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:
|
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
Related Articles, Books, LinkOut
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
Related Articles, Books, LinkOut
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
Related Articles, Books, LinkOut
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
Related Articles, Books, LinkOut
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
Related Articles, Books, LinkOut
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
Related Articles, Books, LinkOut
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
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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.
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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.
for safe sun
cream try Neways products
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