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Shelley R. Kramer                                  Contact: 310 457-5176                      Info@Healthy-Communications.com

Director of the Cancer Prevention Coalition for Los Angeles

         

 

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Sunscreens: Do They Cause Skin Cancer?

Most chemical sunscreens contain from 2 to 5% of benzophenone or its derivatives (oxybenzone, benzophenone-3) as their active ingredient. Benzophenone is one of the most powerful free radical generators known to man. It is used in industrial processes to initiate chemical reactions and promote cross-linking(15). Benzophenone is activated by ultraviolet light. The absorbed energy breaks benzophenone's double bond to produce two free radical sites. The free radicals desperately look for a hydrogen atom to make them "feel whole again"(15). They may find this hydrogen atom among the other ingredients of the sunscreen, but it is conceivable that they could also find it on the surface of the skin and thereby initiate a chain reaction which could ultimately lead to melanoma and other skin cancers. Researchers at the Harvard Medical School have recently discovered that psoralen, another ultraviolet light-activated free radical generator, 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(16).

With complete references for researchers

by Hans R. Larsen, MSc ChE

A comprehensive review of the evidence linking the use of chemicals in sunscreens to an increased risk of melanoma and skin cancer (basal carcinoma and squamous cell carcinoma) – with extensive references.

In 1991 Professor Johan Moan of the Norwegian Cancer Institute made an astounding discovery. He 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"(1).

SKIN CANCER

There are three major forms of skin cancer.

BASAL CELL CARCINOMA is the most common form of skin cancer. It occurs most frequently in men who spend a great deal of time outdoors and primarily produces lesions on the head and neck(2). Basal cell carcinoma rarely spreads throughout the body but can invade neighbouring bone and nerves(3).

SQUAMOUS CELL CARCINOMA is the second most common skin cancer. It primarily affects people who sunburn easily, tan poorly, and have blue eyes and red or blonde hair. Squamous cell carcinoma most commonly develops from actinic keratoses and can metastasize if left untreated. Squamous cell carcinoma of the lip is 12 times more common among men than among women(4).

MALIGNANT MELANOMA is the rarest form of skin cancer but is the most deadly. It affects the cells which produce melanin and seems to be more prevalent among city-dwellers than among people who work out-of-doors. It does not necessarily occur on sun-exposed areas of the body and is thought to be linked to brief, intense periods of sun exposure and a history of severe sunburn in childhood or adolescence. Malignant melanoma metastasizes easily and is often fatal if not caught in time(2,5).

The skin cancer epidemic is a worldwide phenomenon. In 1978 there were approximately 480,000 cases of non-melanoma skin cancer in the United States alone. This is expected to rise to over one million in 1994(6). Malignant melanoma is growing at a rate of 7% per year in the United States. In 1991 cancer experts estimated that there would be about 32,000 cases during the year of which 6,500 would be fatal(7). In Canada melanoma incidence rose by 6% per year for men and by 4.6% per year for women during the period 1970-1986(8). Australia has the highest melanoma rate in the world. For men the rate doubled between 1980 and 1987 and for women it increased by more than 50%(9). It is now estimated that by age 75 two out of three Australians will have been treated for some form of skin cancer(10).

If the ozone layer has not yet changed significantly except at the poles, then what is causing the enormous increase in skin cancer?

The sunscreen connection
The Australian experience provides the first clue. The rise in melanoma has been exceptionally high in Queensland where the medical establishment has long and vigorously promoted the use of sunscreens. Queensland now has more incidences of melanoma per capita than any other place. Worldwide, the greatest rise in melanoma has been experienced in countries where chemical sunscreens have been heavily promoted(11).

Drs. Cedric and Frank Garland of the University of California are the foremost opponents of the use of chemical sunscreens. They point out that, although sunscreens do protect against sunburn, there is no scientific proof that they protect against melanoma or basal cell carcinoma in humans(11). There is, however, some evidence that regular use of sunscreens helps prevent the formation of actinic keratoses, the precursors of squamous cell carcinoma(12).

The Garland brothers strongly believe that the increased use of chemical sunscreens is the primary cause of the skin cancer epidemic. They emphasize that people using sunscreen tend to stay longer in the sun because they do not get a sunburn - they develop a false sense of security(7). Chemical sunscreens are formulated to absorb UVB radiation, they let most of the UVA rays through(7). UVA rays penetrate deeper into the skin and are strongly absorbed by the melanocytes which are involved both in melanin production (sun tanning) and in melanoma formation(11). UVA rays also have a depressing effect on the immune system(13).

ULTRAVIOLET RADIATION

UVA rays constitute 90-95% of the ultraviolet light reaching the earth. They have a relatively long wavelength (320-400 nm) and are not absorbed by the ozone layer. UVA light penetrates the furthest into the skin and is involved in the initial stages of suntanning. UVA tends to suppress the immune function and is implicated in premature aging of the skin(2,13,14).

UVB rays are partially absorbed by the ozone layer and have a medium wavelength (290-320 nm). They do not penetrate the skin as far as the UVA rays do and are the primary cause of sunburn. They are also responsible for most of the tissue damage which results in wrinkles and aging of the skin and are implicated in cataract formation(2).

UVC rays have the shortest wavelength (below 290 nm) and are almost totally absorbed by the ozone layer. As the ozone layer thins UVC rays may begin to contribute to sunburning and premature aging of the skin(2).

All forms of ultraviolet radiation are believed to contribute to the development of skin cancer(2).

Most chemical sunscreens contain from 2 to 5% of benzophenone or its derivatives (oxybenzone, benzophenone-3) as their active ingredient. Benzophenone is one of the most powerful free radical generators known to man. It is used in industrial processes to initiate chemical reactions and promote cross-linking(15). Benzophenone is activated by ultraviolet light. The absorbed energy breaks benzophenone's double bond to produce two free radical sites. The free radicals desperately look for a hydrogen atom to make them "feel whole again"(15). They may find this hydrogen atom among the other ingredients of the sunscreen, but it is conceivable that they could also find it on the surface of the skin and thereby initiate a chain reaction which could ultimately lead to melanoma and other skin cancers. Researchers at the Harvard Medical School have recently discovered that psoralen, another ultraviolet light-activated free radical generator, 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(16).

The benefits of sunlight
Some scientists believe that UV light causes skin cancer through the combined effect of suppression of the immune system and damage to DNA(10,17). Exposure to UV light is, however, not all bad. Most of the body's vitamin D supply, about 75% of it, is generated by the skin's exposure to UVB rays(18). Using a sunscreen drastically lowers the cutaneous production of vitamin D3(19). A low blood level of vitamin D is known to increase the risk for the development of breast and colon cancer and may also accelerate the growth of melanoma(18,19,20).

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 1991 and 1992 may be the result of the pervasive use of sunscreens over the past decade(20). 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(11,21).

Dr. Ainsleigh estimates that 30,000 cancer deaths in the United States alone could be prevented each year if people would adopt a regimen of regular, moderate sun exposure(20).

Although the medical establishment still strongly supports the use of sunscreens there is a growing consensus among progressive researchers that the use of sunscreens does not prevent skin cancer and, as a matter of fact, may promote skin cancers as well as colon and breast cancer.

The bottom line
So what should you do to protect yourself as much as possible against these cancers? Summarizing current research the following recommendations appear reasonable:

  • DO NOT rely on the use of sunscreens to protect you against skin cancer.
  • DO NOT try to get a tan by visiting a tanning studio. The rays from their UV lamps are extremely harmful and the tan produced does not have the protective effect of a sunlight-induced tan(2,7).
  • DO try to develop a moderate natural suntan unless you have extremely sensitive skin and burn easily. Regular and moderate unprotected sun exposure in the early morning or late afternoon will help maintain a protective tan and keep your vitamin D stores at an optimum level(20).
  • DO wear protective clothing and a wide-brimmed hat when you are outside. Avoid sun exposure between 10 AM and 3 PM if at all possible. Remember that UV rays, particularly UVA, are present even on cloudy days(7).
  • DO wear sunglasses that filter out 100% of the ultraviolet light to protect yourself against the development of cataracts(7).
  • DO remember that sunlight is strongly reflected from sand, snow, ice, and concrete and can increase your direct sunlight exposure by 10 to 50%(2).
  • DO make sure you get enough vitamin D3 and beta-carotene, if necessary through supplementation. Recent research has shown that taking 30 mg of beta-carotene a day protects against the suppression of the immune system by UVA rays(13).
  • DO make sure to supplement your diet with antioxidants. Dr. Abram Hoffer in Victoria, Canada recommends that vitamin C, vitamin E, and selenium be used as a protection against the damages of excessive ultraviolet radiation. He suggests daily dosages of 3 grams or more of vitamin C, 800 IU of vitamin E, and 200 micrograms of selenium (l-selenomethionine)(22). Vitamins C and E also protect against cataract formation(23,24).
  • DO cut down on the fat in your diet. Recent research has shown that patients with non- melanoma skin cancers can reduce their risk of developing additional actinic keratoses (precursors to skin cancer) by switching to a low fat diet(25).

SUNSCREENS

Sunscreens are designed to protect against sunburn (UVB rays) and generally provide little protection against UVA rays. They come in two forms:

CHEMICAL SUNSCREENS contain chemicals such as benzophenone or oxybenzone (benzophenone-3) as the active ingredient. They prevent sunburn by absorbing the ultraviolet (UVB) rays(2).

PHYSICAL SUNSCREENS contain inert minerals such as titanium dioxide, zinc oxide, or talc and work by reflecting the ultraviolet (UVA and UVB) rays away from the skin(2).

A sunscreen with a SPF of 15 filters out approximately 94% of the UVB rays. One with a SPF of 30 filters out 97%. The SPF applies for UVB rays only. The protection provided against UVA rays in chemical sunscreens is about 10% of the UVB rating(26).

 

  • DO wear a physical sunscreen with a SPF of 30 if you absolutely must be out in the sun for extended periods of time(22). Physical sunscreens containing , zinc oxide, or corn starch work by reflecting the UV radiation rather than by absorbing it. Sunscreens are tested by using artificial UV light and a screen with a SPF of 30 is not twice as effective as one with a factor of 15(17). Also, reapplying sunscreen during the day does not extend the period of protection. Even "broad-spectrum" sunscreens are not very good in filtering out UVA rays(26). A natural suntan is probably more effective.

    Read the labels on your products and avoid benzophene, diethanolamine (DEA), triethanolamine (TEA), propylene glycol (PG), polyethyleneglycol (PEG), dea, sodium lauryl sulfate (SLS), mineral oil, petrolatum, lanolin

    .

  • DO see your healthcare provider if you spot any unusual moles or growth on your skin - particularly if they are irregular in shape, bleed, itch, or appear to be changing. Most skin cancers can be cured if caught in time(27).

The saga of sunscreens and skin cancer is far from over. Research is continuing and new findings are being published at an accelerated pace. But until we know the whole story, it would seem prudent to take precautions based on what we do know.

Neways International has been a  company manufacturing safe, effective, alternative products that really work for over 15 years..

*****

Information about Sunscreens:

Most chemical sunscreens contain from 2 to 5% of benzophenone or its derivatives (oxybenzone, benzophenone-3) as their active ingredient. Benzophenone is one of the most powerful free radical generators known to man. It is used in industrial processes to initiate chemical reactions and promote cross-linking(15). Benzophenone is activated by ultraviolet light. The absorbed energy breaks benzophenone's double bond to produce two free radical sites. The free radicals desperately look for a hydrogen atom to make them "feel whole again"(15). They may find this hydrogen atom among the other ingredients of the sunscreen, but it is conceivable that they could also find it on the surface of the skin and thereby initiate a chain reaction which could ultimately lead to melanoma and other skin cancers. Researchers at the Harvard Medical School have recently discovered that psoralen, another ultraviolet light-activated free radical generator, 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.

 Dr. Mercola:Should You Use a Sunscreen to Guard Against SUNBURN?

Absolutely! But not any kind of commercial sunscreen. More on that in a moment — but first, let me just say…

As much as I prefer you steer clear of sunscreens because they interfere with natural vitamin D production, there is one critical exception.

The exception is when it is impossible to limit full body exposure to sunlight! So if you can’t limit your exposure for whatever reason, do use a safe sunscreen to protect your skin from sunburn. It is for YOUR own good.

You see, many studies have shown that excess sun exposure that causes sunburn is a well-proven risk factor for melanoma (a very dangerous type of skin cancer.)

More importantly, your risk of getting melanoma increases in relationship to sunburn frequency and severity. Limiting sun exposure, wearing protective clothing, and using a 100% all-natural, non-chemical sunscreen lotion may reduce the risks of skin cancer and other harmful effects of the sun.

Other studies revealed that people who spend more time outdoors without getting sunburn, actually decrease their risk of developing melanoma.

Now get this:

Safe sunlight exposure has also been shown to protect against as many as sixteen different types of cancer, including breast, colon, endometrial, esophageal, ovarian, bladder, gallbladder, gastric, pancreatic, prostate, rectal, and renal cancers, as well as non-Hodgkin’s lymphoma.

So, yes, your body needs a bit of unprotected sun exposure. For all the benefits I’ve mentioned earlier. But if you can’t avoid the following three scenarios:

  • You’re forced to be in the direct rays of the sun for a longer time than is safe…

  • You must go into intense sunlight without having the opportunity to gradually build up to it…

  • You’re in a situation where blocking the sun with strategic clothing or sunshades is impractical…

…use a sunscreen to help guard against sunburn. But, don’t just slap on any of the standard commercial brands you find on store shelves. With that in mind…

It’s Time to Expose the Sunscreen Smokescreen!

In my opinion, corporate greed has created products that are harmful.

I’m talking hundreds of sunscreens that I believe are toxic to your skin because they contain man-made chemicals ... chemicals I believe can cause serious health problems and increase your risk of disease. Here’s why.

The main chemical used in sunscreens to filter out ultraviolet B light is octyl methoxycinnamate. OMC for short. OMC was found to kill mouse cells even at low doses.  Plus, it was also shown to be particularly toxic when exposed to sunshine. And guess what?

OMC is present in 90 percent of sunscreen brands!

But that’s not the half of it. A common ultraviolet A filter, butyl methoxydibenzoylmethane, has also demonstrated toxic properties.

Furthermore, several studies show that the chemicals commonly used in sunscreens are absorbed through the skin and end up circulating in your blood stream. Not good. So…

If Your Sunscreen Contains Any of These Chemicals That I Consider Dangerous and Potentially Life Threatening, Do Yourself a BIG Favor…

Dump it in the trash now .

Yes, that’s right. Toss your sunscreen in the trash if it contains any of these questionable chemicals:

Sunscreen
Toss your sunscreen in the trash if it contains any of these chemicals I consider to be potentially harmful.

  • Para amino benzoic acid…

  • Octyl salicyclate…

  • Avobenzone…

  • Oxybenzone…

  • Cinoxate…

  • Padimate O…

  • Dioxybenzone…

  • Phenylbenzimidazole…

  • Homosalate…

  • Sulisobenzone…

  • Menthyl anthranilate…

  • Trolamine salicyclate…

  • Octocrylene…

And, oh yes, let me not forget…

Potentially harmful chemicals such as dioxybenzone and oxybenzone (two chemicals I just mentioned) are some of the most powerful free radical generators known to man!

So if your sunscreen contains dioxybenzone, oxybenzone, or any of the other chemicals I just revealed, I highly recommend you switch to a formula that is safe and healthy for your skin.

And a note to moms … You are undoubtedly very conscientious about caring for your children.  But when you lather up your son or daughter with sunscreen thinking you’re doing the right thing, you could in fact be doing more harm than good.

So check the labels on your sunscreen, and throw them out if they contain any of the potentially dangerous chemicals named above.  After all, your skin is your largest organ, as your child’s skin is theirs.

Fortunately, there’s a much better option than chemical-laden commercial sunscreens…

 FYI: Neways Sunbrero Sunblock does not contain any of the above chemicals Find out more.

More Studies on Sunscreens

 Studies of Sunscreen Ingredients, 1997

Regarding the explosion of the sun and excess radiation, yesterday my
daughter got a sunburn after I applied her normal amount of sunscreen
that usually protects her. And it was foggy here most of the day. I
wondered if there was excess radiation by the sun.

I'm continuing to look for information on sunscreen ingredients. If
anyone has more information, please e-mail me. I'm writing an article
on this for the next issue of Healthy Child. The following are some of
the studies I found:

Lancet 1997 Sep 20;350(9081):863-4
Systemic absorption of sunscreen after topical application.
Hayden CG, Roberts MS, Benson HA

Some excerpts from this study:

"It is often assumed that little or none of a topically applied
substance is absorbed into the systemic circulation. We show that
substantial amounts of an applied sunscreen, oxybenzone, are absorbed
and subsequently excreted in human urine. Oxybenzone has low acute
toxicity in animal studies yet little is know about its chronic
toxicity and disposition after topical application in people.
Oxybenzone is a benzophenone derivative commonly used throughout the
world to make sun-products with especially high sun protection factors
(SPF)."


"Our results suggest that sunscreens should not be the sole method of
sun protection. It would be prudent not to apply oxybenzone to large
surface areas of skin for extended and repeated periods of time,
unless no alternative protection is available. There may be an
additional concern for young children who have less well-developed
processes of elimination, and have a larger surface area per body
weight than adults, with respect to systemic availability of a
topically applied dose."

Other studies of interest:

British Journal of Clinical Pharmacology 48 (4), 635-637
© Blackwell Science Ltd

Absorption of sunscreens across
human skin: an evaluation of
commercial products for children and
adults
R. Jiang2, M. S. Roberts3, D. M. Collins2 and
H. A. E. Benson1

Aims Topical sunscreens are routinely applied to the skin by a
large percentage of the population. This study assessed the extent
of absorption of a number of common chemical sunscreen agents
into and through human skin following application of commercially
available products.

Methods Sunscreen products were applied to excised human
epidermis in Franz diffusion cells with the amount penetrating into
and across the epidermis assessed by h.p.l.c. for 8 h following
application.

Results All sunscreen agents investigated penetrated into the skin
(0.25 g m-2 or 14% of applied dose), but only benzophenone-3
passed through the skin in significant amounts (0.08 g m-2 or 10%
of the applied dose). With one exception, suncreen agents in
corresponding products marketed for adults and children had
similar skin penetration profiles.

Conclusions Whilst limited absorption across the skin was
observed for the majority of the sunscreens tested,
benzophenone-3 demonstrated sufficiently high penetration to
warrant further investigation of its continued application.

4: Australas J Dermatol 1999 Feb;40(1):51-3

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The PABA story.

Mackie BS, Mackie LE Prince Henry Hospital, Sydney, Australia.

The qualities of para-aminobenzoic acid (PABA)
are discussed and an account is given of how it
came to be the favorite sunscreen of the post
World War II era. Slowly, however,
dermatologists became aware that it was a
fairly common sensitizer and that it tended to
cross-sensitize with compounds of similar
chemical structure both in contact with the skin and
given as systemic drugs. Furthermore, continued
exposure to chemicals of this type could lead to
autoimmune responses especially systemic lupus
erythematosus and dermatomyositis. Discussion
of these complications from the use of PABA
took place at two meetings of the Dermatological
Association of Australia in 1964 and 1965, and
played a part in the slow withdrawal of PABA
from sunscreens.

Publication Types: Historical article

PMID: 10098293, UI: 99198366 29: FEBS Lett 1997 Nov 24;418(1-2):87-90

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Chemical oxidation and DNA damage catalyzed by
inorganic sunscreen ingredients.


Dunford R, Salinaro A, Cai L, Serpone N,
Horikoshi S, Hidaka H, Knowland J

University of Oxford, Department of
Biochemistry, UK.

This is now a known carcinogen Titanium dioxide (TiO2) has been noted (US
Federal Register, 43FR38206, 25 August 1978) to
be an unsafe physical sunscreen because it
reflects and scatters UVB and UVA in sunlight.
However, TiO2 absorbs about 70% of incident UV,
and in aqueous environments this leads to
the generation of hydroxyl radicals which can
initiate oxidations. Using chemical methods, we
show that all sunscreen TiO2 samples tested
catalyze the photo-oxidation of a representative
organic substrate (phenol). We also show that
sunlight-illuminated TiO2 catalyses DNA damage
both in vitro and in human cells. These results
may be relevant to the overall effects of sunscreens.

PMID: 9414101, UI: 98074912

45: Toxicol Lett 1995 Oct;80(1-3):61-7

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Safety evaluation of benzophenone-3 after
dermal administration in rats.


Okereke CS, Barat SA, Abdel-Rahman MS

Department of Pharmacology and Toxicology,
University of Medicine and Dentistry of New
Jersey, New Jersey Medical School, Newark
07103-2714, USA.

Benzophenone-3 (BZ-3) is a category 1
(over-the-counter) product approved by the US Food
and Drug Administration (FDA) for use as a
sunscreen agent in medicine, cosmetics, industry,
and agriculture. This is due to its ability to
absorb and dissipate ultraviolet light in a harmless
manner, thus protecting human skin and products
from UV irradiation. This study investigated the
safety of BZ-3 after repeated administration.
BZ-3 in ointment base was applied at a dose of 100
mg/kg body wt. twice daily, for 4 weeks to the
skin of male Sprague-Dawley rats. Body weight,
organ to body weight ratios, hematological, and
clinical chemistry parameters were not effected.
Pathological examination revealed no
significant changes between control and treated animals.
No gross external abnormalities were observed.
Both in vivo and in vitro blood glutathione
(GSH) levels were effected by BZ-3 treatment.
However, after 60 min of incubation, a reversal
of this effect was observed in the treatment
group as blood GSH levels approached normal
levels. Furthermore, investigation of
GSH-reductase and peroxidase with time indicated an
increase in GSH-reductase activity at 60 and 90
min with no effect on GSH-peroxidase.
Pre-treatment with phenobarbital modulated the
metabolic disposition of BZ-3. There was an
increase in the formation of the hydroxy
metabolites but not the O-dealkylated form. This study
suggests that BZ-3 is not toxic to rats when
applied dermally at a dose of 100 mg/kg body wt.
for 4 weeks.

PMID: 7482593, UI: 96062138 65: FEBS Lett 1993 Jun 21;324(3):309-13

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Sunlight-induced mutagenicity of a common
sunscreen ingredient.

Knowland J, McKenzie EA, McHugh PJ, Cridland NA

Department of Biochemistry, South Parks Road,
Oxford OX1 3QU, UK.

We have tested the mutagenicity of a UV-B
sunscreen ingredient called Padimate-O or octyl
dimethyl PABA, which, chemically speaking, is
identical to an industrial chemical that generates
free radicals when illuminated. It is harmless
in the dark but mutagenic in sunlight, attacking DNA
directly. A commercial sunscreen containing
Padimate-O behaves in the same way. UV-A in
sunlight also excites Padimate-O, although less
than UV-B. Some related compounds, including a
known carcinogen, behave similarly. As mutagens
may be carcinogenic, our results suggest that
some sunscreens could, while preventing
sunburn, contribute to sunlight-related cancers.

Comments:
Comment in: FEBS Lett 1993 Dec
20;336(1):184-5; discussion 186

PMID: 8405372, UI: 94009604 64: J Toxicol Environ Health 1997 Aug 8;51(5):447-62

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Effect of environmental conditions on the
penetration of benzene through
human skin.


Nakai JS, Chu I, Li-Muller A, Aucoin R

Health Canada, Bureau of Chemical Hazards,
Environmental Health Centre, Ottawa, Ontario,
Canada.

The in vitro penetration of [14C]benzene
through freshly prepared human skin was examined
under a variety of skin conditions associated
with swimming and bathing. The experimental
system utilized a recirculating donor solution
and a flow-through receiver solution, and was
modified to accommodate the analysis of
volatiles. The permeability coefficient of 0.14 cm/h
under standard conditions at 26 degrees C was
found to increase to 0.26 cm/h at 50 degrees C
and decrease to 0.10 cm/h at 15 degrees C.
Storage of the skin at- 20 degrees C did not affect
the penetration of benzene. Application of baby
oil, moisturizer, or insect repellant to the skin
before exposure under standard conditions did
not affect the flux of benzene, but a significant
increase was observed when the skin was
pretreated with sunscreen (permeability coefficient
0.24 cm/h). These results suggest that risk
assessment or exposure modeling for benzene and
other environmental contaminants should account
for appropriate changes in the environmental
conditions when considering the dermal route of
exposure.

PMID: 9233379, UI: 97377744

24: Mutat Res 1998 May 11;414(1-3):15-20

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Induction of sister chromatid exchanges and
micronuclei by titanium
dioxide in Chinese hamster ovary-K1 cells.


Lu PJ, Ho IC, Lee TC

Institute of Biomedical Sciences, Academia
Sinica, Taipei 115, Taiwan.

Titanium dioxide (TiO2) has color properties of
extreme whiteness and brightness, is relatively
inexpensive, and is extensively used as a white
pigment in a variety of materials. TiO2, an
effective blocker of ultraviolet light, is
frequently added to sunscreens and cosmetic creams.
However, the genotoxicity of TiO2 remains to be
controversial. In this report, we have
demonstrated that TiO2 can be transported into
Chinese hamster ovary-K1 (CHO-K1) cells.
The effects of TiO2 on induction of sister
chromatid exchanges (SCE) and micronuclei (MN)
were then studied in these cells. The SCE
frequency in CHO-K1 cells treated with TiO2 at a
nonlethal dose range (0 to 5 microM) for 24 h
was significantly and dose-dependently increased.
By the conventional MN assay, TiO2 at the dose
ranged from 0 to 20 microM slightly increased
the MN frequency in CHO-K1 cells. However, in
the cytokinesis-block MN assay, the number
of MN per 1000 binucleated cells was
significantly and dose-dependently enhanced in CHO-K1
cells treated TiO2 at the same dose range for
24 h. These results suggest that TiO2 is a potential
genotoxic agent. Copyright 1998 Elsevier
Science B.V.

PMID: 9630482, UI: 98296327

Jane Sheppard
Future Generations
Publisher of Healthy Child Newsletter
http://www.healthychild.com
Vital, In-depth Information on Children's Health Issues

FYI: Neways Sunbrero Sunblock does not contain any of the above chemicals Find out more.

 


Sunscreen Use Not Tied to Malignant Melanoma

By David Douglas

NEW YORK (Reuters Health) Jul 01 - Contrary to some previous findings, users of topical sunscreens appear to be at no increased risk of developing malignant melanoma, Wisconsin-based researchers report in the July issue of the American Journal of Public Health.

"The issue of sunscreen's impact on melanoma risk has been debated for some time," lead researcher Dr. Michael Huncharek told Reuters Health. The current investigation, he pointed out, "was motivated to a large degree" by "a review of the existing literature by Sloan-Kettering epidemiologists...suggesting that sunscreen increased melanoma risk."

Dr. Huncharek and Bruce Kupelnick of Meta-Analysis Research Group in Stevens Point felt "a more rigorous methodological and statistical evaluation was necessary," and they thus conducted a meta-analysis using data from 11 case-control studies of sunscreen use and melanoma involving 9067 patients.

"We found," Dr. Huncharek continued, "that a number of study design issues contributed to the misinterpretation of the existing data by reviewers producing only 'narrative', non-quantitative reviews of the data. When one looks critically at the data it is clear that the source of patients for some of these studies significantly influenced study outcome."

In particular, data from studies derived using patients from hospitals were statistically heterogenous. The results "differed substantially when compared to each other--far more than expected by chance alone." No such heterogeneity was found among the studies deriving their patients from population tumor registries.

"The bottom line," Dr. Huncharek observed, "is that the population-based studies show no evidence of statistical heterogeneity--meaning that this group of studies show consistent results across the studies and show no evidence of increased risk of melanoma with sunscreen use."

"Sunlight remains the most important risk for the development of melanoma, although the exact biological interaction of sunlight with other host factors such as skin tone, hair color, genetic background, remains obscure," he concluded. "There is no evidence that sunscreens increase the risk of developing melanoma, and our study actually provides indirect evidence that it is truly protective."

Am J Public Health 2002;92:1173-1177.

 


REFERENCES

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This article was also published in the International Journal of Alternative & Complementary Medicine, Vol 12, No 12, December 1994, pp.17-19.

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