Interesting article about blue lights causing cancer. It mentions outdoor LED, cell phones/tablets. What about blue spectrum lights on my reef tank that I spend hours in front of?
Link:
https://www.cnn.com/2018/04/27/health/artificial-blue-light-prostate-breast-cancer-study/index.html
This is a new riff on a relatively old story combined with a bit of misunderstanding by the CNN writer.
It has been known for quite some time now from several very large studies (e.g, the Nurses Health Studies) that disruption of normal circadian rhythms is associated with a variety of adverse health outcomes, including cancers such as breast and prostate cancer. By disrupted circadian rhythms, I mean working night shifts, being a night owl, basically working or being out and about when your body clock says you should be sleeping. The International Agency for Research Cancer (IARC) designated disrupted circadian rhythms as a probable human carcinogen in 2007.
It is also known that what disrupts circadian rhythms the most is light in the blue spectrum because this inhibits production of the hormone melatonin, which is normally responsible for telling your body that it is time to sleep. More blue light = less melatonin -> poorer sleep and perhaps other issues.
What the cited study shows is that people with the highest POTENTIAL (not measured) exposure to blue light also had the highest risk of cancer (although the increase was relatively small, less than 2-fold) and that it did not matter whether this was occupational exposure (working the night shift) or simply being out and about in places where the street lights had been changed to LEDs. There are some uncertainties in the results: the outdoor light estimates from the International Space Station did not distinguish where the light was going (i.e., mostly up, mostly down, mostly lateral, etc). Indoor exposure estimates were based on questionnaires which is typical in many epidemiological studies. This is often the best that you can do, but actual measurements of exposure would produce more accurate estimates of the effects.
What the study did NOT distinguish was whether it was exposure to blue light itself that led to the increased cancer risk or disrupted circadian rhythms by the blue light that led to the increased cancer risk (more likely, I believe). It is likely that the key question to consider is disrupted circadian rhythms.
So what should we do about our reef tanks? I'd say first, ask whether you are sleeping well and soundly at night. If you are, then probably no cause to change much about your environment. The less blue light at night, the better you will probably sleep, overall so it would not hurt to reduce blue spectrum light from your home lighting, phone, tablet, etc.
If you have difficulty falling asleep, or don't sleep soundly, I'd say it is probably a good idea to change the color spectrum of the lights in your home to warm white (2700K-ish) such as the common LED bulbs you can buy at most big box stores and reduce the length of time your actinic lights are on at night. Perhaps shut them off at 10 PM or so. Make sure your phone, computer, tablet etc use a blue-light reducing app for reading at night.
All in all, not a huge cause to worry, but worth thinking about. Probably not the highest priority item in our environments to consider eliminating to reduce the risk of adverse health effects, but a relatively easy change to make.