The link between retinyl palmitate, sunlight and the increased risk of cancer has been confirmed by the National Toxicology Program. The NTP’s report comes after a year long study on mice.

Whether retinyl palmitate in sunscreens is carcinogenic is a controversial issue. The FDA has been reviewing data from several studies on a potential link between retinyl palmitate and cancer risks since July 2009. The issue has been hotly debated between the Environmental Working Group (EWG) and the cosmetics industry. Because of this I’m going to quote the NTP verbatim even though its report, “On The Photococarcinogenesis Study of Retinoic Acid and Retinyl Palmitate” which was peer reviewed yesterday (1/26/11), is marked as “not for attribution”.

The study:

"Groups of 36 male and 36 female Crl: SKH-1 (hr–/hr–) hairless mice were irradiated 5 days per week (Monday through Friday) in the morning for 40 weeks with SSL at levels of 0.00, 6.85, or 13.70 mJ•CIE/cm 2 that were emitted from glass-filtered 6.5 kW xenon arc lamps.  The mice received topical applications of control cream or creams containing 0.001% (w/w) RA or 0.1%, 0.5%, 1.0%, or 2.0% RP to the dorsal skin region in the afternoon of the same days of irradiance exposures."

The conclusions:

Retinoic Acid - Compared to the control cream, RA enhanced the photocarcinogenic activity of SSL and UVB in SKH-1 mice based upon earlier onsets and increased multiplicities of in-life skin lesions.

Retinyl Palmitate - Compared to the control cream, RP enhanced the photocarcinogenicity activity of SSL and UVB in SKH-1 mice based upon earlier onsets and increased multiplicities of in-life skin lesions and increased incidences and multiplicities of squamous cell neoplasm’s.

This conclusion is similar to results of earlier studies on mice. However, other research (not always independent, it has to be said) contradicts those finding. For more, see our post on retinyl palmitate and skin safety.

The EWG issued a statement yesterday saying that it "recommends 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."