Re: Sunlight and cancer - turnabout?
This brings up another subject of the pushing of sunscreens as to block the perhaps benefit's of Vitamin D. With the fear of the effects of skin cancer. But as other post have brought to light that the lighter the skinned people are, and the position to where one lives and genetics's are also contributing factors in the production to skin cancer.
There always the hysteria by skin care product's that to much sun will age skin and cause melanoma. This may be true for some but the pharmaceutical companies seem to blanket the idea that everyone is susceptible to the issue. As a means to promote the products of sunscreens.
But not all sunscreens are safe and pose risk that can be worse for the body then the cause and promote health issues because as to the chemicals in them. Article taken from:
http://wwww.skinbiology.com/toxicsunscreenshtml
Free Radical Generators and Gender-Bending Estrogenic Chemicals
Sunscreen Chemicals may Generate Free Radicals Within Your Body
Do Chemical Sunscreens Increase Cancer?
Psoriasis Treatment Increases Skin Cancer 83-fold
Toxic Estrogenic Chemical Sunscreens
Orcas of Pacific Northwest Dying from Estrogenic Toxins
The Failure of Academic Dermatologists to Protect the Public
Sunscreen Options
Chemical Sunscreens Include:
Benzophenones (dixoybenzone, oxybenzone)
PABA and PABA esters (ethyl dihydroxy propyl PAB, glyceryl PABA, p-aminobenzoic acid, padimate-O or octyl dimethyl PABA)
Cinnamates (cinoxate, ethylhexyl p-methoxycinnamate, octocrylene, octyl methoxycinnamate)
Salicylates (ethylhexyl salicylate, homosalate, octyl salicylate)
Digalloyl trioleate
Menthyl anthranilate
Avobenzone [butyl-methyoxydibenzoylmethane; Parsol 1789] - This is the only chemical sunscreen currently allowed by the European Community. However, its safety is still questionable since it easily penetrates the skin and is a strong free radical generator.
Sunscreen Chemicals May Generate Free Radicals Within Your Body
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.
Avobenzone (Parsol 1789) May Not Be Safe Either
In 1997, Europe, Canada, and Australia changed sunscreens to use three specific active sunscreen ingredients - avobenzone (also known as Parsol 1789), titanium dioxide, and zinc oxide - as the basis of sunscreens. In the USA, the cosmetic companies have held off this policy as they try to sell off their stockpiles of cosmetics containing toxic sunscreens banned in other countries.
However, avobenzone is a powerful free radical generator and also should have been banned. Avobenzone is easily absorbed through the epidermis and is still a chemical that absorbs ultraviolet radiation energy. Since it cannot destroy this energy, it has to convert the light energy into chemical energy, which is normally released as free radicals. While it blocks long-wave UVA, it does not effectively UVB or short-wave UVA radiation, and is usually combined with other sunscreen chemicals to produce a "broad-spectrum" product. In sunlight, avobenzone degrades and becomes ineffective within about 1 hour.
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Do Chemical Sunscreens Increase Cancer?
Worldwide, the greatest rise in melanoma has been experienced in countries where chemical sunscreens have been heavily promoted The rise in melanoma has been exceptionally high in Queensland, Australia where the medical establishment has vigorously promoted the use of sunscreens. Queensland now has more incidences of melanoma per capita than any other place on Earth. (Garland, Cedric F., et al. Could sunscreens increase melanoma risk? American Journal of Public Health, Vol. 82, No. 4, April 1992, pp. 614-15).
Dr. Gordon Ainsleigh in California believes that the use of sunscreens causes more cancer deaths than it prevents. He estimates that the 17% increase in breast cancer observed between 1981 and 1992 may be the result of the pervasive use of sunscreens over the past decade (Ainsleigh, H. Gordon. Beneficial effects of sun exposure on cancer mortality. Preventive Medicine, Vol. 22, February 1993, pp. 132-40). Recent studies have also shown a higher rate of melanoma among men who regularly use sunscreens and a higher rate of basal cell carcinoma among women using sunscreens (Garland, Cedric F. et al. Effect of sunscreens on UV radiation-induced enhancement of melanoma growth in mice. Journal of the National Cancer Institute, Vol. 86, No. 10, May 18, 1994, pp. 798-801 :Larsen, H.R. "Sunscreens: do they cause skin cancer." International Journal of Alternative & Complementary Medicine, 1994; 12(12): 17-19; Farmer K.C. & Naylor, M.F. "Sun exposure, sunscreens, and skin cancer prevention: a year-round concern." Ann Pharmacother, 1996; 30(6):662-73)
Drs. Cedric and Frank Garland of the University of California have pointed out that while sunscreens do protect against sunburn, there is no scientific proof that they protect against melanoma or basal cell carcinoma in humans (Garland, C.F., et al. "Could sunscreens increase melanoma risk?" American Journal of Public Health, 1992; 82(4): 614-615.) The Garlands believe that the increased use of chemical sunscreens is the primary cause of the skin cancer epidemic. There is, however, some evidence that regular use of sunscreens helps prevent the formation of actinic keratoses, the precursors of squamous cell carcinoma (Dover, Jeffrey S. & Arndt, Kenneth A. Dermatology. Journal of the American Medical Association, Vol. 271, No. 21, June 1, 1994, pp. 1662-63).
In February 1998, epidemiologist Marianne Berwick of Memorial Sloan-Kettering Cancer Center in New York presented a careful analysis of data on sunscreen use and skin cancer at the annual meeting of the American Association for the Advancement of Science. Sunscreens may not protect against skin cancer, including melanoma, she concluded. "We don't really know whether sunscreens prevent skin cancer," said Berwick. She looked first at four studies of squamous cell cancer, a cancer that appears on the head, neck, and arms but is usually not lethal. Two of the studies concluded that sunscreen protected against a skin condition thought to precede squamous cell cancer while two other studies reported that sunscreen did not shield people from this type of skin cancer. She then analyzed two studies of basal cell carcinoma, another nonlethal skin cancer that is the most common form of skin cancer and appears most frequently on the head, neck, and arms. Those two studies found that people who used sunscreen were more likely to develop basal cell cancer than people who did not. She then analyzed 10 studies of melanoma, the skin cancer is the most deadly. Melanoma often starts in or near moles on the skin. In five of the melanoma studies, people who used sunscreen were more likely than nonusers to develop melanoma. In three of the studies, there was no association between sunscreen use and melanoma. In the final two studies, people who used sunscreen seemed to be protected. (Source: Science News, Vol. 153, No. 23, June 6, 1998, p. 360).
"After examining the available epidemiological data and conducting our own large case-control population-based study, we have found no relationship between sunscreen use at any age and the development of melanoma skin cancer," said Dr. Berwick. Although sunscreens do prevent sunburn, Dr. Berwick concluded that sunburn itself is not the direct cause of cancer. Dr. Berwick objected to the universal blanket advice about using sunscreens during all time spent outdoors.
Dr. Berwick previously conducted a 1996 study that found no link between sunscreen use at any age and the development of melanoma. The same study also found no relationship between a history of sunburn and the development of melanoma. Berwick continued saying that the relationship between sunscreen use and the development of skin cancer is complicated by evidence that people who are sensitive to the sun engage in fewer activities in the bright sun and wear sunscreen when they do. But if these people develop melanoma, it may be because they are genetically susceptible and likely to develop skin cancer regardless of the amount of sunlight exposure or protection from sunscreen.
"Based on the evidence, we conclude that sunburn itself probably does not cause melanoma, but that it is an important sign of excessive sun exposure particularly among those who are genetically susceptible because of their skin-type," said Dr. Berwick. The melanoma risk for people with numerous moles was six times higher than that of someone with only a few moles. Persons most at risk for melanoma are those with red or blond hair and lighter colored eyes. Such light-skinned people have almost six times more melanoma than persons with darker skin. "The evidence indicates that chronic sun exposure may be protective for the development of melanoma because the skin has adapted to the sun, having become thicker as it has tanned. On the other hand, intermittent sun exposure appears to increase risk, making it much less protective," added Dr. Berwick. "People need to focus on their individual risk characteristics, such as their pigmentary phenotype, their family history, and the type and number of moles they have. I recommend that people avoid the sun when they are clearly at high risk and that they should enjoy a reasonable amount of outdoor activities with less anxiety when they are clearly at reduced risk," advised Dr. Berwick.
After Dr. Berwick's presentation of this data, the American Academy of Dermatology (ADA) issued a press release attacking her work. The then president of the ADA insulted her as a "number crunching scientist". But then, all scientists spend a lot of time crunching numbers.
Studies have found that the incidence of skin cancers has increased even as sunscreens have become popular among fair-skinned people. The establishment answer to this increase in the cancer rate is that wearing sunscreen makes people stay in the sun too long. A study by Drs. Mike Brown (Kate Law of the Cancer Research Campaign) Philippe Autier (European Institute of Oncology in Milan) reported that children using sunscreen returned from holiday with more skin moles - a possible sign of increased cancer risk. Some say that people who wore higher factor sunscreens tend to stay out in sunlight much longer, because they fell protected. However, others have pointed out that if sunscreen chemicals were protective, the factors of longer sun exposure would be somewhat countered by the sunscreen's supposed protective actions.
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Skin Cancer Increase Not Due to Ozone Depletion
But what about ozone depletion and skin cancer? Could this be the cause of the increased skin cancer rates? Professor Johan Moan of the Norwegian Cancer Institute found that the yearly incidence of melanoma in Norway had increased by 350% for men and by 440% for women during the period 1957 to 1984. He also determined that there had been no change in the ozone layer over this period of time. He concludes his report in the British Journal of Cancer by stating "Ozone depletion is not the cause of the increase in skin cancers" (Moan, J. & Dahlback, A. The relationship between skin cancers, solar radiation and ozone depletion. British Journal of Cancer, Vol. 65, No. 6, June 1992, pp. 916-21).
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Psoriasis Treatment Increases Skin Cancer 83-fold
Researchers at the Harvard Medical School discovered that psoralen, another ultraviolet light-activated, free radical generator that is chemically similar to sunscreens, is an extremely efficient carcinogen. They found that the rate of squamous cell carcinoma among patients with psoriasis, who had been repeatedly treated with UVA light after a topical application of psoralen, was 83 times higher than among the general population (Stern, Robert S. and Laid, Nan. The carcinogenic risk of treatments for severe psoriasis. Cancer, Vol. 73, No. 11, June 1, 1994, pp. 2759-64).
