Light at Night and Breast Cancer: The Israel Study
Jacob Schor, ND, FABNO
February 24, 2008
Living in the American west it is difficult to comprehend how small a country Israel is. We once drove some young Israeli relations to Denver from San Francisco. After studying the map carefully, they assumed we could stop off in Yosemite for lunch and expected to make Denver by nightfall. They could not comprehend the scale of things in our country.
Likewise, it is difficult for us to understand how small Israel is; everything is jammed into so tiny an area. I recall watching the sun set from a hilltop in the Northern Galilee several years ago and then watching as the lights came on in the towns and communities between us and the Mediterranean. Rather than urban sprawl as in the United State, we could make out a multitude of small discrete communities; Arab towns, Druze villages, Jewish Kibbutzim and Moshavs, their lights all floated in the darkness. We counted close to two dozen distinct communities from our vantage point, each one a world to itself.
I think back to this as I marvel at a paper published in the current issue of Chronobiology. The results of this study, though what we might predict, exceed anything that I would have guessed.
Itai Kloog and colleagues at the University of Haifa used night time satellite photos taken by NASA to estimate the Light at Night (LAN) levels in 147 communities in Israel. They compared the LAN levels with rates of breast cancer. They correctly assumed breast cancer would be affected by nighttime lighting.
They found a strong positive association between LAN intensity and breast cancer rates. The breast cancer rate in communities with average night lighting were 37% higher than in communities with the lowest amount of light; and in the most well lit communities the rate was another 27% higher. That is they showed a 73% higher breast cancer incidence in the highest LAN exposed communities compared to the lowest LAN exposed communities. 
Certainly the idea that lighting will increase breast cancer risk is no surprise. I’ve been writing about this off and on for years. The hypothesis that light suppresses melatonin levels raising cancer risk has been pretty well established for the two decades.
But still, that one could measure the difference in cancer risk from satellite photos is still mind-boggling. Keep in mind this was nighttime light intensity outside, seen from space. They made no attempt to measure indoor lighting intensity.
It is so well established that working ‘night shifts’ increases cancer risk that the World Health Organization last December classified ‘shift work’ as a "probable carcinogen."
Abraham Haim, one of the Haifa scientists involved in this study, brought up a frightening prospect in a recent Washington Post interview. Haim questioned the recent push by many countries, including the US, to switch to energy-efficient fluorescent bulbs.
‘These energy saving bulbs suppress melatonin production more than conventional incandescent bulbs. "This may be a disaster in another 20 years," Haim said, "and you won't be able to reverse what we did by mistake."’ 
Satellite Photos of Earth at Night:
Links to past articles on melatonin and cancer:
Melatonin and Breast Cancer, September 2007
Seasonal Affective Disorder and Suicide Season
Sleepless in Park Hill
- Chronobiol Int. 2008;25(1):65-81. Light at Night Co-distributes with Incident Breast but not Lung Cancer in the Female Population of Israel. Kloog I, Haim A, Stevens RG, Barchana M, Portnov BA.
- Lights at Night Are Linked to Breast Cancer: Study Bolsters Theory About Interference With Production of Key Hormone. Rick Weiss Washington Post. February 20, 2008;