Friday, December 04, 2015

Possible risks in using LED light to monitor your heart rate?

I had been wearing an activity tracker on my wrist to measure the number of steps I walk daily, for over a year. It has surely given me an incentive to walk more. More recently, I upgraded myself to wear the next version, which also measures my heart rate and displays it when asked to do so. I was aware that I was exposing myself to round-the-clock LED light over a few square millimeters of my skin. After a couple of months of this exposure, I noticed that the area exposed to the LEDs had developed a tan. I was surprised; having dark brown skin, I had not expected it. I looked up information given out by the manufacturer, and it said that the energy put out by the LEDs was so small it was harmless, but I was the one who had his skin in this game, literally! I wanted to be more careful.
I do not know the exact amount of energy used; suppose it is 20 milliwatts and that it is spread over two square millimeters. The energy density would then be about 10 milliwatts per square millimeter. Compare it with 140 Watts of Sunlight spread over a square foot; that is about 1.56 milliwatts/square millimeter. Besides that, I am unlikely to sit in the Sun giving me 140 Watts/square foot of radiation round-the-clock! Governments have advised people to be careful in sunbathing, to reduce the incidence of skin cancer. Visit The Surgeon General’s Call to Action to Prevent Skin Cancer. In many countries, where the weather encourages frequent sunbathing, deaths due to skin cancer exceed the number of traffic deaths.
After thinking all this out, I read the documentation again and found I could turn heart-rate monitoring on and off as I liked. Now, I keep it switched off most of the day and turn it on only during exercise sessions. I have also given up wearing the gadget during sleeping hours. You think I am paranoid? Give me a few reliable studies by credible and independent medical researchers, concluding there is no risk. I will forget my worries!
Subject to standard ethical safeguards, it may be worth doing a small-scale animal experiment exposing rats to the same HR monitor that I have been exposed to. The rats might be smarter and bite the strap off before it is too late! The experimenters might have to take some precautions.
It may be necessary to have the rats’ exposed skin examined by pathology labs to identify any possible risks from the exposure.
I would also suggest that students interested in doing the experiment to send their proposals to the manufacturers of the devices asking for a grant of 60 devices for use in the experiment. You can assure them that you will acknowledge their contributions when you publish your findings. The results might be interesting!
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Srinivasan Ramani said...

There is a follow-up item in regard to this post - a photograph of skin damage on my wrist caused by the activity tracker. I could not include that photograph in this comment and hence made a new post. Visit Possible risks in using LED light to monitor your heart rate Post No 2

Srinivasan Ramani said...

It is almost a year since my first post on possible risks in using fitness trackers that do LED monitoring of your heart rate (HR). Now, I control the the amount of time the LED's are on by switching off HR monitoring when I am not taking a walk. Despite this the black spot on my wrist has been getting darker. I have a couple of suggestions:

1) Use a moistening cream on the wrist. It controls the drying up of the skin exposed to LED light.

2) The makers of fitness trackers should modify their software to have the LED's on only when you bring the HR display on. Rest of the time, the LED's could be off. This will reduce risks.