Cancer myth: Sunscreen and cancer

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Origin of the myth

Some companies have advertised that their sunscreen products do not contain the
carcinogenic (cancer-causing) substances which other sunscreens contain. In particular,
manufacturers of holistic and all-natural sunscreen make this claim. The substances
suggested of being carcinogenic are titanium dioxides, zinc oxide, octyl methoxycimamate, oxybenzone and 4-methyl-benzylidene.
In addition, some people believe that reducing their exposure to sunlight can cause
Vitamin D deficiencies, which may also lead to cancer.

Current evidence

Sunscreen

The U.S. Department of Health and Human Services produces The Report on Carcinogens, which is a list of known or reasonably anticipated human carcinogens (cancer causing substances). None of the suspect ingredients, listed above, are included in this list.[1]  The International Agency for Research in Cancer (IARC) also does not recognise these ingredients as carcinogenic.[2] None of these chemicals has been banned by the Food and Drug Administration in the US or by the European Union.

In response to claims that sunscreen causes skin cancer, a 2003 review examined the
link between sunscreen use and melanoma. No evidence for increased risk of melanoma with sunscreen use was found. The research suggested that sun-sensitive people who have higher risk of melanoma are more likely to use sunscreens.[3]

A study published in 1999 examined the incidence of two types of skin cancer in 1621
residents of Nambour, in southeast Queensland. Participants were randomly assigned
to either apply SPF 15+ sunscreen daily or not for four and a half years. No harmful
effect of daily sunscreen use was reported. Participants who used sunscreen daily
experienced a significant decrease in squamous-cell carcinoma, and no change in
incidence of basal-cell carcinoma.[4]

The Department of Health and Ageing in Australia did a review of studies on the safety
of the titanium dioxide and zinc oxide in sunscreen. The review found that these
substances remain on the surface of the skin and in the outer dead layer, and do not
penetrate into living skin cells. Hence, even if titanium dioxide and zinc oxide were
found to cause cancer (and there is no evidence for this) they are unlikely to reach and
damage living cells.[5]  In another review, IARC concluded that there is inadequate evidence in humans for the carcinogenicity of titanium dioxide.[6]

Vitamin D

There has been some concern recently as reducing exposure to sunlight through measures such as using sunscreen may lower vitamin D levels in the body. Vitamin D is thought to prevent cancer is produced in response to UVB radiation, which is blocked from being absorbed by the skin when sunscreen is used. However, research indicates that a incidental protected exposure on the face and back of hands is enough to produce the required amounts of Vitamin D.[7, 8]

Summary

There is no evidence that use of sunscreens increases the risk of skin cancer or causes
Vitamin D deficiency.[9, 10]  Meanwhile, there is definite evidence that sun exposure increases the risk of skin cancer. Solar radiation is classified as a known human carcinogen in the U.S. Department of Health and Human Services Report on Carcinogens.1 IARC also classifies solar radiation as carcinogenic to humans.[11]

Further reading

  • Choosing and using sunscreen
    The Cancer Council WA
    http://www.cancerwa.asn.au/resources/publications/prevention/#sun
  • Use of SPF30+ sunscreens
    The Cancer Council Australia
    http://www.cancer.org.au/Healthprofessionals/PositionStatements/sunsmart/useofsunscreens.htm

References

1.   U.S. Department of Health and Human Services, 11th Report on Carcinogens. 2005,
      Public Health Service - National Toxicology Program,.
2.   International Agency for Research on Cancer (IARC). IARC Monographs on the
      Evaluation of Carcinogenic Risks to Humans
. IARC Monographs on the Evaluation of
      Carcinogenic Risks to Humans 2007 [cited 2008 02/01/2008]; Available from:
      http://monographs.iarc.fr/index.php.
3.   Dennis, L.K., L.E. Beane Freeman, and M.J. VanBeek, Sunscreen use and the risk for
      melanoma: a quantitative review
. Ann Intern Med, 2003. 139(12): p. 966-78.
4.   Green, A., et al., Daily sunscreen application and betacarotene supplementation in
      prevention of basal-cell and squamous-cell carcinomas of the skin: a randomised
      controlled trial
. Lancet, 1999. 354(9180): p. 723-9.
5.   Therapeutic Goods Administration (TGA), Safety of sunscreens containing
      nanoparticles of zinc oxide or titanium dioxide
. 2006, Australian Government -
      Department of Health and Ageing.
6.   International Agency for Research on Cancer (IARC), Carbon Black, Titanium Dioxide
      and Talc, in IARC Monographs on the Evaluation of Carcinogenic
      Risks to Humans
, IARC, Editor. 2010: Lyon, France.
7.   Sinclair, C., Risks and benefits of sun exposure: implications for public health practice
      based on the Australian experience
. Prog Biophys Mol Biol, 2006. 92(1): p. 173-8.
8.   Sollitto, R.B., K.H. Kraemer, and J.J. DiGiovanna, Normal vitamin D levels can be
      maintained despite rigorous photoprotection: six years' experience with xeroderma
      pigmentosum
. J Am Acad Dermatol, 1997. 37(6): p. 942-7.
9.   Berwick, M., Counterpoint: sunscreen use is a safe and effective approach to skin
      cancer prevention
. Cancer Epidemiol Biomarkers Prev, 2007. 16(10): p. 1923-4.
10. Green, A.C. and G.M. Williams, Point: sunscreen use is a safe and effective approach
      to skin cancer prevention
. Cancer Epidemiol Biomarkers Prev, 2007. 16(10): p.1921-2.
11. International Agency for Research on Cancer (IARC), Solar and ultraviolet radiation, in
      IARC Monographs on the Evaluation of Carcinogenic Risks to Humans
. 1997, IARC:
      Lyon, France.

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