Does the usage of sunscreen cause skin cancer?

Question

I have heard that usage of sunscreen products causes skin cancer. Is this true, and if so, what are the ingredients in it that are reason for such a medical condition. Are there any safe products or methods of application that they don't harm skin.

Answer 1

The potential health risks of sunscreen include:

• The absence of UVA filters combined with a longer exposure time of the sunscreen user^{1995, 2005, 2007, 2007}.
• Suppression of the skin's production of melanin, a natural broad-spectrum photoprotectant^{1995, 2004}.
• Skin penetration (free radical generation) by sunscreen chemicals^{1996, 1997, 2006, 2007}.

• Cytotoxic and carcinogenic effects of nanoparticles (zinc oxide (ZnO) and titanium dioxide (TiO2) toxicity) ¹⁹⁹⁹.

  However TGA study from 2006 (PDF) concluded:

  There is evidence from isolated cell experiments that zinc oxide and titanium dioxide can induce free radical formation in the presence of light and that this may damage these cells (photo-mutagenicity with zinc oxide). However, this would only be of concern in people using sunscreens if the zinc oxide and titanium dioxide penetrated into viable skin cells. The weight of current evidence is that they remain on the surface of the skin and in the outer dead layer (stratum corneum) of the skin.

• DNA damage causing skin cancer (carcinogenic effects of sunscreen ingredients related to vitamin A)²⁰¹². Read below.

• Vitamin D deficiency^{2002, 2002, 2007}.

  The strong promotion of limiting sunlight exposure because of increased risk of skin cancer has resulted in the widespread use of sunscreens. Although sunscreens are very beneficial in reducing skin damage to excessive exposure to sunlight, they also can markedly reduce the photosynthesis of vitamin D3 in the skin.

  When used properly a sunscreen with a sun protection factor of 8 reduces the skin's ability to produce vitamin D3 by 97.5%^{Holick 2002}.

• Oxybenzone (benzophenone-3) toxicity concerns.

  The CDC study from 2008 reveals that 97% of Americans are contaminated with a widely-used sunscreen ingredient called oxybenzone that has been linked to allergies, hormone disruption, and cell damage.

  EWG research shows that 84% of 910 name-brand sunscreen products offer inadequate protection from the sun, or contain ingredients, like oxybenzone, with significant safety concerns. Although oxybenzone is most common in sunscreen, companies also use the chemical in at least >500 other personal care products.

  Chemical was detected in the urine of nearly every study participant. Typically, women and girls had higher levels of oxybenzone in their bodies than men and boys, likely a result of differences in use of body care products including sunscreens.

  A companion study released a day earlier revealed that mothers with high levels of oxybenzone in their bodies were more likely to give birth to underweight baby girls (Wolff 2008).

Retinyl palmitate (vitamin A palmitate) controversy

The FDA's NCTR and NTP in 2009 posted on the NTP website data from FDA’s long-term photocarcinogenicity tests of retinyl palmitate on UV-exposed laboratory animals. In the studies, high doses of topical retinyl palmitate (a form of vitamin A) were shown to accelerate cancer (skin tumors or lesions) in lab animals that grew significantly faster than mice treated with vitamin-free cream (NTP 2009).

^{Source: EWG analysis of data from FDA photocarcinogenicity study of retinyl palmitate (NTP 2009). Percent decreases in time to development of a significant tumor or lesion (for animals exposed to cream laced with retinyl palmitate) are relative to that for animals exposed to cream free of the compound.}

Scientists have known for some time that retinyl palmitate can spur excess skin growth (hyperplasia), and that in sunlight it can form free radicals that damage DNA (NTP 2000).

Previous data were preliminary, however in 2011 the link between retinyl palmitate (RP), sunlight and the increased risk of cancer has been confirmed by the National Toxicology Program after a year long study on mice.

The EWG and and New York Senator Chuck Schumer have called attention to the fact that high doses of topical retinyl palmitate were shown to accelerate cancer in lab animals and EWG published the following statement (which was scheduled for immediate release):

A key independent science advisory panel has voted to confirm federal researchers' conclusion that retinyl palmitate, a form of vitamin A found in two-fifths of U.S. sunscreens, speeds the development of skin tumors and lesions when applied to the skin in the presence of sunlight.

"A compound that causes skin damage and tumors on sun-exposed skin has no place in sunscreens or other daytime skin products," said Jane Houlihan, EWG senior vice president for research.

More than 200 sunscreens from 44 companies listed vitamin A or retinyl palmitate on their labels in 2010, according to EWG's analysis of beach and sport sunscreens with SPF ratings of 15 or higher.

In light of those findings, EWG recommends that manufacturers of cosmetics, sunscreens and other personal care products remove retinyl palmitate from all products to be used on sun-exposed skin and that consumers avoid buying products that contain this chemical.

Despite of that sunscreen controversy, another study from 2010 by JAAD determined that "there is no convincing evidence to support the notion that [retinyl palmitate] in sunscreens is carcinogenic.". Therefore EWG has since refuted this analysis directly⁽²⁰¹¹⁾.

A panel of independent scientists convened by the NTP in January 2011 unanimously confirmed the study’s conclusion that retinyl palmitate “enhanced the photocarcinogenic activity” of sunlight (NTP 2011).

The strong scientific consensus that has formed around the NTP-FDA vitamin A study has afforded the FDA an exceptional opportunity to take a bold public health stand on a cosmetic ingredient that has proven harmful in multiple studies⁽²⁰¹¹⁾.

Since then the FDA has set a minimum performance standard for sunscreens that use the term “broad spectrum” to denote that they provide a measure of protection from ultraviolet-A rays.

The most recent government scientific study from August 2012 by NTP has demonstrated that retinyl palmitate speeds photo-carcinogenic effects on test animals and concluded that diisopropyl adipate increased incidence of skin tumors in mice, and the addition of either retinoic acid or retinyl palmitate both exacerbated the rate and frequency of tumors^(2012),(PDF). The study (Photococarcinogenesis Study Of Retinoic Acid And Retinyl Palmitate) was conducted at a federal research center co-hosted by the FDA and NTP, found that mice treated with small doses of retinyl palmitate and ultraviolet light developed skin tumors faster than untreated, light-exposed mice or those treated only with a control cream. There were more numerous tumors on every animal treated with retinyl palmitate.

And the conclusion was:

Under the conditions of these studies, the topical treatment of SKH-1 mice with the control cream resulted in earlier onsets of in-life skin lesions and higher incidences and multiplicities of in-life skin lesions, when compared to untreated controls, in the absence and presence of SSL.

^{This graphic presents skin tumor onset data for female and male mice exposed to the amount of UV light equivalent to 30 percent of the UV dose that causes sunburn in people. The bottom axis indicates weeks of retinyl palmitate + light treatment. (NTP 2010).}

The sunscreen industry and its paid consultants have rejected the NTP findings.

Whether RP in sunscreens is carcinogenic is a controversial issue for the cosmetics industry and FDA is reviewing data from several studies since July 2009. Nearly 33 years after it began considering regulation of sunscreen products, the FDA has yet to review or certify the safety of chemicals formulated into sunscreen products.

EWG supports FDA’s proposal for further testing to determine the potential phototoxicity and/or photocarcinogenicity of diisopropyl adipate. However, more tests are likely to take some years with detailed toxicity testing with action to remove harmful ingredients from body care products. And until the government takes decisive action, consumers can have no confidence that the regulatory system for sunscreens and cosmetics is screening out suspect ingredients.

See also:

• What scientists say about Vitamin A in sunscreen at EWG
• Potential health risks of sunscreen at Wikipedia
• Retinyl palmitate (vitamin A palmitate) at Wikipedia
• Sunscreen: Potential risks at Wikipedia
• Does sun screen cause cancer? at Skeptics SE
• Is there a health risk from nanoparticles in sunscreens? at Skeptics SE
• 2010: Possible link between ingredient in sunscreen and skin cancer: Schumer at NY Daily
• 2010 article: Retinyl palmitate sunscreen and skin safety
• 2011 article: New study links retinyl palmitate to cancer

Answer 2

Wearing sunscreen while out in the sun cuts your risk of skin cancer.

As others have pointed out, there are some potential risks associated with wearing sun screen. However, if you are out in the sun, these risks are far outweighed by the risk of UV exposure.

This Skeptics.SE answer has a very comprehensive overview of the facts, in particular citing a recent critical review that assessed all studies related to sun screen to date. This was the conclusion:

Given sunscreens prevent Squamous cell carcinoma (SCC) and sunburn (although this study claims it is inconclusive in preventing melanomas and and basal cell carcinoma (BCC)), their use seems justified despite the fears.

Answer 3

Your question sounds like it generalizes about all sunscreen products. But not all sunscreen products are created equal.

I understand your concern because according to this report from the National Institute of Health

Recent reports about sunscreen safety have received widespread media attention

Media attention will lead to opinion based questions. So here's my recollection of opinions + facts:

Remember that anything that damages your DNA has the potential to cause cancer, excess and misuse of sunscreen can cause cancer.

After reading a bit from experts on the topic my non-expert recommendation would be:

1. Use it in moderation. Use sunscreen only when you are going to be exposed directly to the sun for more than a few minutes on peak sun hours (10 am to 2 pm). Or if you are going to be exposed for several hours regardless of peak hours.
2. Use it in the form of ointment/gel/liquid/unguent. Don't use sprays because you should never be breathing that stuff. Use it in the skin only. Don't use it in sensible areas that could absorb it faster, like areas where there are mucous tissue (eyes, mouth, genitals, etc). You should never be eating that stuff.
3. Use inorganic sunscreen because organic has a higher potential to cause allergies and/or disrupt your hormones.

Disclaimer: My informed opinion is no substitute for professional advice. Consult your physician or GP.

References obtained from pubmed, and there's some expert's opinion you can read in the following article (it is not licensed under creative commons so that's why I paraphrased it), the article is also directly referenced by the National Institute of Health so I'd say is somewhat reliable:

Direct link:
http://www.cutis.com/?id=27148&tx_ttnews[tt_news]=372913&cHash=2f78ef616315bff3cc04ef761a0611bd

If the direct link doesn't work enter:

• http://www.cutis.com/
• And search for "sunscreens-causing-cancer-the-facts"