I’ve heard this twice now; that sunscreen is actually more dangerous than sun exposure.
Sounds like BS to me, but I want to be sure. After all, I do put the stuff on every day (lots of it! :eek: ). It’s hard to imagine that it could be more hazardous than the known devil of skin cancer.
So, how dangerous is sunscreen?
I don’t promise that this one won’t be shuffled over to another forum, but I have to ask:
WHY do you put it on every day? :eek: :eek:
A quick perusal doesn’t show anything I’d be nervous about, and the FDA does check these things.
Part of my undergraduate thesis was about sunscreen. (I designed an experiment for college-level chemistry courses where students make sunscreen.) Formerly, many sunscreens contained PABA, para-aminobenzoic acid; many sunscreens now say ‘PABA-free’ because some people are allergic to PABA. Also, PABA does not provide protection against UVA rays and may break down in sunlight to form free radicals that could promote aging and cancer. PABA is not stated as carcinogenic on its MSDS.
Modern sunscreens use other compounds such as avobenzone and octyl para-methoxycinnamate. The concern (stated most often by advocates of ‘natural’ and ‘alternative’ medicine) here is that these compounds will also break apart and release free radicals that could cause cancer. Many chemicals will break apart when exposed to UV light, so it is not surprising that sunscreens may decompose after long exposure to UV radiation. It is very important to stress that any risk that sunscreens might pose would be far less than the risk of exposure to UV light without sunscreen. If you’re afraid of any possible dangers of sunscreen, I’d recommend limiting your exposure to the sun and wearing light-colored protective clothing along with a small amount of sunscreen on unprotected areas. (If you’re really afraid, use a non-organic sunscreen such as zinc oxide or titanium dioxide on unprotected areas.)
One website that claims sunscreens cause cancer suggests that vitamin C is a safe, natural alternative to ‘chemical sunscreens’. This is wholly based on the idea that vitamin C is natural. It does not have the chemical properties that make a good sunscreen. It would block some UV radiation, but not as much as synthetic sunscreens. And, just like any other chemical, it would have the potential to break down under UV light. Perhaps the argument is that vitamin C would protect against free radicals because it is an antioxidant in the body, but ‘chemical’ sunscreens are just as likely, perhaps even more likely, to react with free radicals as would topical vitamin C.
Later on, if you want, I can do a Medline search and get some cites.
Most women I know wear moisturizer with at least SPF 15. Preventive medicine.
I’ve been told to wear sunscreen every day. My dad, mom and brother have all had skin cancer and I have super fair skin.
Better safe, right?
I’ve also heard that people in high risk areas (like Australia) need to wear it even more.
More than every day! How can that be? 
Maybe every day and every night?
And quite possible, I know some women who put on moisturizer before bedtime.
perhaps one of the biggests dangers with sunscreens is that it encourages you to stay out longer than you should.
Having said that, the new transparent UV creams contain nano-sized titanium or zinc oxide particles, that are small enough to enter living cells. No one is quite sure whether these are more dangerous than the normal sized particles.
some background http://online.sfsu.edu/~rone/Nanotech/nosmallmatter.html and http://www.etcgroup.org/article.asp?newsid=392
Just like Vioxx? 
I work outdoors in a national park… I guess every day is an exaggeration; I wear sunscreen every day Monday-Friday, and since I’m often doing outdoor things on weekends too (e.g. this Saturday a birding class and last Saturday kayaking), I pretty much wear it 6 days a week. :eek:
Would I be right in summarizing that people are afraid of the possibility that sunscreen may break down into free radicals and cause cancer, but no one has ever shown that it does?
I think I’ll keep blocking out the known carcinogen of UV.
Thanks to all for your helpful responses!
Moon screen? I’ll use that the next time I work on my lunar power collector cells.
I’ve seen this mentioned in a number of places. It’s part of the “false security” syndrome, the feeling that danger has been taken care of so no further precautions need to be made.
There’s a further aspect of this in that more sunscreen is needed for true protection that most people think is the case.
If putting on inadequate amounts of sunscreen causes you to stay outdoors too long, then indeed sunscreen is dangerous. But only as part of the general rule that it is more dangerous to be an idiot than not to be an idiot.
Yes, like Vioxx.
Yes, like Vioxx.
FDA scientists recognized problems with Vioxx early on. and wrote reports criticial of it, and recommending further testing before approving it. But the reports were suppressed by political appointees, and the scientists who wroute them were harrassed at the agency.
Exapno Mapcase: I had a friend who knew someone who was studying that for a thesis. The idea of homeostasis (a response that corrects a change to a system in such a way as to reduce the effect of the stimulus) was involved. She was interviewing women who were taking a self-defense course to see if they might be more likely to take risks after having taken the course. I suppose the same argument might be made involving condoms, but in that case I think the logic is faulty. (Would wearing a seat belt encourage a driver to drive more aggressively, or more often? Not likely, but using a seat belt does reduce the risk of serious injury if the driver gets in an accident.)
I do think that sunscreen may encourage people to expose themselves to more UV radiation than they would without sunscreen, particularly because the major deterrent to exposing oneself to the sun (getting a sunburn) is reduced when sunscreen is used. UV radiation can still cause damage even if no sunburn occurs, and some UV radiation will still penetrate the sunscreen, particularly if not enough is used or if it is washed away. If a person is simply going to be outside for a while in the sun, sunscreen is a good idea, as well as light-colored protective clothing. (Avoiding the peak times for UV radiation and minimizing your time outside during high-UV days is also a good idea.) But someone who still insists on suntanning or otherwise spending large amounts of time in the sun without adequate protection is going to incur some DNA damage even if they do use sunscreen. (The damage will be substantially less, though, if sunscreen is used.)
scm1001: Titanium dioxide is used in toothpaste and baked goods (and white paint, for that matter). It’s considered safe to eat, though that might be because it’s poorly absorbed.
I don’t know the answer, but I’ve seen arguments to that effect. Or that mandatory motorcycle helmet laws cause cyclists to drive more recklessly. Or that people think that with airbags they don’t have to wear seat belts.
It’s incredibly difficult to sort out cause and effect in these situations. I do believe in the Law of Unintended Consequences, though, and I also believe that if people can find a way to be idiots they’ll take a short cut there every time.
As a preface, I wear concentrated vitamin C under and SPF 60 sunscreen, EVERYDAY, so take this post as you will.
As far as I’m concerned:
It’s possible that sunscreen may cause cancer - there’s no definitive evidence at this point.
Excess sun exposure without sunscreen WILL cause cancer in a portion of the population - that’s a medically recognized fact.
I’m going to put my $$ on the WILLs, rather than the mays, at least until further evidence is out there.
Also, by “more than every day” I assume they mean “applied twice or three times a day.” Sunscreen is only effective on the skin for a certain period which is reduced by swimming or sweating.
scm1001 has a good point. The biggest danger of nanotech (at least for now) is that nano-particles often have different chemical properties than larger particles of the same substance. Ideally, all nano-substances will be tested for toxicity and other dangers before being introduced but I suspect we’ll learn the hard way that that has to be done.
One danger of sunscreen not mentioned yet is that is blocks the production of vitamin D in your skin.
Normal titanium dioxide is indeed very safe because the particles as you said are very large (1-50 microns) and not absorbed. They are white in appearance. Transparent nano-sized titanium dioxide is 100 X smaller and can be absorbed by cells in principle. Inside it could cause a lot of photodamage