3EdIcC&pg...JQhC0&hl=en#PPA92,M1
www.cooke.id.au/Vision_2020_Submission.pdf
All references accessed on 28 March 2008.
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