# Can visible light cause cancer? **URL:** \ **Category:** Factual Questions\ **Created:** [March 12, 2003, 4:37am UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748 "2003-03-12T04:37:29Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Enderw24](https://avatars.discourse-cdn.com/v4/letter/e/ba9def/32.png) [@Enderw24](https://boards.straightdope.com/u/Enderw24)\ **Post date:** [March 12, 2003, 4:37am UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/1 "2003-03-12T04:37:29Z")
Microwaves can cause cancer. Gamma rays can cause cancer X-rays can cause cancer. UV rays can cause cancer. Infrared can cause cancer. So, can looking at stuff cause cancer? ---
**Author:** ![kniz](https://avatars.discourse-cdn.com/v4/letter/k/c37758/32.png) [@kniz](https://boards.straightdope.com/u/kniz)\ **Post date:** [March 12, 2003, 4:59am UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/2 "2003-03-12T04:59:41Z")
[sup] **It causes skin cancer.** [/sup] ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [March 12, 2003, 5:10am UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/3 "2003-03-12T05:10:59Z")
I’ve never heard that infrared causes cancer. There is some debate about microwave radiation (cell phones) but as far as I know, the evidence is far from conclusive. I think visible light is safe as well. ---
**Author:** ![Enderw24](https://avatars.discourse-cdn.com/v4/letter/e/ba9def/32.png) [@Enderw24](https://boards.straightdope.com/u/Enderw24)\ **Post date:** [March 12, 2003, 6:02am UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/4 "2003-03-12T06:02:36Z")
**kniz** , that’s actually the UV radiation, not the light itself. **scr4** , you’re right. Infrared may very well not cause cancer. I don’t actually know. When I refered to microwaves, I wasn’t exclusively speaking of cell phones. Rather, microwaves in general including those coming from, you know, microwaves. I was under the impression that the shielding around it was there for a reason. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [March 12, 2003, 6:45am UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/5 "2003-03-12T06:45:41Z")
UV causes cancer because DNA absorbs UV light quite well. The absorbed energy can then cause various types of DNA damage. Gamma radiation causes cancer because it’s ionizing radiation, so when it hits you, it creates ions and free radicals and all those fun things, when then in turn, again, cause other problems. I can’t think of any similar mechanism that would apply to visible light. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [March 12, 2003, 8:36am UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/6 "2003-03-12T08:36:21Z")
Microwaves, infrared and visible light are all capable of causing tissue damage. However, the mechanism is through heating. Heating can conceivably cause chemical changes leading to cancer. UV, x-rays and gamma rays are all ionising radiation, and are capable of causing chemical changes at levels well below those that would cause significant heating. The debate over cell-phones is whether microwaves can also cause chemical changes through a mechanism other than heating. Certainly infrared and visible light _are_ capable of causing chemical changes. Consider, for example, how photographic film works. Whether infrared and visible light can cause cancer, however, is as yet unproven AFAIK. ---
**Author:** ![Arken](https://avatars.discourse-cdn.com/v4/letter/a/dfb087/32.png) [@Arken](https://boards.straightdope.com/u/Arken)\ **Post date:** [March 12, 2003, 8:38am UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/7 "2003-03-12T08:38:47Z")
Could some cancers of the eyes possibly be caused by visible light? ---
**Author:** ![starman](https://avatars.discourse-cdn.com/v4/letter/s/8c91f0/32.png) [@starman](https://boards.straightdope.com/u/starman)\ **Post date:** [March 12, 2003, 11:25am UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/8 "2003-03-12T11:25:45Z")
I doubt that light could cause cancer at wavelengths longer than UV. That is, UV causes cancer (IIRC) by producing free radicals, which damage DNA. Normally, the damage will be repaired, no problems. If, however, a base is placed in the wrong sequence, then cancer can occur. Visible light does not have the energy required to break the required bonds to release free radicals (O2- etc). -Oli ---
**Author:** ![Andy](https://avatars.discourse-cdn.com/v4/letter/a/aeb1de/32.png) [@Andy](https://boards.straightdope.com/u/Andy)\ **Post date:** [March 12, 2003, 11:42am UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/9 "2003-03-12T11:42:00Z")
I don’t know of a mechanism for sequence disruption through UV light, but adjoining base pairs do undergo [2+2] photocycloaddition ie they become stuck together. This happens frequently, and only causes problems when the repair enzymes miss such a site or are overwhelmed through the number of them. ---
**Author:** ![Urban\_Ranger](https://avatars.discourse-cdn.com/v4/letter/u/e9c0ed/32.png) [@Urban\_Ranger](https://boards.straightdope.com/u/Urban_Ranger)\ **Post date:** [March 12, 2003, 11:55am UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/10 "2003-03-12T11:55:41Z")
It’s the energy of the photon, people. The shorter the wavelength, the more energetic the photon is. That’s why UV can break the bonds in organic compounds, causing damage, while visible light can’t. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [March 12, 2003, 12:00pm UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/11 "2003-03-12T12:00:14Z")
**Urban Ranger** : that’s far too simplistic for the debate at hand. ---
**Author:** ![curly\_chick](https://avatars.discourse-cdn.com/v4/letter/c/7ba0ec/32.png) [@curly\_chick](https://boards.straightdope.com/u/curly_chick)\ **Post date:** [March 12, 2003, 12:37pm UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/12 "2003-03-12T12:37:03Z")
If visible light caused cancer, surely we would all be extinct. Life has been lived on this planet, in light, for however long it is and if visible light ever caused carcinogenic mutations, then we have evolved and that particular mutation is now no longer in the human genome. From my understanding any mutation can spontaneously recur in any species, but en masse, fatal mutations are ideally not passed onto the next generation. Of course, evolution is not an exact science and the technological developments of man, both good and bad bring new challenges to the genetic resilience of man, as a species. Put another way, we now know that X rays cause cancer. X rays are not a natural phenomenon, bathing the whole planet for 12 hours a day, man has to make them. Visible light is a natural phenomenon. So my WAG is that light does not cause cancer, unless you are unlucky enough to have had that particular bit of natural mutation going on in your genome, in which case, your outlook would be pretty bleak. ---
**Author:** ![Andy](https://avatars.discourse-cdn.com/v4/letter/a/aeb1de/32.png) [@Andy](https://boards.straightdope.com/u/Andy)\ **Post date:** [March 12, 2003, 12:47pm UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/13 "2003-03-12T12:47:07Z")
> [@](#): > > \*Originally posted by Urban Ranger \* > It’s the energy of the photon, people. The shorter the wavelength, the more energetic the photon is. That’s why UV can break the bonds in organic compounds, causing damage, while visible light can’t. In organic compounds, UV light can cause electron excitation, but I’ve never seen an example where it causes homolytic (-\> radicals) or heterolytic (-\> ions) cleavage. That’s not to say it can’t happen of course. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [March 12, 2003, 12:50pm UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/14 "2003-03-12T12:50:03Z")
By exactly the same reasoning, **curly chick** , UV can’t cause cancer either. But it _does_. UV is a perfectly natural phenomonon that can cause melanoma, amongst other things. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [March 12, 2003, 1:59pm UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/15 "2003-03-12T13:59:12Z")
Certainly visible light can aid chemical reactions. That’s why you’re supposed to get some sunlight on you – visible light aids in the production of vitamin D. I don’t recall the details, though. See Harris’ book **Good to Eat** , or a book on human biochemistry. I doubt if it’s bond-breaking (you need UV for that, as has been mentioned above). It might give the extra shove needed to get you over the reaction energy threshold. If heat energy can help shove you over that Boltzman curve, visible quanta ought to do it, too. Infrared would have less to contributre being lower energy. I’ve never heard any clsims that visible or IR light cause cancers. I know that people are concerned about flashing illumination for endoscopes and lasers for surgery around inside the body, because they’re not sure what effect they will have in that normally-dark environment, but I’ve never heard anyone actuallty finding any bad effects from it yet. ---
**Author:** ![curly\_chick](https://avatars.discourse-cdn.com/v4/letter/c/7ba0ec/32.png) [@curly\_chick](https://boards.straightdope.com/u/curly_chick)\ **Post date:** [March 12, 2003, 3:02pm UTC](https://boards.straightdope.com/t/can-visible-light-cause-cancer/160748/16 "2003-03-12T15:02:10Z")
> [@](#): > > \*Originally posted by Desmostylus \* > \*\*By exactly the same reasoning, **curly chick** , UV can’t cause cancer either. But it _does_. UV is a perfectly natural phenomonon that can cause melanoma, amongst other things. \*\* I never said natural phenomena couldn’t be carcinogenic. UV radiation causes melanoma in susceptible individuals. Or to put it in exactly the same terms as I used in my WAG, it is carcinogenic if you have _that particular bit of natural mutation going on in your genome_ I still think though, that the fact we are all still here, on the planet, aeons after the dawn of man, is significant in this case. If the mutation which renders visible light carcinogenic in man was a common set of base pairs, man would not exist as we know today.