Most chemical sunscreens contain, as UVA and UVB blockers, from 2 to 5% of compounds such avobenzone, benzophenone, ethylhexyl p-methoxycinnimate, 2-ethylhexyl salicylate, homosalate, octyl methoxycinnamate, oxybenzone (benzophenone-3) as the active ingredients.Benzophenone (and similar compounds) is one of the most powerful free radical generators known. It is used in industrial processes as a free radical generator to initiate chemical reactions. Benzophenone is activated by ultraviolet light energy that breaks benzophenone's double bond to produce two free radical sites. The free radicals then react with other molecules and produce damage to the fats, proteins, and DNA of the cells - the types of damage that produce skin aging and the development of cancer.
Adding to the problem is that large amounts of applied sunscreens can enter the bloodstream though your skin. In the 1970s, Prof. Howard Maibach warned that up to 35 percent of sunscreen applied to the skin can pass through the skin and enter the bloodstream but this had little effect on sunscreen promotion or safety testing. (Maibach, H. "NDELA-Percutaneous Penetration." FDA Contract 223-75-2340, May 19, 1978) The longer sunscreen chemicals are left on the skin, the greater the absorption into the body. (Bronaugh, R.L., et al. "The effect of cosmetic vehicles on the penetration of N-nitrosodiethanolamine through excised human skin, J Invest Dermatol; 1981; 76(2): 94-96.) This may be a factor in the large increases in cancer (breast, uterine, colon, prostate) observed in regions, such as Northern Australia, where the use of sunscreen chemicals has been heavily promoted by medical groups and the local governments.
Many sunscreens also contain triethanolamine, a compound that can cause the formation of cancer causing nitrosamines in products by combining with nitrite used as preservative and often not disclosed on sunscreen labels.
In March 1998, Dr. John Knowland of the University of Oxford reported studies showing that certain sunscreens containing PABA and its derivatives can damage DNA, at least in the test tube experiments. When a chemical sunscreen, Padimate-O, was added to DNA and the mixture exposed to the ultraviolet rays of sunlight, it was found that the sunscreen broke down in sunlight, releasing highly active agents that could damage DNA. It did not block out the UV, but instead absorbed energy. “It became excited and set off a chemical reaction that resulted in the generation of the dangerous free radicals and broken DNA strands that can lead to cancer,” he said and further commented that while it's too early to make blanket recommendations, “I would not use a product containing PABA, Padimate-O or other PABA derivatives.” Dr. Martin Rieger reported that PABA may play a role in DNA-dimer formation, a type of DNA damage that can induce carcinogenic changes.
The bottom line to help stay healthy is to know what you are putting on your skin. Skin absorbes anything you put on it and carries that into the blood stream. Do your research before putting anything on you that you may regret later.
