Fingerprint scanners use one of two methods
- optical (light)
See HowStuffWorks and note that this manufacturer has both "E-Field" and "Active Cap" sensors.
So not all fingerprint readers shine light on your fingers.
Also, patents such as this mention "light" and have no mention of "infra-red" so at first glance it seems that some sensors may be using wavelengths of light that are not infra-red.
Some Infra-red light is the same as radiant heat. I'm unsure this would be useful to shine on a warm object like a finger. It would be better to use a passive-IR detector to capture the IR-radiation (heat) emitted by the finger. This is how some night-vision cameras work. In this case there would be no additional IR received by your finger.
Compare with Passive Infra-Red (PIR) detectors used in automatic lights and burglar alarms.
Infra-Red light is commonly used in domestic heaters and in heaters used to raise chicks.
Examples. Examples. So it would be surprising if these were a hitherto unknown cause of cancers.
Heating a finger could conceivably cause burns (though biometric scanners are unlikely to need high-powered IR emitters and so are probably unlikely to have circuits capable of carrying the electrical current needed to deliver a harmful heating effect).
The power emitted by a typical "high-powered IR emitter" is 20 mW (0.02 W). If this is all shone at a fingertip (area 0.0001 m²) with 100% efficiency (impossible) that gives 200 W/m². Compare this with the heat naturally emitted by your skin which is 40 to 800 W/m²
When I search for "Infra-Red and Cancer" I only get results concerning the use of Infra-Red light to treat (i.e. attempt to cure) cancer! Example
Infra-red light is non-ionizing as pointed out by Nico in a comment below. This means it cannot cause the sort of damage to DNA molecules typically needed to cause cancers.
Skin cancer has been associated with UV-light (specifically UV-B), not IR light. Maybe there is some confusion.
See links referred to in Wikipedia
To work out any health implications you'd need to know
- does the specific fingerprint sensor used actually emit IR light
- what frequency
- what power
- how long is the finger illuminated
- how many time a day/week/month/year does each person use the sensor
I can't find any reference that IR light causes cancer. As explained above, this seems very unlikely.
wrong about device
The article mentioned shows a picture, not of a fingerprint scanner but of a different device - a hand geometry scanner. I believe these scanners typically use visible light and cameras not Infra-Red.
The text of the article talks only about "fingerprint devices"
wrong about "exposure to infrared rays might cause cancer"
This seems to be an error - no references in the article.
other issues may be legitimate but grossly overstated
The anonymous dermatologist warns about transmission of "skin diseases" - this may be a legitimate concern (though the same concerns would presumably apply to doorknobs and banknotes, etc). Some respondents suggested the device is treated to reduce the chance of this.
The article reports
In biochemistry, a fingerprint is defined as a pattern of fragments obtained when a protein is digested by a prototypic enzyme, usually observed following two-dimensional separation by chromatography and electrophoresis.”
The reporter or editor seems to be introducing information that is completely irrelevant to the operation of fingerprint scanners. At the very least they fail to explain how it can possibly be relevant. This casts some doubts on the reporters competence and impartiality.
wrong about X-rays
Physicians also said these devices emit X-rays directly at the hand
If the ridiculousness of this (in the context of fingerprint scanners) is not evident to anyone reading this, please say so in a comment.
(what follows is personal opinion - you can disregard it)
Whatever the hazards (if any) of fingerprint scanners - this article is, on the whole, not credible. It is probably a good example of the worst kind of journalism. It seems to deliberately stir up concern and even panic, prey on peoples natural apprehensions about new technologies and does not make any attempt to give the makers of the devices any opportunity to respond to the claims. For the sake of it's citizens, I hope it is untypical of journalism and science in Saudi Arabia.